High organic loading rates and low sludge production are among the many advantages
anaerobic processes exhibit over other biological unit operations. But the one feature
emerging as a major driver for the increased application of anaerobic processes is the
energy production. Not only does this technology have a positive net energy production but
the biogas produced can also replace fossil fuel sources and therefore has a direct positive
effect on greenhouse gas reduction. This will most certainly ensure the ongoing, and likely
drastically increased, popularity of anaerobic digestion processes for waste treatment in the
future. But why is there a need for a generic model? Several benefits are expected from the
development of this first generic model of anaerobic digestion:
• increased model application for full-scale plant design, operation and optimization;
• further development work on process optimization and control, aimed at direct implementation
in full-scale plants;
• common basis for further model development and validation studies to make outcomes
more comparable and compatible;
• assisting technology transfer from research to industry.
Many of the above points relate to practical, industrial applications. Indeed, this is
one of the areas where most benefits from the application of a generalised process model
can be gained. While many different anaerobic models have been devised over the years
(and indeed form the basis of the ADM1), their use by engineers, process technology
providers and operators has been very limited. Two of the limiting factors have likely
been the wide variety of models available and often their very specific nature. We hope
that this model will help to achieve widespread utilisation of the large body of knowledge
of anaerobic processes available from research studies and operational experience.
Ultimately the model will support the increased application of anaerobic technology as a sustainable waste treatment option and a viable alternative to other energy generating
processes.
In this paper, the model structure, kinetic rate equations (Appendix) as well as implementation
in a simple fixed volume CSTR are presented. An IWA Scientific and Technical
Report (STR) was published in early 2002 (Batstone et al., 2002), and contains a more complete
discussion of the included processes, a review of parameter values, and a suggested
base parameter set. Specific limitations of the model, the influence of these limitations on
outcomes, and a conceptual approach to correcting for them are also discussed in the form
of inserts.