Developing new methane emission factors and quantifying methane emission from Beninese cattle production

Recent greenhouse gas (GHG) inventories carried out in The Republic of Benin have shown that cattle are the major emitters of livestock-related GHG. Due to the unavailability of national emission factors (EF), most of the previous GHG inventories were conducted according to the Tier 1 method based on the use of default EF suggested by the Intergovernmental Panel for Climate Change (IPCC). The use of Tier 1 presents accuracy limits. Thus, this study was conducted to develop country-specific EF; the use of which in future inventories of methane (CH₄) emitted will provide data that will be more accurate. EF was calculated for six local breeds: zebu cattle (Gudali, White Fulani, and Azawak) and humpless cattle - Bos taurus (Borgou, Lagune, and Somba). We calculated EF for CH₄ emitted from enteric fermentation and manure management following the Tier 2 methods. Firstly, we characterized and categorized the cattle population according to species, breed, sex, and age. Then, the gross energy (GE) intake for each category was calculated. Finally, the categorical EF and total CH₄ emitted for the period 1999-2019 were calculated and determined. The results revealed great EF heterogeneity within species, breeds, and age groups. The national enteric EF of 57.91 kg CH₄ head^-1 year^-1 was obtained for all cattle. The EF for CH₄ emitted from manure management was 1.60kg CH₄ head^-1 year^-1. The highest (73.74 kg CH₄ head^-1 year-¹) and the lowest (34.90 kg CH₄ head^-1 year^-1) were recorded in Azawak and Lagune cattle, respectively. CH₄ emissions were mainly emitted from enteric fermentation, with an annual average of 2849.59 Gg CO₂eq, accounting for 97.31 %. Manure-related emissions were yearly at 78.71 Gg CO₂eq, representing 2.69 % of total CH₄ emissions.