The food we eat is responsible for a third of global greenhouse gas emissions caused by human activities, according to two comprehensive studies published in 2021.
“When people talk about food systems, they always think of the cow on the farm,” says statistician Francesco Tubiello, lead author of a report appearing last June. environmental research paper, True, cows are a major source of methane, which, like other greenhouse gases, traps heat in the atmosphere. But methane, carbon dioxide and other planet-warming gases are released from many other sources along the food production chain.
Before 2021, scientists such as Tubiello of the Food and Agriculture Organization of the United Nations were well aware that changes in agriculture and related land use accounted for about 20 percent of the planet’s greenhouse gas emissions. Such land use changes include cutting down forests to graze cattle and pumping groundwater into flooded areas for agriculture.
But the new modeling technique used by Tubiello and his colleagues, as well as worked with a study by a group from the European Commission, brought to light another big driver of emissions: the food supply chain. All the steps that move food from farm to our plates to landfill – transportation, processing, cooking and food waste – bring food-related emissions down by 20 percent to 33 percent.
To slow climate change, the foods we eat deserve the same major attention as burning fossil fuels, says environmental scientist Amos Tai from the Chinese University of Hong Kong. The full picture of food-related emissions shows that the world needs to make drastic changes to the food system if we are to reach international goals for mitigating global warming.
change from developing countries
Scientists have gained a clearer understanding of global human-related emissions in recent years through databases such as EDGAR, or the Emissions Database for Global Atmospheric Research, developed by the European Union. The database covers the human-emitting activities of every country, from energy production to landfill waste, from the 1970s to the present. EDGAR uses a unified methodology to calculate emissions for all economic sectors, says Monica Crippa, a scientific officer at the European Commission’s Joint Research Center.
Crippa and his colleagues, with the help of Tubiello, created a collaborative database of emissions related to the food system, called EDGAR-FOOD. Using that database, the researchers arrived at a third estimate, similar to Tubiello’s group.
Crippa’s team counts, reported in nature food In March 2021, food system emissions were split into four broad categories: land (including both agriculture and related land use change), energy (used for production, processing, packaging and transportation of goods), industry (farming). (including the production of chemicals used in food and materials used to package food) and waste (from unused food).
Land area is the biggest culprit in food system emissions, Crippa says, accounting for about 70 percent of the global total. But the picture looks different in different countries. The United States and other developed countries rely on highly centralized megafarms for most of their food production; Therefore the energy, industry and waste categories make up more than half of these countries’ food system emissions.
In developing countries, agriculture and changing land use contribute much more. Emissions in historically less developed countries have also been increasing over the past 30 years, as these countries have cut wild areas for industrial farming and began to eat more meat, with effects in all four categories of emissions falling into one. and is a major contributor.
As a result, agriculture and related landscape shifts have led to large increases in food system emissions among developing countries in recent decades, while emissions have not increased in developed countries.
For example, according to the Edgar-Food Database, China’s food emissions increased by about 50 percent from 1990 to 2018, largely due to an increase in meat eating. In 1980, the average Chinese person ate about 30 grams of meat a day, Tai says. In 2010, the average person in China ate nearly five times as much, or just 150 grams of meat a day.
top emitting economies
In recent years, Crippa says, the six economies, the top emitters, accounted for more than half of total global food emissions. These economies are, in order, China, Brazil, the United States, India, Indonesia, and the European Union. The vast populations of China and India help drive their high numbers. Brazil and Indonesia make the list because large parts of their rainforests have been cut down to make room for farming. When those trees come down, a huge amount of carbon flows into the atmosphere (SN: 7/3/21 and 7/17/21, p. 24,
The United States and the European Union are on the list due to heavy consumption of meat. In the United States, meat and other animal products contribute to the vast majority of food-related emissions, says Richard Waite, a researcher with the World Resources Institute’s food program in Washington, DC.
Waste is also a huge issue in the United States: According to a 2021 report from the US Environmental Protection Agency, more than a third of the food produced is never actually eaten. When food is not consumed, the resources used to produce, transport and package it are wasted. In addition, uneaten food goes into landfills, which produce methane, carbon dioxide, and other gases when the food decomposes.
Meat consumption increases emissions
Climate advocates who want to reduce food emissions often focus on meat consumption, as animal products cause far more emissions than plants. “Animal production uses more land than plant production does,” says Tai, and “meat production is hugely inefficient.”
“If we eat 100 calories of grains like corn or soybeans, we get 100 calories,” he explains. All the energy of the food is delivered directly to the eater. But if instead 100 calories of grain is fed to a cow or pig, when the animal is killed and processed for food, only one-tenth of the energy from that 100-calorie grain goes to the person eating the animal. goes.
Methane production from the “cow in the farm” is another factor in meat consumption: cows release this gas through their manure, burping and flatulence. Tubiello says that methane emits more heat per tonne than carbon dioxide. So emissions from animal farms can have a major impact (SN: 11/28/15, p. 22According to the 2021 UN report, these livestock emissions account for about one-third of global methane emissions.
Transfer from flesh to plants
US residents should consider how they can transition Brent Kim to a “plant-forward” diet. “Plant-forward doesn’t necessarily mean vegetarian. It means reducing animal product intake, and increasing the share of plant foods on the plate,” says Kim, program officer at the Johns Hopkins Center for a Liveable Future.
Kim and his colleagues estimated food emissions by diet and food group for 140 countries and territories, using a modeling framework similar to Edgar-Food. However, the framework only includes food production emissions (i.e. agriculture and land use), and not the processing, transportation and other pieces of the food system involved in edgar-food.
The diet of the average US resident generates more than 2,000 kilograms of greenhouse gas emissions per year, researchers report in 2020 global environmental change, The group called “CO .” measured emissions in terms of2 equivalent,” a standardized unit that allows a direct comparison between CO.2 and other greenhouse gases such as methane.
By eating meat one day a week, this figure is about 1,600 kg of CO. is reduced to2 equivalent per year, per person. Being a vegetarian — a diet without any meat, dairy or other animal products — cuts this by 87 percent to less than 300. Going even two-thirds vegetarian leads to a huge drop of 740 kg of CO.2 equivalent.
Kim’s modeling also offers a “lower food chain” alternative, which would reduce emissions to around 300 kg of CO. brings to2 equivalent per year, per person. Eating lower in the food chain consists of a mostly plant-based diet with animal products that come from more climate-friendly sources that don’t disturb ecosystems. Examples include insects, small fish such as sardines, and oysters and other mollusks.
Tai agrees that not everyone needs to become a vegetarian or vegan to save the planet, as meat can have significant cultural and nutritional value. If you want to “start with the biggest polluter,” he says, focus on cutting down on beef consumption.
But enough people need to make these changes to “send a signal back to the market” that consumers want more plant-based options, Tubiello says. White says policymakers at the federal, state and local levels can encourage climate-friendly farming practices, reduce food waste in government actions, and do other things to cut back on the resources used in food production. can take steps.
For example, the World Resources Institute, where White works, is part of an initiative called the Cool Food Pledge, which companies, universities and city governments have signed up to reduce the climate impacts of the food they serve. . Waite says institutions agree to track the food they buy each year to make sure they’re moving toward their goals.
Developed countries like the United States – which have been heavy meat consumers for decades – can make a big impact by changing food choices. Indeed, a paper published in nature food It revealed in January that if the populations of 54 high-income countries switched to a plant-focused diet, annual emissions from these countries’ agricultural production could drop by more than 60 percent.
