Fuels from Microorganisms

Fuels from Microorganisms

Fuels can be made by fermentation of natural products - often waste products

Fermentation - when bacteria or yeast break down sugar by anaerobic respiration

Ethanol:

• Yeast make ethanol when they break down glucose by anaerobic respiration
• Glucose -----> ethanol + carbon dioxide + energy
• Sugar cane juices can be used, or glucose can be derived from maize starch by carbohydrase enzymes
• Ethanol distilled to seperate from yeast and remaining glucose before use
• In some countries cars are adapted to run on a mixture of petrol and ethanol called gasohol

Biogas:

• Biogas is usually about 70% methane and 30% carbon dioxide
• Lots of different microorganisms are used to produce biogas, they ferment plant and animal waste which contains carbohydrates
• Sludge waste from e.g. sewage works or sugar factories is used to make biogas on a large scale
• It's made in a simple fermenter called a digester or a generator
• Biogas generators need to be kept at a constant temperature to keep the microorganisms respiring
• There are 2 types of biogas generators - batch generators and continuous generators
• Biogas can't be stored as a liquid (it needs to high pressure) so it has to be used straight away, for heating, cooking, lighting or to power a turbine to generate electricity

Fuel production can happen on a large scale or a small scale:

Large scale biogas generators are now being set up in a number of countries, in some countries small biogas generators are used to make enough gas…