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

Abstract

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.