Abstract
Liquid dairy manure treated with sulfuric acid was stored in duplicate pilot-scale storage tanks for 120 days with continuous monitoring of CH4 emissions and concurrent examination of changes in the structure of bacterial and methanogenic communities. Methane emissions were monitored at the site using laser-based Trace Gas Analyzer whereas quantitative real-time polymerase chain reaction and massively parallel sequencing were employed to study bacterial and methanogenic communities using 16S rRNA and methyl-coenzyme M Reductase A (mcrA) genes/transcripts, respectively. When compared with untreated slurries, acidification resulted in 69–84% reductions of cumulative CH4 emissions. The abundance, activity, and proportion of bacterial communities did not vary with manure acidification. However, the abundance and activity of methanogens (as estimated from mcrA gene and transcript copies, respectively) in acidified slurries were reduced by 6 and 20%, respectively. Up to 21% reduction in mcrA transcript/gene ratios were also detected in acidified slurries. Regardless of treatment, Methanocorpusculum predominated archaeal 16S rRNA and mcrA gene and transcript libraries. The proportion of Methanosarcina, which is the most metabolically-diverse methanogen, was the significant discriminant feature between acidified and untreated slurries. In acidified slurries, the relative proportions of Methanosarcina were ≤ 10%, whereas in untreated slurries, it represented up to 24 and 53% of the mcrA gene and transcript libraries, respectively. The low proportions of Methanosarcina in acidified slurries coincided with the reductions in CH4 emissions. The results suggest that reduction of CH4 missions achieved by acidification was due to an inhibition of the growth and activity of Methanosarcina species.
Highlights
Livestock production is a significant source of methane (CH4) emissions (e.g., 119.1 ± 18.2 Tg in 2011) (Wolf et al, 2017), mainly from enteric fermentation and manure management of dairy farming operations (Laubach et al, 2015; Jayasundara et al, 2016; Wolf et al, 2017)
In this study we investigated structure and activity responses of bacterial and methanogenic communities to the addition of H2SO4 to stored liquid dairy manure
Addition of 1.4 L and 2.4 L 70% H2SO4 m−3 slurry resulted in 69–84% reduction of cumulative CH4 emissions when compared with untreated slurries (Figure 1D)
Summary
Livestock production is a significant source of methane (CH4) emissions (e.g., 119.1 ± 18.2 Tg in 2011) (Wolf et al, 2017), mainly from enteric fermentation and manure management of dairy farming operations (Laubach et al, 2015; Jayasundara et al, 2016; Wolf et al, 2017). The large volumes of manure produced annually from intensive dairy farming operations are Greenhouse Gas Emissions From Manure usually stored in slurry form (VanderZaag et al, 2013), which create environments conducive to CH4 production (Grant et al, 2015; Petersen, 2018). To reduce CH4 emissions from such storage systems, strategies such as reduction of aged manure (inoculants), crust development for potential aerobic CH4 oxidation, and manure acidification using sulfuric acid (H2O4) have been reported (Petersen et al, 2012; Sommer et al, 2017; Habtewold et al, 2018). Sulfuric acid-based acidification of liquid dairy manure has primarily been used to abate ammonia (NH3) emissions, but can reduce CH4 emissions (Ottosen et al, 2009; Petersen et al, 2012; Fangueiro et al, 2015; Sommer et al, 2017). There are no data available about the effects of manure acidification on the activities of microbial communities in stored liquid dairy manure
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