In the energy transition, diversifying power sources is often seen as a necessary step on the route to net zero. According to the International Energy Agency, if we are going to meet zero emissions by the middle of the century, then a “dramatic transformation” of our energy system is needed, and the inclusion of new energy sources is necessary.
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While renewable electricity generation shows promising growth, much existing energy infrastructure was designed for liquid or gas fuels. Industries such as shipping, construction and manufacturing still rely heavily on crude oil and natural gas. For consumers, much of our global energy infrastructure and pipelines, notably in the global south, was designed for the transportation of crude products. Decarbonising these liquid fuels provides a cheaper route to net-zero for these consumers, even if it only fills a gap on the way to renewables.
As such, some have looked into producing alternative liquid fuels from a variety of sources, from plants and organic matter to waste material. Plastic, which is originally produced using crude oil, can also be used to produce synthetic oil and gas through a process called pyrolysis.
Through pyrolysis, the plastic is heated to extremely high temperatures, between 300⁰C and 900⁰C, with a lack of oxygen. This causes it to break down into smaller molecules and transforming it into pyrolysis oil or gas. This product can then be used as a fuel or to create new, second-life plastic products.
Supporters of pyrolysis claim that it holds the answer to the dual challenge of plastic waste and excessive fossil fuel consumption. Pyrolysis company Stellar 3 has developed a “particular pyrolysis technology that is the most flexible and efficient with the highest quality outputs”, CEO Dan Nienhauser says. However, the process is not without its detractors.
An emerging technology
Plastic degradation, through pyrolysis, uses differing types of plastic, such as polyethylene or polystyrene, to produce a variety of liquid gas fuel products. Plastics can be added individually or as a mix in order to produce a diverse range of products. Differing types of catalysts are used to improve the pyrolysis process, including ZSM-5, zeolite, Y-zeolite, FCC, and MCM-41. While high temperatures are used, pyrolysis avoids incinerating its feedstock, instead reforming it into fuels.
Many pyrolysis facilities produce a liquid oil with a high heating value which resembles conventional diesel. This product can be used to power vehicles and machinery after it is refined and blended with conventional fuels. As such, fuels produced through pyrolysis could offer a lower carbon solution for hard-to-abate industries.
Stellar 3 has developed a pyrolysis process which can recycle plastics including PVC. “PVC is typically avoided because it has a chlorine in it, so we have designed, developed and built a chlorine extraction pre-pyrolysis unit. What that does is it keeps the plastic to a temperature that where the plastic is still liquid, and then the chlorine evaporates, that chlorine is captured and condensed into a 30% hydrochloric acid into a special container, and then the rest of the plastic goes through the regular pyrolysis process”.
Pyrolysis is not a form of incineration, Nienhauser adds, as when burning waste an amount of energy is lost in the process.
“You’re eliminating all the carbon footprint of taking oil out of the ground, shipping it to a refinery and then shipping it all the way to importing countries. Some of that can be replaced with a blend-ready diesel, produced locally based on the plastics that are there”.
Local energy production
For Nienhauser one of the major benefits of pyrolysis technology is that the plants are small enough to accommodate fuel production on a local level which is then transported in liquid form. Stellar 3 builds facilities which take in 30 tonnes of waste material per day, the equivalent plastic waste production of 250,000 people per day.
Alongside others globally, the company manages a processing facility located in the Philippines. “Because of the island location, one of the challenges is that you don’t have extra room for landfill. So, once it’s filled, you put extra plastic on the top of the landfill, and it rolls down into a river that ends up in an ocean. Our objective by is to have the capacity to take 500 tonnes of landfill waste per day and use it in a waste transformation facility,” Nienhauser adds.
The problem of plastic pollution
With the increased consumption and urbanisation of our society comes more plastic waste. Around 12 million tonnes of plastic makes its way into the world’s oceans every year. Environmentalists and NGOs are calling for better waste management of plastics. Currently, 9% of plastics are recycled and an additional 22% are mismanaged. Much of the plastic we used is currently either heads to landfill or the oceans.
Pyrolysis has the potential to increase the demand for second-life plastics turning them into a useful product. However, while pyrolysis offers a potential waste solution critics argue that it is not the fix-all green solution for both plastic waste and fossil fuel use.
How green is pyrolysis?
Producing a fuel from a hydrocarbon product means that when that product is burned, it will produce carbon dioxide and other greenhouse gases. As such, they can only reduce emissions from their suppliers, not their consumers. Synthetic fuels that make use of pre-existing oil and gas infrastructure could also delay the infrastructure overhaul need to transform our energy system. Detractors argue that whether it is oil and gas pipelines or vehicle engines, at some point our infrastructure and technologies will have to change.
Additionally, pyrolysis is not a perfect science. When producing a product from waste, it is difficult to ensure the exact same product every time when the input material varies. Critics say that given the variety in plastic types, in reality only a fraction of it is recycled effectively in pyrolysis.
But for Nienhauser, recycling any plastic should be counted as a positive. “When you put something into a system and you turn it into a gas, you can’t change what it is from a from a molecular structure standpoint. That said, the developing world is very excited about ways of reducing waste.”
Stellar 3 is also developing recycling facilities that handle only one type of material. “We’ve done a pilot facility looking at end-of-life tires. Frequently, there are these very large facilities where their only purpose is to shred tires. We have a new plant that, instead of taking the shredded material, takes a whole tire and puts it into a vacuum sealed environment where the rubber and petroleum-based part is melted off it. You leave the steel and the fabric on top of a sieve and then you have the liquid that proceeds into the pyrolysis chamber.”
“In addition to providing a petroleum and carbon black product that can be put back into the tire industry, and you can create around 60% of a new tire if you have the right efficiencies in your system for from an old tire. And that for us is very exciting where we start to really cut back on those raw virgin materials”.
How much energy does pyrolysis need?
Any kind of recycling requires large amounts of energy, especially when heating materials to high temperatures. However, recycling remains more energy efficient than producing a product from original materials.
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“It’s part of pyrolysis’ reputation, because there’s a lot of companies that have done it less efficiently in the past,” says Nienhauser. But pyrolytic facilities are innovating: Stellar 3, for example, burns excess synthetic gas produced from the process to produce the necessary heat. “Once it’s operational, the process needs a low level of external power which can be provided from renewables.”
For Nienhauser is “the year of chemical recycling”. “This is really a time where the circular economy starts to have economic legs, as opposed to being something that we do because we really have to. With all the climate challenges going on today, I think anything we can do, even if it’s flawed compared to what we may envisage as a perfect scenario, it’s something we should start doing as soon as possible,” he concludes.
"Till date nothing has proven to be a truly effective or environmentally responsible solution to the burgeoning global landfill problem. In fact, many existing solutions have been just the opposite: costly, energy inefficient or equally as harmful to the environment as the plastic itself. "
It is only now, that with the evolving pyrolysis technology, there is a solution that is remarkably simple, economically viable and "green" as well.
Pyrolysis is a thermochemical decomposition of organic material at elevated temperature without the participation of oxygen. In this process long polymer molecules are broken down into shorter chains of hydrocarbons with the help of heat and pressure. You can learn more about this process here: How to make oil from plastic
Some benefits of pyrolysis are that the process does not generate harmful pollutants and that the by-products can be used as fuel for running the plant. In the case of plastic, some of the valuable fuels and solvents that can be extracted through waste plastic pyrolysis are fuels like gasoline, kerosene, diesel, and high-value ones like benzene, toluene and xylene. And a kilo of waste (typically PP) can yield upto a litre of fuel whereas the incineration of the same quantity of plastic would produce 3 kilos of CO2!
This technology is growing in popularity and in demand. Commercial machines for home are still expensive. But with the following method, you can convert waste plastic to fuel all by yourself!
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Before getting down to work, first decide the scale of your setup.
Ideally, 1 kg of plastic can produce 1 kg of fuel. For getting a good yield, you can use polypropylene i.e. any plastic product with the mark PP or '5'.
The reactor that I built has a capacity of about 100g.
So while selecting the container for your reactor, keep in mind the following considerations:
I used a stainless steel vessel and clamped it with a bolted aluminum strip. Next I drilled a hole in the centre of the lid for the outlet of the fuel vapour.
Back in the reactor, the plastic is converted to vapourized fuel above 400C.
You need to convert this vapour to liquid by passing it through a condenser. Once again, it needs to be robust, heat resistant and leak-proof. I used copper pipes (used as condensate piping in A/Cs and refrigerators) but you can you aluminium or steel.
The length of the condenser may not be sufficient for the circulating water to bring the 400C vapour to room temperature. So you'll need to further bubble it into water and then seperate the floating oil from the denser water. Let me know if you come up with a smarter way for doing this!
Once you are done with the construction work, start the fascinating process of converting trash to black gold!
Here's how:
1. Collect some waste plastic items and shred them to pieces for faster and better reaction
2. Seal the shredded plastic tightly in the reactor chamber
3. Setup the equipment on your stove and turn on the inlet water flow
4. Turn on the stove, stand back, and watch the spectacle!
Initially you'll see fumes flowing out of the condenser, then drops will trickle, and finally you'll have a stream of usable oil flowing out! At the end of the reaction, when you open the chamber that was initially full, you'll be surprised to find it empty, only charred.
The trash disappears and all you are left with is usable oil of high calorific value. Light the obtained fuel and witness it burn flawlessly and for long! If you want to obtain refined usable products from this mixture, you can do so by careful fractional distillation. Although few people can extract the different product of pyrolysis, we successfully did! After successive distillations, we extracted four distinct products, which on the basis of boiling point, odour and calorific values, were concluded to be benzene, toluene and even a mixture similar to diesel!
Waste is a misplaced resource...your trashcan is a treasure chest.
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