Proceedings

Current concerns related to energy supply and carbon abatement have altered perceptions of
industrial and municipal waste streams toward considering them to be resources. Biochemical
conversion of biomass crops, sludge or co-digestion for recovery of energy carriers such as
methane and hydrogen through anaerobic digestion and dark fermentation are promising
pathways from which sustainable energy fuels can be produced. Two-stage acidogenic and
methanogenic continuous anaerobic processes have been widely studied and adopted in the
water industry.

In this study, a mathematical model for mesophilic two-stage system (CSTR/UAF) including
hydrogenogenic and methanogenic reactors is presented. The model is based on mass
balances applied over a number of relevant chemical and microbial species. The model
concept is implemented in a MATLAB™/Simulink™ framework and is a development of the
widely applied IWA Anaerobic Digestion Model No.1 Batstone (2006). The model has been
modified to incorporate degradation intermediates and kinetics of biosolids hydrolysis as well
as variable product fermentation yields as function of operational conditions. Wheatfeed,
which was identified as one of the potential energy source for bio-hydrogen fermentation in
UK, was selected as the substrate for this study. The model can simulate the performance
and dynamics of the two stage system’s reactors.

KEYWORDS
Biomass, two-stage fermentation, methane, hydrogen, ADM1, modelling, hydrolysis