A combination of carbon, hydrogen, sulfur, oxygen, nitrogen, and other trace elements synthesised or originating from natural sources such as plants and animals. Human excreta, paper products, food, agriculture and much industrial wastes are all examples of organic compounds. The degradation of organic matter by organisms in soil release gases such as H₂S, NH₃, CH₄ and CO₂ the last two both important greenhouse gases because of their long atmospheric lifetimes and IR absorption characteristics.