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

• This page concentrates on metal resources, but many aspects discussed e.g. recycling, equally apply to the use of plastics.

• 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 often results in lots of waste material that must be dealt with from an environment of view.

• 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.

• Examples of advantages of a country 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.

  • Valuable revenue if the mineral or its products are exported.

  • Jobs for people, especially new sources of employment in poor countries or areas of high unemployment in developed countries.

  • Wages earned go into the local/national economy leading to improvements in schools, health service and transport etc.

  • See issues related to limestone quarrying, a detailed focussed discussion on extracting a particular mineral.

  • Increase in local facilities promoted e.g. transport systems, like roads, recreational and health social facilities.

• Examples of disadvantages of exploitation of mineral resources and reduction of its social and environmental impact:

  • Dust from 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.

  • Noise from process operation or transport of raw materials and products (lorries/trucks/wagons).

    • Difficult to deal with, sound–proofing often not practical, but operations can be reduced for unsociable hours e.g. evening movement.

  • Pollution can be reduced by cleaning the 'waste' or 'used' air, water and waste gases etc. of toxic or acidic materials e.g.

    • Toxic carbon 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.

    • Sulphur 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?

    • Acidic gases 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'.

  • Mining operations will disfigure the landscape BUT it can be re–claimed and 'landscaped' in an attempt to restore the original flora and fauna.

    • However in the case of a limestone quarry, I'm afraid there is no way round the fact that huge chunks of beautiful hills get carted away if we want to use it as useful mineral.

  • 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.

  • See 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 valuable commodity.

  • Reduction of 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 uses.

  • Generally 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.

  • Recycling is all about reusing materials like metals or plastics to make new useful products.

    • It creates new jobs, replacing some of those associated with large scale mining.

  • Collection of 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

    • e.g. scrap iron is added to newly extracted from a blast furnace being converted into steel.

  • 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!

    • Recycling is now a massive industry and creates new jobs.

      • Waste material needs to be collected and transported to specialised recycling centres.

      • A modern recycling centre is a very sophisticated operation separating all sorts of domestic or industrial waste from mobile phones to plastic bags and aluminium or steel products.

    • 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.

    • Environmental benefits.

      • 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!

    • Saves money - 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.

      • Recycling is particularly beneficial if the metal is expensive to extract and buy - more so for rare metals.

    • Overview of benefits:

      • Many of these benefits described are economic benefits

        • e.g. less waste to manage - less environmental damage to repair in the future,

        • new jobs - more wealth circulating in society and people paying tax,

        • less energy used - greener more sustainable technology (including biotechnology) - especially if the metal production processes are costly and use lots of energy - reduces carbon footprint - les use of fossil fuels.

  • Examples: The 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 involved.

      • 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?

  • However metal–rich 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 traditional mining.

  • For an example of an alternative method of extracting metals see ...

    • ...  copper extracted by phytomining or by bioleaching ... for more detailed notes on exploiting low grade ores or waste from spoil heaps that may contain economically viable amounts of metal.

• Recycling iron and steel

  • 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 cutlery etc.

  • 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.

    • Transport costs may be less (e.g. within UK now, whereas the iron ore is imported from abroad), but also and  importantly

      • mining iron ore costs are omitted – energy/machinery involved in digging out the ore, crushing it, transporting the ore,

      • and the cost of actually extracting the iron from its finite ore resource – chemicals needed (coke from coal and limestone), constructing and running a blast furnace

  • 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
  • Apparently aluminium is the most cost effective metal to recycle.
  • 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 importantly
    • 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 there is less impact on the environment - less ore mined and less waste, also less transport used and much less energy involved overall.
  • 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.

Recycling other materials

Paper

Paper and cardboard are easily collected and reprocessed for further use in packaging or writing/printing paper.

Glass

Glass bottles can be recycled, cleaned and reused directly.

Other glass products are easily collected and melted down and reshaped as recycled glass products - the waste glass can be sorted by colour and chemical composition.

The recycled glass might end up as a jar, bottle or fibreglass insulation.

Initial glass production uses lots of energy, but recycling only need energy to melt the glass - much more energy is used in extracting sand and limestone and converting them to glass.

Plastics

See section 7I on recycling plastics on polymers page

Recycling is not without its problems

Recycling itself, also uses energy and other resources to collect the waste materials, sort them and remove impurities e.g. food, grease or paint contaminants.

You also need energy to reprocess the material e.g. metal, plastic or glass into useable material or object.

Some materials are difficult to separate economically, requiring time, machinery-technology and energy e.g. glass of different colours, different steels - but its easy to separate non-magnetic aluminium from magnetic iron or steel (referred to as 'ferrous' metals).

There is always a cost to recycling, it might be too expensive, especially if there is not enough of a specific waste material to recycle in bulk or there is insufficient demand for the recycled product.

So, there are times when you have to weigh up the cost of recycling versus environmental impact i.e. which do you do, recycle or dispose of the waste material and produce new material from freshly extracted raw materials.

Therefore, ideally, choose the option with the smallest impact on the environment - requires the least energy, least resources, reducing material put into landfill sites and is are the raw materials/energy renewable or non-renewable.

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SEE ALSO three related-overlapping sections on the chemical and pharmaceutical industries

Chemical & pharmaceutical Industry, economics & sustainability, finite resources, Life Cycle Assessment, recycling

Products of the Chemical & Pharmaceutical Industries & impact on us

The Principles & Practice of Chemical Production - Synthesising Molecules

Aspects involving calculations ...

... % purity of a product  *  14.2a % reaction yield  *  14.2b atom economy

Now closed unfortunately!

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 forty 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, Northern England.

The local stone walls, barns and houses are also made of limestone – a useful naturally occurring resource.

See issues related to limestone quarrying

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WHERE NEXT?

Other associated KS4 Science GCSE/IGCSE chemistry web pages on this site

• GCSE/IGCSE Foundation–tier (easier) Multiple choice QUIZ on METAL EXTRACTION

• or GCSE/IGCSE Higher–tier (harder) Multiple choice QUIZ on METAL EXTRACTION

• and gap–word–fill exercise on METAL EXTRACTION

• Reactivity of metals : all the reactions of metals with oxygen (air), water and acids, displacement reactions

• Oxidation–reduction explained (redox theory)

• Group 1 Alkali Metals: chemical and physical properties

• Extra Industrial chemistry : properties and uses of metals including titanium and aluminium

• Transition metals physical and chemical properties and uses

• Metallic Bonding – structure and properties of metals

• Extra Electrochemistry–electrolysis theory, experiment designs and links to all electrolysis sections

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