6. Environmental Impact
and Economics of Metal Ore Extraction and
mining–quarrying other minerals
Aspects of this discussion applies to
minimising the cost of production of any chemical product.
What are the social, economic and
environmental impacts of exploiting metal ores (mineral extraction), of
using metals and of recycling metals – economic,
sociological and environmental issues
Metal ores are obtained
by mining/quarrying and that this involved digging up and processing
large amounts of rock.
Most ores are mined have
to be concentrated before the metal is extracted and purified.
This means that metal or mineral extraction
results in problems and issues in balancing ecological,
environmental, economic, social advantage factors.
It doesn't matter whether you are mining and
processing iron ore or limestone, many of the advantages and
disadvantages are common to these operations.
advantages of exploiting it's own mineral resources:
Useful products can
be made from metal to enhance our lives – most consumer products
we take for granted ie we expect to have them at our disposal.
revenue if the mineral or its products are exported.
people, especially new sources of employment in poor countries or areas of high
unemployment in developed countries.
go into the local/national economy leading to improvements in
schools, health service and transport etc.
issues related to
limestone quarrying, a detailed focussed discussion on
extracting a particular mineral.
local facilities promoted e.g. transport
systems, like roads, recreational and health social
disadvantages of exploitation of mineral resources and
reduction of its social and environmental impact:
mining–quarrying or processing can be reduced by air filter and
precipitation systems and even hosing water on dusty areas or
spoil heaps or carried away to somewhere else via tall chimneys.
Scarring of the
landscape from mining, quarrying, waste tips etc. as well as
loss of wildlife habitat.
process operation or transport of raw materials and products
can be reduced by cleaning the 'waste' or 'used' air, water and
waste gases etc. of
toxic or acidic materials e.g.
monoxide from the blast furnace extraction of iron, it can
be burnt as a fuel, but it must not be released into the air
unless converted to biologically harmless carbon dioxide.
dioxide gas from copper extraction of its sulphide ore is an
irritating poisonous gas which can also cause acid rain, but
it can be converted to the useful, therefore saleable,
industrial chemical concentrated sulphuric acid, so you can
remove a harmful pollutant and recover back some of the
metal extraction costs, good green economics?
like sulphur dioxide can be removed by bubbling through an
alkali solution such as calcium hydroxide solution
('limewater') where it is neutralised and oxidised to
harmless calcium sulphate. Cleaning a gas in this way is
called 'gas scrubbing'.
operations will disfigure the landscape BUT it can be re–claimed
and 'landscaped' in an attempt to restore the original flora and
Disused quarries and
mines increase hazards in the landscape e.g. quarries can fill
with water, old mine workings can collapse buckling roads
through subsidence and producing sink holes.
issues related to
limestone quarrying, a detailed focussed discussion on
extracting a particular mineral.
The cost of
extracting and purifying metals is quite varied for several reasons.
If the ore
is plentiful it is cheaper e.g. iron ore, but silver ores and
gold are much rarer and on that basis alone they would be a more
ores using coke (e.g. iron), made from cheap coal, is cheaper
than the electricity bill for extracting aluminium from its
molten oxide by electrolysis, but different metals have
different properties best suited for particular and different
speaking, more reactive metals (like Al) are more costly to
extract than less reactive metals (like Fe) because of the
different energy demands and ease of extraction, which may
sometimes be due to more costly technology.
RECYCLING – a very
good idea because mineral resources are limited and manufacturing
costs of many metals from their naturally occurring ores involves
costly energy and environmental issues.
material to obtain metals from to recycle
Before any metals can be
recycled the scrap metal must be collected, transported and sorted,
which are cost factors themselves.
The main problem is
separating the useful metal from the rest of the rubbish.
e.g. in domestic
recycling plants iron and steel objects can be plucked out with a
magnet, since most other materials are not magnetic.
The recycling process
Why recycle metals?
Reasons to recycle metals
Saves valuable finite
natural mineral resources, only a finite quantity of metal ores,
conserves a valuable mineral reserve - mineral sources cannot last forever!
Saves energy, so less
fossil fuels burned, good 'green' economics. Its cheaper to recycle
metals that to start from scratch with raw unprocessed mineral ore.
There will be less pollution and less waste.
Reduces a waste disposal
problem e.g. less piles of rusting cars and reduces environmental
problems in general.
Any reduction in
landfill waste sites is a blessing on the environment, so this is
now a real drive to recycle metals, plastics, glass and paper.
Landfill rubbish sites are source of environmental pollutions from
toxic materials leaching out and a health hazard from rotting
decomposing organic material.
Apart from reducing the
accumulation of waste, there are waste disposal management issues
e.g. how do store the waste? how dangerous is it? and environmental
scientists/technicians are needed to monitor possible pollution of
the surrounding air, water or land – more costs!
It is less expensive
than mining the original ore and extracting the metal, both these
processes are eliminated and far less energy is used overall, so on
several counts it will cost less money i.e. much more economic.
supply of copper–rich ores is limited so it is important to
recycle as much copper as possible especially as demand for
copper is growing as the economies of African countries, India,
China and Brazil etc. are rapidly developing and becoming
increasingly industrialised with the ensuing consumer demands for
all the eg electrical products that we in the West take for granted.
Recycling copper only
uses ~15% of the energy that is required to extract and purify
copper from its naturally occurring ore.
For every tonne of
aluminium recycled you would need to mine at least four times as
much bauxite ore and all the transport and extraction costs
You only need about 10% of the energy of extracting
aluminium from its ore compared to recycling previously extracted
aluminium and there is far less waste.
Its quite easy to melt the scrap
aluminium and re-cast in any desired shape - same applies to scrap
iron and steel.
The future of metal
extraction from mineral ores?
There are still huge
deposits of mineral ores around the world which are and will be for
some time fully exploited by the industrialised nations – soon most
of the world?
ores e.g. copper ores, are being depleted and because traditional mining and
extraction methods have major environmental impacts, there are
important issues involved and to be resolved in the future
exploitation of metal ore reserves.
Because of these issues,
new ways of extracting metals like copper from low–grade ores are
being researched hopefully to limit the environmental impact of
For an example of an alternative
method of extracting metals see ...
Recycling cast iron or steel alloy
scrap is a good example of some of the points discussed above, they can
both be melted into freshly made iron or steel.
About 42% of iron or steel in
manufactured goods is recycled iron/steel,
whether it be steel pans, car bodies, bridge girders, stainless steel
This makes good economics
because recycling saves on several costs including energy and transport AND allows a mineral resource
like iron's haematite or magnetite ore resources to last a lot longer – slower depletion of
the Earth's mineral ore resources will make it last longer.
So, scrap metal merchants
are doing a roaring trade at the moment.
The savings are partly
reduced by the cost off collecting waste/scrap metal.
There are particular
problems due to the varying composition of alloys, but if the
composition is known, or obtained from chemical analysis, the different
compositions can be blended together to a desired alloy composition.
- Recycling aluminium
- About 39% of the aluminium in foil, car
components etc. is recycled aluminium.
- This makes good economics because
recycling saves on costs AND allows a mineral resource like aluminium's
bauxite ore to last a lot longer – slower depletion of the Earth's
mineral ore resources will make it last longer.
- Transport costs may be less (ie within
UK now), but much more
- mining costs are omitted – energy/machinery
involved in digging out the ore, crushing it, transporting the ore,
- and the cost of actually extracting
the metal from its finite ore resource – electrolysis plant,
expensive electrical energy used
- So, scrap metal merchants are doing a
roaring trade at the moment.
- The savings are partly reduced by the
cost off collecting waste/scrap metal and purifying for further use.
- It is estimated that recycling aluminium
only uses 5% of the energy required to extracted the same mass of
aluminium from its ore – the original aluminium extraction uses very
expensive electrical energy for the electrolysis.
SEE ALSO three
related-overlapping sections on the chemical and pharmaceutical
pharmaceutical Industry, economics & sustainability, finite
resources, Life Cycle
Products of the
Chemical & Pharmaceutical Industries & impact on us
The Principles & Practice of Chemical
Production - Synthesising Molecules
% purity of a product * 14.2a
% reaction yield * 14.2b
The haze of pollution from Redcar Steelworks on the
North Sea coast of North East England. It is an important source of
employment and income into towns like Redcar. This steel works closed in 2010 and in an area already hard hit by the decline of
traditional heavy industry over the last fourty years but I'm glad to
say the steelworks reopened in 2012 providing much needed jobs for the
Teesside area BUT has since closed permanently in 2016!
A mineral train of limestone
or lime filled wagons from Swinden Quarry in the Yorkshire Dales. The
local stone walls, barns and houses are also made of limestone – a
useful naturally occurring resource.
issues related to limestone
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