|
Biogas Design Types
A description of the main types of biogas plants up to and including biogas production
Biogas design, or in other words, the design of biogas production plants comes in many guises. Here is a list of
some of the most common types of biogas plant designs which have been conceived and built, and some of them in
large numbers, numbering in the tens of thousands:-
1. Household sewer and soil biogas plant designs (developing nations): Low cost, low maintenance gravity fed
concrete tanks below ground close to the dwelling with a lead off pipe from the top of the digester vessel which
provides biogas to the kitchen where it fuels a hob.
2. On-farm biogas design which is simple and automated, but restricted to the developed nations and an order of
magnitude more high-tech than the household plant just described. These may use purpose grown biofuel crops, or
they may use animal slurry. They do have basic automation and usually run as a continuous process.
3. Sewage treatment biogas plant designs. The truth is that these in the past were probably designed first and
foremost as a method of taking sewage sludge and rendering it pathogen free an safe for use as a fertiliser and
soil conditioner for farmland and nurseries. These are quite large plants but until recently they would supply no
more than the power to run the sewage works and maybe some would use the biogas directly to run site owner’s
vehicles.
4. A biogas design option emerging in the last 10 years has been that of the community biogas plant, providing both
a convenient waste disposal route for organic wastes ad a source of income to farmers and residents alike within
the community. Such plants will accept a wide range of feed materials from food waste from local residents to farm
animal waste slurries, and where food processing takes place probably also food waste processing waste.
5. All the foregoing options are water based so called “wet” digestion processes, but anaerobic digestion can be
carried out on solids, with the exclusion of air. Mixing is more difficult and many examples of this technique
therefore operate on a batch rather than a continuous production basis. Rather than a tank a batch type dry
digester comprises a tunnel filled and emptied by a wheeled front end loader or similar.
6. Many further options have been developed for larger digester plant designs and plants using municipal solid
waste (MSW), and specialist technology provider companies have patented many of these. They first is where the
biogas designer adds pre-processing variations on the feed materials to ensure the best percentage of organic
matter is digested while in the reactor. The most common is to reduce the particle size for quicker digestion.
Another pre-digestion stage method is to add hydrolysis which again improves the conversion rate of biomass into
biogas.
7. At the digestion stage again a major choice is single or double digestion stages, and some technology providers
will strongly advocate the value of a double digestion stage biogas design.
Many more biogas design options also exist once the biogas has been produced, but there is no space to mention
those here.
by Steve Last - 8 January 2009
Back to
Top
###
Source: http://www.biogas-digester.com
| 
