Anaerobic digestion of crop residues: Technological developments and environmental impact in the Indian context

India is an agrarian country generating surplus amounts of paddy, wheat, and maize crop residues at large scale, which are not being managed properly. The anaerobic digestion is an efficient way of managing these residues in an environmentally friendly manner. It results in high calorific methane gas and fertile rich digestate. The current study focused on reviewing the availability, methane potential and technological developments to improve the methane production of crop residues. The methane potential from the anaerobic digestion of surplus paddy, wheat, and maize residues in India is estimated as 18,677 Mm3/year (632 × 109 MJ/year). The methane potential of crop residues could substitute 52 Mt/year of coal utilisation that evades 46 Mt/year of net CO2 emissions from releasing into the atmosphere.