ASSESSMENT OF CARBON DIOXIDE EXTRACTION IN A SOLID WASTE MANAGEMENT FACILITY, AKURE, NIGERIA

Abstract

Carbon dioxide (CO2) emissions from solid wastes is a major contributor to the acceleration of global warming. In Nigeria, CO2 capture has been limited to the energy sector only. There is need to explore the reduction of CO2 emissions from solid wastes through appropriate technologies. This study, therefore was designed to assess CO2 extraction by adsorbents in a Municipal Solid Waste (MSW) management facility in Akure, Nigeria. An exploratory study design with an intervention component was adopted. For a year, wastes brought to the MSW facility from three locations viz: markets, residences and roadside, were characterised and quantified monthly. Chemical characteristics of the wastes were determined using standard methods. Carbon-dioxide emissions were estimated from the MSW composition using the Intergovernmental Panel on Climate Change tools. Air CO2 levels were monitored during the dry and wet seasons using a P-Sense Plus CO2 meter AZ-7755(PSPCM) and seasonal variations computed. A CO2 extractor which uses adsorbents consisting of Sawdust + Potassium Hydroxide (SKH), Sawdust + Sodium Hydroxide (SSH) and Sawdust + Calcium Hydroxide (SCH), all at ratio1:1, was designed and fabricated. The adsorbents were integrated into the equipment to capture CO2 from 5 kg samples of solid wastes burnt under controlled conditions with five replicates for each adsorbents during each test. The potential CO2 in the solid wastes was determined by ultimate analysis, while the concentration of CO2 adsorbed was obtained by finding the difference between the concentration of the CO2 at the inlet and outlet chambers of the extractor measured with the PSPCM. The effectiveness of the extractor combined with the adsorbents was determined by comparing the adsorbed CO2 with the potential CO2. Data were analysed using descriptive statistics and ANOVA at The mean monthly wastes generation from the three locations were 1,004,130.8+742,394.6 kg (biodegradable wastes), 1,322,831.0+810,634.9 kg (plastics) and 1,330,813.5+400,412.4 kg (paper). The mean values for the chemical constituents of these wastes for the three locations, residential, roadside and market respectively were Nitrogen 2.7+0.6, 2.1+0.8 and 3.4+0.7%; Phosphorus 0.10+0.03, 0.10+0.03 and 0.10+0.04% and Carbon 53.2+1.4, 53.1+1.8 and 53.1+1.5%, with no significant difference within the groups. The estimated CO2 emissions was 1.2 Gg/Yr. The ambient CO2 levels ranged between 438.0+7.2 and 630.0+124.5 ppm in the dry season, and 407.3+11.3 and 506.9+71.1 ppm for the wet season. The mean potential CO2 in the solid wastes was 160.0+ 42.0 ppm. The mean CO2 adsorbed were 99.0+24.0 ppm, 45.0+24.1 ppm and 30.0+13.0 ppm for SKH, SSH and SCH respectively. The effectiveness of SKH in the capture of CO2 was 61.9 % as against 20.8 % and 18.8 % by SSH and SCH, respectively. The selected adsorbents were effective in capturing carbon dioxide. Incorporation of Sawdust + Potassium Hydroxide improves the effectiveness of carbon dioxide extraction in the solid waste management facility.