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  3. In an age of increasing environmental sensitivity, conventional plastics made from fossil fuels have come to be regarded as rath

In an age of increasing environmental sensitivity, conventional plastics made from fossil fuels have come to be regarded as rath

admin2012-01-14  64
问题    In an age of increasing environmental sensitivity, conventional plastics made from fossil fuels have come to be regarded as rather dubious materials, ones that are useful and commonplace yet also to blame for some of the ecological problems that we are facing in the twenty-first century. Fortunately, there is a solution within reach: biopolymers, which are analogous to conventional plastics but superior in several ways.
   One of the greatest advantages of biopolymers is their biodegradability. Biodegradation refers to the biological process by which the activity of microorganisms causes an organic material to degrade. In terms of biopolymers, what this means is that while conventional plastics pile up in landfills and litter our streets and parks, biopolymers disintegrate easily over time, turning into carbon dioxide, methane, and other compounds, and therefore contributing less pollution to the environment than traditional plastics.
   There are other environmental benefits of biopolymers as well. Foremost among them is their suitability for sustainable use. Biopolymers can meet the world’s need for a plastic material and do so in a way that does not jeopardize future generations’ natural resources. This is because biopolymers are manufactured from products like potatoes, corn, and wheat--commodities that are renewable, unlike fossil fuels.
   Already, biopolymers are being produced on a large scale as replacements for conventional plastics and have proven to be just as sturdy. For example, in the construction industry, biopolymers have found numerous applications and in fact are sometimes preferred over synthetic plastics because of their unique properties. Some of the important construction- related functions biopolymers perform include water retention, thinning effects, and set acceleration. In addition, biopolymers can be found in food and beverage containers, packaging materials, textiles, and paper products. New research into biopolymers is also exploring ways that these special plastics can be processed to produce new materials.
   [L]ECIURE

   [R]ESPONSE
   TOEFL Writing
   Summarize the points made in the lecture, being sure to explain how they cast doubts on the points made in the reading passage.
   225 WORDS
选项
答案 [L] ECTURE SCRIPT [Professor] (female) We’re living in the age of plastics, and the problems inherent in our unchecked use of them are becoming more and more evident. These materials last forever and pollute our environment. What’s the solution? Some might argue that the answer lies in biopolymers. However, I disagree, as there are a number of problems with biopolymers as well. In my opinion, they aren’t a suitable alternative to traditional plastics. For one thing, biopolymers don’t disintegrate very easily, contrary to what you might have heard. The thing is, very specific conditions must be met in order for biopolymers to degrade properly--humidity and temperature play a key part. I suppose if you live in a warm, humid climate, this wouldn’t be much of a problem, but for everyone else, biopolymers are essentially the same as any other plastic. Even when they do degrade, biopolymers can pose problems because they sometimes contain harmful additives that are released into the environment as they break down. And biopolymers are not without their negative environmental impact, even if they are made from renewable resources like corn or potatoes. Think about how much plastic we use, and how much corn and potatoes are required to supply our biopolymer needs. Well, the agricultural industry needs a great deal of energy in order to grow our crops, and these processes produce pollution as well. So biopolymers still have a major environmental impact...it’s just a different environmental impact than that of traditional plastics. Another unfortunate drawback of biopolymers is that they’re unsuitable for use in certain applications, because their sturdiness is unproven and they are vulnerable to heat and moisture. Some pretty major limitations, right? And that’s on top of the environmental problems I already talked about. When you take all of this into consideration, it’s hard to see how biopolymers are much of a step up from traditional plastics. [R]ESPONSE In the reading passage, three advantages of the use of biopolymer plastics are discussed. In the lecture, on the other hand, the professor addresses those socalled advantages and describes ways in which they are not actually beneficial. First, the professor casts doubt on the idea that biopolymers break down quickly and harmlessly. According to the lecture, there have to be certain environmental conditions present for this to occur, and even when they do disintegrate, they can give off harmful substances. This contradicts the reading’s assertion that biopolymers are more biodegradable than regular plastics. Next, the professor goes on to describe how biopolymers contribute to pollution just like other plastics. While it is true that biopolymers are made from things like crops instead of synthetic chemicals, it is unavoidable that polluting energy is used to grow the crops. So even though the pollution caused by biopolymer production is different from that of traditional plastics, it is still a problem. And finally, the professor calls into question the sturdiness of biopolymers. According to the reading passage, they are quite sturdy and useful, but the professor says that the strength of biopolymers is unproven and that they could be vulnerable to heat and moisture.
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