Carbon dioxide is produced as a crude by-product of a number of manufacturing processes.

二氧化碳是作为许多工业生产过程的天然副产品生产的。

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The plan: extract 1.5 million gallons of green crude oil a year from patented pond scum fed a diet of carbon dioxide and sunlight.

FORBES: The U.S. Military's Great Green Gamble Spurs Biofuel Startups

For their calculations, the two assumed that where there was a gap between demand and conventional supply it would be filled with synthetic fuels, first with tar-sands oil and later with oil from coal and shale. (According to high-end estimates, coal and oil shale could together yield some ten trillion barrels of unconventional crude.) They then calculated what the impact would be on global carbon-dioxide levels.

NEWYORKER: Unconventional Crude