What we eat and how it is produced affects not only our health but also the environment. Food must be grown, processed, transported, distributed, prepared, consumed, and sometimes discarded. Each of these steps generates greenhouse gases that trap the sun's heat and contribute to climate change. Approximately one-third of all human-made greenhouse gas emissions are linked to food.

The largest share of food-related greenhouse gases comes from agriculture and land use. For example, methane from the digestive processes of cattle, nitrous oxide from fertilizers used in crop production, carbon dioxide from deforestation to expand farmland, fertilizer management, other agricultural emissions, rice cultivation, crop residue burning, and fuel use on farms all contribute to greenhouse gas emissions.

A much smaller share of food-related greenhouse gas emissions comes from industrial processes such as cooling and transporting food, producing materials like paper and aluminum for packaging, and managing food waste.

Which foods contribute how much to greenhouse gas emissions?

The climate impact of foods is measured in terms of greenhouse gas emission intensity. Emission intensity is expressed as kilograms of "carbon dioxide equivalents" per kilogram of food, gram of protein, or calorie – including not just CO2 but all greenhouse gases.

Animal-based foods, especially red meat, dairy products, and farmed shrimp, are typically associated with the highest greenhouse gas emissions. The reasons for this include:

– Meat production often requires large pastures created by cutting down trees, which releases carbon dioxide stored in forests.

– Cows and sheep release methane as they digest grass and plants.

– Waste from cattle on pastures and the chemical fertilizers used for crops grown as cattle feed emit nitrous oxide, another potent greenhouse gas.

– Shrimp farms are often associated with occupying coastal lands previously covered by mangrove forests, which absorb large amounts of carbon. The significant carbon footprint of shrimp is primarily due to the stored carbon released into the atmosphere when mangroves are cleared to create shrimp farms.

Plant-based foods such as fruits and vegetables, whole grains, beans, peas, nuts, and lentils generally use less energy, land, and water and have lower greenhouse gas intensities compared to animal-based foods.

– Emissions are measured in kilograms of carbon dioxide equivalent (kgCO2eq), which accounts for not only carbon dioxide but also other greenhouse gases such as methane and nitrous oxide, converted to their equivalent global warming potential.

How can food-related emissions be reduced? 

Reducing emissions from the food sector requires changes at all stages, from producers to consumers.

Shifting food systems toward plant-rich diets, focusing more on plant-based proteins (such as beans, chickpeas, etc.), can lead to significant reductions in food-related emissions where appropriate. Animal products remain a crucial source of food security, nutrition, and livelihoods for many rural populations worldwide. Improved feeds and feeding techniques can reduce the amount of methane produced during cattle digestion, as well as the gases released from decomposing manure. Better manure and fertilizer management, methods to preserve healthy soil for carbon storage, rotational grazing, and the restoration of degraded lands are examples of improved agricultural practices that can significantly help reduce greenhouse gas emissions.

At the same time, reducing food waste is crucial. Each year, approximately 1 billion tons of food — 17% of all food available to consumers worldwide — is thrown away. Producing, transporting, and allowing this food to decay contributes to more than 8% of global greenhouse gas emissions.

If food waste were a country, it would be the third-largest emitter of greenhouse gases in the world.

https://www.un.org/en/climatechange/science/climate-issues/food