The key components of coffee grounds can absorb sulfur.

There is good news for coffee lovers around the world: the large amount of coffee grounds they throw away helps remove the toxic smell of dirt. In the American Journal of Hazardous Materials, researchers at the City University of New York published a study saying that coffee grounds can absorb hydrogen sulfide gases, which are often caused by the fact that the dirt smells so bad. It is now a common practice to use activated carbon in treatment facilities to absorb hydrogen sulfides from the dirt. But if activated carbon is replaced with coffee grounds, it absorbs sulfur particularly well because of a key ingredient in coffee: caffeine. The researchers carbonized coffee grounds, water and zinc after a mixture of drying. Caffeine contains nitrogen, which increases carbon's ability to remove sulfur, said study author Teresa J. Bandosz, a chemist and chemical engineer at the City University of New York.