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