Tropentag, September 11 - 13, 2024, Vienna "Explore opportunities... for managing natural resources and a better life for all"

Greenhouse gas emissions from traditional livestock enclosures in Kenya and options for mitigation

¹International Livestock Research Institute (ILRI), Mazingira Centre, Kenya
²Chinese Academy of Sciences, Inst. of Mountain Hazards and Environment, China
³Midlands State University, Dept. for Land and Water Resources Manag., Zimbabwe
⁴Karlsruhe Institute of Technology (KIT), Inst. of Meteorology and Climate Research, Atmospheric Environmental Research, Germany
⁵Agroscope, Research Division Agroecology and Environment, Switzerland

Abstract

Livestock in semi-arid pastoral rangelands is often corralled overnight in traditional enclosures (“bomas” or “kraals”) to protect them from theft and predators. Manure is usually not removed from bomas but is left to accumulate, building thick manure layers that are hotspots for greenhouse gas (GHG) emissions in the landscape. Here, we present a full year of measurements of manure CH₄ and N₂O emissions from cattle bomas in Kenya. We found that GHG flux rates from bomas were elevated by several orders of magnitude compared to background savannah fluxes, with mean fluxes of 325 ± 11 µg N₂O-N m^-2 h^-1 and 3245 ± 234 µg CH₄-C m^-2 h^-1 for active bomas, and 610 ± 186 µg N₂O-N m^-2 h^-1 and 3127 ± 1262 µg CH₄-C m^-2 h^-1 for abandoned bomas, while surrounding savannah soils only emitted 2.5 ± 2.2 µg N₂O-N m^-2 h^-1 and 0.1 ± 0.7 µg CH₄-C m^-2 h^-1. At the farm scale, boma manure contributed little (2.2%) to total CH₄ emissions, which were dominated by enteric CH₄ emissions (97.6%); but bomas were a substantial source for N₂O, contributing over 32% to total N₂O emissions on the farm. Annual manure emission factors were 2.43 ± 0.42 %N for N₂O and 0.49 ± 0.07 %C for CH₄, which corresponds to 2.64 ± 0.37 g CH₄ kg^-1 volatile solids (VS). However, boma emissions are currently not captured in IPCC inventories because there is no category for them, and countries do not collect activity data for this emissions source. This likely leads to an underestimation of livestock GHG emissions from pastoral rangelands in sub-Saharan Africa. To mitigate boma GHG emissions, we suggest that manure should be removed regularly, or bomas should be relocated every few days/weeks to prevent excessive manure build-up and redistribute nutrients across the landscape. Boma manure can be used as fertiliser to grow crops and livestock feeds, preventing nutrient mining and ensuring rangeland productivity and resilience.

Keywords: Boma, kraal, manure, methane, nitrous oxide

Contact Address: Sonja Leitner, International Livestock Research Institute (ILRI), Mazingira Centre, Kabete Campus, Old Naivasha Rd., 00100 Nairobi, Kenya, e-mail: s.leitnercgiar.org