3

Sustainability for the Chemical Economy

In the 21st century, society faces the urgent tasks of mitigating the global climate emergency and arresting the deterioration of global ecosystems. The Intergovernmental Panel on Climate Change’s Sixth Assessment Report warned that the world is on code red because major climate-related damages are already causing significant loss of lives and livelihoods (IPCC, 2021, 2022; see also IPBES, 2019). In the United States in the past decade alone, hurricanes and wildfires exacerbated by climate change are estimated to have cost $890 billion in damages (Smith, 2021). Other climate-driven risk modeling (Hsiang et al., 2017) estimates that 1.5°C of warming compared to a 1981–2010 baseline would cost the United States –0.1% to 1.7% of its gross domestic product (GDP), and 4°C of warming would cost 1.5% to 5.6% of its GDP, with losses concentrated in the poorer counties across the country. The deterioration of global ecosystems is resulting from a multiplicity of factors. Among them are waste streams derived from products that have served human needs. Plastic pollution is estimated to reduce the benefit humans derive from global oceans by

1% to 5%, amounting to an estimated annual loss of $0.5 to $2.5 trillion (Beaumont et al., 2019). Herbicides and pesticides, while contributing to increased agriculture production, also contribute to biodiversity losses and ecosystem degradation (Beketov et al., 2013; NRC, 2000; Schütte et al., 2017). Additionally, plastics production has a large energy cost that has already produced more than 100 million metric tons of carbon dioxide (CO₂) equivalent in greenhouse gas (GHG) emissions in the United States alone, and these GHG emissions are predicted to substantially increase based on the rate of plastic consumption (Nicholson et al., 2021).

These climate and ecological crises necessitate meeting human needs while making transformative changes in a society in which sustainable development is the central paradigm—that is, the alignment of economic development with public health and environmental protection. The United States affirmed its support for sustainable development as early as the 1992 Earth Summit. The United States then reiterated its support in helping to formulate and launch the Sustainable Development Goals (SDGs) of the United Nations in 2015 (UN, 2015). These goals aim to achieve economic progress, good health, clean water, affordable renewable energy, and other human needs and aspirations for everyone, while protecting ecosystems and maintaining a stable climate, which are vital to support the former.

To reach these goals, there is a need to balance the benefits from products that meet human needs with the costs of those products to public health, the environment, and the climate. This is both a challenge and an opportunity for the chemical economy. Basic chemistry and associated industries have made tremendous contributions toward meeting the SDGs, but have also created products and processes that contribute to the climate and ecological crises. To address these crises, the chemical economy will need to make a transformative shift in which sustainability and decarbonization are central tenets.

A report from the National Research Council on Sustainability in the Chemical Industry commented that “sustainability is a path forward that allows humanity to meet current environmental and human health, economic, and societal needs without compromising the progress and success of future generations” (NRC, 2006a). Decarbonization, defined as the reduction in use and emissions of fossil-based carbon (NASEM, 2021b), along with sustainability, is an essential feature of the transformation needed both for industry’s social license to operate and to meet pressures in the United States and abroad. Companies that lead on sustainability will be more competitive in a new economic environment that values sustainability and climate protection. Nevertheless, to transition from the business-as-usual scenario to this sustainable future, companies face a number of challenges. Market and public policies do not consistently and fully reward sustainability and climate protection, which is necessary to provide the certainty of payoffs for companies to invest in such a shift.

The growing embrace of sustainability by the public has spurred efforts in basic chemical research (as well as in commercial research and development [R&D]) to find solutions that can meet the SDGs using green chemistry and other principles, such as circular design. However, much work is still needed, and there are large gaps in achieving the world’s sustainability goals that chemistry is primed to solve. All areas within chemistry have a role to play in advancing fundamental research toward decarbonization, sustainability, and environmental stewardship. In this chapter, we discuss contributions that chemistry has already made to sustainability, decarbonization, and the environment; consider industry initiatives and public policies that can provide more certainty for the payoffs that companies need to drive the transformative shift; and then lay out some important research avenues for fundamental chemistry.

3.1 BASIC CHEMISTRY IN SOCIETY: CONTRIBUTIONS AND CONSEQUENCES

3.1.1 Contributions of Chemical Research to Society

Fundamental chemical research as well as applied R&D have contributed to sustainability, including saving lives, empowering individuals, and reducing emissions. We summarize in Table 3-1 examples given throughout this report of impactful developments arising because of basic chemical research, and list SDGs supported by each example. Several of these examples illustrate how products have brought benefits, and investments to advance basic chemistry can potentially improve the products and processes by reducing the amount of energy input and the amount of waste by-products. The committee’s focus, per its Statement of Task, is on the potential contributions of basic chemical research to these goals. We note that socioeconomic and political efforts, beyond technical approaches, are also necessary to meet these goals.

3.1.2 Adverse Consequences to Public Health, Ecosystems, and Climate from Chemical Products and Processes

Notwithstanding these numerous contributions to the SDGs, some of the same chemical products and processes adopted for their ability to meet specific needs have subsequently had significant public health and environmental impacts attributed to them. Debates continue on the use of these products: Should they be used in specific circumstances when benefits outweigh the costs; should they be severely restricted or banned to incentivize the search for more benign substitutes; and is a complete overhaul of the fundamental approach in that particular sphere needed or even possible

TABLE 3-1 Examples of Basic Chemical Research Contributions to the Sustainable Development Goals

(e.g., shifting from chemical-based agriculture to regenerative agriculture)? All of these are foundational questions needing further attention.

Examples include the perfluoroalkyl and polyfluoroalkyl substances (PFAS), highly fluorinated synthetic chemicals with unique properties due to their strong carbon-fluorine bonds. PFAS, which were invented in the 1930s and prized for their water- and oil-repellent properties, became widely used in firefighting products (e.g., at airports and military bases) and consumer products (e.g., nonstick pans, waterproof clothing, stain-resistant carpets). However, scientific research subsequently uncovered that PFAS¹ are biopersistent—they are environmentally mobile and do not decompose—and pose public health and environmental risks (U.S. Congress, 2019). Regulations and voluntary actions ended the manufacture of two PFAS chemicals, perfluorooctanoic acid and perfluorooctane sulfonate, in the 2000s (Hogue, 2019; NASEM, 2021d), but the United States today is still facing the challenge of redressing PFAS pollution in drinking water sources.

Another example is chlorpyrifos, one of the most widely used pesticides, applied to crops including corn, wheat, citrus, apples, and strawberries. In 2000, as more research revealed that chlorpyrifos posed neurodevelopmental risks to infants and children, environmental groups petitioned the U.S. Environmental Protection Agency (EPA) to end its use. Following the virtual removal of chlorpyrifos from homes and lawns in 2000, the chemical was banned from agricultural uses by 2007 (EPA, 2022). In 2015, the EPA under the Obama administration proposed to ban the use of the pesticide, but the decision was reversed under the subsequent administration. In 2021, in response to the Ninth Circuit Court of Appeals ruling that the EPA prove it was safe for use on food crops or to declare it illegal, the EPA announced its ban on the use of chlorpyrifos.

Although the calculation of cost versus benefit was clear in the chlorpyrifos example above, the calculation of chemistry-based products and processes even on the yardstick of public health is not always clear-cut and often is context dependent. The case of dichlorodiphenyltrichloroethane (DDT) is illustrative. The United States has banned the use of DDT for malaria control and has chosen to use alternatives for mosquito control. On the other hand, the World Health Organization (WHO) recommends the use of DDT for controlled indoor spraying as a strategy to control mosquitoes that are vectors for malaria and dengue. The WHO assessment favored DDT over alternative insecticides.

A recent study showed the extent of pharmaceutical pollution in Earth’s waterways (Wilkinson et al., 2022). While the pollution was extensive, and thought to be one of the drivers of antibiotic resistance seen today, it is notable that pharmaceuticals were found in all water systems, especially in wealthier countries. The paper additionally noted that the sites of highest contamination were “associated with areas with poor wastewater and waste management infrastructure and pharmaceutical manufacturing.” These discoveries were built on a body of knowledge around monitoring contamination of antibiotics and the risk of antibiotic resistance (Scott et al., 2016). On the basis of this knowledge, pharmaceutical companies are generally aware of this issue and have made strides to address pollution, but much work is still needed (EEB, 2018).

In these and other examples, the chemical innovations have addressed a pressing problem but subsequently were found to have produced negative unintended consequences. Such outcomes have been the result of incomplete foresight, and in some cases, they have been the result of incomplete transparency in public health and environmental impact evaluations of products before they enter the marketplace (McHenry, 2018). The PFAS incidents, alongside other contaminant and waste issues, underscore that industries within the chemical economy cannot simply take support from the public as a given, but will need to ensure that public good, public health, and protecting the environment are central to their mission (Mazzucato and Li, 2021).

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¹ The PFAS umbrella comprises more than 9,000 substances with different properties, potential toxicities, uses, and potential for human exposure.

3.2 TRANSITIONING TO SUSTAINABILITY AND DECARBONIZATION IN THE CHEMICAL ECONOMY

The chemical industry, while already contributing to sustainability and decarbonization of its own and other industries, will need to adjust its processes, feedstocks, and products to make these approaches and goals central to its operations. A National Research Council report notes that “sustainable practices refer to products, processes, and systems that support this path” (NRC, 2006a). These processes will not only need to avoid harm to health and the environment but will need to be financially feasible to be widely implemented (NRC, 2006a).

The industry currently contributes to GHG emissions in two major ways. First, it uses primarily fossil fuel–based energy resources. Second, it uses feedstocks that are based on fossil fuels, whose life cycle from extraction to product to waste contributes GHGs. The chemical industry, as noted, also is responsible for some adverse impacts on public health and ecosystems from products that are toxic or in other ways hazardous.

In 2020, the chemicals value chain ranked as the third-largest industrial subsector source of GHG emissions behind cement and steel (Aden et al., 2020), and is the largest industrial consumer of energy. This is in large part because the hydrocarbons used as feedstocks are also considered fuels. Unlike when used directly for energy production, much of the carbon in those feedstocks stays locked into the products, and as a result, the short-term CO₂ emissions are lower than would be expected based on the industry’s apparent energy consumption. Because many of the chemical industry’s products are commodities sold on price, there has been significant prior focus on reducing production costs, including through process energy efficiency. This has resulted in a nearly 25% reduction in nonfeedstock energy use between 1977 and 2014, such that 58% of the apparent energy input is actually in the feedstocks themselves (IEA, 2018; Kätelhön et al., 2019; Levi and Cullen, 2018). Yields in these processes are quite high, with only 15% of the carbon input leaving as waste products. Thus, further reductions in carbon emissions by the chemical industry will require approaches outside of traditional optimization strategies. The World Economic Forum noted that this sector can reduce its carbon emissions by shifting to renewable feedstocks and energy, increasing energy efficiency in its processes, and discovering new innovations in products and processes (Brudermüller, 2020).

A sustainable chemical industry of the future will increasingly base its manufacturing on plant-based biomass, abundantly available CO₂, and end-of-use waste, which will play a crucial role in a circular economy (Clark et al., 2016) (Figure 3-1). It will be powered by renewable energy sources, such as solar and wind energy, and by renewable hydrogen (derived from water splitting using renewable energy sources) to eliminate the carbon footprint of fossil fuels. The widespread availability of plant- and waste-based biomass, solar, and wind energy gives us good reason to think that this grand vision can become a reality. For this to happen, an editorial by Subramaniam et al. (2021a) notes that it is important for the current industry to develop “viable technologies to make chemicals and fuels from these emerging feedstocks, finding processes that minimize resource consumption.” Fundamental research in the chemical sciences is critical to meet these challenges in a prudent and holistic manner, balancing economic, social, and environmental considerations. Select research areas in support of these aims are discussed in Section 3.4.

The shift is likely to proceed when existing companies reorient their goals and new entrants that operate in the new paradigm join the chemical economy. Fundamental chemical research will play a central role in operationalizing this shift. Chemical transformations have historically been performed under harsh conditions, for example, using extreme temperatures and pressures and corrosive reagents. Negative impacts of these processes and resulting products on human and ecosystem health were often treated as unforeseeable or unavoidable by decision makers at chemical companies. Green chemistry (Anastas and Warner, 1998), popularized by Paul Anastas and John

Warner, however, is predicated on the idea that these negative consequences are avoidable through targeted development of less toxic and less material- and energy-intensive processes. Advances in chemistry tools, such as circular chemistry modeling and prediction of chemical toxicity, have improved the ability to project the public health and environmental footprint of new innovations, thus reducing the probability of inadvertently introducing these compounds into the environment. Even so, continued monitoring of public health and the environment, using among other tools, chemistry-based instruments, and drawing on chemical knowledge to understand processes is vital to detect the unanticipated impacts of these innovations. While progress is being made in this direction, there are opportunities for basic chemical research to develop more benign substitutes and support the shift to a regenerative paradigm, for instance in agriculture (McBride, 2020).

There is also a need for thoughtful co-design for end-of-life considerations. One article notes that “increasingly bundled under the heading ‘Circular Economy,’ closed-loop systems keep products, components, and materials at their highest utility and value—reducing the need for extracting and processing new resources, and in the process, reducing related impacts on the environment” (Volans and United Nations Global Compact, n.d.). If these systems are well designed, they can help businesses capture untapped value by collaborating across the value chain and the wider ecosystem. A major advantage of closed-loop business models is that waste streams are more homogeneous, allowing for more effective recycling and reclamation approaches. However, products such as plastics need to be redesigned with both product specifications and effective recycling, particularly chemical recycling, in mind. This co-design process requires investments in basic research to develop new polymers and both the building blocks and processes to achieve them (Britt et al., 2019).

The paradigm shift to sustainability is by no means easy to operationalize, but on the bright side, it has been embraced by segments of the chemical sector. For instance, the Green Chemistry

and Commerce Council has led in advocating for the shift to sustainable chemistry. In several cases, the shift to green chemistry has had financial payoffs as well as improved the environmental footprint for specific companies. Additionally, closed-loop business models are being pioneered by corporations who are taking full responsibility for the cradle-to-grave-to-rebirth of their products and packaging. The chemical industry’s recognition of its reliance on the social license to operate has contributed to efforts to innovate such programs to reduce its public health and environmental footprint (Finger and Gamper-Rabindran, 2013; Gamper-Rabindran and Finger, 2013).

The need for decarbonization of the chemical economy has found support among a subset of companies. Presenters to the committee discussed their efforts to shift to renewable energy for their electricity and to shift away from fossil fuel–based feedstocks (Maughon, 2021; van Tol, 2021). However, according to Ernst & Young, “less than 40% of U.S.-headquartered chemical companies in the ICIS [Independent Commodity Intelligence Services] Top 100 have published net-zero climate goals or climate goals aligned with the Science Based Targets initiative” (Weick et al., 2021). Even these net-zero pledges may overstate decarbonization commitments, since some studies have shown that net-zero pledges by companies are inconsistent with their actual GHG emissions trajectories (In and Schumacher, 2021).

3.2.1 Benefits of the Move Toward Sustainability

As highlighted in Chapter 2, the chemical economy is global and highly competitive, which complicates technology investments, especially where changes will incur cost increases. We highlight some cases in which the shift to sustainability can provide companies with a competitive advantage and a profitable strategy. Basic chemical research deployed to solve challenging sustainability issues can potentially result in patentable knowledge, giving the patent holder opportunities to license to companies worldwide.

3.2.1.1 U.S. Competitive Advantage in Innovation-Intensive Products

Investing in basic chemistry R&D, plus deployment to bring products to the marketplace, provides one strategy for the United States to secure a competitive advantage in the invention and manufacturing of innovation-intensive products, which meets the growing market demand for environmental protections. For instance, the United States leads in the innovation and manufacturing of hydrofluorocarbon (HFC) substitutes. This has given U.S. chemical manufacturers a competitive advantage as countries, following the Kigali Amendment to the Montreal Protocol, are shifting away from HFCs. HFCs replaced chlorofluorocarbons (CFCs) as refrigerants. While HFCs are not ozone depleters (as CFCs were), HFCs turned out to be powerful GHGs, significantly more potent than CO₂. U.S. leadership in the innovation and manufacture of HFC substitutes was cited by congressional representatives in their support for legislation that directed the United States to sign onto the Kigali Amendment (Gamper-Rabindran, 2022).

3.2.1.2 Green Chemistry: Profits While Reducing Health and Environmental Footprint

Given the domestic and global pressures for sustainability (see Section 3.2.2) and the need for companies worldwide to implement solutions, basic research in these areas could well result in significant payoff. Innovation of green processes and products could make companies competitive and profitable, and expansion of chemical knowledge could lead to companies securing patents for eco-technologies and revenue from their licensing (Hennessey, 1996). For instance, the adoption of green chemistry precepts in the United States spurred the growth of green chemistry–related

patents, though information is not readily available on the extent to which these translated into licensing opportunities (Nameroff et al., 2004).

The shift to green chemistry has both increased company profits and reduced their environmental footprint. In 1995, the EPA established the Presidential Green Chemistry Challenge Awards (now known as the Green Chemistry Challenge Awards)² to highlight scientific and technical advances in green chemistry. There are many illustrative examples of awardees where green chemistry has reduced inputs, environmental impacts, and in some cases production costs. We highlight a few of them:

• Merck & Co., Inc. dramatically improved on their original synthesis of a chronic cough medicine, gefapixant citrate, and were awarded the 2021 Greener Synthetic Pathways Award.³ By innovating on at least four steps of the process, they achieved higher yield and a sixfold reduction in raw material costs and were able to replace a step that previously involved hazardous chemicals. By improving the energy efficiency of their process, they generated cost savings and reduced CO₂ and carbon monoxide (CO) emissions.
• Thermal paper (which has been widely used for receipts, tickets, and other labels) can contain bisphenol A (BPA), a potentially toxic chemical. Evidence of BPA transfer from paper to skin and absorption into the body was a motivation for Dow Inc. working with Papierfabrik August Koehler SE to develop an alternative. In 2017, they were awarded the Designing Greener Chemicals Award (EPA, 2017) for producing a thermal paper that eliminated reactive chemistries such as BPA, increased longevity of the receipt image, and was compatible with existing commercial thermal printers. This paper was designed to take advantage of the physical properties of the polymers in the paper rather than use chemical reactions to create the image.
• Life Technologies was awarded the 2013 Greener Synthetic Pathways Award (EPA, 2013) for developing a three-step one-pot synthesis process for the production of chemicals for polymerase chain reactions. This dramatically improved efficiency of conventional techniques, reducing solvent consumption by up to 95% and by 65% for other hazardous waste, and has reduced hazardous waste by 1.5 million pounds per year.
• Geoffrey Coates was awarded the Academic Award (EPA, 2012) as part of the Presidential Green Chemistry Challenge for developing catalysts that convert CO₂ and CO into polymers. This technology was the basis for Novomer Inc., a start-up company whose Converge® polyol technology was acquired by Saudi Aramco in 2016 and valued at $100 million (Aramco, 2016). Aramco is using these catalysts to manufacture coatings that require 50% less petroleum to produce. These coatings have applications in food and drink can linings and at full market penetration were projected to have the potential to sequester and avoid 180 million metric tons of annual CO₂ emissions.

3.2.2 Pressures for Decarbonization and Sustainability

The chemical industry is likely to face continuing pressure to decarbonize and to become sustainable, though policy signals in the United States have not been uniform or consistent. Keeping the average global temperature rise to below 1.5°C is necessary to avoid the worst of the adverse climate impacts. By 2030, global GHG emissions would need to be halved relative to 2005 levels if the world is to meet the aspirational goal under the Paris Climate Agreement to limit global warming to 1.5°C.

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² See https://www.epa.gov/greenchemistry/green-chemistry-challenge-winners.

³ See https://www.epa.gov/greenchemistry/green-chemistry-challenge-2021-greener-synthetic-pathways-award.

3.2.2.1 Domestic Pressure for Decarbonization

In April 2021, President Biden pledged to halve U.S. GHG emissions relative to 2005 levels by 2030 in the U.S. Nationally Determined Contributions under the Paris Climate Agreement. However, support for climate actions has been mixed among members of Congress and among state governments. Nevertheless, the ever more frequent climate-enhanced extreme weather disasters could compel more voter support for decarbonization policies (Gagliarducci et al., 2019) and prompt action at the federal and state levels as well as increase direct consumer or investor pressure on companies to reduce their carbon footprint (Breckel et al., 2021). A nationally representative survey of 1,000 respondents in September 2021 reported that “94% of liberal Democrats and 80% of moderate/conservative Democrats say global warming should be a high or very high priority for the President and Congress,” while 45% of liberal/moderate Republicans and 17% of conservative Republicans say the same (Leiserowitz et al., 2021).

Investor pressure prior to the Biden administration and federal policies in the Biden administration provide some, but not uniform, signals for decarbonization. In 2020, at least 220 of Standard & Poor’s 500 companies reported their climate change risks in their U.S. Securities and Exchange Commission (SEC) filings, including Chevron and Gilead Sciences (Ramonas and Rund, 2021). While the SEC has not made such reporting mandatory, investor pressure has led to this voluntary reporting. The European Union (EU) has required climate change risk reporting since 2018 (Ramonas and Rund, 2021).

SEC Chairman Gary Gensler has proposed a new rule amendment on Enhancement and Standardization of Climate-Related Disclosures (SEC, 2022). Disclosures would include

In October 2021, Federal Reserve Governor Lael Brainard confirmed that the Federal Reserve “is developing scenario analysis tools to model the economic risks of climate change and assess the resilience of the entire financial system” (Newburger, 2021). This could lead the financial sector to reassess its financing of the chemical sector, particularly those that are more prone to risks from direct climate impacts or from risks to existing business models from climate mitigation actions, including regulations to curb GHG emissions (Gamper-Rabindran, 2022).

3.2.2.2 Global Pressure for Decarbonization

The U.S. chemical sector is under international pressure for a lower energy footprint, including from the EU. In July 2021, the EU announced its adoption of the Carbon Border Adjustment Mechanism (CBAM), which will begin to take effect in 2023 (EC Directorate-General for Taxation and Customs Union, 2021). That tax will raise the cost of a small number of U.S. exports to the EU for affected goods that are intensive in GHG emissions (Figure 3-2). Ammonia is currently the only chemical covered by CBAM, and there are concerns that its inclusion will have unintended economic consequences for Europe, including increasing the “downstream production costs of hundreds of chemicals in the ammonia value chain” (CEFIC, 2022b). U.S. producers will still need to consider how energy efficiency for their products compares to that of other producers. Although the EU and the U.S. chemical industries focus on different markets, the EU chemical industry

reports that it made significant strides in reducing its energy intensity by 3% a year between 1991 and 2017 (CEFIC, 2020).⁴

It is difficult to predict the full impact of programs such as the recent CBAM legislation as part of Europe’s Fit for 55 agenda. The European chemicals industry is concerned about how CBAM might impact its long-term competitiveness. In 2019, the EU was the largest chemical exporter globally based on value, and increased costs for their products could negatively affect their export position if other regions do not follow through with similar carbon taxes (Eurostat, 2021). There is a recognition that increased carbon taxes could have an adverse effect if not managed appropriately (Condon, 2021). Simultaneously, there is an expectation that the proposed legislation will result in increased funding for innovation that the chemical industry will need to develop different business

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⁴ These figures would capture both energy reduction from a shift out of energy-intensive products and a shift to cleaner energy sources.

models as part of its move toward a circular economy (Beacham, 2021). If similar support for fundamental research in the United States is not forthcoming, it may hinder the speed and effectiveness of the ability of the U.S. chemical industry to decarbonize and compete in an economy that values energy efficiency and reduced carbon emissions.

3.2.2.3 Domestic Pressure for Sustainability

Chemical companies have faced significant legal liability and financial penalty when their products adversely affect public health. Two examples are lawsuits against the manufacturers of glyphosate and PFAS.

Legal action related to glyphosate.

Glyphosate, an herbicide developed by the Monsanto Company, was used in the first attempt at weed control and management by applying a herbicide on fields planted with genetically modified glyphosate-tolerant crops. Glyphosate has been registered as a pesticide safe for use since 1974 (EPA, 2020), and John Franz was awarded the National Medal of Technology and Innovation in 1987 for his discovery of the herbicidal properties of glyphosates, because of their significance to agricultural practices globally. However, in 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as being a probable carcinogen to humans, spawning a broad review of its use in agriculture. Bayer, which purchased Monsanto in 2018, assumed ownership of and legal liability for Roundup, the brand name for a glyphosate-based weed killer (Hals, 2021). Although the IARC classified glyphosate as a probable human carcinogen in 2015, an EPA review concluded that there was no risk to human health when used according to the label (EPA, 2020). As of 2021, the product does not carry a warning label of a probable human carcinogen.

Bayer faces ongoing lawsuits from cancer patients who allege that Roundup use had caused their cancer. As of 2021, three cases had gone to trial, with the jury awarding plaintiffs millions of dollars in damages. In May 2021, Bayer announced it was reconsidering its residential sales of Roundup in the United States after a judge dismissed its proposal for responding to class action lawsuits on Roundup as unreasonable (Hals, 2021). Partly as a result of more than 125,000 lawsuits largely related to residential use of Roundup, Bayer announced on July 29, 2021, that it would discontinue offering glyphosate-based products for residential use and would reformulate those products starting in 2023 (Erickson, 2021).

The use of glyphosate and glyphosate-tolerant crops has been debated. One view, within the pesticide-is-essential-to-agriculture community, is that reduction in the use of glyphosate and glyphosate-tolerant crops will cause declines in crop production. For instance, one review of the impacts of removal of glyphosate and glyphosate-tolerant crops estimates losses of $6.76 billion in global farming incomes annually and annual reductions of the output of soybean, corn, and canola crops by 18.6, 3.1, and 1.44 million tons, respectively (Brookes et al., 2017). The review estimates a replacement with 8.2 million kg of other active herbicides, which would have a net environmental impact quotient of 12.4% relative to the use of glyphosate. A competing viewpoint, anchored in the paradigm of regenerative agriculture, points to the treadmill of glyphosate-resistant weeds (González-Torralva et al., 2012; Livingston et al., 2015), risks to pollinator populations (Motta et al., 2018), and adverse impacts on soil health (Soil Association, 2016).

Legal action related to PFAS.

PFAS manufacturers have also faced several expensive verdicts and settlements. These include “an U.S.$850 million settlement with a state attorney general in 2018; a U.S.$671 million settlement to resolve 3,550 lawsuits in 2017; and a U.S.$83 million settlement in 2021 to resolve nearly 100 personal injury claims, and a cost-sharing arrangement to address up to U.S.$4 billion in PFAS legacy liabilities” (Birnbaum et al., 2021). Revelations that companies producing these compounds became aware of the health and environmental impacts of these chemicals but failed to immediately notify regulators and end their use (Richter et al., 2021;

UCS, 2019) have tarred the public perception of these companies (U.S. Congress, 2019). Such revelations also tar the social license of the chemical sector more broadly. PFAS contamination, an extreme case with billions in potential liability and high-profile contamination, has resulted in companies’ stock market declines. An article in C&EN notes that “between January 2018 and September 2020, DuPont’s shares fell 45%, 3M’s dropped 31%, and Chemours’s plummeted 59%. 3M and DuPont, and then the DuPont spin-off Chemours, were major producers of PFAS” (Zainzinger, 2020).

3.2.2.4 Global Pressure for Sustainability

In October 2020, the European Commission announced the EU Chemicals Strategy for Sustainability whose goals are to position “the EU industry as a globally competitive player in the production and use of safe and sustainable chemicals” and to “protect human health and the environment from harmful chemicals.” The proposed requirement for the “one substance, one assessment” process aimed to strengthen the principles of “no data, no market.” That proposal, which builds on the previous Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Directive, will favor exports to the EU that meet higher standards for safety and sustainability (EC, 2020a). To support this change, a 2020 European Commission survey found that 8 in 10 EU citizens continue to worry about the impact of toxic chemicals in everyday products. Nine out of 10 people are concerned about the impact of chemicals on the environment and a slightly smaller proportion (85%) about their impact on health (Chemical Watch, 2020).

Additionally, policies discouraging the use of single-use plastics have ramifications for chemical companies, especially those that produce polyethylene and polypropylene for the consumer packaging sector. The decrease in single-use plastics consumption could also lead to overcapacity and a decrease in returns (Dickson et al., 2022). In 2019, 170 countries supported a UN resolution to reduce plastics use by 2030 (BBC News, 2019). China, Kenya, the United Kingdom, the EU, and several U.S. states (California, Connecticut, Delaware, Hawaii, Maine, New York, Oregon, and Vermont) have moved to ban some types of single-use plastics. In 2020, Canada announced its proposal to regulate “plastics as a toxic substance under the Canadian Environmental Protection Act, and to ban outright the manufacture and import of many single-use plastics by 2021” (ECCC, 2019).

Numerous countries in North America and Europe have long relied on China and a number of developing countries as the destination for their plastics waste. China implemented the National Sword Policy in 2018, which bans the import of most plastic waste material, and the 2019 Amendments to the Basel Convention list plastic waste as conditionally hazardous. Effective January 2021, signatories to the Basel Convention are restricted in what plastic waste shipments they can export to developing countries (Seay et al., 2020). The decision of China to cease accepting such waste and the Basel Convention restriction on waste shipments to developing countries means that there is no longer a cheap offshore destination for waste, and plastic waste will need to be addressed at the national or continental level. This has spurred greater action in these countries to restrict use of single-use plastics.

As a holistic approach to this problem, circular economy schemes such as extended producer responsibility (EPR) (OECD, 2006) are being proposed to shift responsibility around recycling and reuse of plastics from the public sector to the manufacturers, and to incentivize rethinking of product and packaging design. Depending on the EPR policy, this can also raise funds for more effective management of the remaining waste. In the EU, the Packaging Waste Directive (94/62/EC), implemented after limited success with voluntary take-back programs, has resulted in a variety of mandates and mechanisms in which manufacturers pay for collection and recycling of packaging

materials, at least in part (Rogoff, 2014). Countries implementing EPR have seen success in material usage reduction and increased recycling (Rubio et al., 2019). More recently,

3.2.3 Challenges for Decarbonization and Sustainability of the Chemical Economy

Fully operationalizing the shift to sustainability and decarbonization will require reorientation of investment and production patterns for companies in the chemical sector and their entire supply chain. To make such an expensive and financially risky pivot, the private sector will need assurance that this shift can be profitable and will be applied in a harmonized fashion so they can maintain a long-term competitive position. Policies that are uniform and durable would provide these assurances and support the economywide shift to deep decarbonization and sustainability.

However, in reality, the chemical sector operates in a system in which externalities are pervasive. In most cases, prices do not capture the benefits provided by energy efficient and sustainable products and processes, nor do they reflect the costs of polluting production and processes. Additionally, the chemical sector operates in a system in which policies are not durable, which hampers long-term investments. The impact on the chemical sector of policies enacted by the U.S. government are mixed at best, and the policies or their enforcement are prone to change across administrations.

Although investors are beginning to consider environmental, social, and governance (ESG) factors in investments, narrower financial concerns still dominate (Zainzinger, 2020). ESG metrics are evolving. Thus, the failure to price externalities puts products with superior environmental attributes at a disadvantage as they are more “expensive” in a simplistic sense. There is some evidence though that ESG matters. According to an October 2020 report by the investment firm Jefferies, which surveyed more than 2,100 individual investors in the United States, the UK, Germany, and China,

However, one piece from C&EN notes that “ESG goals can be more of a risk-mitigation strategy than a driver for change” (Zainzinger, 2020). The same piece quoted Ronald Köhler, head of investor relations at Covestro, as saying, “Unfortunately, it is not yet the case that companies get rewarded for being sustainable. Rather, they get punished for not being sustainable.” This piece noted that there is only pressure on large chemical companies to adopt sustainability, while small and midsize ones will not implement such practices for years (Zainzinger, 2020).

There are other hurdles on the road to decarbonization and sustainability. The U.S. Government Accountability Office reviewed federal programs in support of green chemistry (GAO, 2018). That study, which interviewed experts from academia, government, and industry, identified several barriers to green chemistry, including

For companies faced with the transition, their choice is in the continuum from resisting to greenwashing to making the transition (Green et al., 2021).

3.3 POLICIES TO ASSIST IN ADOPTION OF SUSTAINABILITY AND DECARBONIZATION

Presenters to the committee from industry emphasized the need for well-designed market-based and regulatory policies that favor the more sustainable products and processes. These policies create the certainty that enables companies to take a long-term investment approach into sustainability and decarbonization. Presenters’ views echo the Porter hypothesis in economics literature that “well-designed and stringent environmental regulation can stimulate innovations, which in turn increase the productivity of firms or the product value for end users” (van Leeuwen and Mohnen, 2017).

Companies that sell products directly to consumers have been able to implement business models that tie their brand firmly to sustainability and to profit from implementing that brand, for example, Adidas implementing EPR to promote recycling (Adidas, 2021). Some chemical companies have also adopted similar programs, such as Braskem’s “I’m green” product line. A paper by Iles and Martin (2013) describes how the company was successful in developing standards and then using carbon measurements to demonstrate that their bioplastic polyethylene reduced environmental impact as compared to other polyethylenes.

3.3.1 Regulatory Policies

Several of the previous examples illustrate how regulatory policies that restricted or banned a process or product enabled a more benign substitute to enter and compete in the marketplace. Nevertheless, political dynamics have made it difficult to promulgate and implement regulatory policies that penalize products with harmful health and environmental consequences. Innovators favor policies that reward sustainability and decarbonization, but the established companies that produce the less sustainable and more carbon-intensive products fight to keep their market share. Incumbents have been successful at opposing policies that would restrict the use or raise the price of their products or processes.

These dynamics continue to the present day. For instance, the Union of Concerned Scientists argue that Dow Chemical, producer of chlorpyrifos, lobbied hard for the EPA under the Trump administration to reverse the EPA’s 2015 decision supporting the ban on chlorpyrifos (UCS, 2017), though Corteva Agriscience, formerly Dow AgroSciences, agreed to phase out production of chlorpyrifos in 2020 after facing pressure from California and the EU (Erickson, 2020). Wagner and Steinzor (2006) document the challenges that regulatory agencies face in presenting the science to justify stricter regulations in the face of industry’s strategies in the legal and scientific arenas. Wagner and Steinzor (2006) call for robust government investment in research that advances understanding of how chemical products and processes affect health and the environment. That research is fundamental to building the body of scientific evidence to enable the promulgation of regulations, which in turn can incentivize a shift to more sustainable products and processes.

3.3.2 Market-Based Policies on Carbon

Well-designed market-based policies that put a price on carbon make it less profitable for companies to use fossil fuel–intensive processes or fossil fuel feedstocks, and thus incentivize the shift to decarbonization (CBO, 2013). Carbon taxes set at an appropriate level to capture the climate costs of each ton of GHG emissions would provide such a signal. That market signal can spur companies to invest in decarbonizing their products and processes. However, the political environment at the federal level has prevented the implementation of carbon pricing policies within the United States.

3.3.3 Demand-Pull Procurement and Purchasing

The opposition to regulatory and market approaches that raise the prices or restrict the use of carbon-intensive and less sustainable products and processes means that demand-pull strategies such as procurement can offer more viable solutions. U.S. government procurement programs at the federal, state, and local levels have the potential to provide the demand-pull for energy-efficient and sustainable products (Krupnick, 2020). A number of state and local programs exist, but two federal programs are considered here: the U.S. Department of Agriculture’s (USDA’s) BioPreferred Program and the EPA’s Safer Choice Program. The BioPreferred Program requires federal agencies and their contractors to purchase biobased products when they purchase items such as paints, lubricants, adhesives, and cleaners, among others.⁵ The program saw a 93% increase between 2017 and 2019 in the number of products that the U.S. Department of Agriculture certified as BioPreferred (Golden et al., 2021). EPA’s Safer Choice Program labels products that are safer for the environment, to guide consumers and businesses toward making more sustainable choices.⁶ Programs like these can provide the market demand for products that are perceived as more expensive but are more energy efficient and sustainable than conventional products.

Previous studies have shown that there is a growing interest in green chemistry products—“chemical products and processes that reduce or eliminate the use or generation of hazardous substances” (Golden et al., 2021). That report, prepared for the Green Chemistry & Commerce Council, came to several conclusions about the purchasing of green chemistry products, including that “emerging government policies and investor expectations are fueling growth of the green chemistry sector.” Additionally, the report showed that green chemistry products had a market growth that was more than 12 times faster than that of their conventional counterparts between 2015 and 2019 (Figure 3-3) (Golden et al., 2021). Other studies present some evidence that government procurement policies favoring products with environmental attributes correlated with innovation (Porter, 1991). Advanced market commitments have provided the demand-pull.

3.3.4 Funding R&D&D

Congress has recognized the essential role of chemical R&D—and additionally, the need for public–private sector collaboration—to support the paradigm shift toward products and processes with lower public health and environmental footprints. This is why the focus has expanded to include R&D&D, with the last “D” standing for “deployment.” For example, the Save Our Seas 2.0 Act (Pub. L. No. 116-224) was passed in 2020 to address concerns about plastic pollution in coastal and marine ecosystems. This law mandates a variety of studies and reports on the impacts of microplastics and other plastic pollution, novel uses of plastic waste, and investigation of circular economy approaches and needs for material and waste management.

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⁵ See https://www.biopreferred.gov/BioPreferred/.

⁶ See https://www.epa.gov/saferchoice.

In January 2021, Congress enacted the Sustainable Chemistry Research & Development Act as part of the FY 2021 National Defense Authorization Act (Bergeson & Campbell, P.C., 2021). The Act states that “sustainable chemistry can improve the efficiency with which natural resources are used to meet human needs for chemical products while avoiding environmental harm, reduce, or eliminate the emissions of and exposures to hazardous substances, minimize the use of resources, and benefit the economy, people, and the environment.” The Sustainable Chemistry R&D Act is meant to coordinate interagency efforts to accelerate U.S. innovation in this emerging area of market growth (Jalbert, 2021). The law directs the White House Office of Science and Technology Policy to “convene a multi-agency task force that will, for the first time, coordinate federal funding and promotion of sustainable (i.e., green) chemistry research” (Hogue, 2021). The interagency working group will develop a consensus definition of “sustainable chemistry” and “a framework of attributes characterizing, and metrics for assessing, sustainable chemistry” (Bergeson & Campbell, P.C., 2021).

More recently, the Infrastructure Investment and Jobs Act (Pub. L. No. 117-58, H.R. 3684, 117th Cong.) passed in 2021 directs the U.S. Department of Energy (DOE) to establish near-, mid-, and long-term targets for the hydrogen R&D&D program. In section 813, it directs the Secretary of Energy to establish at least four regional clean hydrogen hubs to aid the demonstration of production, processing, delivery, storage, and end uses of clean hydrogen. To accomplish this, $8 billion is appropriated for these activities for fiscal years 2022–2026. Regarding clean hydrogen in manufacturing, priority is given to manufacturing projects that increase efficiency and cost-effectiveness. Additionally, the act directs DOE to issue awards “for research, development, and demonstration projects to advance new clean hydrogen production, processing, delivery, storage, and use equipment manufacturing technologies and techniques” (117th Cong. H.R. 3684, 2022). For this work, $500 million is appropriated for fiscal years 2022–2026.

The act also directs the establishment of a clean hydrogen electrolysis program focused on reducing the cost of electrolytically produced hydrogen to less than $2/kg by 2026. The program will also carry out demonstrations, and seek to scale up technology including the integration of compression, drying, storage, and transportation systems. For these activities, $1 billion is appropriated for fiscal years 2022–2026.

3.4 FUNDAMENTAL CHEMICAL RESEARCH FOR SUSTAINABILITY, DECARBONIZATION, AND ENVIRONMENTAL STEWARDSHIP

The pressing need to attain the United Nations’s SDGs provides numerous opportunities for chemical R&D to advance our knowledge and innovate solutions in support of decarbonization and sustainable development in the broadest sense. Table 3-2 lists future-looking chemical topics that are discussed in the remainder of this chapter and the SDGs on which these knowledge advances may have an impact.

3.4.1 Sustainability Assessments

Global environmental and safety regulations for new and existing chemicals and materials are aimed at encouraging development of technologies that are inherently safer and sustainable

TABLE 3-2 Opportunities for Fundamental Chemical Research and How They Contribute to the Sustainable Development Goals

(EC, 2020b; U.S. Congress, 2019). A U.S. Government Accountability Office report (GAO, 2018) concludes that quantitative sustainability assessment is vital for timely implementation of sustainable chemical technologies. The 2019 United Nations Environmental Programme report (UNEP, 2019) concurs with this sentiment. Life-cycle assessment (LCA) tools are increasingly available to quantify the ecological impacts of a chemical product during its complete life cycle, which includes manufacturing, use, and disposal (“cradle-to-grave”) or recycling (“cradle-to-cradle”) phases (Figure 3-4). The environmental burdens during the manufacturing phase stem from not only unit operations within the chemical plant but also the extraction of the raw materials that often occurs far away from the chemical plant.

LCA is essential to provide rational guidance for implementing circular chemistry, which refers to a framework that promotes sustainable practices throughout the life cycle of a chemical product. Circular chemistry is characterized by near-total carbon atom economy and minimal adverse impacts on the environment and human health (Keijer et al., 2019). To perform quantitative sustainability assessment, metrics such as atom economy, process mass intensity, and the environmental factor are available to determine if feedstock resources are being efficiently used to make the desired products (Allen and Shonnard, 2001). Several software tools that incorporate such metrics are available in the open domain for estimating environmental impacts of chemical products and processes. For example, the American Chemical Society’s Green Chemistry Institute has made available several tools to guide the selection of green reagents, including the Green Chemistry Innovation Scorecard Calculator.⁷ The EPA has introduced online tools to estimate the effects of chemical processes and products on the environment and human health. These include the environmental fate, bioaccumulation, and toxicity of chemicals.⁸ New tools continue to evolve, incorporating predictive toxicology, product biodegradability, and even social dimensions as part of a comprehensive sustainability assessment (Zimmerman et al., 2020).

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⁷ See https://www.acs.org/content/acs/en/greenchemistry/research-innovation/tools-for-green-chemistry.html.

⁸ EPI Suite™-Estimation Program Interface, https://www.epa.gov/tsca-screening-tools/epi-suitetm-estimation-programinterface.

To compare the environmental impacts of conventional processes and alternative chemistries or technologies, LCA tools such as SimaPro,⁹ GaBi,¹⁰ Materials Flows through Industry (MFI),¹¹ and GREET¹² are available. The Economic Input-Output Life Cycle Assessment (EIO-LCA),¹³ developed at Carnegie Mellon University, estimates the material and energy consumption of a chemical product, along with its associated environmental impacts in various economic activity sectors across the supply chain. The Department of Energy’s National Energy Technology Laboratory also provides a suite of reports and tools on LCA of energy technologies and pathways.¹⁴ When LCA methods are used early in development, and throughout a process life cycle, the assessments can be useful in guiding research and public policy decisions (Bento and Klotz, 2014; Sharp and Miller, 2016). Incorporating sustainability metrics to guide research and process development is essential to achieve sustainable processes and products in a timely manner. To be useful in comparing tradeoffs between alternatives, LCA relies wholly on reliable life-cycle inventory metrics for the processes or products modeled and a rigorous process model that accurately accounts for inputs and outputs, both in terms of mass or material flows and energy balances. Advances in fundamental chemistry will continue to inform LCA processes, and vice versa, through better analytical tools and a deeper understanding of chemical matter.

Another emerging aspect of sustainability assessments is the use of systems-level thinking to take a holistic view of what impact a chemical or process might have on the environment or health. Systems thinking is generally defined as “the ability to understand and interpret complex systems” (Evagorou et al., 2009) and includes “visualizing the interconnections and relationships between the parts of the system; examining behavior that changes over time; and examining how systems-level phenomena emerge from interactions between the system’s parts” (Orgill et al., 2019). In relation to sustainability, the idea is to incorporate more information into standard LCAs, sometimes termed a life-cycle and sustainability assessment. LCAs are already a systems-based analysis approach, and the incorporation of broader systems thinking encourages other considerations, including “revealing macro-level impacts, consideration of social and economic impacts, and taking into account underlying mechanisms” (Onat et al., 2017). This approach is particularly important in chemistry due to the impact that chemistry and chemical methods have on many other areas of science and manufacturing. As shown in this chapter and Chapter 2, many different aspects of society, policy, economics, and the environment impact, and are impacted by, changes in the chemical enterprise. Current supply-chain concerns, for example, touch all facets of society. Continued research on the interconnectedness of chemicals, the environment, and society remains critical, and advancing basic understanding of individual chemicals and methodologies will increase our ability to understand the whole enterprise.

3.4.2 Resource-Efficient Chemistry

Feedstocks that come from greener sources and allow for more efficient reactions will be vital to the green chemistry landscape. New fundamental research will be needed to explore the use of circular feedstocks and for altering reaction conditions to be more energy efficient.

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⁹ Pre Consultants, SimaPro Life Cycle Assessment Software, www.pre-sustainability.com/simapro.

¹⁰ GaBi Life Cycle Assessment Software, www.gabi-software.com/america/index/.

¹¹ See https://mfitool.nrel.gov.

¹² Argonne GREET Model, http://greet.es.anl.gov/.

¹³ Carnegie Mellon University Green Design Institute’s Economic Input-Output Life Cycle Assessment, www.eiolca.net/.

¹⁴ See https://netl.doe.gov/LCA.

3.4.2.1 Plastics and Polymer Production and Recycling

Plastics production has grown to more than 100 lbs of plastic per person every year,¹⁵ and plastics are needed by nearly every manufacturing industry (Figure 3-5). Global production of polyolefins (polyethylene and polypropylene) is greater than any other plastic because they are derived from an inexpensive feedstock such as natural gas. Additionally, they have extraordinarily useful properties: low density, resistance to degradation, resistance to swelling from both water and common hydrocarbons (grease, oil, cleaning solvents), and easily molded or blown into packaging film. Beyond polyolefins, the other plastics with high annual production numbers include polyesters, polyamides, and polyurethanes.

Plastics were discovered in the early 1900s when the first synthetic material, Bakelite, was developed serendipitously by Leo Baekeland. Plastic quickly became known as the material of “1,000 uses” and was manufactured on a mass scale for everything from telephones to jewelry. Today, polymeric materials can be found in almost everything that we touch and see, from food packaging to single-use disposable medical equipment to excipients in pills. Plastics are an important and well-integrated part of the chemical economy. However, the very properties that make plastics so useful have caused severe stress on the environment: microplastics fill our oceans, sachets clog waterways in Africa leading to flooding and disease, and microscopic fibers from clothes can be carried by the wind and found in soil samples across the world. Estimates for the naturally occurring breakdown of plastic in the environment is 1,000 or more years. There exists a need, therefore, to collect waste plastics prior to environmental dispersion and to develop waste separation techniques and waste treatment plants to recover the valuable chemicals and embodied energy contained within the covalent bonds of the materials.

During the transition to a circular plastics economy and for dealing with recalcitrant plastics, biodegradable plastics have been proffered as a part of the solution to uncollected plastic waste.

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¹⁵ Calculated from 7.753 billion worldwide population in 2020 and 368 million metric tons of plastics produced.

However, currently available biodegradable plastics have limited uses due to their often-brittle characteristics (Narancic et al., 2018). They may be suitable for some packaging applications, in single-use items, and in some agricultural uses, being mindful, though, of potentially hazardous degradation by-products (Dilkes-Hoffman et al., 2019; Flury and Narayan, 2021). Importantly, if the feedstocks for biodegradable plastics are not renewable, biodegradable plastics can be a vehicle for higher carbon emissions than the alternative in the short term (Zheng and Suh, 2019). Emissions can arise from both their production and accelerated degradation. Successful biodegradation often requires industrial composting and therefore extra energy, and degradation intrinsically yields carbon emissions. There is active development of biodegradable plastics, but research is needed to support improved materials properties, optimize degradation conditions, and understand the environmental and life-cycle implications and tradeoffs (Flury and Narayan, 2021). Despite the potential value of biodegradable plastics, reducing the volume of uncollected plastic waste and thereby decreasing the loss of material and energy remains the preferable approach.

Unlike paper, discussed in Box 3-1, plastics are a structurally diverse group of polymers with different chemical properties. For example, polyolefins are long-chain molecules containing only carbon and hydrogen atoms. Therefore, they have few “chemical handles” to use to chemically break down the polymer via common chemical reactions into monomers that can be used as building blocks for new polyolefins. Polyesters, polyamides, and polyurethanes, on the other hand, because they contain functional groups, are easier to degrade chemically and convert to small molecules and starting materials. Economically viable recycling processes are being developed for polyamides (Suntinger, 2020), polyurethanes (Laird, 2021), and especially for the polyester used commonly in bottled-water containers (Smalley, 2021; Tudball, 2022; Tullo, 2021). Through advances in fundamental and applied research in catalysis, it has been demonstrated that even polyolefins can be pyrolyzed back to oils, which can be refined and processed in steam reactors to make building-block olefins for polyolefins in a circular fashion (Gebre et al., 2021). Major plastic makers, ExxonMobil, Dow, SABIC, Eastman, and Chevron Phillips Chemical, have all established efforts to bring capacity for chemical recycling of sorted plastic waste streams. The largest example of this to date is ExxonMobil’s, which is scheduled to come online by the end of 2022. This recycling plant in Texas expects to process 30,000 metric tons of plastic waste per year back into chemical feedstocks for the generation of polyolefins (Tullo, 2021). This is a positive development that was only possible through R&D investments in catalysis and chemical process intensification. This is only the beginning, as this recycling represents less than 0.01% of the plastics produced globally each year. Additionally, it is important to explore and research other chemical recycling methods beyond pyrolysis and to use process and life-cycle analyses to determine which methods are providing the most benefit.

3.4.2.2 Sustainable Synthesis

For the chemical industry, sustainability means safer chemistry, sustainable products, and circular chemistry with carbon efficiency. Sustainable chemical synthesis is one key part of a sustainable chemical economy. Improving reaction rates and selectivities inherently decreases the resources used per reaction and promotes sustainability. Principles of green chemistry and green engineering provide guidelines for choosing reaction components, such as reagents, solvents, catalysts, and operating conditions that minimize adverse health and environmental effects.

Catalytic processes often involve the use of other substances such as water, organic solvents, acids, and bases. Product and catalyst separation steps are typically solvent and energy intensive. The use of certain harmful solvents, such as chloroform and benzene, is banned by international

regulations such as Europe’s REACH. Thus, the choice of greener solvents and greener acids and bases is essential to sustainable synthesis (Byrne et al., 2016; Henderson et al., 2015).¹⁶

The production of catalysts itself may impose environmental damage. For example, catalyst production associated with biofuels can be >10% of the cradle-to-grave GHG emissions for the entire process (Benavides et al., 2017). Homogeneous metal catalyst complexes are often synthesized via multistep procedures that use organic solvents and mineral acids. The production of TiO₂ (used in photocatalysis and as catalyst support) from ilmenite (FeTiO₃) ore is energy intensive, requiring temperatures of 1,500–2,000 K. It also requires corrosive reagents, such as chlorine, and generates large amounts of waste (Gázquez et al., 2014). In all of these cases, there is a need for research to find benign manufacturing processes with reduced environmental and health impacts.

The increased demand for elements that are widely used as catalytic metals is also raising sustainability concerns. For example, palladium (Pd) catalysis is enormously important in the synthesis of pharmaceutical precursors due to its versatility, selectivity, and robustness in a number of C–C and C–X bond-forming reactions. A widely held notion is that the continued use of such platinum group metal (PGM) catalysts is not sustainable (Hayler et al., 2019). However, this view may not take into account the shift away from internal combustion engines (ICEs). As transportation becomes electrified, there will be less need for catalytic converters, which rely on PGMs to function. In 2020, the automotive catalyst industry accounted for approximately 90%, 85%, and 32% of the worldwide Pd, rhodium (Rh), and platinum consumption, respectively (Cowley, 2021). The decline in ICE demand related to the shift toward electric vehicles will result in a commensurate drop in the demand for PGMs in automotive emission control catalysis. A steadily increasing inventory in Pd and Rh accompanied by declining prices is forecast, especially after 2030 (Hochreiter, 2021). Recognition of this impending trend might encourage renewed exploration of new areas of chemistry for PGMs, especially Pd and Rh.

There is significant work on exploring Earth-abundant transition metal catalysts (iron and nickel) as cost-effective and more sustainable replacements for PGMs (Plett and Bernales, 2016). Such alternative formulations often require much higher catalyst loadings and expensive ligands. Higher metal loadings increase the possibility of residual metals contamination that is unacceptable for the end-product use, and may require cleaning procedures that are environmentally deleterious (EMA, 2019). Furthermore, nickel is likely to be in short supply in the future as a result of the twofold increase in its demand to build secondary battery technologies (IEA, 2021b). One possible way to address this is to further consider chemical capabilities for recovering and reusing critical metals from batteries. Some work is being done to include this as a solution (Sensiba, 2021), but continued chemical research is needed to increase the efficiency of recovery and bring these technologies to scale (Petranikova et al., 2022). Clearly, evolving demand trends, where cost and availability can be dependent on emergent technologies and international policy (Blas, 2022; Rosevear, 2022), must be carefully considered to rationally guide the quest for new catalytic materials. These considerations would benefit from using comprehensive process and life-cycle analyses to help chemists and chemical engineers focus on materials and processes that will have the least adverse environmental impact.

3.4.3 Greenhouse Gas Reduction Strategies

GHG emissions—primarily CO₂—are largely the result of fossil fuel combustion. Fundamental chemical research can play critical roles in helping to establish renewable energy sources, electrification of engines, and improved methods of carbon capture, utilization, and storage (CCUS).

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¹⁶ See also ACS’s Solvent Selection Tool, https://www.acs.org/content/acs/en/greenchemistry/research-innovation/toolsfor-green-chemistry/solvent-selection-tool.html.

3.4.3.1 Renewable Feedstocks for Energy

The chemical industry currently derives its raw materials and energy primarily from fossil sources. To make the transition to sustainably manufacture its myriad products, the chemical industry has at its disposal sources such as plant-derived biomass, sequestered CO₂, and even end-of-use waste as alternative feedstocks to promote a circular economy. The chemical industry is already moving to renewable power such as solar and wind energy as well as renewable hydrogen to reduce its carbon footprint. However, major challenges remain in developing new chemistries and viable technologies for converting these alternative feedstocks to petrochemical-equivalent chemicals and fuels.

Biomass processing involves biological material originating from either terrestrial or marine sources including cellulose, hemicellulose, lignin, chitin, lipids, and polysaccharides. Global energy demand is expected to grow from approximately 600 quadrillion BTU (quads) per year in 2019 to 900 quads per year by 2050 (EIA, 2019). Currently, only a small fraction of energy is derived from biomass resources (EIA, 2020). However, energy and materials derived from biomass could increase significantly in the future. Projections indicate that up to a billion tons per year of crop residues, herbaceous energy crops, and woody crops and wastes are available in just the United States (DOE, 2016). Algae-based biomass could augment this feedstock, especially if cultivated with the help of concentrated CO₂ sources, such as those emitted from ethanol plants, coal-fired power plants, and natural gas–fired power plants.

Biomass resources are both physically and chemically different from common fossil fuel–based feedstocks such as crude oil and natural gas. Crude oil consists primarily of hydrocarbons ranging from light molecules to heavier ones. In petroleum refineries, the crude oil is first cracked to yield many fractions which are separated by distillation into various gas and liquid streams for further processing. In gas-processing plants, the various components of natural gas liquids are cryogenically separated. In sharp contrast, future biorefineries will rely on different processes, many yet to be developed, to convert solid and liquid biomass forms into useful chemicals. For example, fossil sources often require the addition of oxygen atoms to produce valuable feedstocks. This is done by selective oxidation of C–H and C–C bonds. In contrast, biomass is already oxygenated and hence is suitable for making chemical precursors without the addition of oxygen. However, to make hydrocarbon fuels, biomass often requires the addition of hydrogen to selectively remove the oxygen atoms. Mapping a transition for the existing chemical economy to evolve into a sustainable one is discussed in Sections 3.1–3.3.

The subject of biomass as a feedstock to produce chemical feedstocks has received increased R&D attention since the release of DOE’s report that identified the top value-added chemicals that can potentially be made from various fractions of biomass (Holladay et al., 2007). Several reviews have tracked progress in the development of new chemical pathways for converting biomass-based feedstocks into either petrochemical equivalents or new products with superior functional properties (Bender et al., 2018; Biddy et al., 2016; Chheda et al., 2007; Corma et al., 2007; Deuss et al., 2014; Fiorentino et al., 2017; Huber et al., 2005; Jing et al., 2020; Kunkes et al., 2008; Schutyser et al., 2018; Shanks and Keeling, 2017; Sun et al., 2018; Takkellapati et al., 2018).

As shown in Figure 3-6, carbon-rich biological material can be “refracted” into a variety of products through appropriate processing steps. For achieving circularity, the end-of-use products must be either recycled or reprocessed to make new products or returned to the biological cycles, such as soil nutrient recycling. Biomass feedstocks often require pretreatment to fractionate components such as cellulose, hemicellulose, lignin, chitin, and lipids. These fractions are then chemically converted into precursors for making fuels, chemicals, and materials. Implementation of practically viable biorefineries requires the development of (1) robust and reliable feedstock supply chains and (2) cascade processes that valorize the rich diversity of fractionated biomolecules into a diverse

product portfolio, from specialty bioactive compounds and multifunctional materials to platform chemicals and energy. To implement such a “no carbon left behind” vision (Figure 3-6), integrated green chemistry and engineering approaches are needed that valorize all fractionated biomass components through use of renewable energy, regenerable green solvents, and catalysts (Clarke et al., 2018).

Moving from fossil-derived carbon to renewable carbon as a feedstock for the industry will be a challenge. Because of the predicted volume needed, it will not be possible to supply the industry solely with carbon based on biomass and recycled waste streams. The shift to biomass will need to be sensitive to competition between land for food crops and for industrial feedstocks. One scenario modeled by the Nova Institute suggests that 25% of the feedstock base for the chemical industry will be based on CO₂ (Kähler et al., 2021). The report recognizes that the use of renewable and recycled feedstock does not guarantee sustainability. Environmental and health impacts that may result during their processing must be properly accounted for and mitigated. Estimating the carbon footprint is commonly practiced today (Ubando et al., 2020), and a similar analysis is needed for feedstocks such as plastic waste and CO₂ to assess the sustainability of these processes (see Section 3.4.1 for more details).

In addition to relying on biomass, plastic waste, and CO₂ feedstocks, the future chemical industry will also depend on a different network of processes and infrastructure than the existing ones. Even partially replacing traditional fossil fuel feedstocks with renewable sources and recycled carbon will require advances in catalysts, reactors, separations, and process intensification. The transition to new feedstocks will require new approaches and new chemistries, which will come from investments in fundamental chemical research. According to a recent report from the National Research Council,

Other emerging technologies, such as artificial intelligence and computational models, will also be essential in accelerating the pace of discovery (see Chapter 4 for more details).

3.4.3.2 Hydrogen

Hydrogen is gaining in importance as a CO₂-free energy system and therefore is a key substance for decarbonizing the energy and chemical sectors. On a weight basis, hydrogen (net calorific value of 33.3 kWh/kg) carries almost three times as much energy as gasoline. It can be burned either directly (producing water as a product) or converted into electricity in fuel cells (Bockris, 2013). The chemical industry alone is predicted to produce (and consume) more than 60 million tons of hydrogen each year (Holladay et al., 2009). Hydrogen is currently mainly produced from coal, oil, and natural gas. All of these processes produce CO₂ as a by-product. For example, 1 ton of hydrogen produced by methane reforming generates more than 10 tons of CO₂ (Dufour et al., 2009). CO₂-free hydrogen can be produced from electrolysis (“green” hydrogen) and stored for use as needed, thereby circumventing the intermittent nature of the outputs of photovoltaic plants or wind farms that are dependent on weather and the time of day.

However, hydrogen gas is highly explosive. For storage and transportation, it must be either cooled below –250°C to store it as a liquid or kept under very high pressure as a gas because of its low density. Both options require complex and costly infrastructure. Liquid organic hydrogen carrier technology offers a safe method for storing and transporting hydrogen (Preuster et al., 2017). Ammonia, made economically from green hydrogen, is also a promising candidate as a liquid hydrogen carrier (Wan et al., 2021). Ammonia can be readily decomposed to liberate hydrogen for use in fuel cells. It also has the added advantage of globally mature transportation and storage networks.

Hydrogen as a reagent will be especially important for processing emerging feedstocks such as CO₂ and biomass. The hydrogen produced by steam reforming of methane is termed “gray” hydrogen, which produces CO₂ as emissions. If carbon capture and storage (CCS) technologies are deployed to reduce these emissions, the hydrogen thus produced is termed “blue” hydrogen. However, a recent report suggested that the life-cycle GHG emissions of blue hydrogen could be quite high when the release of fugitive methane is taken into account. More detailed evaluations demonstrate the complexities in making these assessments and support the hypothesis that blue hydrogen can indeed be produced in a low-carbon fashion (Bauer et al., 2021). Other works have also highlighted the challenges associated with carbon accounting when considering methane and demonstrate the need for ongoing research in LCA and carbon accounting methodologies (Allen et al., 2021; Roman-White et al., 2021; Rosselot et al., 2021). In addition to the environmental impact, the financial costs of moving to hydrogen-based systems are unclear. It is widely acknowledged that the cost of hydrogen is falling, but the rate at which the price is falling, especially for greener forms of hydrogen, is unclear (DiChristopher, 2021). Some estimates already put fossil-based hydrogen below $2/kg, a cost goal set by recent U.S. legislation (see Section 3.3.4), but it is unclear how long it will take for greener forms of hydrogen to get to a similar cost (DiChristopher, 2021). Given the importance of hydrogen to the energy transition and decarbonization, other sources to obtain CO₂-free hydrogen, such as methane pyrolysis and light alkane dehydrogenation, will also continue to garner attention.

3.4.3.3 Carbon Capture Utilization and Storage

As the world seeks ways to decarbonize energy systems, a key technology for decreasing CO₂ emissions in the atmosphere will be CCUS. As described in the recent National Academies of Sciences, Engineering, and Medicine’s report, New Directions for Chemical Engineering, “Stopping the growth in concentration of atmospheric CO₂ does not require zero anthropogenic CO₂ emissions, but rather that anthropogenic CO₂ emissions are balanced by natural and anthropogenic CO₂ sinks, to achieve net-zero emissions” (NASEM, 2022a). CCUS is essential to achieve this goal because it has the potential to greatly reduce CO₂ emissions from hard-to-abate industries. The

International Energy Agency projects that CCS could mitigate up to 15% of global emissions by 2040 (IEA, 2020). In another recent National Academies’ report, Accelerating Decarbonization of the U.S. Energy System (NASEM, 2021b), CCUS is highlighted in the report’s recommendations, noting that the Departments of Transportation and Energy should plan and construct an interstate CO₂ transportation system to move captured CO₂ from sources to sites of storage and utilization. Figure 3-7 illustrates the flow of CO₂ in the CCUS schema. CCUS elements are briefly described below.

Carbon capture and storage.

CCS is a set of technologies that separate or “scrub” CO₂ from smokestack emissions or capture CO₂ from industrial process emissions, compress and transport the CO₂, and then pump it into geologic formations, typically 800–1,500 meters below ground or under the ocean. CCS technologies have been field tested and refined since 1972, but then and in many subsequent cases, the captured CO₂ has been used in a tertiary technology (enhanced oil recovery [EOR]) for extracting oil and gas from underground reserves. Although the captured CO₂is trapped underground, the extracted oil and gas ultimately generate CO₂ emissions through refining and use, and so this scenario is not carbon neutral. However, CO₂ storage facilities are being developed and brought online at an accelerated rate, including some that are not used for EOR. The Global CCS Institute has 135 facilities (operational and under construction) in its database as of 2021, and the U.S. National Energy Technology Laboratory notes that more than 200 CO₂ capture and storage operations are in place worldwide.¹⁷ The International Energy Agency lists 21 CCS facilities operating globally that have the capacity to capture 40 million tons of CO₂ annually (IEA, 2020). To achieve CCS at the gigaton scale necessary to aid in keeping global temperature rise below 1.5°C, hundreds of facilities, large and small, will need to be built globally. This will require large investments and extensive collaborations among chemists, chemical engineers, geochemists, geologists, policy makers, civic leaders, and politicians from local to federal. In a recent announcement, 14 petrochemical companies operating in Houston, Texas agreed to collaborate on the development of

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¹⁷ See https://www.netl.doe.gov/coal/carbon-storage/faqs/carbon-storage-faqs.

a very large CCS effort that, at full scale, could capture and store 100 million metric tons per year (ExxonMobil, 2022). In addition to an investment of ~$100 billion (Davis, 2021), the project will need policy and regulatory incentives and substantial scientific innovation.

Fundamental chemistry research can play an important role in CCS, especially in the area of CO₂ capture. Capturing CO₂ is most cost-effective at point sources where the concentration of CO₂ in a given waste stream is high, such as at large carbon-based energy facilities and industries with major CO₂ emissions. For example, the waste stream from ammonia manufacture is >98% CO₂ and that from cement, steel/iron, and glass production contains 20–35% CO₂ (NASEM, 2019c). The dominant CO₂ capture technology is absorption, or carbon scrubbing, with amines in solution, a process patented in 1930 to separate CO₂ from natural gas (Bottoms, 1930). Alkanolamine solutions are used most often, due to their high absorption capacity, low price, and favorable kinetics, among other reasons. However, they degrade in the presence of heat, CO₂, and O₂. In addition, as CCS expands to a wide variety of CO₂ emission sources, each with different concentrations of gas and varying amounts of contaminants, finding more efficient absorbents, including new generations of liquid and solid amines, is highly desirable. For example, metal-organic frameworks functionalized with tetraamines have been developed recently for use in conditions such as natural gas–fired power plant emissions, in which CO₂ concentration is only ~4% and is contaminated with high percentages of O₂ and H₂O (Kim et al., 2020). Other new materials being tested for CO₂ adsorption include water-lean solvents (Heldebrant et al., 2017), metal oxides (Wang et al., 2011), encapsulated liquid sorbents (Vericella et al., 2015), and porous solid adsorbents such as activated carbons, zeolites, metal-organic frameworks, and porous organic polymers (Creamer and Gao, 2016; Furukawa et al., 2013; Siegelman et al., 2021; Tian and Zhu, 2020).

Carbon utilization options.

In addition to sequestering captured CO₂, there are opportunities for captured CO₂ to be used in industrial process streams, either directly as CO₂ or after chemically transforming it to other molecules. The National Academies’ report Gaseous Carbon Waste Streams Utilization: Status and Research Needs (NASEM, 2019c) divides CO₂ utilization into three pathways: mineral carbonation, chemical conversion to produce fuels and chemicals, and biological conversion into fuels and chemicals; these are aligned with DOE’s Carbon Utilization Program (Figure 3-8). The 2016 CO₂ Sciences report uses similar categories when it identifies high-value markets for captured-CO₂ utilization. These include the cement, concrete, and aggregate industries, and the formation of commodity chemicals, specialty chemicals, polyols, polycarbonates, and fuels. While these markets have begun to be commercialized, there is room for significant growth that is dependent on, among other things, fundamental research in catalysis, reaction optimization, and separation technologies.

Using captured CO₂ in building materials.

Cement production accounts for 8% of global annual CO₂ emissions, releasing up to 0.95 ton of CO₂ per ton of cement produced (Bellona, 2015; Plaza et al., 2020). Approximately 65% of these emissions are process emissions (Figure 3-9), formed when limestone is thermally decomposed to calcium oxide and CO₂. The cement, concrete, and aggregate industries could noticeably reduce global CO₂ emissions, because these industries are significant emitters of CO₂ and are large global industries that are expected to continue to grow as development and population demands increase, and because the conversion of CO₂ into mineral carbonates is a thermodynamically favorable reaction. However, to achieve a net reduction in CO₂ emissions, more fundamental research is needed in LCA within these industries (Ravikumar et al., 2021). In Box 3-2, several companies are profiled that are using captured CO₂ and renewable energy to directly reduce or offset CO₂ emissions during the formation of cement, and via carbonation during the production of concrete and aggregate.

Converting CO₂ to chemicals and fuels.

After fossil fuels are combusted and release their energy, they produce lower-energy, fully oxidized carbon species in the form of CO₂. When considering CO₂ utilization pathways (Figure 3-10), it is possible to select applications where the

carbon can be utilized in its fully oxidized form. These pathways are less energy intensive, and as a result, nonreductive CO₂ utilization pathways tend to be further advanced commercially than those where the CO₂ needs to be reduced. The previous examples of using captured CO₂ in the cement and concrete industries are examples of nonreductive CO₂ utilization pathways (Grim et al., 2020).

Utilizing CO₂ to form organic molecules requires an input of energy, sometimes substantial amounts. As shown in Figure 3-11, many of the target product molecules are higher in energy and their carbon(s) is less oxidized than the carbon in CO₂; thus, converting CO₂ to many chemicals and fuels requires reducing its carbon oxidation state. CO₂ reduction can be done via addition of hydrogen and/or electrons through processes such as thermocatalytic, biological, or electrochemical transformations. Ultimately, for captured CO₂ to be the feedstock for the formation of chemicals and fuels without incurring a net emissions cost, the energy used to reduce the carbon in CO₂ has to come from zero-carbon or low-carbon sources, such as wind, solar, nuclear, or biomass. Likewise, when H₂ is used for carbon reduction, it needs to be derived from a low-carbon process or through water electrolysis.

For thermocatalytic transformations of CO₂, chemistries to create CO (Daza and Kuhn, 2016), methanol (Bowker, 2019), and methane (Frontera et al., 2017) are well established. Conversions of CO₂ to either methanol or CO are quite attractive, as they are useful intermediates to allow further upgrading to a range of products through well-known and optimized processes. Methanol can be used directly to form olefins, aromatics, and oxygenated products; used in fuel cells; or put into the fuel pool (Olah, 2005), making it a very flexible molecule. Future supply chain strategies built around methanol, known as “the Methanol Economy,” have long been proposed (Figure 3-12) (Olah, 2005). Likewise, conversion of CO₂ to CO makes it amenable to the entire range of syngas-based chemistries including Fischer-Trøpsch processes to make olefins, hydrocarbons, and fuels (Panzone et al., 2020). However, reducing CO₂ to methane requires shifting the carbon oxidation state from +4 to –4, which is a much more energy-intensive process than making methanol or CO from CO₂. Because the resultant methane is an energetic molecule, there are proposals to use the conversion of CO₂ to methane as a means to store excess renewable energy utilizing the current natural gas infrastructure (Schaaf et al., 2014).

Conversion of CO₂ to methane may have less utility than conversion to other chemicals, as there are currently fewer large-scale chemical processes based on methane as a feedstock outside of its reoxidation to syngas or its use for making hydrogen cyanide. However, researchers are exploring methane as a source of carbon for structured carbon materials such as graphite, carbon nanotubes, nanofibers, and nano-onion structures through catalyzed methane decomposition reactions. In these reactions, a low-carbon H₂ is also produced, adding to the utility of the approach. Unlike steam methane reforming, the carbon is not converted to CO₂, and therefore the H₂ that is produced is low carbon, even when made from conventional methane sources (Qian et al., 2020). CO₂-derived methane could be used for these syntheses, but will be more expensive and require more energy overall. There are also new routes for producing carbon nanostructures, utilizing molten salt electrochemical systems where the CO₂ capture, carbon reduction, and carbon nanostructure synthesis steps are combined. Many experimental factors can be used to tailor the final structures, and further research is needed before moving to the development phase (Yu et al., 2020).

While many of the thermocatalytic processes are somewhat mature, further research in their development is still needed. For example, hydrogenation of CO₂ to methanol generates a lot of water, which can lead to catalyst instability. Creating more hydrothermally stable methanol conversion catalysts remains an active area of research (Guil-López et al., 2019).

Biological processes to convert CO₂ are also showing significant progress. In addition to conversions of CO₂ via direct photosynthetic processes to generate biomass and/or crops, which can then be transformed into chemicals and fuels, efforts have been directed toward microbial syntheses using photosynthetic cyanobacteria or nonphotosynthetic chemolithotrophs. These microbial systems can be engineered to give a desired product slate (García-Granados et al., 2019), and a wide range of chemicals have been demonstrated (NASEM, 2019c). Currently, these gas fermentation routes are dominated by anaerobic processes. For example, LanzaTech has commercialized a 46-kiloton/year ethanol process with its proprietary acetogen, using steel mill waste gases as the carbon source. The LanzaTech technology utilizes a proprietary anaerobic acetogen, which is derived from a bacteria originally found in cat droppings. These bacteria produce ethanol from

CO-rich industrial gases (Daniell et al., 2012). The LanzaTech process can also make a variety of other chemical products. Through a combination of techniques including directed evolution and artificial intelligence, LanzaTech has demonstrated the possibility to form more than 50 different chemicals from industrial waste streams (Kobayashi-Solomon, 2021a,b,c). Most recently, researchers from LanzaTech, Northwestern University, and the Department of Energy’s Oak Ridge National Laboratory reported newly developed acetogen strains capable of producing acetone and isopropanol from industrial waste gases (Liew et al., 2022). The acetone and isopropanol processes are now ready for commercialization (Kobayashi-Solomon, 2021b).

Another approach to CO₂ conversion that has made significant progress is electrochemical conversion. There are two ways of classifying electrochemical processes involving CO₂: indirect and direct. For indirect processes, H₂ is generated via water electrolysis and then used to reduce CO₂ to useful products through a variety of chemical processes. When this methodology is used for generating fuels, the fuels are sometimes referred to as e-fuels because the H₂ is electrochemically produced even if the actual generation of the final product is via a non-electrochemical route. An oft-cited e-fuel example is Carbon Recycling International’s CO₂-to-methanol George Olah Facility (Burkart et al., 2019; NASEM, 2019c). Creation of hydrogen via water electrolysis is a commercial process and is the subject of ongoing research (Brauns and Turek, 2020; Shiva Kumar and Himabindu, 2019).

In direct electrochemical processes, CO₂ is directly reduced to yield products such as formic acid, CO, methane, ethane, and ethanol (Appel et al., 2013; Centi and Perathoner, 2009). In many cases, the direct route combines two steps into one where the hydrogen is generated in situ to generate the final product. These routes in turn can be broadly separated into two categories, low-temperature solvent processes and higher-temperature gaseous processes (Bonheure et al., 2021). The lower-temperature processes can utilize many of the same principles used in water electrolysis cell design, and several companies are commercializing technologies using these approaches. High-temperature electrolysis utilizes solid oxide electrolyzer cells (SOECs) to generate CO and syngas. The design of these systems is closely related to solid oxide fuel cell systems, which has aided in their development (Küngas, 2020). Although high-temperature electrolysis systems cannot directly synthesize other hydrocarbons and oxygenates from CO₂, they are being commercialized for the production of CO (Alcasabas et al., 2021). The efficiency and lifetime of SOECs will be improved through materials development and better understanding of nanoscale processes occurring in SOECs (Hauch et al., 2020).

While these commercial successes are encouraging, there is much more R&D to be done. A 2019 report from the National Academies recommends that “the U.S. government and the private sector should jointly implement a multifaceted, multiscale research agenda to create and improve technologies for waste gas utilization” (NASEM, 2019c). The report goes on to say, “Specifically the U.S. government and the private sector should support

• Research and development in carbon utilization technologies to develop pathways for making valuable products and to remove technical barriers to waste stream utilization;
• The development of new life-cycle assessment and technoeconomic tools and benchmark assessments that will enable consistent and transparent evaluation of carbon utilization technologies; and
• The development of enabling technologies and resources such as low- or zero-carbon hydrogen and electricity generation technologies to advance the development of carbon utilization technologies with a net life-cycle reduction of greenhouse gas emissions.” (NASEM, 2019c).

In addition to the sequestration of CO₂ in deep geological formations and its reuse into products, there are other strategies for capturing CO₂ in natural carbon sinks. These include afforestation and reforestation and sequestration on agricultural land and in coastal and pelagic ocean waters. These strategies are thoroughly presented in three recent reports (NASEM, 2019a,e, 2021a) and ongoing work from the National Academies.¹⁸

3.4.4 Chemical Research to Improve Quality of Life

3.4.4.1 Air Quality

In 2013, a detailed characterization study of trapped air in Greenland snowpack reported a surprising conclusion. Mapping of the samples showed that atmospheric CO levels in the Arctic steadily increased from the 1950s through the 1970s and then began dropping, ultimately resulting in levels lower than what were found for samples corresponding to the 1950s. Prevailing models did not predict there to be a reduction of atmospheric CO levels of this nature. The results were even more unexpected because these reductions were occurring simultaneously with increasing fossil fuel use over that same period. The authors credited improvements in emission control technologies and the introduction of catalytic converters in the United States and Europe for lowering CO levels (Petrenko et al., 2013). This trend mirrors measurements reported for CO by the EPA.¹⁹ Atmospheric levels for NO₂, SO₂, and particulates also showed significant declines since the 1980s and were all below established air standards (Figure 3-13). While a number of factors are undoubtedly responsible for the improved air quality, the introduction of catalytic convertor technologies plays a major role in these improvements (Farrauto et al., 2019).

Although emission control advances have significantly improved air quality, according to the WHO, air pollution caused an estimated 7 million deaths in 2016, with Africa and Southeast Asia being the most impacted by poor air quality (WHO, 2016). COVID-19 lockdowns provided direct evidence of the impact of many modern technologies on air quality (F. Liu et al., 2021) and highlighted the health benefits that reducing the dependence on fossil fuels could have if appropriately managed. However, some of the changes in air quality during the lockdowns did not fully follow the predicted behavior and demonstrated that this is an area where more basic research would be beneficial. For example, ground-level ozone in some locations rose because decreased urban NO₂ levels facilitated the production of ozone from free radical reactions with volatile organics (Bourzac, 2020). Projected climate change may make future air quality conditions worse, and thus there is a need to continue research in this topical area (Hong et al., 2019).

Even in a future when fossil energy is no longer used, there will be a need for emission control chemistry, though it will look different than the technologies of today. For example, if hydrogen combustion replaces fossil fuels, that will reduce CO₂, CO, and particulate emissions, but it could lead to increased NO_x emissions. These emissions of NO_x form because H₂ burns at a high temperature, and when done in the presence of air, a mixture of H₂, O₂, and N₂ all combust, which forms NO_x (Lewis, 2021). New energy technologies will create new problems to be solved. Solving them will require research in new areas of fundamental chemistry as well as building on what we know, such as our current knowledge of automotive and diesel emissions control (Lewis, 2021).

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¹⁸ See https://www.nationalacademies.org/our-work/carbon-utilization-infrastructure-markets-research-and-development.

¹⁹ See https://www.epa.gov/air-trends/carbon-monoxide-trends.

3.4.4.2 Water Safety

Without question, clean, safe drinking water is of the utmost importance to humanity, and chemistry has played a major role in ensuring that our water is safe to drink. There are three methods for disinfecting a water supply: ultraviolet treatment, ozonation, and chlorination. These treatments typically require significant infrastructure and are commonly deployed for population centers. Although most places with access to centralized treatment facilities have safe water, for some rural areas, particularly in geographic locations with fewer resources, access to potable water is quite limited (Figure 3-14). Developing treatment approaches for cost-effectively producing potable water at small scale is an area of need where fundamental research would have a significant global impact (Shinde and Apte, 2021).

Several new approaches are being explored, utilizing a combination of various chemical technologies such as electrochemistry, photochemistry, and nanomaterials (Amaro-Soriano et al., 2021; Bridle et al., 2015; Hand and Cusick, 2021). Novel materials and catalysts are also being probed to understand their efficacy and offer new avenues for materials development overall (Nasrollahzadeh et al., 2021). For example, the high biocidal activity, normally low human toxicity, and tunability of carbon nanomaterials have encouraged a number of research teams to start exploring how to employ them alone or in combination with approaches such as photochemistry as novel water disinfectant methods (Wang et al., 2019).

Understanding the chemical interactions of water treatment methodologies with a range of chemical contaminants in water supplies is another rich area of research. While chlorination is used widely as a water treatment strategy, due in part to its broad ability to destroy pathogens, chlorine’s strong oxidizing power and ability to directly halogenate other chemical molecules lead to a range of chemical transformations of other species present in a water supply. This can result in harmful by-products that are genotoxic, carcinogenic, and mutagenic. Several factors affect the formation of these harmful by-products, including pH, natural organic matter, ions, and the pipe material. A variety of chemical techniques have been applied to evaluate methods for eliminating pathogens while minimizing harmful disinfection by-products (Kali et al., 2021). Because new chemicals—related to the production and disposal of consumer products, agrichemicals, and pharmaceuticals—continue to enter our water supplies, studying these moieties under a range of chemical conditions and mapping their interactions will need to be an ongoing effort that requires buy-in from a number of different stakeholders and includes corporate responsibility and government oversight. This is an area of impactful science requiring new sampling, separation, and analytical techniques (Richardson and Ternes, 2014).

As our toxicological understanding advances, the need to develop faster and more sensitive detection capabilities continues to grow. These improved capabilities have identified previously unknown disinfection by-products, which in turn has led to safer drinking water supplies (Wawryk et al., 2021). Once advanced detection methodologies are adopted at water treatment facilities, opportunities to embed artificial intelligence and machine learning to provide better process control will engender other areas of research (Li et al., 2021).

3.4.4.3 Food Safety

A 2020 report from the Food and Agriculture Organization of the United Nations highlights how truly global the food supply has become. Their work estimates that about one-third of all agriculture and food exports are traded globally, crossing borders at least twice (FAO, 2020). While global food chains have increased access to a wide range of food choices for consumers, reducing seasonal changes in availability, they have also added complexity when tracking and tracing the source of the food. For

example, the 10 salad ingredients in Figure 3-15 originate from more than 37 countries. Global food chains greatly increase the possibility of food contamination and spoilage (IOM, 2012). Application of machine learning and related techniques in the service of food safety is a rapidly developing area, which will continue to be important (Deng et al., 2021). While there is no evidence of a link between SARS-CoV-2 infections and food ingestion, concerns around COVID-19 and the subsequent supply-chain disruptions have heightened interest in advancing food security monitoring, pathogen detection, and food safety–related applications. This will open a range of new avenues of scientific exploration (Lacombe et al., 2021).

Advances in analytical methods have led to significant improvements in the overall safety of the food supply, because these methods permit detection and monitoring of a wider range of potential contaminants and with increased sensitivity. Because of the variety of potential contaminants of concern, both traditional techniques of detection and new approaches are being explored.^20,21 Novel materials, such as magnetic nanoparticles (Yu et al., 2022) and metal-organic frameworks (Zhang et al., 2021) are being developed to help detect species of concern. This research space will be a rich area for further exploration for many years to come.

Food safety issues can also be created during routine food preparation. The application of advanced analytical approaches combined with chemical experimental probes has led to a detailed mechanistic understanding of reactions that can create potentially hazardous compounds during food processing and storage (Jackson, 2009). An example is our improved understanding of factors controlling formation of acrylamide, which the IARC classifies as a potential human carcinogen

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²⁰ See https://www.fda.gov/food/science-research-food/laboratory-methods-food.

²¹ See https://www.fda.gov/food/laboratory-methods-food/other-analytical-methods-interest-foods-program.

(Krishnakumar and Visvanathan, 2014). As new food types such as meat substitutes are added to the food supply, there will be even more need for these kinds of studies to build on fundamental knowledge required to ensure food safety (Sun et al., 2021).

Similarly, fundamental chemistry has led to improvements in food preservatives (Carocho et al., 2018) and packaging materials. Climate change could increase food spoilage rates and will require a multidisciplinary approach to ensure the long-term security of food supplies (Misiou and Koutsoumanis, 2021). Food spoilage and waste is already an area of great concern due to both its GHG impact as well as the financial cost to society. As much as 6% of global CO₂ emissions are linked to food waste (Our World in Data, 2020). This estimate includes both the fossil energy used throughout the food’s lifetime and any emissions related to its decomposition. The EPA estimates that about 40% of food is lost or wasted, costing the United States about $218 billion/year, which is approximately 1.3% of the GDP. Food waste makes up approximately 24% of solid waste entering U.S. landfills and is estimated to be the third-largest U.S. source of methane associated with humans (EPA, 2021). Thus, this is an important area of focus and presents an opportunity for chemical sciences to have broader impact.

While the carbon and physical footprint of food packaging is a concern, such packaging plays a significant role in protecting food from contamination and spoilage as well as offering convenience to the consumer. Because of the range of food types and ingredients and the types of packaging materials and their composition, understanding potential interactions that might occur at or near packaging–food interfaces is a complex area of exploration. Migration of compounds within the packaging material to the food can result in contamination that causes potential safety and quality concerns, which are further impacted by storage conditions. However, such transference can also be beneficial and form the basis of many active packaging concepts (Alamri et al., 2021). There are also concerns that exist along the entire end-to-end supply chain related to food packaging, detection of spoiled food at retailers, and many other issues that can occur over the extended lifetime of food products (Chen et al., 2020). Thus, there is a complex interplay of factors to map out in this space. A particularly active area of research is in the development of sensor technologies that can be combined with active packaging concepts to offer the potential to improve food quality, safety, and shelf life (Han et al., 2018). Understanding how to co-design functionality of the packaging with improved recyclability will be a rich area of research for the foreseeable future (Bauer et al., 2021; López de Dicastillo et al., 2020). Similarly, detailed attention to potential safety issues arising from contaminants in recycled materials will spawn research needs in packaging design, recycling process technology, and plastic additives (Geueke et al., 2018)

3.5 CONCLUSIONS

Fundamental chemical research has historically led to significant advancements that improved quality of life for billions of people. These benefits have sometimes been accompanied by unintended adverse consequences. To sustainably meet the needs of society moving forward, the chemical economy faces both challenges and opportunities for innovation. To meet the challenges and to take full advantage of the opportunities, the chemical economy needs to dramatically rethink its approach to production and consumption. Unfortunately, markets and public policies have yet to fully reward sustainability and climate protection in ways that enhance profitability and incentivize companies to invest in a shift to sustainability. Notably, some companies that have embraced green chemistry and circular economy principles have become more competitive or, at least, remained competitive. With these factors in mind, the committee arrived at a number of general conclusions for this chapter.

Conclusion 3-1: To implement a circular economy, the future will require a paradigm shift in the way products are designed, manufactured, and used, and how the waste products are collected and reused. These new processes, and the use of clean energy and new feedstocks to enable these processes, will require novel chemistries, tools, and new fundamental research at every stage of design.

Conclusion 3-2: Transitioning the chemical economy into a new paradigm around sustainable manufacturing, in which environmental sustainability is balanced with the need for products that will improve quality of life, enhance security, and increase U.S. competitiveness, will require substantial investment and innovation from industry, government, and their academic partners to create and implement new chemical processes and practices.

Conclusion 3-3: As fundamental chemical research continues to evolve, the next generation of research directions will prioritize the future of environmental sustainability and new energy technologies. Keeping sustainability principles in mind during every stage of research and development will be critical to accomplishing this goal.

Conclusion 3-4: Chemical research will have the greatest impact addressing energy and environmental sustainability if researchers and practitioners develop and use tools to quantify and mitigate environmental and human health impacts of new discoveries and are aware of the societal implications of their work, and if the research is driven by policies that identify specific environmental sustainability outcomes.

In addition to these conclusions, the committee noted the importance of fundamental chemical research in addressing key steps in decarbonization. As the chemical enterprise continues to look for areas where chemical research could make the largest impact in sustainability, there are a number of concrete areas where initial steps have already been made, and further advancement is possible. The areas that are prime for chemical innovation include

• better measurements for life-cycle assessments;
• enhancement of recycling technologies and co-design of plastic products for recyclability;
• sustainable syntheses;
• sustainable feedstocks and energy sources;
• carbon capture, utilization, and storage;
• monitoring and improving air quality;
• monitoring and improving water safety; and
• monitoring and improving food safety;

Conclusion 3-5: As the world moves deeper into its current energy transition—including the switch to electric vehicles, the implementation of clean energy alternatives, and the use of new feedstock sources—coupled with an increasing focus on circularity, the committee expects that decarbonization, computation, measurement, and automation will significantly alter the operations and processes of current industries, creating new opportunities and challenges that will benefit from fundamental chemistry and chemical engineering advances.

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