Effects of polyphenol-rich extracts and compounds on methane and ammonia emissions from pig slurry during 28-day incubation

Animal manure in livestock production facilities is a major source of methane (CH₄) and ammonia (NH₃) emissions from agriculture. In this study, we investigated different polyphenol-rich extracts and chemicals including commercial chestnut tannin (CT), shea meal extract (SME) and lignosulfonic acid (LSA) in combination with 1 mM of urease inhibitors acetohydroxamic acid (AHA) and/or sodium fluoride (NaF) to mitigate CH₄ and NH₃ in an in-vitro setup with 0.5 L slurry reactors mimicking slurry pits in livestock facilities. Daily addition of pig feces and urine along with additives were conducted for 28 days at room temperature, while CH₄ and NH₃ emissions were monitored by cavity ring-down spectroscopy (CRDS) continuously. SME and SME + NaF added to slurry reduced CH₄ emission by 72% and 88%, and NH₃ emission by 45% and 52%, respectively. CT + NaF at the CT concentration of 2.6, 4.25 and 8.5 mg mL⁻¹, resulted in 48–55%, 70–72% and 81% reduction in CH₄ emission, and 17–29%, 40–49% and 49% reduction in NH₃ emission, respectively. Emission reduction based on the dosage of CT revealed that the relationship between dosage and emission reduction is not linear, therefore the reduction efficiency was calculated by emission reduction divided by concentration. CH₄ reduction efficiency at the CT concentration of 2.6, 4.25 and 8.5 mg mL⁻¹ were 18–21, 16–17 and 10 % (mg mL⁻¹)⁻¹. Therefore, the optimum dosage of CT was 4.25 mg mL⁻¹. In conclusion, addition of CT and SME along with NaF resulted in significant reductions of both CH₄ and NH₃ emissions, while supplementation of LSA and AHA to CT + NaF did not enhance the mitigation effect.