科研之友
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摘要
Stored liquid dairy manures are methane (CH4) emission hotspots because of the large amount of slurry volatile solids (VS) converted into CH4 by methanogens under anaerobic conditions. Our research has indicated that a reduction of total solids (TS) of slurries before storage can reduce CH4 emissions. In the current study, methanogen abundance was characterized in tanks with different CH4 emissions. Using mesoscale slurry storage facilities equipped for continuous gaseous emission monitoring, we stored dairy slurries having TS from 9.5 to 0.3% for up to 6 mo. Samples were taken after Day 30 and Day 120 of the storage (20 May-16 Nov. 2010) from the upper and bottom layers of the slurries. Methanogenic communities were studied by targeting the gene encoding the a subunit methyl-coenzyme M reductase (mcrA), which catalyzes the final step of methanogenesis. Interestingly, mean abundances of methanogens increased by similar to 8 and 23% at the top and bottom sections, respectively, as slurry TS decreased from 9.5 to 0.3%. Cumulative CH4 emissions, however, decreased by similar to 70% as slurry TS decreased from 9.5 to 0.3%. Nevertheless, compared with Day 30 of storage, mean abundances of methanogens were relatively higher at Day 120 (up to 19%), consistent with an increase in the cumulative CH4 emissions. Polymerase chain reaction denaturing gel electrophoresis analysis indicated a low methanogen diversity, with most bands sequenced closely related to the genus Methanocorpusculum (>95% amino acid sequence similarity), the hydrogenotrophic methanogens. Results suggest that available carbon substrate and not methanogen abundance may be limiting cumulative CH4 emissions at reduced TS levels of dairy slurries.
- 出版日期2017-2
