Revision as of 11:54, 19 September 2016 by
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Overview
There are different types of small scale biogas digesters. Some of the biogas digesters are summarized below:
The table below gives a first comparision of the different types.
| Factors
|
Fixed dome
|
Floating drum
|
Tubular design
|
Plastic containers
|
| Gas storage
|
Internal Gas storage up to 20 m³ (large)
|
Internal Gas storage drum size (small)
|
Internal eventually external plastic bags
|
Internal Gas storage drum sizes (small)
|
| Gas pressure
|
Between 60 and 120 mbar
|
Upto 20 mbar
|
Low, around 2 mbar
|
Low around 2mbar
|
| Skills of contractor
|
High; masonry, plumbing
|
High; masonry, plumbing, welding
|
Medium; plumbing
|
Low; plumbing
|
| Availability of Material
|
yes
|
yes
|
yes
|
yes
|
| Durability
|
Very high >20 years
|
High; drum is weakness
|
Medium; Depending on chosen liner
|
Medium
|
| Agitation
|
Self agitated by Biogas pressure
|
Manual steering
|
Not possible; plug flow type
|
Evtl Manual steering
|
| Sizing
|
6 to 124 m³ digester vol
|
Up to 20 m³
|
Combination possible
|
Up to 6 m³ digester vol
|
| Methane emission
|
High
|
Medium
|
Low
|
Medium
|
Low-Cost Polyethylene Tube Digester
In the case of the Low-Cost Polyethylene Tube Digester model which is applied in Bolivia (Peru, Ecuador, Colombia, Centro America and Mexico), the tubular polyethylene film (two coats of 300 microns) is bended at each end around a 6 inch PVC drainpipe and is wound with rubber strap of recycled tire-tubes. With this system a hermetic isolated tank is obtained (figure td1 ).
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Picture td2: Winding In-/Outlet Tube Digester |
 Figure td1: Scheme of Low-cost Polyethylene Tube Digester.
Because the tubular polyethylene is flexible, it is necessary to construct a "cradle" which will accommodate the reaction tank, so that a trench is excavated (picture td3).
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Gasholder and Gas Storage Reservoir
The capacity of the gasholder corresponds to 1/4 of the total capacity of the reaction tube (figure td1). To overcome the problem of low gas flow rates, two 200 microns tubular polyethylene reservoirs are installed close to the kitchen, which gives a 1,3 m³ additional gas storage (picture td4).
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Picture td4: Gas Storage Reservoir |
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Picture td3: Tube Digester Altiplan of Bolivia |
To contrast these simple biogas plants, figure 2 gives an impression about dimensions of industrial plants which are, for example, built in Europe.
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Fig. 2: Industrial plant with utilization of domestic organic wastes
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Installation Manual for Low Cost Polyethylene Biogas Digester
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Experience with Polythylene Biogas Digester (PBD)
To read about the experiences of deploying Polyethylene biogas digester, please see the article on
Variation Tyre Tube Household Digester
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Further Information
References
This article is a continuation of the article, Types of Biogas Digesters and Plants. For questions regarding the article, please contact the authors of the article, Types of Biogas Digesters and Plants.
