Biohydrogen production from buffalo manure codigested with agroindustrial by-products in an anaerobic reactor

Most on-farm biogas plants in Europe use animal waste and co-substrates for biogas production (CH₄ and CO₂ mixture). However combined hydrogen and methane production in a twostage process is a concept which has been developed in recent years and it is more promising from an energy perspective. The aim of this research was to explore hydrogen production from buffalo manure alone and in co-digestion with suitable feedstocks (low protein cheese whey and crude glycerol from biodiesel manufacturing). Experiments were carried out in batch reactor at 37 °C using a microbial consortia as inoculum. In a first set of batch trials the sterilization effect on hydrogen production from each individual substrate was explored. Results showed that sterilization increased hydrogen production yield (mL H₂/g VS) in all substrates, even reaching a three times higher yield in the case of buffalo manure. In a second set of experiments hydrogen production using different mixing ratios of sterilized substrates were investigated. Results showed that the hydrogen production yield from manure codigested with 10% glycerol or 10% of low protein cheese whey (LPCW), was increased from 37.7 mL H₂/g VS to 47.2 and 65.4, respectively. Moreover the co-digestion decreased H₂ production time from 114 hrs to 24 hrs. The yields further increased up to 116 mL H₂/g VS when a combination of 70% manure, 20% LPCW and 10% glycerol was used. During the experiments CH₄ was not detected. Buffalo manure, when codigested with LPCW and glycerol gave interesting yield together with an optimum buffering capacity avoiding the use of any external buffer/pH control system.