Country-specific emission factors for methane emission from enteric fermentation: a case study from a non-annex 1 country

Methane emission from enteric fermentation is a subcategory considered under the Agriculture sector greenhouse gas emissions under the United Nations Framework Convention on Climate Change (UNFCCC). So far, most non-annex 1 member countries have used the default IPCC 1996 revised guidelines in estimating such emissions. The latest IPCC 2006 revised guidelines for national greenhouse gas inventories provide better guidelines for developing country-specific emission factors. Countryspecific methane emission factors were developed for estimating methane emission from enteric fermentation in livestock in Sri Lanka, using a Tier 2 approach with energy calculations (IPCC, 2006) based on country-specific activity data. Each animal category was further subdivided for the analyses, and emission estimates incorporated population characteristics in the different agro-climatic zones of the country. Separate emission factors were calculated for sub categories within the local (indigenous) and improved (Indian and European) breeds. The population-weighted methane emission factor (50 kg head-1 yr-1) estimated for dairy cows (i.e. lactating females) was lower than the IPCC default value. The methane emission factors calculated for other cattle categories ranged between 11 – 58 kg head-1 yr-1. However the population-weighted emission factor (32 kg head-1 yr-1) was slightly higher than the IPCC default value (27 kg head-1 yr-1), as the proportion of the calves in the other cattle population was relatively lower (~47 percent) than what the IPCC default emission factor has considered. Overall, the population-weighted emission factors for buffaloes (49 kg head-1 yr-1) and sheep (3 kg head-1 yr-1) were lower than the IPCC default values.