Emission of CO and CO2 from Straw Burning Activities in Hanoi City, Vietnam: A Major Rice Cultivation Area in the Red River Delta

Abstract

Globally, biomass burning significantly contributes to air pollution and climate change. In Vietnam, agricultural waste burning, particularly rice straw, is a common practice that exacerbates these issues. Hanoi, a major rice cultivation area in the Red River Delta, faces severe air pollution due to straw burning. The research quantified the above-ground biomass (AGB) for the Winter-Spring crop of 2023 in Hanoi by integrating Sentinel-1A imagery with an artificial neural network (ANN) model to develop a biomass inventory and assess the residual straw remaining in the fields. Following this, it estimated emissions and modeled dispersion utilizing the Atmospheric Dispersion Modelling System (ADMS) alongside meteorological data. Findings revealed that the AGB predominantly ranged from 3.1–4.0 kg/m² (approximately 49,000 ha), with a total projected residual straw of around 109,000 tons, primarily contributed by Ung Hoa district, exceeding 12,000 tons. The overall emissions from straw combustion during this crop were approximated at 42,831.92 tons of CO and 542,076.93 tons of CO₂, with CO₂ levels being approximately 12.66 times higher than those of CO; emission hotspots were primarily located in the southern and southwestern suburban districts, including Ung Hoa, My Duc, and Phu Xuyen. The ADMS dispersion simulation indicated that the area impacted by CO₂ was larger than that affected by CO, with urban districts, despite the absence of straw burning, still experiencing minimal diffusion effects (recorded emission levels in core districts were roughly 0–3 tons of CO and 0–50 tons of CO₂). These outcomes provided comprehensive insights into the magnitude and spatial distribution of emissions arising from straw burning in Hanoi, highlighting that the burning of agricultural residues is a concern not only for rural areas but also for urban air quality. Our findings highlight the significant impact of straw burning on local air quality, emphasizing the need for effective management strategies. The integration of remote sensing, biomass inventory, and dispersion modeling, as illustrated in this research, could serve as a robust scientific framework for the development of strategies addressing agricultural residue management and air pollution control policies.