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The
process of composting is a technique in which the natural process
every organic substance undergoes through the action of microbes
is controlled, accelerated and improved.
It is an "aerobic process of biological decomposition of organic
substances which occurs under controlled conditions, allowing us
to obtain a biologically stable product in which the organic component
presents a high degree of evolution" (Keener et al., 1993).
Rich in humus, in active microbial flora and in micro-elements,
compost is suitable for many agricultural uses, from greenhouse
plants to open field cultivation.
The
composting process takes place essentially in two phases:
- Bio-oxidization,
in which the mass is cleansed: this is the active phase (known
as the high rate, active composting time), characterised by intensive
processes of degradation of the organic components which can be
broken down more easily
- The
maturing process, during which the product becomes stable and
enriched with humic molecules. This is known as the curing phase,
and is characterised by processes of transformation of the organic
substance, the maximum expression of which is the formation of
humic substances.
The
composting process can be carried out with selected organic waste
(for example organic waste collected separately from general household
waste, or organic waste collected from agri-business), from which
is produced "High quality compost", a composted soil improver
for use in agriculture or floriculture.
The organic fraction obtained from non-separated solid waste is
treated by means of a mechanical-biological system of composting
to obtain a Stabilised Organic Fraction for non-agricultural use,
for example landscaping and land reclamation such as filling in
old quarries, or for daily covering of landfill sites.
COMPOSTING
OF PRE-SELECTED ORGANIC WASTE
In
recent years the recovery of selected organic waste for the production
of High Quality Compost has increased significantly. In 1993 there
were 10 composting plants in Italy, dealing with approximately 100,000
tonnes of waste per annum, whereas in 2002, (the latest APAT-ONR
statistics available), this had increased to 237 composting plants
treating approximately 2.8 million tonnes of separately collected
organic waste a year, with an operating capacity of 5 million tonnes
per annum.
These composting plants are concentrated in northern and central
Italy, where systems of separate organic waste collection of household
waste are more advanced, and where the regional authorities have
activated plans and publicity to favour this process.
Today, Italy is the second European country with the highest number
of composting plants, even if several countries such as Austria,
Holland, Denmark and the Flanders part of Belgium have a larger
pro-capita operating capacity.
Source:
APAT-ONR, 2003 Waste Report
BIOLOGICAL
TREATMENT OF NON-SEPARATED SOLID WASTE
Biological
treatment is carried out on the organic fraction of solid waste
which is not collected separately, but obtained from the mechanical
sorting of solid waste after it is collected.
This mechanical-biological treatment, in all its phases, (stabilisation
before landfill, biological drying, production of stabilised fractions
for landscaping), is an important part of the waste management system
at European level. With the imminent application of legislation
on landfills (Decree 99/31) which provides for the progressive reduction
of the percentage of organic substances present in the waste destined
for landfill sites, a further increase in the number of composting
facilities and the total treatment capacity is forecast.
According to data collected in 2003 by APAT-ONR (relating to 2002),
there were 90 treatment plants operating in Italy, which treated
approximately 5.6 million tonnes of urban waste, while the total
capacity was approx. 10 million tonnes.
Source:
APAT-ONR, 2003 Waste Report
It
is noticeable that the majority of the plants are situated in northern
and central Italy, but the geographical distribution is more equal
than for plants which treat selected organic waste.
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