using resources

finite resources

being used up faster than they can be replaced

• fossil fuels

• metal ores

• minerals

renewable resources

• these can be replaced at the same rate theyre used

sustainability

• meeting the needs of the present without compromising the ability of future generations to meet their own needs

the synthetic shift

• Natural resources are often replaced by synthetic ones for human needs

potable water

water thats safe to drink

its not pure water

it contains dissolved salts and microbes

how to make potable water

• choose a source = fresh rain water from river or lake.

• water passed through filter beds = remove different sized insoluble solids

• water then sterilised by ozone/ UV light/ chlorine = kill microbes

if only salty/ sea water available?

• requires desalination

• done by distillation

• or by reverse osmosis = passing water through a membrane at high pressure to filter out salts

• Both very expensive = requires lots of energy

water treatment (before it goes to the environment)

• passed thru a mesh screen to remove large objects

• Chemicals added to make solids and microbes stick together to form sediment.

• Heavier sludge = sinks to bottom. Lighter effluent = floats on top

• anaerobic digestion of sewage sludge

• aerobic digestion of the effluent

• water then sterilised with chlorine to kill any microbes left

pros and cons of sea water

• pro = its a plentiful raw material

• cons = very expensive and takes lots of energy

pros and cons of fresh water

• pros = very cheap and easy to make potable

• cons = not every country has rivers/lakes

4 stages of Life Cycle Assessment

• extracting and processing raw materials

• Manufacturing and packaging

• Use and operation during its lifetime

• Disposal including transport

problems with LCA

• not purely objective

• It’s a subjective judgement

• Leads to bias

why do we need to reduce use

• conserve limited resources = we’re running out of certain materials and fossil fuels

• save energy = extracting and processing raw materials requires huge amount of energy

• reduce environmental impact = they cause landscape scarring, habitat destruction and pollution

how to reduce use

Reuse recycle reduce

How can you reduce the use of energy when extracting copper?

• Use scrap iron to displace copper from solutions (like the ones produced in bioleaching)

• Because iron is cheaper and more reactive than copper

Pros and cons of recycling

• pros = saves energy, protects habitats reduces landfill, waste conserves ore

• cons = collecting and transporting waste requires fuel. sorting different types of waste can be difficult and expensive

metals recycling

• by melting and casting into new shapes

• uses much less energy than mining and smelting new ore

glass reusing

• crushed and melted to make new glass products

building materials reusing

• bricks can be reused

• concrete can be crushed to make road base

phytomining

Using plants to extract metal from low-grade ores

• plants are grown on soil containing low-grade copper ore

• The plant absorbed the metal ions and stored them in their roots and leaves

• The plants are harvested and burned

• The resulting ash contains a high concentration of copper compounds

bioleaching

Using bacteria to extract low-grade ores

• Specific bacteria are mixed with low-grade ore

• the bacteria carry out chemical reactions and produce a solution called a leachate

• The leachate contains metal compounds, not solid metal yet

Plastic bag

• Material = crude oil (finite)

• Manufacturing = high energy releases carbon dioxide

• Reusable many times

• Recyclable but stays in landfill for hundred of years

paper bag

• material = wood/timber (renewable)

• Manufacturing = high water use produces waste

• Only used once or twice usually

• Biodegradable and non-toxic