Toward Sustainable Aviation Fuels
Commercial aviation accounts for 2 percent of global carbon pollution, a figure projected to grow to between 3 and 4.7 percent by 2050 without concerted action to curb emissions. Accordingly, a comprehensive solution to the world’s climate predicament requires a strategy to reduce aviation’s carbon footprint. Industry leaders recognize this imperative and accordingly have set a goal of reducing the sector’s carbon emissions 50 percent by 2050.
Sustainable aviation fuels (SAF) are integral to that strategy. More efficient aircraft and engine design, streamlined flight operations, and improvements to air traffic management systems can slow the growth in aviation’s climate pollution, but it will take substituting fuels with a lower carbon footprint to actually reduce the industry’s greenhouse impact in coming decades. Because commercial planes have long useful lifetimes and new models have long design and production timelines, liquid hydrocarbon fuels that can be used in existing planes and fueling infrastructure—“drop-in biofuels”—are necessary.
Interest in SAF has accelerated in the past decade. Individual flights of commercial airliners powered by SAF began in 2008; in 2011, both Lufthansa and Alaska Airlines embarked on a series of flights using fuel made from plant and animal oils. These fuels must meet essential physical and performance specifications set by the engineering testing body American Society for Testing and Materials (ASTM). Three kinds of biofuel received this approval in 2009, 2011, and 2014, and three more varieties are on track to receive it in the coming year. The three approved varieties of SAF must be blended with fossil jet fuel in order to ensure that the fuel performs properly in flight, but other types would make it possible to fly using fuel derived entirely from biological materials. Research and development continues on promising new SAF production processes, using feedstocks such as industrial waste gases and brine-raised algae.
SAF development continues apace despite the slide in petroleum prices that began in 2014, although no SAF facilities operate yet at commercial scale. Major projects are underway in Oregon, California, Nevada, the US Midwest, and Britain to manufacture SAF from feedstocks as varied as vegetable oils, municipal solid waste, and forestry by-products. The pending approval of green diesel for blending into jet fuel at ratios of up to 10 percent will create an immediate opportunity for large-scale SAF use, since that fuel is already in commercial production for ground transport.
The lack of consistent and reliably supportive government policies has been the most significant factor holding back SAF growth. Clean fuels mandates at the state and federal level, as well as financing mechanisms that reduce the risks for SAF investors, and infrastructure projects to facilitate the introduction of SAF to the jet fuel supply would all accelerate the adoption of SAF.