The average horse produces nearly nine tons of manure a year—that’s a lot of poop! But did you know that all this manure could be both hindering and helping the environment?

Global warming is partly the effect of livestock production: grass-fed animals produce a digestive gas known as enteric methane, which contributes to the greenhouse effect, said William Martin-Rosset, PhD, head of equine nutrition research at the French National Institute for Agricultural Research (INRA) in Saint-Genès-Champanelle. But it’s not all bad news: The compounds and minerals in equine manure can provide an excellent source of organic fertilizer as well as renewable energy, establishing the horse as a worthwhile contributor to sustainable development and a healthy planet, he said at the 2013 French Equine Research Day, held Feb. 28 in Paris.

Martin-Rosset and colleagues investigated equine enteric methane release, as well as horses’ production of nitrogen, calcium, potassium, and other potentially harmful minerals through urine and feces. The researchers also looked into environmentally-friendly uses of equine manure.

Cattle produce about 90% of the enteric methane in France (which contributes to 3-5% of France’s global warming) while horses produce only 1.5% of the nation’s methane, Martin-Rosset said. An average horse produces 20.7 kilograms (45.5 pounds) of methane gas per year—just a fraction of what cows produce annually. A lactating draft horse mare, for instance, will only release 34% of the methane released by a lactating dairy cow, he said.

The team also estimated that in a single year, the average horse