Indigenous microbial capability in solid manure residues to start-up solid-phase anaerobic digesters. (June 2017)

• Record Type: Journal Article
• Authors: Yap, S.D.; Astals, S.; Jensen, P.D.; Batstone, D.J.; Tait, S.
• Is Part Of: Waste management. Volume 64(2017)
• Page Start: 79
• Page End: 87
• Publication Date: 2017-06
• Subjects: Anaerobic digestion -- Microbial community -- Manure -- Straw -- Inoculum -- Biological inhibition; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2017.02.031
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: Livestock residues are both an inoculum and a substrate for anaerobic digestion. The native microbial community recovered the full methane potential. Thermophilic conditions increased failure risk without enhancing performance. Inoculation with residue from a previous batch expedited the start-up. Inhibitors are important at high solids and when inoculating with residues. Abstract: Batch solid-phase anaerobic digestion is a technology for sustainable on-farm treatment of solid residues, but is an emerging technology that is yet to be optimised with respect to start-up and inoculation. In the present study, spent bedding from two piggeries (site A and B) were batch digested at total solids (TS) concentration of 5, 10 and 20% at mesophilic (37 °C) and thermophilic (55 °C) temperatures, without adding an external inoculum. The results showed that the indigenous microbial community present in spent bedding was able to recover the full methane potential of the bedding (140 ± 5 and 227 ± 6 L CH4 kgVSfed −1 for site A and B, respectively), but longer treatment times were required than for digestion with an added external inoculum. Nonetheless, at high solid loadings (i.e. TS level > 10%), the digestion performance was affected by chemical inhibition due to ammonia and/or humic acid. Thermophilic temperatures did not influence digestion performance but did increase start-up failure risk. Further, inoculation of residues from the batch digestion to subsequent batch enhanced start-up and achieved full methane potential recovery of the bedding. Inoculation with liquid residue (leachate) was preferred over a solid residue, to preserve treatment capacity for fresh substrate. Overall, the study highlighted that indigenous microbial community in the solid manure residue was capable of recovering full methane potential and that solid-phase digestion was ultimately limited by chemical inhibition rather than lack of suitable microbial community.