Waste-derived fuels
To achieve greater sustainability, it is essential that all
available resources are used efficiently and effectively. The
cement industry considers wastes, with some exceptions, to be
alternative resources to use within its manufacturing
processes.
The UK Government has committed itself to the EU Landfill
Directive and other international agreements that aim to reduce
disposal of wastes to landfill and to recovering energy and
materials from used tyres, packaging wastes, solvents and many
other waste streams. The UK cement industry is, therefore, playing
a vital role in helping to achieve the UK's environmental
objectives by utilising appropriate wastes as alternative fuels and
raw materials in the manufacture of cement, via industrial
ecology.
Which wastes are used as alternative fuels?
In the UK, alternative fuels are carefully specified and
sourced from amongst: used tyres (whole or chipped), secondary
liquid fuels (recycled inks, solvents, thinners, oils and
residues), packaging wastes (non-recyclable paper, cardboard and
plastics), and, to a limited extent, sewage sludge (pellets). A
very small residue or ash is formed from lthose fuels,
but this is chemically bound in cement clinker. In
particular, tyres burn to give a residue that is mainly iron, thus
reducing the need for additional iron ore to be added as a raw
material component.
The heavy metal content of cement is continually monitored to
ensure it is always below levels that may cause concern. Any
organic compounds will not survive the high temperature found in
the cement kilns.