Estimating induced land use change emissions for sustainable aviation biofuel pathways

Sustainable aviation fuels (SAFs) are expected to play an essential role in achieving the aviation industries' goal of carbon-neutral growth. However, producing biomass-based SAFsmay induce changes in global land use and the associated carbon stock. The induced land use change (ILUC) emissions, as a part of the full life-cycle emissions for SAF pathways, will affect whether and to what extent SAFs reduce emissions compared with petroleum-based jet fuels. Here, we estimate the ILUC emission intensity for seventeen SAF pathways considered by the International Civil Aviation Organization (ICAO), covering five ASTM-certified technologies, nine biomass-based feedstocks, and four geographical regions. We introduce the SAF pathways into a well-established computable general equilibrium (CGE) model, GTAP- BIO, and its coupled emission accounting model, AEZ- EF, to study economy-wide implications of SAF production and estimate ILUC emissions intensity for each pathway. The estimated SAF ILUC emission intensities, using a 25-year amortization period, range from -58.5 g CO(2)e MJ(-1) for the USA miscanthus alcohol (isobutanol)-to-jet (ATJ) pathway to 34.6 g CO(2)e MJ(-1) for the Malaysia & Indonesia palm oil Hydrotreated Esters of Fatty Acids (HEFA) pathway. Notably, the vegetable oil pathways tend to have higher ILUC emission intensities due to their linkage to palm expansion and peatland oxidation in Southeast Asia. The cellulosic pathways studied provide negative ILUC emissions, mainly driven by the high carbon sequestrations in crop biomass and soil. Using the core life-cycle emissions established by ICAO, we show that fifteen of the assessed pathways have a lower full life-cycle emission intensity than petroleum-based jet fuels (89 g CO(2)e MJ(-1)), offering promising options to reduce aviation emissions. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

The study estimated ILUC emission intensities for 17 SAF pathways, finding that vegetable oil pathways tend to have higher emissions while cellulosic pathways provide negative ILUC emissions. Most of the assessed pathways have lower full life-cycle emission intensities than petroleum-based jet fuels, offering promising options to reduce aviation emissions.