C7 - Making Ethanol

Different ways to make ethanol and if it is sustainable or not

Ethanol by distilation

How can ethanol be made by distillation? What are the steps?

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Ethanol by distilation

1) Ethanol solution is placed in flask below fractioning column

2) Solution is heated so that ethanol boils.  The ethanol vapours travel up the column cooling as they go.

3)The temperature is such that anything above the boiling point of ethanol (like water) cools to a liquid and flows back into the solution at the bottom

4) This means that only pure ethanol vapours reach the top of the column

5) The ethanol vapour flows through the condeser - where its cooled to a liquid, and then collected. 

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Sustainable process?

Is fermentation a sustainable process?

Answer the eight questions for sustainability.

Will the raw materials run out?

What is the atom economy like?

What do I do with the waste products?

What are the energy costs?

Will it damage the environment?

What are the health and safety risks?

Are there any benefits or risks for society?

Is it profitable?

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Sustainable process?

Will the raw materials run out? Sugar beet and yeast grow quickly so wont run out.

What is the atom economy like? The waste Co2 produced means it has a low atom economy.  And because the enzyme is killed of by the ethanol produced, it makes the reaction even less efficient

What do I do with the waste products? Waste CO2 can be released without processing

What are the energy costs? Energy is needed to keep reaction at optimum temp.

Will it damage the environment? CO2 adds to global warming

What are the health and safety risks? Chemicals produced don't have any specific dangers

Are there any benefits or risks for society? Making ethanol doesn't impact society 

Is it profitable? Depends on what the ethanol is used for

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Biomass

How can ethanol be made from biomass?

What are the optimum temperatures for this?

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Biomass

1) Waste biomass is the parts of a plant that would normally be thrown away - e.g. rice husks and straw

2) Waste biomass cannot be fermented in the normal way because it contains a lot of cellulose.  Yeast can easily convert some sugars to ethanol but it cannot convert cellulose to ethanol. 

E.coli bacteria can be genetailly modified so they can convert celluslose in waster biomass to ethanol.  

Optimum conditions for this are at 35 degrees Celsius and a slightly acidic solution, pH 6.

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Sustainable biomass?

Is producing ethanol from biomass sustainable? 

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Sustainable biomass?

Very similar to the sustainability of standard fermentation because they both use similar processes.  Advantage of using biomass is that you don't have to grow crops specially for producing ethanol, you can use the waste from other crops. 

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Steam production

How do you make ethanol from steam and ethene?

What are optimum temperatures for this?

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Steam production

1) Ethane is one of the hydrocarbons found in crude oil

2) It is cracked (split) to form ethene (C2H4) and hydrogen gas.

3) Ethene will react with steam (H20) to make ethanol 

Temp of 300 degrees Celsius and a pressure of 70 atmosphere.  Phosphoric acid is used as a catalyst. 

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Steam Sustainability

Will the raw materials run out?

What is the atom economy like?

What do I do with the waste products?

What are the energy costs?

Will it damage the environment?

What are the health and safety risks?

Are there any benefits or risks for society?

Is it profitable?

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Will the raw materials run out? Crude oil is the raw material and it is non-renewable so will run out

What is the atom economy like? Cracking ethane has a fairly high atom economy as the only was product is hydrogen.  Reacting ethene has an even higher atom economy as ethanol is the only product.

What do I do with the waste products? Hydrogen is only waste product by cracking ethane.  It can be reused to make ammonia in the Haber process

What are the energy costs? Energy is needed to maintain high temperatures and pressure used.

Will it damage the environment? Do not produce any waste products that will directly harm environment.  But crude oil can harm environment, through oil spills

What are the health and safety risks? High temp and pressure need to be carefully controlled otherwise it could be very dangerous

Are there any benefits or risks for society? No specific impact on society

Is it profitable? Yes, continuous and quick and the raw materials are fairly cheap, but it wont stay that way once crude oil starts to run out. 

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Comments

Rhys B-M

Really good summary of ethanol!

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