From trash to treasure: Recycling organic waste supports farmers, climate

June 5, 2025

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By Krisy Gashler

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Cornell University Agricultural Experiment Station
PRO-DAIRY
Food Science
Department of Global Development
School of Integrative Plant Science
Agriculture
Environment
Plants
Soil

Recycling isn’t just about separating paper and plastics. It’s also using fly maggots to eat garbage and then feeding the maggots to chickens. It’s extracting the nutrients from human urine to use as fertilizer and capturing the methane from dairy farms to use as an energy source.

“We don’t think about waste as a resource, but we should,” added Lori Leonard, professor and chair of global development in the College of Agriculture and Life Sciences. “Our landfills are filling up, and nobody wants a new landfill in their backyard. I think there’s a big realization that there are valuable and useful things we could do with that organic material. We can supplement animal feed, create compost and improve soils, or create energy, all while diverting nutrients from somewhere they’ll be harmful to places where they’ll be beneficial.”

Two people wearing rain jackets examine a pile of compost. — Lori Leonard, professor in the Department of Global Development, stands with a student in her Global Garbage class at the Cornell University Agricultural Experiment Station (Cornell AES) Compost Farm. Credit: Chris Kitchen

Tackling the organic waste problem

Roughly one-third of all food produced for human consumption goes to waste. To make matters worse, most waste food in the U.S. is sent to landfills, where it breaks down and creates methane, a potent greenhouse gas. About 11% of U.S. methane emissions come from landfills.

Cornell researchers are dedicated to turning trash into treasure. By studying how to divert food, manure, carcasses and other organic wastes from landfills to better purposes, like livestock feed, organic compost and renewable energy, they’re building virtuous cycles that reduce greenhouse gas emissions, generate energy and improve soil health, among a host of benefits.

A person wearing a red rubber glove holds a tray of green produce. — Processing produce waste at AgriTech. Credit: Allison Usavage.

Preserving nutrients, avoiding contaminants

Farmers have appreciated the value of recycling organic waste back into the soil for generations. But understanding the benefits and risks of such waste recycling is critical to preserving nutrients while avoiding contaminants, said Dan Buckley, microbiology professor and head of the Soil and Crop Sciences Section in the School of Integrative Plant Science.

“We have this opportunity to see the sustainable benefits of these waste resources for soil health and soil fertility, but they come with the risk of potentially hazardous compounds,” Buckley said. “That's where we need to help the people who are generating and using these materials to do so safely, and we need to be doing research to anticipate problems before they become problems.”

Supporting New York’s soil health

A large team of Cornell experts, including Joseph Amsili, Harold Van Es, Matt Ryan, and Deborah Aller (leaders of the New York Soil Health initiative) and Robert Schindelbeck (director of the Cornell Soil Health Laboratory) provide soil health resources and comprehensive testing for farmers, gardeners, agricultural service providers, landscape managers and researchers. Van Es, Schindelbeck and their colleagues published a comprehensive report, “Characterization of Soil Health in New York State,” which establishes soil health guidelines that consider the effects of region, soil type and cropping system.

A pair of hands holding a small trowel taking soil sample — Garrett Boudinot, research associate in the department of ecology and evolutionary biology, inspecting soil in a corn field at Cornell AgriTech. Credit: Allison Usavage

Two students in a field examining soil. — Natalie Bray, Ph.D. student in the department of entomology, and Abby Wentworth, technician in the Wickings lab, conduct research on the relationship between earthworms and grubs on soil health. Credit: Allison Usavage

three people stand in the distance in a corn field — From left to right, graduate student Ann Bybee-Finley, Matt Ryan and intern Pauline Mouillon at Musgrave Research Farm. Credit: Allison Usavage

Combating bird flu

Jean Bonhotal, director of the Cornell Waste Management Institute, has been helping farmers and regulatory agencies deal with the toughest organic waste disposal issues for the past 35 years. Bonhotal was called to consult on the first case of highly pathogenic avian influenza on a commercial farm, in 2015. Now, she’s working with state and federal regulators to prepare farms, respond to outbreaks and train staff in strategies to safely address mass livestock mortality.

Kreher Family Farms, based in Clarence, New York, is home to 2.5 million chickens that produce 1.8 million eggs per day. The 100-year-old family farm, run by members of the third and fourth generation, supplies eggs for Tops and Wegmans, among other retailers.

“We haven’t had avian influenza on our farm, thank God, but the farms that have had it, Jean and CWMI staff have gone to them to help them cope with mass mortality events,” said Hal Kreher ’85, co-owner of Kreher Family Farms. “When you have a big, mass burial like that, things don’t break down like you would want. Whereas when you compost, it develops the heat needed to kill the pathogens.”

a flock of birds fly over a blue track and compost pile — Cornell University Agricultural Experiment Station (Cornell AES) Compost Farm. Credit: Chris Kitchen.

Exploring organics recycling solutions

The innovative work of CALS researchers benefits farming, sustainability, contaminant removal, soil health, energy production and more.

Reducing microplastics in wastewater

Julie Goddard and her research team are engineering a unique enzyme that targets polyethylene terephthalate (PET), a common plastic used in packaging and textiles. Her lab has successfully engineered a new enzyme capable of breaking down plastic in the complex conditions found in sewage sludge, and she envisions a system in which these enzymes could someday help reduce microplastics in treated wastewater.

A graduate student wearing a white lab coat works in a food science lab — A graduate student works in professor Julie Goddard's food science lab. Credit: Allison Usavage.

Turning dairy manure into biochar

Johannes Lehmann, the New York State Energy Research and Development Authority and Spruce Haven Farm are collaborating to install New York’s first commercial dairy biochar kiln. The kiln turns separated solids from digested cow manure into environmentally friendly biochar, which decreases manure storage costs, reduces odors, and, when applied to soils, helps retain nutrients and sequester carbon.

A man looks into a metal barrel — Johannes Lehmann, professor of soil science, producing biochar in Cornell's pyrolysis facility. Credit: Allison Usavage.

Recruiting flies to recycle garbage into livestock feed

Lori Leonard is collaborating with colleagues in New York, Honduras and Kenya who are using black soldier fly larvae to transform garbage into livestock feed. “Black soldier flies don’t transmit disease,” she said. “The larva will feed on food waste for about two weeks until fully grown, and then you can feed the larva as a great source of protein and fat to chickens, tilapia, and pigs. It’s one of the mechanisms we can use to convert really low-value, difficult-to-convert food waste into something beneficial.”

Dried black soldier fly larvae in a plastic bag. — Dried black soldier fly larvae. Credit: Provided.

Helping NYS farmers reuse food waste

Leonard, extension staff with PRO-DAIRY and the New York State Department of Environmental Conservation collaborate to help farmers understand the legal and logistical options available for reusing food scraps. “If the food can’t be eaten by a human being, it requires recycling – as animal feed, as an energy source through digestion, biofuels, compost or fertilizer for ag fields,” Leonard said. “We want people to be using a recycling strategy, whichever makes the most sense for each operation.”

Three buckets sit below a sign that reads "Food Scraps" — Composting at the 2017 Grassroots Festival. Credit: Lindsay France.

Reusing organic nutrients in urban spaces

Rebecca Nelson, Johannes Lehmann, Chuan Liao and Erika Palmer are exploring strategies to reuse organic nutrients in urban and rural settings – including using human urine in compost and fertilizer. Growers in West Africa “were desperately asking the question: Where are we going to get the nutrients we need for our crops? How are we going to build our soil health?,” Nelson said. “They didn’t have a long list of options to choose from, and they realized the majority of the nutrients that a person eats come back out in their pee. Why are we wasting this when we need nutrients and the price of synthetic fertilizer is going sky high?”

Two people stand next to a yellow eco toilet. — Rebecca Nelson, professor of plant science and global development, and postdoctoral researcher Krisztina Mosdossy show off an “eco loo” source-separating toilet at the Dilmun Hill Student Farm. Credit: Sreang "C" Hok.

Uncovering the secret lives of soil microbes

Dan Buckley studies the life cycles of soil microorganisms, which are critical for soil health, nutrient cycling, carbon sequestration and agricultural yields. “Soils are alive. Soils are not just the ground that you walk on; they are a living thing made up of an ecosystem of microorganisms. Like any living thing, you have to feed it, and organic matter is how we feed our soils and keep them healthy and sustainable.”

A collection of soil samples in jars and other tools sit on top of a lab table. — Soil samples. Credit: Sasha Israel.

Krisy Gashler is a writer for the College of Agriculture and Life Sciences. 