Reducing Emissions
- To reduce the amount of pollutants released in car exhaust fumes, many cars are now fitted with catalytic converters
- Precious metals (such as platinum, rhodium and palladium) are coated on a honeycomb to provide a large surface area
- The reactions that take place in the catalytic converter include:
- Oxidation of unburnt hydrocarbons:
CnH2n+2 + (3n+1)[O] → nCO2 + (n+1)H2O
-
- Oxidation of CO to CO2:
2CO + O2 → 2CO2
or
2CO + 2NO → 2CO2 + N2
Catalytic removal of NOx and CO
- Carbon monoxide and the nitrogen oxides released through cars’ exhaust fumes pollute the atmosphere
- The nitrogen oxides are reduced on the surface of the hot catalyst to form the unreactive and harmless nitrogen gas which is then released from the vehicle’s exhaust pipe into the atmosphere
- The chemical reaction for the reduction of nitrogen oxide to nitrogen gas by the catalyst is as follows:
2CO (g) + 2NO (g) → 2CO2 (g) + N2 (g)
A catalytic converter helps reduce the pollutants from motor vehicles
Alternative fuels
- There are a number of reasons for finding and developing alternative fuels:
- Reducing pollution from the combustion of fossil fuels, including issues associated with global warming and climate change
- The limited amount and depletion of non-renewable fossil fuels are two reasons for finding alternative fuels
- Biofuels are renewable fuels
- Renewable meaning that they can be replaced over a short period of time
- The bio part of biofuel meaning that it comes from living matter
- The three main biofuels are biodiesel, bioethanol and biogas
- Biodiesel - made by refining renewable fats and oils
- Bioethanol - made by fermentation
- Biogas - made / released when organic waste breaks down
Benefits of biofuels
- Biofuels are often considered as carbon neutral
- Biodiesel and biogas can reduce the amount of waste going to landfill as the waste can be used to produce them
- Biofuel production could provide money for less developed countries as they have the space to grow the crops required
Drawbacks of biofuels
- The cost of converting engines and machinery to run on biofuels instead of petrol / diesel
- Many developed countries don't have the space to be able to produce enough plants to make the biofuels because the land is needed for food production
Greenhouse Gases
- When shortwave radiation from the sun strikes the Earth’s surface it is absorbed and re-emitted from the surface of the Earth as infrared radiation
- Much of the radiation, however, is trapped inside the Earth’s atmosphere by greenhouse gases which can absorb and store the energy
- Carbon dioxide, methane and water vapour are gases that have this effect
- Increasing levels of carbon dioxide, although present in only a small amount, is causing significant upset to the Earth’s natural conditions by trapping extra heat energy
- This process is called the enhanced greenhouse effect