Hydrous pyrolysis refers to the chemical processes which take place when material is heated to high temperatures in the presence of water.

Steam cracking is used in the petroleum industry to produce the lighter alkenes.

Hydrous pyrolysis may be a significant process in the creation of fossil fuels. Simple heating without water, anhydrous pyrolysis has long been considered to take place naturally during the catagenesis of kerogens to fossil fuels. In recent decades it has been found that water under pressure causes more efficient breakdown of kerogens at lower temperatures than without it. The carbon isotope ratio of natural gas also suggests that hydrogen from water has been added during creation of the gas.

Thermal depolymerization uses hydrous pyrolysis in the conversion of organic waste into oil.

References

• A Possible Deep-Basin High-Rank Gas Machine Via Water Organic-Matter Redox Reactions, Leigh C. Price
• Surreptitiously converting dead matter into oil and coal - Water, Water Everywhere, Science News, February 20, 1993, Elizabeth Pennisi
• HYDROGEN ISOTOPE SYSTEMATICS OF THERMALLY GENERATED NATURAL GASES, Chris Clayton
• NOVEL CATALYTIC CO-PROCESSING OF BIOWASTES WITH FOSSIL FUELS