Biogas: a Solution to Many Problems
In almost all developing countries, the lack of adequate supplies of cheap, convenient and reliable fuel is a major problem. Rural communities depend largely on kerosene, wood and dung for their cooking and lighting needs. But kerosene is now priced out of reach of many people and wood, except in heavily forested areas, is in short supply. The search for firewood occupies a large part of the working day and has resulted in widespread deforestation.
Dung is in constant supply wherever there are farm animals and, when dried, it is convenient to store and use. But burning dung destroys its value as fertilizer, thus depriving the soil of a much needed source of humus and nitrogen.
Rural areas of developing countries are also plagued by a lack of adequate sanitation. Improper waste disposal spreads disease, contaminates water sources and provides breeding grounds for disease-carrying insects.
The problem of improving environmental hygiene, conserving resources and finding alternative sources of fuel may be unrelated. Their solutions, however, are not, as many countries experimenting with biogas technology arc discovering. Biogas, a mixture of methane and carbon dioxide, is produced by the fermentation of organic matter. The process of anaerobic fermentation is a natural one, occurring whenever living matter decomposes. By containing the matter — and the process — in a digester or biogas plant, the combustible gas can be trapped and used as fuel for household lighting and cooking. The digested slurry that remains can be used on the land as a soil conditioner and fertilizer.
Biogas plants have attracted much interest in recent years and they are in use in several Asian countries: 36,000 are reported in rural areas of India, 27,000 in Korea and more than 80,000 in China. In most countries, the value of the gas has been the prime factor leading to their adoption: 70 per cent of India’s plants, for instance, were built during the energy and fertilizer crisis of 1975-76 — although their use in that country dates back to 1951. Similarly in Thailand and Korea, biogas is being investigated as an alternative to costly charcoal and to save compost materials from being burned.
In Japan and China, reducing pollution from animal wastes has been an important factor. Privies, hen houses and pigpens are built in proximity to the fermentation chamber in China. Examinations of the digested slurry have shown that the total number of parasite eggs was reduced by 93.6 per cent, hookworms by 99 per cent and no flukes were found.
The greatest benefits from biogas systems, however, are probably to be derived from the manurial value of the slurry, although it is not widely used outside of India and China. Vegetable farmers near Calcutta found that the digested slurry produced bigger and better tasting peas than did other fertilizers and the weight of root vegetables increased by nearly 300 per cent.
The production of biogas by of animal and vegetable wastes is a technology that has been largely developed and used in the countries. Only very recently have scientists in the industrialized nations begun to show an interest — presumably because of the energy .
Family-sized biogas first came into widespread use in India in the 1950s in an effort to make a cleaner and efficient use of cattle . The programme really expanded in the 1970s, and today there are as many as 100,000 plants throughout the world. Most are in domestic use to provide fuel for and but some larger units are operated in order to recycle wastes, supply fertilizer, control pollution and improve . One Chinese study has shown that digestion of animal in the air-tight digesters greatly reduces health hazards from parasitic diseases. One Indian study has estimated that the value of the obtained is in itself greater than the cost of producing the . Thus, the system is economically sound, in addition to other benefits such as a cleaner, healthier environment.
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Question Focus: Synonym match - summary says 'production of biogas by ___ of animal and vegetable wastes'
Correct Answer: fermentation
Why this is correct: The passage explains that biogas is produced by fermentation of organic matter. Animal and vegetable wastes are types of organic matter, so fermentation fits perfectly.
Passage Reference: Biogas, a mixture of methane and carbon dioxide, is produced by the fermentation of organic matter. The process of anaerobic fermentation is a natural one, occurring whenever living matter decomposes.
Common Mistake: Students may write decomposition because the passage mentions it, but the passage clearly names the process as fermentation. You must copy the exact word. This is a synonym trap.
Paraphrasing: Passage: 'produced by the fermentation of organic matter' = Summary: 'production of biogas by ___ of animal and vegetable wastes'
Tips: When you see 'by + gap', expect a noun naming a process.
Key Vocabulary:
- fermentation = natural breakdown process
- organic matter = plant or animal material
Question Focus: Synonym match - where the technology is mainly used
Correct Answer: developing
Passage Reference: In almost all developing countries, the lack of adequate supplies of cheap, convenient and reliable fuel is a major problem. Rural communities depend largely on kerosene, wood and dung for their cooking and lighting needs.
Why this is correct: The passage repeatedly focuses on developing countries as the main users of biogas technology. The summary shortens this to developing countries.
Common Mistake: Some students write Asian because examples are from Asia, but the passage talks more broadly about developing countries. This is a partial truth trap.
Paraphrasing: Passage: 'developing countries' = Summary: 'the ___ countries'
Tips: Do not replace passage words with your own. Copy exactly what fits.
Key Vocabulary:
- developing = poorer, less industrialized
Question Focus: Cause for new interest in industrialized nations
Correct Answer: crisis
Passage Reference: were built during the energy and fertilizer crisis of 1975-76
Why this is correct: The passage links increased interest to the energy and fertilizer crisis. The summary shortens this to energy crisis.
Common Mistake: Students may write shortage or problem, but these words are not in the passage. This is a synonym trap.
Paraphrasing: Passage: 'energy and fertilizer crisis' = Summary: 'energy ___'
Tips: If the summary shortens a phrase, usually one key word stays the same.
Key Vocabulary:
- crisis = serious problem
Question Focus: Naming the biogas equipment
Correct Answer: plants
Passage Reference: Biogas plants have attracted much interest in recent years and they are in use in several Asian countries: 36,000 are reported in rural areas of India, 27,000 in Korea and more than 80,000 in China. In most countries, the value of the gas has been the prime factor leading to their adoption: 70 per cent of India's plants, for instance, were built during the energy and fertilizer crisis of 1975-76 - although their use in that country dates back to 1951.
Why this is correct: The passage consistently calls them biogas plants, so plants is the correct word to complete the summary.
Common Mistake: Writing systems or digesters changes the wording from the passage. This is a synonym trap.
Paraphrasing: Passage: 'Biogas plants' = Summary: 'Family-sized biogas ___'
Tips: Check singular or plural carefully.
Key Vocabulary:
- plant = facility or installation
Question Focus: Material used from cattle
Correct Answer: dung
Passage Reference: Dung is in constant supply wherever there are farm animals and, when dried, it is convenient to store and use.
Why this is correct: The passage explains that dung from farm animals is used and discussed in detail, especially in India.
Common Mistake: Students may write manure, but that word is not used in the passage. This is a synonym trap.
Paraphrasing: Passage: 'Dung is in constant supply' = Summary: 'use of cattle ___'
Tips: Use the exact noun from the passage, not a similar one.
Key Vocabulary:
- dung = animal waste
Question Focus: Domestic use of biogas
Correct Answer: cooking
Passage Reference: used as fuel for household lighting and cooking.
Why this is correct: The passage clearly states that biogas is used for household lighting and cooking. The summary follows the same order.
Common Mistake: Reversing the order causes confusion later. This is a wrong order trap.
Paraphrasing: Passage: 'fuel for household lighting and cooking' = Summary: 'fuel for ___ and ___'
Tips: Keep the same order as the passage.
Key Vocabulary:
- cooking = preparing food
Question Focus: Second domestic use of biogas
Correct Answer: lighting
Passage Reference: used as fuel for household lighting and cooking.
Why this is correct: Along with cooking, lighting is directly named as a main use of biogas in homes.
Common Mistake: Students sometimes repeat cooking again. This is a careless repetition trap.
Paraphrasing: Passage: 'lighting and cooking' = Summary: '___ and ___'
Tips: When two gaps are joined by 'and', look for paired words in the passage.
Key Vocabulary:
- lighting = providing light
Question Focus: Additional benefits of biogas systems
Correct Answer: sanitation
Passage Reference: Rural areas of developing countries are also plagued by a lack of adequate sanitation. Improper waste disposal spreads disease, contaminates water sources and provides breeding grounds for disease-carrying insects.
Why this is correct: The passage talks about improving sanitation and environmental hygiene as major benefits. Any of the listed answers match the passage.
Common Mistake: Writing health is too general and not the passage word. This is a partial truth trap.
Paraphrasing: Passage: 'improving environmental hygiene' = Summary: 'improve ___'
Tips: If more than one answer is possible, choose the simplest exact word.
Key Vocabulary:
- sanitation = clean waste systems
- hygiene = cleanliness
Question Focus: Material digested in biogas plants
Correct Answer: waste
Passage Reference: reducing pollution from animal wastes has been an important factor. Privies, hen houses and pigpens are built in proximity to the fermentation chamber in China. Examinations of the digested slurry have shown that the total number of parasite eggs was reduced by 93.6 per cent, hookworms by 99 per cent and no flukes were found.
Why this is correct: The passage mentions animal wastes being digested, which reduces disease. Singular or plural is accepted.
Common Mistake: Choosing something not linked to disease reduction is wrong. This is a context shift trap.
Paraphrasing: Passage: 'animal wastes' = Summary: 'animal ___'
Tips: Check if the noun can be singular or plural in the sentence.
Key Vocabulary:
- waste = unwanted material
- slurry = wet mixture
Question Focus: Economic value of biogas by-products
Correct Answer: fertilizer
Passage Reference: The greatest benefits from biogas systems, however, are probably to be derived from the manurial value of the slurry, although it is not widely used outside of India and China.
Why this is correct: The passage says the slurry has great manurial value and is used as fertilizer, which is very valuable.
Common Mistake: Writing gas misunderstands the sentence focus. This is a context shift trap.
Paraphrasing: Passage: 'used on the land as a soil conditioner and fertilizer' = Summary: 'value of the ___ obtained'
Tips: Watch what the value refers to, not just the main topic.
Key Vocabulary:
- fertilizer = plant food
Question Focus: Cost comparison
Correct Answer: biogas
Passage Reference: value of the slurry, although it is not widely used outside of India and China. Vegetable farmers near Calcutta found that the digested slurry produced bigger and better tasting peas than did other f
Why this is correct: The passage clearly compares the value of fertilizer with the cost of producing the biogas.
Common Mistake: Students sometimes repeat fertilizer, but the comparison is with production cost of biogas. This is a logic trap.
Paraphrasing: Passage: 'cost of producing the biogas' = Summary: 'cost of producing the ___'
Tips: Read the full sentence to see what is being compared.
Key Vocabulary:
- biogas = fuel gas from waste
General Tips:
- FIB questions follow passage order. Use your last answer to find the next one faster.
- Always copy the exact word from the passage. Synonyms are usually wrong.
- Check grammar carefully. Articles, prepositions, and plurals give strong clues.
- Keep an eye on the word limit. One extra word makes the answer wrong.
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