If global food waste was a country, it would be the third-largest contributor to greenhouse gas emissions in the world.1 Wasted food contributes about 3.3 gigatons of carbon dioxide emissions equivalent (CO2e) emissions to the atmosphere every year, according to the United Nations Food and Agriculture Organization.2
Wasted food rotting in landfills also breeds one of the most potent greenhouse gases—methane—as bacteria feed on the organic waste in the oxygen-poor conditions of a trash heap. While the total emissions from American landfills have actually been decreasing in recent years, the methane emissions from the food waste sent there are increasing, according to the U.S. Environmental Protection Agency.3 People waste so much food, the agency reports, that what they’re tossing emits the same amount of pollution as more than 50 million gas-powered vehicles.
Human-caused climate change also stands to make our food waste problems worse. As the likelihood of extreme weather events like droughts and floods increase, food all through the supply chain becomes increasingly vulnerable to loss. This could look like lowered nutrient levels in some crops, the expansion of pests and infestations, and even the inability of ships to access ports.4,5
How is food waste connected to climate change?
Producing food takes energy, so every lost morsel is also lost energy. Much of the equipment used throughout the production cycle, like harvesters and combines used in fields, relies on burning of fossil fuels like oil and gas. According to the U.N., 38% of the total energy used in global food systems goes towards making food that’s ultimately wasted or lost.6 Worldwide, the food sector sucks up about 95 exajoules of energy every year, which is equal to the amount of energy found in 16.5 billion barrels of oil—just over 6 billion of which would then go to waste.7
Decaying food also plays a huge role in the climate change equation. The millions of tons of rotting organic matter in landfills emit harmful greenhouse gases, particularly methane—a gas around 28 times as potent at carbon dioxide. Depending on the landfill, solid waste (including food) typically ends up in heavily compacted conditions where there is no oxygen. The bacteria that feed on that waste thrive in those anaerobic conditions, producing methane. Food waste is responsible for the majority of methane emissions in U.S. landfills, accounting for 58% of the total, according to the EPA.8
While landfills do have methods to trap these emissions, such as wells that capture the gas for treatment and reuse, they’re not foolproof fixes. The EPA estimates that 61% of the methane generated by food waste in landfills still reaches the atmosphere.9
How much methane does food waste produce?
The global food supply chain is a top emitter of greenhouse gases. In 2019, production alone accounted for about 49 million metric tons of methane emissions, largely generated by the decay of food waste in landfills and dumps.10 Given the potency of methane gas, that’s a carbon dioxide equivalent of 1.37 billion metric tons—or 367 coal-fired plants running for a year.
Only recently have we gotten a sense of how much methane food waste produces on its own. A 2023 EPA report found that food waste in American landfills produced about 55 million metric tons of CO2 equivalent methane in 2020.11 Those emissions would equal the pollution output of about 15 coal-fired power plants.
What are the world’s top contributors to methane emissions?
Around 60% of the methane that reaches the atmosphere comes from human sources, while 40% comes from natural sources like wetlands. Of the human sources of methane pollution, agriculture, fossil fuels, and food waste are the greatest contributors. From 2008 to 2017, worldwide methane emissions from human activities alone were estimated to be 359 teragrams per year—which would weigh about as much as 275 million baby humpback whales, according to The Global Methane Budget published in Earth System Science Data.12 In many instances, researchers use carbon dioxide equivalent measurements, often expressed as millions of metric tons, for air emissions. But when it comes to atmospheric methane, they often go with teragrams (the equivalent of one billion kilograms).
If global food waste was a country, it would be the third-largest contributor to greenhouse gas emissions in the world.
Agriculture and waste contributed more methane than any other sector, contributing between 191 and 223 teragrams a year; livestock and rice production, particularly, are among the highest methane producers in the sector. Fossil fuel production comes in second in methane emissions (113–154 teragrams a year), but the study authors note that this industry is responsible for 35% of all human-made emissions—not just methane. Methane emissions from burning biomass and biofuel come in a distant third, producing 26–40 teragrams a year; this category also includes residential burning of biofuels from stoves, boilers, and fireplaces.
Which countries are the top emitters of methane?
The following countries emitted the most methane annually in 2021.13 According to the International Energy Agency, these five nations are responsible for about half of all methane emissions globally.
China: 61.73 teragrams
China emits a proverbial ton of methane due to its high rate of coal production and mining. The country finds coal to be a more “stable” source of electricity compared to natural gas or renewable energy because of its massive underground coal reserves. Renewable options like hydropower, have faced historical challenges due to high temperatures and drought, particularly in the southwestern region of the country.
India: 31.85 teragrams
India’s large agricultural industry, especially from rice production, plays a key role in methane emissions there. Researchers have, however, found emissions from urban solid waste have been steadily rising in recent decades.14
U.S.: 23.24 teragrams
The U.S. contributes methane through a combination of sources, including the oil and gas sector, landfills, and agriculture.15
Brazil: 20.94 teragrams
Brazil’s agricultural sector is responsible for more than 90% of the country’s methane emissions, according to the Climate & Clean Air Coalition. That pollution is heavily linked to the manure generated by the region’s animal operations, much of which is repurposed as fertilizer.
Russia: 16.47 teragrams
Russia’s oil and gas operations are to blame for most of its methane emissions. According to the International Energy Agency, oil and natural gas revenues account for nearly half of the country’s federal budget.
Which foods cause the most methane emissions?
When food waste decomposes in conditions without oxygen—like when they’re trapped in plastic garbage bags and landfills—it creates methane emissions. But some foods, including beef and rice, are also responsible for higher methane emissions throughout their lifespan from harvest to table.
However, animal-based food products are responsible for the most greenhouse gas emissions, especially red meat, dairy and farmed shrimp, in part because of the resource-intensive needs related to their production. The United Nations estimates that ruminant (i.e. farmed cattle, sheep, and goats) supply chains produce 5.7 billion tons of CO2 equivalent annually, accounting for 16% of the world’s total emissions.16 According to the American Society for Microbiology, ruminants themselves emit about as much methane as the oil and gas industry, accounting for 27% of the world’s human-caused methane air pollution in 2020.
People waste so much food that what they’re tossing emits the same amount of pollution as more than 50 million gas-powered vehicles.
Rice is another high methane contributor. According to one 2020 Earth System Science Data (ESSD) report, rice was responsible for 8% of total manmade methane global emissions between 2000 and 2017.17 That’s because most rice is grown in flooded paddy fields where oxygen levels are low—much like the anaerobic, though drier, conditions in landfills. During that same time period, rice contributed about 30 teragrams of methane emissions annually.
Implications of food waste on the environment, beyond climate change
Lost food isn’t simply a matter of an old head of lettuce going to waste, or an unused carton of milk rotting away. With each food product lost or wasted also goes the energy and water used to create, transport, and sell that product. “It’s hard for me to think about the waste at the farm level without thinking about water issues,” said Pennsylvania State University professor Edward Jaenicke, who studies food waste and related topics and recently published one of the first comprehensive studies calculating household-level food waste in America.18
The loss of water resources worsens the odds of drought conditions, making proper management critical in the face of climate change. “Most of our fruits and vegetables are coming from California where water is super scarce. … When you think of all the different resources wasted on food waste, that water is some of the most precious stuff out there.”
Food waste also impacts ecosystems and biodiversity when wasted. The Center for Biological Diversity says food waste converts about 80 million acres of habitat to farmland for food that isn’t even eaten.
Meanwhile, pesticides, herbicides, and other chemicals used to protect some of those crops also create downstream pollution that threatens vulnerable species. The U.S. Fish and Wildlife Service has recognized more than 72 endangered plants threatened by the use of the herbicide glyphosate alone, while aquatic species like salamanders have also been found to be susceptible to chemical pollution finding its way to local waterways.19 The World Wildlife Fund notes that some foods—such as soy, palm oil, and cocoa—lead to the clearing of lands and destruction of rainforests.
How to mitigate climate change by reducing waste
The relationship between lost food and addressing human-caused climate change is simple: The less food we waste, the less emissions our waste creates. Since most food is lost at the retail and consumer levels, there are steps that everyday people can take to help.
Food waste at home
People can be more strategic about what they buy and consume as a way to reduce their own food waste. For example, a single person might opt to buy a bag of frozen veggies instead of a large package of fresh vegetables that are at risk of spoilage. Doing a true inventory of items at home and relying on a shopping list can help people avoid purchasing duplicate or unneeded grub that could end up in the garbage. Creative cooking tricks to avoid wasting food—like making a pie or breads out of overripe fruits or offering scraps as a snack to well-behaved dogs or backyard chickens—also help.
Composting food waste is also far better than throwing it in the trash as a means to avoid methane emissions. That’s because at-home composting includes oxygen in the process, meaning the microbes that are plentiful in anaerobic landfill conditions aren’t present to produce harmful methane.
Food waste on the farm
About 14% of the world’s food is lost after it’s harvested but before it reaches retail environments. While some on-farm losses are unavoidable during unfortunate events (e.g., when grains get wet and grow mold), other food waste never gets sold to conventional supermarkets due to buyer preferences for picture-perfect produce. Some farms have found a way to offset losses of less-than-perfect products through “misfit” produce services. Tackling food waste by at least keeping it out of landfills, Penn State’s Jaenicke says, is a step in the right direction.
Restaurant food waste
Restaurants have a variety of options to minimize their food waste. Food service establishments (including restaurants, caterers, schools, and more) can also donate non-perishable and unspoiled foods to food banks and shelters. The EPA offers some tips and outlines safety rules on how organizations (and individuals) can donate leftovers and extras. They can also work with local nonprofits and environmental groups to compost food waste—some might even choose to recycle shells from oysters and clams for restoration projects
Retail store food waste
For food retailers, mitigating food waste comes down to inventory management. National groups like ReFED offer suggestions for retailers to address food waste by focusing on how they plan, price, and purchase their goods. Retailers can also find ways to donate foods to people in need.
Implementing policies and regulations to reduce food waste
By 2030, both the U.N. and the U.S. hope to halve the amount of food waste and loss at the retail and consumer levels. This goal is a key part of the U.N.’s 17 Sustainable Development Goals, which were developed in 2015 as “a historic promise to secure the rights and well-being of everyone on a healthy, thriving planet.” In America, the EPA and USDA have joined forces to meet that same target goal. Some states have also made strides in addressing food waste with local rules and regulations, such as New York City’s shift to extend sell-by dates of pasteurized milk products.20 ReFED keeps an inventory of state-level food waste policies on its website.
- Estimating Food Waste as Household Production Inefficiency, American Journal of Agricultural Economics, Mar. 2020 ↩︎
- Food Wastage Footprint, FAO, 2013 ↩︎
- Quantifying Methane Emissions from Landfilled Food Waste, U.S. Environmental Protection Agency, Oct. 2023 ↩︎
- Impact of Anthropogenic CO2 Emissions on Global Human Nutrition, Nature Climate Change, Sep. 2018 ↩︎
- The Effect of Climate Change on Invasive Crop Pests Across Biomes, Current Opinion in Insect Science, Apr. 2022 ↩︎
- The State of Food and Agriculture, Food and Agriculture Organization of the United Nations, 2014 ↩︎
- “Energy-Smart” Food for People and Climate, Food and Agriculture Organization of the United Nations, 2011 ↩︎
- Quantifying Methane Emissions from Landfilled Food Waste, U.S. Environmental Protection Agency, Oct. 2023 ↩︎
- Ibid ↩︎
- Ibid ↩︎
- Quantifying Methane Emissions from Landfilled Food Waste, U.S. Environmental Protection Agency, Jan. 2024 ↩︎
- The Global Methane Budget 2000–2017, Earth System Science Data, Jul. 2020 ↩︎
- National Contributions to Climate Change Due to Historical Emissions of Carbon Dioxide, Methane, and Nitrous Oxide Since 1850, Scientific Data, Mar. 2023 ↩︎
- Methane Emissions in India: Sub-Regional and Sectoral Trends, Atmospheric Environment, Sep. 2011 ↩︎
- U.S. Methane Emissions Reduction Action Plan, The White House Office of Domestic Climate Policy, Nov. 2021 ↩︎
- Greenhouse Gas Emissions from Ruminant Supply Chains, Food and Agriculture Organization of the United Nations, 2013
↩︎ - The Global Methane Budget 2000–2017, Earth System Science Data, Jul. 2020 ↩︎
- Estimating Food Waste as Household Production Inefficiency, American Journal of Agricultural Economics, Mar. 2020 ↩︎
- Impact of Pesticides Use in Agriculture: Their Benefits and Hazards, Interdisciplinary Toxicology, Mar. 2009 ↩︎
- The Effect of Sell-By Dates on Purchase Volume and Food Waste, Food Policy, Jan. 2021 ↩︎