Emission factors and emission inventory of diesel vehicles in Nepal.

A comprehensive emission inventory of the transport sector through fuel-based emission factors (EFs) was developed for the first time in Nepal. This study estimates air pollutants emission from diesel vehicles between the years 1989 and 2018 based on national statistical data, average vehicle kilometers travelled, fuel mileage, and measurement-based EFs for each vehicle category during idle and moving conditions. The consumption of diesel by vehicle category was also estimated and total consumption was compared with national sales data. The Monte Carlo was used to estimate uncertainties. Nationally, total diesel consumption was estimated as 892,770 kL (85-115%) in 2017/18, 13.4 times higher than 1989/90. Ratnoze1 and Microaeth were used to conduct the tail pipe emission measurements. The fuel-based EFs of CO2, CO, BC, and PM2.5 were calculated through the carbon mass balance method. Of all diesel vehicles measured (n = 29) during idling, the average EFs were estimated as CO2 2600 (99-101%), CO 33.3 (44-156%), BC 0.6 (25-101%), and PM2.5 5.2 (0-235%) in unit of g L-1. For moving conditions (n = 5), the average EFs were estimated to be CO2 2476 (90-110%), CO 97.3 (0-232%), BC 1.7 (46-110%), and PM2.5 20.7 (0-255%), all in g L-1. Multiplying fuel consumption by EFs, national air pollutant emissions were estimated as 2214 (90-110%) to 2781(85-115%) for CO2, 27.7 (42-158%) to 88.8 (0-232%) for CO, 0.51 (23-177%) to 3.55 (46-110%) for BC and 3.42 (0-236%) to 23.47 (0-255%) for PM2.5 in 2017/18 in unit of Gg. This paper recommends revising national vehicle mass emission standards based on the findings of this study and including and enhancing sustainable low-carbon transport through amendment of transport policy.

A model-ready emission inventory for crop residue open burning in the context of Nepal.

Open burning of crop residue is an important source of air pollution which is poorly characterized in South Asia. Currently, the gridded inventory reported by Global Fire Emissions Database for biomass burning including open burning of crop residue are of coarse resolution (0.25° × 0.25°), and may not be appropriate for a simulation for Nepal. This study develops a comprehensive high resolution (1 km × 1 km) gridded model-ready emissions inventory for Nepal to understand the spatial characteristics of air pollutant emissions from open burning. We estimate the national air pollutant emissions from crop residue burned between the years 2003 and 2017. The best available data on agricultural production, residue consumption patterns, agricultural burning parameters and emission factors were derived from secondary sources. The Monte Carlo method was used to estimate uncertainties. The mass of crop residue burned in 2016/17 was 2908 Gg (61-139%), which was 22% of the dry matter generated that year. By multiplying the burned crop residue mass by emission factors, the air pollutant emissions were estimated as 4140 for CO2 (56-144%), 154 for CO (4-196%), 6.5 for CH4 (7-193%), 1.2 for SO2 (60-140%), 24.5 for PM2.5 (30-170%), 8.6 for OC (38-162%), 2.2 for BC (-1-201%), 7 for NOx (54-146%), 22.5 for NMVOC (8-192%) and 2.7 for NH3 (3-197%) in unit of Gg yr-1. More than 80% of air pollutants were generated during the months of February to May from the open burning of crop residue. The findings of this paper indicate that substantial reduction in open field burning would dramatically improve air quality in both the Terai region and other parts of Nepal and help reduce negative health impacts associated with the open burning of residue such as premature deaths, respiratory disease, and cardiovascular disease.

Estimating emissions from open burning of municipal solid waste in municipalities of Nepal.

Open burning of municipal solid waste (MSW) is a poorly-characterized and frequently-underestimated source of air pollution in developing countries. This paper estimates the quantity of MSW that was burned in five erstwhile municipalities of the Kathmandu valley, Nepal. A household survey, a transect walk survey, an experiment to measure the fraction of waste that is combustible, a survey on fraction of population burning waste outside their houses, and a survey of the fraction of MSW burned at dump sites were performed in this study, whereas burning/oxidation efficiency, municipal populations, MSW generation rates, and emission factors were derived from the literature. The total mass of MSW burned during 2016 is estimated to be 7400 tons (i.e., 20 tons/day), which was of 3% of the total MSW generated in the valley municipalities that year. This exceeds Government estimates by a factor of three. Multiplying the burned MSW mass by emission factors, the air pollutant emissions are estimated as PM2.5 55 tons (OC 42 tons and EC 1.4 tons), PM10 60 tons, BC 25 tons, CO2 11,900 tons, CH4 30 tons, SO2 5.0 tons, NOx 19.2 tons, CO 630 tons, NMVOC 112 tons, and NH3 5.7 tons per year. Open burning of MSW can trigger health impacts such as acute and chronic respiratory disease, heart diseases, and allergic hypersensitivity, in addition to impacts on local climate. Improved waste-segregation practices at the source and waste-collection systems throughout the valley are needed to mitigate this pollution source and its effects.