Study On Composting Effect Of Earthworm Cooperative Treatment On Kitchen Waste And Agricultural Utilization

The waste of resources and environmental problems caused by the increase of kitchen waste and improper disposal methods have gradually attracted the attention of the society.It is an important way to make compost of kitchen waste and then return it to the field for agricultural utilization.Vermicomposting is a waste recycling process using earthworms to feed on organic debris.Compared with traditional aerobic compost,vermicomposting has advantages in improving the quality of compost and increasing the agricultural value of compost products.In addition,the optimized joint composting method has been becoming a research hotspot on the resource utilization of organic wastes in recent years.Kitchen waste has the characteristics of high oil,salt and water content.Composting alone is not conducive to the development of composting process and the survival of earthworms.The addition of auxiliary materials such as cow manure and wheat straw is helpful to optimize composting parameters and improve the composting effect and the growth of earthworms.Therefore,exploring suitable composting substrate and composting mode is an important way to optimize the composting process of kitchen waste in order to obtain higher resource utilization value.In this paper,kitchen waste was taken as the research object,cow manure and wheat straw were used as auxiliary materials for co-composting,and the effects of high temperature compost,pre-composting-vermicompost and high temperature compost combined with vermicompost on the maturation process and nutrient changes of kitchen waste were studied under different substrate ratios,and the compost products suitable for agricultural use were comprehensively analyzed and screened out.The emission rules of greenhouse gas and ammonia in different composting processes and the contribution of greenhouse gas emissions to greenhouse effect were explored.The effects of different dosages of earthworm manure on the growth and soil nutrients of Chinese cabbage were studied by pot experiment,and the agricultural effects and feasibility were evaluated.The following main research results and conclusions were obtained:（1）High temperature compost can meet the high temperature harmless standard of kitchen waste composting,but the quality of composting products is not good.Earthworm can enhance the mineralization and maturation process of compost,reduce the p H value and ammonium nitrogen and total nitrogen content of compost products,and improve the maturity of compost products and the mass fraction of nitrate nitrogen,total phosphorus,total potassium and total nutrients.Compared with pre-composting-vermicompost,high temperature compost combined with vermicompost can not only meet the high temperature harmless standards,but also improve the maturity and nutrient content of compost products（except total nitrogen）,and the compost products meet the agricultural industry standards of organic fertilizer.（2）The EC value,ammonium nitrogen,NH₄⁺-N/NO₃^--N ratio and total nitrogen content of compost products in substrate S_Ⅰ（kitchen waste:cow manure:wheat straw=3:1:1,w/w,dw）were always higher than those in substrate S_Ⅱ（kitchen waste:cow manure:wheat straw=2:2:1,w/w,dw）,while the p H,C/N and seed germination index were the opposite.From the perspective of earthworm growth,substrate S_Ⅱcan significantly improve earthworm survival and growth compared with substrate S_Ⅰ,and the high temperature compost combined with vermicompost significantly increased earthworm biomass compared with pre-composting-vermicompost（P<0.05）.（3）In the composting process,CO₂,CH₄ and NH₃ emissions mainly occurred in the early and high temperature stages of the high temperature compost stage,while N₂O emissions mainly occurred in the late stage of maturity.The total greenhouse gas CO₂emission equivalent was the highest in high temperature compost combined with vermicompost,followed by pre-compost-vermicompost,and the lowest in high temperature compost,among which the total greenhouse effect of substrate S_Ⅱcomposting treatment was always lower than that of substrate S_Ⅰ.The total greenhouse effect contribution is mainly CO₂,but earthworm inoculation can cause the increase in the emission of nitrogen related gases（N₂O and NH₃）,and the greenhouse effect caused by this can be further concerned.（4）The effects of earthworm manure on the growth and yield of Chinese cabbage showed a trend of first increasing and then decreasing with the increase of application amount.Compared with the single application of chemical fertilizer,the amount of chemical fertilizer reduced by 20%and the appropriate amount of earthworm manure（0.5%～1.0%）could effectively improve the growth,yield and phosphorus and potassium content of Chinese cabbage.The application of earthworm manure could reduce soil p H,increase soil EC value and nutrient content,and its effect increased with the increase of application amount.Excessive application of earthworm manure（2.5%～5.0%）can cause the decrease of Chinese cabbage yield and nitrogen and potassium content,resulting in excess soil nutrient,and the risk of pollution and salinization caused by high nitrate nitrogen and EC values.The Chinese cabbage with20%reduction of chemical fertilizer and application of 1.0%earthworm manure in kitchen waste had the highest yield,and the risk of excess nutrients,pollution and salinization was lower,which was a more suitable amount of earthworm manure for application.In conclusion,the cooperative treatment of earthworm compost is significantly better than that of high temperature aerobic compost,and the products of high temperature compost combined with vermicompost meet the national agricultural industry standard of organic fertilizer.Kitchen waste,cow manure and wheat straw are co-composted according to the dry weight ratio of 2:2:1 and the high temperature compost combined with vermicompost method has more advantages in the preparation of high-quality organic manure,earthworm culture and greenhouse gas emission reduction in the composting process,and the 20%reduction of chemical fertilizer and its compost products according to 0.5%～1.0%reasonable combination have a positive effect on the growth of Chinese cabbage and soil quality,which is a better composting mode of kitchen waste.The results of this study are helpful to systematically evaluate the effect and feasibility in utilization of kitchen waste of earthworms in composting.