title: Testing a biofilter cover design to mitigate dairy effluent pond methane emissions.
abstract: Biofiltration, whereby CH(4) is oxidized by methanotrophic bacteria, is a potentially effective strategy for mitigating CH(4) emissions from anaerobic dairy effluent lagoons/ponds, which typically produce insufficient biogas for energy recovery. This study reports on the effectiveness of a biofilter cover design at oxidizing CH(4) produced by dairy effluent ponds. Three substrates, a volcanic pumice soil, a garden-waste compost, and a mixture of the two, were tested as media for the biofilters. All substrates were suspended as 5 cm covers overlying simulated dairy effluent ponds. Methane fluxes supplied to the filters were commensurate with emission rates from typical dairy effluent ponds. All substrates oxidized more than 95% of the CH(4) influx (13.9 g CH(4) m(-3) h(-1)) after two months and continued to display high oxidation rates for the remaining one month of the trial. The volcanic soil biofilters exhibited the highest oxidation rates (99% removal). When the influx CH(4) dose was doubled for a month, CH(4) removal rates remained >90% for all substrates (maximum = 98%, for the volcanic soil), suggesting that biofilters have a high capacity to respond to increases in CH(4) loads. Nitrous oxide emissions from the biofilters were negligible (maximum = 19.9 mg N(2)O m(-3) h(-1)) compared with CH(4) oxidation rates, particularly from the volcanic soil that had a much lower microbial-N (75 mg kg(-1)) content than the compost-based filters (>240 mg kg(-1)). The high and sustained CH(4) oxidation rates observed in this laboratory study indicate that a biofilter cover design is a potentially efficient method to mitigate CH(4) emissions from dairy effluent ponds. The design should now be tested under field conditions.
authors.affiliation: Landcare Research - Manaaki Whenua, Riddet Road, Palmerston North, New Zealand. C.Pratt1@massey.ac.nz
authors.forename: Chris
authors.initials: C
authors.lastname: Pratt
authors.forename: Julie
authors.initials: J
authors.lastname: Deslippe
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Tate
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000378:metabolism*; D000397:Air Pollution / Q000517:prevention & control*; D056804:Biofuels / Q000032:analysis; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism; D003612:Dairying; D005374:Filtration / Q000295:instrumentation* / Q000379:methods; D008697:Methane / Q000032:analysis / Q000378:metabolism*; D009609:Nitrous Oxide / Q000032:analysis / Q000378:metabolism; D010084:Oxidation-Reduction; D016062:Porosity; D017640:Silicates; D012987:Soil; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods
chemical_list: D000393:Air Pollutants; D056804:Biofuels; D017640:Silicates; D012987:Soil; D002245:Carbon Dioxide; D009609:Nitrous Oxide; C005144:pumice; D008697:Methane