Methane emission reduction by adding sulfate to liquid dairy manure

Area of Science:

• Agricultural Science
• Environmental Science
• Animal Science

Background:

• Dairy farming aims to reduce its carbon footprint, with methane (CH4) from manure being a significant source.
• Current methane reduction technologies like anaerobic digesters face adoption barriers due to cost and infrastructure.
• Low-cost, easily adoptable alternatives are needed for near-term methane emission reductions.

Purpose of the Study:

• To evaluate the efficacy of different sulfate-based additives and acidification strategies for suppressing methane emissions from dairy manure.
• To compare the effectiveness of sulfuric acid (H2SO4), phosphoric acid (H3PO4), and calcium sulfate (CaSO4) in reducing manure methane.

Main Methods:

• A 157-day laboratory study at 24°C compared the effects of CaSO4, H2SO4, and H3PO4 on manure methane emissions.
• Tested varying rates of CaSO4 and two acidification levels (pH > 7 and pH < 7) for H2SO4 and H3PO4.
• Monitored cumulative methane (CH4) emissions over time to assess suppression efficacy.

Main Results:

• Acidification with H2SO4 and H3PO4 showed early methane suppression (up to 65% and 54% within 40 days, respectively).
• Sulfate compounds demonstrated increasing suppression after 50 days, with final cumulative suppression up to 63% for CaSO4 and 91% for H2SO4.
• H2SO4 was most effective, likely due to combined acidity and sulfate content; CaSO4 was more effective than H3PO4.

Conclusions:

• Sulfate-based additives, particularly gypsum (CaSO4), show significant potential for reducing dairy manure methane emissions.
• These additives offer a promising, low-cost, and readily adoptable alternative to anaerobic digesters for near-term methane reduction.
• Further research into sulfate-based additives could provide scalable solutions for dairy farms to mitigate greenhouse gas emissions.