Study On The Effects Of Additives On Physicochemical Performance And Bacterial Communities During Composting

Composting is a widely used method in treating agricultural solid wastes,which transform the biodegradable organic matter into stable humus-like products through the ubiquitous microorganisms under artificial control and aerobic conditions.During composting process,physicochemical parameters,the properties of dissolved organic matter and microorganisms community structure in compost habitat,would change with this process.These changes can be used as indicators to characterize the properties of composting piles directly or indirectly.In this study,twoseparate composting experiments were conducted to investigate the effects of bentonite andbiochar on the physicochemical properties of composting pilesand the effects of FGDG on the properties of dissolved organic matter and bacterial community structures.To explore the effects of these two inorganic additives(bentonite and biochar),the dynamic changes of physicochemical parameters(temperature,pH,moisture content,organic matter content,Kjeldahl nitrogen content,C/N ratio,NH4+-N and NO3--N concentrations)were monitoredand analyzed during the co-composting of dairy manure,mature fertilizer and sugarcane leaf.The obtained results showed that the addition of bentonite and biocharreduced water evaporation and retain the moisture in composting material.The bentonite caused a slight temperature drop in the initially stage compared to the control composting pile.On the contrary,the addition of biochar had no obvious effects on composting temperature.In addition,both bentonite and biochar increased the compost alkaline slightly,promoted the degradation of organic matter as well as reduced the nitrogen loss.These two additives might play a positive role in weakening the mineralization of nitrogenous organic compounds,which might cause the less nitrogen loss in respective composting pile.However,neither bentonite nor biochar had significantly effects onNO3--N concentration.In the end of composting,C/N ratio corresponded to the two standards,which means the addition of bentonite and biochar to the compost piles was anadvantagein improving composting maturity.This work also aimedto investigate the influences of flue gas desulphurization gypsum(FGDG)on the properties and evolution of dissolved organic matter(DOM)during the co-composting of dairy manure,sugarcane leaf and pressmud with the combination techniques of elemental analysis,particle size,zeta potential,UV-vis spectroscopy and FT-IR technology.The results revealed that FGDG amendment reduced the carbon loss and facilitated the nitrogen emission in compost DOM,increased the aromaticityof DOM and compost maturity,enhanced the absorbanceof-OH,-CHO,-COOH and C-O in polysaccharides.Additionally,FGDG amendment induced the growth of BacteroidetesandProteobacteria and inhibited the growth of Firmicutess and Chloroflexibased on Illumina sequencing.These findings provided new insights into the evolution and properties of DOMand microbial community during the composting process withFGDG amendment.