6. Large-scale biogas plants
Biogas technology, or better: anaerobic-process engineering, Is becoming increasingly important as
a means of treating and cleaning industrial organic waste materials and highly loaded organic
wastewater.
This applies in particular to the following ranges of production:
- large-scale stock farming
- industrial processing of agricultural produce (refining of sugar, production of starch, winning of
fibers, processing of coffee, generation of alcohol, slaughterhouses, etc.)
- industrial and urban refuse and sewage (manufacturing of paper, organic household waste,
sewage sludge, biotechnological industries).
Most biogas plants used in those areas are large-scale plant systems with volumes ranging from
several hundred to several thousand cubic meters.
Compared to aerobic treatment, anaerobic processes offer comparable performance with regard to
purification capacity and conversion rates, but also stand apart from the former in that they:
- require less energy to keep the process going and to generate useful energy in the form of
biogas, and
- produce less organic sludge, because the growth rate of anaerobic microorganisms is slower
than that of aerobic microorganisms.
Consequently, anaerobic treatment of waste materials and wastewater offer some major
advantages for a comparable initial invest" meet. Nonetheless, much of the technology has not yet
passed the testing stage.
Due to the size of plant, different objectives and special requirements concerning operation and
substrates, the anaerobic treatment of waste materials and wastewater involves a different set of
planning mechanisms, plant types and implementational factors. To go into detail on this subject
would surpass the intended scope of this manual; besides, extension officers hardly need expect to
be confronted with the job of planning such plants. Nevertheless, some basic information is offered
here to give the reader a general grasp of what large-scale biogas technology involves.
In discussing the various waste-treatment options, differentiation is made between wastewater
(organic - highly loaded) and waste materials/residues (organic solids).
Fig. 6.1: Basic principle of organic
wastewater treatment (Source:
OEKOTOP)
82