Sustainable Development of Algal Biofuels in the United States (2012) / Chapter Skim
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4 Natural Resource Use
4 Natural Resource Use
Pages 99-138
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From page 99... ...
Although production of algal biofuels is technically feasible, they have to be shown to be economically, environmentally, and socially sustainable to become a practical substitution for petroleum-based fuels. The scaling of the pathways for algal biofuel production that are deemed practical for commercial production poses a new demand on natural resources.
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From page 100... ...
. Where relevant data are available, quantitative case studies for at least two potential pathways for algal biofuel production are presented in this Chapter.
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From page 101... ...
This section discusses water requirement and consumptive use of fresh water along different steps of the algal biofuel supply chain and throughout the life cycle of algal biofuel production. In this report, water requirement refers to the quantity of water needed throughout the life cycle of algal biofuel production.
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From page 102... ...
The use of inland saline water in algal biofuel production also could have other potential environmental effects (see Chapter 5)
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From page 103... ...
(2010) analyze life-cycle water requirements of a number of alternative transportation fuels, including corn-grain and switchgrass ethanol, soybean biodiesel, solar and wind generated electricity, and algal biofuels with algae cultivation in open-pond systems and closed photobioreactors.
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From page 104... ...
They did not include water use upstream of algae cultivation (for example, water use for fertilizer production) , but that amount is a small fraction of the total water requirement (Harto et al., 2010)
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(2011) also constructed scenarios that build out the geographical distribution of algal biofuel production, starting with areas with lower evaporation and more rainfall.
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From page 106... ...
(2011) discussed the potential benefits and limitations of using wastewater to produce algae for biofuels cost effectively, and concluded that dual-use microalgae cultivation for wastewater treatment and biofuel production has the potential to use up nutrients in wastewater and reduce the amount of fresh water required for biofuel generation from algal biomass.
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From page 107... ...
. If they limit the algae cultivation to areas with high rainfall, such as areas near the Gulf Coast, the Great Lakes, and most of the eastern seaboard, then consumptive use of fresh water per unit fuel produced can be reduced by 75 percent.
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(2011) suggested that the irrigation water from other agricultural applications will need to be diverted to algal biofuel production if 10 billion gallons of fuels are to be produced from algae cultivated in fresh water.
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From page 109... ...
Indicators of sustainability of freshwater requirements for algal biofuel production include the following (Mulder et al., 2010; GBEP, 2011) : · Consumptive freshwater use expressed as kilograms of water per kilogram of fuel produced (biodiesel or ethanol)
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From page 110... ...
Therefore, water recycling and use of nonfreshwater resources are important to ensuring the social acceptability of the large water requirements for algal biofuel production. 4.2 NUTRIENTS Algae require key elemental nutrients for metabolic maintenance and growth, as is true of terrestrial plants.
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From page 111... ...
The extent and efficiency of nutrient recycling that is used in the post-cultivation processing of algal biomass into biofuels and coproducts will affect the net nitrogen and phosphorus requirements of biofuel production systems. Nutrients cannot be recycled 100 percent because of losses as a result of precipitation1 and nutrients tied up in dead algal biomass.
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From page 112... ...
. 4.2.1 Estimated Nutrient Requirements 4.2.1.1 Carbon Dioxide The estimated CO2 requirements for algal biofuel production are substantial.
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, 90 percent to 150 percent of all CO2 emission sources would be needed to produce 10 billion gallons of algal oil. They concluded that only a small number of stationary emission sources would be within a reasonably affordable access range in regions of the United States that are best suited for large-scale algal biomass cultivation, unless a costly infrastructure for CO2 capture and pipelining is in place.
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From page 114... ...
Note: The table shows the four different levels of algal biofuel production (10, 20, 50, and 100 billion gallons per year; 37.8, 75.7, 189, and 379.5 billion liters per year (BLY) , respectively)
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. 4.2.3 Opportunities for Mitigation Recycling of spent growth medium and of the residual nitrogen and phosphorus that remain in post-process algal biomass residuals will be essential for the sustainable production of algal biofuels.
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Similarly, R&D is needed to incorporate nutrient recycling into algal biofuel production systems. The potential for combining the use of wastewater in algae cultivation and the production of a fertilizer coproduct is worth further investigation.
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4.3 LAND A major constraint on the future expansion of biofuel production is likely to be the limited amount of land suitable for producing bioenergy crops and for expanding related refinery and transportation infrastructure (Cai et al., 2011)
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would have to be matched carefully to the cultivation systems used for algal biofuel production if the essential requirements for successful large-scale algal biomass production (suitable land and climate, sustainable water supplies, and sustainable nutrient supplies) are to be aligned in terms of their geographical location (DOE, 2010b)
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; (b) Annual average solar radiation (units)
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FIGURE 4-6 Mean annual lake evaporation in the continental United States. SOURCE: Hanson (1991)
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(2010) stressed that siting biofuel production systems close to water and nutrient resources would place additional limits on algal biofuels' contributions to future liquid transportation markets.
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4.3.2 Estimated Land Requirements Algal biomass production potentially requires much less land area than terrestrial biofuel feedstock cultivation. The land requirements for algal biofuel production are potentially 1-2 orders of magnitude lower than any crop-based biofuel, whether based on volumetric yield or energy yield per unit area (Table 4-5; see also Table 1 in Singh et al., 2011)
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From page 123... ...
They concluded that the Southwestern and the Nineteen Lower-Tier State regions in the United States potentially were more likely to meet the siting requirements for algal biofuel production scale-up than the Midwestern and Southeastern regions. However, the total land area required to meet targeted biofuel production levels is expected to be inversely correlated with the annual biomass productivity and algal lipid contents that actually can be achieved in practice (see Figure 2 in Pate et al., 2011)
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From page 124... ...
The related topics of impacts of land use and how to mitigate those effects are discussed in Chapter 5. 4.3.4 Sustainability Indicators Indicators of sustainability of land requirements for algal biofuel production include the following: · Liters of fuel produced per hectare.
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-based analysis of algal biofuel production in California. Continued efforts to perform meta-analyses of existing LCAs are desirable to comprehensively assess the land requirements and the most likely site locations for future algal biofuel production.
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Nonetheless, there is a great deal of recent research activity to assess life-cycle energy use of algal biofuel production. Table 4-6 shows the energy return on investment (EROI)
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(2010) Industrial CO2 Alum flocculation, - Algal biomass 1.06 centrifuge Clarens et al.
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. 4.4.2 Energy Requirements in the Supply Chain and Credits for Coproducts Analyses of prior studies provide insight into the current understanding of what production stages are important contributors to energy requirements despite the large uncertainties and variability associated with energy requirements of algal biofuel production.
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From page 129... ...
The treatment of the energy credits for coproducts is critical in the energy balance of algal biofuels. For production of bio-electricity, the energy credit per megajoule of biodiesel ranges from 0.3-1.3 megajoule/megajoules biodiesel (Lardon et al., 2009; Stephenson et al., 2010; Campbell et al., 2011)
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From page 130... ...
Given the importance of coproducts in the net energy balance, developing higher "energy value" coproducts could be an important mitigation strategy. 4.4.5 Sustainability Indicators A number of different metrics are already in use to assess energy systems (Farrell et al., 2006; GBEP, 2011; Baral et al., 2012)
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From page 131... ...
Increased data availability from laboratory and pilot scales is critical to calibrate and validate the forecasting methods that emerge. 4.5 CONCLUSIONS A review of published literature suggests that the scale-up of algal biofuel production to yield 37.8 billion liters of algal oil (10 billion gallons)
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From page 132... ...
Although several studies assessed land, water, and nutrient requirements and energy balance of algal biofuel production, few studies considered all four requirements simultaneously. A national assessment of land requirements for algae cultivation that takes into account climatic conditions; fresh water, inland and coastal saline water, and wastewater resources; sources of CO2; and land prices is needed to inform the potential amount of algal biofuels that could be produced economically in the United States.
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From page 133... ...
·Recycling of nutrients in algal biofuel pathways that require harvesting unless coproducts that meet an equivalent nutrient need are produced. A national assessment of land requirements for algae cultivation that takes into ac count climatic conditions; fresh water, inland and coastal saline water, and wastewater resources; sources of CO2; and land prices is needed to inform the potential amount of algal biofuels that could be produced economically in the United States.
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2011. Algal biofuels from wastewater treatment high rate algal ponds.
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Sponsor Perspectives for NRC Study on Algae Biofuels Sustainability. Presentation to the NRC Committee on Sustainable Development of Algal Biofuels on March 17.
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2011. The potential of sustainable algal biofuel production using wastewater resources.
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2005. Isolation and determination of cultural characteristics of a new highly CO2 tolerant fresh water microalgae.
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