heir exams. • Traditionally, biomass had been utilized through direct combustion. Cow dung cake is one of the most important and widely used biomass for the production of daily energy needs. It has been estimated that 2.5 billion people around the world are not being able to access modern fuels. They are highly dependable on locally available wood and cow dung cakes. • About nine-tenth of the rural households in India uses traditional biomass-wood and dung-as a household fuel annually. Burning of biomass or cow dung cakes through direct combustion creates indoor air pollution and ultimately contributing to serious health problems, particularly cancer and respiratory infections. • Approximately half a million premature deaths and nearly 500 million cases of illness are estimated to occur annually as a result of exposure to smoke emissions from biomass use by households in India, making indoor pollution the third leading health risk factor. • Biogas represents a renewable source of energy that derives mainly from the decomposition of organic wastes in the absence of oxygen. In India, biogas mainly produced from cattle dung.