*4.2.5 Substrate particle size*

Pretreatment of biomass should be processed to reduce the particle size and then followed co-digestion to increase the biogas production [62, 112]. The substrate for anaerobic digestion has to be composed of digestible particle sizes. Smaller particles raise surface area for the microbial action of the methanogens as a result growing the biodegradability of the feedstock, hence raising the rate of biogas generation and vice versa for great particles which may clog the digester [96, 113, 114].
