A Review on Anaerobic Co-Digestion with a Focus on the Microbial Populations and the Effect of Multi-Stage Digester Configuration

Abstract

Recent studies have shown that anaerobic co-digestion (AnCoD) is superior to conventional anaerobic digestion (AD). The benefits of enhanced bioenergy production and solids reduction using co-substrates have attracted researchers to study the co-digestion technology and to better understand the effect of multi substrates on digester performance. This review will discuss the results of such studies with the main focus on: (1) generally the advantages of co-digestion over mono-digestion in terms of system stability, bioenergy, and solids reduction; (2) microbial consortia diversity and their synergistic impact on biogas improvement; (3) the effect of digester mode, i.e., multi-stage versus single stage digestion on AnCoD. It is essential to note that the studies reported improvement in the synergy and diverse microbial consortia when using co-digestion technologies, in addition to higher biomethane yield when using two-stage mode. A good example would be the co-digestion of biodiesel waste and glycerin with municipal waste sludge in a two-stage reactor resulting in 100% increase of biogas and 120% increase in the methane content of the produced biogas with microbial population dominated by Methanosaeta and Methanomicrobium.

Hydrogen and Methane Production Under Conditions of Anaerobic Digestion of Key-Lime and Cabbage Wastes

“…Neutral conditions of investigation allowed to assess availability of the substrates for hydrogen production and methane without special pretreatment or other unit operation that increases costs of the research. The initial conditions (neutral pH) are usually more suitable for methane production (Rabii et al, 2019) than hydrogen production. However, dark fermentation for some substrates in nonacidic pH can give high volumes of hydrogen like Li et al (2018) Klebsiella sp.…”

A Review on the Fate of Nutrients and Enhancement of Energy Recovery from Rice Straw through Anaerobic Digestion

“…Co-digestion offers various advantages like improved system stability, adjusted C/N ratio, a better nutrient balance, dilution of toxic compounds, improved buffer capacity, increased biodegradation, adjusted moisture content, a supply of TEs, and increasing OLR. It can therefore, enhance volumetric biogas recovery [61][62][63] and improves the fertilizer value of the digestate [64]. These advantages of co-digestion are presented in Figure 6.…”

Analysis of Microbial Consortia with High Cellulolytic Activities for Cassava Pulp Degradation

“…In hydrolysis, microorganisms in a consortium secrete cellulolytic enzymes to convert the macromolecular compounds to micromolecules and monomers that subsequently converted to biogas or other products. In fact, the production rate and efficiency of cellulolytic enzymes depend on various factors, especially working condition of hydrolysis process, including temperature, pH, as well as nutritional value [7].…”