Electric Field Enhances The Maturity Of Aerobic Composting And Mitigates N₂O Emissions

The number of livestock wastes has been increasing recent years with the economic development and improvement of people's living standard.On the one hand,the livestock wastes contain parasitic worm,pathogenic microorganisms and heavy metals?such as Zn,Cu?and other harmful substances,which poses a serious environmental.On the other hand,livestock wastes are also an important resource rich in various organic matters,nitrogen,phosphorus,potassium and other fertilizer element.Aerobic composting has been suggested as an efficient method for livestock wastes.However,the conventional aerobic composting?CAC?has some disadvantages,such as low temperature,long fermentation period and poor effect of decomposition,especially in releasing large amount of greenhouse gas.In particular,CAC has become an important source of global agricultural emissions of nitrous oxide?N₂O?.It poses a serious environmental pollution as the emissions may cause global warming and nitrogen loss.Therefore,how to deal with the problems of maturity and N₂O emission during conventional aerobic composting are important.Recently,there is a novel technique--electric field to aerobic composting?EAAC?has been applied and evaluate its effects on compost maturity and N₂O emissions.Two groups of identical reactors with the same chicken manure composting were built:one group was applied with a low direct current?DC i.e.?2 V?0.05-0.5 V/cm?,while the other group was used as control.The results showed that electric field could accelerate the process of composting maturity and shorten fermentation period than conventional composting.The seed germination index?GI?of the EAAC was 124%by day 30 higher than CAC was 99%.Through the analysis of spectroscopy,it was concluded that the electric field can enhance the aromatic structure of composting humus and promote the stabilization of composting,indicating that the EAAC can improve composting maturity,and shorten the period about 33%.In addition,the electric field-assisted could reduce N₂O emission more than 82.9%.Finally,we preliminarily explored the mechanism of composting maturity and N₂O emission by electric field.The results showed that the electric field could promote the growth of electroactive microorganisms and inhibit the growth of nitrifying and denitrifying microorganisms.The rate of oxygen consumption showed that the electric field can enhance the electron flow and utilization rate of O₂,promote composting ripening and inhibit the generation of N₂O.Compared with the CAC,the EAAC has the obvious advantages of fast starting temperature,short cycle and low N₂O emission,and has a potential application.However,the mechanism of electric field on composting is still unknow.How does the electric field affect the N₂O emission.How dose electric field affect microbes,functional genes,water or ion migration,and so on.The findings of this study provide insights into the mechanisms behind N₂O mitigation in EAAC,and contribute to the development of a new aerobic composting technology for organic solid waste.