Study On The Improvement Of Green Waste Composting Technology And The Effect Of Compost Application

Composting is the main way to utilize green waste resources at present.However,the traditional composting method exists the problems of low humification and poor quality,which limits the market value and application of compost products.In order to improve the composting quality and utilization rate of green waste,this research took green waste as the research object,using high-throughput sequencing,FTIR spectra,principal component analysis,cluster analysis and other technical means and statistical methods to conduct research.Firstly,simulated fermentation experiments were carried out under different particle sizes and C/N ratios to screen out the optimal initial composting conditions and explore the formation mechanism of humus in composting.Secondly,bean dregs,tea residue and biochar were selected as exogenous precursor additives in outdoor composting experiment for evaluating the control effect of exogenous precursor organic matter on humification process,then selected the optimal compost by combining the effects of organic matter degradation and gas emission reduction;Finally,the effects of composting on soil improvement and plant growth were further evaluated through plant planting experiments,and the feasibility of using green waste compost instead of peat as soil improvement substrate was discussed.The main conclusions are as follows:(1)The results showed that 2mm particle size and low C/N ratio(C/N = 23)were more conducive to composting temperature,and significantly improved the germination index,humic substance content and degree of polymerization of compost products.The ratio of the aromatic carbon structure of the humus to the absorption peak intensity of the main functional group of the precursor increased.Pseudoxanthomonas of Proteobacteria and Thermobacillus and Bacillus of Firmicutes can promote the degradation of organic matter and the formation of humic substance precursor(amino acids,soluble sugars,carboxyl and polyphenols).Total nitrogen,organic matter,microbial diversity and HS precursors are key factors affecting the formation of humic substance.(2)The addition of exogenous precursors(bean dregs,tea residue and biochar)alone or in combination can prolong the duration of thermophilic phase of the reactor,improve the cation exchange capacity and germination index of compost,optimize the physical structure of compost,improve the enzyme and microbial activity,increase the quantity of HS precursor and promote the formation of humic substance,which is conducive to the transformation of aliphatic compounds to stable aromatic structure,and the composting has the advantages of higher degree of humification and stability.According to the humification indexes,T6 added with bean dregs,tea residue and biochar was the highest treatment.(3)The addition of bean dregs,tea residue and biochar alone or in combination increased the degradation amount and rate of organic matter,promoted the degradation and transformation of lignocellulose,increased the content of total nitrogen and nitrate nitrogen in compost,and had lower nitrification coefficient;tea residue and biochar could reduce ammonia emission and increase nutrient retention,and biochar had the best control effect on gas emission.Enhaning organic matter degradation and ammonium nitrogen fixation were beneficial to humic substance formation." Bean dregs + Tea residue + Biochar" as an exogenous additive has the best effect of promoting humification and reducing emissions.(4)Composting can improve soil physi-chemical properties,also promoted plant growth,T6 compost has the best application effect.Using compost instead of peat as organic matrix can improve soil aeration,cation exchange capacity and nutrient content.Composting can effectively improve the contents of total nitrogen,total potassium and chlorophyll of plants,and promote the growth of aboveground parts of plants better than peat,while peat is more conducive to the accumulation of total phosphorus and underground biomass.R4(15% peat + 35% compost)had the highest comprehensive evaluation index of aboveground growth and root morphology.The results of principal component analysis showed that R4 which mixed15% peat and 35% compost had the highest score,then the score of R5 was higher than that of R1.Therefore,it is feasible for compost to partially or completely replace peat as organic improvement matrix.This study discussed the formation mechanism of humic substance in green waste compost,proposed a method to improve the humification degree of compost by adding exogenous precursors organic matter,and discussed the feasibility of compost products replacing peat as organic improvement matrix and the optimal replacement ratio,formed the basic theory and technical method of green waste compost resource utilization.