Used coffee grounds are a rich source of healthful antioxidants

Maria-Paz de Peña and colleagues explain that people around the world drink millions of cups of coffee every day, generating about 20 million tons of used grounds annually. Although some spent coffee grounds find commercial use as farm fertilizer, most end up in trash destined for landfills. Coffee itself is a rich source of healthful antioxidants. De Peña's team wondered about the amount of antioxidants that remained in used coffee grounds from different coffee-making methods.

They found that filter, plunger and espresso-type coffeemakers left more antioxidants in coffee grounds, while mocha coffeemakers left the least. Because filter and espresso coffeemakers are more common in homes and commercial kitchens, the authors report that most grounds are likely to be good sources of antioxidants and other useful substances. They note that after these compounds are extracted, the grounds can still be used for fertilizer.