MCD Model (Modified Camartec Design)
A model adopted from Tanzania, also a fixed dome type mainly promoted in the Phase 1 of the program. Recommended by ABPP for the introduction of Biogas in Uganda. The CAMARTEC Solid State – domestic biogas plants have been designed and modified by TDBP from the popular MCD to allow use of fresh undiluted cattle dung as substrate/feeding material that will suit the potential group of livestock keepers living in dry or semi arid areas.
Major modifications that have been incorporated in SSD are:
- Its large cylindrical inlet opening of 80 centimeters diameter instead of the current 10 centimeters diameter PVC inlet pipe which will
allow a stiff organic material to enter into the digester. - A separate cylindrical dung mixing chamber with a conical bottom of 90 centimeter diameter where removal of unwanted materials or
debris takes place. - Increased digestion volume via its deeper inlet and outlet openings and the conical shaped bottom of the digester that compensates for
the lost volume due to expected siltation. - Placement of the expansion chambers manhole directly on top of the slurry outlet opening to facilitate removal of inorganic solids
Literally under normal operations such biogas plants require very little or no water for mixing with cattle dung, and can generate about 50%
more biogas due to the fact that what influences the amount of gas production is the quantity of total organic solid contents (TSC) in the
mixture.
The total solid content (TSC) of the fresh cattle dung normally varies between 15–19%. If dung is thoroughly mixed with an equal quantity of water, a case with our popular MCD will produce a mixture with TSC of between 8–10%, and the digested slurry discharged from these biogas units is watery, containing up to 94–96% of water and the Total Solid Content 4–6%.
The slurry is spread on to the ground or collected into open slurry pits for drying, over a period of up to 45 days, to facilitate its transportation to the fields for use as manure. Like for the popular MCD, initial feeding has to start with a mixing ratio of dung to water/urine 1:1, and once a plant has started producing gas, the ratio/consistency can now be changed gradually, i.e. from 1:1, 3:1, 4: 1 and lastly undiluted fresh dung only without varying the amount of
fresh dung to be fed into the digester provided that slurry will be able to flow by itself in and out of the system.
Testing will be conducted in several phases, basing on the convenient consistency of the influent to determine the amount of gas production/day as well as the optimum hydraulic retention time which is also likely to prolong from i.e. 50 days to 100 days.
