The food we eat is responsible for a staggering third of global human-caused greenhouse gas emissions, according to two comprehensive studies published in 2021.

“When people talk about food systems, they always think of the cow in the field,” said statistician Francesco Tubiello, lead author of one of the reportsappearing in June last year Letters for environmental research. It is true that cows are a major source of methane, which, like other greenhouse gases, traps heat in the atmosphere. But methane, carbon dioxide and other global warming gases are emitted by several other sources in the food production chain.

Before 2021, scientists like Tubielo of the Food and Agriculture Organization of the United Nations were well aware that agriculture and related land use changes account for approximately 20 percent of the world’s greenhouse gas emissions. Such land use changes include deforestation to pave the way for grazing livestock and pumping groundwater to flood fields in the name of agriculture.

But new modeling techniques used by Tubielo and his colleagues, plus a study by a group in the European Commission that Tubielo is working with, have unveiled another major emission engine: the food supply chain. All the steps that take food from the farm to our plates to the landfill – transportation, processing, cooking and food waste – increase food-related emissions from 20 percent to 33 percent.

To slow down climate change, the foods we eat deserve as much attention as fossil fuels, says Amos Tai, an environmental scientist at China University in Hong Kong. The fuller picture of food-related emissions shows that the world needs to make drastic changes to the food system if we are to achieve international goals of reducing global warming.

Change from developing countries

Scientists have gained a clearer understanding of global human emissions in recent years through databases such as EDGAR or Emissions database for global atmospheric research, developed by the European Union. The database covers the activities of each emitting country, from energy production to landfill waste, from 1970 to the present day. EDGAR uses a unified methodology for calculating emissions for all economic sectors, said Monica Kripa, a researcher at the European Commission’s Joint Research Center.

Kripa and colleagues, with the help of Tubiello, built an accompanying database of emissions related to the food system called EDGAR-FOOD. Using this database, the researchers came up with the same estimate of one-third as Tubielo’s group.

The calculations of the Kripa team, reported in Natural food in March 2021, divides emissions from the food system into four broad categories: land (including both agriculture and related land use change), energy (used for the production, processing, packaging and transport of goods), industry (including the production of chemicals used in agriculture and materials used for packaging food) and waste (from unused food).

The land sector is the biggest culprit for food emissions, Kripa said, accounting for about 70 percent of total global emissions. But the picture looks different in different nations. The United States and other developed countries rely on highly centralized megafarms for much of food production; so that the categories of energy, industry and waste account for more than half of the emissions of the food systems of these countries.

In developing countries, agriculture and changing land use make a much greater contribution. Emissions in historically less developed countries have also increased over the past 30 years as those countries cut wilder areas to make room for industrial agriculture and began eating more meat, another major contributor to emissions affecting all four categories.

As a result, agriculture and related landscape changes have led to significant increases in food emissions among developing countries in recent decades, while emissions in developed countries have not increased.

For example, food emissions in China increased by almost 50 percent from 1990 to 2018, largely due to an increase in meat eating, according to the EDGAR-FOOD database. In 1980, the average Chinese person ate about 30 grams of meat a day, Tai said. In 2010, the average person in China ate almost five times as much, or just under 150 grams of meat a day.

Economies with the highest emissions

In recent years, Kripa says, the six economies with the largest emissions are responsible for more than half of total global food emissions. These economies are China, Brazil, the United States, India, Indonesia and the European Union. The huge populations of China and India are helping to increase their large numbers. Brazil and Indonesia are on the list because large parts of their rainforest have been cut down to make room for agriculture. When these trees fall, huge amounts of carbon are released into the atmosphere (SN: 7/3/21 & 7/17/21, p. 24).

The United States and the European Union are on the list for heavy meat consumption. In the United States, meat and other animal products contribute to most food-related emissions, said Richard Waite, a researcher in the food program at the World Resources Institute in Washington, D.C.

Waste is also a huge problem in the United States: More than a third of the food produced is never actually eaten, according to a 2021 report from the United States Environmental Protection Agency. When food remains uneaten, the resources used to produce, transport and package it are lost. In addition, uneaten food goes to landfills that produce methane, carbon dioxide and other gases while food decomposes.

Meat consumption leads to emissions

Climate advocates who want to reduce food emissions often focus on meat consumption, as animal products lead to much higher emissions than plants. Animal production uses more land than crop production, and “meat production is highly inefficient,” says Tai.

“If we eat 100 calories of grain, like corn or soy, we get those 100 calories,” he explains. All the energy from food is delivered directly to the person who eats it. But if the 100-calorie grain value is instead fed to a cow or pig when the animal is killed and processed for food, only one-tenth of the energy of those 100-calorie grain goes to the person who eats the animal.

Methane production by ‘field cows’ is another factor in meat consumption: cows release this gas through their manure, belching and gases. Methane captures more heat per tonne of carbon dioxide, says Tubielo. So emissions from livestock farms can have a huge impact (CH: 28.11.15, p. 22). These livestock emissions account for about one third of global methane emissionsaccording to a 2021 UN report

Switching from meat to plants

People in the United States need to think about how they can move on to what Brent Kim calls “transitional diets.” “Working forward does not mean vegan. That means reducing the intake of animal products and increasing the proportion of plant foods on the plate, “said Kim, program director at the John Hopkins Living Center.

Kim and his colleagues calculated dietary and food group emissions for 140 countries and territories using a similar EDGAR-FOOD modeling framework. However, the framework only covers emissions from food production (ie agriculture and land use) and not the processing, transport and other parts of the food system included in EDGAR-FOOD.

Producing the diet of the average US citizen generates more than 2,000 kilograms of greenhouse gas emissions per yearresearchers said in 2020 Global changes in the environment. The group measures emissions in relation to “CO2 equivalents’, a standardized unit allowing direct comparisons between CO2 and other greenhouse gases such as methane.

If you run out of meat one day a week, that figure drops to about 1,600 pounds of CO2 equivalents per year, per person. Becoming vegan – a diet without meat, dairy or other animal products – reduces it by 87 percent to less than 300. If even two-thirds become vegan, this offers a significant drop to 740 kilograms of CO2 equivalents.

Kim’s modeling also offers a “low food chain” option that reduces emissions to around 300 kilograms of CO2 equivalents per year, per person. Low-chain diets combine a plant-based diet with animal products that come from more climate-friendly sources that do not disturb ecological systems. Examples include insects, smaller fish such as sardines, oysters and other mollusks.

Ty agrees that not everyone needs to become a vegetarian or vegan to save the planet, as meat can have important cultural and nutritional value. If you want to “start with the biggest polluter,” he says, focus on reducing 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, Tubielo said. Policymakers at the federal, state and local levels can also promote climate-friendly farming practices, reduce food waste in government operations and take other actions to reduce the resources used in food production, Waite said.

For example, the World Resources Institute, where Waite works, is part of an initiative called A bet for cool foodin which companies, universities and city authorities have joined in reducing the climate impact of the food they serve. Institutions agree to track the food they buy each year to ensure they are moving toward their goals, Waite said.

Developed countries such as the United States – which have been heavy consumers of meat for decades – can have a big impact by changing food choices. Indeed, a document published in Natural food January shows that if the population of 54 high-income nations switches to a plant-based diet, their countries’ annual agricultural emissions could decline by more than 60 percent.

How much does eating meat affect nations’ greenhouse gas emissions?

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