The next frontier in clean flight? Jet fuel from city waste

Research explores sustainable aviation fuel from municipal solid waste

Harvard John A. Paulson School of Engineering and Applied Sciences

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 Municipal solid waste-based sustainable aviation fuel potential and its contribution to jet fuel demand across regions and scenarios. 

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Credit: McElroy group / Harvard SEAS

 

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.”

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Journal

Nature Sustainability

DOI

10.1038/s41893-025-01644-3 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Powering air travel with jet fuel derived from municipal solid waste

Article Publication Date

13-Nov-2025

 

Gene editing produces plants that are indigestible to pests

Researchers revisit advances in generating genetically modified plants that prevent bedbugs, beetles, weevils, and woodworms from digesting starch.

Fundação de Amparo à Pesquisa do Estado de São Paulo

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Insects that feed on starch can find veritable feasts in corn, pea, and bean crops or warehouses. It is no coincidence that the ancestors of these commercial plants developed α-amylase (alpha-amylase) inhibitor proteins, which make the starch in their seeds indigestible to pests, keeping them from becoming serious threats. However, the domestication of wild plants by humans to increase productivity and digestibility may have reduced the presence of these inhibitors.

In an article published in the Biotechnology Journal, an international group of researchers discusses the advances made in the last two decades and emphasizes the potential of gene editing to develop plants that produce these inhibitors in greater quantities to combat insect pests. Of course, care must be taken at the same time to ensure that the plants are digestible to humans and other non-target organisms, such as livestock.

The group of authors was led by researchers from the Brazilian Agricultural Research Corporation (EMBRAPA) and the Genomics for Climate Change Research Center (GCCRC), an Applied Research Center (ARC) supported by FAPESP at the State University of Campinas (UNICAMP).

“In the early 2000s, there were many advances in this area, such as the prospecting of genes encoding alpha-amylase inhibitors in different plant species, the evaluation of the specificity of these molecules against alpha-amylase enzymes in insect pests and non-target organisms, and the development of transgenic plants that overexpress these molecules. Advances were also made in protecting intellectual property through patents filed and granted,” says Marcos Fernando Basso, a researcher at the GCCRC with a scholarship from FAPESP and first author of the article.

However, the use of classical transgenics, which involves inserting genes from other species into the genome of plants of interest, discourages biotechnology and food production companies from developing and exploiting their final product. New transgenic organisms for human consumption would risk low market acceptance, in addition to high regulatory costs.

Potential

Bedbugs, beetles, weevils, and woodworms are popular names for insects that produce amylase enzymes. These enzymes convert the starch molecules found in the leaves and seeds of important agricultural crops into sugars. In their adult or larval stages, these pests can attack seeds in fields and during storage, causing economic losses and compromising food quality.

Bruchids, such as the weevil and woodworm, were among the first targets of these technologies due to the significant damage they cause, particularly to grains stored long-term. In this food-rich environment, they reproduce rapidly. Infestation can occur during pod development and persist in storage and during commercialization.

Alpha-amylase inhibitors have also proven effective against other insects. For example, the boll weevil (Anthonomus grandis) feeds on the sugars produced and stored in cotton flower buds. Similarly, the coffee berry borer (Hypothenemus hampei) is an insect whose larvae feed on coffee seeds.

The authors point out that developing varieties with higher alpha-amylase inhibitor production – provided it does not inhibit amylase enzymes in humans and non-target organisms – has great potential when using gene editing techniques.

Using these techniques to increase the expression or modify the DNA sequence of a plant’s own genes may enable the creation of plants that are not considered transgenic by the National Technical Commission on Biosafety (CTNBio). CTNBio is the technical-scientific body responsible for formulating, updating, and implementing the National Biosafety Policy for Genetically Modified Organisms (GMOs). Consequently, these technologies would be more likely to be accepted in the market. Therefore, they would be of interest to agribusiness companies for commercialization.

“Gene editing using the technique known as CRISPR [a tool that allows precise and specific genetic modifications to be made to DNA chains or genomic rearrangements to be generated] and its variations gives us the possibility of increasing the production of these inhibitors or making them more active in plants of interest to act specifically against insect pests, without the molecules being a problem for humans and animals that consume the plants or seeds. Therefore, it may be a promising path in the coming years,” concludes Basso (read more about CRISPR at revistapesquisa.fapesp.br/en/a-tool-to-edit-dna/). 

About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

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Journal

Biotechnology Journal

DOI

10.1002/biot.70098 

Article Title

Exploring Plant α-Amylase Inhibitors: Mechanisms and Potential Application for Insect Pest Control

 

UM School of Medicine researcher proposes new medical training on cannabis use

University of Maryland School of Medicine

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Study co-author David Gorelick, MD, PhD, Clinical Professor of Psychiatry at the Maryland Psychiatric Research Center

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Credit: University of Maryland School of Medicine

Maryland is one of 38 US states, along with three territories and the District of Columbia, that have legalized cannabis for medical purposes. This legal sea change has generated increasing interest in and use of cannabis and cannabis products, yet most health care practitioners and students feel underprepared to counsel patients on medical cannabis, according to a new paper co-authored by a University of Maryland School of Medicine (UMSOM) faculty member and published in JAMA Network Open.

The paper suggests key content that should be incorporated into medical school curricula so that students will have the tools they need to serve patients in a landscape of increasing legal medical cannabis use, according to study co-author David Gorelick, MD, PhD, Clinical Professor of Psychiatry at the Maryland Psychiatric Research Center. 

“This paper outlines the core competencies that physicians should possess to deal appropriately with their patients regarding medical cannabis,” Dr. Gorelick said. “The goal is to spur medical schools and residency programs to incorporate these competencies into their curricula.”

The core competencies could also help clinicians address a concurrently increasing amount of legal non-medical cannabis use, Dr. Gorelick added, as 24 states, including Maryland, now allow for adult recreational sale and use of cannabis products. 

In collaboration with more than 20 co-authors across 26 institutions, Dr. Gorelick and his colleagues characterized the gap between patient and clinician needs and the current medical school curriculum. They cited past studies showing that only 8 percent of medical school curricula mentioned medical cannabis in the 2015-2016 academic year, and that 66.7 percent of surveyed medical school curriculum deans felt their students graduated without adequate preparation for prescribing medical cannabis. At the same time, the need for cannabis-informed physicians is increasing as more people are using cannabis with or without medical supervision — UMSOM researchers studying cannabis use among pregnant women found that use increased 170 percent between 2009 and 2016, for instance. 

To better meet the needs of patients and clinicians, the authors assembled 23 clinical and scientific experts with varied backgrounds to achieve a consensus on what medical students need to know about cannabis before entering practice. The process resulted in a recommendation of six core competencies addressing the clinical utility, risks, legal landscape, and scientific evidence around medical cannabis. 

The six core competencies are:

1. Understand the basics of the endocannabinoid system.
2. Describe the main components of the cannabis plant and their biological effects.
3. Review the legal and regulatory landscape of cannabis in the US. 
4. Describe the evidence base for health conditions that are commonly managed with cannabis. 
5. Understand the potential risks of medical cannabis use. 
6. Understand basic clinical management with medical cannabis. 

Cannabis in the Curriculum at UMSOM 

Although all healthcare professions will continue to adapt to the evolving legal cannabis landscape, UMSOM is ahead of the curve in providing medical students with training on cannabis. 

”It's important that medical students be exposed to this information, and we currently provide lectures that cover cannabis fairly robustly in our pre-clerkship curriculum in the first two years of medical school,” said Dr. Joseph Martinez, MD, UMSOM Professor of Emergency Medicine and the school’s Associate Dean for Medical Education and Student Experience. Students also gain hands-on experience in caring for patients using cannabis, as well as any other medications and illicit substances, after they begin their clinical rotations, he added. 

“I’m pleased to say that the UMSOM medical student curriculum appears to incorporate most of the topics recommended in the JAMA Network Open article,” Dr. Gorelick said. “I hope that further progress will be made in including cannabis-related material in the curricula for clinical clerkships and residencies. This will help ensure that future physicians have the knowledge and expertise they need to work with patients who are using or considering using cannabis products."

Cannabis and Healthcare in Maryland

In addition to his work at USOM, Dr. Gorelick serves as editor-in-chief of the Journal of Cannabis Research and as a member of the Maryland Cannabis Public Health Advisory Council. The Council’s mission is to make public health recommendations relating to cannabis, including issues of healthcare professional training and education. The Council’s 2025 report to the Maryland Governor and General Assembly, which will be released in December, includes a list of cannabis core competencies recommended for all healthcare professionals in Maryland. This recommendation highlights the public health importance of cannabis core competencies for all clinicians. 

“Whether you know it or not, like it or not, no matter how you practice, or where you practice, you're going to be dealing with patients taking cannabis,” Dr. Gorelick said.  

About the University of Maryland School of Medicine

The University of Maryland School of Medicine, established in 1807 as the first public medical school in the U.S., continues today as one of the fastest growing, top-tier biomedical research enterprises in the world. The School has nearly $500 million total research funding, 46 departments, centers, and institutes, more than 2,200 student trainees and over 3,000 faculty members, including notable members of the National Academy of Medicine. As the largest public medical school in the DC/MD/VA region, faculty-physicians are working to help patients manage chronic diseases like obesity, cancer, heart disease and addiction, while also working on cutting-edge research to address the most critical generational health challenges. In 2024, the School ranked #12 among public medical schools and #27 among all medical schools for R&D expenditures by the National Science Foundation. With a $1.3 billion total operating budget, the School partners with the University of Maryland Medical Center to serve nearly 2 million patients annually. The School's global reach extends around the world with research and treatment facilities in 33 countries.  In Maryland, the School of Medicine is spearheading new initiatives in AI and health computing and partnering with the University of Maryland BioPark to develop new medical technologies and bioengineering ventures. For more information, visit medschool.umaryland.edu.

 

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Journal

JAMA Network Open

DOI

10.1001/jamanetworkopen.2025.35049 

Method of Research

Systematic review

Subject of Research

People

Article Title

Developing Medical Cannabis Competencies A Consensus Statement

COI Statement

Dr Gorelick reported receiving personal fees from Wolters Kluwer and Springer Nature for serving as an editor for the Journal of Cannabis Research outside the submitted work. Dr Abrams reported serving as a scientific advisor to Cannabotech outside the submitted work. Mr Barich reported serving as the chief marketing officer at Holistic Industries outside the submitted work. Dr Boehnke reported receiving grants from State of Michigan Cannabis Regulatory Agency; National Institute on Arthritis, Musculoskeletal, and Skin Diseases; and National Institute on Drug Abuse during the conduct of the study and personal fees from Viatris Inc, Tiny Buddha Yoga, Tryp Therapeutics, Southern Pain Society, and Michigan Center of Clinical Systems Improvement outside the submitted work. Dr Dahmer reported being previously employed by and owning stock in Vireo Health outside the submitted work. Mr Friedman reported serving as a member of the scientific advisory board of Acannability outside the submitted work. Dr Russo reported serving as a senior medical advisor for Canurta, a chief medical officer for Andira, and the author of a medical education platform with MM411 outside the submitted work. Dr Kogan reported receiving personal fees from Penguin Random House outside the submitted work. No other disclosures were reported.