Weibold Academy article series discusses periodically the practical developments and scientific research findings in the end-of-life tire (ELT) recycling and pyrolysis industry.

Claus Lamer
Claus Lamer

These articles are reviews by Claus Lamer – the senior pyrolysis consultant at Weibold. The reviews aim to give industry entrepreneurs, project initiators, investors, and the public a better insight into a rapidly growing circular economy. At the same time, this article series should stimulate discussion.

For completeness, we would like to emphasize that these articles are no legal advice from Weibold or the author. Please refer to the responsible authorities and specialist lawyers for legally binding statements.

Introduction

For decades, carbon black has been one of Europe’s most heavily used industrial materials—found in tires, plastics, inks, coatings, and countless engineered products. Its manufacturing has historically been dominated by a small number of global players using the well-established furnace black process. As a result, the regulatory identity of carbon black under REACH seemed fixed, stable, and largely uncontested.

But things changed when ECHA officially accepted a new substance identity for recovered carbon black (rCB). The CB4REACH Consortium, representing Europe’s major carbon black manufacturers, publicly acknowledged that ECHA approved a dedicated EC number—954-402-4—for “Amorphous carbon and silicon dioxide recovered from processing of spent tyres.” This material identity is expressly associated with rCB derived from the pyrolysis of end-of-life tyres (ELTs).

This recognition is more than bureaucratic housekeeping. It represents a regulatory milestone, signaling that Europe now views pyrolysis-derived carbon solids not merely as a variant of virgin carbon black, but as a distinct UVCB substance with its own compositional fingerprint, industrial relevance, and circular-economy significance.

Yet the acceptance of EC 954-402-4 also raises important questions: When can an rCB still be considered “carbon black” under the traditional EC 215-609-9? Does the manufacturing process matter? And what does this mean for companies navigating REACH obligations while trying to place rCB on the market?

This article explores, at a high level, how carbon black, recovered carbon black, and the REACH regulation have become intertwined.

Substance Identity in REACH: More than just a Name

REACH defines a substance not by where it comes from, nor by how it is produced, but by its intrinsic chemical identity. In principle, two materials can be made by entirely different processes yet be treated as the same substance—provided their main constituents and impurity profiles match.

Carbon black provides an elegant example of this principle. Whether it is produced in a modern furnace black plant in Europe or a thermal decomposition reactor elsewhere, if the final material consists almost entirely of elemental carbon with only trace amounts of oxygen, nitrogen, sulfur, and metals, then its identity is apparent.

But REACH also recognizes complexity. When a discrete chemical structure cannot fully describe a material’s composition, when it is variable, multi-component, and source-dependent, REACH categorizes it as a UVCB substance. UVCBs require more than a simple CAS number; their identity must also include: (1) the nature of the raw materials, (2) the type of process, and (3) the resulting compositional spectrum.

This distinction becomes crucial when comparing virgin carbon black to recovered carbon black.

Virgin Carbon Black: The Benchmark Identity

Virgin carbon black (vCB) is one of the most precisely characterized substances. The CB4REACH Consortium maintains an extensive joint REACH registration under EC 215-609-9, which effectively defines what “carbon black” is in the regulatory sense.

The consortium’s boundary composition principles can be summarized:

Virgin carbon black is essentially pure carbon, formed through the high-temperature partial combustion of heavy hydrocarbons. Its structure is a network of fused spheroidal particles—nano-sized but aggregated into larger grape-like clusters. The manufacturing process produces a material with remarkably low levels of inorganic impurities. Metals appear only at trace concentrations—mere parts per million. Ash content rarely exceeds a fraction of a percent. Organic impurities, notably polycyclic aromatic hydrocarbons (PAHs), are strictly controlled and remain at very low ppm levels.

In short, carbon black is carbon, and nearly nothing else.

This identity has been stable for decades. It forms the cornerstone of REACH compliance for all traditional carbon black manufacturers. Any material claiming this identity must be able to show—analytically—that it falls within these tight compositional boundaries.

Recovered Carbon Black: A Substance with a Past

Recovered carbon black begins life as virgin carbon black embedded in tires. But tires are not made from carbon black alone. They incorporate (besides others): (1) Silica as a reinforcement filler, (2) Zinc oxide as an activator and crosslinking agent, (3) Oils and plasticizers, (4) Steels and fibers, (5) Sulfur-based vulcanization systems.

When tires undergo pyrolysis, the polymer matrix decomposes, releasing gases and oils. What remains is a black solid, what producers call rCB, but its composition is fundamentally shaped by what the tire once contained.

Unlike virgin carbon black, rCB is not born from hydrocarbons. It is born from a product. The pyrolysis process cannot separate the original fillers from the carbon black; instead, they remain interwoven within the material.

Thus, rCB typically contains: (1) 10–20% ash, sometimes more. (2) Significant amounts of silica, often comprising the majority of the ash. (3) Zinc compounds, frequently measurable in percent levels. (4) Residual organic matter. (5) Slightly elevated sulfur content.

Its carbon content—though still high—tends to be lower than virgin grades. While vCB typically contains 96–99% carbon, rCB often contains 75–90% carbon, depending on feedstock, pyrolysis conditions, and post-treatment.

This is where the challenge arises: Can a material with 15% silica be registered as a substance that allows less than 1% ash?

Technically, yes—if the silica is truly “impurities.” Legally and practically, however, the answer becomes more nuanced.

Does the Production Process matter for REACH?

REACH is emphatic: the production process alone does not define a substance. If two materials are compositionally equivalent, they may share the same registration—even if manufactured worlds apart.

Yet, in the case of carbon black, the production process matters indirectly because it determines the composition.

The furnace black process produces a remarkably pure form of elemental carbon, with almost no inorganic residue. Pyrolysis, in contrast, inevitably produces a carbonaceous material loaded with the tire’s legacy: silica, zinc oxide, and metal traces that do not exist in furnace black.

So, while REACH doesn’t discriminate based on process, the process determines the substance.

If an rCB producer can show, through rigorous analytical evidence, that their recovered carbon black: (1) has ash levels comparable to vCB, (2) contains only ppm levels of metals, (3) and exhibits PAH levels within boundary limits, then the process becomes irrelevant, and the material may validly be registered as virgin carbon black (EC 215-609-9).

But for most rCBs on the market today, this is not the case.

ECHA’s Acceptance of EC 954-402-4: A Turning Point

The CB4REACH Consortium’s is explicit: ECHA has formally accepted a new substance identity for recovered carbon black derived from spent tires, assigning it EC number 954-402-4.

This new identity reflects a profound reality: namely, rCB is not the same substance as vCB, unless purified to the point of stripping away what makes it rCB.

EC 954-402-4 embraces the true nature of pyrolysis-derived solids: (1) It is amorphous carbon, (2) It is silicon dioxide, (3) It is other inorganic tire residues, (4) And critically: it is the product of processing spent tires.

This is precisely how UVCBs are meant to be defined, by their compositional fingerprint and their process-dependent character.

For rCB producers, the existence of EC 954-402-4 accomplishes two things:

  • It provides a legitimate, compliant route for REACH registration without trying to force-fit the material into a definition it cannot meet.
  • It reinforces the circular-economy narrative that rCB is a new, independent industrial material, one that deserves its own regulatory identity rather than being treated as a derivative or “second-class” carbon black.

When Can rCB Be Registered as Virgin Carbon Black?

There is no prohibition against registering rCB under EC 215-609-9 if the composition matches. But this is a high bar.

To co-register as virgin carbon black, an rCB producer must demonstrate convincingly that their material:

  • Contains ≥95% elemental carbon.
  • Has minimal ash—ideally <3%, and certainly below ~5–7%.
  • Shows metal impurities at ppm levels.
  • It has PAH profiles within the CB4REACH boundaries.
  • Does not introduce new hazards absent from the vCB dossier.

In practice, meeting these criteria usually requires significant post-treatment, such as:

  • Acid demineralization (sometimes multiple sequential acids).
  • High-temperature oxidation burn-off.
  • Steam activation.
  • Magnetic separation to remove steel fines.

Such processes are costly, energy-intensive, and can erode rCB’s sustainability advantage.

Nevertheless, several companies are actively developing “upgraded rCB” products approaching furnace-black purity. For them, co-registration under EC 215-609-9 is feasible and legally defensible.

For most others, however, the more appropriate pathway is EC 954-402-4.

Conclusion: Two Substances, One Regulatory Framework

Virgin carbon black and recovered carbon black share a name, a color, and many functional similarities. But under REACH, substances are defined not by appearance or performance, but by composition and identity.

Virgin carbon black (EC 215-609-9) remains one of the most precisely defined substances in industrial chemistry—nearly pure elemental carbon with minimal impurities.

Recovered carbon black, despite its origins in that same substance, becomes something different after pyrolysis: a carbon-inorganic hybrid shaped by its feedstock and manufacturing history.

ECHA’s acceptance of EC 954-402-4 acknowledges this distinction and provides the regulatory clarity the industry has long needed.

For rCB producers, the choice is now clearer than ever:

  • If your rCB matches vCB composition, you may co-register under EC 215-609-9.
  • If it does not—and most rCBs do not—the correct, future-proof pathway is EC 954-402-4.

This dual pathway system strengthens regulatory compliance, enhances market credibility, and supports Europe’s transition to a circular carbon-black economy.

In the end, REACH does not stand in the way of recovered carbon black. It simply insists that the material be named for what it truly is.

If you would like to gain deeper insights into this topic, please don't hesitate to contact the author, claus@weibold.com.