Current Methods for Life-Cycle Analyses of Low-Carbon Transportation Fuels in the United States (2022) / Chapter Skim
Currently Skimming:
8 Aviation and Maritime Fuels
8 Aviation and Maritime Fuels
Pages 142-156
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 142... ...
Therefore, the term "sustainable aviation fuels" is not used in this report because it suggests an endorsement of the environmental benefits for all non-petroleum aviation fuels. For the purposes of evaluating the climate impacts of AAFs within fuels policies, this section discusses several key areas that may require special consideration beyond the approaches used for alternative fuels used in other sectors: (1)
|
From page 143... ...
TABLE 8-1 Summary of Approved and Pending Alternative Aviation Fuel Production Pathways Blend Fuel Level Typical Feedstocks Status Hydroprocessed esters and fatty acids synthetic 50% Vegetable oils; waste fats, oils and Approved in 2011 paraffinic kerosene (HEFA-SPK) greases Hydroprocessed fermented sugars to synthetic 10% Sugar crops Approved in 2014 isoparaffins (HFS-SIP)
|
From page 144... ...
Conventional jet Crude oil (average, ultra- low United States Process-based Primarily energy (2010) fuel, HEFA-SPK, sulfur, oil sands, oil shale)
|
From page 145... ...
In CORSIA, GHG emissions reductions may be generated by subtracting the life-cycle emissions for AAFs from the fossil fuel baseline, calculated as 89 gCO2e for jet fuel and 95 gCO2e/MJ for aviation gasoline. More information on the variation in upstream carbon intensity (CI)
|
From page 146... ...
CORSIA specifies two approaches for low LUC risk aviation fuel feedstock production: the Yield Increase Approach, and the Unused Land Approach. For the Unused Land Approach, CORSIA (ICAO 2019, 10-11)
|
From page 147... ...
(2021) parameterized the impact of low aromatic AAFs on contrail cirrus formation as a function of the square root of the fossil fuel share, implying that a 50 percent reduction of jet fuel aromatic content via AAF blending reduces contrail cirrus radiative forcing by about 30 percent.
|
From page 148... ...
The non-CO2 effects of aviation fuels raise several important questions for LCA of aviation fuels and in turn, for aviation fuel policy. Though existing LCAs of aviation fuels have generated a set of estimates for the emissions of conventional GHGs released from the well-to-wake production and use of aviation fuels, compared to the quantity of existing literature on the life-cycle GHG emissions for AAF production, the data are more sparse on the non-CO2 effects of AAFs.
|
From page 149... ...
It is challenging to present the non-CO2 impacts of aviation fuel combustion on a consistent basis alongside the climate impacts of the fuel cycle, largely due to the different time scales. The fuel cycle is dominated by CO2 emissions and thus is not sensitive to assumptions of time horizon; in contrast, the impact of non-CO2 emissions is much more sensitive to the assumptions of the time horizon and operating conditions (altitude and atmospheric conditions)
|
From page 150... ...
Conclusion 8-5: Though there is evidence that fuel blending can mitigate the impact of some non CO2 climate forcing; attributing these impacts to fuel switching in policies may result in inaccurate crediting of these fuels. Impacts of Alternative Aviation Fuels on Aircraft Efficiency Using alternative fuels or electrification technologies (e.g., batteries or fuel cells)
|
From page 151... ...
. In most cases, the fuel savings associated with a more energy-dense liquid fuel will be small because these fuels will be blended with conventional petroleum jet fuels.
|
From page 152... ...
For AAF production pathways that generate both an aviation and a road fuel co-product, maximizing the share of AAF output requires additional energy and may reduce overall biofuel yields, increasing emissions attributable to AAF production. Conclusion 8-7: There are some variations in the life-cycle emissions attributable to alternative aviation fuels at facilities for some fuel pathways, depending on whether they are configured to maximize alternative aviation fuel output or to maximize yields of other co-products, such as mid dle distillates.
|
From page 153... ...
In sum, future climate regulations from the International Maritime Organization may further influence the mix of fuels supplied to the marine sector. Sulfur regulations such as MARPOL Annex VI are already driving changes in the production and use of fuels in the marine sector, including in refineries that are experiencing increasing demand for very low sulfur fuel oil.
|
From page 154... ...
Recommendation 8-5: The baseline life-cycle GHG emissions for marine fuels should reflect cur rent industry trends stemming from MARPOL Annex VI and potentially be updated after several years' time once the industry adjusts more fully to the new regulations through, for example, de ployment of more liquefied natural gas-fueled vessels. Recommendation 8-6: Marine fuel pathways should be evaluated with methods that are consistent with on-road and aviation fuels while considering unique factors in the oil refining and use phase aspects of a marine fuel's life cycle.
|
From page 155... ...
2014. Life cycle greenhouse gas emissions of sugar cane renewable jet fuel.
|
From page 156... ...
2010. Life cycle greenhouse gas emissions from alternative jet fuels.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.