capacity greater
control of the optimum composting procedures, accelerated
composting procedures greater odour control and increased
efficiency.
The composting facility is organised so that
the incoming green waste can move directly to the weighbridge
and into the reception area. Once the waste has moved into
the reception area the waste is sorted and shredded. The waste
is irrigated to bring the moisture levels up to the optimal
levels before the green waste enters the clamp. The green
waste is mixed to maintain a good C:N ratio and the correct
physical structure. Once the feedstock preparation is done
the green waste is loaded into the clamp. During the period
that the feedstock is being prepared there is a mist-air deodoriser
that removes any odour from the reception area.
The Composting System was installed by the Composting Company
Ltd. The invessel composting system installed at Tree
Fella consists of four clamps. The clamps are made
from concrete ‘A’ blocks that are bolted into
the concrete base for stability.
Each clamp has a series of galvanised steel
pipes that run along the base of the clamp. The piping is
attached to a fan at the rear of the back wall, the fan forces
the air through the green compost in the clamps to ensure
that there is sufficient oxygen in the green waste mix to
maintain aerobic decomposition. This forced aeration system
allows us to maintain the optimal oxygen levels
so that the correct microorganisms can break down the green
waste.
The clamps have a retractable roof that covers the entire
clamp; the roof retracts fully allowing the loading shovels
to enter the clamp when loading. Once the clamp is fully loaded
six temperatures probes are inserted into the green waste
so that temperature fluctuations can be monitored and adjusted
accordingly. The temperature probes are linked to data loggers
that continuously record the temperature levels within the
clamp to confirm that the compost has been sanitised. There
are also two oxygen probes that are inserted into each clamp.
This allows us to measure the oxygen levels in the clamp so
that aerobic decomposition is maintained throughout.
The fan and piping system is set up in such
a way that the humid air between the green waste and the retractable
roof is sucked from underneath the roof and back down into
the fan and air pipes along the base of the clamp. This helps
to reduce moisture loss from the green waste.
When the initial composting phase has been completed the door
to each clamp is removed using a loading shovel. The partially
composted green waste is then removed from
the clamp and formed into a windrow. The composting material
when removed from the clamp has no bad odours because it has
been fully aerated throughout the period it has been in the
clamp. It is this beginning stage that is crucial in maintaining
the oxygen levels to reduce any odour so that when it is moved
into open windrow the odours have been reduced.
The open-air windrow system is then continued
through the phases of stabilisation and maturation.
Regular turning and monitoring is maintained throughout the
composting process until the compost is sufficiently matured
for use.
Some of the advantages of using the invessel system are; that
the composting process is speeded up; the
potential throughput for the same footprint has been vastly
increased and site overall efficiency improved; reduced odour
through a combination of forced aeration and mist air system;
a better monitoring system in the use of a temperature probes,
oxygen probes and data loggers.
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