The pros and cons of tire recycling pyrolysis
Tire pyrolysis is an innovative and sustainable solution that treats end-of-life tires (ELTs) as a resource, not waste.
Pyrolysis involves the thermal decomposition of tires in the absence of oxygen, where the vulcanising bonds between the polymers are broken down into valuable byproducts with little negative environmental impact. Since the number of ELTs discarded annually is over one billion and growing, this is a substantial source of feedstock that has the potential to replace fossil fuels in the manufacture of several products.
Tire pyrolysis is not new, but the technology has risen in prominence due to its potential to provide circular raw materials. However, safety concerns and other difficulties are associated with the pyrolysis process.
This article analyses the pros and cons of tire recycling pyrolysis and how Contec, an industry leader, has developed a clean and safe technology that meets all sustainability and safety standards.
What are the pros of tire pyrolysis?
Tire pyrolysis can potentially reduce emissions and increase energy availability and circularity due to some key advantages, as discussed below.
Pyrolysis as renewable fuel/energy
Tire pyrolysis oil (TPO) is the most abundant product of tire pyrolysis since 85 per cent of tire components are petroleum-based.
TPO’s properties are similar to some fossil fuels, making it a highly efficient and versatile energy source. After processing and treatment, TPO can be a sustainable option for partial replacement of fossil fuels in many applications:
- As fuel for motor vehicles, diesel burners, generators, engineering machinery, etc.
- As oil for power generation and heating
- Act as feedstock for the manufacture of medium to low reinforcing virgin Carbon Black
- After distillation, TPO can be used for the production of high-value chemicals.
Renewable TPO can reduce many industries’ dependency on fossil fuels.
One of the advantages of TPO is the convenience of storing, transporting, and pumping it. Since many forms of renewable energy are challenging to store, the storage convenience increases TPO’s market appeal. Moreover, distilled TPO can be used as fuel with existing machinery without any changes, enabling immediate applications.
TPO’s 41–44 MJ/Kg calorific value is similar to diesel’s 45 MJ/Kg calorific value. After distillation and desulphurisation, TPO can be used in a TPO-diesel blend (10 per cent TPO and 90 per cent diesel).
Tire pyrolysis’ byproducts result in sustainable options for the tire industry
In addition to fuels, the tire pyrolysis process generates valuable byproducts, including Recovered Carbon Black (rCB) and steel wire. The rCB is a viable option to replace medium-grade virgin Carbon Blacks from fossil fuels. rCB has proven applications as a circular raw material in many industries, including tires, paints, coatings, inks, and rubber manufacturing.
The recovered steel is recycled without losing quality and used to manufacture steel parts for tires and other industries.
Tire pyrolysis can reduce emissions
A tire pyrolysis plant is the most environmentally responsible approach to waste tire management. Other methods of disposing of ELTs, such as incineration and landfilling, have high carbon emissions.
Tire pyrolysis efficiently converts and recovers materials and energy in waste tires and creates few carbon emissions and pollutants. It produces a renewable syngas byproduct, which can heat the pyrolysis plants, further reducing the process’s carbon footprint.
What are the cons of tire pyrolysis?
Pyrolysis of ELTs into valuable products has disadvantages, including further product processing, safety considerations, pollution concerns, and operational expenses.
These drawbacks should be carefully assessed and managed when implementing a tire pyrolysis process.
No usage as engine fuel
TPO is a heavy, dark fluid whose hydrocarbon composition depends on the pyrolysis process, conditions, and feedstock. According to Han 2023, at temperatures below 500°C, the TPO has more aliphatic hydrocarbons (isoprene and limonene) and fewer aromatic hydrocarbons. At temperatures over 500°C, the aromatic hydrocarbon content increases.
While TPO’s chemical composition is similar to crude oil, high levels of limonene and pollutants like sulphur make it unsuitable for engine fuel use. Heavy oil is only suitable for use as heating fuel. Therefore, TPO requires additional processing and distillation before it can be used as engine fuel.
TPO produced from pyrolysis can include pollutants like nitrogen, sulphur compounds, and polycyclic aromatic hydrocarbons (PAHs). Pyrolysis using higher temperatures creates more PAHs, which are known to be carcinogenic and mutagenic. Burning TPO can produce gaseous pollutants that are an environmental concern.
In large-scale use of TPO, it’s necessary to have a flue gas purification system to remove these emissions, which can increase operational costs.
Tire pyrolysis can be expensive
The overall cost of a tire pyrolysis plant is directly linked to its efficiency and the technology required to comply with environmental and safety regulations. Higher-efficiency equipment tends to be more expensive. The initial capital cost of building pyrolysis plants can be high and run into millions of euros.
The fuel choice and the need for highly skilled personnel for plant operation will also add to the costs. However, the high value of pyrolytic products is expected to make pyrolysis feasible in the long term.
Pyrolysis processes have historically suffered from safety issues. The risks associated with pyrolysis involve accidental combustion of organic material due to contact with oxygen or high temperature. Other issues are the need for precise process control, ensuring equipment integrity, and addressing inadequate safety measures to prevent explosions.
Considering the pros and cons of pyrolysis, it’s clear that its benefits outweigh the risks. It’s a proven technology expected to grow by diverting waste tires that are landfilled or incinerated.
Tire pyrolysis at Contec
Contec’s pyrolysis process and technology have made it a leader in the industry for focusing on safety and sustainability.
The plant is checked regularly before starting each run and monitors the process constantly to ensure no pressure buildup could lead to an explosion. Contec’s Molten®, a molten salt and proprietary technology, has a high heat transfer exchange, so less energy is used. The molten salts are reusable, producing no pollutants when heated.
The design of modern waste tire pyrolysis plants results in reduced environmental impact, improved economic benefits, more safety for staff, and reduced energy costs. Companies like Contec are solving the growing waste tire problem and producing innovative recycled products without negative environmental or safety concerns.
Their innovations have adapted traditional pyrolysis technology to meet current environmental, sustainability, and ethical work standards while helping industries join the circular economy. Find out more about Contec’s circular TPO, ConPyro®.
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