Greenhouse Gas Emissions from Manure Management and Its Response to Farming System Dynamics in the Addis Ababa Milkshed, Salale Highlands of Ethiopia

Manure management in dairy production contributes considerably to greenhouse gas (GHG) emissions in agriculture. Intensification of the sector led to increased volumes of manure accumulation, which emit GHGs like methane (CH4) and nitrous oxide (N2O). It is crucial to have reliable information in order to contribute to global efforts to reduce CH4 and N2O emissions from manure management and utilization practices. The present study was designed to develop country-specific improved (Tier II) emission factors (EF) for manure CH4 and N2O across farming system dynamics based on animal energy requirements derived from animal performance and feed characterization data of about 2500 cattle from three smallholder dairy farming systems (Urban, Peri-urban and Rural) in the Salale highlands. Our result showed that there was significant variation in manure CH4 and total N2O EFs across the farming systems. The predicted EF values for mature dairy cows in urban, peri-urban, and rural farming systems were 14.89, 11.68, and 3.19 kg CH4 head-1 year-1, and 0.62, 0.53, and 0.21 kg N2O head-1 year-1, respectively. The maximum CH4 and N2O EFs were reported for matured dairy cattle in urban farm. Smallholder rural farm showed significantly lower CH4 EFs and N2O for matured dairy cattle compared to urban and peri-urban farms. Compared with IPCC default values (2019), our values for CH4 EF are higher than those in the IPCC (2019) for sub-Saharan Africa. This study can serve as a baseline in the national emissions inventory to evaluate the effectiveness of future interventions, potentially improving the country's commitment to reduce GHG emissions. Increasing the proportion of manure used for composting and biogas instead of dung cake as fuel would result in an increase in organic manure and renewable energy sources on farms, thereby improving nutrient use efficiency and reducing greenhouse gas emissions.