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describing the behaviour of process reactions and have been reported to
successfully predict digester operation, failure and remedies (Lyberatos and
Skiadas, 1999; Batstone et al., 2006). Proper modelling ought to take into
consideration both biochemical and physico-chemical reactions. The effect
of pH, temperature and gas-liquid phase mass transfer also must not be
ignored. The effect of inhibitors such as oxygen, chloroform, halogenated
organics, heavy metals, etc. should also be studied.
10.4.3 AD mathematical modelling: current status and
perspectives
Astals et al. (2011) stated that 'the power of the models lies in their capacity
to reproduce an empirical behaviour in a computer in a clear and
quantifiable manner, where the mathematical equations are able to simulate
the physical, chemical and biological processes'. One of the challenges in the
recent development of mathematical models is the capacity of the system to
simulate the AD process where two or more substrates are applied. One of
the key issues would be to predict the nutrient limitations for the process
(Astals et al., 2011). Gali et al. (2009) developed an ADM1-based model
suitable for anaerobic co-digestion of agricultural wastes. The work was
further extended by Astals et al. (2011) who accurately predicted the
degradation of pig manure and glycerine. Other examples of the
implementation of mathematical models for AD are given by, for example,
Rosen et al. (2006) and Nopens et al. (2009).
The information presented on mathematical modelling of the AD process
is not intended to give a full review of the existing literature. Given the large
number of scientific publications existing and new ones being constantly
published, it couldn't be - it is rather about underlining the idea of how
important, useful and powerful mathematical modelling is in process design,
operation, optimisation and, consequently, control.
10.5 Advantages and limitations of process control
The advantages of integrating process control in anaerobic digestion sectors
are multiple. Monitoring, managing and controlling AD in the future is a
must. The AD industries are becoming more and more mature and
advanced over time. In the near future, biogas production will play an
important role in an overall energy share and it will take over the position
from natural gas. All of this means that a constant and controllable flow of
biogas will have to be supplied to society.
As in other advanced fermentation industries, there is a great need for
optimised, on-line process control for the AD process. The AD sector is
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