Survey-based inventory for atmospheric emissions from residential combustion in Vietnam

Local questionnaire surveys were conducted to collect representative activity data for calculation of annual emissions from residential combustion in Red River Delta (RRD), Vietnam, for 2010-2015. Multistage statistical sampling was implemented in the surveys for Hanoi Metropolitan Region (HMR) and deep rural area of Ninh Binh province (Con Thoi, Ninh Binh (CTNB)). Emission factors were scrutinized to select relevant ranges and central values for typical cookstoves in RRD. Large differences in the activity data (cooking activities, fuel-stove types, and fuel consumption) were found between three HMR strata (urban, suburban, and rural populations) and CTNB, respectively, which resulted in distinctly different annual emissions per capita. Annual 2010 emissions from residential combustion in RRD were estimated for toxic pollutants, in Gg/year, of 217 for CO, 1.5 NO_x, 7.4 SO₂, 33 NMVOC, 3.7 NH₃, 16.9 PM_2.5, 1.4 BC, and 7.1 OC, along with 171 t/year of total PAHs with 0.7 t/year of BaP, and greenhouse gases of 5395 CO₂, 17.2 CH₄, and 0.7 N₂O Gg/year. Emissions increased by 1.5-7.8%, varying with species, over the 6-year period. Prevalent use of crop residue in CTNB induced its dominant shares in the residential combustion emissions not only in this deep rural area but also in the entire RRD domain. Spatial emission distribution exhibited high intensities over districts having high rural population density. Global warming potential results indicated the dominant role of black carbon, especially over the 20-year horizon. Switching from solid fuels to liquefied petroleum gas would reduce the emissions from this sector and bring in multiple benefits.