The key components of coffee grounds can absorb sulfur.

Coffee lovers around the world have some good news: The amount of coffee grounds they throw away helps remove the toxic smell of dirt. Coffee grounds can absorb hydrogen sulfide gases, which are often responsible for the foul smell, researchers at the city university of new york report in the american journal hazardous materials. It is now common practice to use activated carbon in treatment facilities to absorb hydrogen sulfide from contaminants. But if you replace activated carbon with coffee grounds, it adsorbs sulfur especially well because of a key ingredient in coffee: caffeine. Researchers mixed coffee grounds, water and zinc, dried them and carbonized them. Caffeine contains nitrogen, which increases carbon's ability to eliminate sulfur, said Teresa J. Bandosz, a chemist and chemical engineer at the City University of New York and study author.