Methane from cattle waste: Effects of temperature, hydraulic retention time, and influent substrate concentration on kinetic parameter (k)

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Abstract
The effects of temperature (35 and 55°C), influent volatile solids (VS) concentration (S0 = 43, 64, 82, 100, and 128 kg VS/m3) and hydraulic retention time (HRT = 4, 5, 8, 10, 15, and 25 days) on methane (CH4) production from cattle waste were evaluated using 3‐dm3 laboratoryscale fermentors. The highest CH4 production rate achieved was 6.11 m3 CH4 m−3 fermentor day−1 at 55°C, four days HRT, and S0 = 100 kg VS/m3. Batch fermentations showed an ultimate CH4 yield (B0) of 0.42 m3 CH4/kg VS fed. The maximum loading rates for unstressed fermentation were 7 kg VS m−3 day−1 at 35°C and 20 kg VS m−3 day−1 at 55°C. The kinetic parameter (K, an increasing K indicates inhibition of fermentation) increased exponentially as S0 increased, and was described by: K = 0.8 + 0.0016 e . Temperature had no significant effect on K for S0 between 40 and 100 kg VS/m3. The above equation predicted published K values for cattle waste within a mean standard error of 7%.