Advantages of Biofuels
Biogas better for environment than fossil fuels because sustainable and relatively clean fuel - releases fewer pollutants when burnt than coal and oil.
Biofuels produced in sustainable way, decomposed crops to make biogas can be replaced quickly with new plants. Finite supply of fossil fuels like coal and crude oil - will run out.
Plants grown to make biogas photosynthesise so removes CO2 (greenhouse gas) from atmosphere. Balances out release of CO2 when burnt - increasesd greenhouse gas levels cause global warming. Only true if biofuels burnt at same rate as new biomass produced, areas of land cleared to grow biomass without burning other vegetation, burnt vegetation releases CO2.
Biogas cleaner fuel than diesel or petrol, burning fossil fuels produce particulates causing lung disease. Burnt biogas produces no particulates.
Disadvantages of Biofuels
Biogas not as much energy as same volume of natural gas because more dilute.
Large areas of land cleared of vegetation for space to produce biofuels. Increases greenhouse gas levels and huge problems for ecosystems:
- Habitat loss - plants cleared so habitats of plant and animal species destroyed
- Species extinction - loss of habitats and change in food availability means species die out in area
Ethanol as a Biofuel
Can be burnt as fuel, cleaner than petrol or diesel produces fewer pollutants.
Renewable resources, produced by yeast fermenting glucose. Sugar cane, corn, barley used as source of glucose.
Cars can be adapted to run on mixture of ethanol and petrol - gasohol. 10% ethanol, 90% petrol.
Using gasohol saves on crude oil - non-renewable.
Growth of crops means CO2 absorbed. Balances out CO2 produced when gasohol burnt.
Brazil has made extensive use of gasohol, most economically viable in areas with plenty of sugar cane (tropical countries) and not much oil.