Biogas as an alternative to stubble burning in India

Crop residue management and curbing stubble burning is of global interest. For every tonne of rice harvested, approximately 1.4 tonnes of straw is left behind on the crops and a similar proportion applies for the other major crops as well. Direct on-farm burning remains the most common method in India to manage these huge volumes of crop residues. Generating biogas from the crop wastes could be an effective and environment friendly alternative. Biogas is a renewable source of energy, offers controlled waste management along with reducing greenhouse gases and harmful pollutants. The digested sludge when used as an organic fertiliser even completes a sustainable loop of recycling nutrients back into the soil. Crop residues due to their rich organic content have demonstrated excellent biogas potential. Most energy crops have shown methane yields of approximately 300 m/t of organic matter. This gas could be used as a fuel or converted to electricity or even upgraded to bio-methane. To further optimise the process, different types of pre-treatment methods and co-digestion of the substrates have been identified. The current article aims at providing a perspective on the impact of stubble burning and replacing the practice by producing biogas instead, thus, providing information on the potential, limitations and methods for optimising methane generation from the crop residues.