Microwaves could be the future for plastic recycling

A Quebec-based engineer is using microwave technology to recycle plastic waste. Could his approach help cut down on the production of new plastic?

March 11th 2021
Jocelyn Doucet is honest about his technology's limitations, saying it is only one tool to end the plastic crisis, not a panacea. Photo provided by Pyrowave

It’s been almost a decade since Jocelyn Doucet first experimented with recycling plastic waste in a microwave.

Now he says the technology derived from those early efforts will make it possible to produce plastic almost exclusively from recycled materials.

“We’re consuming more and more plastics,” says the Quebec-based engineer and founder of Pyrowave, a company pioneering microwave-based plastic recycling technology. “Yet there are not that many solutions to address the end-of-life problem, and this is what we’re proposing.”

The technology is so promising it has caught the attention of French tire giant Michelin. Last year, the company announced a partnership with Pyrowave to build a microwave recycling system for tires. It will be the first time Doucet's technology is used on a commercial scale.

Most recycling in Canada today is mechanical, where plastics are shredded before being melted down to make new, usually lower-quality, products. For the process to be viable, the stream of plastics entering the processing facility needs to be clean and well sorted, which poses huge logistical challenges. Pyrowave’s technology then uses high-powered microwaves to break clean polystyrene — a common plastic used to make everything from yogurt cups to keyboards — into molecular components, or monomers, that manufacturers can use to create entirely new polystyrene plastic.

Simple as it sounds, the approach is novel. Few researchers had successfully used microwaves to break plastic into its constituent parts until Doucet, who has a PhD in chemical engineering from the Polytechnique de Montréal, took up the challenge with a team in 2009.

Jocelyn Doucet says his microwave recycling technology — a novel approach to recycling plastic waste — could play a key role in moving Canada towards a circular economy for plastics. Photo provided by Pyrowave

At the time, he was working on food waste technologies and wanted a new challenge. “We started getting approached for plastic waste,” he says. Plastic recycling was something new.

He wondered if pyrolysis could be used in the recycling process. Pyrolysis is a chemical process that burns carbon-based materials like wood or plastic without oxygen to remove the material's hydrogen and oxygen molecules, leaving nothing but carbon. It’s ancient — Egyptians used pyrolysis to make charcoal.

Doucet thought a modified version could be used to recycle plastic.

“Very quickly, we fell on a microwave unit in the lab and started playing with microwaves,” he said. They found high-powered microwaves worked — an exciting discovery for the environmentally minded team.

Doucet’s microwave process uses electric energy instead of heat, dramatically reducing the amount of energy and greenhouse gas emissions (GHG) needed to produce polystyrene plastic, he says. According to a forthcoming life cycle assessment by Pyrowave, producing polystyrene using microwave pyrolysis recycling is 40 per cent more energy efficient than virgin oil production, Doucet adds.

Observers are reserving judgment.

"Pyrowave's technology might play a role in terms of displacing the production of virgin plastic and materials, but until we have more transparent and verifiable data on the yields, environmental and climate impact, we need a cautionary approach," says Shanar Tabrizi, chemical recycling and plastics-to-fuel policy officer for Zero Waste Europe.

Pyrowave's technology transforms polystyrene, a common plastic used in everything from fridges to food packaging, into molecular components that can easily be used to make new plastic products. Photo provided by Pyrowave

Those potential impacts are broad, from the energy required to collect, sort and clean plastic waste before the recycling process to managing the toxic residues created by plastic additives. She also noted life-cycle assessments can be misleading, depending on their methodologies.

"It's hard to assess (Pyrowave's) claims and see whether there might be significant pollutants released in the process," says Richard Heinberg, senior fellow at the Post Carbon Institute. "In general, anything we can do to recycle plastic in more environmentally friendly ways helps, but reducing the scale of production and consumption is even better."

Maximizing the environmental potential of Doucet's technology demands a wholesale restructuring of how we produce and dispose of plastics, the Quebec researcher said. New facilities that use microwave pyrolysis to manufacture plastic will need to be built. And as long as the price of virgin-oil plastic remains low, recycled plastic can't compete. It will take government regulations mandating that new plastic products contain mostly recycled materials to make the switch, Doucet said.

This is the opportunity to completely rethink.

Jocelyn Doucet, founder of Pyrowave

He compared microwave pyrolysis recycling and virgin-oil plastic manufacturing to the difference between steam and electric trains. As electricity became widespread, train engineers quickly realized it was more efficient to build entire rail systems based on high-speed electric trains than it was to replace coal with electric heating coils in steam train boilers. The new technology pushed a wholesale shift in how rail systems worked.

“This is the opportunity to completely rethink,” Doucet says.

The petrochemical and oil and gas industries so far show no signs of slowing down.

Virgin-oil plastic factories have been integrated into oil and gas infrastructure like refineries and pipelines for decades — investments that industry is loath to abandon. The sector is betting on continued plastic production to stay afloat as the world transitions away from fossil fuels, with plastic manufacturing anticipated to fuel between 45 per cent and 95 per cent of the sector’s future growth. Fossil fuel and petrochemical companies are even spending $509 billion more worldwide to expand their facilities by 2024, according to a September 2020 report by the Carbon Tracker Initiative.

Ineos and Braskem oil facilities in La Porte, Texas. Virgin-oil plastic factories have been integrated into oil and gas infrastructure like refineries and pipelines for decades. Photo by Aaron Sprecher / Greenpeace

That has environmentalists concerned. While recycling — including microwave pyrolysis recycling — can be part of the solution, it can't be used to justify current levels of production and plastic use, said Laura Yates, lead plastics campaigner at Greenpeace Canada. The organization has been leading efforts for greater government regulations to decrease overall plastic production and implement stringent recycling requirements in Canada.

In particular, Yates is concerned about efforts by the plastics industry to convert plastic waste into vehicle fuel. That will continue to stimulate virgin-oil plastic production and fail to reduce overall GHG emissions, Yates said.

Still, there are glimmers of hope. Virgin-oil plastic production decreased by four per cent in 2020, and the trend is expected to continue in the coming decades, according to the Carbon Tracker Initiative. That shift is driven by more stringent rules in China and Europe mandating that plastic products be made primarily from recycled materials. They have also started to make recycled plastic economically competitive in those markets, Doucet said.

As well as the shift in Europe, the federal government is currently drafting new plastics regulations that could see similar policies implemented here, despite intense pushback from the plastics industry on key parts of the planned regulations. Doucet is hopeful that if the new rules are implemented, they will help make plastic recycling — including microwave pyrolysis recycling — commercially viable in Canada.

Doucet is honest about his technology's limitations. It is only one tool to end the plastic crisis, not a panacea. Reducing how much plastic we use and ensuring what gets produced gets recycled more efficiently remain essential.

First of all, Pyrolysis does not burn materials without oxygen, it heats them without it, to undo other chemical processes. Second, there is a lot of vagueness around "using electricity instead of heat." The electricity is already being converted to microwaves, which usually generate heat - are they breaking chemical bonds directly here? Third, I don't see anything at all about how this process handles contaminants, the usual problem with recycled plastic. Fourth, we didn't put electric resistance heaters into steam engines because there were already better electric motors, and these are usually being turned by on-board diesel engines and generators. I smell a mess of red herrings here.

The steam engine operated by coal-fired steam pressure applied directly to a piston and drive rod assembly, which in turn was connected to the drive wheels. It was a leap forward from there to diesel-electric locomotives. Today, it would be a leap in both directions (forward with digital electrical engineering and high-speed rail technology, and backward to basic electric motor design) to pure electric drive.

I am old enough to remember the steam engines chugging and blowing their high-pitched whistles on the CPR mainline through my childhood Prairie town, steam mixed with black coal smoke, great clouds billowing high aloft on bitterly cold winter days. Today it's a disappointment to see diesel freight trains and no advancement whatsoever in rail for three generations, especially with modern electric passenger service. Canada remains lodged in the 1960s with respect to rail.

Some firms promote the use of dimension "lumber" in the construction trades made from plastic waste that is simply heated and formed under pressure into 2x4s, 2x6s and so on. They do not rot and are stronger than traditional lumber, ideal for ground-contact situations or as sill plates bolted onto concrete foundation walls and slabs. They accommodate screws, bolts and drilled holes. This use is large enough to potentially divert noticeable streams of plastic waste from the landfills, but too small and expensive to prevent a large scale displacement of wood in residential construction.

Perhaps that is a good thing, as wood is a renewable resource if managed well, and engineered wood products dramatically lower the volume of waste wood going to landfills, add value and increase productivity in lumber mills. Today, they are building residential towers from engineered wood. Cross-laminated timber columns and floor slabs enabled the construction of a 23-storey student housing building on the UBC campus, designed by the architect Michael Green who specializes in mass timber design.

The majority of forest products come from public forests on crown land, and their management is subject to the policies of publicly elected officials. That model has been a failure in too many jurisdictions like BC, where old growth stands are down to the nub and high-grading has wreaked environmental destruction on steep slopes and riparian areas that should never have been logged. The same model has been applied to Canada's petro industries. Plastics that are derived from oil and gas come from publicly-owned resources that have also been poorly managed, mostly through industry control over the resource through the private political funding of provincial governments. That has been an enormously profitable investment strategy for industry in both forests and fossil fuels. They have even succeeded in mostly passing the external environmental costs of their activity to the public.

There are probably only three ways to change that: replace the management model; dilute or eliminate private money in politics; and displace the source material. In forestry, a Community Forest Trust structure could be enacted where local government (towns and regional districts) are given control over the forest resource under defined conservation principles where continuous canopy cover and ongoing silvicultural research on climate-resiliency are practiced by a dedicated department, not unlike a local engineering or parks department overseen by an elected council or board.

This principle would be harder to realize for oil and gas, which needs to be increasingly eliminated sector-by-sector from the world economy. However, the replacement of petro fuels is well underway with electrification in both land transportation and building energy, and the international policy motivation to continue on this course is getting stronger. There is also an increasing awareness that overconsumption of plastics needs to be addressed through policy, along with the replacement of some plastics with biodegradable materials made from corn starch, paper and other substances. It's a no brainer that this effort has to be given more emphasis.

Perhaps purely local control over resources might not be a really good idea, given that residents of any community would be exceedingly loathe to stop cutting down trees before they're all gone, simply because resource extraction towns tend to protect what they see as their way of life: in my hometown, for instance, where 3-5 generations have earned a living in the same industry. There is an idea that "indigenous people" are automatically on the side of forest conservation and all kinds of environmentally friendly changes. But in some communities, First Nations people have been working in the forest harvesting industries since the late 50s or early 60s. When a shift closes down at sawmill operations, workers look for jobs in, say, mining, or construction associated with resource extraction.
Populations of towns rise and fall, and with them, the lot of other businesses that grew to serve the increasing population rises and falls with the population.
The prospect of Just Transition has to deal also with a lot of older workers who'll be displaced, workers who don't have much education (can't do college courses), and workers who can't afford to move.
They mjustn't be left behind. But they can't be expected, either, at 50-60 years old, to go back to hs, so they can retrain.