雅思阅读 153: Beyond the Smoke — The Promise and Limits of Bioenergy（生物质能的前景与局限）

改编自 U.S. Department of Energy / ACS Publications（2025–2026年）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.energy.gov/node/1508916

Reading Passage

A. When policymakers search for replacements for coal and oil, one option keeps returning to the table: energy drawn from things that were alive. The official term is bioenergy, but the raw material is familiar enough. Biomass is any organic material that has stored sunlight in the form of chemical energy — trees left after a harvest, straw from a wheat field, wood chips, household waste, even fast-growing algae. Where a fossil fuel burns carbon laid down by prehistoric forests, biomass burns carbon that a growing plant pulled from the atmosphere only last season. It is this tight loop — capture today, release tomorrow — that lies behind the marketing slogan most often attached to the sector: carbon neutral. The logic is seductively simple. A young corn plant fixes carbon dioxide through photosynthesis; a lorry converts that plant into liquid fuel; an engine burns it, returning the gas to the sky. Because the next crop will draw the same amount back, advocates argue, the atmosphere should neither gain nor lose. Wind and solar are praised for the same reason, but they cannot easily replace the petrol that fills a fuel tank, whereas biomass can be converted directly into ethanol, biodiesel or renewable gasoline that drops into an existing engine. That compatibility with the world already built is, for many governments, the decisive argument.

B. The comforting equation, however, hides as much as it reveals. Carbon neutrality, researchers now stress, is not guaranteed by definition; it is earned, or lost, by the details of how the biomass is grown, processed, transported and burned. A mature forest cut down and replaced by a young plantation loses stored carbon for decades before the new trees catch up. Tractors, fertilisers, drying kilns and long-distance lorry journeys all consume fossil fuel, and every joule of that consumption must be subtracted from the renewable balance. Early generations of biofuels made from food crops such as corn and palm oil drew a sharper criticism still. By diverting farmland and driving up grain prices, they were accused of raising food costs and encouraging the clearing of tropical forests — a perverse outcome for a technology sold as green. The ripples reached beyond the energy system entirely, touching global hunger debates and tropical conservation at the same time. It became clear that a fuel could be renewable on paper yet harmful in practice, and that the label itself required an honest audit rather than an act of faith.

C. Those criticisms pushed the field toward a quieter second act. Instead of food crops, newer projects concentrate on waste: agricultural residues that would otherwise rot, municipal refuse that would otherwise occupy a landfill, and dedicated non-food grasses that grow on marginal soil nobody wants to plough. Chemists describe several routes to turn such material into energy. Thermochemical methods apply heat and oxygen to gasify or pyrolyse the material, while biochemical methods use microbes to ferment sugars into alcohol. A particularly ambitious variant adds a final step: bioenergy with carbon capture and storage, in which the carbon released by combustion is trapped and pumped underground rather than allowed to return to the air. Because the original carbon was absorbed by a plant, sequestering the exhaust effectively removes it from the atmosphere altogether. Engineers estimate that this combination can yield a net energy gain of roughly 18 gigajoules for every tonne of carbon dioxide captured — a rare example, in climate policy, of a technology that both supplies power and takes greenhouse gas out of the sky. It is, on paper, one of the few routes to "negative emissions" that the models of future climate scenarios routinely assume.

D. Yet even this refined version invites scepticism, and for a structural reason. Biomass is, by its nature, diffuse. A solar panel covers a roof and produces power; a tonne of biomass, by contrast, carries relatively little energy for its weight, so gathering enough of it to run a power station demands vast hinterlands of farmland or forest. The more land is devoted to energy, the more it competes with food production and with the wild habitats that conservationists are trying to protect. Critics in the academic journals argue that some models quietly assume hundreds of millions of hectares of energy crops will materialise in 2050 — an area that would rival the entire farmed territory of several continents — without specifying where that land, and the water it requires, will come from. They warn that relying on such a promise as a substitute for cutting emissions now is a form of procrastination dressed as a plan. Bioenergy, on this view, cannot be a licence to keep burning fossil fuels; it is a narrow tool whose usefulness depends on wasting nothing and planting nowhere that matters.

E. The emerging consensus is therefore neither celebration nor rejection but calibration. Bioenergy looks most defensible where it does what nothing else can: converting waste that already exists, in quantities already available, into heat, power or fuel that would otherwise be made from oil. Used that way, it recycles carbon that was going to oxidise anyway, and it recovers value from material society was discarding. Used on an industrial scale as a strategic substitute for all fossil fuel, by contrast, it begins to collide with the limits of land. The smart policy, researchers conclude, is not to crown biomass as the hero of the energy transition but to reserve it for the narrow niche where its advantages are real and its downsides manageable. In that sense the story of bioenergy mirrors the wider story of the green shift: the most attractive technology is rarely the one with the most glowing slogan, but the one whose limits an honest society is willing to measure.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. A technical route that could remove carbon from the air entirely ii. Why bioenergy burns carbon only recently captured iii. The hidden conditions behind "carbon neutral" iv. The global rise in food prices caused by cooking oil v. Why biomass cannot simply scale to replace all fossil fuels vi. The countries that export the most ethanol vii. A measured, narrow role for the technology

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why is biomass often described as carbon neutral? A. It contains no carbon at all when it burns. B. The carbon it releases was recently absorbed by growing plants. C. It burns more cleanly than natural gas. D. It produces no waste by-products.

6. What criticism was directed at early biofuels made from food crops? A. They were too expensive to distil. B. They could not be used in ordinary engines. C. They diverted farmland and could drive deforestation. D. They released more sulphur than coal.

7. What is distinctive about bioenergy with carbon capture and storage? A. It needs no fuel to operate. B. It can produce negative emissions by trapping released carbon underground. C. It works only at room temperature. D. It requires no biological material.

8. According to critics, what structural problem limits biomass? A. It cannot be converted into liquid fuel. B. Its energy is diffuse, so large amounts of land are needed to scale it. C. It decomposes too quickly to transport. D. It produces energy only at night.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Biomass stores sunlight in the form of chemical energy.
10. Carbon neutrality is guaranteed automatically by the biological origin of the fuel.
11. Bioenergy with carbon capture and storage yields roughly 18 gigajoules of net energy per tonne of carbon dioxide captured.
12. Most commercial bioenergy projects now use tropical palm oil as their feedstock.
13. Several European nations have banned the construction of new biomass power stations.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Rather than food crops, newer projects focus on (14) __________ that would otherwise be thrown away, while an advanced variant that traps exhaust can in principle deliver (15) __________ emissions.

答案与解析

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