mining waste

• Metal ore waste:

  • Acid mine drainage 
  • Unwanted waste left in piles 
  • Waste comes into contact with water and oxygen 
  • Sulphide minerals form 
  • Pyrite oxidation 
  • Sulphuric acid 
  • Dissolves heavy metals 
  • Water runoff contains toxic heavy metals 
• Metal ore waste:

  • Remove water from mine and treat 
  • Flood mine then seal, after microorganisms have used oxygen no more oxidation of minerals 
• Metal ore waste:

  • Active treatment - neutralise with a base like lime 
  • Expensive - constant use of base and disposal 
  • Effective with high flowrates 
  • Passive treatment - wetland ecosystem with ponds of limestone gravel
  • Expensive to set up but cheap to run 
  • Effective for low flow rates and in remote areas 
• Metal ore waste:

  • Bad chemicals during processing 
  • Waste from crushing is fine and toxic with radioactive or toxic metals 
• Coal mining waste:

  • Waste tipped onto spoil heaps 
  • Shale and mudstones 
  • Only stable at gentle angles 
• Aberfan:

  • Spoil heap on sandstone slope 
  • Shale with coal under sandstone aquifer 
  • Spoil heap on top of a spring 
  • Heap on site of a previous landslide 
• Cleaning up coal:

  • Carbon capture from power stations could store CO2 underground 
  • In porous reservoirs from depleted oil and gas 
  • CO2 could be pushed into deep coal that cannot be mined - displacing methane that could be used 
  • Store in salt deposits 
  • Store in basalt - CO2 reacts slowly to make a non-toxic mineral