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Dairy Manure Total Solid Levels Impact CH 4 Flux and Abundance of Methanogenic Archaeal Communities
Author(s) -
Habtewold J.,
Gordon R. J.,
Wood J. D.,
WagnerRiddle C.,
VanderZaag A. C.,
Dunfield K. E.
Publication year - 2017
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2016.11.0451
Subject(s) - methanogen , slurry , methanogenesis , manure , archaea , methane , chemistry , anaerobic digestion , biogas , environmental chemistry , abundance (ecology) , food science , biology , environmental science , environmental engineering , ecology , biochemistry , gene , organic chemistry
Stored liquid dairy manures are methane (CH 4 ) emission hotspots because of the large amount of slurry volatile solids (VS) converted into CH 4 by methanogens under anaerobic conditions. Our research has indicated that a reduction of total solids (TS) of slurries before storage can reduce CH 4 emissions. In the current study, methanogen abundance was characterized in tanks with different CH 4 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 α subunit methyl‐coenzyme M reductase ( mcrA ), which catalyzes the final step of methanogenesis. Interestingly, mean abundances of methanogens increased by ∼8 and 23% at the top and bottom sections, respectively, as slurry TS decreased from 9.5 to 0.3%. Cumulative CH 4 emissions, however, decreased by ∼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 CH 4 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 CH 4 emissions at reduced TS levels of dairy slurries. Core Ideas Reduction of total solids levels of stored dairy slurry can reduce cumulative CH 4 flux. Abundance and activity of methanogens increase as dairy slurry total solids decrease. Volatile solids‐to‐CH 4 conversion rates appear to be higher as dairy slurry total solids decrease. Substrate availability, not methanogen population, limits cumulative CH 4 flux.