What is Pyrolysis?

Mary McMahon
Mary McMahon

Pyrolysis is a form of decomposition which takes place in an environment with little to no oxygen which is very hot, and may also be at high pressure. This form of decomposition can occur in nature, and it can also be used in controlled environments for various purposes. Some industrial products are produced with the assistance of pyrolysis, and it is also used to produce experimental fuels and in various other applications, both experimental and commercial.

Old tires can be broken down with pyrolysis.
Old tires can be broken down with pyrolysis.

With pyrolysis, thermal decomposition occurs, with the material breaking down under the heat to produce gases, some water, and solid byproducts which can take the form of ash or char. Sometimes thick tar is produced during pyrolysis as well, depending on what is being broken down. In an example of this phenomenon in nature, lava causes thermal decomposition when it flows over vegetation. In labs and manufacturing settings, pyrolysis is often accomplished in a reactor.

The more oxygen present during thermal decomposition, the more oxidation will occur during the reaction. Thus, people may take steps to try and minimize oxygen in the environment where they are creating a pyrolysis reaction, and may even conduct the reaction in a vacuum in some cases. In other cases, the reactor will simply be solidly built with seals which are designed to keep as much oxygen out as possible, because oxidation can interfere with the process.

Pyrolysis can be used specifically to process various materials to access useful byproducts of thermal decomposition, such as pyrolysis oil, a type of synthetic fuel, and various gases which are used in industrial processes. A wide variety of materials can be broken down with this process, including products like rubber tires, which can be broken down and turned into useful byproducts with thermal decomposition instead of simply being landfilled. Thermal decomposition of other materials may also help to reduce the strain on the world's landfills.

Pyrolysis of biomass is a process of particular interest to people who are interested in developing alternative fuels. Gasification, as it is sometimes called, can be used to fuel engines without relying on petroleum-based fuels. In fact, gasification has been used historically during periods of fuel shortages. Working gasification vehicles have been built to demonstrate the potential applications of this process, with their drivers sometimes even using them as primary vehicles for transport. These drivers also like to use their vehicles for public relations, demonstrating that pyrolysis is possible and has potential by modeling it on the streets.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


I'd like to add that sometimes with chemical reactions, whether biomass pyrolysis or some other process, you get harmful byproducts. I don't know much about this particular process, but it could be that the reason pyrolysis fuel byproducts are not being mass produced at this point is because they haven't figured out a way to make them safe.


@palomino - I'm sure there are many facilities that are looking into developing products that can be powered by fuels produced with the pyrolysis process. Any new fuel technology, however, comes with all sorts of complications that must be worked out before determining whether or not it is a cost effective alternative.

If you take ethanol, for example, the technology definitely exists and it is a sustainable way to create fuel. The cost of creation, however, is so high that right now it simply isn't a feasible alternative. At least not economically. I won't argue that it is certainly better for the environment, but unless you can make the fuel affordable, as well as make the products that use the fuel affordable, consumers will not purchase it.


What I find fascinating is the fact that they have this waste pyrolysis technology available that could benefit the environment and society in all sorts of ways, and yet this is the first time I've ever heard about it.

What I mean is that if there is a way to decompose waste in a controlled environment with the byproducts being various fuels, then why aren't we seeing the development of vehicles and other devices that use these fuels? Could that not put a damper in the whole fuel crisis the world is facing right now?


Oh, neat! I've always wondered how they make those products out of old tires out of recycling. You know, like those sidewalks you see in state parks or school tracks? I always figured they put it through a shredder of some sort and then kind of melted the pieces back together to form a sheet. Who knew it was a more complex process. I wonder if they can make other things with tire pyrolysis as well, and what those products might be.

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