Abstract
The slaughterhouse waste (SHW) contains high organics which makes SHW a feasible feedstock for anaerobic digestion (AD). The present study systematically assessed the microbiome response and biomethanation along with the production of volatile fatty acids (VFAs) and ammonia under 2%, 4%, 6%, and 8% (w v-1) loadings of SHW in AD. The optimum loading was 2% SHW which resulted in maximum biomethane production and VFAs consumption. A higher SHW concentration (4% and 6%) resulted in a prolonged lag-phase and decreased biomethane production. High VFAs (28.88 g L-1) and ammonia nitrogen (>4 g L-1) accumulation were observed at 8% SHW leading to permanent inhibition of biomethane and methanogenic archaea. An increase in ammonia and VFAs concentration, at 4% and 6% SHW loadings, shifted the methanogenic pathway from acetoclastic to hydrogenotrophic lead by Methanoculleus. Acetoclastic Methanosaeta (77.15%) dominated the reactors loaded with 2% SHW resulting in the highest biomethane production.