Landfill waste site
prevent it from contracting and mixing with ground
and surface water.
To ensure that waste deposited in a landfill
site is more rapidly degraded it can be pulverized
before landfilling. The process is usually carried
out under wet conditions to reduce dust and, since
the waste needs to be wet to promote maximum
production of landfill gas, biodegradation occurs
quickly after the waste has been landfilled.
In parallel with the land filling of household
waste, since many of its constituents are
combustible, incineration is another option. Its
attraction lies in the fact that large land areas are
not removed from use for other purposes for an
indefinite period of time, and surplus heat can be
produced. Because household waste contains a
large variety of materials, including those which
are not combustible, plant used to incinerate such
waste needs to be rugged and versatile to cope
with a highly variable feedstock both in terms of
waste composition and calorific value.
Because the waste is not easy to feed to and
through an incinerator it is usual practice to use
furnaces based on either the chain or rocking
grate principle or to a lesser extent a rotary kiln. To
ensure high combustion efficiency the temperature
range at which the furnace is operated and burns
waste and the time during which the waste reaches
and is maintained at furnace temperature and
turbulence within the furnace chamber, all need to
be strictly controlled, the so-called “3Ts Principle” –
Temperature, Time and Turbulence exemplifies this
requirement for good combustion.
Waste delivered to an incinerator by a
collection vehicle usually discharges its load into
a large hopper from where the waste can the