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Everyday trash, food waste, and even discarded metal and rubber scraps can be used as a source of sustainable aviation fuel, Harvard researchers concluded in a new study published last month in the journal Nature Sustainability.
The researchers from the Harvard-China Project on Energy, Economy, and Environment and Tsinghua University in Beijing found that solid municipal waste can be transformed into liquid-based feedstock — shown to significantly reduce greenhouse gas levels compared to regular jet fuel. Waste, they found, can also be more reliable and less expensive than other sustainable fuels.
The researchers said their goal was to find ways to reduce carbon emissions in aviation, which currently contributes to around 2.5 percent of total global carbon emissions.
Jingran Zhang, a postdoctoral fellow with the Harvard-China Project and the study’s first author, said because the industry is limited by challenges in fully electrifying aircraft, finding sustainable forms of jet fuel provides an alternative.
“We’re thinking about a way to have a low-cost, more reliable-availability, and with-low-emissions feedstock,” Zhang said.
The study focused on municipal waste in part because policymakers are also trying to determine how to reduce the buildup of trash, especially material that does not quickly biodegrade.
“We are actually trying to align the goal of zero waste cities and carbon neutral aviation,” Zhang said. “It kind of could achieve those two goals at the same time.”
While scientists have already concluded that jet fuel is possible to develop from vegetable oil and other agricultural products, the process has ambiguous emission mitigation effects and it has proven difficult to scale where it has been tested. According to the study, municipal waste by comparison is more readily available and less seasonally variable than agricultural products.
“We are trying to look for something more sustainable,” said Zhang.
The study formally began two years ago, when researchers from Tsinghua began utilizing gasification to transform municipal waste into a thin gas that could become a source for biofuel or feedstock. But purifying the gas to make it usable as a fuel proved especially difficult due to its high moisture content and particles to filter out, according to Zhang.
“The challenge of this process, mainly, is in the gasification,” Zhang said. “It is a bottleneck of this process.”
Zhang said that the Harvard and Tsinghua teams were “a perfect match.”
“They are working on some gasification, and then we are looking for some solution for the aviation sector,” Zhang said.
In the next stage of the research, Zhang and the research team hope to move towards sectors that rely on fuel outside of aviation.
“We’re definitely going to move on to more low carbon-fuels, especially methanol,” Zhang said.
Zhang added that this is only one of the many pathways to generate sustainable aviation fuels. But the results of the study and the development of sustainable jet fuels advance the scientific understanding of how to decarbonize the industry, she said.
“Just thinking about that helps us to understand what we can do to help with the carbon neutral future,” Zhang said.
—Staff writer Danielle J. Im can be reached at [email protected].
—Staff writer Neeraja S. Kumar can be reached at [email protected]. Follow her on X @neerajasrikumar.
