destructive distillation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A process by which organic substances such as wood, coal, and oil shale are decomposed by heat in the absence of air and distilled to produce useful products such as coke, charcoal, oils, and gases.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry The heating of a material, such as coal or wood, in an inert atmosphere, at a high temperature such as to cause decomposition; the principal products include oils and tars from which many useful organic compounds may be obtained; town gas and coke were obtained in this way.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun heating a solid substance in a closed container and collecting the volatile products