GREET underestimates indirect land use change, undermining the climate benefits of section 40B

The policy brief contends that the GREET model's outdated assumptions regarding land displacement and forest impacts lead to a significant underestimation of indirect land use change (ILUC) emissions for sustainable aviation fuel (SAF). This discrepancy allows high-emissions fuels, particularly land-intensive soy and corn biofuels, to qualify for the section 40B tax credit, which the author argues distorts the market against waste-based and synthetic SAF and contradicts congressional intent. The document advocates for updating GREET to a methodology similar to the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), which incorporates a broader range of ILUC values to better reflect global market impacts.

• The GREET model is not similar to the CORSIA methodology and underestimates indirect land use change (ILUC) emissions because it uses a less rigorous module with outdated assumptions about land displacement and the impact of crop production expansion on forest lands.
• Using GREET 2022 ILUC values creates a market distortion that favors low-cost, land-intensive conventional biofuels derived from corn and soy over synthetic SAF and waste-based fuels, while also reducing incentives for ethanol producers to implement carbon capture.
• A comparison of a soy-based SAF producer shows that using GREET 2022 results in a lifecycle emission total of 47.3g CO2e/MJ (a 50% reduction vs fossil jet fuel), whereas CORSIA's higher ILUC rate results in 64.3g CO2e/MJ (a 30% reduction), meaning the producer might qualify for the section 40B tax credit under GREET but not under CORSIA.

APA

Hunt, K. (2024). GREET underestimates indirect land use change, undermining the climate benefits of section 40B. Clean Air Task Force. https://www.catf.us/2024/04/greet-underestimates-indirect-land-use-change/

Chicago

Hunt, Kara. GREET underestimates indirect land use change, undermining the climate benefits of section 40B. Clean Air Task Force, 2024. https://www.catf.us/2024/04/greet-underestimates-indirect-land-use-change/.

Wikipedia

{{cite report |last1=Hunt |first1=Kara |title=GREET underestimates indirect land use change, undermining the climate benefits of section 40B |publisher=Clean Air Task Force |date=5 April 2024 |url=https://www.catf.us/2024/04/greet-underestimates-indirect-land-use-change/ |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{hunt2024greet, author = {Hunt, Kara}, title = {{GREET underestimates indirect land use change, undermining the climate benefits of section 40B}}, institution = {Clean Air Task Force}, year = {2024}, month = apr, url = {https://www.catf.us/2024/04/greet-underestimates-indirect-land-use-change/}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }