Đề thi & Đáp án IELTS Recent Actual Test – Reading passage 2 – Biofuels


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A Soon, we’re told, corn crops will be as valuable as oil. This is because corn and a few other crops are being promoted as the ‘biofuels’ of the future. Biofuel is an umbrella term used to describe all fuels derived from organic matter. The two most common biofuels are bioethanol, which is a substitute for gasoline, and biodiesel. Not only have soaring oil prices made biofuels economically viable for the first time in years, but they could also help countries reduce their dependency on fossil fuel imports. However, the real plus point in the minds of many is their eco-friendly image.

B Supporters claim they will cut our net greenhouse gas inputs dramatically, because the crops soak up carbon dioxide from the atmosphere as they grow. Given this fact, it’s no surprise that politicians and environmentalists the world over are backing the idea, hoping we will soon be using this green alternative to power our cars, buses and trains. Other scientists, however, have begun to question the environmental and social arguments for biofuels. Far from solving our problems they believe biofuels will destroy rainforests, suck water reserves dry, kill off species and raise food prices. Worst of all, they claim that many biofuels will barely slow global warming at all if the technology behind them does not improve. Biofuel supporters counter that it’s still early days, and we should give this technology the time and investment to deliver on its promise. So who’s right?

C The controversy may be brand new, but the biofuels themselves are an old idea. The Model T Ford, first produced in 1908, was designed to run on ethanol, and Rudolf Diesel, who invented the diesel engine in 1892, ran his demonstration model on peanut oil. Biofuels fell out of favour as petroleum-based fuels appeared and became cheaper to produce, but, after the oil crisis of the early 1970s, some countries returned to biofuels. For example, Brazil has been producing large quantities of ethanol from sugar cane for over 30 years. Brazilian law now requires that 20 per cent of fuel be blended with bioethanol, which all gasoline-powered cars can tolerate. Over 15 per cent of Brazil’s cars can even run on pure bioethanol.

D According to a recent study by the Worldwatch Institute, for Brazil to produce ten per cent of its entire fuel consumption requires just three per cent of its agricultural land, so it’s not surprising that other places want to emulate Brazil’s approach. The problem is that in most other countries, the numbers don’t add up. The same study estimated that to meet that ten per cent target, the US would require 30 per cent of its agricultural land, and Europe a staggering 72 per cent. It’s no secret why things stack up so differently. Not only do Brazilians drive far less than Europeans and Americans, their fertile land and favourable climate mean their crop yields are higher, and their population density is lower.

E Several research groups have tried to compare fossil fuel emissions with those of corn bioethanol at every stage of production from seed sowing to fuel production. The studies have been beset by scientific uncertainties, such as how much of the greenhouse gas nitrous oxide is produced by the nitrogen fertiliser used in growing corn. Opinions are divided as to what should and should not be included in the calculations, which means the results vary widely, but a study by David Pimentel at Cornell University in New York concluded that corn ethanol creates more greenhouse gases than burning fossil fuels.

F Another reason a growing number of people oppose biofuels is that growing corn for ethanol uses up land that is currently supplying food to the world. According to Lester Brown, veteran commentator and activist on food politics, the corn required to fill a 4×4 tank with bioethanol just once could feed one person for a year. He predicts that a boom in bioethanol would lead to a competition between the 800 million people in the world who own automobiles and the three billion people who live on less than $2 a day, many of whom are already spending over half their income on food.

G So are we utterly mistaken to think that bioethanol could usher in an era of greener energy? The way things are developing, it certainly looks that way, but it needn’t be so. Scientists want to perfect a way to make biofuels from non-food crops and waste biomass, saving the corn and other food crops for food use, and to do it without wrecking natural ecosystems. Already researchers are discovering ways to convert cellulose-rich organic matter into ethanol. Cellulose is the main structural component of all green plants. Its molecules comprise chains of sugars strong enough to make plant cell walls. If you could break down those molecules to release the sugars they contain, you could ferment them until ethanol is created. Developing such a process could open the door to many non-food materials such as switchgrass – a wild grass that thrives in the eastern states and Midwest of the US – straw, crop residues like stalks and hardwood chips. Its supporters say these cellulose materials could deliver twice as much ethanol per hectare as corn, and do it using land that is today neither economically productive nor environmentally precious. Some even think municipal waste such as paper, cardboard and waste food could also be used. If the numbers add up this could be the development that may yet deliver us from our dependence on oil, without costing us the Earth in the process.


Questions 14-19: Reading Passage 2 has seven paragraphs, A-G. Which paragraph contains the following information?
Which paragraph contains the following information?
Write the correct letter A-G in boxes 14-19

14 reasons for the success of bioethanol production in one region
15 an individual’s prediction of the consequences of increasing production of corn ethanol
16 a reference to why biofuels might help to slow down global warming
17 a definition of biofuel
18 a reference to research that found one type of bioethanol to be less ecofriendly than oil
19 examples of how ethanol was used as a fuel before petroleum

Questions 20-25: Complete the summary below.
Choose NO MORE THAN TWO WORDS from the passage.

Using Non-Food Crops to Make Biofuels
A major constituent of green plants is cellulose. The (20) of cellulose are made up of sugars. These form the (21) of plants. Ethanol could be produced by extracting the sugars and allowing them to (22) One common North American plant that could be used in this method is (23) Some scientists believe that this would be a more productive source of ethanol than (24) Additionally, the source plant materials could be grown in ground which is not currently being used for agriculture and is not (25)valuable.

Questions 26: Choose the correct letter, A, B, C or D.
What conclusion does the writer of the text come to?

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