Nepal Emission Inventory (NEEMI): a high resolution technology-based bottom-up emissions inventory for Nepal 2001–2016
Authors: Sadavarte Pankaj , Rupakheti Maheswar , Bhave Prakash V. , Shakya Kiran , Lawrence Mark G. 
Published: March 2019

Abstract. The lack of a comprehensive, up-to-date emission inventory for the Himalayan region is a major challenge in understanding the regional air pollution, including its impacts, mitigation, and the relevant atmospheric processes. This study develops a high resolution (1 km × 1 km) present-day emission inventory for Nepal with a higher-tier approach (detailed) to understanding the current combustion technologies and sectoral energy consumption. We estimate emissions of aerosols, trace gases and greenhouse gases from five energy-use sectors (residential, industry, commercial, agriculture and transport) and an open-burning source (agro-residue) for the period 2001–2016 (with 2011 as the base year), using bottom-up methodologies. Newly-measured country-specific emission factors (EFs) are used for emission estimates. It is estimated that the national total energy consumption in 2011 was 378 PJ with the residential sector being the largest energy consumer (79 %), followed by the industry (11 %) and transport (7 %) sectors. Biomass is the dominant energy source contributing 88 % to national total energy consumption, while the share of fossil fuel is only 12 %. With regards to open burning of the crop waste, it is estimated that 9.3 million tons of agro-waste was burned after harvesting crops in 2011. Nationally, 8.4 Tg CO2, 666 Gg CH4, 2.5 Gg N2O, 72 Gg NOX, 1984 Gg CO, 477 Gg NMVOC, 239 Gg PM2.5, 28 Gg BC, 99 Gg OC and 28 Gg SO2 were emitted from these sources in 2011. The energy consumption was also estimated for each year for the period 2001–2016 which shows an increase by a factor of 1.6 in 2016, while the emissions of various species increased by a factor of 1.2–2.4 with respect to 2001. An assessment of the top polluting technologies shows high emissions from traditional cookstoves using firewood, dungcakes, and agricultural residues, and open burning emissions of wood and residues. In addition, high emissions were also encountered from fixed chimney Bull's Trench kilns for brick production, cement kilns, two-wheeler gasoline vehicles, heavy diesel freight vehicles and kerosene lamps. A GIS-based gridded 1 km × 1 km population density map incorporating land-use and land cover data, settlement points, and topography was used for the spatial distribution of residential emissions. Geospatial locations were assigned to point sources, while activity-based proxies were used for other sources. Emissions were apportioned across different months from brick production, the agriculture sector, diesel generators, and space and water heating, using respective temporal variations of the activities. It was found that April had the maximum PM2.5 emissions, followed by December, January and February. Also, a wide variation in emissions distribution was found, highlighting the pockets of growing urbanization and the detailed knowledge about the emission sources. These emissions will be of value for further studies, especially air quality modelling studies focused on understanding the likely effectiveness of air pollution mitigation measures in Nepal.