Atmospheric Pollutants

Atmospheric Pollutants

1. Unburnt hydrocarbons

   • Caused by evaporative emissions and incomplete combustion
   • Contributes to the formation of photochemical smog, causing respiratory problems
   • Reduced by catalytic converters and Oxygenates- but this means that CO2 is increased

2. Carbon monoxide

   • Incomplete combustion of hydrocarbons
   • Toxic to humans, as it decreases the uptake of oxygen by the blood
   • Reduced by Catalytic convertors and oxygenates- but this means CO2 is increased. Also reduced by lean burn engines, but this may mean unburnt Hydrocarbons are increased

3. Carbon Dioxide

   • Complete combustion of hydrocarbons
   • Causes greenhouse effect and global warming
   • Hydrogen is the only petrol alternative that doesn't produced CO2

4. Nitrogen oxides

   • Nitrogen FROM THE AIR reacts with oxygen FROM THE AIR in the high temperature of the engine
   • Contributes to formation of photochemical smog, and causes acid rain
   • reduced by catalytic converters, but CO2 is increased. Also reduced in lean burn engines,but this may mean more unburnt hydrocarbons

5. Sulphur Oxides

   • Sulphur in petrol reacts with oxygen in air in the heat of the engine
   • Causes acid rain, with erodes limestone buildings and damages forests and lakes
   • Low sulphur fuel can be produced by DESULPHURISATION

6. Alternative fuels

   • Diesel
     • non- sustainable
     • Less CO produced
     • Produces more NOx
   • LPG or Autogas
     • Non sustainable, as crude oil is running out
     • Less CO, CO2, unburnt hydrocarbons and NOx than from petrol engines
     • Petrol engines are easily converted
     • But needs to be stored under pressure so that it's a liquid
   • Ethanol
     • possibly not sustainable- large amounts of energy needed for cultivating sugar cane for fermentation
     • Less CO, SO2, and NOx produced
     • higher octane number
     • Sugar cane absorbs CO2 in growth
     • Highly flammable
   • Biodiesel
     • can be made from waste plant & animal oils and fats, so its renewable, but fossil fuels may be used as an energy source in production
     • Living things absorbed CO2. it is biodegradable, so less CO, unburnt HC's SO2 and particulates than from diesel engine
     • NOx emissions higher than diesel engine
   • Hydrogen
     • Only sustainable if electricity needed for electrolysis of water is from a renewable source such as solar cells
     • Water is the only product of combustion, but H2 is highly flammable, & a high pressure in fuel tank is needed to store it as a liquid