TOEFL Listening Practice: Lecture04
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MP3 – SoundCloud
Answer
- B
- B
- D
- A, C
- C
- B
Transcript
| Professor: | Alright class today we’re going to talk about a subject that indirectly affects many people, algae biodiesel. How does this affect you? Well, as, gas prices continue to rise, and the stocks of oil under the Earth’s surface are dwindling, we are in search of a new type of renewable fuel. This is essential because so many things rely on oil, not just cars, but our electricity, our plastics, almost everything in our world today uses some amount of oil. So our discussion today will focus on one of the possible alternatives, algae, which grows naturally all over the world and can be manipulated into an efficient form of diesel fuel. |
| To begin with, let’s focus on why exactly algae would be a good plant for use. First of all, there are over 100,000 types of algae across the planet. This means there are many options for growing. Secondly, algae is very easy to grow since it only requires three things, water, sunlight, and carbon dioxide. Additionally, engineers believe that the potential for growing enough algae to fuel the world is highly reasonable. With a single acre of land they can potentially grow over 100,000 gallons of oil. This means that on 100 acres we could grow enough algae to produce 10 million gallons of biodiesel. While that isn’t enough to power the whole planet, that’s a lot of oil from a relatively small amount of space given that biodiesel can be grown anywhere. | |
| Next, we should look at exactly how this process works. The first step to understanding the process is to think about juicing. Algae requires the same sort of process, whereby high pressure squeezing releases the oil from the plant. There are a few different methods for producing the algae that all result in different amounts extracted. The most efficient, but hardest to construct, is called the supercritical fluids method, and it extracts 100 percent of the oil from algae. The process requires mixing the algae with certain levels of carbon dioxide which turns all of the algae into oil. However, this method requires far more equipment and overhead in comparison to the simple oil press method to squeeze the algae. | |
| Further exploration of the topic leads to some more difficulty beyond the simple gather and squeeze method of oil collection. You should be asking, how exactly do we grow enough algae to make it worth it? Well, lucky for us scientists have been working on that. We don’t have enough open ponds to continually grow algae. However, through a method where algae is placed into plastic bags and hung, the algae can be mixed with necessary sunlight, nutrients, water, and carbon dioxide to promote vast amounts of growth. A downside to mass growth is that one simple contaminant to the system could destroy an entire crop of algae in such a linked system. Assuming that the worst doesn’t happen though, this type of growing could result in algae being harvested daily for use. The search for oil deep under the Earth’s crust would be over. | |
| So in conclusion, what are some of our pros and cons that we haven’t already talked about? The pros would be the ability to control a natural, clean, efficient form of oil to be used every day on every continent. But before we get too excited let’s think about the cons. Any open air growth of algae has a high risk of contamination which ruins the possibility for effective growth. Unfortunately, scientists haven’t quite resolved this critical issue. Further complicating the scientific reliability is that there hasn’t been much critical testing completed. Therefore, before we continue down this path, we have to ask, what further steps are we required to take before we turn over the world’s oil to the algae business. |