Illinois study explores feasibility of creating sustainable jet fuel from food waste
image:
Sabrina Summers and Yuanhui Zhang, University of Illinois Urbana-Champaign, hold vials of the sustainable aviation fuel developed in their lab.
view moreCredit: Marianne Stein/College of ACES
URBANA, Ill. – The aviation industry accounts for a large portion of global greenhouse gas emissions. Biobased, sustainable aviation fuel (SAF) can mitigate climate impacts, but transitioning to SAF faces critical supply chain constraints. A research team at the University of Illinois Urbana-Champaign has developed a method to produce jet-grade fuel from food waste, contributing to a circular bioeconomy. In a new paper, published in Nature Sustainability, they focus on technical and economic considerations.
In a previous study, the researchers outlined the process of developing SAF that meets aviation standards. This study follows the same general approach, converting food waste to crude oil through hydrothermal liquefaction (HTL), a process that mimics natural formation of crude oil in a fraction of the time, and refining it with a catalyst.
“However, here we use a simpler approach with less catalytic intensity and greater focus on distillation, which is commonly used for industrial purposes. This is a more economical and environmentally friendly method. But the quality of the fuel is not as good, and it needs to be mixed with regular jet fuel,” said corresponding author Yuanhui Zhang, Founder Professor in the Department of Agricultural and Biological Engineering (ABE), part of the College of Agricultural, Consumer and Environmental Sciences and The Grainger College of Engineering at the U. of I.
Zhang compared this to the use of ethanol for cars; it must be blended with fossil fuel to work in car engines.
“It would be very difficult to produce enough SAF to meet industry needs, so it makes sense to take a biodiesel approach with a percentage blend,” he explained. “Our tests are based on a 50-50 blend, so it will certainly be feasible to use a 10% or 20% blend of SAF with regular fuel.”
The researchers conducted tests on key parameters to ensure their SAF product meets jet fuel standards set by the American Society for Testing and Materials (ASTM) and the Federal Aviation Administration.
“We are still doing this work on a very small scale. But my lab is now set up to produce several liters of upgraded fuel, which is enough for diesel engine tests. After that, the next step will be jet engine tests,” Zhang said.
The biggest bottleneck in SAF production is getting the waste from disposal to reclamation and recovery, Zhang noted. Most food waste ends up either in a landfill or a wastewater treatment plant, where it is separated and converted into sludge. Collecting and reusing food waste presents logistical challenges, but the HTL process enables use of treated wastewater as feedstock.
While HTL offers a promising approach to create SAF from wet waste, it leaves a toxic, nutrient-rich byproduct called HTL aqueous phase, or HTL-AP. Zhang and his team explored ways to recover acid and nutrients from HTL-AP through electrochemical (EC) treatment.
The researchers also conducted techno-economic and lifecycle analysis for the integrated process of upgrading the biocrude oil and treating the HTL-AP byproduct. They developed three scenarios for the analysis: A baseline where HTL-AP was sent to a centralized wastewater treatment plant; treatment with EC technology to recover and valorize HTL-AP; and a future scenario based on improved EC technology.
Compared to the baseline scenario, using EC technology nearly tripled the cost per gallon due to higher capital and operating costs. However, technological advances are expected to lower the EC costs, so they become equivalent to baseline in the future.
The team also evaluated global warming potential (GWP), which indicates how much global warming is affected by CO2 emissions. They estimated that both the baseline and the improved EC treatment would be able to achieve negative carbon emissions, leading to lower GWP.
The study outlines a technically feasible and environmentally beneficial pathway for turning urban organic waste into SAF and promoting a circular bioeconomy, the researchers concluded.
The paper, “A circular hydrothermal refinery for sustainable aviation fuel from food waste,” is published in Nature Sustainability [DOI: 10.1038/s41893-026-01848-1].
Research in the College of ACES is made possible in part by Hatch funding from USDA’s National Institute of Food and Agriculture. This study was also supported by the National Science Foundation (award no. 1804453), the Department of Energy (project no. DE-EE0009269), and the 2115 Talent Development Program of China Agricultural University.
Journal
Nature Sustainability
Article Title
A circular hydrothermal refinery for sustainable aviation fuel from food waste
Article Publication Date
23-Jun-2026
Tracking melanoidins to improve food-waste biogas recovery
By combining ultraviolet-visible spectroscopy, three-dimensional excitation-emission matrix fluorescence spectroscopy, parallel factor analysis, methane production tests, and microbial community analysis, the team found that higher hydrothermal temperatures continuously promoted melanoidin formation, especially above 140 °C. These compounds showed a clear dose-dependent inhibitory effect: low doses reduced digestion efficiency and methane quality, while high doses triggered near-complete system collapse.
Food waste is rich in organic matter and is widely considered a promising substrate for anaerobic digestion, a process that converts biodegradable materials into methane-rich biogas. Hydrothermal pretreatment is often used to accelerate the breakdown of complex food-waste components and overcome the slow hydrolysis stage of digestion. However, higher pretreatment temperatures can also promote Maillard reactions between sugars and amino compounds, generating melanoidins. Because melanoidins are structurally complex, difficult to isolate, and lack standard reference materials, their formation and biological effects have remained hard to quantify. These uncertainties have limited the optimization of hydrothermal pretreatment coupled with anaerobic digestion.
A study (DOI: 10.48130/een-0026-0008) published in Energy & Environment Nexus on 21 April 2026 by Guangsuo Yu’s & Lu Ding’s team, East China University of Science and Technology, reports that melanoidins increase with hydrothermal temperature and inhibit methane production by disrupting methanogenic microbial communities.
The researchers first prepared simulated food waste composed of cooked rice, pork, and cabbage, representing starch-rich, protein-rich, and cellulose-rich components. The waste was hydrothermally treated at 120, 140, 160, 180, and 200 °C for one hour, and the resulting hydrothermal liquid products were analyzed. Dissolved organic carbon increased up to 160 °C, indicating enhanced hydrolysis of macromolecules, but declined at higher temperatures as polymerization and condensation shifted carbon into less soluble products. Meanwhile, pH decreased from 5.62 to 3.59 as temperature increased, showing stronger acidification. The team then used UV-Vis spectroscopy to assess aromaticity and color-related absorption. SUVA254 and absorbance at 350 nm both rose markedly when temperatures exceeded 140 °C, indicating increased formation of aromatic, brown-colored melanoidin-like compounds. To strengthen semi-quantitative characterization, they applied three-dimensional fluorescence spectroscopy and parallel factor analysis. The model identified two fluorescent components, with Component 1 assigned mainly to melanoidins. Its maximum fluorescence intensity increased continuously from untreated samples to the 200 °C group, reaching 374.14 a.u., confirming that melanoidins accumulated progressively with hydrothermal severity. The researchers next prepared food-waste-derived melanoidins and added them to anaerobic digestion systems at four dosage levels: 2.08, 4.16, 6.24, and 8.32 mg·mL−1. Low-dose additions reduced methane content and impaired digestion performance without causing full acidification failure. In contrast, high-dose additions sharply suppressed methane production by 98.15% and 99.24%, with methane content dropping below 10% and final pH values falling well below the optimal range for methanogens. Microbial sequencing showed that melanoidins reshaped bacterial and archaeal communities. Bacterial groups related to acid fermentation remained active, but methanogenic archaea, including key methane-producing taxa, were strongly disrupted. This suggests that melanoidins mainly block the methane-production stage rather than the early acid-production stage.
Overall, the study reveals that hydrothermal pretreatment is a double-edged strategy for food-waste resource recovery. While it can enhance hydrolysis and accelerate substrate breakdown, excessive thermal severity promotes melanoidin accumulation, which weakens methane production and may collapse anaerobic digestion systems. By establishing a semi-quantitative approach for tracking melanoidins and linking dosage effects to microbial responses, the work offers practical guidance for selecting hydrothermal conditions that balance organic-matter solubilization with biological digestibility. Future applications may include pretreatment-temperature control, melanoidin monitoring, and microbial management strategies to improve stable biogas production from food waste.
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References
DOI
Original Source URL
https://doi.org/10.48130/een-0026-0008
Funding Information
This work was supported by the project of the National Key Research and Development Program of China (Grant No. 2022YFC3902404), and the National Natural Science Foundation of China (Grant No. 22278142).
About Energy & Environment Nexus
Energy & Environment Nexus is a multidisciplinary journal for communicating advances in the science, technology and engineering of energy, environment and their Nexus.
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Semi-quantitative characterization of melanoidins during hydrothermal treatment of food waste and their impact on anaerobic digestion
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