Pyrolysis of Plastics to Oil

Humans are responsible for most of the world’s pollution. In the last several decades, the Earth’s municipal solid waste (MSW) has risen to alarming levels. It should come as no surprise that plastic is one of the most commonly used and discarded materials in the world. Since 1950, production of plastic has risen every year. In 2019, 368 million metric tons of plastic was manufactured worldwide. That number is up 9 million from 2018. Plastic pollution is a clear and present danger to the world’s ecosystem.

With politicians and world leaders typically split on environmental issues, there is concern that the situation will continue to spiral out of control in the coming years.

There are viable solutions that can help us cut back on such hazardous waste. One such solution involves converting plastic waste into useable energy. Waste-to-energy plants are not a new concept. These plants have often been used as a means to convert organic material into biomass energy. Plastics provide a greater challenge, however, as they are inorganic and more difficult to bio-degrade than most other materials. However, pyrolysis is one method that can be used to convert plastic waste into useable energy, which comes in the form of oils.

What is pyrolysis?

Pyrolysis is a process used to break down waste matter by heating it without oxygen. Without air, the chemicals that make up these compounds decompose into useable gases. This allows for a process known as biomass gasification to take place, which through use of heat and steam, can convert biomass into hydrogen without the danger of combustion.

While pyrolysis isn’t a new concept, only recently are companies investing heavily into this technology. Industrial-scale reactors are being created to process the excess plastic waste around the globe. With waste pollution on the rise, pyrolysis is considered to be a viable method to reduce the world’s surplus of wasted organic and inorganic material.

Using pyrolysis on plastics yields great benefits, as the plastics are thermally broken down into a reusable crude oil, which can then be used as fuel or to create more plastic products. Though plastic recycling has risen in recent years, any positive impact on the environment has remained relatively small-scale, since the waste numbers far exceed the increased focus on recycling.

How does the pyrolysis process work?

To understand what the pyrolysis process is all about, you must understand the meaning behind the word. The term pyrolysis is derived from the Greek words “pyro,” meaning fire, and “lysis,” meaning separating. The process is most commonly used to create solid forms of carbon and ash from organic materials. While pyrolysis doesn’t react with water or oxygen, a small amount of oxidation will always occur during the process due to the difficulty of creating an environment entirely devoid of oxygen. The process occurs under pressure at temperatures that are above 430°C (800°F).

There are three different types of pyrolysis: slow, fast, and flash. While slow pyrolysis will minimize the oil produced by modifying solid material, fast and flash pyrolysis create a maximum amount of oil and gas.

The big differences between the three are the temperatures used, the residence time, and the rate of heat. Slow pyrolysis is heated at a medium-high temperature (400-500°C), a longer time of residence (5-30 minutes), and a lower heating rate (10°C).

Fast pyrolysis occurs at a slightly higher temperature (400-650°C), a much shorter residence time (0.5-2 seconds), and a higher heating rate (100°C).

Finally, flash pyrolysis is heated at an even higher temperature (700-1,000°C), with a residence time of 0.5 seconds or less, at a much higher heating rate that exceeds 500°C.

What are the major benefits of pyrolysis?

The technology for pyrolysis is simple and very cost-effective, and it also provides a large variety of feedstocks. It reduces greenhouse emissions, water pollution, and sewage sludge, and cuts back on solid waste from landfills.

From an American perspective, pyrolysis could also dramatically reduce dependence on foreign energy sources and create a plethora of jobs that could jumpstart the economy.

As time goes by, the increasing world population, consistent economic growth, and human dependence on plastic products drives the Earth toward an unsustainable living environment. Waste-management strategies must be improved; our quality of life hinges upon it. With strides being made in biomass gasification and the pyrolysis process continuing to be perfected, sustainable energy can be attained in this increasingly populated world.

Let’s give waste plastics a valuable second life.