Study And Estimation On The Biochemical Methane Potential Of Livestock Manure In Anaerobic Digestion

Livestock manure management process is one of the important sources of agricultural greenhouse gas?GHGs?emissions,and the proportion of anaerobic degradation of livestock manure is also a key factor affecting the methane emission during the production and management of livestock manure.The study found that anaerobic digestion?AD?not only can significantly reduce CH₄ emissions,but also could provide clean energy as alternative fossil fuels.Hence,conversing livestock manure to the useful resources is undoubtedly a good way to reduce emissions of CH₄.Simultaneously,taking into account the expansion of the scale of livestock in China and the production mode changes in the preparation of greenhouse gas inventory when t the default value of B₀ given by IPCC is no longer in line with the actual production of animal husbandry in China.In this paper,on the basis of the literature of domestic and foreign,three typical waste of livestock and poultry,that is,chicken manure?CM?,dairy manure?DM?and swine manure?SM?were selected as the substrate,and a series of batch AD tests were carried out under the condition of 37±0.5?.Firstly,the effects of total solids?TS?content and inoculation ratios on the gas production characteristics of swine manure were investigated.Cumulative biogas production,cumulative methane production,methane accumulated methane yield,TS and volatile solids?VS?removal rate,fermentation broth characteristics were measured and analyzed,and the proper TS content and inoculation ratio parameters were obtained by anaerobic fermentation.AD process of CM,DM and SM was quantified and fitted to the first-order kinetic model and modified Gompertz model.The results obtained in this test was in line with China's current production of the actual B₀ value.Finally,according to the B₀ obtained from the BMP test,the biochemical methane potential of CM,DM and SM was calculated to provide the reference for parameter selection,greenhouse gas emissions and making the relevant policy in China.The main conclusions are as follows:The results showed that in the AD process of SM,the biogas production in different treatments was similar to that under different TS content and inoculation ratio.The maximum biogas yield was 469.1mL·g^-1 VS at TS=6%,r_I/S=3.0,and which significantly higher than that of the other treatments?P<0.05?.The highest methane yield(333.2 mL·g^-1VS)was achieved at TS=6%and r_I/S=3.0,which was significantly higher than that of other treatments?P<0.05?.The rate of TS content and inoculation had a significant effect on the gas production rate and cumulative methane production,and the TS content played a much more role in the biogas production than theinoculation ratio.The kinetic model parameters show that the first-order kinetic model was better that the modified Gompertz model to fit the AD process of SM,and to a certain extent,a higher accuracy was found with the higher inoculation ratio and TS content.The results showed that the peak of biogas production rate for CM,DM,and SM was 87.86,60.53and 102.51 mL·g^-1VS·d^-1,respectively.The cumulative methane production of CM,DM and SM was326.01,172.28,375.29 mL·g^-1VS_added.The BMP_1%of CM,DM and SM were 316.85,162.11 and351.63 mL·g^-1,respectively,which accounted for over 90%of the measured BMP value at the end of the experiment.This suggested that BMP_1%could be used to reflect the biomethane potential of organic matters in AD process.Compared to the time taken for the BMP,the time for achieveing BMP_1%was shortened by 45.3⁷6.6%.The time taken for BMP_1%as the end of the test time ont only reduced the test time,but also gave a quantitative standard for the BMP test.The cumulative methane yield of CM,DM and SM measured by BMP test was 0.33,0.17 and 0.38 m³·kg^-1VS_added,respectively,and the corresponding value given by IPCC was 0.24,0.13 and 0.29 m³·kg^-1VS_added were remarkably different.The first-order model and the modified Gompertz model were used to fit the methane curves of the three substrates.The parameters of the first-order model and the modified Gompertz model were compared.The first-order model was fitted with the accuracy.But the coefficient?R²?of both first-order model and the modified Gompertz model were all greater than 0.9,and BMP_?also reached 90%of cumulative methane yield obtained in the test.In a word,the kinetic parameters indicated that these two models can be used to fit the AD process of these three typical livestock manure.