From 1985 to 1993, a number of biogas plants were developed for treatment of various organic waste flows. A common feature of these plants is that produced biogas is used in a pneumatic / hydraulic system for stirring and control of the reactor. The bio gas pressure is converted into potential energy, released at regular time intervals. Put in a more matter-of-fact manner, this system could be compared to the heart beat of the reactor. The difference in the particular plants has mainly been one of peripheral equipment for instance for pre-treatment of added organic material, after treatment of degassed substrate, the kind of added organic material, control and monitoring, etc.
A plant of this type, in its most sublimed form, has been erected in Tanzania by SUPERFLEX in cooperation with Tanzanian Non Governmental Organization SURUDE. This plant has an effective reactor volume of appr. 4 m3, and has been built without any peripheral equipment, is uninsulated, and works without any supply of energy for control or heating. This plant is run solely using solar heat. For stirring of the substrate and reactor control, solely the biogas pressure level is used in a pneumatic/hydraulic system. Every five hours, the reactor will release its heart beat which may be experienced within one minute as a deep, rumbling sound mixed with a hissing from the gas, flowing at a rate of 100 km/h. through the gas pipe to the gas store.
As a new organism, the plant is, with its easy heart beat, day after day, week after week, year after year, a unit melting in with the grand nature of Tanzania. Plants of this kind contribute in various ways to the maintenance of ecological balance. Deforestation collecting wood and pollution of watercourses with organic waste are avoided. Degassed substrate from biogas plants is considered the most ideal form of agricultural soil fertilizer. Especially for plants in these areas, we would add that the daily heavy work in collecting wood frequently carried out over vast distances will discontinue, and the standard of hygiene will increase very considerably in that the night soil may be conducted to gas production, and in that animal waste will be carried away quickly, thus leading to a great reduction in the number of flies and a higher degree of cleanliness on site.
Plants of this type will, in a modified form, be perfect for treatment of a heavy flow of waste for instance from the processing industry for agricultural products, slaughterhouses, etc.
Jan Mallan, biogas engineer