Beyond Fats and Oils: Unlocking Biomass for the Next Generation of SAF

By Stephen Toon, CEO, BioVeritas
Special to The Digest

The Feedstock Dilemma at the Heart of SAF

After several decades working across industrial biotechnology, from greenfield plant startups to navigating more than a few cellulosic scale-up challenges, I’ve learned that the future of sustainable aviation fuel (SAF) hinges on something far more fundamental than technology: feedstock. For aviation, energy diversification is not only a sustainability goal; it is essential for long-term competitiveness and national energy security. SAF remains the most practical near-term solution for lowering carbon emissions, with the advantage of functioning as a true drop-in fuel requiring no modifications to aircraft or existing infrastructure.

However, despite this promise, SAF growth remains constrained by feedstock availability. The aviation industry’s commitment to net-zero carbon emissions by 2050 will require roughly 35 billion gallons of SAF annually in the United States and nearly 120 billion gallons globally. Today’s primary SAF technology – Hydroprocessed Esters and Fatty Acids (HEFA) -cannot meet that scale. HEFA relies on fats, oils, and greases (FOGs), a resource that is inherently limited. Worse, every gallon of FOGs used for SAF competes directly with renewable diesel, a market experiencing strong and sustained demand. Analysts project that by 2030, limited FOG supply will create real shortages, driving up costs and constraining production growth.

When Feedstocks Hit a Ceiling

HEFA is a highly effective platform. It is mature, reliable, and commercially efficient, representing about 1.5 billion gallons per year of global capacity. Projections suggest HEFA could continue supplying up to 80 percent of SAF production in the near term, a testament to its operational robustness.

But even the best industrial process can only go as far as its feedstock allows. Despite innovations in oilseed production, the global supply of fats and oils remains fixed within narrow limits. As early as 2030, the HEFA pathway will reach its natural cap, not because of processing limitations but due to simple resource scarcity.

Meanwhile, the U.S. Department of Energy’s 2023 Billion-Ton Report estimates that more than one billion tons of biomass could be sourced domestically each year, theoretically more than enough to meet national SAF targets. Yet HEFA cannot utilize these materials. Agricultural residues, forestry waste, and other lignocellulosic biomass streams remain incompatible with HEFA’s requirements. This reality has sent researchers and companies searching for new pathways that overcome the fundamental feedstock constraint.

The Power-to-Liquid Detour

One frequently discussed alternative is Power-to-Liquid (PtL), or e-fuels, which convert captured carbon dioxide and renewable-electricity-derived hydrogen into synthetic liquid fuels. In theory, CO₂ supply is nearly limitless. In practice, the economics are daunting. According to the National Renewable Energy Laboratory (NREL), producing enough PtL fuel to meet U.S. aviation demand would require approximately 3,500 terawatt-hours of renewable electricity per year—more than five times current U.S. wind and solar generation and roughly 85 percent of total national electricity consumption.

With renewable power already under pressure from electric vehicles, industrial applications, and data centers, scaling PtL in the near term is unlikely. While the pathway holds long-term promise, it does not provide an immediate or practical solution to SAF’s feedstock limitations.

The Untapped Potential of Cellulosic Biomass

The most abundant, sustainable feedstock available today is cellulosic biomass—corn cobs, husks, agricultural residues, sugarcane bagasse, and forestry byproducts. These materials are composed primarily of lignin, cellulose, and hemicellulose. The longstanding challenge is that this lignocellulosic structure is inherently resistant to biochemical breakdown. It is, quite literally, nature’s design for structural strength.

Accessing fermentable sugars from this material requires costly pretreatment steps and enzyme systems. Despite decades of effort, only one commercial-scale plant currently produces cellulosic ethanol. Other approaches, such as gasification and Fischer-Tropsch synthesis, have shown promise but continue to face infrastructure, cost, and maturity hurdles.

Having participated in numerous cellulosic fermentation initiatives myself, I’ve seen how often the issue isn’t scientific capability but practical scalability. The industry has been searching for a biological approach that is both robust and economically viable.

Cracking Cellulosics Through Mixed-Culture Fermentation

One of the more promising developments draws from nature itself. Mixed-culture fermentation, the same microbial process active in wetlands, landfills, and even animal digestive systems, naturally converts organic materials into volatile fatty acids (VFAs). These mixed microbial communities offer several advantages for cellulosic conversion:

• They tolerate impurities.
• They adapt well to heterogeneous feedstocks.
• They require less pretreatment.
• They can process materials unsuitable for traditional yeast-based ethanol fermentation.

Laboratory studies demonstrate that lignocellulosic materials such as corn stover, bagasse, and various organic waste streams can be converted into VFAs using this approach. From there, well-established chemical upgrading processes can transform the VFAs into ketones. Importantly, these ketones share structural similarities with the triglycerides used in HEFA, allowing existing HEFA refining infrastructure to process them with minimal or no modification.

This biological-to-chemical connection effectively builds a bridge between abundant biomass resources and proven refining assets.

Merging Biology With Industry

The integration of biological conversion and industrial chemistry may represent the most practical pathway for scaling SAF production beyond current limits. By producing VFA-derived ketones that can be refined through established HEFA systems, the industry can unlock a vast feedstock pool that includes agricultural residues, forestry waste, and other non-food biomass.

One company advancing this approach is BioVeritas, which is working to commercialize mixed-culture fermentation and ketone upgrading at scale. Pulling from my time leading novel technology scale-ups, one notable differentiator is BioVeritas’ systematic, staged feedstock evolution strategy. Rather than immediately shifting to the most complex materials, the company is taking a disciplined, stepwise approach that builds operational confidence before moving into advanced feedstocks such as lignocellulosic biomass.

This is a significant departure from past cellulosic efforts, many of which attempted to prove the technology and master the hardest feedstocks simultaneously, a difficult combination. By contrast, BioVeritas’ strategy positions its process to succeed where many earlier ventures struggled.

SAF is also an ideal first market for demonstrating this technology. The sector places high value on waste-stream utilization, and once cellulosic conversion is validated here, the same platform can be applied to a wide range of other biobased products.

A Path Forward for Sustainable Flight

The global aviation sector stands at a pivotal moment. HEFA has played a critical early role but is nearing its natural feedstock limit. Power-to-Liquid technologies remain promising but are years away from cost-effective deployment.

The greatest near-term opportunity lies in connecting new biological pathways with existing industrial refining infrastructure. By leveraging natural, catalytic upgrading, and HEFA’s established capabilities, the industry can finally access the billions of tons of biomass identified by the DOE.

For an industry balancing economic reality with environmental responsibility, this integrated approach offers a practical, scalable solution. It provides a pathway for SAF to expand beyond current constraints and positions aviation to achieve its long-term decarbonization goals.