Methane emissions reduced using gypsum in pilot-scale dairy manure tanks

Area of Science:

• Agricultural Science
• Environmental Science
• Climate Change Mitigation

Background:

• Animal manure storage facilities are significant sources of greenhouse gases (GHGs), primarily methane (CH4) and nitrous oxide (N2O).
• Reducing these emissions is crucial for Canada's climate change mitigation efforts.

Purpose of the Study:

• To evaluate the efficacy of adding gypsum powder to cow manure for reducing methane and nitrous oxide emissions.
• To determine optimal application rates for gypsum as a GHG mitigation strategy.

Main Methods:

• Pilot-scale study using duplicate tanks of dairy manure (∼10,000 L) with three gypsum rates: low (3.2 g L⁻¹), high (7.1 g L⁻¹), and control (0 g L⁻¹).
• Gas samples (CH4 and N2O) collected over 143 days from steady-state chambers using gas chromatography.
• Cumulative emissions calculated and compared across treatments.

Main Results:

• Both low and high rates of gypsum significantly reduced cumulative methane emissions compared to the control.
• Methane emission reductions were substantial: 87% for the low rate and 92% for the high rate.
• While nitrous oxide emissions showed a reduction trend with gypsum, it was not statistically significant due to minor emission levels.

Conclusions:

• Gypsum additive is a safe and effective strategy for mitigating greenhouse gas emissions from animal manure slurry in storage.
• Further research is needed to establish on-farm application rates and assess economic feasibility.