Methods to the madness: Smithers pins 4 processes for sustainable carbon black

AKRON—The carbon black industry, which sees about 94 percent of its global demand from tire and non-tire rubber manufacturing companies, has yet to reach true, commercially viable, more sustainable production methods.

That is, outside of recovered carbon black, which is the only process that has reached an industrialized scale.

But even that method has a ways to go.

As it stands today, less than 1 percent of all carbon black material used globally in new tire production comes from recycled, end-of-life tires, due primarily to a weak supply pipeline for the recovery and reuse of the critical performance additive.

And keeping the price point viable for the consumer, with all of the often costly upstream sustainability efforts, remains one of the major hurdles for tire manufacturers attempting to be net zero by 2050.

"Experts in the market believe sustainability by itself will never advance to a critical scale," Janine Young, commissioning editor for the information division of Smithers, told Rubber News. "They emphasize it must be partnered with cost reduction and performance to deliver on the 2050 sustainability goals established by the tire industry."

As an industry that currently relies almost exclusively on petroleum feedstocks and energy-intensive furnace black processing, this poses a major challenge for carbon black suppliers over the next 20 years.

But through innovation and partnerships, the carbon black industry is getting closer, according to Smithers.

The United Kingdom and Akron-based testing and consulting company recently released "The Impact of Sustainability on Carbon Black to 2041," authored by industry expert Martin von Wolfersdorff.

The comprehensive report, available through Smithers for $6,075, pins down the four most likely, more sustainable carbon black production methods (outside of the legacy furnace black processes) moving forward.

They include methane pyrolysis, recovered carbon black, renewable carbon black and circular carbon black.

Combined, Smithers estimates that, by 2041, these methods will contribute 1.98 million tons to the global supply of carbon blacks, the equivalent of around 20 conventional carbon black furnace lines.

"Sustainable solutions for producing carbon black will evolve over the next two decades, meeting the competing demands of lowering costs and improving the quality of blacks produced," Young said.

And as tire manufacturers and carbon capture tech companies coalesce around goals to produce tires with an increasingly higher percentage of sustainable ingredients, the upstream CB production methods defined in Smithers' new study are gaining attention.

"All four methods have a role to play in the way we design tires and compounds today," said Bill Niaura, director of sustainable materials for Bridgestone Americas Inc. "There are a host of different carbon blacks in different parts of a tire, and having the correct, specified grade is non-negotiable.

"In that space, particularly with recovered carbon black, we need that room to maneuver in the marketplace."

Adoption of any of the methods, singularly or in concert with one another, will increase the array of greener material options available in multiple segments.

Smithers' data shows that the tire industry's global demand for CB will reach 13.9 million metric tons in 2022, making tire production the leading end-use market. It will account for 74 percent of overall volume.

Non-tire rubber products come in a distant second at about 20 percent of the global demand for CB, according to Young.

Orion Engineered Carbons, Bolder Industries, Monolith, Birla Carbon and Cabot Corp. are some of the major carbon black suppliers who produce sustainable CB at some readiness level between pilot programs and industrial production.

And there are a number of startups or younger carbon capture companies with which tire makers have formed prosperous partnerships, including LanzaTech with Bridgestone and Enviro with Michelin.

Enviro's technology, which produces new, high-quality reusable materials like carbon black, pyrolysis oil, gas and steel, will enable everything in an end-of-life tire to be recovered for reuse, according to Russell Shepherd, technical communications director for Michelin North America.

"Michelin has begun construction on its first tire recycling plant in collaboration with Enviro, a Swedish company that has developed a patented technology to recover carbon black, oil, steel and gas from ELTs," Shepherd told Rubber News. "The new-generation recycling plant will support the circular economy with innovative recycling processes.

"Scrap tires will be collected directly from customer premises, then transported to the plant to be cut up and recycled."

In November, Michelin and Bridgestone jointly announced an expected demand for up to 1 million tons of rCB by 2030.

Enviro achieved its sustainability certification from ISCC in the fall of 2022 for both recovered carbon black and tire pyrolysis oil. It became the first organization in the world to certify its carbon black according to ISCC EU and ISCC Plus requirements.

Standard furnace carbon blacks and their production from fossil feedstocks are in conflict with tire producers that have defined objectives for recycled and biobased content in their products, according to the Smithers report.

"The resulting higher interest in alternative fillers as replacement for furnace carbons is covered in this report," Wolfersdorff writes.

As such, the four defined, more sustainable methods also have their "demerits," Bridgestone's Niaura said, including technical processing limitations and cost.

"(Tire pyrolysis) is probably the most attractive for us as it solves the ELT problem," he said. "But it comes with some demerits. If you pyrolyze a pile of tires, (the rCB) can't be recovered perfectly. It is mixed and representative of that particular pile of tires, but a non-virgin quality material—and its use is therefore limited."

And it is one reason why so little rCB finds its way into new tires.

Young said the main path to sustainability in carbon black production involves methane pyrolysis, which has a demonstration line already in position in Nebraska with Monolith.

The production process uses a plasma arc reactor to form the CB during methane decomposition. An important secondary product that forms is turquoise, or sustainable, hydrogen.

Methane pyrolysis has produced CBs that can replace semi-reinforcing carbon blacks, Young said. The technology is at the "demonstration and engineering" level and not yet fully industrialized, which is expected in 2025-26, according to the Smithers report.

"The key requirement for this process beyond scale-up is for refinements to allow methane pyrolysis to produce harder, more durable carbon black grades," Young said.

Drawbacks to methane pyrolysis, until production plants can use biomethane feedstock or some form of green power by which the plant can be powered, is that the overall sustainability is only "incrementally better" than furnace black production, Young said.

As mentioned, rCB via tire pyrolysis is the go-to method for tire majors. Recovered carbon black is essentially the solid carbon residue from tire pyrolysis.

Recovered CBs are "100-percent recycled" and maintain a significantly better carbon footprint than furnace black methods. They have been refined into viable alternatives for semi-reinforcing CBs, including N700, N600 and N500 grades.

"It can be up to 85 percent less carbon-intensive than furnace black to manufacture, and does not require direct petroleum inputs," according to Young. "Recovery and preparation of rCB requires thermal processing, meaning it will never be fully carbon neutral, however."

About 65 percent of tire makers cite rCB as the "best material to achieve sustainability goals," according to the Smithers report.

It also is the method that most sustainable CB suppliers are adopting, including Black Bear Carbon B.V., Bolder Industries, Circtec Group, Elysium Nordic, Kal Tire and Scandinavian Enviro Systems A.B., among many others.

Renewable carbon blacks are produced using a standard furnace black production line, but use biobased, renewable feedstocks, like wood (rather than fossil fuels).

"Renewable CBs can produce a conventional range of harder blacks," Young said, adding that commercial supply has now begun with one manufacturer.

While every furnace CB grade can be produced by renewable CBs, feedstock availability, yield and cost are major issues for this production avenue, Smithers said.

"The major flaw with this approach is cost," Smithers said. "Prices five to 10 times those of conventional carbon blacks make this an unrealistic option for the mass market."

Finally, circular CBs also are produced using furnace methods, but with circular, recycled feedstocks like tire pyrolysis oil (as opposed to renewable feedstocks, like wood).

The circular CBs are considered the "halfway point between renewable and standard furnace blacks," Smithers said.

"Unlike rCB processing, this requires the intermediate step of having the used tires or polymers rendered down into pyrolysis oils first," Young said. "Circular carbon black still produces carbon emissions, but energy use is much lower than for conventional carbon black furnace processes."

The cost of circular CBs—still at the pilot production level—is expected to be about double that of furnace blacks, according to Smithers.

Niaura said Bridgestone is interested in tire pyrolysis oil (from ELTs) for its circularity, but cautioned that tire makers are not the only companies vying for the scarce material.

"You can do chemistry on a benchtop and do some cool stuff," Niaura said. "But working at-scale is a separate challenge. Cost is an issue, as renewable oils are scarce and inherently expensive, either because of process or competition.

"Keep in mind we are in competition with other industries—like food packaging—for the material as well, industries that are very different, with very different price margins than tires. But we are optimistic this can happen."

Tire makers are looking at all of these methods with greater interest as more sustainable processes for carbon black production.

And while two of the four methods (circular CB and methane pyrolysis) identified by Smithers still will rely on petroleum-based feedstocks to generate energy, all have the potential to greatly reduce the energy consumption that has come to be expected from legacy furnace blacks.

"The solution must also fix the end-of-life-tire and circularity problem with current and emerging technologies being used to their full potential," Young said. "There must be no trade-off of existing technologies for emerging technologies in a vacuum.

"If there is a large cost or performance penalty, sustainability will not advance. For example, consumers will not accept a $250 tire that is all sustainable or one with poor fuel economy."

Use of carbon black as a reinforcement in non-tire rubber goods—primarily mechanical rubber goods such as hoses, belts, extruded and molded goods, antivibration components, rollers, and roofing—accounts for another 20 percent of demand, putting the market's overall reliance on rubber applications at 94 percent.

Young added that the remaining 6 percent of carbon black demand consists of specialty blacks, which primarily are used in plastics compounding or as a pigment in printing inks and paints and coatings.

"By 2050, major tire producers are aiming for carbon neutrality, 100-percent sustainable tires ... and recycled content of between 30 and 60 percent in tires," Young said. "Intermediate targets for 2030 are around 40 to 60 percent sustainable tires with about 20 percent recycled materials."

In the short term, some tire makers have identified and met a goal of 3 percent for recycled content in tires by 2025, with carbon black being a key area of focus.

Through other industry partnerships, including the Tire Industry Project, a voluntary CEO initiative of 10 companies under the World Business Council for Sustainable Development, the industry is anticipating the human health and environmental impacts of tires through their lifecycle.

The members of TIP have launched a roadmap to accelerate tire value-chain impact on the United Nations Sustainable Development Goals.

TIP members include Bridgestone, Continental, Goodyear, Hankook Tire, Kumho Tire, Michelin, Pirelli, Sumitomo Rubber, Toyo Tires and Yokohama.

Niaura added that he is proud of the work Bridgestone and Michelin have done in the sustainable CB space, as the two companies presented a position paper on the topic at Smithers' recent conference on rCB, which took place in November in Berlin.

"The joint work we have done with Michelin ... we believe in this," Niaura said. "And we want it to succeed. We want to be customers and not necessarily investors in this space.

"But a lot of these companies (engaging in sustainable CB production) are startups. This is not a farmer's market where the tomatoes are seasonal. We need tomatoes—and the correct grade of tomatoes—all year long. We need to have our tomatoes delivered on time and in reasonable ways."

Shepherd said Michelin, at least initially, will look to use rCB "to increase the short loop, from tire to tire."

"However, we could also use it as we manufacture other products, such as conveyor belts," he said. "Michelin is making progress toward its sustainability goals thanks to a greater use of natural rubber, along with recycled carbon black, oils such as sunflower oil and bio-sourced resins, silica from rice husks and even recycled steel."

While a 100-percent sustainable tire is the goal, the upstream hurdles are many, as evidenced by the challenges faced by the carbon black industry in the next 20 years.