Greenhouse Gas Mitigation through Dairy Manure Acidification

Area of Science:

• Agricultural Science
• Environmental Science
• Chemical Engineering

Background:

• Liquid dairy manure storages release methane (CH), nitrous oxide (NO), and ammonia (NH).
• CH and NO are greenhouse gases (GHGs); NH indirectly contributes to NO emissions.
• Manure acidification reduces NH emissions in swine but is less studied for dairy manure's CH and NO reduction.

Purpose of the Study:

• To evaluate the effectiveness of dairy manure acidification in reducing CH, NO, and NH emissions.
• To compare emissions from control dairy manure with medium (pH 6.5) and low (pH 6) acidified manure treatments.

Main Methods:

• Utilized mesoscale manure tanks (6.6 m³) with controlled steady-state chambers.
• Continuously measured CH and NO emissions using tunable diode laser trace gas analyzers (June-December 2017).
• Measured NH emissions via acid traps three times weekly.

Main Results:

• Medium pH treatment reduced total GHG emissions by 85%; low pH treatment reduced them by 88% (CO equivalent basis).
• CH emissions decreased by 87% (medium pH) and 89% (low pH).
• NH emissions were reduced by 41% (medium pH) and 53% (low pH).

Conclusions:

• Dairy manure acidification is a promising strategy for significantly reducing GHG and NH emissions.
• Further research is needed to optimize acid dosage and understand manure buffering capacity for farm-scale application.
• Acidification offers a potential pathway for more sustainable dairy manure management.