Does the Rubber Meet the Road? Assessing the Potential of Devulcanization Technologies for the Innovation of Tire Rubber Recycling

4.1. Key Industrial Activities in the Value Chain

Collecting tires. All interviewed companies organized their supply chains to ensure a steady supply of tire rubber with the goal of providing devulcanized material with a consistent quality. Four companies made arrangements with their tire rubber suppliers to meet specific quality standards, while another four companies conducted their own processes of sorting and separating tires. Additionally, two companies separated truck and passenger car tires, one company focused on removing tires older than 10 years, and one company also separated summer and winter/all-season tires. Thus, pre-sorting was managed both through supplier agreements and in-house processing, and each company employed its own set of selection criteria.

Separating tires. Most companies that devulcanize tires used the granulate of whole tires, but in some cases, the tire rubber was first separated. Three companies purchase tread rubber from retreading companies, obtaining rubber with more uniform specifications. Additionally, a developer of devulcanization equipment introduced a new technology to scrape the treads of passenger car tires, thereby obtaining pure tread tire rubber. Devulcanizing only the tread rubber resulted in a higher quality of devulcanized material compared to rubber from whole tires.

While the majority of companies applied thermo-mechanical processes, sometimes supported by chemical devulcanization aids, the interviews also unveiled significant differences between these companies. In addition to variations in the supply of sorted and separated tire rubber, distinctions were noted in terms of the temperature employed, the use of specific chemicals or solvents, the size of the powder or granulate, and the equipment used (with extruders and autoclaves being the most common). Notably, one company employed three different devulcanization methods in a single facility to optimize processes for three distinct sources of recovered tire rubber. There were large variations in feedstock and equipment. Four respondents claimed that their technology was more sustainable than similar devulcanization technologies, citing different arguments such as the absence of chemicals, the use of non-hazardous chemicals, fully optimized equipment or a process conducted at lower temperatures. It can therefore be concluded that the diverse approaches taken in devulcanization processing activities highlight companies’ strategic customizations of these methods to align with their specific business objectives and sustainability targets.

Adding devulcanized material to compounds. The respondents mentioned that their devulcanized material was mostly compounded with rubber from primary sources to meet the specifications needed for new products. The ratio depended on the application and customer demands, but generally, 10 to 20 percent of devulcanized rubber was added to a compound. This compounding was mostly managed by tire or rubber goods manufacturers, sometimes in collaboration with recyclers. When devulcanized material was added to a rubber compound, the impact of the devulcanized material on the properties of the new compound needed to be studied.

Developing new products with recycled content. In the interviews, the respondents mentioned various applications and markets for devulcanized rubber on an industrial scale as follows:

These responses suggest that devulcanized rubber can be applied in a range of applications. However, it is not applied in the most critical applications.

4.2. Technological Innovation System Functions

Entrepreneurial activities. An opportunity for the development of industrial devulcanization processes lies in the creation of new business models that support these processes. For six of the interviewed companies, devulcanization was at the core of their business model, while others also engaged in other activities, such as the development of different technologies. Their business model was not entirely dependent on the devulcanization of tires. Among the companies reliant on devulcanization activities, four were part of a larger holding company, and the other two were startups that collaborated with other companies to organize a value chain and establish their business cases. Thus, the interviewed companies not only had different devulcanization processes but also possessed distinct business models, both in terms of activities and organizational structure.

A barrier existed for the development of industrial devulcanization processes because the quality of devulcanized material depended not only on the devulcanization process but also on other activities within the value chain. The respondents generated new knowledge on improving and scaling up industrial processes, integrating activities in the supply chain, and facilitating customers’ use of devulcanized material in new compounds. Five companies actively participated in the compounding process led by tire and rubber goods manufacturers by providing advice and conducting additional tests. In summary, a barrier exists in the need for aligning activities throughout the value chain, requiring collaborative efforts and engagements from tire and rubber goods manufacturers.

Knowledge development. An opportunity arose from the development of a significant number of novel devulcanization technologies, ranging from research and development facilities to industrial processes. All respondents worked with patented devulcanization technologies. While tire manufacturers globally held the majority of intellectual property (IP), these companies primarily relied on IP from other sources. In four cases, the devulcanization method was developed by universities that made their IP available through licensing to companies. Three companies developed their own devulcanization methods and filed for IP rights. One company developed an entirely new devulcanization method within an EU-funded project. Another company, initially not focused on devulcanizing rubber, coincidentally discovered a novel approach while experimenting with another recycling method. This diversity in the origin of intellectual property from these companies illustrates a range of innovation pathways.

The variation in devulcanization processes and the diverse sources of end-of-life tire rubber also posed a barrier because it made it challenging for manufacturers to compare the composition and quality of devulcanized rubber from different suppliers. Eight of the companies initiated their devulcanization activities within the past seven years, introducing new types of devulcanized material to the market. Each company branded its own devulcanized material and defined its own grades. The respondents noted incidents where manufacturers were unwilling to test their material because other companies had already presented a similar type of material. A tire manufacturer pointed out that it had conducted research and development on the devulcanized material of just one supplier due to the necessary research and development efforts. Thus, although many innovations occurred, this did not automatically result in a greater adoption of the technology.

Knowledge diffusion. An opportunity existed in the collaboration of various knowledge institutes, recycling companies, and suppliers of equipment and chemicals to develop industrial devulcanization processes within projects. Seven respondents had recently participated in projects to (further) develop devulcanization, funded either by the EU or national governments. These projects were mainly used to (further) develop their devulcanization technologies. The interviews revealed that the participating organizations played various roles in technology development and information sharing within these projects, including the following key roles for technology development:

A barrier was that the diffusion of knowledge often remained confined to those projects and their associated value chains. The willingness of companies to license intellectual property and share knowledge reflected a potential avenue for overcoming this obstacle for knowledge diffusion and commercial selling.

Guidance of the search. An opportunity arose as governments funded projects to stimulate the development of devulcanization. For the adoption of devulcanization, customers of devulcanized rubber had to engage in research and development activities to add devulcanized material to their compounds. In most projects, one or more launching customers participated in testing devulcanized material for their applications. These projects, with various types of organizations, led to a rapid development of new technologies and applications.

A barrier was identified because most tire and rubber goods manufacturers did not have the incentive to replace virgin rubber with devulcanized material in their products, and there was a lack of stimulating regulations. In the current situation, potential customers were mostly interested in devulcanized rubber to meet certain sustainability goals. Three respondents mentioned that there were no rules and regulations at the national or European level that stimulated manufacturers to use recycled rubber instead of virgin rubber. Two respondents advocated for national or European regulations that would require manufacturers to incorporate a percentage of recycled content into their compounds. This indicates that the existing rules and regulations do not stimulate the uptake of recycled materials, such as devulcanized rubber.

Market formation. An opportunity arose as the attention from tire manufacturers and other rubber product manufacturers increased, according to the respondents. Three respondents experienced a rise in the number of companies showing interest in purchasing devulcanized rubber in the past year. Three respondents had already supplied devulcanized material to tire manufacturers. One of these companies had already supplied rubber in large quantities, while the other companies were undergoing a preparation process to meet the demands set by manufacturers. Although the interest in devulcanized material was increasing, this did not always directly translate into higher sales.

A barrier existed as there was no established market for devulcanized rubber. Assessing devulcanized material by tire and rubber goods manufacturers was challenging due to its different properties compared to virgin rubber. Five respondents indicated that many rubber goods manufacturers were not yet inclined to use any recycled rubber. Four recycling companies stated that price negotiation for devulcanized material with rubber goods manufacturers was often difficult. As this was a new type of material, there was not yet a clear reference price. The interviewed tire manufacturer stated that the price their purchasing department was willing to pay for devulcanized material was significantly lower than the price for virgin rubber. One recycler stated that his company was forced to stop its operations because the market value of virgin rubber suddenly declined, and customers also demanded lower prices for the devulcanized material. Therefore, market development was complicated by the unfamiliarity with the material characteristics of devulcanized material on the one hand, and the volatility and often low prices of virgin rubber on the other hand.

Resource Mobilization. An opportunity presented itself when companies had access to multiple sources of income for the development of technology. The financial resources identified for the development of industrial devulcanization processes came from government funds and corporate and private investments. Most innovations in the technology were developed in subsidized projects.

For better market expansion, most companies encountered a barrier in the need for additional customers, specifically tire and rubber goods manufacturers, to scale up their production. In some cases, it took months or even years of research and development before certain customers were willing to incorporate devulcanized material into their compounds. These long lead times made it challenging for companies to generate sufficient income from their sales, primarily because extended research and development trajectories did not guarantee a confirmed market uptake.

Creation of legitimacy. An opportunity emerged as devulcanization gained recognition as a recycling approach in the industry. This was manifested not only by an increase in potential customers showing interest but also by the heightened involvement of other interested parties, such as investors. The respondents also mentioned that they could present their technology at industry conferences.

However, 10 respondents also pointed out that the acceptance of devulcanized material was also a barrier. One respondent from a recycling company mentioned the challenge of explaining the distinctiveness of devulcanized material to customers, investors and interested parties. Another respondent raised a similar issue regarding the use of devulcanized rubber as a plasticizer in asphalt, highlighting that this was a novel material for such an application.