What do biofuels use?
Energy that is trapped in biomass.
What types of biofuels are there?
- Burning the wood of fast-growing trees
- Sugar or waste material is fermented by bacteria or waste and is used as fuel
Why are biofuels becoming more popular?
- Alternative sources to fossil fuels
- Waste makes no net increase to greenhouse gases (being burnt as the same rate biofuels are produced)
- Don’t release particulates when burnt
What are problems of clearing land for biofuels?
- Fuel is not carbon neutral because other plants can’t remove carbon dioxide
- Important habitats may be lost and species could go extinct
What does biogas contain?
- Mainly methane
- Some carbon dioxide
- Small amounts of hydrogen, hydrogen sulphide and nitrogen
How can biogas be produced?
- In a digester
- Uses continuous flow method as organic waste is constantly added and the gas and remaining solids are being constantly removed
What is biogas used for?
- Burnt to produce electricity
- Burnt to produce hot water and steam for heating systems
- Used as fuel for vehicles
What is the ideal methane % in biogas?
Above 50% it can be burnt in a controlled way but below 10% it becomes extremely explosive.
What is an advantage and disadvantage of biogas?
Cleaner fuel than diesel and petrol but doesn’t contain as much energy as natural gas.
What is gasohol?
Biogas mixed with alcohol from fermentation, used in countries such as Brazil for petrol.
Why is gasohol good for countries like Brazil?
- Uses sugar cane rather than oil
- Cheaper than importing oil
