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Electrical Engineering and Technology |Электротехника и электротехнологии

LESSON 7

Read the text: Bio-diesel, a Renewable Alternative to Petro-dieseL for Motor Vehicles

As its name suggests biodiesel is a fuel oil derived from biological sources. Mainly these are vegetable oils and recycled cooking greases or oils, and it is a viable alternative to traditional petro-diesel for fuelling diesel engines. It has other uses, for example in heating boilers, but our main concern is its use in cars and other motor vehicles. As a motor fuel, it may be used 100% pure (in compatible engines) or combined with petro-diesel in proportions as low as 2%. Although on combustion it releases greenhouse gases (mainly, but not only, CO2) it is described as carbon-neutral, since it is derived indirectly from living plant sources. It is argued that the plants absorb essentially the same amount of these gases during the growing stage and this is in stark contrast to fossil-based fuels. The benefits of biodiesel exceed its carbon-neutral property and some of the other advantages are identified below. Biodiesel can also be manufactured from animal oils and greases for which the arguments are different. However, if these oils and greases are normally discarded then taking them out of the waste stream and converting them to a fuel has obvious, substantial environmental benefits. First let's briefly see how it is manufactured then identify some limitations before identifying its main advantages

How is it manufactured, its byproducts and what does it cost?

Put simply, vegetable and/or animal oils, fats or greases are combined with methanol in the presence of sodium or potassium hydroxide (as a catalyst). The chemical reaction is called transesterification, and the products are fatty acid methyl esters (the biodiesel) plus glycerine. The latter is an alcohol with many useful properties for example it is sweet, a lubricant and a humectant which means it retains moisture. These properties give rise to many commercial applications in commodities such as drugs, paints, personal-care products, foods, flexible plastics etc. Popular raw sources for biodiesel processing include rapeseed oil (Europe), soybean oil (USA), palm oil (SE Asia). Various cooking oils and fats are suitable (new and recovered). Some keen individuals make their own biodiesel, especially in the States, and there are sites describing the methods, but the chemicals produce toxic fumes and the liquids are corrosive (eg caustic soda) so great care is needed. It is possible for individuals to buy small and medium sized purpose-made plant for production. Reading some articles on the net we see examples where experimenters are pouring neat untreated oils into their wagons and claiming to get away without processing, however, there are serious drawbacks to such a method which can result in expensive damage to the engine. The cost of manufacturing biodiesel currently is greater than petro-diesel although with the volatility of conventional oil prices we are not giving a figure. Even so, at the point of sale the difference may be negligible due to the imposition of tax. In the UK, for example, where taxes are high and biodiesel gets some preference (Ref: UK Budget, 2002, duty 20p/litre less) the prices of commercially produced diesels are similar. If the biodiesel is home produced it can be significantly cheaper in the tank.

1. Match the left part with the right:

2. Complete the sentences with the suggested words:

 conventional   due   giving   greater

The cost of manufacturing biodiesel currently is (1)____________ than petro-diesel although with the volatility of (2)____________ oil prices we are not (3)____________ a figure. Even so, at the point of sale the difference may be negligible (4)____________ to the imposition of tax.