title: Pilot-scale testing of a leachbed for anaerobic digestion of livestock residues on-farm.
abstract: A leachbed is a relatively simple anaerobic digester suitable for high-solids residues and on-farm applications. However, performance characteristics and optimal configuration of leachbeds are not well-understood. In this study, two 200 L pilot-scale leachbeds fed with spent straw bedding from pigs/swine (methane potential, B0 = 195-218 L CH4 kg(-1) VS fed) were used to assess the effects of leachate recirculation mode (trickling vs. flood-and-drain) on the digestion performance. Results showed comparable substrate solubilisation extents (30-45% of total chemical oxygen demand fed) and methane conversion (50% of the B0) for the trickling and flood-and-drain modes, indicating that digestion performance was insensitive to the mode of leachate flow. However, the flood-and-drain leachbed mobilised more particulates into the leachate than the trickling leachbed, an undesirable outcome, because these particulates were mostly non-biodegradable. Inoculation with solid residues from a previous leachbed (inoculum-to-substrate ratio of 0.22 on a VS basis) hastened the leachbed start-up, but methane recovery remained at 50% of the B0 regardless of the leachate recirculation mode. Post-digestion testing indicated that the leachbeds may have been limited by microbial activity/inhibition. The high residual methane potential of leachate from the trickling (residual Bo = 732 ± 7 L CH4 kg(-1) VS fed) and flood-and-drain leachbeds (582 ± 8 L CH4 kg(-1) VS fed) indicated an opportunity for further processing of leachate via a separate methanogenic step. Overall, a trickling leachbed appeared to be more favourable than the flood-and-drain leachbed for treating spent bedding at farm-scale due to easier operation.
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address: s.yap@awmc.uq.edu.au.
authors.forename: S D
authors.initials: SD
authors.lastname: Yap
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Astals
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: P D
authors.initials: PD
authors.lastname: Jensen
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Batstone
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Tait
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D008372:Manure / Q000032:analysis*; D008697:Methane / Q000032:analysis; D010865:Pilot Projects; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage / Q000737:chemistry*; D034421:Sus scrofa; D018505:Waste Management / Q000379:methods
chemical_list: D008372:Manure; D012722:Sewage; D008697:Methane
keywords: Anaerobic digestion; Inoculation; Leachbed; Manure; Solid-phase; Straw