| TRUE | if the statement agrees with the information |
| FALSE | if the statement contradicts the information |
| NOT GIVEN | if there is no information on this |
Energy from Biological Sources
A. Radiation from the sun is the earth’s primary source of energy. More than 99 per cent of the processes that are happening on earth are energized by the sun either directly or indirectly. As solar radiation is a permanent and renewable source of energy, why, then, do we have an “energy crisis”? The problem, of course, lies in how to utilize this energy. It is diffuse and intermittent on a daily and seasonal basis, thus collection and storage costs can be high. But we already have at our disposal a means of capturing and storing a proportion of this energy, and we have always had such a means. It is plant life — the “biomass”. The process involved is photosynthesis.
B. This capture of solar energy and conversion into a stored product occurs, with only a low overall efficiency of about 0.1 per cent on a world-wide basis but because of the adaptability of plants, it takes place and can be used over most of the earth.
C. We should remember two things about this energy source. First, the world's present and precarious dependence on fossil fuels — first coal, and then oil — is only about two hundred years old. Before that, most of the energy required by human beings for heating, cooking and industrial purpose was supplied from biological sources. By this, we mean mainly wood, or its derivative, charcoal. Secondly, wood still accounts for one sixth of the world’s fuel supply. In the non-OPEC developing countries, which contain 40 per cent of the world’s population, non-commercial fuel often comprises up to 90 per cent of their total energy use. With the increasingly doubtful future of fossil fuel supplies, fuel from biological sources may have to become even more important.
D. Traditional fuels of biological origin include wood, charcoal, agricultural residues such as straw and dried animal dung. With the growth in world population, there has been increasing pressure on these resources, leading to what is sometimes called the “second energy crisis”. This is more drastic for mankind than the “first”, or oil crisis. It takes the form of deforestation, with loss of green cover in hot lands, leading to desiccation and the loss of fertile land to desert.
E. The threat from both energy crises can be partly met by utilizing the enormous supply of energy built up annually in green plants. The question is, how should this be done? In the past, photosynthesis has given us food, fuel wood, fibre and chemicals. It has also, ultimately, given us the fossil fuels — coal, oil and natural gas, but these are not renewable while the other products are. Recently, however, with abundant oil, the products of present-day photosynthesis are mainly evident to the developed world as food. We should re-examine and, if possible, re-employ the previous systems; but, with today’s increased population and standard of living, we cannot revert to old technology and must instead develop new means of using present-day photosynthetic systems more efficiently.
F. Fortunately for us, plants are very adaptable and exist in great diversity — they could thus continue indefinitely to supply us with renewable quantities of food, fibre, fuel and chemicals. If the impending fuel problem which is predicted within the next ten to fifteen years comes about, we may turn to plant products sooner than we expect. Let us be prepared!
G. Some basic research can be done centrally, without reference to the conditions in any one country. For example, all plant energy storage depends ultimately on the process of photosynthesis. Experiments are being made to see whether this process can either be speeded up, or even reproduced artificially, in order to produce a higher efficiency in energy extraction. Most research should be done locally, however, because of climatic and vegetation differences, and also because of the difference in needs and emphasis in varying countries. Such research and development is an excellent opportunity to encourage local scientists, engineers and administrators in one field of energy supply. Even if biomass systems do not become significant suppliers of energy in a specific country in the future, the spin-off in terms of benefits to agriculture, forestry, land use patterns and bioconversion technology is certain to be valuable.
H. What are the methods currently in use or under trial for deriving energy from biomass? The first is the traditional use outlined in paragraph C, which may be termed the “non-commercial” use of biomass energy. The second also has a long traditional history: the use of wood-fuel under boilers to generate steam. This has now been revised on an intensive scale. In a study from the Philippines, it has been estimated that a 9,100 hectare fuel wood plantation “would supply the needs of a 75 megawatt steam power station if it were not more than fifty kilometres distant”. Such a plantation would use a species of fast-growing tree — leucaena leucocephala, or the giant “ipil-ipil”. The investment requirements and cost of power produced looks favourable and competitive with oil-fired power stations of similar capacity. In addition, residues from cropland after harvest and from sawmills could be used as steam-producing fuel. The steam could then be used to generate electricity.
I. There are also bioconversion processes to produce liquid fuels such as oil and alcohol. Some fuel oils can be pressed directly from certain crops. Alcohols, on the other hand, can be produced by converting plant material by fermentation. Ethanol (ethyl alcohol) can be extracted from growing plants such as sugar cane, from waste plant, material, or from whole grain. Methanol (methyl alcohol) can be produced from coal, wood, sewage and various waste products. These alcohols have several industrial uses and can also be used as fuels in the internal combustion engines of vehicles. Technology is already advanced, and the main problem is devising ways of collecting enough organic material to make the installations commercially viable. Some crops can be grown specifically for this purpose. In other cases, the installations can make use of the residue, or “trash” produced in the large-scale plantation farming of such crops as sugar cane and pineapple. Another fuel product produced by a fermentation process is fuel gas of various kinds, including a biogas called methane. Several of these processes can be applied to household or municipal wastes and refuse — a large and concentrated source in all big towns and cities.
AI explanationShows the answer. Tap to open.
Question Focus: Synonym match - different plant products are all forms of biomass energy
Correct Answer: TRUE
Why this is correct: The passage clearly states that food, fuel wood, and fibre all come from photosynthesis and are products of plant biomass. This shows that plant material grown for different purposes is still a potential energy source.
Passage Reference: In the past, photosynthesis has given us food, fuel wood, fibre and chemicals. It has also, ultimately, given us the fossil fuels - coal, oil and natural gas, but these are not renewable while the other products are. In the past, photosynthesis has given us food, fuel wood, fibre and chemicals.
Common Mistake: Some students think this is NOT GIVEN because the passage does not say the word farmers. But the passage talks about plant products in general, which includes crops grown by farmers. This is a Paraphrase trap.
Paraphrasing: Passage: 'food, fuel wood, fibre' = Statement: 'food, fuel or fibre'
Tips: Do not focus on missing small words like 'farmers'. Focus on whether the idea is clearly stated.
Key Vocabulary:
- biomass = plant material
- photosynthesis = how plants make energy
Question Focus: Synonym match - ethanol used as fuel
Correct Answer: TRUE
Passage Reference: Ethanol (ethyl alcohol) can be extracted from growing plants such as sugar cane, from waste plant, material, or from whole grain. Ethanol (ethyl alcohol) can be extracted from growing plants such as sugar cane
Why this is correct: The passage directly says that ethanol can be extracted from sugar cane. It also explains that these alcohols can be used as fuels in the internal combustion engines of vehicles, which means motor fuel.
Common Mistake: Students sometimes mark this NOT GIVEN because the sentence does not say 'important crop'. But importance is clear from the fact it is used to produce fuel. This is a Synonym match.
Paraphrasing: Passage: 'ethanol can be extracted from sugar cane' = Statement: 'used to produce ethanol'
Tips: If the passage gives a clear example, that is enough to confirm TRUE.
Key Vocabulary:
- ethanol = alcohol fuel
- extracted = taken out
Question Focus: Contradiction - benefits are not limited to certain countries
Correct Answer: FALSE
Passage Reference: Even if biomass systems do not become significant suppliers of energy in a specific country in the future, the spin-off in terms of benefits to agriculture, forestry, land use patterns and bioconversion technology is certain to be valuable. Even if biomass systems do not become significant suppliers of energy in a specific country
Why this is correct: The passage says that any country can benefit, even if biomass does not supply much energy there. This directly contradicts the idea that only developing countries with large land areas can benefit.
Common Mistake: Students choose NOT GIVEN because developing countries are mentioned elsewhere. But here the passage clearly says benefits are not limited. This is a Contradiction trap.
Paraphrasing: Passage: 'any specific country' = Statement: 'only developing countries'
Tips: Watch out for words like 'only'. They often make statements FALSE.
Key Vocabulary:
- spin-off = extra benefit
- specific = particular
Question Focus: Time reference - historical use
Correct Answer: TRUE
Passage Reference: Before that, most of the energy required by human beings for heating, cooking and industrial purpose was supplied from biological sources. By this, we mean mainly wood, or its derivative, charcoal. Before that, most of the energy required by human beings for heating, cooking
Why this is correct: The passage explains that before fossil fuels, people used wood and charcoal for cooking. Since fossil fuel dependence is only about two hundred years old, this confirms long-term use.
Common Mistake: Some students look for an exact number of years and choose NOT GIVEN. That is unnecessary. This is a Time/tense trap.
Paraphrasing: Passage: 'before fossil fuels' = Statement: 'for hundreds of years'
Tips: Use historical time clues like 'before that' to judge long periods.
Key Vocabulary:
- derivative = product made from
- fossil fuels = coal and oil
Question Focus: Reverse meaning - deforestation causes damage
Correct Answer: FALSE
Passage Reference: It takes the form of deforestation, with loss of green cover in hot lands, leading to desiccation and the loss of fertile land to desert. leading to desiccation and the loss of fertile land to desert
Why this is correct: The passage clearly says deforestation causes desiccation and loss of fertile land, which is the opposite of improving fertility. This is a direct contradiction.
Common Mistake: Some students misread and think deforestation is a planned solution. This is a Reverse meaning trap.
Paraphrasing: Passage: 'loss of fertile land' = Statement: 'improve the fertility of the land'
Tips: Always check whether the passage describes positive or negative effects.
Key Vocabulary:
- desiccation = drying out
- fertile = good for farming
Question Focus: Contradiction - comparison of fuel use
Correct Answer: FALSE
Passage Reference: In the non-OPEC developing countries, which contain 40 per cent of the world's population, non-commercial fuel often comprises up to 90 per cent of their total energy use. non-commercial fuel often comprises up to 90 per cent of their total energy use
Why this is correct: The passage states that non-OPEC developing countries rely heavily on biological fuel. There is no statement that OPEC countries use more. The comparison shows the opposite.
Common Mistake: Students assume oil-producing countries still use lots of biomass. This is outside knowledge. This is a Contradiction trap.
Paraphrasing: Passage: 'non-OPEC developing countries' = Statement: 'developing world in general'
Tips: Do not add your own knowledge. Compare exactly what the passage says.
Key Vocabulary:
- non-commercial fuel = traditional fuel
- comprises = makes up
Question Focus: Cause and effect - problems increased with population growth
Correct Answer: TRUE
Passage Reference: With the growth in world population, there has been increasing pressure on these resources, leading to what is sometimes called the 'second energy crisis'. With the growth in world population, there has been increasing pressure on these resources
Why this is correct: The passage links serious problems to population growth. This means when population levels were lower, these problems did not exist.
Common Mistake: Some students mark NOT GIVEN because the passage does not say 'no problems'. But the cause is clear. This is a Causation trap.
Paraphrasing: Passage: 'with the growth in world population' = Statement: 'when population levels were low'
Tips: Look for cause words like 'with the growth' to understand timing.
Key Vocabulary:
- pressure = stress
- resources = supplies
General Tips:
- TFNG questions follow passage order. Use the previous answer to find the next one faster.
- If a statement uses words like 'only' or 'all', check carefully. These often make the statement FALSE.
- FALSE means the passage says the opposite. NOT GIVEN means the passage is silent about the specific claim.
- Do not use your own knowledge. Only trust what is written in the passage.
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