Greenhouse Gas Emissions during Windrow Composting and Open-Air Dumping of Pig Manure with Added Wood Shavings

Aims: To evaluate GHG emissions from two common manure management practices in Cameroon; windrow composting and Open-air dumping with and without the addition of wood shavings.

Study design: The research employed a controlled experimental design with a comparative approach.

Place and Duration of Study: Waste-to-resource project site and project laboratory of the Department of Environmental Science of the University of Buea, Cameroon between February and March 2023.

Methodology: Fresh pig manure was treated in four configurations: 100% manure subjected to windrow composting, 100% manure subjected to open-air dumping, 90:10% manure: wood shavings subjected to windrow composting, and 90: 10% manure: wood shavings subjected to open-air dumping. Gas samples were collected every next morning at 10:00 AM over a period of 40 days using the static flux chamber method, and analyzed for CH₄, N₂O, and CO₂ emissions using gas chromatography.

Results: Results showed that adding wood shavings significantly reduced CH₄ and N₂O emissions across both composting and open-air dumping systems. CH₄ emissions were highest in stockpiled 100% manure (2.152 ± 1.741 mg CH₄ m² min⁻¹) and lowest in composted manure with wood shavings (0.085 ± 0.179 mg CH₄ m² min⁻¹). N₂O emissions followed a similar trend, with the highest emissions (131.3 ± 90.4 mg N₂O m² min⁻¹) recorded in stockpiled 100% manure, compared to the lowest (35.25 ± 43.50 mg N₂O m² min⁻¹) in stockpiled manure with wood shavings. CO₂ emissions were higher in treatments with wood shavings, particularly in composting (159.2 ± 70.8 mg CO₂ m² min⁻¹). Further statistical analyses confirmed significant differences in GHG emissions among the different treatments, with windrow composting consistently outperforming Open-air dumping in reducing CH₄ and N₂O emissions.

Conclusion: The study concluded that wood shavings addition and windrow composting practices significantly reduced GHG emissions from pig manure management in tropical settings.