Research On Ultra High Temperature Compost Process And Nitrogen Loss During Vegetable Waste Composting

During the adjustment of agricultural structure in China,the amount of vegetable wastes increased gradually due to the increased cultivated area and vegetable crop yield.Currently,it remains challenging to treat and recycle these vegetable wastes effectively and safely due to the lack of suitable technique.There is an urgent need to develop a composting technology for vegetable wastes in order to ensure the sustainable development of vegetable industry.Hence,this study aimed(i)to develop an optimal composting technology system for vegetable waste(cucumber stalk)by investigating the influence of various factors,i.e.,the bulk density of initial material(0.30,0.35,0.40 kg·L-1),easily-degraded organic matter content of the initial material(27%、36%、45%、51%of dry matter)and the use of microbial agent on ultra high temperature composting,(2)to explore the relationships between ultra high temperature and the transformation and loss of nitrogen,and(3)to analyze the effects of various in-situ nitrogen loss controlling methods on reducing nitrogen loss.The main results were summarized as below:(1)Key technologies for achieving optimal composting for vegetable waste(cucumber stalk)were:adjusting the bulk density of initial composting mix to 0.35 kg·L-1,and easily-degraded organic matter content at 45%,with which the highest temperature could be above 70℃ using microbial agent to promote the lignin degradation and to increase the temperature and thermophilic period,however,keeping the temperature lower than 75 ℃,or the lasting time at 75 ℃ should be less than 24 hours(when longer than 24 hours,the inhibitory effect will be limited and the restore time will be longer).(2)When adjusting the initial material character,the bulk density of 0.30 kg-L"1 and the easily-degraded organic matter content of 45%both increased the NH3 emission amount,compared to other conditions.In addition,the NH3 emission increased with the temperature when the initial materials were the same.(3)The nitrogen loss rate was 26.12%during ultrahigh temperature composting for vegetable waste,while microbial agent addition would promote the nitrogen transformation and NH3 emission,resulted in a nitrogen loss rate of 33.00%.NH3 emission accounted for more than 90%of total nitrogen loss.(4)The three controlling methods used in this study all could effectively reduce the nitrogen loss when compared with CK.In general,woody peat addition was more efficient in reducing ammonia emission(57.54%)and nitrogen loss(54.23%),compared to the K2HPO4 and MgO addition(27.93%and 27.50%)and intermittent aeration(24.17%and 16.12%),but it influenced the ultrahigh temperature realization.All three methods could promote the maturity,shorten the composting cycle and finally reduce NH3 emission and nitrogen loss.Based on the results mentioned above,adjusting the bulk density of initial material to 0.35 kg·L-1 and easily-degraded organic matter content at 45%,together with microbial agent and struvite-based addition(K2HPO4 and MgO),vegetable wastes(cucumber stalk)could be safely and effectively transformed into high quality product by composting for more than 7 days.