The US Energy Department has issued a plan to boost the production and use of sustainable aviation fuel (SAF), which the government said should be focused on commercially ready conversion technologies and feedstocks.
In the plan, dubbed the “SAF Grand Challenge Roadmap”, the US Department of Energy (DOE) lays out how the government and industry can achieve previously revealed SAF goals, which were originally signed in 2021 by the Biden administration.
The 2021 plan aimed to achieve a 50% reduction in life cycle greenhouse gas emissions compared with conventional fuel as well as produce three billion gallons of SAF per year by 2030 and ensure sufficient SAF supply to meet 100% of aviation fuel demand by 2050.
According to the government-wide roadmap, enough biomass can be collected sustainably each year in the US to produce 50–60 billion gallons of low-carbon fuels.
“Growing, sourcing, and producing SAF from renewable and waste resources can also create new economic opportunities in agricultural and rural communities, improve the environment, and even boost aircraft performance,” the DOE said late on Friday.
The DOE also highlighted the potential for existing biofuels within the SAF sphere “as ground transport electrifies.”
In terms of feedstock, the DOE argued that there is sufficient feedstock to meet the estimated demand of the US aviation industry “if cost, sustainability and production barriers can be addressed.”
The question of feedstock sustainability
Ensuring that the SAF used in aircraft is genuinely environmentally beneficial has long been cited as a major challenge for the aviation industry.
This is mainly because of potential shortages of feedstocks such as used cooking oil, which is also highly sought after by road transport and an expected uptake by the shipping industry – and a forecast surge in demand in the aviation sector.
In the shorter term, given that there is less than eight years to achieve 2030 goals laid out in 2021 and considering the lengthy timelines often associated with SAF infrastructure, the path to meeting the 2030 goals requires “an immediate focus” on already available technologies and feedstocks.
More specifically, the DOE highlighted lipid-based pathways (fats, oils, and greases) as the expected primary fuel pathway leading up to 2030, with a smaller contribution from waste, forest and agricultural residue, and alcohol pathways.
“A diverse array of lipids should be studied, including but not limited to oilseed crops (including soybean and canola), oilseed cover crops, food waste (used cooking oil/brown grease), distillers corn oil, and animal fat/tallow,” the DOE said.
The body added that greater use of “commodity vegetable oils”, including soybean and canola, could play a role in growing SAF volumes.
Legislation and tax credits
Biden officially signed the Inflation Reduction Act into law on August 16, which is slated to provide SAF credit incentives of $1.25-1.75/gallon in the years 2022-2024, with the payments calibrated to GHG savings of between 50%-100% compared with fossil kerosene.
That system will be replaced in 2025 by the Clean Fuel Producer tax credit, which will also apply to road-based biodiesel and SAF, which changes the tax credit formula, so it is pegged to the reduction beyond 50 kgCO2e/MMBtu (metric million British thermal units).
In effect, the CFP means feedstocks will need to deliver much higher GHG savings than in the 2022-2024 phase and would effectively exclude some feedstocks that have only scraped into the 50% GHG reduction cut requirement.
According to the DOE, aviation generates approximately 2% of US human-made carbon dioxide (CO2) emissions and contributes additional global warming impacts through high-altitude nitrogen oxide emissions and aviation-induced cloudiness.
The government body took the opportunity in its roadmap to highlight the difficulties associated with decarbonizing the aviation sector, which it said was largely down to the need for an energy-dense liquid fuel to power heavy and passenger/cargo laden aircraft that will travel at high speeds.
For this, the DOE added, energy sources other than liquid hydrocarbon jet fuels, such as battery technologies and hydrogen, “are not expected to contribute to substantially reducing aviation emissions until after 2050.
