Greenhouse Gas Emissions during Windrow Composting and Open-Air Dumping of Pig Manure with Added Wood Shavings
David T. Tiku *
Department of Environmental Science, Faculty of Science, University of Buea, Cameroon.
Fabrice L. Yengong
Department of Environmental Science, Faculty of Science, University of Buea, Cameroon.
Ngwa M. Ngwabie
Department of Agricultural and Environmental Engineering, College of Technology, The University of Bamenda, Bambili, Cameroon.
Veronica E. Manga
Department of Environmental Science, Faculty of Science, University of Buea, Cameroon.
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Greenhouse gas emissions, pig manure management, windrow composting, open air dumping, wood shavings amendment, aeration