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

• Published in: Water science and technology Vol. 60; no. 7; pp. 1829 - 1836
• Main Authors: Pabón Pereira, C P, Zeeman, G, Zhao, J, Ekmekci, B, van Lier, J B
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01-01-2009
• Subjects: Biodegradability; Biodegradation; Biodegradation, Environmental; Corn; Corn silage; Experiments; Hydrolysis; Inoculum; Kinetics; Mathematical analysis; Reactors; Silage; Silage - analysis; Zea mays; Zea mays - chemistry
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2009.549

The biodegradability and first-order hydrolysis coefficient of maize silage have been assessed from batch experiments using different types of inoculum and substrate to inocula (S/I) 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)% while the first order hydrolysis was 0.26 (+/-0.01) and 0.27(+/-0.02) d(-1), using granular and a mixture of granular and suspended inoculum, respectively. In the CSTR experiment biodegradability ranged from 41-65% depending on the HRT applied whereas the calculated first order hydrolysis coefficient was 0.32 d(-1). It is concluded that batch experiments can be used to assess first order hydrolysis 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 as 20 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.