Lesson 1  Lesson 2  Lesson 3  Lesson 4  Lesson 5  Lesson 6  Lesson 7  Lesson 8  Lesson 9  Lesson 10

Electrical Engineering and Technology |Электротехника и электротехнологии

LESSON 10

Read the text:           How are they produced?                                     

It is fairly common knowledge that the alcohols can be made from organic materials such as grains, fruit and wood. In practical and commercial terms the sources may be quite varied and sometimes surprising.

For example, waste from fields (used in food production) can be a useful source. The waste, traditionally, may have been burned but using the residue instead to create fuel gives a two-pronged environmental benefit. Firstly, the burning of the waste that would have fed dirt and toxic compounds into the atmosphere is obviated, and secondly, the use of the new byproduct as a renewable fuel means that less fossil fuel is consumed in vehicles.

 There is also a potential for the extraction of alcohols from domestic rubbish or trash. To some extent the advantages are as described above but additionally the amount of waste going in to landfill is reduced.

Sugar cane is a good example of a raw material which can be cultivated for the purpose of producing alcohol and therefore is different in principle from using already existing material. Other food crops such as corn and potato can be used to produce alcohols but none seem to have the potential of sugar cane. Dr Andre Faaij at the Utrecht University describes it as a 'Wonder Crop' (Ref: 'Sugar Rush', Engineering and Technology, Feb. 2007). Sugar cane has a very efficient cropping habit and the fibrous waste (bagasse) can be used to power the plant and evaporate the cane juice. This is a prime instance of industrial cogeneration or CHP. Where the cogeneration is efficient it is even possible to sell excess electricity to the the grid. The world's largest producer of ethanol from sugar cane is Brazil but other countries include India and Mauritius and there are more with considerable potential.

The main argument in favour of the process is that the growing of the crops absorbs carbon and so compensates for the eventual emissions. That argument has its doubters but certainly there can be little doubt that this is far preferable to the use of fossil materials.

The processes by which alcohols are produced are environmentally relevant. For example in the US, corn mash may be fermented to produce alcohol and the dried residue used for animal feed. In the States, the Environmental Protection Agency (EPA) argues that some of these production plants are releasing carbon monoxide, methanol and some carcinogens at unacceptable levels. Methanol is classified as a hazardous pollutant if it is allowed to contaminate the environment, and the emitted carcinogens include formaldehyde and acetic acid, released as volatile organic compounds (VOCs). It would appear that processes that are not properly controlled could create serious pollutions; so control is important.

There are clearly pros and cons in greenness when sourcing and producing alcohols. What we deduce is that if the sources are materials which are being cultivated or would normally be created anyway (eg waste from food production) there are substantial benefits to be gained. On the other hand if the raw materials are fossil extractions they will release sequestered carbon and that is as bad as it gets. Also we note there is a need for scientific monitoring and control of the production processes.If alcohols are used instead of petrol is there less tail-pipe pollution?

Here again we don't find an easy answer. Although cars can run on pure alcohol, road vehicles normally use a mixture of petrol and alcohol. The ratio of the mixture makes a difference to the pollution potential. In general when alcohol is added there appear to be less carbon monoxide and other toxins but there are greater emission of VOCs (see above): localized pollution is not only about carbon emissions.

On balance we do believe that the optimum mixture will be slightly greener at the point of exhaust.

 

1. Match the left part with the right:

 

The alcohols can be	a)     a mixture of petrol and alcohol.
Waste from fields can be	b)     a useful source.
Road vehicles normally use	c)     be made from organic materials.
Corn and potato can be used	d)     to produce alcohols.

 

2. Complete the sentences with the suggested words:

cons   cultivated   producing   there

There are clearly pros and (1)__________ in greenness when sourcing and (2)__________ alcohols. What we deduce is that if the sources are materials which are being (3)__________ or would normally be created anyway (eg waste from food production) (4)__________ are substantial benefits to be gained.