Cow dung is also useful for mankind as it contains methane, nitrogen, phosphorous, etc. These elements help in the production of fuel or biogas. Cow dung is often used as a fertilizer in farming because it is actually a naturally rich fertilizer. Additionally, it is also used as an insect repellent after it has been burnt. In rural India, the use of cow dung is very common as biogas in the kitchen and as fertilizer in the fields.