Page last updated 30/08/2018
Small-scale Rural Biogas Programmes
Chapter Abstracts - 3
There are two main types of plastic biogas plant: ones that use flexible plastic and those that use rigid
plastic to make plants that are similar to floating drum or underground plants. Flexible plastic systems
include "bag" digesters, where the whole plant is made from plastic and "membrane" digesters where
the plastic membrane acts as a gas holder over a pit made from masonry or other materials. Floating
drum designs also include systems in which the tank and gas holder are both made of plastic (Martin,
2008; Roos et al., 2004) or ones in which only the gas holder is of plastic and the digester tank is made
from masonry or other materials. Underground plants are also available in which the digester pit and
reservoir are both made of plastic. (21 references).
http://dx.doi.org/10.3362/9781780448497.007
Ancillary equipment used with a biogas plant includes slurry and gas handling equipment. Inlet slurry of
dung and water can be mixed with various types of machine. Food waste often requires a pre-digester.
Outlet slurry should be used as a compost. Gas equipment includes pipes, valves, manometers, stoves
and lights. Gas pipes can be made of several different materials, such as metal (steel or copper) and
plastic (HDPE, PVC, etc). The best valves to use for gas are ball valves. Gas stoves and lights need to
have been carefully designed and tested. Biogas can also be used in engines with suitable ancillary
equipment. (19 references).
http://dx.doi.org/10.3362/9781780448497.008
The process of building a biogas plant involves a series of decisions: the design of plant to be used; the
feed stock available and therefore the size of the plant; the location of the plant and its distance from
the feed stock supply; and where the gas is to be used. Starting a plant involves adding the right
microbes and allowing the population to be built up. Running a plant is a matter of feeding it regularly
and avoiding contaminants. (28 references).
http://dx.doi.org/10.3362/9781780448497.009
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