10-Using resources

• life cycle assessments (LCA)

  analyse the different stages in a product's life cycle to assess it's impact on the environment
• the four stages of an LCA

  1. extracting and processing raw materials
  2. manufacturing and packaging the product
  3. using the product
  4. disposing of the product
• LCA - extracting and processing raw materials

  • when extracting resources from nature it damages the environment directly - cutting trees, digging huge mines for ores
  • when processing resources it damages the environment indirectly due to huge amounts of energy required and pollutants being released - extracting metals from their ores, fractional distillation
• LCA - manufacturing and packaging

  • energy use
  • release of pollution
  • production of waste products
• LCA - using the product

  • how much damage it does during it's lifetime
  • how long the product is used for
• LCA - disposing the product

  • placing it in landfill - takes up space that could be used for nature, chemicals can seep out into the ecosystem
  • burning - release pollutants
  • energy to transport the waste needs to be considered
• limitations to life cycle assessments

  • it's difficult to gather all the required data about each step
  • it's difficult to compare different harms
  • companies can manipulate their LCAs to look more favourable
• potable water is water that is safe to drink and is not pure
• potable water can be acquired through:

  • treating fresh water sources
  • desalinating sea water
• 3 points for water to be considered potable

  • levels of dissolved substances must be fairly low
  • pH must be between 6.5 - 8.5
  • it must not have any microorganisms
• fresh water sources

  • surface water - lakes, rivers, reservoirs
  • ground water - aquifers
  • fresh water is replaced frequently and is easy to access
• treating fresh water

  1. pass water through a wire mesh to filter out large objects
  2. pass water through a bed of sand and gravel to filter out smaller objects
  3. sterilize the water to kill microorganisms - bubble chlorine gas through it, expose the water to ozone or ultraviolet light
• desalinating sea water

  • distillation - simple distillation in larger quantities
  • reverse osmosis - water is passed through a membrane to allow only the water particles through
  • these processes require a lot of energy so are very expensive and damage the environment
• waste water sources

  • domestic - household waste from showers, sinks or toilets
  • agricultural - nutrient runoff from fields, animal waste from farms
  • industrial - factories that make and use chemicals
  • waste water must be treated before disposal to minimise pollution
• sewage(domestic) and agricultural waste must have organic matter and harmful microbes removed, industrial waste must go through extra steps due to the harmful chemicals
• sewage treatment

  1. screening - pass the sewage through a mesh to remove any objects
  2. sedimentation - sewage is left in settlement tank, the heavier particles settle at the bottom as sludge, the lighter particles settle at the top as effluent
  3. aerobic digestion - air is pumped through the effluent to supply the bacteria with oxygen
  4. anaerobic digestion - sludge is sealed in a container to prevent air entering, which ensures anaerobic respiration
• sewage treatment aerobic and anaerobic digestion

  • aerobic and anaerobic digestion is used on sewage to break down organic matter by microorganisms
  • effluent water is safe and can be released after aerobic digestion
  • sludge releases methane during anaerobic digestion which can be burned as an energy source, the remaining digested waste can be used as a fertiliser
• industrial waste water treatment

  • can contain toxic substances
  • removed by - adding chemicals to precipitate out any metals or using ultraviolet radiation to break them down