pyrolyzed

Pyrolyzed is an adjective describing a material that has undergone pyrolysis, a thermochemical decomposition of organic matter at elevated temperatures in the absence or limited presence of oxygen. Pyrolysis differs from combustion (oxidation) and gasification (partial oxidation). The process typically occurs in reactors or kilns at temperatures ranging roughly from 350 to 900°C, with heating rate and residence time determining the outcome. Fast or flash pyrolysis favors liquids; slow pyrolysis favors solid char formation.

During pyrolysis, feedstock is broken down into three main product streams: solid char, condensable liquids (bio-oil or tar), and non-condensable gases (syngas). The exact distribution depends on feedstock composition, temperature, heating rate, and reactor conditions. Pyrolyzed products often exhibit increased carbon content and aromatic structures, with porosity that makes them useful as carbon materials, adsorbents, or fuels.

Applications. Pyrolyzed biomass yields biochar used to improve soil fertility and sequester carbon; pyrolysis oil can be upgraded to fuels or chemical feedstocks; charcoal and activated carbon are produced from pyrolyzed biomass or coal. In industry, coal or other hydrocarbons subjected to pyrolysis are carbonized to make coke for steelmaking. Pyrolysis is also used to recover energy and materials from waste plastics and tires, producing oil, gas, and char, though emissions controls are required.

Measurement and terminology. In scientific writing, material is often described as pyrolyzed to indicate the product of pyrolysis, regardless of feedstock. Related terms include pyrolyzate (the mixture of products) and pyrolysis oil. Safety and environmental considerations include tar formation and volatile organic compounds; modern processes employ gas cleanup and environmental controls.