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 far mankind than the “first”, or oil crisis. It takes the form of deforestation, with loss of green cover its 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. Mast 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 platation 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.

 

The above reading passage has nine paragraphs A – I. Choose the most suitable headings for paragraphs B – I from the list of headings below. Write the appropriate numbers (1-10) in the spaces provided.NB: There are more headings than the paragraphs so you will not use all of them. You may use any of the headings more than once.

List of heading
1. Fuels from biological sources	6. Plant power
2. Research and development into biomass systems	7. Efficiency of the solar conversion process
3. Solar energy and its utilization	8. Tree biomass
4. The energy crisis and photosynthetic systems	9. Other forms of renewable energy
5. The second energy crisis	10. Liquid and gaseous fuels from biomass

 Đáp án: A. 3; B.7; C.1; D.5; E.4; F. 6;  G.2; H.8; I.10