Stephanie Keith/The New York Times

Fruit and vegetables distributed by Vivian Lin, who provides local produce to New Yorkers in exchange for their food scraps and other organic waste, in Brooklyn on July 19, 2020.

April 22, 2021

Composting Allows Redemption of Food Waste, Third Largest Threat to Global Climate

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As the United Nations World Meteorological Organization warns that the Earth continues to somersault towards irreversible climate change consequences — Cornellians are composting their food scraps to minimize their carbon footprint.

When food ends up in landfills, it has the potential to emit methane, a greenhouse gas — which contributes to global warming. 

“In landfills [where food waste lands], food is tucked away without access to oxygen, and undergoes anaerobic decomposition, a process that releases methane,” explained Emma Goldenthal ’22. “People have found whole cabbage heads in landfills, years later.”

According to the UN Food and Agriculture Organization , anaerobic decomposition of food waste contributes to 3.3 gigatonnes of greenhouse gas emissions — a value comparable to the total carbon emissions of China or the United States.

“Composting is this alternative, where you can put your food to good use and eliminate the bad effects of food waste cost,” said Megan Feely ’22.

According to Jean Bonhotal grad, director of the Cornell Waste Management Institute in Soil and Crop Sciences, composting makes use of small insects and microbes to speed up the natural decaying of organic wastes like food scraps and yard trimmings.

“Having diverse feedstocks  — different ingredients  — in your compost allows more organisms to come in and feed,” Bonhotal said. “We’re making an ecosystem that these microorganisms are going to live in for a while, so that they’re able to mineralize the organics.”

Leigh Miller ’22, Feely and Goldenthal, leaders of the student organization Cornell Compost, told The Sun that a healthy compost pile must be balanced in nitrogen and carbon content. 

“A healthy compost pile smells warm and earthy, not gross or rotten,” Miller said. “It doesn’t smell like moldy or gross or rotten. Because [you have the] right ratio, [of organisms] breaking everything down.”

Mineralization — the chemical process that turns food scraps into compost through oxidation —  is defined by soil scientists as the oxidation of nutrients that links microbial energy cycles and carbon cycles. Nitrogen fixing bacteria, such as rhizobium, incorporate nitrogen from vegetable scraps to fuel their own cellular energy needs, and release the carbon fragments of amino acids found in composted greens to free them up for oxidation 

When carbon is oxidized for energy by microorganisms such as fungi in the compost pile, it is released as carbon dioxide — as opposed to being reduced to methane in landfills. 

Microorganisms raise the internal temperature of compost piles up to 120 degrees in the process of carbon and nitrogen breakdown, which drives food waste degradation. When bacteria run out of compounds to mineralize, temperatures decrease and mesophiles— bacteria that withstand temperatures of 20-45 degrees —  finish off maturing, or “curing,” the compost, Bonhotal explained.

After several months, composting yields a healthy, nutrient-dense humus that can strengthen poor soils, often referred to as black gold. Compost fertilizers yielded from this process contribute to revitalizing infertile soils through increasing biodiversity and buffering the soil pH, Bonhotal says.

At Cornell, through converting 4,000 tons of organic wastes each year, from dining hall food scraps, animal bedding and plant debris from campus landscaping — the University is working toward the UN’s Sustainable Development Goals of slashing food waste by 50 percent before 2030.

Cornell Compost, are among those on campus recognizing the importance of addressing food waste as a contributor to climate change.

“Approaching composting from like an individual perspective and an institutional perspective is a huge part of our mission as a club,” Goldenthal said. “Institutionally [we want to emphasize] providing the infrastructure to students and making sure composting bins are almost as available, ideally, as recycling bins.”