4.10 Using resources

What do humans use Earth’s resources for?

To provide

• Warmth

• Shelter

• Food

• Transport

What can natural resources provide?

Natural resources, supplemented by agriculture provide

• Food

• Timber

• Clothing

• Fuels

Define sustainable development

Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs

When natural supplies are limited or expensive, what do we do?

Natural supplies are supplemented or replaced by agricultural or synthetic products as they tend to be cheaper and more widely available

Give examples of natural products that are supplemented or replaced by agricultural and synthetic products

• Wood used for construction, furniture

  • Synthetic plastics

• Natural rubber

  • Synthetic rubber made from petrochemicals

• Wool, cotton

  • Synthetic fibres such as polyester

• Natural dyes

  • Replaced by synthetic dyes produced from chemical processes

Define potable water

Potable water is water that is safe to drink

• For humans, drinking water should have sufficiently low levels of dissolved salts and microbes

True or false: potable water is pure

FALSE: Potable water is not pure in the chemical sense because it contains dissolved substances

What do the methods used to produce potable water depend on?

• Available supplies of water

• Local conditions

Define freshwater

Freshwater is water that has low levels of dissolved substances

Describe how potable water is produced in the UK

In the UK, rain provides water with low levels of dissolved substances (freshwater) that collects in the ground and in lakes and rivers

• Choose an appropriate source of freshwater

• Pass the water through filter beds

  • The water is passed through a wire mesh screen that catches large objects such as leaves and twigs

  • The water is then passed through filters made of sand and gravel, which removes any remaining particles of mud or grit

• Sterilising

  • The water is sterilised to kill any harmful bacteria or microbes:

    • Add small amounts of chlorine

    • Bubbling ozone through

    • Exposing water to ultravoilet radiation, which destroys microorganisms by damaging their DNA

Name the sterilising agents used for potable water

• Chlorine

• Ozone

• Ultraviolet light

If supplies of freshwater are limited (eg. due to the country being dry), how can potable water be produced?

• Desalination of salty water/ sea water

Describe how potable water is produced from seawater

Through desalination:

• Distillation

  • Pour the salty water into distillation apparatus

  • Heat the water so that it evaporates, leaving any dissolved salts behind

  • The water vapour will condense in the condenser and can be collected as it runs out

• Reverse osmosis

  • Water is forced through a partially permeable membrane

  • High pressure is applied to the salty water

  • The membrane only allows water molecules through; so ions and larger molecules are trapped by the membrane and so are separated from the water

  • Desalinated water is produced on one side, while waste water remains on the other

These processes require large amounts of energy

What is the downside of producing potable water from sea water?

Desalination processes require large amounts of energy

What does sewage and agriculture waste water require?

Removal of:

• Organic matter

• Harmful microbes

Otherwise this would cause pollution and health risks

What does industrial waste water require?

Removal of

• Organic matter

• Harmful chemicals

Describe the process of sewage treatment

• Sewage is screened by passing through a mesh which removes solids and pieces of grit

• The sewage is allowed to stand in a settlement tank and undergoes sedimentation (the heavier, suspended solids sink to the bottom to produce sewage sludge, while the lighter effluent floats on top

• The sludge is removed and transferred into large tanks; it gets broken down by bacteria in the process of anaerobic digestion

  • Anaerobic digestion breaks down the organic matter in the sewage sludge, releasing methane in the process

  • The methane gas can be used as an energy source, and the remaining digested waste can be used as fertiliser

• The effluent in the settlement tank is removed and treated by biological aerobic digestion

  • Air is bubbled through the water to encourage aerobic bacteria to break down any organic molecules and harmful microorganisms

  • After this, the liquid effluent can be safely discharged into nearby rivers or the sea

Comment on the relative ease of obtaining potable water from waste water, groundwater and salt water

• Waste water

  • Requires more processes

  • Uses much less energy than desalination

• Groundwater

  • Easiest method: contains only few microorganisms and levels of dissolved salts so needs only simple filtration and sterilisation as groundwater has been naturally filtered by rocks

• Salt water

  • Most difficult: desalination methods require large amounts of energy and specialist equipment which is very expensive

What ores are becoming scarce?

Copper ores

Name one way to improve the sustainability of copper

• Extracting it from low grade ores

Describe how copper is extracted from low grade ores

• Phytomining

  • Plants are grown in soil that contains copper

  • They absorb the metal compounds; as plants cannot use or get rid of the copper, it builds up in the leaves

  • The plants are then harvested and burned to produce ash that contains copper compounds

• Bioleaching

  • Bacteria are added to the ore

  • The bacteria carry out chemical reactions to produce a leachate, containing copper ions.

Both of these processes produce copper compounds, and so the copper must be extracted:

• Copper can be obtained from solutions of copper compounds by displacement using scrap iron

• Electrolysis