Polyethylene Biogas Digester (PBD)


			Introduction
			Puxin Biogas Digester
			Polythene Biogas Digester
			Oil Drum Digester

		TakaNguvu 3 is an implementation of the Polyethylene Biogas Digester (PBD) described by Lylian Rodriguez and T R Preston in Recycling Livestock Wastes - Biodigester Installation.

Project Rationale

Small-scale farmers at the Kenyan Coast mainly use fuel wood for cooking. With the increase in population over the last years this results in increasing and rapid deforestation, causing direct severe environmental problems such as increased soil erosion, loss of soil fertility, loss of water in catchments areas and even loss of biodiversity. Furthermore this energy source (e.g. wood) is almost exhausted. It is therefore essential that other means of fuel sources for communities and small-scale farmers have to be found (e.g. for cooking and lighting).

Alternative system to the drum digesters for renewable energy-resource on small and medium scale farms and other sources of bio-waste.
Promote and develop a low cost biogas system for small scale farmers with up to 10 livestock units
System easy to handle while in use
System imbedded in the environment of organic sustainable farming methods
Farmer training in Biogas-production

On 24. December 2004 the PDB was filled and went into production of biogas.

Location
Shamba Mtopanga Bamburi North Quarry, Mombasa, Kenya Hosted by

Experience

The PBD is a cost effective system for the digestion of manure from 1 - 2 livestock units upwards.
It is built within a short time. However the design of the grave and the handling of the plastic tube needs extra care.

This digester type has many advantages compared to the oil drum digesters:

The PBD can be directly connected to the animal shed in order to capture the maximum of manure, urine and water and to reduce the handling.
The capacity can be built according to the available manure. 5 m of PBD with a diameter of 67 cm can be operated with 1 cow.
The gas yield is higher as the retention period is longer.
In a 24-hour period the average gas volume produced was 275 litres (0.275 m³).
With this amount of gas a low pressure cooker could be operated for about 1 hour.
Lifespan of the digester is much longer: 2 - 4 years (experience from other sites) compared to 1 year of the oil drum type (our own experience)
Cheaper to build: For the same amount of produced gas at least 3 oil drum digesters would be needed
The biofertilizer can directly be brought to the fields as the concentration is much thinner (more water) compared to the one from the oil drum digester.

The oil-drum digester however is a good supplement for demonstration purposes as it is possible to look inside the digester and to see what is going on and that there are no hidden gadgets / miracles.

Project Support / Credits

This project has been kindly supported by The National Centres of Competence in Research (NCCR) North-South, Switzerland.

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last update: 20/09/2011