The diesel-extraction method for coffee grounds is similar to that used for other vegetable oils.

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In March, energy company Cuadrilla said it had delayed plans to use the shale gas extraction method in the county until 2014.

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The extraction method is really quite simple.

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He added that shale gas extraction, which could involve using the fracking method, was a "long way off".

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In these zones, a method known as in-situ extraction is used.

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