The PBD is a cost effective system for the digestion of manure from 1 - 2 livestock
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
- 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
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
- 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
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.