题目内容
New Energy Sources to the Rescue
As petrol prices rise, policy makers and venture capitalists are suddenly embracing alternatives. Will the trend last？
Reasons for the change
In his long career in country music, Willie Nelson has always been on the left side of all things. Now, at 73, he is in the vanguard. Mr. Nelson, who lives on a big farm outside Austin, powers his car with the help of vegetable oil. He has even created his own line of this cleaner-burning diesel blend (混合柴油). He called it "BioWillie", which is distributed at several sites in Texas and is going national, too. Mr. Nelson argues that it will help America's farmers, truckers and the environment while, at the same time, reducing dependence on foreign petroleum.
With high petrol prices causing troubles in Washington, D.C., everyone is trying to find out alternatives. Soya beans, canola (rapeseed), switch grass, anything, is being investigated~ Even George Bush, a former oilman who supports loyally the industrial development, called last week for more research into ethanol (酒精) and bio-diesel-two key types of bio-fuels (生物燃料) and boldly predicted that "ethanol will replace gasoline consumption". Jim Woolsey, a former head of the CIA notes that developing bio-fuels is in the national interest, since it is high time America stopped its reliance on petroleum from foreign countries and so stopped funding some fanatical religious organizations.
Future: convenience and pains
The federal government is beginning to formulate policy to promote the use of bio-fuels. In Montana, Hawaii and Minnesota all petrol must contain 10% ethanol, while Washington State requires petrol and diesel to contain 2% renewable fuel by volume. For both ethanol and bio-diesel, Congress has required a near-doubling of production by 2012. Both blends, notes Mr. Woolsey approvingly, need little new infrastructure to support them (unlike, say, hydrogen fuel-cell cars). Ethanol can be dispensed at regular petrol stations and works, within limits, in today's cars. Bio-diesel fuelling stations, such as those for BioWillie, are popping up around America.
Unfortunately for Mr. Bush's political fortunes, a bio-fuels revolution will not happen in time to ease America's current pain at the pump. Right now, ethanol--a clean-burning, high-octane alcohol typically derived from com in America, or sugar in Brazil--accounts for just 3% of America's petrol use, though American cars can handle a 10% ethanol blend. Bio-diesel is used even less.
Moreover, ethanol is typically blended with regular fuel, and a widespread shift to an ethanol blend (a result of another provision of last year's energy bill) has contributed to some petrol shortages in Texas and elsewhere, as the supply chain creaks into life. Skeptics argue that growing crops for ethanol will bum more petrol than it will save.
But others are persuaded, despite the pains at the beginning stage. "If I had to bet $100, I'd bet on bio-fuels," says Hunter Lovins, co-author of" Natural Capitalism", adding that she would favor them even over other renewable energy sources. Rich investors also believe as growth. Richard Branson, a British entrepreneur who heads the Virgin conglomerate, recently announced plans to invest up to $400 in ethanol production.
Growing production？
Can production be scaled up？ A recent bioengineering breakthrough means that it should soon be possible to convert plant products far more efficiently to ethanol. This lends promise to cellulosic ethanol— a product that can be made from agricultural "waste", such as corn cobs or weeds, which is widely available. (Once corn kernels and sugar-cane sap have been taken away for sugar, they leave plenty of stalks and leaves behind.) The most promising source of cellulosic ethanol, say experts, is switch grass, a native American grass that grows naturally in the prairie he
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Egypt Felled by Famine
Even ancient Egypt's mighty pyramid builders were powerless in the face of the famine that helped bring down their civilisation around 2180 BC. Now evidence gleaned from mud deposited by the River Nile suggests that a shift in climate thousands of kilometres to the south was ultimately to blame--and the same or worse could happen today.
The ancient Egyptians depended on the Nile's annual floods to irrigate their crops. But any change in climate that pushed the African monsoons southwards out of Ethiopia would have diminished these floods.
Dwindling rains in the Ethiopian highlands would have meant fewer plants to stablise the soil. When rain did fall it would have washed large mounts of soil into the Blue Nile and into Egypt, along with sediment from the White Nile.
The Blue Nile mud has a different isotope signature from that of the White Nile. So by analysing isotope differences in mud deposited in the Nile Delta, Michael Krom of Leeds University worked out what proportion of sediment came from each branch of the fiver.
Krom reasons that during periods of drought, the amount of the Blue Nile mud in the river would be relatively high. He found that one of these periods, from 4,50Oto 4,200 years ago, immediately predates the fall of the Egypt's Old Kingdom.
The weakened waters would have been catastrophic for the Egyptians. "Changes that affect food supply don't have to be very large to have a ripple effect in societies," says Bill Ryan of the Lamont Doherty Earth Observatory in New York.
"Similar events today could be even more devastating," says team member Daniel Stanley, a geoarchaeologist from the Smithsonian Institutions in Washington, D. C.. "Anything humans do to shift the climate belts would have an even worse effect along the Nile system today because the populations have increased dramatically."
Why does the author mention "pyramid builders"？
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