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.

Key words: Solid waste, gasification, waste to energy, rice husks, saw dust, maize combs, syngas