Estimation of Methane (CH4) Emission by Ruminants due to Enteric Fermentation -A Preliminary Study in Sri Lanka

Abstract

Methane emission of ruminants due to enteric fermentation is an important subcategory considered globally under the agriculture sector greenhouse gas emissions. A preliminary study was undertaken to estimate the CH4 emission due to enteric fermentation of ruminants in different production systems in Sri Lanka. Further it was aimed to use the emission data as a tool to develop future research on appropriate adaptation and mitigation strategies. Animal population statistics during the period from 2003 to 2014 were obtained from the Departments of Census and Statistics. Emissions from enteric fermentation were calculated using the guidelines given in Intergovernmental Panel on Climate Change (IPCC 2006) for tier 1 National Greenhouse Gas Inventories. Total CH4 emission from cattle through enteric fermentation was highest (P<0.05) in low country dry zone (385.19 Gg) compared with the coconut triangle (138.93 Gg). Total CH4 emission from enteric fermentation was 96.01 Gg for the low country wet zone and intermediate zone while up and mid country showed the lowest (P<0.05) value of 89.79 Gg. Results reveal that, estimated values are mainly related (R2=0.96) to the herd size in different zones. Further, in the low country dry zone, majority of herd composed of indigenous, zebu and their crosses with low number of productive and higher number of unproductive animals including bulls. Due to extensive management system, poor quality of forages, and occasional use of draught power lead to high maintenance requirement in animals* Therefore higher CH4 emission was estimated compared to other production systems. In contrast, mid and up country consisted pure European breeds and their crosses reared mainly under intensive management system. Therefore CH4 emission estimated to be lowest due to low mobility. When considering the CH4 emission from buffaloes, low country dry and intermediate zones showed highest values (126.22 Gg) due to the existence of highest numbers of buffaloes. Contributions of goat and sheep were negligible due to their low body size and low population. CH* emission values estimated in this study will be helpful in improving the emission estimates for future greenhouse gas inventories to be produced in the country as well as to use as a tool to develop future research.