______keen individuals make their ____biodiesel, especially ____the States, and ____are sites describing the methods, ___the chemicals produce toxic fumes and the liquids are corrosive (eg caustic soda) __great care is needed. It is possible ___individuals to buy small and medium sized purpose-made plant for production.
Exercise 2. Fill in the table with words and expressions from the text:
| substances | devices | commodities | |
| Example: On combustion biodiesel releases | greenhouse gases (mainly CO2). | - | - |
| Biodiesel is used in | |||
| Biodiesel can be manufactured from | |||
| Glycerine has commercial applications in |
Exercise 3. Compose a story on one of the topics (up to 100 words):
“The Ways of Manufacturing Biodiesel”
“Advantages vs Disadvantages of Using Biodiesel”
LESSON 8
THE READING MODULE
Read the text: (continued)
There are some limitations to its green credentials.
The carbon-neutral feature of biodiesel can be reduced to some extent because fossil fuels may be used in general transportation and in the manufacturing process. That is a variable depending on the detailed procedures but in any case should not be as much as a third.
Where specialised crops are grown on a vast commercial scale there is a distinct threat to diversity, natural forestation and the provision of foods.
Frequently biodiesel is combined with petro-diesel to ensure greater compatibility with unmodified engines. When used in standard compression-ignition engines biodiesel can increase nitrogen oxide emissions. This phenomenon is not due to nitrogen in the fuel but comes from the intake air as a result of the particular combustion process. This phenomenon is not replicated in some other applications such as oil fired boilers and the effect can be reduced in vehicle engines by refining the tuning. Now let's review some of the additional benefits of biodiesel.
Biodiesel produces less noxious emissions than petro-diesel.
Biodiesel reduces tailpipe particulate matter, hydrocarbon, and carbon monoxide emissions from most modern four-stroke compression ignition engines. The reason is mainly associated with the presence of oxygen in the fuel which allows more complete combustion. Particulates are mainly carbon dust, commonly described as soot, and contain very fine particles that can be dangerous since they can get into the lungs by bypassing the body's natural filter mechanisms. Together with the unburned hydrocarbons, particulates are suspected of being carcinogens and can cause other serious toxic effects. Carbon monoxide is well known for its lethal action in the bloodstream. Obviously, the higher the proportion of biodiesel in a mixture, the more these noxious exhausts are reduced. Biodiesel has a very low concentration of sulphur, which can lead to SO2 and acidic precipitation. The amount is very much less than traditional diesel oils.
And there are other fringe benefits of biodiesel.
The overarching benefit of biodiesel is that as a renewable fuel it is nominally carbon-neutral. An associated factor is that the global petroleum resources are being depleted rapidly and the term renewable is more significant than just reducing emissions. Biodiesel improves the lubricating power of the fuel and therefore ensures correct operation of key components in the engine system.
The fuel can be used in existing diesel engines especially at low proportions. Some modifications may be necessary, especially at higher concentrations of bio, and vehicle purchasers should be aware of engine specifications. The modifications are usually only minor and do not represent a basic change in the technology.
The fact that one possible raw material is used cooking oils etc gives a special advantage. Large caterers (think McDonald's) will have residues contaminated with meat. To be able to use this product for biodiesel is an opportunity to be welcomed, the only downside being that the contaminated materials would need to be filtered and 'washed' first.
But some disadvantages too.
Biodiesel has a lower energy density than petro-diesel and because it is a denser fuel, the statistics vary slightly depending on whether you want a figure of energy per gallon or per pound. Roughly speaking the reductions are in the vicinity of 10%. Viscosity at low temperatures is important with diesel, sometimes making cold-weather starting difficult; biodiesel can be at a disadvantage in this respect. We have read of occasional use of dual tank vehicles where petro-diesel is used to start and shut down but switched to biodiesel for main running. A more practical solution is to introduce some special additive or a proportion of petro-diesel.
The properties of biodiesel mean that rubber pipes may have to be replaced by plastic ones and it may remove engine deposits hence filters may need changing more frequently.
If biodiesel-from-crops was widely adopted as a motor fuel then there would be a knock-on effect with serious problems caused by reduced biodiversity, displaced forests and the disrupted supply of other vital agricultural products. There is no reasonable expectation that petro-diesel could be completely replaced by bio-diesel. There are already signs that over development of crops for bio fuels can be damaging to the environment.
After text activity
I. Reading exercises:
Exercise 1. Read and memorize using a dictionary:
| natural forestation, provision of foods, compression-ignition engines, nitrogen oxide, intake air, tailpipe particulate matter, four-stroke compression ignition engines, hydrocarbon, soot, exhausts, sulphur, acidic precipitation, fringe benefits,raw material, residues, contaminated materials, energy density, viscosity, additive, engine deposits |
Exercise 2. Answer the questions:
1) What are the major limitations of using biodiesel?
2) What are the advantages of using biodiesel?
3) What are the disadvantages of diodiesel?
4) Is overdevelopment of crops for bio fuels damaging to the environment?
Exercise 3. Match the left part with the right:
| 1. Using biodiesel in standard compression-ignition engines can | a) in existing diesel engines. |
| 2. The unburned hydrocarbons and particulates can | b) increase nitrogen oxide emissions. |
| 3. Biodiesel can be used | c) for biodiesel. |
| 4. Residues contaminated with meat can be used | d) cause serious toxic effects. |
THE SPEAKING MODULE
II. Speaking exercises:
Exercise 1. Describe nitrogen oxide, hydrocarbon, exhaust, residue, energy density, additive using the suggested words and expressionsas in example:
| nitrogen oxide N2O, colorless, sweet-tasting, gas, boiling, -90°C; slightly, soluble, water, soluble, alcohol; used food, aerosol, anesthetic, dentistry, surgery, known, laughing, gas Example: N2O Colorless, sweet-tasting gas, boiling at -90°C; slightly soluble in water, soluble in alcohol; used as a food aerosol, and as an anesthetic in dentistry and surgery.Also known as laughing gas. |
| hydrocarbon one, very, large, group, chemical, compounds, composed, only, carbon, hydrogen; largest, source, hydrocarbons, petroleum, crude, oil |
| exhaust working, substance, discharge, engine, cylinder, turbine, performing, work, moving, parts, machine |
residue
|
| energy density energy, per, unit, volume, medium; case, electric, magnetic, field, energy, needed, set up, field, thought, residing, field |
| additive substance, added, another, strengthen, otherwise, alter, purpose, improving, performance, finished, product |
Exercise 2. Ask questions to the given answers:
1) Question: ___________________________________________?
2) Answer: Where specialised crops are grown on a vast commercial scale there is a distinct threat to diversity, natural forestation and the provision of foods.
3) Question: ____________________________________________________?
4) Answer: The overarching benefit of biodiesel is that as a renewable fuel it is nominally carbon-neutral.
5) Question: ____________________________________________________?
6) Answer: If biodiesel-from-crops was widely adopted as a motor fuel then there would be a knock-on effect with serious problems caused by reduced biodiversity, displaced forests and the disrupted supply of other vital agricultural products.
THE WRITING MODULE
III. Writing exercises:
Exercise 1. Complete the sentences with the suggested words:
