iogas production study was conducted for water hyacith/cowdung mixture and cowdung only.
Figure 2. Temperature variation within the biogas digester.
Figure 3. pH variations within the biogas digester.
The results are presented in Figure 7. The cowdung feedstock was found to produce biogas from the fourth day rising to a high on the eigth day which remained almost constant reaching a maxima between the 28 - 36th day.
The biogas production from the water hyacith/cowdung mixture showed a different trend; biogas production remained low than that from cowdung between the fourth and the18th day but rose steadly to reach a maxima at the 32nd day and remained constant up to the 36th day. The trends show a rather similar trend bu the delay during the first few days for water hyacinth/cow dung mixture can be attributed to the low bacteria population in the matrix. The study shows a greter yield of biogas from the hyacinth/cow dung mixture compared to cow dung. The results of the study agree with those reported by other researchers using water hyacinth as a feed stock  -  .
The study shows that E. crassipes is a good feedstock and that can be utilized as a renewable energy source. The
Table 2. Biogas composition after upgrading.
Figure 6. Chromatogram for upgraded biogas.
Figure 7. Biogas production with time (days).
production profiles compares well with those of conventional feed stocks such as cow dung. The utilization also provide an innovative way of managing the invasion of the weed in freshwater bodies in an environmentally sound manner.
The authors gratefully acknowledge to the Japan International Cooperation Agency (JICA) and BRIGHT project of JICA for the financial support throughout this study.
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