Effects Of Different C/N Ratios On CO₂ And CH₄ Emissions And Humification In Aerobic Composting

Aerobic composting,as a more efficient way of agricultural waste resource utilization,still has some problems in the real process of production and utilization.Aiming at the secondary pollution caused by a large amount of carbon loss and the low quality of composting in the process of aerobic composting,this experiment adopted strip stacking composting,with five C/N treatments:T1?C/N=15?,T2?C/N=20?,T3?C/N=25?.T4?C/N=30?and T5?C/N=35?were used to determine the contents of TOC,DOC,THA,HA,FA,and the changes of CO₂ and CH₄emissions and cumulative emissions in different C/N aerobic composting processes in order to understand the transformation of carbon in different C/N aerobic composting processes and reduce composting losses.Secondary pollution in the process of composting,reducing carbon loss,optimizing composting parameters and improving the quality of compost products.The main results are as follows:1.The degradation of TOC during aerobic composting is mainly concentrated in the first 12 days of composting.The higher the initial C/N of the compost,the higher the degradation rate of TOC and the more serious the carbon loss.The results showed that the degradation of TOC in each treatment accounted for33.05%⁷3.94%of the total degradation in 12 days before composting,and the degradation rate of TOC in T1^T5 treatment was 40.98%⁵1.36%at the end of composting.The higher the C/N ratio,the higher the degradation rate of TOC and the more serious the carbon loss.The degradation rate of DOC decreased with the increase of C/N ratio in the compost.2.In the whole composting process,carbon loss in the form of CO₂ accounted for 21.90%⁴8.08%of total organic carbon loss,CH₄ 0.08%³.46%.When C/N was below 30,the total CO₂ emission flux increased with the increase of C/N,but the excessive C/N would inhibit its production.During the aerobic composting process,the peak periods of CO₂ and CH₄emissions were concentrated in the warming and high temperature periods,during which the emissions accounted for 80.38-90.29%and 90.00-107.00%of the total.In the whole composting process,carbon loss in the form of CO₂ accounted for21.90%⁴8.08%of total organic carbon loss,and CH₄ accounted for0.08%³.46%.When the initial C/N of the compost was between 15 and 30,the cumulative emission of CO₂ increased with the increase of C/N during the whole aerobic composting process,and the total emission of CH₄ gas was the lowest in T1treatment with the lowest C/N,which was only 1.45%in T4 treatment.When C/N>35,the cumulative emissions of CO₂ and CH₄ will decrease.This may be due to the high C/N ratio,the temperature of reactor and the duration of high temperature period will increase significantly,which will affect the reproduction and activity of microorganisms in the reactor,and thus inhibit the emission of carbon-containing greenhouse gases.3.The accumulation of total humic acid?THA?and humic acid?HA?,the stability of fulvic acid?FA?and the humification degree of compost products were better when C/N=20.THA loss rate was 25.03%³3.33%,HA loss rate was 4.00%¹5.58%and FA loss rate was 34.17%⁵7.66%in the whole aerobic composting process.Among them,the lowest loss rate of THA and HA was found in T2 treatment with C/N=20,and FA content decreased the most.When initial C/N>30,the degradation rate of THA and HA in the compost would be greatly increased and FA degradation would be inhibited.The four humification parameters of the products of T1 treatment with the lowest C/N ratio were at the lowest level in all treatments,indicating that the humification degree of the products was the lowest,and when the initial C/N ratio was 20,the humification degree of the products was the highest.4.Low C/N ratio will reduce the content and humification degree of various organic compounds in compost products,while high C/N ratio will aggravate the loss of carbon.During the whole composting process,the lowest C/N T1 treatment kept the lowest levels of all kinds of carbon-containing organic matter,and the lowest TOC,DOC,THA,HA content and humification degree were found in the products.The highest C/N T4 and T5 treatments have the highest content of all kinds of carbon-containing organic compounds in their products,but in the composting process,not only a large number of carbon-containing greenhouse gases will be emitted,but also the degradation of TOC,THA and HA in the compost will be aggravated,resulting in a large number of carbon losses.