Key Takeaways

• A new study finds that sustainable aviation fuel made from municipal solid waste could reduce greenhouse gas emissions by 80-90% compared with traditional jet fuel.
• Municipal solid waste-derived sustainable aviation fuels are less costly than other sustainable fuel pathways but still require policy support.

Aviation currently contributes about 2.5% of total global carbon emissions, and with air travel demand expected to double by 2040, cutting those emissions has become a pressing priority. One path forward is sustainable aviation fuel, a low-carbon alternative made from feedstocks such as used cooking oil and crops. But despite its potential, sustainable aviation fuel makes up less than 1% of global jet fuel use, mainly due to high production costs and limited supply.

A new study in Nature Sustainability points to a promising breakthrough: using municipal solid waste as a reliable, low-emission, cost-effective feedstock for sustainable aviation fuel.

Researchers from Tsinghua University and the Harvard-China Project on Energy, Economy, and Environment evaluated municipal solid waste-based jet fuel produced through industrial-scale gasification and Fischer-Tropsch synthesis. A life cycle analysis found that jet fuel made from municipal waste could reduce greenhouse gas emissions by 80-90% compared with conventional jet fuel. The main technical hurdle lies in scaling up gasification systems for widespread use.

“Unlike road transport, which is quickly shifting toward electrification, there’s no silver-bullet solution for achieving carbon-neutral aviation,” said Jingran Zhang, the study’s first author and a postdoctoral fellow at the Harvard-China Project who is supported by the Salata Institute for Climate and Sustainability at Harvard. “Turning everyday trash into jet fuel could be an innovative but major near-term step toward cleaner aviation. By converting municipal waste into low-carbon jet fuel that already works in today’s engines, we can start cutting emissions immediately, without waiting for future technology.”

Municipal solid waste as a feedstock

Municipal solid waste includes organic matter like food scraps and paper as well as plastics and metals. Traditionally, much of this waste has been landfilled or incinerated, which consumes land or can contribute to air pollution. As landfill space shrinks and waste generation rises, converting municipal solid waste into liquid fuels could conserve land, cut emissions, and produce cleaner energy to help cities move toward zero-waste goals.

The Harvard study explores the largely under-researched potential of municipal solid waste-based jet fuel using real-world data on Fischer-Tropsch gasification technology. The researchers analyzed key emission sources, calculated greenhouse gas impacts, and identified ways to boost efficiency. They found that while the process significantly lowers emissions, only about 33% of input carbon is converted into fuel due to gas composition mismatches. Efficiency could be improved by capturing carbon dioxide or adding green hydrogen, produced with renewable power, during processing.

Global implications

Many countries are ramping up efforts to make aviation more sustainable by adopting cleaner fuels. In the United States, the government aims to produce up to 35 billion gallons of sustainable aviation fuels annually by 2050, supported by strong financial incentives. In the European Union, new regulations will require all departing flights to gradually increase their share of sustainable aviation fuels, catapulting from 2% in 2025 to 70% by 2050. On a global scale, the International Civil Aviation Organization’s CORSIA program requires operators to offset emissions growth, which they can do by buying eligible offsets or by using sustainable fuels.

The study examined how municipal solid waste could be converted into sustainable aviation fuel under several scenarios. In the most practical case, global municipal solid waste could yield around 50 million tons (62 billion liters) of jet fuel globally, cutting aviation’s greenhouse gas emissions by roughly 16%. If waste management and conversion systems are inefficient, the benefits drop substantially. However, if green hydrogen is integrated into the process, production could reach 80 million tons per year, which is enough to supply up to 28% of global jet fuel demand and reduce emissions by as much as 270 million tons of carbon dioxide annually.

In Europe, the projected output would already exceed the European Union’s jet fuel-blending targets while remaining compliant with sustainability standards. Economically, the study suggests that adopting municipal solid waste-based jet fuels could save airlines money under carbon pricing systems like CORSIA, particularly when government incentives and subsidies are factored in.
Ultimately, sustainable aviation fuel currently makes up less than 1% of global jet fuel use, mainly because of its high production costs. This underscores the urgent need for strong policy action and financial incentives to scale up supply.

“This study presents a blueprint for converting urban waste into sustainable aviation fuel, offering future environmental and economic benefits,” said lead author Michael B. McElroy, the Gilbert Butler Professor of Environmental Studies at Harvard and chair of the Harvard-China Project on Energy, Economy, and Environment. “Moving forward, broad collaboration among governments, fuel producers, airlines, and aircraft manufacturers will be essential to increase production, lower costs, and accelerate aviation’s path to net-zero emissions.”