Solid biomass energy consumption and air pollutant emissions projection for household energy use in Rwanda: An application of LEAP model

Abstract

In Rwanda, the utilization of solid biomass for household cooking needs is prevalent. The combustion of solid biomass releases a complex mixture of air pollutants that significantly degrade indoor and ambient air quality, thus negatively impact public health and the environment. To develop workable prevention and control methods that can enhance the quality of air and reduce human exposure to air pollutants and their effects, it is important to gather local, trustworthy data on solid biomass fuel consumption and emissions. This study seeks to estimate the emissions of seven main air pollutants from household solid biomass use in Rwanda. It uses a LEAP model to analyze the solid biomass energy consumption and air pollutants emissions projection for household energy use in Rwanda. The yearly solid biomass energy consumption in historical year was calculated by multiplying activity data by intensity of solid biomass type consumed and projecting taking the household’s growth as driving indicator. The current and projected air pollutants emissions of nitrogen oxides, carbon monoxide, volatile organic compounds, black carbon, organic carbon and particulate matters (PM10&PM2.5), from household solid biomass energy use were estimated. The Business As Usual scenario (BAU) was developed by taking into account the historical trends in household consumption and by considering household growth rate as a key factor influencing solid biomass consumption. Additionally, the scenario assumes that the current energy policy remains unchanged. The study focuses on solid biomass fuel consumption, including firewood, charcoal, and agricultural residue. It calculates historical emissions of air pollutants from 2005 to 2022, while also forecasts their potential levels until 2030 under a business-as-usual (BAU) scenario. The study has found that the total energy consumption from solid biomass reached 36.064 thousand Terajoule (TJ) in 2005, with firewood being the dominant fuel source, accounting for 32.38 thousand TJ. Looking at the overall projection for solid biomass energy demand, in the BAU scenario, the demand for solid biomass energy is anticipated to dramatically increase to 84.67 PJ. In the baseline year, the most significant emissions were attributed to CO at a magnitude of 186.19 kilotonnnes (kt), subsequently followed by NMVOCs, PM10, PM2.5,OC,NOX and BC at 20.17 ,18.06,14.5,6.32,3.61 and 1.91 kt respectively. By the end year (2030), there is a notable rise in air pollutant emissions, with carbon monoxide (CO) reaching a substantial level of 456.98 kt. This is slightly closely followed by NMVOCs, PM10, PM2.5, organic carbon (OC), nitrogen NOX, and BC at 42.4, 37.78, 30.5, 13.9, 8.47, and 4.34 kt, respectively. The findings of the study highlight a striking similarity between the growth in overall air pollutant emissions and the trend of solid biomass energy consumption.

v The study's findings also highlight the importance of concentrating efforts on tackling the rising trend in emissions to mitigate any potential environmental effects caused by an increase in household solid biomass use and enhance ambient and indoor air quality in residential areas.