Globally, about 4 billion waste tires are buried or stockpiled, with approximately 1.8 billion new tires discarded each year. Through pyrolysis processing, these tires can be converted into valuable by-products—including pyrolysis carbon black (PCB). On average, every 10 kilograms of automotive tires contains roughly 3 kilograms of carbon black, resulting in a massive annual output of this material. Read on to explore how this waste tyres convert into valuable PCB.
Environmental Hazards of Tire Accumulation
Land Occupation and Visual Pollution
Discarded tires occupy extensive landfill space due to their bulk and non-biodegradable nature. Unlike organic materials, tires do not decompose easily and can persist for centuries. The piles not only reduce usable land but also create unsightly landscapes that affect urban and rural aesthetics. Large-scale tire dumps often become symbols of mismanaged industrial waste and environmental neglect.
Fire and Air Pollution Risk
Tire stockpiles are highly flammable. Once ignited, they are difficult to extinguish because of their rubber composition and internal void structure that supports smoldering combustion. Tire fires release dense black smoke, carbon monoxide, sulfur compounds, and polycyclic aromatic hydrocarbons (PAHs), which can contaminate the air and soil for years.
Breeding Ground for Disease Vectors
The hollow interiors of discarded tires easily collect rainwater, creating stagnant pools ideal for mosquito breeding. This increases the risk of vector-borne diseases such as dengue fever, malaria, and Zika virus in surrounding communities. Improperly stored tires thus become inadvertent public health threats.
Long-Term Ecological Impact
Over time, weathering and ultraviolet radiation cause the tire surface to degrade, releasing micro-rubber particles into the environment. These particles can leach heavy metals and toxic additives into soil and waterways, posing long-term risks to aquatic ecosystems and biodiversity. The cumulative ecological burden emphasizes the urgency of sustainable tire recycling and pyrolysis recovery technologies.
The Formation Process of Pyrolysis Carbon Black
Currently, pyrolysis offers an efficient and sustainable approach to waste tire management. The following section explains how tire pyrolysis carbon black is formed.
Polymer Breakdown and Volatilization
Tires comprise cross-linked rubber polymers plus various additives (carbon black, sulfur, metals, etc.). Under pyrolysis (heating in an oxygen-deficient atmosphere), the rubber matrix begins to decompose. At temperatures typically above about 400 °C, the long polymer chains undergo depolymerization (breaking into smaller fragments), dehydrogenation (loss of H₂), and pyrolysis into volatile hydrocarbons. These volatile compounds escape as gases or condense into oils; what remains is a carbon-rich char. Research shows that during high-temperature pyrolysis of waste tires, the yield of carbon black increases significantly when the temperature rises (e.g., from ~1100 °C to ~1300 °C) and residence time is sufficient.
Solid Carbon Formation and Refinement
Once the volatiles are removed, the remaining carbonaceous residue begins to restructure: small aromatic rings polymerize and condense into graphitic or quasi-graphitic domains, particles nucleate and grow, and a carbon black-like morphology emerges. The degree of graphitization, particle size, and specific surface area depend strongly on pyrolysis temperature and residence time (higher temperature and sufficient dwell time favor smaller particles and more ordered carbon). After pyrolysis, the char may be cooled under an inert atmosphere, separated from metal wires or mineral additives, and further processed (milling, activation, surface treatment) to improve its structure and remove residual volatiles or contaminants.
Characteristics of Pyrolysis Carbon Black
Microstructure and Morphology
Carbon black is composed of fine, amorphous carbon particles typically in the range of 10–100 nanometers. These particles form complex aggregates and agglomerates, creating a high surface-area network that influences its color intensity, electrical conductivity, and reinforcement capability. The degree of aggregation directly affects the performance of carbon black in industrial materials.
Surface Chemistry
The surface of carbon black contains various functional groups, including hydroxyl, carboxyl, and quinone structures. These chemical sites determine its adsorption properties and compatibility with organic and polymeric matrices. Controlled surface modification can improve dispersion and bonding strength in composite materials.
Thermal and Electrical Properties
With its high thermal stability and excellent electrical conductivity, carbon black is resistant to decomposition under elevated temperatures and serves as an efficient heat and electron conductor. Its black coloration and opacity also result from strong light absorption due to the extended π-bond network within its carbon layers.
Key Applications of Pyrolysis Carbon Black
With global carbon black production reaching around 14 million tons annually, refined pyrolysis carbon black is emerging as a sustainable alternative across multiple industries. The following are its main application sectors and their respective market shares.
Tire Manufacturing (70%)
Refined pyrolysis carbon black is primarily used in tire production, especially for medium- to low-performance tires. After post-treatment, it can meet the requirements for grades like N330, N550, and N660.
- Used in tread, sidewalls, and inner liners
- Improves abrasion resistance and heat conductivity
- Suitable for off-road, agricultural, and commercial vehicle tires
Technical Rubber Products (20%)
About 20% of PCB is applied in industrial and automotive rubber products where material strength and resilience are important but not at tire-grade levels. Common uses include:
- Conveyor belts, rubber hoses, gaskets, and molded components
- Applications requiring moderate reinforcement and dimensional stability
Plastics, Dyes, and Pigments (10%)
Roughly 10% of refined PCB is used in plastics manufacturing and pigment formulations. Although its dispersion and gloss may not match high-end pigments, it delivers acceptable performance for cost-sensitive applications.
- Applied in black masterbatches, plastic films, and containers
- Used in inks, industrial paints, and low-grade coatings
Improving the Usability of Pyrolysis Carbon Black
Pyrolysis carbon black (PCB) cannot be directly applied in most industrial fields due to its coarse particle structure, uneven distribution, and the presence of ash, oil residues, and metallic impurities. Such characteristics reduce its reinforcing performance and dispersibility, limiting its effectiveness in rubber, plastic, and pigment production. To address these limitations, Beston Group adopts a specialized post-processing system that integrates carbon black grinding and granulation.This process can achieve:
- Increases the specific surface area of carbon black, improving adsorption and reactivity.
- Promotes overall PCB quality by achieving higher purity and uniformity.
- Expands its usability and commercial value across multiple industries while supporting circular resource utilization.
Conclusion
Pyrolysis carbon black is more than just a by-product—it’s a practical, resource-saving material with growing relevance across multiple sectors. As pyrolysis technology evolves, the demand for this sustainable carbon source is likely to expand. Partner with Beston Group to improve the overall utilization efficiency of end-of-life tire resources.
