Turning table scraps into jet fuel, researchers have unveiled a breakthrough method to convert food waste into high-quality sustainable aviation fuel - promising cleaner skies and a powerful step toward net-zero emissions.
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Researchers have explored a novel pathway for producing sustainable aviation fuel (SAF) from food waste using hydrothermal liquefaction (HTL) followed by catalytic hydrotreating. Their study, published in the journal Nature Communications, demonstrates the effectiveness of cobalt-molybdenum catalysts in converting pretreated biocrude oil derived from food waste into a viable SAF candidate.
The findings highlight the potential of waste-to-energy technologies to advance sustainable fuel production and reduce greenhouse gas emissions in the aviation sector.
Addressing Greenhouse Gas Emissions in Aviation
The aviation industry contributes approximately 2-3 % of global greenhouse gas emissions and 11 % of US emissions, highlighting the urgent need for cleaner alternatives to conventional jet fuels. As the United States aims to meet its SAF Grand Challenge of achieving 100 % domestic aviation fuel demand with net-zero carbon emissions, SAFs emerge as a key solution capable of reducing lifecycle emissions by up to 80 %.
In this context, HTL offers a promising pathway for SAF production by converting wet biomass, such as food waste, into biocrude oil under high temperatures and pressures. By utilizing waste feedstocks, HTL supports circular economy principles. A Circularity Index (CI) analysis indicates that implementing this SAF pathway improves energy circularity by 31.1 % and carbon circularity by 17 % compared to conventional jet fuel.
Experimental Approach: Converting Food Waste to Biocrude
Researchers focused on converting food waste sourced from a local processing plant in Champaign, Illinois, using a pilot-scale continuous plug flow HTL reactor. They processed the waste at a solid content of 20 wt% under conditions of 300 °C and 12.4 MPa for 20 minutes, producing biocrude oil. To meet aviation fuel specifications, the produced biocrude was refined using a multi-stage pretreatment process that involved desalting, dewatering, and deashing through sequential water washes and distillation.
The quality of the refined oil was further improved through catalytic hydrotreating using cobalt-molybdenum on alumina (CoMo/Al2O3) catalysts, which removed heteroatoms such as nitrogen, oxygen, and sulfur. The hydrotreating experiments employed Taguchi design and Box-Behnken design methodologies to optimize parameters affecting the process, including temperature, catalyst-to-oil ratio, and retention time. The resulting products were then analyzed for yields, elemental composition, and heteroatom removal efficiency.
Key Results: Fuel Quality and Efficiency Metrics
The outcomes indicated that the hydrotreating process achieved high deoxygenation efficiency (76-100 %), reducing the oxygen content of the biocrude to 2.21 wt%. Sulfur removal reached up to 94 %, resulting in a final sulfur level of 10 ppm, which is well within the ASTM aviation fuel standards. Nitrogen removal was less efficient, ranging from 7 % to 23 %, with a residual nitrogen content of 0.55-0.66 wt%. The study identified temperature, catalyst-to-oil ratio, and retention time as the most influential factors affecting overall fuel quality.
Under optimized conditions, the hydrotreated product met several ASTM jet fuel specifications without blending. The upgraded fuel demonstrated a boiling point distribution with over 99 % distillate fractions below 250 °C and a higher heating value exceeding that of conventional jet fuels. Its composition, rich in n-alkanes, cycloalkanes, and aromatics, ensures suitable combustion performance and handling properties.
Potential Applications in the Aviation Sector
The successful conversion of food waste into SAF through HTL and hydrotreating is a promising approach for reducing the aviation industry’s dependence on fossil fuels. Transforming a major waste stream that typically ends up in landfills supports waste reduction and advances the bioenergy sector's circular economy.
Beyond aviation, the biocrude oil produced from food waste can be refined into other fuels such as bio-based gasoline and diesel, expanding its relevance across the transportation sector. Integrating HTL and hydrotreating technologies into existing fuel production systems could significantly lower greenhouse gas emissions and strengthen energy security. The adaptability of HTL to diverse biomass feedstocks, such as municipal solid waste and agricultural residues, broadens its potential for generating sustainable fuels.
Future Directions: Enhancing Scalability and Quality
This study highlights the potential of HTL and catalytic hydrotreating as transformative technologies for producing SAF from food waste. The findings demonstrate the feasibility of generating high-quality SAF that meets industry standards while addressing waste management challenges simultaneously. By converting waste (specifically food waste) into renewable energy, this approach supports the development of a circular bioeconomy and contributes to global sustainability and climate goals.
Future work should focus on optimizing hydrotreating conditions to enhance nitrogen removal, improve cold flow properties, and explore alternative catalysts that can further elevate fuel quality. Evaluating the scalability of this process and its integration into existing fuel supply chains is also crucial for ensuring commercial viability. As the demand for low-carbon energy increases, such innovations will be essential in helping the aviation sector achieve net-zero emissions and transition toward a more sustainable future.
Journal Reference
Summers, S. et al. (2025). From food waste to sustainable aviation fuel: cobalt molybdenum catalysis of pretreated hydrothermal liquefaction biocrude. Nat Commun 16, 9570. DOI: 10.1038/s41467-025-64645-y, https://www.nature.com/articles/s41467-025-64645-y
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