Mitigation of greenhouse gas emission from the cattle manure composting process by use of a bulking agent(Mitigation of methane and nitrous oxide emissions from livestock waste management)

概要

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The greenhouse gas (GHG) [methane (CH_4) and nitrous oxide (N_2O)] mitigation effects of mixing dried grass into passively-aerated manure during the composting process (which accounts for 68.7% of Japanese dairy manure management) were assessed. Gaseous emissions [CH_4, N_2O, carbon dioxide (CO_2) and ammonia (NH_3)] from about 4t of fresh dairy manure with or without 400kg of dried grass mixed in were measured by the dynamic chamber method. The addition of dried grass contributed to a decrease in GHG emissions from 20.8±1.3 gkg^<-1> volatile solids (VS) to 5.4±1.4gkg^<-1> VS (74.3% mitigation) for CH_4 and from 7.4 ± 2.6g N_2O-N kg^<-1> Ninitial to 2.7 ± 0.4g N_2O-N kg^<-1> Ninitiai (62.8% mitigation) for N_2O. By applying this strategy, the expected reduction of GHG emission would be 70,466t CH_4 yr^<-1> and 1379t N_2O-N yr^<-1> (1907 Gg CO_2 eq. yr^<-1> in total) in the Japanese dairy sector. On the other hand, it was showed that CO_2 and NH_3 emissions increase [from 424.4 ±214.9 g CO_2 kg^<-1> VS to 603.8 ± 99.6 g CO_2 kg^<-1> VS for CO_2 and from 16.9 ± 7.1 g ammonium-nitrogen (NH3-N) kg^<-1> Ninitiai to 38.3 ± 3.5 g NH3-N kg^<-1> Ninitiai for NH_3] by this method. Moreover, the mechanism of this significant N_2O mitigation effect cannot be explained, and a better understanding of this effect could further improve the GHG mitigation strategy.