About 17% of all food produced around the world is wasted, a drain on resources that contributes significantly to climate change, United Nations researchers revealed Monday in what the organization called the most comprehensive study of global food waste to date. 

The estimated 931 million tons of food waste is driven primarily by individual consumers, according to the U.N.’s 2021 Food Waste Index Report.  Specifically, 61% of waste comes from households, 26% from food service and 13% from retail stores like supermarkets. 

“Nearly in every country that has measured food waste, food waste levels are substantial,” said Martina Otto of the United Nations Environment Programme, which conducted the study. “If we don’t change course, it will be catastrophic.”

Waste on the household level is “equally relevant” in middle- and high-income countries, the researchers found, upending assumptions that consumers in wealthy countries waste more food. 

High-income countries produce 79 kilograms of food waste per capita per year, according to the researchers. Upper-middle income countries, meanwhile, waste 76 kilograms per capita annually, and lower-middle income countries produce 91 kilograms per person over the same period of time. There was insufficient data for low-income countries, according to the researchers. 

The authors of the report cautioned that the food waste estimates are not solely made up of edible food — they also include some inedible waste like bones, pits and eggshells. 

There was insufficient data on the breakdown of food waste between edible and inedible food waste in most countries, and edible food waste could make up a larger proportion of food waste in wealthy countries, the researchers said. 

“It’s conceivable that the proportion of edible and inedible is different between middle- and high-income countries,” said co-author Tom Quested of WRAP, a U.K.-based nonprofit that collaborated with the U.N. on the study. “This is an evidence gap that we’d like to address in the future” 

In anticipation of further food waste studies in 2022, the U.N. said it is launching “regional working groups to help build countries' capabilities to measure food waste.” 

The researchers used food waste data from the 54 countries where it was available, including the United States and China. They then used that data, which was concentrated among high- and middle-income countries, to extrapolate estimated food waste in the rest of the world. 

The findings are particularly relevant to the ongoing fight against climate change, according to the researchers, because 8% to 10% of global greenhouse gas emissions are associated with food that is not consumed when losses before consumer level are taken into account. 

“If food waste were a country, it would be the third-largest emitter of greenhouse gases after the U.S. and China,” said Otto. “Food waste has been overlooked in national climate strategies.”

The U. N. wants countries to cut food waste in half by 2030, though researchers said achieving this goal will require serious changes to both consumer behavior and industry practices. Currently, the average household wastes about 11% of its total food, food service companies waste 5% and retail outlets like grocery stores waste 2%.

The findings also have relevance for world hunger. About 690 million people were hungry in 2019, and 3 billion people cannot afford a healthy diet, the researchers said. 

“Throwing away food means throwing away the resources that went into its production,” said Otto. “If food waste ends up in landfills, it does not only not feed people, it feeds climate change.” 

The paper represents a collaboration between academics, governments, nonprofits and commercial interests, and was written by Clementine O’Connor of the United Nations Environment Programme, as well as Tom Quested and Hamish Forbes of WRAP, which partners with companies including Coca-Cola, Nestlé and Google to address food sustainability issues. It was peer-reviewed by researchers from the U.N.’s Food and Agriculture Organization, Brazil’s governmental food and agricultural research corporation, the multinational sustainability consultancy group Anthesis, the University of Southern Denmark and the Johann Heinrich von Thünen Institute in Germany.  

The study, “UNEP Food Waste Index Report 2021,” published March 4 on the United Nations website, was authored by Clementine O’Connor, United Nations Environment Programme; and Tom Quested and Hamish Forbes, WRAP.