In-Vessel Composter
IVC is used primarily for the treatment of biodegradable waste such as food and garden waste. Specially designed vessels (partially or fully enclosed) contain the waste and treat it under strictly controlled environmental conditions regulating moisture, temperature and aeration levels.
This composting process allows the decomposition of the material to form a “humus” or compost, which can be used in landscaping, agricultural and horticultural applications. The waste volume is also significantly reduced. There are many variations on the system, however the process described in the following section relates to a local IVC which Perth and Kinross Council utilises for biodegradable garden and food waste collected from the New Kerbside Recycling Service.
The IVC consists of insulated silos, which are suspended above a concrete base and contain the biodegradable waste. A series of 8 - 28 silos are built close together with gaps through which air can pass into the silo. Each bank of silos have a front end loader, mixer and overhead feeder allowing shredded and mixed material to be loaded into the silos. The waste is mixed with wood shavings or manure-rich waste to ensure an optimum feedstock is prepared before loading to allow efficient composting.
The composting process is started by micro-organisms, predominantly bacteria, which allow the initial decomposition to begin. Fungi and bacteria then further degrade the waste material, by producing enzymes, breaking the material down. Temperature, moisture, pH and aeration all have to be controlled to allow optimum composting to occur.
The composting process is complete after a period of around 8-21 days, depending on the feedstock. The silos are unloaded from the bottom by means of an auger and conveyors. The compost can then be heaped in a maturation shed, after which it may be used in bulk, or sent for bagging after being graded, for use by gardeners. The process can occur all year around regardless of the outside weather conditions.
To find out more about In-Vessel Composting please visit the Waste Technologies page at
www.wasteawarescotland.org.uk/html/aboutWasteTech.asp
