Unlocking Lead from U.S. Aviation Fuels
CONTRIBUTOR | By Brian Hall, former naval aviator and FAA certified commercial pilot – WEDNESDAY, AUGUST 9, 2023
Leaded gasoline was phased out of use in motor vehicles in the 70s and 80s due to the discovery of the extent of health problems caused by lead poisoning. However, it is still commonly used in aviation for aircraft using piston engines, which the Environmental Protection Agency acknowledges as a public health threat. The technology exists today to make lead-free aviation gasoline, known as avgas, without using fossil fuels. Why are we not doing it?
Leaded avgas has had deleterious impacts to the health of aviation workers, the broader U.S. public, and the environment. Efforts to move away from leaded avgas have been delayed due to the high cost of parts, old engine technology, and limited research and development funding.
Sustainable aviation fuels (SAF) are crucial in decarbonizing the aviation transportation sector. Moreover, biofuels are necessary to reduce the carbon impact of internal combustion legacy on-road vehicles as we transition to electric vehicles. The U.S. is a key player in producing SAF because of the existing and upgradable fuel infrastructure and feedstock production capacity. Support for the biofuel industry’s continued investment in aviation fuel is important for this transition. This can be accomplished through regulations that limit carbon emissions and production incentives that create good-paying jobs.
AIRCRAFT FUEL DEVELOPMENTS
One opportunity to promote biofuels for aviation fuel is through ongoing efforts to remove leaded additives from avgas. It is important to mention that SAF and avgas are different types of fuel used for separate applications. Avgas is used to power small piston-engine aircraft used by the non-commercial sector of aviation, known as general aviation. General aviation has a large piston-engine fleet of approximately 171 thousand aircraft that run on leaded avgas. However, the general aviation fleet consumes far less avgas than the commercial sector uses jet fuel. Despite that, piston-engine aircraft are the largest remaining source of airborne lead emissions.
Given the long-life cycles of aircraft in the general aviation sector (46.8 years), efforts should be directed towards decarbonizing avgas. Currently, there are no U.S. initiatives for low-carbon avgas production, making the reengineering of avgas a unique opportunity to eliminate lead, reduce carbon emissions, and incentivize biofuel production that can also be used for legacy passenger vehicles.
Promising but immature aircraft technologies such as electric, hybrid-electric, and hydrogen-powered aircraft are still developing but do not address the existing piston-engine fleet of aircraft. Consequently, there is a pressing need for drop-in fuels that are low carbon intensity and lead-free. Reformulated biofuel-based avgas is needed to decarbonize existing and future piston-engined aircraft that will fly for decades.
Consequently, avgas is a relatively small and niche fuel market that decarbonization efforts have largely ignored when compared to jet fuel and the implementation of SAF policies. Federal legislation and Federal Aviation Administration (FAA) initiatives have been drafted to ensure avgas is reformulated to meet the performance requirements of piston-engine aircraft without lead additives, but remain stalled without being implemented. The biofuel sector has the technology to meet the FAA requirements, and policy can help achieve that aim.
High octane fuels reduce engine knocking, a term for untimed gas combustion under heat and pressure. Engine knocking is unsafe for flying because it limits power and risks engine failure. Lead in fuel raises the octane rating, allowing for increased compression ratios and more horsepower for a given engine size. The general aviation industry has historically argued that there is a lack of viable high-octane alternatives for lead, but transitioning away from leaded avgas is achievable through existing octane-boosting technologies that can be produced in the U.S.
POLICY OPPORTUNITIES
There are currently two bills in Congress that promote the phasing out of leaded avgas: HR 3559 focuses on FAA research and development funding, and includes a roadmap requirement to develop safe, lead-free fuel for general aviation. It encourages collaboration with private industry to identify research programs, scale production and distribution, assess market viability, and incentivize adoption. The second bill, H.R.3935, is the larger FAA reauthorization and improvement bill. Within that bill, the FAA is required to safely eliminate leaded avgas for piston-engine aircraft while ensuring existing performance characteristics. Unfortunately, neither of these bills promote low-carbon solutions for biobased fuel or octane boosters–a missed opportunity for cleaner air transportation.
Additional federal programs have recently been implemented that promote the production of SAF. The Inflation Reduction Act (IRA) incentivizes SAF production by providing additional tax credits for SAF production in addition to low-carbon transportation fuels, it authorizes $500 million in grants to the FAA that support SAF infrastructure. Meanwhile, the Department of Energy (DOE) launched two initiatives to promote SAF production and deployment: the SAF Grand Challenge and the Clean Fuels and Products Shot programs; both programs focus on decarbonizing jet fuels and providing market signals for biofuels in the commercial aviation industry. Still, there are no specific considerations for the decarbonization of avgas for general aviation piston-engine applications.
Under the IRA tax incentives for SAF, avgas is ineligible because it does not meet the current definition of SAF, which only concerns turbine-powered (jet) engine fuels. However, under the 45Z credit for low-carbon transportation fuels, any low carbon transportation fuel produced and sold in the U.S. can receive up to $1.00 per gallon.This credit could create a significant incentive to help fund a low-carbon transition to lead-free avgas, however, it falls short of the SAF production maximum of $1.75 per gallon of renewable drop-in jet fuel.
The efforts to remove lead from avgas provide an opportunity to incentivize lower-carbon biofuels, which will continue the necessary progress to eliminate intractable emissions from the U.S. aviation sector. As such, policies in the form of incentives should be considered to increase the production of low-carbon fuel for piston-engine aircraft. Existing octane-boosting replacements for lead, such as ethanol, aromatics, and iso-octane, can all be synthesized from biobased feedstocks grown in the U.S. The technology exists today to make lead-free avgas without using fossil fuels.
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Brian Hall is a former officer and pilot in the U.S. Navy. He is a graduate student in global environmental policy at American University and a Clean Fuels Fellow at Boundary Stone Partners.