Strategic Action Plan - International Environmental Technology Centre

Strategic Action Plan Report
As the decomposition progresses, the organic biomass changes color to dark brown humus like substance
and its volume is reduced by 35 to 45%. Decomposition or stabilization is accomplished in 4 to 5 weeks.
The stabilized compost is heterogeneous in nature having impurities of various shapes, sizes and texture.
Hence mechanical process is required for screening out the digested organic matter in pure and powder
form. This is done with the help of mechanical and gravity separators as also with grading and sieving
machines. Inorganic and non-biodegradable material like plastic, metals, rubber, stones, bricks, etc. are
recovered for recycling/ reuse purpose. The other remnants about 15% of original volume which are nonrecyclable
are disposed off for sanitary or low lying landfills.
Fully matured and stabilized organic compost/manure is recovered. Quality control is done for chemical
nutrients and microbial counts. If required, it is enriched with nutrients and various microbes like
Azetobactor, Rhyzobium etc. The product is finally weighed and bagged.
Process Microbiology
During the aerobic composting process a succession of facultative and obligate aerobic microorganisms is
active. In the phases of the composting process, mesophilic bacteria are the most prevalent. After the
temperatures in the compost rise, thermophilic bacteria are predominating, leading to thermophilic fungi, which
appear after 5-10 days. In the final stages or in the curing period actinomycetes and molds appear. Because
significant concentration of these microorganisms may not be present in some types of biodegradable
waste e.g. newspaper, it may be necessary to add them to the composting material as an additive or
inoculums.
The microbiology of all aerobic composting process includes moisture content, C/N ratio and temperature.
For most biodegradable waste organic, once the moisture content is brought to a suitable level (50-60%) and
the mass aerated, microbial metabolism speeds up. The aerobic microorganisms, which utilize oxygen, feed
upon the organic matter and develop cell tissue for nitrogen, phosphorous and some of the carbon and
required nutrients. Much of the carbon serves as the source of energy for the organisms and is burned up and
respired of CO 2 . Because organic carbon serves both as a source of energy and cell carbon, more carbon is
required than nitrogen.
Conditions required for proper working of aerobic composting
1) Aeration
It is important to ensure that oxygen is supplied throughout the mass and aerobic activity is maintained.
During the decomposition, the oxygen gets depleted and has to be continuously replenished. This can be
achieved either by turning of windrows or by supplying compressed air.
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