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compost tunnel. This way the compost mix is gradually ‘pushed’ towards the
exit of the composting tunnel. (Morocomp.,2010)
The residence time of the compost mix inside the tunnel is 46 days. Each
agitation device is equipped with sprinklers for providing water to the compost
mix. This is important in order to ensure that the compost mix will not dry out
from the high temperatures that develop inside the compost heap. This way the
moisture level of the mix is controlled <strong>and</strong> maintained at desirable levels.
Thirty six (36) blowers provide the required air for the composting process to
take place. This corresponds to 12 blowers for each feeding line of the
composting unit. Aeration is achieved (apart from agitation) with air suction
from the floor of the compost tunnels. The tunnel floor has a grid; air is sucked
through aeration pipes placed beneath the grid <strong>and</strong> ends up in a main pipe. In
total there are six (6) main pipes; the air that is sucked is fed to each central
pipe through eight (8) tunnels. Therefore, 2 main pipes correspond to each
feeding line of the composting unit.
At the floor of each tunnel there is a collection pipe in order to collect the
produced leachate. The top part of the collection pipe is perforated so that
leachate can enter inside it. All the collection pipes converge to a centralized
pipe which ends up at the wastewater treatment unit of the facility. At the end
of each composting tunnel there is a conveyor belt which has been installed
vertically to the composting tunnels. This conveyor belt transports the end
compost to the screening unit. At last, there is a Shredder for shedding the
green waste (Morocomp.,2010)
The refinery unit
The compost from the tunnels is fed to the refinery unit (Picture 59.) through
the conveyor belt of the composting tunnels. The compost is received at the
reception unit. In the reception unit the compost is agitated <strong>and</strong> grinded.
Agitated screws with blades speed up the simultaneous feeding, distribution
<strong>and</strong> dosing of the material. Two rotating drum screens are utilized that produce
three different streams of output material. The finest material is directed
through a conveyor belt to the waste residuals. The coarser material, which is
mainly comprised of material that has not been fully composted, is directed to
a densimetric table. The middle sized stream is directed to another densimetric
table. The screening unit has in total three (3) densimetric tables.