Gas emits about half as much carbon dioxide as coal per unit of energy produced.

天然气的二氧化碳产生量是每单位煤炭释放能量时二氧化碳产生量的一半。

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Howarth and his colleagues conclude that the greenhouse gas footprint of shale gas can be as much as 20 percent greater than, and perhaps twice as high as, coal per unit of energy.

霍沃斯和他的同事综合这些因素认为页岩气的温室气体足迹比每单位能煤炭要高20%甚至高出一倍。

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Coal contains less energy per unit of weight than weight than natural gas or oil; it is difficult to transport, and it is associated with a host of environmental issues, among them acid rain.

煤的单位能量含量低于石油和天然气，而且会导致包括酸雨在内的一系列环境问题。

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MidAmerican Energy is the operator of a 1600 megawatt four unit coal-fired power plant in Council Bluffs, Iowa, commonly known as Walter Scott, Jr.

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Estimates are that it cost double that of a coal unit, which produce twice the oomph, or BTUs, as do wood chips.

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Avg coal waste per unit: 300, 000 tons of coal ash annually.

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