The recent virtual symposium hosted in the US by CAAFI, the Commercial Aviation Alternative Fuels Initiative, illustrated the increasing momentum in sustainable aviation fuel (SAF) commercial development, with companies at different stages of development outlining ambitious plans for multiple facilities over the coming years. Many facilities are already under construction or nearing completion, and the increased availability of SAF is expected to become a reality over the next few years. Significantly, many producers are pursuing net zero SAF from initial construction by integrating technologies such as renewable energy, green hydrogen and carbon capture and storage into their fuel production strategy, reports Susan van Dyk. By incorporating net zero targets as part of the initial engineering design of a facility, any SAF pathway can potentially be net zero if the right policies are in place to incentivise the greatest emission reductions.
Gevo’s first fully net zero project is planned for its Lake Preston, South Dakota, facility and across its entire feedstock supply chain, CEO Pat Gruber told the symposium. Onsite electricity used in the facility will be derived from biogas, offsite electricity from wind turbines and renewable hydrogen. As Gevo uses corn for the production of isobutanol, the feedstock supply chain is addressed explicitly through better agricultural practices and land management, improved tillage practices and sustainable fertiliser. Gevo works closely with farmers and plans to reward them according to the sustainability of their corn, according to Gruber. Adds the company: “Gevo designs our entire business with carbon value in mind from the beginning, and carbon value has an impact on everything we do. By focusing on carbon value, Gevo is set up to maximise the value of renewable energy sources. When we aim towards that goal, everything we do in developing our plans, building our facilities, working with airlines, fuel companies, farmers and other partners, becomes focused on sustainability.”
Other companies pursuing a holistic approach to net zero SAF are Velocys, Aemetis, Red Rock Biofuels, and SkyNRG Americas. The Velocys Bayou Fuels project, according to Jeff McDaniel, VP New Projects, can achieve a negative -144 gCO2/MJ carbon intensity based on the production of the facility’s electricity with solar power and further use of carbon capture and sequestration for emissions from the facility, to achieve a significant reduction in carbon intensity.
Eric McAfee, CEO of Aemetis, told the CAAFI symposium the company’s strategy for net-zero includes renewable natural gas, cellulosic hydrogen, and carbon capture and storage. The proposed facility of SkyNRG Americas aims for maximum emission reductions by producing hydrogen from electrolysis, stated CEO John Plaza, while Red Rock Biofuels is implementing engineering changes to its Lakeview facility to lower the carbon intensity of the fuels. According to CEO Terry Kulesa, the Lakeview facility will use solar power for electricity and undertake carbon capture of any emissions.
The ability of SAF to reduce emissions, reflected in the carbon intensity (CI) of the specific fuel, is a central characteristic of its environmental benefits and sustainability, and based on a life cycle assessment across the entire supply chain of the fuel production process. Under CORSIA, eligible fuels are given default CI values, termed life cycle emission factors (LSf), based on the type of technology and feedstock used, although CORSIA provides a methodology to determine the unique LSf of a SAF pathway. The default LSf under CORSIA for isobutanol-to-jet based on a corn feedstock (similar to the Gevo pathway), is 77 gCO2eq/MJ compared to conventional jet fuel of 89 gCO2eq/MJ. However, the actual calculated value for Gevo fuel is -5 gCO2/MJ, according to Gruber.
If any type of SAF can deliver net zero, all technologies can potentially be used to meet net zero targets for the aviation sector to 2050. Proponents of synthetic e-fuels, such as Andrew Murphy from Transport and Environment, argue that power-to-liquid (PtL) fuels should be the main SAF technology in the long term as it is the only pathway that can achieve net zero. In contrast, Andreea Moyes, Global Aviation Sustainability Director at BP in a presentation at the CAAFI Symposium, argues “multiple SAF pathways are required, and all should be allowed to compete on their own merits within societal preference.” According to Moyes, the GHG profile of SAF, rather than the volume, should be the focus.
An important driver for aggressive targeting of maximum emissions reductions is placing a value on carbon. This type of policy is already in action in California’s Low Carbon Fuel Standard and has created a strong incentive for low carbon intensity fuels. The proposed Sustainable Skies Act, recently introduced in the US House of Representatives by Congressman Brad Schneider, creates exactly this type of policy in the aviation sector (see article). The Act proposes a blenders tax credit of $1.50 per gallon of SAF that provides a 50% reduction in emissions. SAF that provides greater emission reductions can earn an additional credit of $0.01 per gallon for each percentage the fuel reduces emissions over 50% up to a maximum of $2 per gallon for a 100% reduction, in order to incentivise greater reductions in emissions.
In contrast, the European ReFuelEU Aviation policy proposes a volumetric blending mandate which is not directly linked to emission reductions (see article). Although this will create a strong demand signal, it seems unlikely to drive aggressive carbon reductions of SAFs. Bryan Stonehouse, General Manager Aviation Sustainability & Risk at Shell Aviation, speaking at the recent IATA SAF Symposium, explained the role of policy for driving investment in SAF and contrasted the blenders tax credit with the ReFuelEU mandate. According to Stonehouse, the mandate is important for creating a demand but does not give the whole picture. The blenders tax credit will be the carrot for the industry, he said. According to Stonehouse, SAF is incredibly expensive and needs affordability support and argued the SAF industry needs aspects of both the ReFuelEU and the US blenders tax credit for development and scale-up.
While carbon intensity is only one component of sustainability, achieving net zero carbon intensities of SAF pathways should be a critical focus in the sector. Several US companies are engineering new facilities with a goal of achieving net-zero carbon intensity of fuels, and this seems to be driven by policies in the US that incentivise greater reductions. Designing and engineering a facility from the get-go to produce net zero fuels makes sense, and the right policies are crucial at this critical stage of investment and scale-up. While multiple policies are needed, rewarding carbon intensity reductions should play a central role in policymaking.
Photo courtesy of Alaska Airlines and Gevo