John Dees, PhD

Senior Decarbonization Scientist

A.J. Simon

Head of Industrial Decarbonization

Aviation plays a major role in today’s global economy, from critical services such as air freight and humanitarian relief to the recreation and tourism industries that are pillars of local economic prosperity. Despite a slowdown during the pandemic, demand for aviation has rebounded and is expected to grow considerably in the coming decade. Aviation accounts for 2.5% of global carbon dioxide emissions, and the costs and challenges of decarbonizing this critical service loom large for both airlines and consumers.

In the near term, the only scalable solution to decarbonize aviation is the use of sustainable aviation fuel. While in the longer term, the industry might transition to electric and hydrogen-fueled planes, these technologies are decades from full commercialization. Sustainable aviation fuel, or SAF, is considered a critical technology for reducing greenhouse gas emissions from aircraft and enabling the airline industry and its corporate customers to achieve their carbon-neutral targets.

There are some key barriers to scaling up sustainable aviation fuel, and today there is not nearly enough sustainable aviation fuel of sufficient quality and price to meet global demand. To answer the challenge of how to scale up high-quality, low-carbon sustainable aviation fuel, Carbon Direct partnered with Apple to explore the full range of fuel types, carbon intensities, market conditions, and potential costs across the entire landscape of sustainable aviation fuel. The analysis is part of Apple’s work to spur new solutions for addressing hard-to-avoid emissions using new technologies as the company prioritizes direct emissions reductions.

Today, we are excited to release a summary of our findings in the Sustainable Aviation Fuel Primer: Promising production pathways and opportunities to scale. Our goal was to find technologies and fuels that have the potential to deliver impactful volumes of sustainable aviation fuel at viable costs by 2030, while also cutting carbon emissions by over 70%. Our analysis compares 22 distinct production pathways on the basis of scalability, carbon intensity, and projected cost.


Our report finds that not all sustainable aviation fuel is created equal. Specifically, this report finds that pathways such as alcohol-to-jet (using current ethanol production capacity) and Fischer-Tropsch technologies (using waste woody biomass and agricultural residues) have the potential to be produced at quantities large enough to meet market demand.

Other pathways such as hydrotreated esters and fatty acids (HEFA) are likely to be constrained by the available supply of feedstocks and the environmental impacts of expanding that supply.

Sustainability and Carbon Intensity

The carbon intensity of any pathway largely depends on the environmental impact of feedstocks. While corn-based ethanol feedstocks have the potential to produce low-carbon fuels today, second-generation feedstocks including agricultural residues show promise for low-carbon, and potentially carbon-negative, aviation fuel at larger scale in the future.

We found that well-regulated carbon capture and storage (CCS) is a powerful lever to reduce carbon intensity across multiple sustainable aviation fuel production pathways. For example, carbon capture and storage can capture off-gases from both alcohol-to-jet and Fischer-Tropsch pathways, in some cases resulting in larger climate benefits than the initial switch from fossil to conventional biofuels.

Projected Cost

Our analysis confirms that subsidies are necessary for sustainable fuels to compete with current Jet-A prices. Encouragingly, in addition to existing incentives such as California’s low carbon fuel standard (LCFS), there are three new provisions in the Inflation Reduction Act that can substantially reduce the cost of sustainable aviation fuel to buyers. This legislation introduced changes to the tax code including the 40B SAF Blenders Credit; the 45Z Clean Fuel Production Credit; the 45Q Carbon Capture, Utilization, and Sequestration Credit; and the 45V Clean Hydrogen Production Credit—all of which are favorable to sustainable aviation fuel, and each with a different impact on the production pathways we assessed. These credits will alleviate cost increases that would otherwise constrain demand.

Read the full report: Sustainable Aviation Fuels Primer >