Science for All newsletter: Food waste, a major contributor to climate change

In supreme irony, over 600 million people around the world experienced hunger in 2025.
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It produces five times the greenhouse gas emissions than does the aviation sector and it releases methane that accounts for no less than 10 per cent of all global greenhouse gases. The culprit is food waste, the result of excess production, spoilage or poor meal planning, said a recent report by the United Nations Environment Programme (UNEP).

According to the Food Waste Index Report 2024, a fifth of food available to consumers — or 1.05 billion tonnes — “is wasted either by being discarded at retail, in food service settings, or thrown away by households.” In fact, more than 1 billion meals are left uneaten every day, and 60 per cent of food waste comes from households. From here it ends up in landfills where it produces methane, which has contributed to a third of global warming to date: it traps 86 times more heat than carbon dioxide over a 20-year period, the UNEP report noted.

Methane is produced when organic matter such as uneaten food is buried in landfills, where it is deprived of oxygen and interacts with microorganisms.

But there is hope yet. While methane is a major air pollutant, it also breaks down much faster than carbon dioxide. For instance, when organic matter is composted in an oxygen-rich environment, it breaks down into carbon dioxide: “still a greenhouse gas but one that warms much less than methane over the short term,” said the report.

Flies to the rescue

There is another curious solution: flies. When bred, black soldier flies, in their larval stage, eat food waste thereby recycling it. Moreover, the flies die quickly and can in fact make high-protein animal food. Managment through black soldier flies is already being used in Uganda and Malawi, noted the report.

“… cutting emissions today from sources such as food waste can deliver climate benefits within decades, acting as an ‘emergency brake’ on global warming,” the report explained. That is the goal of UNEP’s Food Waste Breakthrough programme, which aims to halve food waste by 2030 and cut methane emissions by seven per cent.

But if no action is taken, food waste is expected to double by 2050. “At a time when the world is searching for practical ways to slow warming quickly, tackling food waste may be one of the most immediate and cost-effective climate solutions available,” Martin Krause, Director of the Climate Change Division at the UNEP was quoted as saying.

In supreme irony, over 600 million people around the world experienced hunger in 2025, according to the The State of Food Security and Nutrition in the World 2026 by the Food and Agriculture Organization . A fourth of the world’s population experienced moderate or severe food insecurity at the same time.