文摘
Biofiltration, whereby CH4 is oxidized by methanotrophic bacteria, is a potentially effective strategy for mitigating CH4 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 CH4 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 CH4 influx (13.9 g CH4 m鈥? h鈥?) 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 CH4 dose was doubled for a month, CH4 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 CH4 loads. Nitrous oxide emissions from the biofilters were negligible (maximum = 19.9 mg N2O m鈥? h鈥?) compared with CH4 oxidation rates, particularly from the volcanic soil that had a much lower microbial-N (75 mg kg鈥?) content than the compost-based filters (>240 mg kg鈥?). The high and sustained CH4 oxidation rates observed in this laboratory study indicate that a biofilter cover design is a potentially efficient method to mitigate CH4 emissions from dairy effluent ponds. The design should now be tested under field conditions.