Fermentation- when bacteria or yeast break down sugars by anaerobic respiration.
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How is Ethanol made?
Anaerobic Fermentation of Sugar
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How does Yeast make Ethanol?
Break down of glucose by anaerobic respiration. Glucose --> Ethanol + Carbon Dioxide + Energy
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How can sugar cane juices be used?
Can be derived from maize starch by the action of carbohydrase. (or glucose)
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Why is Ethanol distilled?
Seperate it from the yeast and remaining glucose before use.
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How is Biogas made?
Anaerobic Fermentation of Waste Materials.
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What does Biogas usually contain?
70% Methane and 30% Carbon Dioxide.
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What is Biogas made in?
A simple fermenter called a digester or a generator.
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Why do Biogas generators need to be kept at a constant temperature?
Keep microorganisms respiring.
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Why does Biogas have to be used straight away?
As it can't be stored as a liquid as it needs too high a pressure.
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What are by-products used for?
Fertilizing crops and gardens.
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What are batch generators?
Make biogas in small batches. Manually loaded with waste, which is left to digest and by-products are cleared away.
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What are continuous generators?
Make biogas all the time. Waste is continually fed in and biogas is produced at a steady rate. More suited to large-scale biogas projects.
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What does a Biogas generator need?
1. An inlet for waste material to be put in. 2. An outlet for digested material to be removed through. 3. An outlet so that Biogas can be piped to where it is needed.
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Which generator is more expensive?
Continous generator - as waste has to be mechanically pumped in and digested material has to be mechanically removed all the time.
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Which generator is less convenient?
Batch Generators- have to be continually loaded, emptied and cleaned.
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What are the conditions the Biogas generator has to be kept at?
Around 35°C- if the temperature falls production will be slower.
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Where should generators be located?
Away from homes as they smell also best located close to a waste source.
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How are Biofuels 'greener'?
They are carbon neutral.
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What is good about Biogas generators?
1. Cheap and easily available. 2. Act as waste disposal system getting rid of waste that could cause disease and pollution.
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