Field-Scale Pilot Observation of Continuous Cattle Slurry Acidification on Methane and Ammonia Emission Mitigation (Published)

Livestock activities are a major source of anthropogenic greenhouse gas emissions, particularly in tropical regions where high ambient temperatures accelerate manure degradation. This study evaluated the efficacy of field-scale continuous cattle slurry acidification using concentrated sulfuric acid (H2SO4) to mitigate methane (CH4) and ammonia (NH3) emissions under Malaysian conditions. Pilot observations in 600-liter high-density polyethylene tanks demonstrated that maintaining a slurry pH of 5.0 through periodic re-acidification reduced cumulative CH4 emissions by 62.3% and total NH3 volatilization by 35.3% over a 120-day storage period. A parallel field pond trial confirmed a 90% immediate reduction in CH4 flux following acidification to pH 5.0, though emissions gradually rebounded as the slurry’s natural buffering capacity returned the pH toward neutral. Economic analysis indicated the technology is viable with a Benefit-Cost Ratio (BCR) of 1.30, primarily driven by carbon (C) credit potential from CH4 mitigation, which accounted for over 80% of total benefits. However, the relatively modest net benefit indicates that the economic performance of the system remains sensitive to fluctuations in key market parameters, particularly carbon pricing and chemical input costs. These findings suggest that decentralized acidification is a practical tool for SME farmers to align with Net Zero 2050 targets, provided that policy interventions stabilize the economic returns against market volatility.

Keywords: Ammonia, cattle slurry, continuous acidification, greenhouse gas, methane

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

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.

 

 

 

 

 

 

 

 

Keywords: Ammonia, continuous acidification, greenhouse gas, methane, slurry

Controlling Poultry House Ammonia Emmissions Using Gas Permeable Membrane Systems (Published)

An experiment was conducted to investigate the use of gas-permeable membrane systems to capture and recover ammonia from poultry houses. The objectives of the experiment were: 1) to evaluate the performance of two gas-permeable membrane ammonia-capturing system models and 2) to assess ammonia emission impact on birds’ mortality, and to investigate the relationship between birds age and ammonia emission in rooms equipped with and without these systems. The systems were developed and placed inside a 6.0 m X 6.0 m room in a research poultry house.  The systems were started by preparing 5N sulfuric acid in an acid tank and a pH 1 solution in a concentration tank. Acids were added to the concentration tank manually to achieve a pH of 2.0, and then the pH pump controller and the membrane circulation modules were used to bring the pH back to 1. After NH₃ gas passed through the membrane and was in contact with the acidic solution, ammonium (NH₄⁺) salt was formed, which was retained and concentrated in the acidic solution. The experiment consisted of two treatments namely: 1) Control (room without membrane systems (RWOMS), and 2) treatment (room with both membrane systems (RWMS). Each room contained 400 birds. The results demonstrated a significant (p<0.05) difference of air ammonia concentration between rooms and from poultry litter. Among the membrane systems, tubular membrane system had the greatest mean NH₄⁺ recovery compared to the flat membrane system. The difference was highly significant (p<0.01). Birds’ mortality rate was decreased by ~46.6% in room with the installed systems indicating that reduced ammonia resulted in improved bird survival. The findings of this study indicate that the membrane systems can be an effect method of reducing ammonia concentration in poultry houses with an added advantage of retaining ammonium salt has plant food. 

Keywords: Ammonia, Ammonium, Gas‐Permeable Membrane, Poultry manure, Sulfuric Acid