Rabbit manure as a potential inoculum for anaerobic digestion

The potential of using rabbit manure as inoculum for biogas production was evaluated through batch assays using bean straw as substrate. The microbial diversity in the rabbit manure included lignin-degrading bacteria (classes Bacteroidia, Bacilli and Clostridia) as well as key acetoclastic (Matheanosarcina and Methanosaeta), and hydrogenotrophic (Methanobacterium, Methanolinea, and Methanovebribacter) archaea. The effects of particle size, substrate to inoculum ratio (S/X) and pH adjustment were studied to improve the inoculum activity. The adjustment of the pH entailed the highest improvement in methane production (515%) and rate (164%). However, high S/X, (3–4), resulted in the acidification of the processes, denoting an imbalance between hydrolytic bacteria and methanogenic archaea in the rabbit manure. This confirmed that the use of rabbit manure as inoculum could sustain anaerobic digestion from agricultural residues, although a proper enrichment and adaptation is necessary to ensure an appropriate methane production.