3. Results and discussion
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Feed to water dilution ratio
3.1. Influence of water dilution on biogas generation
The influence of water volume on cumulative biogas yield and
daily rate of biogas generation were shown in Figs. 2 and 3,
respectively. Feed to water ratio of 1:6 w/v gave the best cumulative
yields. Although, the four tested ratios all gave greater yields than
the control digester that had no water. Peak biogas production rates
recorded for feed to water dilutions ratios of 1:4, 1:6 and 1:8 w/v
were 130,150 and 143 mL/day, respectively. Also, the yield of 4 mL/
day occurred at day 3 for control while 1:10 gave maximum yield of
50 mL/day at day 4, as shown in Fig. 3. Using brewer’s spent grains;
Onwosi [22] reported an improved biogas production at the dilution
of 1:4 w/v but biogas production decreased as the dilution
increased to 1:10 w/v. Report by Fernando [23] showed that excess
dilution does not encourage bacterial cluster formation, which is
needed for excellent biogas production