Plastic waste-to-fuel: What it is and how it works - Marsh

Plastic is part of our daily lives — it’s hard to imagine life without it. However, only 9% of plastic is recycled, with 12% incinerated and the remaining 79% landing in our oceans and landfills, where scientists predict it will take up to 450 years to biodegrade.

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With the energy transition underway, the UK Government for the first time, in its upcoming Energy Bill, has enabled support of recycled carbon fuels, including those made from plastic waste. In this first instalment of a three-part series on plastic-to-fuel technology, we outline this new process and its challenges; future articles will examine the associated risks and how they can be mitigated.

Key ways to recycle plastics

There are several ways to recycle plastics, including:

Mechanical recycling: Plastic is crushed into granules that can then be used in another product, but its molecular structure is retained. This is a widely-used technique, but has limitations. For instance, sorting methods are not yet available at scale to differentiate food-grade plastics, which command higher prices. Plus, there are environmental health concerns relating to the release of particles during this process. Companies are currently repurposing plastics, using a variety of methods, into rugs, packaging, shoes, plastic jackets, skateboards, and construction materials.

Chemical recycling: There are currently two chemical processes for converting plastic waste to an energy carrier — pyrolysis and gasification (see figure 1). These methods break down plastic, remove any impurities, and convert it back to its chemical components. They have the potential to tackle the problem of plastic pollution while also providing an alternative source of energy.

Plastic-to-fuel process

Collection and sorting: Plastic waste is collected from sources such as households, industries, or recycling centres. It is sorted to remove any non-plastic materials, like paper or metal.

Shredding and pre-treatment: The sorted plastic waste is shredded into small pieces to increase the surface area and improve the efficiency of the subsequent processes. The shredded plastic may undergo pre-treatment processes — for example, washing or drying — to remove contaminants such as dirt or moisture.

Pyrolysis: The shredded plastic is subjected to high temperatures, typically in the range of 300°-500°C (572°-932°F), in an oxygen-free environment, a process known as pyrolysis. The plastic undergoes thermal decomposition and breaks down into simpler hydrocarbon molecules.

Vaporization and condensation: The vapors produced during pyrolysis are cooled, causing them to condense and form a liquid. This liquid consists of various hydrocarbon compounds, including impurities, which can be further refined to obtain usable fuels or chemical raw material components.

Refining: The condensed liquid is processed through further refining steps, such as fractional distillation and hydro-processing, to separate and purify the different hydrocarbon fractions. The resulting fuels can include gasoline, diesel, kerosene, or similar products.

By-product handling: Some by-products may also be generated during the process, such as char or residue. These may undergo additional treatment such as hydro-cracking, or be recycled or disposed of appropriately.

Gasification: In gasification, plastic waste reacts with a gasifying agent — such as steam, oxygen, or air — at high temperatures between 500°– °C. This process produces synthesis gas, or syngas, that can be used to produce fuel for cells that can generate electricity.

One advantage of gasification compared to pyrolysis is the greater flexibility to jointly increase the value of plastics of different composition or mixtures or plastics mixed with other feedstock.

Figure 1

Source: American Chemical Society

An alternative to fossil fuel

The fundamental molecular components of plastics consist of hydrogen and carbon. Fuels produced from plastic waste can be tailored to meet a certain need, such as fuel for industrial, aeroplane, ship, locomotive, or diesel engines, and boilers. Plastics may also be processed to harvest hydrogen — a clean fuel that when consumed in a fuel cell, produces only water. As such, they are suitable substitutes for fossil fuels.

Advantages of converting plastic waste into fuel

There is much excitement about this relatively new technology worldwide — with visions that landfills could become the oil fields of the future. Several councils in the UK have already granted planning permission for plants that will convert plastic waste into fuels (see box), with other local authorities expected to follow suit. As well as in the UK, from India to Australia, plastic-to-fuel projects are underway. The benefits of creating fuel by using this technology include:

• The fuels produced are better for the environment, as they have the properties of clean fuel, so can be burned with a lower carbon footprint than coal, oil, and natural gas.
• Replaces the need for new carbon, as existing produced carbon and hydrogen molecules are utilised.
• Reduces the amount of plastic incinerated in the UK and the carbon emissions resulting from that process.
• Prevents hard-to-recycle or non-recyclable material from ending up in a landfill and reduces export of plastic waste from the UK (see figure 2).
• The potential to develop the method to include other waste materials, including those that may not be easily recyclable, such as metal waste.
• The chemical compounds produced can be used instead of fossil fuel-based alternatives in existing production lines.
• The operational cost is relatively low once the plant is set up.
• Oil and gas production has associated methane pollution, which is a large contributor to greenhouse gases. Less new carbon should result in less hydrocarbon production losses linked to flaring, methane leaks, and CO2 emissions from the chemical processes (some of which will come from cracking the plastic itself).

Figure 2

Source: National Packaging Waste Database ()

Challenges of plastic fuels

There are a number of environmental and health considerations associated with the chemical recycling of plastics due to the release of nitrous oxides, sulphur dioxides, particulate matter, and other harmful pollutants. Oil from plastic waste has more than a 20% lower flash point in comparison to regular diesel at under 40°C, increasing the opportunity of spontaneous ignition. The feedstock is variable (the raw products used in plastics, for example, vary from country to country). The different polymers that are fed into a pyrolysis reactor break along different patterns, which can pose challenges. In particular, molecules with high degrees of branching crack more easily than linear ones, which makes process control and reactor stabilization more difficult.

Once a plastic waste-to-fuel recycling plant is built, its costs of operation are comparatively low, but setting up the new unit can be costly. Lack of incentives and proper systems for waste collection can hinder the availability of waste plastic feedstock.

Additionally, the recycling industry is concerned that plastic waste-to-fuel will undermine the economy of other waste-to-fuel processes, such as solid waste-to-fuel. There is also the argument that the use of waste-to-fuel programmes does not resolve the issue of over reliance on plastics, but just increases their usefulness for the same amount of environmental impact.

The plastic recycling industry, however, is continuously evolving, and new technologies and innovations are being explored to improve the efficiency and sustainability of plastic-to-oil processes and enhance the quality of the end product.

Future articles in the series will explore the risks associated with plastic fuels and ways to mitigate them.

For more information, please visit How to Get Fuel Oil from Waste Plastic Pyrolysis.

Bob Powell had spent more than a decade in the energy industry when he turned his attention to the problem of plastic waste. “I’m very passionate about the environment,” he says. To him, the accumulating scourge of irresponsibly discarded plastic ranks high on the list of environmental issues, “right behind global warming and drought.” In , he found what he considers a solution: a suite of technologies that uses chemicals and heat to turn plastic into oil to manufacture more plastic.

In the years since, Powell founded a “plastics renewal” company, Brightmark, Inc., whose first plant, currently in its start-up phase, has processed 2,000 tons of waste plastic at its Circularity Center in Ashley, Indiana. Using an “advanced plastics recycling” technique called pyrolysis, post-consumer plastics delivered to the Brightmark plant are subjected to intense heat in an oxygen-starved environment until their molecules shake apart, yielding a type of oil similar to plastic’s petroleum feedstock, along with some waste byproducts. Ideally, Powell says, Brightmark will sell the oil to produce new plastic, promoting true circularity in the manufacturing supply chain.

Around the world, companies are drawing up plans for pyrolysis plants, promising relief from the crushing problem of plastic pollution. Small startups and demonstration projects are joining with larger companies, including petroleum and chemical giants. Chevron Phillips was recently awarded a patent for its proprietary pyrolysis process, and ExxonMobil announced in March it was considering opening pyrolysis plants in Baton Rouge, Louisiana; Beaumont, Texas; and Joliet, Illinois. ExxonMobil already operates a pyrolysis facility in Baytown, Texas, which the company claims will recycle 500,000 tons of plastic waste annually by .

“There’s a lack of transparency about how much plastic they’re recycling” and what the end product will be used for, a critic says.

Globally, the market for advanced recycling technologies is projected to exceed $9 billion by , up from $270 million in , according to a report from Research and Markets, an industry analysis firm. That’s a 32 percent increase every one of those nine years.

Proponents of pyrolysis say it will keep plastic out of landfills, incinerators, and waterways, prevent it from choking marine life, and keep its toxic components from leaching into soil and contaminating water and air. The American Chemistry Council says that “advanced recycling reduces greenhouse gas emissions 43 percent relative to waste-to-energy incineration of plastic films made from virgin resources.”

The technology can handle the plastics that can’t be mechanically melted and remolded — those stamped with the numbers three through seven, including certain plastic films, juice pouches, and polystyrene foam take-out boxes. The pyrolysis vessel itself emits nothing — there’s no oxygen, so no combustion — although heating it with fossil fuel releases the usual greenhouse gases and other pollutants.

Opponents argue, however, that pyrolysis practitioners aren’t being entirely honest about their manufacturing outcomes. “There’s a real lack of transparency about how much plastic they’re recycling” and what their end product — pyrolysis oil — will actually be used for, says Veena Singla, a senior scientist at the Natural Resources Defense Council.

Some companies, such as LG Chem in South Korea, do have verifiable plans to process plastic items into useful hard goods. The company has partnered with the marine-waste disposal company NETSPA to turn fishnets and buoys into a substance called “aerogel,” a superlight insulation; its pyrolysis plant is scheduled to be up and running near Seoul by .

But what pyrolysis mostly does, says Singla, is make oil to be refined and then sold as fuel. An analysis by the Minderoo Foundation, an Australia-based philanthropic organization focused on the environment, calculated that of the roughly 2 million tons of advanced recycling capacity scheduled to come online over the next five years, less than half a million tons of this material will actually be recycled back into plastic goods. The rest of the output is destined to power airplanes, trucks, and other heavy transportation.

Depending on the type of plastic that enters a pyrolysis vessel and the current price of oil, turning plastics into fuel might be profitable. What it’s not, says Singla, is recycling. “The benefit of recycling comes when you return materials into the production cycle, which reduces the demand for virgin resources.” That’s what the traditional, mechanical recycling of simple polyethylene terephthalate (PETE) and high-density polyethylene (HDPE) plastic does. Making plastic goods with recycled content generates 30 to 40 percent fewer greenhouse gas emissions than making plastics from virgin resources. “Now if you’re taking plastic and burning it as fuel,” Singla says, “it’s not feeding back into plastic production. And so to keep making [new] plastic, you have to keep extracting fossil fuel.”

The data from one study suggests creating pyrolysis oil from used plastic is worse for the climate than extracting crude from the ground.

Powell says his aim is 100 percent circularity, plastic to plastic, “and we’re going to be relentless in that pursuit.” But while the market matures and prices for recycled plastic drop, he admits that as “an interim step” some pyrolysis oil could be sold as fuel. “In some emerging economy nations, there may not be a viable way to use the liquids as a feedstock to make plastics,” he says. They may be too far from manufacturing facilities for plastic manufacturing to make sense, for instance. But Powell insists even this outcome is better than leaving the 90 percent of post-consumer plastic that isn’t recycled to accumulate in the environment. “I’m sure you’ve seen the videos of places where there are just rivers of plastics flowing. If we were to pull those plastics out and turn them into fuel, is that a better environmental outcome?”

“Yes it is,” he answers himself. “You’d better believe it.”

Turning plastic into fuel would obviously help keep the petroleum-based polymer industry afloat: To some observers, that’s the point of advanced chemical recycling. “The fossil gas industry is seeking to use plastics as a way to expand their production, even as they are contributing enormously to climate chaos,” says Senator Jeff Merkley of Oregon, one of 47 U.S. Senators, all Democrats, who signed a letter objecting to the EPA’s proposal to regulate pyrolysis and gasification as manufacturing instead of incineration, which is more tightly regulated. Merkley has also questioned the EPA’s inclusion of plastic-based fuel as a “waste-based” fuel under the Renewable Fuel Standard, a federal program that requires transportation fuel sold in the U.S. to contain a varying percentage of renewable fuels to reduce greenhouse gas emissions.

Fuel made from plastic does not meet the basic criteria for biofuels or renewable fuels, says Taylor Uekert, a researcher at the National Renewable Energy Laboratory (NREL), in Golden, Colorado, and lead author of a study on plastics recycling methods. “Plastic is not an infinitely renewable resource,” Uekert says. Nor is plastic-based fuel a win for the climate. “If you’re turning plastic back into oil for fuel,” she says, “you need to be comparing it to the environmental impacts of creating that fuel from fossil sources.”

NREL researchers have begun collecting data from patent applications that compare the energy it takes to produce pyrolysis oil with the energy that burning that oil can generate. So far, the data suggests that creating pyrolysis oil from used plastic, including the energy required to superheat the vessel, is worse for the climate than extracting new crude from the ground.

“In general, you’re getting higher greenhouse gas emissions from pyrolysis than you would from conventional drilling,” Uekert says. And you can’t just turn around and add pure pyrolysis oil to your gas tank. It needs to be refined. That refining process is where the most serious consequence of plastic-to-fuel comes in, impacting the people who live near refineries — most of them Black, Brown, or low-income — with another set of toxic emissions.

A Mississippi citizens’ group is suing the EPA for approving plastic-based fuel production at a Chevron refinery.

Reporting in ProPublica uncovered data from the U.S. Environmental Protection Agency that showed long-term exposure to emissions associated with the production of jet fuel from plastic-based oil carries a one-in-four lifetime cancer risk. “That kind of risk is obscene,” Linda Birnbaum, former head of the National Institute of Environmental Health Sciences, told ProPublica. Nevertheless, the EPA has authorized production of this “new chemical” at a Chevron refinery in Pascagoula, Mississippi, without revealing the proprietary substance’s name.

Chevron’s refinery isn’t the only facility turning pyrolysis oil into transportation fuels, notes Katherine O’Brien, a senior attorney with the Toxic Exposure and Health Program at the environmental law firm Earthjustice. “We’re aware of other facilities in other parts of the country that have also indicated that they’re refining or producing fuel products from pyrolysis oils,” she says. But it’s difficult to understand the scope of the problem, or even which particular communities are at risk, “because of the profound lack of transparency from the EPA in the process for approving these new chemicals.” Earthjustice is currently representing a Mississippi citizens’ group suing the EPA for approving, under the Toxic Substances Control Act, the Chevron refinery’s plastic-based fuel production. Says O’Brien, “We intend to challenge the EPA’s lack of transparency as a legal violation in that case.”

Alexis Goldsmith, an organizer with the nonprofit Beyond Plastics, says that pyrolysis and its analogs, which she calls “false recycling,” have another drawback: “They take away political will from waste reduction,” she says, potentially dissuading lawmakers from passing plastic bag bans and other legislation that might reduce the amount of plastic in circulation. Instead, some state governments are welcoming pyrolysis and gasification of plastic as a solution to plastic waste, obviating the need to reduce polymer use in the consumer and business sectors. As of this April, 24 states, including Indiana, where Brightmark’s Circularity Center is located, have passed laws classifying pyrolysis and gasification as manufacturing instead of incineration or solid waste disposal, clearing the way for the plants to operate under lighter regulation and sometimes with government incentives for job creation.

Goldsmith thinks it’s the wrong idea altogether. “We can’t recycle our way out of the plastic-waste crisis,” she says, either by mechanical or chemical means. “We need to require the world’s biggest plastic polluters to reduce the amount of plastic that they’re pumping into the market in the first place.”

So what to do with the hundreds of millions of tons of polymers already circulating in the environment, consumer sector, and waste stream? “Contain it,” she says, “just like we do with nuclear waste. Better to contain it in a landfill than burn it.”

Correction, June 5, : An earlier version of this story incorrectly identified a senior attorney with Earthjustice. She is Katherine O’Brien, not Kathleen O’Brien.

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