Biogas plant
• A golden rule is: the plant belongs to the stable rather than to the kitchen. Preferably,
the mixing chamber and inlet are directly connected to a concrete stable floor. A few
meters of piping are more economic than the daily transport of dung from the stable
to the biogas plant.
• The roof of the stable should neither drain on the digester nor on the soil covering the
plant. Large amounts of water entering the ground around the plant weaken the soil
and cause static instability. Excess rain water may cool down the slurry in the plant
and cause the gas production to drop.
• The overflow point should guide into farmland owned by the plant user. It has been
observed that plants which overflow on public or foreign land can cause social
problems. A promise of the owner to remove the slurry daily should not convince the
planner.
• Water traps in the piping are a constant source of trouble. If the site allows, the plant
and its piping should be laid out in a way that a water trap in the piping can be
avoided. This is only possible if the pipes are sloping all the way back to the plant.
• The piping is a major cost factor. It
should not be unnecessarily long. This
criterion, however, is given less priority
than having the stable close to the inlet
and the outlet directed towards the
farm land.
• A fixed dome plant should not be
located in an area required for tractor
or heavy machinery movements.
• Trees should not be too close to the
plant. The roots may destroy the
digester or the expansion chamber. In
addition older trees may fall and
destroy parts of the plant. If the
position of the biogas plant is too
shady, the soil temperature around the
plant will be low in general. This leads
to a decrease in gas production.
• The area around a biogas plant should
not be a playground for children. This
is less important for underground fixed
dome plants, more important for
floating drum plants and essential for
balloon plants.
Figure 24: A model of an agricultural
digester in Germany with two horizontal
steel tanks, a gas storage bag and a co-
generation unit in a container.
Photo: Krämer (TBW)
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