Implications of reactor type and conditions on first-orderhydrolysis rate assessment of maize silage

摘要

The biodegradability and first-order hydrolysis coefficient of maize silage have been assessedfrom batch experiments using different types of inoculum and substrate to inocula (S//) ratios,and from CSTRs working at different hydraulic retention times (HRTs). In the batch experiments,the assessed maximum biodegradability of the maize silage was 68 (± 2.7)% and 73(±2.9)% whilethe first order hydrolysis was 0.26 (±0.01) and 0.27(± 0.02) d~(-1),using granular and a mixture ofgranular and suspended inoculum, respectively. In the CSTR experiment biodegradability rangedfrom 41-65% depending on the HRT applied whereas the calculated first order hydrolysiscoefficient was 0.32 d~(-1).It is concluded that batch experiments can be used to assess first orderhydrolysis constants and biodegradability provided that a well balanced inoculum is guaranteed.Further, it is shown that CSTR reactors digesting maize silage and operating at HRTs as low as20 days can attain 88% of maximum biodegradability as long as pH fluctuations are minimized.2 mmol NaHCO3 per gram maize silage was calculated to suffice for the purpose.