Effect Of Biochar On The Aerobic Composting Process Of Pig Manure Or Sewage Sludge And The Changes Of Its Physical And Chemical Properties During Composting

Biochar is a kind of rich carbon rich solid with strong pore structure,large specific surface area,rich functional groups and strong chemical adsorption capacity.It has good thermal stability and anti biochemical decomposition characteristics.In recent years,biochar has been paid much attention as a conditioner in compost process.However,the current research focuses on the acceleration of biochar to the process of composting and the improvement of the quality of the composting products.There are few reports about the changes of physicochemical properties of biochar before and after the composting.In this study,pig manure and sludge were used as the raw materials for composting,and5%and 10%biochar were added to the heap to study the influence of the biochar on the aerobic composting process.By measuring the changes in the morphology and surface characteristics of biochar,the biochar in the process of different matrix composting was studied to clarify the process of biochar and composting.The mechanism provides a scientific basis for the application of biochar in compost.The main conclusions are as follows:（1）Compared with the control,the biochar made the maximum temperature of the heap up to 1²d in advance,the high temperature period extended 1³d,the pH value of the heap increased 0.11⁰.24,the conductivity decreased 0.14⁰.23mS·cm^-1,the water content decreased 1.3%⁷.6%.Except for the time of water content and maximum temperature,all the other indicators showed that the more amount of biochar added,the more obvious the effect was.Compared with the sludge compost,the maximum temperature of the pig manure composting was 1²d,the highest temperature was0.1².1℃,the duration of the high temperature period was 3d,the pH value and the electrical conductivity increased,while the water content and the seed germination index decreased.（2）On the 0²1d of composting,the decrease of organic carbon in sludge compost accounts for more than 80%of the total decline,and the drop of pig manure is only about 40%of the total decrease.Adding bio carbon can increase the organic carbon content of the heap,reduce the loss rate of organic matter in the composting of pig manure,and the more the loss rate of organic matter is added,and the biochar increases the sludge.The organic matter loss rate and organic matter loss rate of composting were5%biochar>10%biochar>control.The water soluble organic carbon in the sludge composting was first rising and then decreasing,while the water soluble organic carbon of pig manure was decreased first and then decreased.In addition to the control,the content of soluble organic carbon in the high temperature period was improved effectively,and the content of soluble organic carbon in the later period was obviously reduced,except for the treatment of pig manure 5%biochar.It indicates that biochar is beneficial to the utilization of soluble organic carbon at maturity stage.Compared with the control,biochar reduced the content of humic acid,humic acid and fulvic acid by 13.0-25.4,7.4-14.9 and 5.6-10.5g/kg respectively,the more effective of biochar addition,indicating that biochar was beneficial to the decomposition and synthesis of heap humus,and to deepen the maturity of the heap.The humification index of compost with mud as substrate is higher than that of pig manure compost.（3）At the end of the composting,the ammonium nitrogen content of the pig manure added with 5%and 10%biochar decreased by 20.6%and 35.7%,the nitrate nitrogen increased 19.9%and 24.1%respectively,and Kjeldahl nitrogen increased 2.1%and 5.6%,respectively,and the ammonium nitrogen content of the sludge heap decreased 32.2%and 41.6%respectively,and nitrate nitrogen increased 16.9%and33.9%,Kjeldahl nitrogen,respectively.The content increased by 9.4%and 11.9%,respectively.The results show that biochar can promote the transformation of ammonium nitrogen to nitrate nitrogen and increase the nitrogen content of the heap.The increase of nitrogen content in the composting process based on sludge is higher than that of pig manure,indicating that the transformation of nitrogen in the sludge compost is stronger than that of pig manure.In the pig manure compost and sludge compost,the more the biochar was added,the more obvious the decrease of C/N value was.（4）Adding biochar can reduce the content of Cu and Zn,increase the content of Pb,reduce the Cd content of pig manure heap,and have little difference between different biochar content,and the Cd content of the sludge pile body is 5%biochar treatment>10%biochar treatment.The content of Zn and Cd is caused by dilution and has a passivation effect on heavy metal Pb.In sludge composting,biochar can promote the passivation of Cu,Zn,Pb and Cd in the heap,and the more effective the biochar addition.（5）The seed germination rate,humification index,NO₄⁺-N/NO₃^--N value,C/N value,electrical conductivity,heavy metal and showed that biochar addition could help to improve the quality of the composting products.The degree of maturity and toxicity of the composting products with sludge were better than the pig manure.（6）After aerobic composting,a large number of fine particles have been blocked in the pores of biochar,and the longer the duration of the composting,the more particles in the pores,the more obvious the clogging;the pore wall of the biochar is thinner,and some of the pore structures are seriously destroyed and even collapsed,resulting in the disorder of the structure of biochar,which cannot be identified.Its original complete pore structure.Sludge treatment of biochar is more obvious in pore blocking and collapse,which indicates that the process of sludge composting has a greater impact on the structure characteristics of biochar.（7）After composting,the pH value of biochar decreased and EC increased.After composting,the content of C and H decreased,the content of N and O increased,the ratio of H/C decreased,and the ratio of O/C and（N+O）/C increased.The total acidic oxygen functional groups in the pig manure composts increased by 54.8%,64.5%,and CEC respectively by 35.2%and 34.7%,respectively,and the correlation between the total acid functional group content and CEC value was 0.922**.0.765*,the total acid oxygen functional groups in the sludge compost increased by 50%and 59.7%respectively,and the value of CEC increased by 36%and 34.7%respectively.The correlation between the total acidic functional group content and the CEC value was0.797*and 0.938**respectively.The infrared spectra showed that after the composting,the hydroxyl and carboxyl groups increased,the aromatic ring C-C decreased,the alkyl groups gradually disappeared,and the aromatic property was enhanced,and the biochar was oxidized,which may be affected by biological oxidation and abiotic oxidation.During the composting process,the chemical characteristics of biochar were similar in the composting process of different biochar,but on the whole,the chemical characteristics of the biochar with the more biochar added more deeply,and the composting process with pig manure as the raw material had more influence on the chemical characteristics of biochar than that of the sludge.