ENERGY PRODUCTION FROM THERMAL GASIFICATION OF SELECTED MUNICIPAL SOLID WASTES FROM THIKA MUNICIPALITY OF KIAMBU COUNTY, KENYA

Abstract

Thermal gasification is a process that converts organic or fossil based carbonaceous materials into carbon monoxide, hydrogen and carbon dioxide. The waste dumped in the dumpsite consists of plastic papers, organic waste, textiles, rubber, rice husks, maize combs among others. The study aimed to determine the energy production potential from conversion of solid wastes to energy resources using thermal gasification. Selected carbonaceous waste such as rice husks, maize combs and sawdust were gasified in a fixed bed updraft gasifier to obtain synthetic gas (syngas) and carbonized residues. Samples of the syngas were collected in evacuated clean air tight plastic containers. 1 ml of the sample was injected into a gas chromatograph (GC-TCD) and the CO2, CO, CH4, H2, N2, and O2 concentrations were determined using a thermal conductivity detector (TCD). The study found that 25Kg of rice husks fed to the gasifier, produced 580±4.2m3 of syngas, with sawdust producing 480±2.8m3 and maize combs producing 420±3.1 m3 for the same weight of feedstock. Syngas from rice husks was found to contain 9.81±0.99% CH4, 28.55±0.99% CO, 12.59±0.99% CO2 7.44±0.99% N2, 8.34±0.99% O2 and 34.06±1%H2 while that from sawdust gave 12.06±1.13% CH4, 34.34±1.13% CO, 8.24±1.1% CO2 5.11±1.1% N2, 5.96±1.13% O2 and 34.4±1.1% H2. Maize cobs gave syngas of 24.74±2.70CH4, 27.90±1.64CO, 9.99±1.52CO2, 7.44±0.11N2, 11.97±0.58O2 and 30.32±0.74O2. The calorific value of syngas from sawdust was 16.17 MJ/m3 while rice husks had 13.18 MJ/m3 with maize combs giving 12.1 MJ/m3. The higher content of CH4 and CO in sawdust contributes to its higher calorific value than rice husks. The results obtained in this study are an indication that there is a high potential of energy production from carbonaceous waste.