Medicine salesmen were frequently tarred and feathered or given involuntary cosmetic surgeries when their clients caught up with them when coal tar was used in medicines.
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Prosecutors said the company also illegally stored and disposed of hazardous waste without a permit, instructing workers to mix coal tar sludge, a listed hazardous waste that contains benzene, on the ground.
Originally they were derived from coal-tar, the black viscous waste product left over from distilling coal for gas.
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There is oil aplenty of other sorts (tar sands, liquefied coal and so on), so the stuff is unlikely to run out for a long time yet.
Unconventional sources of oil and gas that are set for further exploitation include Canada's tar sands, shale and coal-bed methane deposits around the world.
Crude oil, or its substitutes, will be produced for decades, but at an increasingly expensive tariff, both in terms of cost and energy, as it is sourced in the form of a heavy, sour (high-sulphur) material, or in synthetic form from tar-sands, shale and coal.
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.
The greens may not be able to stop the Canadians from extracting oil from the Alberta tar sands, but they would succeed in wiping out American coal-fired power.
Both Mr Obama and Mr Harper made particular mention of carbon capture and sequestration, an unproven and expensive technology that could eventually be used on the coal plants that produce about 70% of American electricity, or on the upgraders and refineries in the tar sands.
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