Exploring Continuous Cattle Slurry Acidification as a Strategy for Reducing Greenhouse Gas Emissions

Cattle feedlot farming typically relies on multiple lagoons for slurry storage, which significantly contributes to greenhouse gas emissions. Slurry acidification is a promising approach for reducing greenhouse gas (GHG) and ammonia (NH₃) emissions from livestock manure management. A study was conducted to evaluate an alternative method of reducing NH₃ and CH₄ emissions during slurry storage by maintaining a lower pH through continuous acidification with concentrated hydrochloric acid (HCl), concentrated sulfuric acid (H₂SO₄), lactic acid (C₃H₆O₃), and nitric acid (HNO₃). Cattle slurry was collected from commercial farms, stored with different acids to maintain a pH of 5.0, and re-acidified every three weeks. The results showed that reducing slurry pH with HCl and H₂SO₄ significantly decreased NH₃ volatilization by 86.8% and 82.9%, respectively. Both HNO₃ and C₃H₆O₃ reduced NH₃ emissions by 63%. In terms of CH₄ emissions, HCl and H₂SO₄ inhibited emissions by 17.7% and 19.3%, respectively, while HNO₃ was more effective, reducing CH₄ by 57%. Interestingly, the use of C₃H₆O₃ did not reduce CH₄ emissions but instead led to a 151% increase in CH₄ release into the atmosphere. These findings emphasize the potential of acidification for mitigating emissions while highlighting the need to optimize acid selection and dosage to balance environmental and economic considerations. Further research should assess its long-term impacts, microbial interactions, and feasibility on-farm implementation.