A research project undertaken by the International Council on Clean Transportation (ICCT) has estimated that the US has enough feedstock capacity to comfortably reach a 2030 target on sustainable aviation fuel (SAF) but will fall woefully short of its 2050 goal.
A ‘grand challenge’ launched by Joe Biden’s government in late 2021 is intended to encourage production of 3 billion gallons of SAF by 2030, and then increasing production tenfold to 35 billion gallons over the next two decades.
However, the research suggests that the country only has feedstock capacity to produce 21.7 billion gallons of theoretical SAF production, but only 12.2 billion gallons would come from biomass sources deemed to be sustainable.
The report defined sustainable biomass as any feedstock “without adverse market and environmental consequences.”
Examining the 2030 target of 3 billion gallons through four low-risk to high-risk feedstock and technology scenarios, the report determined that under all four scenarios the target was feasible.
At the lowest risk end – where technology already exists and supply is already being produced – ICCT estimated that production is likely to reach just over 3 billion gallons by 2030.
Around 40% of that output would reflect waste-based hydroprocessed esters and fatty acids (HEFA) with the balance coming from second-generation cellulosic production that typically uses non-food parts of plants or municipal city waste.
A high-risk production scenario, using waste and crop-based HEFA, second generation cellulosic fuels and conventional alcohol-to-jet (AtJ) technologies could see production ramp up to just short of 7 billion gallons by 2030, according to the report.
However, the dramatic ramp up in mandates to 35 billion gallons would likely be out of the reach of all forms of US feedstocks and would fall significantly short of target when non-sustainable feedstocks are exclusively deployed.
“In total, we find that the United States has approximately 21.7 billion gallons of theoretical SAF production from available biomass, but only 12.2 billion gallons of that is from sustainably available biomass,” the report said.
The report also noted that the current tax incentives, also introduced by the Biden administration to encourage investment in SAF production, only run out to 2027.
“Without a long-term price signal, SAF developers will lack sufficient incentive to invest in projects from less-tested, advanced fuel pathways,” the report warned, concluding that technology delays will likely blunt early production potential.
Pathways reliant upon HEFA production – an advanced form of renewable diesel – will be highly resource constrained, while AtJ pathways are likely to be expensively prohibitive in the near term.
Available resources and sustainability
In feedstock terms, the two biggest available resources – corn grain and soybean oil – will both largely fall short of the threshold required to be deemed sustainable, with both failing to meet the 50% life cycle GHG reductions that are required under the main compliance scheme, CORSIA.
When pushing on from the 2030 target, the report calculated the biggest single contributor to the SAF production pool stood to be corn grain ethanol, with 43.9 million tonneds of feedstock likely to be able to deliver around 6.9 billion gallons of SAF, at a conversion factor of just under 50%.
However, that would equate to virtually the entire supply of US corn ethanol currently heading into the road fuel mix, while the second place feedstock – soy oil – likely to be able to contribute a maximum 15.3 million tonnes at a 100% crush rate
That would yield 2.67 billion gallons of SAF, but both would find it difficult to contribute under current GHG reduction compliance requirements.
Of the feedstocks that are deemed to be sustainable, agricultural residues could contribute 161.1 million tonnes of feedstock and 4.88 billion gallons of SAF, while next best option was energy crops, that could produce 2.72 billion gallons of SAF from 89.7 million tonnes of feedstock.
Animal fats were identified as the most productive feedstock, with 500,000 tonnes of feedstock resulting in 420 million gallons of SAF, followed by corn oil where 700,000 tonnes of feedstock could produce 370 million gallons.
“Approaching the long-term SAF target would require substantial diversion of feedstock from other economic sectors,” the report notes, and called for incentives to be “extended and expanded” post-2030.
“There is insufficient biomass to meet the long-term 2050 target… the current set of policies in place are insufficient to expand SAF deployment beyond 3 billion gallons,” the ICCT said.
The report tap into the mounting concerns around the ambitious SAF mandates that both the US and the European Union have set out as they attempt to decarbonise the hard-to-abate aviation section.
With other parts of the world also looking at their waste-based and vegetable oil feedstock slate, and competition for feedstocks intensifying, meeting these targets will require significant investment and securing of relevant feedstocks.
The EU is looking to ensure 70% of its entire aviation supply uses SAF by 2050, up from 0.03% as of 2020.
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