Effective Pre-Treatments for Enhancement of Biodegradation of Agricultural Lignocellulosic Wastes in Anaerobic Digestion – A Review

Agricultural crop residues like stems, straws and leaves are valuable resources for biofuel production, especially methane, due to anaerobic digestion. Biogas from agricultural lignocellulosic wastes is capable of attaining sustainable energy yields without environmental pollution. Farmers in many developing countries burn these wastes throughout their fields, imposing environmental hazard due to emission of greenhouse gases. The main problem in this field is the recalcitrance of the agricultural lignocellulose waste that limits its enzymatic degradation and hydrolysis efficiency and consequently decreases biogas production. Therefore, efficient pre-treatments prior to anaerobic digestion are essential. Various pre-treatment methods are used for increasing the anaerobic digestibility of lignocellulose biomass, such as physical (mechanical, thermal, etc.), chemical, biological and combined pre-treatments. This paper reviews different pre-treatments used in anaerobic digestion for the agricultural lignocellulosic wastes and explains the advantages and disadvantages of each. The most frequently used pre-treatments for main agricultural wastes in process of biogas production are also introduced.