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| Effects of inoculation ratios on the biochemical methane potential of pig manure under mesophilic conditions |
| Received:October 12, 2022 Revised:April 25, 2023 |
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| KeyWord:anaerobic digestion;pig manure;inoculation ratio;biochemical methane potential;mesophilic condition |
| Author Name | Affiliation | | MA Wenlin | Beijing Climate Change Response Research and Education Center, Beijing University of Civil Engineering and Architecture, Beijing 102616, China
School of Environment and Energy Engineering, Beijing University of Civil Engineering and Architecture, Beijing 102616, China | | WANG Anji | School of Environment and Energy Engineering, Beijing University of Civil Engineering and Architecture, Beijing 102616, China |
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| Abstract: |
| This study aimed to explore the effects of different inoculation ratios on the biochemical methane potential(BMP)of pig manure under mesophilic conditions. BMP experiments were conducted at(35.0±0.5)℃ and 3% of the initial volatile solids(VS)concentration at the ratios of pig manure to inoculum solution of 1:2, 1:1 and 2:1, respectively. During the experiment, the methane productions of each test were monitored daily, and the physical and chemical indices of the supernatant of fermentation liquid, such as pH, ammonia nitrogen, total nitrogen, and glucose, were measured once every two to three days. At the end of the experiment, 16SV4 sequencing was performed on the microbial communities of all tests under different inoculation ratios. Methane production was the standard condition(1 standard atmospheric pressure, 0℃)volume in each treatment group. The results showed that the cumulative methane production and maximum daily methane production were positively correlated with the pig manure inoculation ratio(P＜0.05); however, there was no significant difference in the BMP(calculated by VS)of pig manure under different inoculation ratios(P＞0.05). The BMPs of pig manure were(252.05± 5.12),(250.07±16.57)mL·g-1, and(249.65±13.69)mL·g-1 at inoculation ratios of 1:2, 1:1, and 2:1, respectively. The mean BMP was calculated as(250.59±1.28)mL·g-1. Firmicutes, Bacteroides, and Cloacimonadota were the three types of bacteria with the highest relative abundance in the anaerobic digestion system of pig manure. Halobacterota dominated the methanogenic archaea. The decreasing relative abundance levels of Proteobacteria and Methanobacterium were negatively correlated with the inoculation ratio. The modified Gompertz model was more suitable than the Logistic model for anaerobic digestion kinetics analysis of pig manure under mesophilic conditions. In conclusion, there was no significant difference in BMP values of pig manure with different inoculation ratios under mesophilic conditions ([35.0±0.5)℃] and initial VS level(3%). Selecting the inoculation ratio of 1:2 for the BMP test of pig manure is recommended to shorten its measurement time and improve its working efficiency. |
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