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The other greenhouse gas

September 22, 2023

There are countless ways we’re advised to live more sustainably – drive an electric car, fly less often, don’t eat meat, shop local. And yet, there’s another environmental action that’s relatively unintrusive and low-cost: reducing food waste.

When it comes time to let go of that moldy peach or questionable leftover noodles, we typically turn to the trashcan and bid our foul food farewell. But climate scientists ask us to think twice before condemning our food to landfills where it breaks down and releases a significant portion of human-made greenhouse gases.

Viable food is lost at each point in the production chain as it travels from seed to supermarket. However, most wasted food journeys all the way to restaurant kitchens and homes, only to end up uneaten in the garbage. The EPA, USDA and the United Nations have each set goals to address household food waste, aiming to cut it in half by 2030.

(Graphic shows the breakdown of food wasted along the production chain and how much went to landfill in 2021. Homes are the biggest food waste contributors in the United States. Almost half of household food waste is thrown in the garbage. The majority of food in landfills comes from homes. )

Over time, food is buried under other waste and decomposes in anaerobic conditions (without access to oxygen), creating a favorable environment for bacteria that produce methane, a greenhouse gas 28 times stronger than carbon dioxide over a 100-year period.

“The whole characteristics of food – that they’re rich in energy, rich in proteins, rich in nutrients and that they’re relatively easy to extract that energy from – means that in the landfill environment, they will generate more methane than a lot of other waste components,” said Max Krause, an engineer with the EPA’s Office of Research and Development.

“Solid food waste in landfills generates incredible amounts of methane every year, just based on the fact that food is sitting in piles and it decomposes in anaerobic conditions,” said Kevin Karl, a researcher at NASA’s Center for Climate Systems Research who is also an Environmental Statistics Consultant at the Food and Agriculture Organization of the United Nations.

When we talk about global warming, we think about carbon dioxide. It’s one of the most abundant greenhouse gases in our atmosphere and is commonly the center of conversation for slowing climate change. But methane is worth some attention.

(Graphic showing the contribution of different greenhouse gases to warming influence on the earth from 1750 to 2021. Carbon dioxide contributes the most warming effect, 66%. Methane comes in second, contributing 16%. Note: Data shows the contributions of the most important greenhouse gases to the increase in “radiative forcing” or the change in heating of the earth’s surface since the pre-industrial era, 1750. Source: World Meteorological Association Greenhouse Gas Bulletin )

Reducing methane is key in achieving temperature limits set in the 2015 Paris Agreement, according to the United Nations Environment Programme and other environmental groups. Opportunities to cut methane are relatively inexpensive compared to its infamous companion, carbon dioxide. And there are two factors that might make methane most attractive to target: It is potent and it is short-lived.

Methane’s Global Warming Potential is 100 times that of carbon dioxide for its first 20 years in the atmosphere, but methane leaves the atmosphere in a fraction of the time. The carbon dioxide we emit today will continue warming our planet for up to 100,000 years, but methane only lasts for a timescale of 12 years before breaking down into less potent gases.

“One of the fastest ways to improve the quality of life for people that already exist on the planet is to reduce methane that is currently being emitted,” Karl said.

There is not one solution that will reduce enough methane to be in line with the Paris Climate Agreement. Instead, researchers say, it will take action in many sectors to meet the goal.

Methane produced by food decomposing in landfills makes up 1.6% of all human-made Greenhouse Gas emissions. While that may not sound like much, it’s a large percentage for such a specific pollutant. When scientists look at hyper-specific categories, Karl says, anything over 1% is significant.

“Any action that can prevent food waste from sitting in untreated piles will directly lead to climate impacts being reduced.”

Reuters looked at how consumers can divert food away from landfills to help reach the goal of cutting household food waste in half by 2030: READ MORE

By Ally J. Levine and Daisy Chung


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