16 - Solid state anaerobic digestion of organic waste for the generation of biogas and bio manure

Abstract

Anaerobic digestion (AD) is an environmentally benign and economically viable process for the treatment of organic wastes for the generation of added value products such as bio gas, volatile fatty acids, bio hydrogen, alcohols and bio manure. AD is classified into two types, namely wet AD (WAD) and solid-state AD (SSAD) depending on the total solid's concentration in feedstock. Wet AD is widely accepted and implemented at full-scale globally for the concomitant treatment and generation of biogas and bio manure but SSAD is still emerging. Although SSAD has numerous advantages over Wet AD, but its implementation in real field is only feasible when the techno-economic viability of the process is established. Biomethanation of wastes containing high solids such as agricultural waste, MSW through SSAD is a feasible approach but the limitation of pre-treatment needs to be addressed to make the process economically feasible. This chapter details about the classification of AD based on different factors and the merits and demerits of Wet AD and SSAD. Advantages of the SSAD include less consumption of water content in the feed stock and the moisture in the digestate is very less compare to WAD, in addition to this it is more advantageous in terms of reactor volume, substrate handling, methane yield and requirement of energy. Handling of raw substrate which is having high TS such as agriculture waste, MSW, household waste and so on is more suitable in SSAD compare to WAD. In this chapter various aspects related to SSAD are discussed with following contents.