Low-Cost Polyethylene Tube Digester

From energypedia


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.


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






Very high >20 years

High; drum is weakness

Medium; Depending on chosen liner




Self agitated by Biogas pressure

Manual steering

Not possible; plug flow type

Evtl Manual steering


6 to 124 m³ digester vol

Up to 20 m³

Combination possible

Up to 6 m³ digester vol

Methane emission





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 ).

Picture td2: Winding In-/Outlet Tube Digester
Low Cost Polyethylene Tube Digester Scheme.jpg
Figure td1: Scheme of Low-cost Polyethylene Tube Digester.
One of the 6" PVC drainpipes serves as inlet and the other one as the outlet of the slurry. In the tube digester finally, a hydraulic level is set up by itself, so that as much quantity of added prime matter (the mix of dung and water) as quantity of fertilizer leave by the outlet.
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).

►Go to Top

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).

Picture td4: Gas Storage Reservoir
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.

Fig. 2: Industrial plant with utilization of domestic organic wastes

►Go to Top

Installation Manual for Low Cost Polyethylene Biogas Digester

Low cost polyethylene tube installation.pdf

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

►Go to Top

Further Information


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.