GHG emission from diesel-powered irrigation pumps and mitigation potentials in agriculture sector of Nepal

Emissions from diesel-powered irrigation pumps (DIPs) in Nepal's agriculture sector contribute to climate change and local air pollution. This study presents the emission estimation using emission factors (EFs) for energy use in DIPs and estimates the contribution of DIPs to the GHGs emission in Nepal using both the bottom-up and top-down approaches. It involves analyzing data on the number of DIPs, the amount of fuel used for irrigation, hours of operations, and efficiency of the pumps. The various EFs for the DIPs were collected from the previous research reports and articles. The activity data for the bottom-up approach was collected from a telephone survey, field sampling, and review of the existing documents. The country-specific EFs for energy use in DIPs developed in Nepal by previous studies using sample measurements were used in this study. The estimated number of DIPs for 2024 is about 51,137 (1.5 to 9 hp; average 5 hp DIPs), operating an average of 192 h per year in Nepal. The DIPs consume 5891 m³ (kL) of fuel per year and emit 14,674 tons of CO₂, 20.9 tons of CH₄, 0.18 tons of N₂O, 71.3 tons of NO_x, 52.2 tons of non-methane volatile organic carbon (NMVOC), 332.0 tons of CO, 54.4 tons of PM_2.5, 40.30 tons of organic carbon (OC), 17.8 tons of black carbon (BC), and 0.6 tons of SO₂ each year. The number of solar-powered irrigation pumps (SIPs) is 3129, which is about 2% of total irrigation pumps in Nepal. Farmers are providing encouraging feedback on the use of SIPs in their small-sized farms. The study shows that the number of electricity-powered pumps has increased rapidly by replacing the DIPs after the mid-2010s due to increased access to the grid electricity. The assessment is expected to support identifying opportunities to reduce emissions through improvements in technology, management practices, and other strategies.