Environmental Engineering Reference
In-Depth Information
8.1
Components of plant design.
fundamental elements. The chemical and biological composition of the
substrate or the biogas determines the construction materials needed in
order to avoid corrosion. The amount of substrate or gas defines the
dimensions or capacity of each plant element. Adapted technology and
correct engineering are the basis for a well-functioning biogas plant. It is
therefore of vital importance to study the feedstock and the local conditions
carefully before taking any design decisions.
8.2
Digestion unit
The digestion unit is the heart of a biogas plant; this is where microbial
activity takes place and organic matter is transformed to biogas. The
digestion unit is composed of one or several digesters, including feeding,
agitation and heating systems. A pre-digestion tank and a post-digester may
complete the unit. The technological possibilities are vast, with choices
depending mainly on feedstock characteristics such as dry matter content,
degradation rate, contaminant and inhibition risks. The main options and
designs of different plant components are described in this chapter. Table
8.1 summarises the main processing options for the key parameters of a
digestion unit.
8.2.1 Feeding systems
Feeding systems bring the substrates from their storage place into the
digester, making the transition from aerobic to anaerobic conditions. They
can be simple structures for substrate transport, but there are also elaborate
systems that simultaneously allow intermediate storage, mixing, milling,
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