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Acidification with inorganic and organic acids to reduce greenhouse gas emission from pig slurry: Acidification with inorganic and organic acids to reduce greenhouse gas emission from pig slurry

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Methane emission from livestock manure contribute significantly to the total climate footprint of agriculture. Acidification of manure is known to reduce methane emission. However, the mode of inhibition by acidification is not completely understood and may depend on the acid or acids used.
In this work, we examined the effect of organic, inorganic, and mixed acids on greenhouse gas emission from pig slurry. Initially, pig slurry was incubated in glass vials and acidified to pH 5.5. Methane production was measured with a GC-TCD. After initial screening, a continuous gas monitoring setup was used to simulate conditions occurring in a pig house. Greenhouse gas emission, was continuously measured with a cavity-ring-down spectrometer, while different acid combinations were used to treat the pig slurry to pH 5.5 - 6.25. The effect of daily-added pig slurry, as well as weekly slurry removal, and acidification of the residual slurry was examined using this laboratory setup as well.
In the initial screening, nitric acid reduced methane with > 99% (p = 2.0E-10) when acidified to pH 5.5. Combinations of acetic acid with sulfuric acid or nitric acid showed no further inhibition of methane production compared to nitric or sulfuric acid alone. In the continuous gas monitoring setup nitric acid reduced methane emission, but increased nitrous oxide emission, reducing the treatment effect on total CO2-e considerably. Treatment with HNO3 to pH 6.25 increased nitrous oxide emission by > 800% (p = 0.042). Treatment with different ratios of nitric acid and sulfuric acid to pH 5.5, was not better than pure sulfuric acid treatment, which resulted in 92% CO2-e reduction (p = 0.002). When daily addition of slurry was applied, the efficiency of acidification decreased significantly after one week, and CO2-e was not significantly different from the control (p = 0.085 for H2SO4 treatment).
Udgivelsesårjun. 2022
StatusUdgivet - jun. 2022
Begivenhed8th International Greenhouse Gas & Animal Agriculture Conference - Orlando, USA
Varighed: 5 jun. 20229 jun. 2022


Konference8th International Greenhouse Gas & Animal Agriculture Conference

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