Methane release from enteric fermentation and manure management of domestic water buffalo in Nepal.

Methane (CH4) emission in livestock arises from enteric fermentation (EnF) and manure management (MM). This study develops the country-specific CH4 emission factors (EFs) in both EnF and MM for domestic water buffalo (Bubalus bubalis) and estimates total CH4 emission in Nepal using Intergovernmental Panel on Climate Change (IPCC) Tier 2 methodology. Seasonal field data were collected on morphological characteristics, feed characteristics, and manure management practices of the buffalo. The buffalo population was divided into five age groups, and at least 35 buffalo individuals were measured from each age group in the Hilly and Plain regions of Nepal in the winter and summer seasons. Buffalo adult male (BAM) had the highest body weight of 530 ± 53 kg in the plain region and 514 ± 65 kg in the Hill region. Similarly, the weight of buffalo calf (BC) was 91 ± 25 kg in the plain region and 77 ± 26 kg in the Hill region. For different age groups of buffalo, EnF EFs ranged from 34 ± 8 to 90 ± 10 kg CH4 head-1 year-1 and MM EFs ranged from 2.5 ± 0.5 to 7.5 ± 0.5 kg CH4 head-1 year-1. The estimated EnF and MM EFs of buffalo were not statistically different by region (p > 0 .05). The total CH4 flux from buffalo was 347.8 Gg year-1 in Nepal, contributing 322.2 Gg year-1 from EnF and 25.6 Gg year-1 from MM. The country-specific EFs are highly recommended for precise computing of the national emissions and carrying out mitigation action.

Methane emission factors and carbon fluxes from enteric fermentation in cattle of Nepal Himalaya.

This study presents a first estimate of the country-specific enteric methane (CH4) emission factors (EFs) and the net CH4 fluxes for the local and improved cattle breeds (LCB and ICB) in Nepal using the IPCC Tier 2 methodology. The country-specific herd structure, morphological and feed characteristics data of cattle were collected from the field survey. In LCB, adult males had the highest mean live body weights (BWs) ranging from 222 ± 42 kg in the Hill to 237 ± 36 kg in the Plain region, while for improved cattle, adult females had the highest BW of 334 ± 45 kg in the Hill to 308 ± 38 kg in the Plain regions. Weight gains of ICB were higher than the LCB. Local calves gained BWs of 97 ± 20 g day-1, while improved calves gained a weight of 202 ± 41 g day-1. The CH4 EFs ranged from 13 ± 3 to 46 ± 9 kg CH4 head-1 yr-1 for different age-groups of the LCB, while for the ICB, the EFs ranged from 14 ± 3 to 75 ± 15 kg CH4 head-1 yr-1. Overall, the EFs were 33 ± 7 and 46 ± 9 kg CH4 head-1 yr-1 for LCB and ICB, respectively. The estimated enteric EFs of cattle in the Hill and Plain regions were not statistically different (p > 0.05), but a significant difference existed between the breeds (LCB and ICB; p < 0.05). The net CH4 flux was 254 ± 51 Gg yr-1 from enteric fermentation in cattle of Nepal using the country-specific EFs, about 15% higher than using the default EFs (221 ± 66 Gg yr-1). We underline that the emission estimation, deploying the country-specific EFs, will be more accurate, contributing to reduce the uncertainties in the national GHG inventories and supporting the mitigation actions.