The Department of Energy’s “SAF Grand Challenge” to produce 3 billion gallons of sustainable aviation fuel (SAF) annually by 2030 seeks to decarbonize one of the hardest to decarbonize industries—aviation. A key component of this program provides producers a $1.25 per gallon tax credit for SAF that achieves a 50% carbon intensity reduction versus conventional jet fuel. Carbon intensity (CI) is a measure of greenhouse gases released per unit of energy; commonly expressed as grams of CO2 equivalent per megajoule (gCO2e/MJ). Meeting the 50% CI reduction threshold and obtaining the tax credit is key to the financial viability of potential SAF projects.
Mead & Hunt’s aviation and renewable energy groups are at the nexus of this carbon reduction story. We develop carbon reduction roadmaps, recommend emissions reduction strategies, and implement efficiency improvements for airports across the nation. We have also led research for the National Academy of Sciences to evaluate deploying carbon removal technologies at airports. In the renewable energy market, we have delivered dozens of design-build biofuel projects through our in-house engineering and construction teams. As a technology agnostic design-build firm, we work with many of the leading renewable energy technology providers and help bring their technological solutions to life through delivery of commercial scale facilities.
Sustainable Aviation Fuel Production Landscape
SAF production from the triglycerides found in soybean oil is well understood and not that different from renewable diesel production. While the majority of current U.S. SAF is produced from soybean oil triglycerides at large refineries, this SAF does not meet the 50% CI reduction required to be eligible for the tax credit. Used cooking oil and animal fats (e.g., rendering waste) are two alternative triglyceride sources that allow SAF produced at refineries to easily meet the CI reduction target. However, there is not an adequate supply of these feedstocks to meet current or future needs. Distillers corn oil, another alternative triglyceride and a byproduct of corn ethanol production, allows for a better SAF CI score but also lacks the abundance needed to meet SAF production targets.
The ethanol industry sees huge potential for corn ethanol “alcohol-to-jet fuel processes” to fill this gap.
With a shift to passenger vehicle electrification, demand for corn ethanol is expected to slump over the next 20 years. The resulting excess ethanol production capacity could easily be used to meet the demand for ethanol as an intermediate fuel in SAF production—if—ethanol facilities can lower the CI score of their product. The ethanol industry is keenly focused on lowering the CI score of ethanol so that it can become a desirable intermediate fuel in SAF production. The following pathways can contribute to lowering the CI score of corn ethanol:
- Carbon capture and sequestration (CCS) holds one significant key to lowering ethanol CI. Projects like the planned Navigator Heartland Greenway pipeline and Summit Carbon pipeline will transport captured CO2 from corn ethanol plants across the grain belt to geological sequestration injection wells in Illinois or North Dakota. When ethanol production CO2 is captured and sequestered, the CI of ethanol produced at that facility drops from 60 to 30, enabling SAF produced from that ethanol to be eligible for the $1.25/gallon tax credit needed for a financially viable SAF project. However, CCS projects face significant regulatory and permitting headwinds, which lead to the need for other more immediate methods for lowering an ethanol facility’s carbon intensity.
- Techniques like anaerobic digestion of stillage for biogas production, incorporating solar power, or installing combined heat and power engines all work to lower the CI score of a facility’s ethanol, and can be implemented more quickly than CCS. Ethanol’s value is tied to its carbon intensity, and projects like adding stillage anaerobic digestion can improve the carbon intensity enough to boost the sale price of ethanol by around $10,000,000 per year or more for an average-sized ethanol facility.
- Another approach for lowering the CI score of ethanol skips the corn kernel and instead produces ethanol from cellulosic biomass, such as corn stover or grasses. While cellulosic ethanol production has yet to be demonstrated as financially viable at full scale, several large entities, such as SAFFiRE Renewables, are committed to the technology. They are receiving large backings from the airline industry, implementing lessons learned, and have improved financial proformas due to SAF production tax credits.
Other SAF Pathways
There is the potential to convert biogas from a variety of sources into SAF through a modified Fischer-Tropsch synthesis reaction. The feedstock—ultra-low carbon intensity biogas—is generated through digestion of livestock manure, wastewater, and landfill gas. Additionally, gasification of municipal solid waste, or woody biomass, can allow for similar synthesis reactions to produce SAF, such as the systems operating at the Fulcrum Bioenergy facilities.
Another pathway converts municipal wastewater plant sludge through a hydrothermal liquefaction (HTL) process to create a biocrude that can be readily converted to SAF. A demonstration facility is currently under development by Metro Vancouver. As with several other potential biofuel feedstocks, scalability of HTL remains a challenge.
Meeting Future SAF Targets
The amount of new SAF production that needs to be brought online in the next six years is extraordinary. When accounting for the required 50% reduction in carbon intensity, it becomes clear that multiple new technologies and pathways need to be commercialized in the next couple of years to achieve these targets. The good news is that many of these technologies already exist and simply needed the right incentive structure to become financially viable. Plans for full-scale commercialization of many of these technologies are currently underway. Quickly expanding the adoption of the best technologies, and then increasingly building facilities around those processes, is essential to hit future SAF targets.
With a holistic view of this emerging biofuel industry, Mead & Hunt’s aviation and renewable energy teams are ideally positioned to help airports, technology providers, and project developers achieve their goals. Mead & Hunt will continue to assist our airport clients with decarbonization planning, SAF sourcing and uptake support, and integration of carbon removal efforts such as direct air capture (DAC). We help clients holistically weigh various reduction and removal efforts. The intersection of DAC and SAF pathways is central to scaling production of SAF and meeting the aviation industry’s net zero goal by 2050.
Meanwhile, Mead & Hunt’s design-build renewable energy group is prepared to assist technology providers in building commercial scale facilities. Our engineering team is ready to provide technology integration and balance of plant engineering. We develop accurate capital budgets and schedules for construction by engaging our preconstruction services team in the early stages of projects. When it’s time for construction, we oversee site safety, manage construction, and provide a system that meets your objectives. Our in-house controls group is involved every step of the way for smooth start-up and operations.
Mead & Hunt strongly believes SAF will have a positive impact on people, communities, and the planet. We are excited to help lower the carbon emissions of the aviation industry.