Integration of biohydrogen, biomethane and bioelectrochemical systems

Anaerobic bioprocesses such as Anaerobic digestion (AD), fermentative biohydrogen (BioH ₂), and Bioelectrochemical system (BES), converting municipal, agro-industrial wastes and crops to energy have attracted accelerating interest. Anaerobic digestion (AD) however, still requires optimisation of conversion efficiency from biomass to methane. Augmenting methane energy production with simultaneous BioH ₂ and bioelectrochemical stage(s) would increase process efficiencies while meeting post treatment effluent quality. Pre-treatment of feedstock increase bacterial accessibility to biomass, thus increasing the conversion yield to target product, but an alternative is separating the acidogenic/hydrolytic processes of AD from methanogenesis. Acidogenesis can be combined with BioH ₂ production, prior to methanogenesis. Depending on operating conditions and without further treatment after digestion, the methanogenic stage may discharge a digestate with significant organic strength including volatile fatty acids (VFAs). To meet wastewater discharge consents; adequate use of digestates on land; to minimise environmental impact and; enhance recovery of energy, VFAs should be low. Concatenating bioelectrochemical systems (BES) producing hydrogen and/or electricity can facilitate effluent polishing and improved energy efficiency. Various configurations of the BioH ₂, methanogenesis and BES are plausible, and should improve the conversion of wet biomass to energy.