Pollution

Farm animal waste is choking rivers and oceans

By WhyStopHarmingAnimals.com

Animals have to eat, drink, pee and poop, and people breed and kill about 88 billion land animals a year for food[1]. Faunalytics, working from FAO data, counts 87.9 billion in 2024[1]. At that scale the waste is enormous. It washes off fields and out of feedlots into rivers and oceans, where it feeds the algae blooms that leave dead zones behind, stretches of water with too little oxygen for fish and other animals to survive.

Farms are the main source

Poore and Nemecek’s 2018 meta-analysis in Science found that food production causes about 78% of eutrophication, the nutrient pollution that suffocates rivers, lakes and coastal seas[2]. It also causes about 32% of the acidifying pollution that falls on land[2]. Most of that damage happens on the farm itself, through fertilizer on feed crops and the manure and urine of the animals. Our World in Data reports the same 78% figure for the share of global ocean and freshwater eutrophication caused by agriculture[2][3].

How much waste

In the United States alone, Burkholder and colleagues, writing in Environmental Health Perspectives in 2007 and citing EPA figures, estimated that farm animals produce about 133 million tons of manure a year on a dry-weight basis[4]. That is about 13 times the solid waste from human sewage in the country[4]. Farm animal manure is stored in lagoons and spread on fields, far more of it than the land can absorb, and the nitrogen and phosphorus it carries run off when it rains.

Water use and water pollution are linked. About 70% of the world’s freshwater withdrawals go to agriculture, and about 80% of agricultural land is used for grazing and feed[5]. When that water leaves the field, it carries the waste with it. Mekonnen and Hoekstra’s 2012 water-footprint study in Ecosystems found that the grey water footprints of meat and dairy, the water needed to dilute the pollution they cause, dwarf those of pulses and grains[6].

Food by food

Our World in Data’s chart of eutrophying emissions per 1,000 kilocalories, built from Poore and Nemecek’s data, puts beef, cheese and farmed fish at the top for water pollution[2][7]. Peas, nuts and potatoes sit near the bottom. Poore and Nemecek also found that even the lowest-impact animal products typically cause more pollution than vegetable substitutes[2]. The extra pollution comes from the animal: the feed it ate and the waste it left.

Diets show the same pattern. In a 2023 study in Nature Food, Scarborough and colleagues looked at the diets of about 55,000 people in the UK and found that vegan diets produced about 73% less water pollution than diets with 100 grams of meat a day or more[8], along with about 75% less greenhouse gas[8][9] and land use[8].

What the numbers cover

The 78% figure covers all of food production, including crops grown for people, so it is not a figure for farm animals alone. The food-by-food charts and the diet study show how much of it comes from animals[7][8]. The UK study is observational, based on what people reported eating, and the U.S. manure figure is a national estimate from 2007 measured by dry weight[4]. Each piece of evidence points the same way. The waste is a direct result of breeding animals in the tens of billions[1], and none of it was ever needed.