Effects of storage temperature on CH4 emissions from cattle manure and subsequent biogas production potential

초록

CH4 is one of the main greenhouse gases (GHGs) generated from agricultural sector, and a significant amount of it is emitted during the storage of livestock manure. To mitigate the CH4 emissions, strong acid addition to the manure was attempted, which is only applicable to slurry-type manure. On the other hand, lowering the storage temperature could be an effective method to reduce the CH4 emissions, particularly applicable to solid-type manure. In this study, cattle manure (CM) with a high-solid content (TS > 30%) was stored at different temperatures (15-35 degrees C) for 80 d. The highest CH4 emissions of 375.1 kg CO2 eq./ton VS was observed at 35 degrees C, and this was reduced to less than half at <= 20 degrees C. Like the difference in CH4 emissions, the degradation of organic matter showed a similar trend. The maximum VS reduction of 29% was observed at 35 degrees C, while only 8% reduction was observed at 15 degrees C. Results from microbial community analyses and specific methanogenic activity tests indicated that hydrogenotrophic methanogens were the dominant indigenous CH4-producers, and the abundance of psychrophilic methanogens increased with decreasing temperature. The conservation of organic matter at low temperature led to an increase in biogas production potential from 25 to 43 L CH4/kg CM. It was calculated that the GHGs emissions from electricity consumption for cooling CM below 25 degrees C can be offset by mitigating CH4 emissions during storage but increasing in subsequent biogas production potential of CM. Compared at 35 degrees C, 91.6 kg CO2 eq./ton CM of GHGs reduction can be attained at 15 degrees C. (C) 2019 Elsevier Ltd. All rights reserved.

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