Conversion of Water Hyacinth Derived Biogas to Biomethane for Electricity Generation in Kenya: A Waste to Energy (WtE) Approach.

Abstract

Water hyacinth a freshwater weed that thrives in polluted water was used as feedstock for Biogas production. The weed is removed from the water bodies by manual, mechanical, biological or chemical means. Manually and mechanically uprooted Water hyacinth poses a great environmental and public health challenge. This has developed an environmentally sound method of utilization of weed from Lake Victoria, Kenya as feedstock for biogas production. The uprooted weeds were pulped and mixed with water at a ratio of 1:1 and 1:3 with cow dung to supplement decomposition microorganisms. The mixture was loaded into bioreactor and gas yield, physicochemical parameters and bioreactor temperatures monitored during the production period. Gas compositional analysis of the biogas was carried out with a Gas Chromatograph coupled with a Thermal Conductivity detector (GC-TCD). The Biogas contained 49 - 53% methane, 30 - 33% carbon dioxide, 5 - 6% nitrogen and traces of Hydrogen sulphide. Optimal gas production occurs at the 21st day after feeding the digester. The biogas was upgraded into Biomethane using a series of cleaning devices; hydrogen sulphide scrubber, water scrubber and a carbon dioxide wet scrubber. Upgrading of the gas led to gas that that was of very high purity - Biomethane. The Biomethane was used to run internal combustion engine coupled with a generator for electricity production. Biomethane production from water hyacinth was found to be an environmentally and energy friendly project since it promotes Waste to Energy (WtE) technologies. Analysis of bioreactor effluents also produced a high quality bio-fertilizer.