Methane Producing Characteristics Of Three Kinds Of Livestock And Poultry Manure Mixed With Corn Straw And The Effects Of Cu And Zn Contents

In order to understand the relationship between the characteristics of raw materials and the cumulative production quanatity of methane during the anaerobic fermentation and to improve the efficient utilization of livestock and poultry manures and corn straw, the methane production characteristics of chicken manure, swine manure, cow manure, corn straw, and their mixture material were studied under thermophilic anaerobic digestion （55℃） in a laboratory batch incubation system. And then the effects of Cu and Zn contents on the methane generation characteristics of three kinds of livestock and poultry manure （chicken manure, swine manure, and cow manure） mixed with corn straw were studied. The main conclusions are as follows:（1） The contents of heavy metals Cu, Zn, Pb, Cr, Cd, and Ni in chicken manure, swine manure, and cow manure sampled from different places were tested. The results showed that the contents of Cu and Zn were the highest in the chicken manure, swine manure, and cow manure.The Cu content was 48～146 mg·kg^-1 and Zn content was 253～600 mg·kg^-1 in chicken manure, the Cu content was 401～1158 mg·kg^-1 and Zn content was 587～1249 mg·kg^-1 in pig manure, and the Cu content was 7～81 mg·kg^-1 and Zn content was 19～327mg·kg^-1 in cow dung.（2） Three chicken manures, three swine manures, and three cow manures were screened out from the livestock and poultry manure sampled from different places based on their volatile solid （VS） contents in preliminary screening process. The VS contents of the three chicken manures were 51.3%,85.5%, and 64.4% respectively, the VS contents of the three swine manures were 60.5%,51.3%, and 73.0% respectively, and the VS contents of the three cow manures were 86.8%,38.8%, and 74.8% respectively. The methane production capacity of the three chicken manures, three swine manures, and three cattle manures were studied under thermophilic anaerobic digestion （55℃） condition. The results showed that the cumulative methane production quantities of chicken manure No.5, swine manure No.7, and cow manure No.17 were the highest and their cumulative methane production quantities were 3896,4986, and 5597 mL respectively. At the same time, the results of correlation analysis showed that the NH4+-N content in the fermentation liquid was the main factor which led to the difference of the three chicken manures in cumulative methane production quantity and the C/N value of fermentation material was the main factor which made the difference of the three cow manures in cumulative methane production quantity.（3） The methane production capacity of chicken manure No.5, swine manure No.7, and cow manure No.17 was analyzed and compared. The results showed that the cumulative methane production quantity of the cattle manure No.17 was the highest （5597 mL）, followed by the swine manure No.7 （4986 mL）, and the chicken manure No.5 was lowest （3896 mL）. The cumulative methane production quantity was negatively related to VS degradation rate and the contents of crude protein and crude fat of the fermentation materials, while it was positively related to C/N decline rate and the contents of carbohydrates and crude fiber of the fermentation materials. The content of NH4+-N in the fermentation liquid of chicken manure was significantly higher than that of swine and cattle manures during incubation period and reached as high as 2348.33 mg·L1 at the end. The time of methane production was shorter and cumulative methane production quantity was lower of chicken manure than that of swine and cattle manures. The organic material composition of the three livestock and poultry manures was the important factor controlling the cumulative methane production quantity under thermalphilic digestion condition.（4） The methane productions capacity of the three kinds of livestock and poultry manures mixed with corn straw were analyzed and compared. The results showed that the change trends of daily methane production quantities of the three kinds of livestock and poultry manures （chicken manure, swine manure, and cow manure） mixed with corn straw were nearly the same. The cumulative methane production quantities of chicken manure and corn straw mixed by the ratio of 3:1, swine manure and corn straw mixed by the ratio of 2:1, and cow manure and corn straw mixed by the ratio of 1:1 were all the highest, and their cumulative methane production quantities were 8504,6051, and 6072 mL respectively. The cumulative methane production quantity was positively related to TS degradation rate, VS degradation rate, VFA degradation rate, and C/N decline rate at the end of anaerobic fermentation, therefore their changes can reflect the cumulative methane production quantity of the three kinds of livestock and poultry manures mixed with corn straw. At the same time, the contents of NH4+-N in the fermentation liquid of the three kinds of livestock and poultry manures mixed with corn straw increased in varying degrees at the end of fermentation. The content of NH4+-N in the fermentation liquid of chicken manure mixed with corn straw was the highest and was 1382.4～1863.4 mg/L. The results showed that the NH4+-N content in the fermentation liquid was the main factor which affected the cumulative methane production quantity of chicken manure mixed with corn straw.（5） Effects of Cu content on the methane productions capacity of the three kinds of livestock and poultry manures mixed with corn straw were studied. The results showed that the change trends of daily methane production quantities of the three kinds of livestock and poultry manures （chicken manure, swine manure, and cow manure） mixed with corn straw treated by different contents of Cu were nearly the same during the anaerobic fermentation. The cumulative methane production quantity was negatively related to the content of Cu. The cumulative methane production quantity of CK was higher than that of other treatments added with Cu. The cumulative methane production quantity of chicken manure and corn straw CK (the content of Cu is 169.14 mg·kg^-1) was 7970 mL, the cumulative methane production quantity of swine manure and corn straw CK (the content of Cu is 481.42 mg·kg^-1) was 7444 mL, and the cumulative methane production quantity of cow manure and corn straw CK (the content of Cu is 481.42 mg·kg^-1) was 8248 mL.（6）Cu inhibited the activities of the hydrolytic eneymes in the fermentation system. The results showed that the cellulase activities, sucrase activities, and urease activities of chicken manure mixed with corn straw and swine manure mixed with corn straw treated with Cu were significantly positively related to their accumulative methane production quantities. The cellulase activities and sucrase activities of cow manure mixed with corn straw treated with Cu were significantly positively related to its accumulative methane production quantity, but the urease activities was not significantly correlated with the accumulative methane production quantity.（7） The optimal regression equations of the Cu contents in the three kinds of livestock and poultry manures mixed with coen straw and the accumulative methane generation quantities were established by SPASS software. It showed that the anaerobic fermentation process was inhibited when the content of Cu was more than 623.8 mg·kg^-1 in chicken manure mixed with corn straw at the ratio of 3:1, and its cumulative methane production quantity was 5523.9 mL and was 30.7% lower than CK. The anaerobic fermentation process was inhibited when the content of Cu was more than 509.8 mg·kg^-1 in chicken manure mixed with corn straw at the ratio of 1:1, and its cumulative methane production quantity was 7089.5 mL and was 14.1% lower than CK.（8） Effects of different Zn contents on the methane production capacities of the three kinds of livestock and poultry manures mixed with corn straw were studied. The results showed that the change trends of daily methane production quantities of the three kinds of livestock and poultry manure mixed with corn straw treated by different contents of Zn were nearly the same during the anaerobic fermentation. The cumulative methane production quantities were negatively related to the contents of Cu in chicken manure mixed mixed with corn straw, the cumulative methane production quantities were significantly negatively related to the contents of Cu in swine manure mixed with corn straw, and the cumulative methane production quantities were positively related to the contents of Cu in cow manure mixed with corn straw. The cumulative methane production quantity of chicken manure mixed with corn straw was the highest in Zn100 treatment (the content of Zn is 502.26 mg·kg^-1) and it was 7499 mL. The cumulative methane production quantity of swine manure mixed with corn straw was the highest in the treatment CK (the content of Zn is 666.22 mg·kg^-1) and it was 7666 mL. The cumulative methane production quantity of cow manure mixed with corn straw was the highest in the Zn200 treatment (the content of Zn is 345.6 mg·kg^-1) and it was 8260 mL. The results showed that adding appropriate Zn can promote the cumulative methane production quantity in the anaerobic fermentation system.（9） Zn inhibited the hydrolase activity in chicken manure mixed corn straw and swine manure mixed corn straw, but promoted the hydrolase activity in cow manure mixed with corn straw. The cellulase activities and sucrase activities of the three kinds of livestock and poultry manures mixed with corn straw were significantly positively related to their accumulative methane production quantities, but the urease activities were not significantly related to their accumulative methane production quantities.（10） The optimal regression equations between the Zn contents in the three kinds of livestock and poultry manures mixed with corn straw and the accumulative methane generation quangtities were set up by SPASS software. It showed that the optimal Zn content was 522.1 mg·kg^-1 in chicken manure mixed with corn straw at the ratio of 3:1 and its cumulative methane production quantity was the highest （655.8 mL）. The optimal Zn content was 720.9 mg·kg^-1 in swine manure mixed with corn straw at the ratio of 2:1 and its cumulative methane production quantity was the highest （7587.3 mL）. The optimal Zn content was 414.5 mg·kg^-1 in cow manure mixed with corn straw at the ratio of 1:1 and its cumulative methane production quantity was the highest （7924.7 mL）.