Emissions of ammonia and greenhouse gases during combined pre-composting and vermicomposting of duck manure

摘要

Combined pre-composting and vermicomposting has shown potential for reclamation of solid wastes, which is a significant source of ammonia (NH_3), and greenhouse gases (GHG), including nitrous oxide (N_2O), methane (CH_4), and carbon dioxide (CO_2). Earthworms and amendments may both affect physico-chemical characteristics that control gas-producing processes, and thus affect NH_3 and GHG emissions. Here, we used two-way ANOVA to test the effects of addition of reed straw and combined addition of reed straw and zeolite on NH_3 and GHG emissions during pre-composting of duck manure, either with or without a follow-up phase of vermicomposting. Results showed that cumulative N_2O, CH_4, and CO_2 emissions during pre-composting and vermicomposting ranged from 92.8, 5.8, and 260.6 mg kg~(-1) DM to 274.2, 30.4, and 314.0 mg kg~(-1) DM, respectively. Earthworms and amendments significantly decreased N_2O and CH_4 emissions. Emission of CO_2 was not affected by earthworms, but increased in responses to addition of reed straw. Cumulative NH_3 emission ranged from 3.0 to 8.1 g kg~(-1) DM, and was significantly decreased by reed straw and zeolite addition. In conclusion, combined pre-composting and vermicomposting with reed straw and zeolite addition would be strongly recommended in mitigating emissions of N_2O, CH_4, and NH_3 from duck manure. Moreover, this method also provides nutrient-rich products that can be used as a fertilizer.