Environmental Engineering Reference
In-Depth Information
4.1
Lignocellulose complex in plant cell walls (courtesy of Lydia
Rachbauer).
wastewater or bioethanol industries. There are a huge number of pre-
treatment technologies and it is often difficult to assess which ones are
worthwhile. Claims by manufacturers about the abilities of their technol-
ogies must be viewed with caution, as they often neglect to mention the
disadvantages. Research carried out on behalf of these companies may also
be misleading. Even other research is not always neutral, as every researcher
has a specialist area and a preferred technology. It is difficult to draw a
conclusion from the vast amount of studies published using different pre-
treatment methods on different substrates. This is partly because costs are
rarely considered in research papers. In addition, technologies that look
promising at small scale in batch fermentation may not be effective at large
scale in continuous fermentation. Different technologies and the positive
and negative aspects of the technologies are now discussed.
4.3.1 Physical pre-treatment
Mechanical pre-treatment
Mechanical pre-treatment is a simple form of pre-treatment aimed at
increasing the specific surface area and availability of biomass. In addition
to increasing biogas yield, particle size reduction also has an effect on the
viscosity in digesters and reduces the formation of floating layers that cause
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