Biofuels
What you need to know
Reflections and Exam tips
Biofuels
Bio= Biological = Living
Fuel= Substance that can be burned to get energy
Biofuels come from living things or products from living things.
Why the interest in them then?
Because of the concerns that:
- Fossil fuels are gonna run out soon
- Fossil fuels cause pollution and global warming as they unlock CO2 that was locked away millions of years ago and put it back into circulation, significantly offsetting the Carbon balance.
Ethanol
Sugar cane (see image) is a grass with juicy stems that are filled with sugar (sucrose). Sucrose can be convereted to glucocse and glucose can be fermented to produce flammabe ethanol.
Ethanol can be used as a fuel as it:
- Burns (ignites) easily
- Is renewable- we can grow more of the cane next year and the year after, and the one after, so it :
- Does not offset the carbon balance, only returns the Carbon dioxide that the cane plant took from the air while it was photosynthesising.
The equation for the fermentation of sugar:
Glucose + Yeast (anaerobic respiration) —› Ethanol (Alcohol) + Carbon Dioxide
Ethanol is mixed with petrol to run petrol cars. The mixture of 20% Ethanol to 80% Petrol is called Blend. Diffrent countries use different percentages. Leading the trend in this revolution is Brazil, but at what cost?
- Sugar cane production may take up land for growing other food crops
- The demand for ethanol may result in destruction of rainforests to clear up land for sugar cane production.
What else?
- Car engines may need minor modifications
- Ethanol is very volatile, hence may need modified storage containers.
Biodiesel
Diesel is a thick, oily liquid. It is less volatile and not easy to ignite (set alight)
Biodiesel is just modified cooking oil. It can be obtained from plant seeds such as sunflower and oilseed rape
The advantages
- Fossil fuels are gonna run out soon
- Fossil fuels cause pollution and global warming as they unlock CO2 that was locked away millions of years ago and put it back into circulation, significantly offsetting the Carbon balance.
- It is renewable
The disadvantages
- Production may take up land for growing other food crops
- The demand may result in destruction of rainforests to clear up land
- Car engines may need minor modifications
Biogas
Biogas is methane from decomposing biological material. It is produced through anaerobic respiration of bacteria on dead organic matter in a closed container. The container is closed so as to prevent oxygen coming in, this would reduce methane production as aerobic respiration would occur.
The equation:
Organic matter (carbohydrates, fats) —› Methane + Carbon dioxide + Sulphur Dioxide
The more methane the better, the less Carbon dioxide and Sulphur Dioxide the better as they reduce the quality and flammability of the Biogas.
This depends on the material that is used. These include:
- Kitchen waste
- Human waste (faeces/poo)
- Animal waste (manure/poo)
- Vegetable waste
What are the ethical issues involved in using human faeces to produce biogas for cooking?
What process occurs during fermentation?
What conditions would affect biogas production in your local area?