What are the two ways in which cow-dung can be used as a fuel? Which of them is better and why?

The two ways in which cow-dung can be used as a fuel are as follows:

1. In the form of "cow-dung cakes", which can be used directly as a fuel for cooking food.

2. In the form of "Biogas" which can be used as a smokeless fuel.

Biogas is better than cow-dung cakes as it does not cause air pollution, and after extracting biogas, the cow dung can still be used as manure because it continues to retain all the nutrients that plants need.

Explanation

Biogas is the mixture of gases produced by the anaerobic bacterial decomposition (decomposition without oxygen) of organic matters. It comprises primarily methane (CH4) and carbon dioxide (CO2) and a trace amount of hydrogen sulphide (H2S), ammonia (NH3), oxygen and nitrogen.

It is a clean and renewable energy source, which can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste.