Abstract:
Disposal of Municipal Solid Waste (MSW) has been identified as a major environmental challenge in developing countries. Electricity generation has been identified as one of the ways for utilisation of MSW. Literature is scanty on the characterisation of MSW for optimal electricity generation in Nigeria. This study was designed to investigate the potential of electricity generation from MSW in Uyo metropolis, Nigeria.
Municipal solid waste of 100 kg were collected from ten selected sites in Uyo metropolis and segregated into eight components. Data for the estimation of total volume of MSW were collected through field studies and AkwaIbom State Waste Management and Environmental Protection Agency, and spot sampling method was used to sort the MSW. Calorific Values (CV) of the segregated MSW components: Organic Waste (OW); Paper-Carton Waste (PCW); Plastics Waste (PW); Textile, Leather and Wood Waste (TLWW); Glass Waste (GW); Iron and Metal Packaging Waste (IMPW); Inert Metal Waste (IMW); and Unknown Waste (UW), were determined using bomb calorimeter at 10% moisture content. A prototype power plant of 1 kW capacity was designed and constructed according to standard procedures to model electricity generation from MSW using two sets of 42 combinations of two and three ratios of segregated components based on literature. The first combination consisted of six different mix of PW/TLWW, PW/OW, PW/PCW, TLWW/OW, TLWW/PCW, and O/PW, across five different ratios (9:1, 8:2, 7:3, 6:4 and 5:5); while the second consisted of four different mix of PW/TLWW/OW, PW/TLWW/PCW, PW/OW/PCW, and TLWW/OW/PCW across three different ratios (5:4:1, 5:3:2 and 4:3:3). Linear programming model was used to obtain the CV of the mix and Dulong equations were used to determine the electricity potential of MSW. Data were analysed using ANOVA at α_0.05.
The estimated annual volume of MSW was 72,000 tonnes for a population of about 847500. The components were dissagregated into 66.3% OW, 18.4% PCW, 5.2% PW, 4.3% TLWW, 1.3% GW, 2.1% IMPW, 0.5% IMW, and 1.9% UW. The CV of the components obtained for OW, PCW, PW, TLWW, GW, IMPW, IMW, and UW were 18.0, 17.0, 40.0, 32.0, 0.0, 0.0, 0.0, and 18.0MJ, respectively. The CV of PW/TLWW, PW/OW, PW/PCW, TLWW/OW, TLWW/PCW, and OW/PCW at 9:1 mix were 39.20±0.70, 37.80±0.63, 37.70±0.43, 30.60±0.71, 30.50±0.57, and 17.90±0.68 MJ, while at 6:4 mix, the CV were 36.80±0.81, 31.20±0.56, 30.80±0.21, 26.40±0.45, 26.00±0.44, and 17.60±0.42 MJ, respectively. The CV of PW/TLWW/OW, PW/TLWW/PCW, PW/OW/PCW, and TLWW/OW/PCW at 5:4:1 mix were 34.60±0.54, 34.50±0.53, 28.90±0.35, and 24.90±0.32 MJ, while at 4:3:3 mix, the CV were 31.00±0.69, 26.50±0.55, 26.50±0.45, and 23.30±0.46 MJ, respectively. The estimated power potential ranged from 5.0 to 8.0 MW. The highest potential was obtained for PW/TLWW ( 9:1), while the lowest potential was obtained for OW/PCW (5:5) operating at 160.93 tonnes/day. There was no significant difference between the estimated power potential and the published data for same mix ratios.
The use of municipal solid waste for electricity generation is feasible in Uyo metropolis. Improved waste mix of plastics, textiles, wood and leather gave the highest electricity generation potential.
