A comprehensive review on the recent development of anaerobic sludge digestions: Performance, mechanism, operational factors, and future challenges

Abstract

After the industrial revolution, rapid population growth and burning fossil fuels led to the achievement of massive amounts of both liquid and solid waste, which can pose numerous threats for all compartments of environment. Anaerobic Digestion (AD) has been one of the most applicable techniques used during the last few decades to overcome the unpleasant presence of both organic fraction of waste and sewage sludge (SS), and as the result of this technique, biogas which is one of the main sources of energy can be produced. Therefore, the application of AD as a solution to overcome sludge and biodegradable fraction of solid waste has been the center of attentions since significant amounts of waste and sludge are being produced every day. In this regard a comprehensive review was conducted to know the advantages, disadvantages, various techniques that can improve methane yield, insights on the pretreatment methods, and operating factors was conducted to elucidate research gaps and future opportunities. Also, in the current study we discussed about operating conditions of single-stage digesters, two-stage digesters, anaerobic co-digestion. Our study is the first comprehensive review worked on the techniques by which we can improve methane yield from AD system.