Current challenges of high-solid anaerobic digestion and possible measures for its effective applications: a review

Abstract

The attention that high solids anaerobic digestion process (HS-AD) has received over the years, as a waste management and energy recovery process when compared to low solids anaerobic digestion process, can be attributed to its associated benefits including water conservation and smaller digester foot print. However, high solid content of the feedstock involved in the digestion process poses a barrier to the process stability and performance if it is not well managed. In this review, various limitations to effective performance of the HS-AD process, as well as, the possible measures highlighted in various research studies were garnered to serve as a guide for effective industrial application of this technology. A proposed design concept for overcoming substrate and product inhibition thereby improving methane yield and process stability was recommended for optimum performance of the HS-AD process.

Keywords: Anaerobic digestion; Challenges; High solids; Improved measures; Inhibition; Waste management.

Fig. 1

The AD Process through different degradation steps and trophic groups of microorganisms. 1 – Hydrolysis and Acidogenesis 2—Acetogenesis 3—Methanogenesis. Adapted from Schnürer and Jarvis [22]

Fig. 2

One Phase Batch Reactor Design with integrated heating and percolation liquid systems. BEKON System ( Adapted from BEKON [81])

Fig. 3

Reactor designs for adequate mixing of solid wastes; DRANCO System. (Adapted from Baere [81])

Fig. 4

Horizontal plug flow bioreactor design with inoculum recirculation; STRABAG System (Adapted from STRABAG [85])

Fig. 5

Vertical plug flow bioreactor design with biogas recirculation; VALORGA System (Adapted from Vandevivere, De Baere [83])

Fig. 6

Proposed Design for Limiting Inhibition in HS-AD Plants