Tyre-Derived Fuel: Pros, Cons, and How It Compares to Other Options

By:     Conor Murphy

What Tyre-Derived Fuel Is and Where It Fits in the Tyre Hierarchy

Tyre-derived fuel (TDF) is the product of processing scrap tyres for use as a fuel material in industrial energy applications. The term covers both whole tyres used directly as fuel in specifically designed facilities and processed tyre material (shredded chips or baled material) used as a fuel component in industrial combustion processes such as cement kilns, pulp and paper mill boilers, and dedicated waste-to-energy facilities.

Tyre rubber has a calorific value of approximately 32 to 35 MJ/kg, comparable to coal (approximately 29 MJ/kg for steam coal) and significantly higher than municipal solid waste (approximately 9 to 14 MJ/kg). This high energy content makes tyres an attractive supplementary fuel for energy-intensive industrial processes, and TDF has been used commercially in cement production for several decades.

The position of TDF in the UK waste hierarchy is recovery, the fourth level below prevention, reuse, and recycling. Material recycling routes such as crumb rubber production and civil engineering baling rank above energy recovery in the hierarchy; TDF is the appropriate route for tyres that cannot be directed to higher-value uses rather than a first-choice destination for all tyres. Understanding where TDF fits, and where it doesn’t, is essential context for any tyre processor or tyre generator making disposal decisions.

Gradeall International manufactures tyre processing equipment that prepares tyres for all end-of-life routes, including the front-end sidewall cutting and shredding preparation that TDF applications may require. The tyre recycling equipment range from Gradeall’s Dungannon, Northern Ireland facility supports the full tyre processing chain. With nearly 40 years of manufacturing experience and equipment in over 100 countries, Gradeall provides technical context on TDF as part of a broader understanding of the tyre processing options.

How Tyre-Derived Fuel Is Produced and Used

Preparation for TDF use. Different TDF applications require different levels of tyre processing. The options range from minimal processing to significant size reduction:

Whole tyres are accepted directly by some cement kilns designed to receive them. The tyre is fed through a port in the kiln at the inlet end and combusted in the high-temperature zone. The steel belts and bead wires are incorporated into the cement clinker, the ash from the rubber is absorbed into the clinker chemistry, and the energy content contributes to kiln heating. This is the simplest preparation route from a processing perspective.

Tyre-derived chips (TDC) are produced by primary shredding of whole or pre-processed tyres into 25 to 50mm chips. TDC can be used in boilers designed to accept solid refuse-derived fuel and in some cement kiln arrangements where the chip format is preferred over whole tyres. The shredding step requires energy input but produces a more consistent fuel specification and allows feeding into systems that cannot accept whole tyres.

Tyre bales from the PAS 108 baling process can also be used as a fuel at the end of their civil engineering service life, but this is a secondary use of the bale rather than a primary TDF production route.

Cement kiln co-processing. The cement industry is the largest user of TDF globally and in the UK. Cement kilns operate at temperatures of 1,400 to 1,500°C in the sintering zone, well above the temperatures needed to combust rubber completely. The kiln’s high temperature and long residence time ensure complete combustion of the rubber, with no unburned carbon in the output. The steel from the tyre is absorbed into the calcium silicate chemistry of the cement clinker rather than leaving as ash or slag, which means TDF in cement kilns produces no solid residue beyond what is incorporated into the cement product. This makes cement kilns an environmentally efficient TDF application: the fuel energy is recovered, the rubber carbon is combusted completely, and the steel becomes part of the product.

UK cement manufacturers including those operating in England and Wales have used TDF as a coal substitute for decades under environmental permits from the Environment Agency. The substitution rate varies by facility; some kilns operate with TDF providing a meaningful proportion of their total thermal energy requirement.

Dedicated energy from waste (EfW) facilities. Purpose-built facilities that combust tyres or tyre-derived chips to generate heat and electricity exist in the UK and Europe. These facilities operate under strict emissions permits covering particulate matter, sulphur dioxide, nitrogen oxides, dioxins, and heavy metals. Modern EfW facilities with appropriate abatement equipment can meet stringent emissions standards. The energy recovered can contribute to grid electricity supply or district heating systems.

Pulp and paper industry. Some pulp and paper mills use TDF chips in their boilers as a supplementary fuel. The mill boiler is modified or designed to accept the chip fuel alongside conventional fuel oil or gas. This application is less common in the UK than cement kiln use but is a significant TDF outlet in some international markets.

The Environmental Profile of TDF

TDF has a more complex environmental profile than either material recycling or landfill diversion, and the profile is application-specific.

Emissions from TDF combustion. Tyre rubber contains sulphur (from the vulcanisation process), zinc (from zinc oxide used as a vulcanisation activator), and various processing chemicals. Combustion of tyre rubber produces sulphur dioxide and zinc oxide in the flue gas alongside the standard combustion products of carbon dioxide, water, and nitrogen oxides. In well-controlled combustion systems with appropriate abatement, these emissions are managed to within permitted limits. In poorly controlled or uncontrolled combustion, they represent a genuine environmental hazard: this is why burning tyres is illegal outside permitted industrial processes and why tyre fires at storage sites are treated as serious environmental incidents.

Carbon balance. The rubber compound in tyres is approximately 60 to 65 percent carbon by mass. When combusted, this carbon is released as CO2. The carbon in natural rubber has biogenic origins (it came from CO2 fixed by rubber trees), and accounting frameworks treat biogenic carbon differently from fossil carbon. Synthetic rubber (styrene-butadiene rubber, the other major tyre rubber component) is derived from petroleum and its combustion releases fossil CO2. The carbon balance of TDF is therefore a blend of biogenic and fossil carbon release, with the exact ratio depending on the natural/synthetic rubber proportion of the specific tyre compound.

Compared to coal. TDF is frequently presented as a sustainable alternative to coal in cement kilns, and the comparison has merit: the fossil carbon component of TDF is lower than coal’s fossil carbon per unit of energy delivered, and the biogenic component is carbon-neutral on a lifecycle basis. Cement industry sustainability reporting typically presents TDF as a positive contribution to their coal substitution and decarbonisation programmes.

Waste hierarchy position. From a regulatory and policy perspective, energy recovery ranks below material recycling. A tyre that is shredded to crumb rubber for use in road surfacing is considered environmentally preferable to the same tyre being shredded to TDF chips for combustion, because material recycling retains the material’s embodied energy and carbon rather than releasing it in combustion. TDF is the right route for tyres that cannot economically reach a material recycling outlet, not a substitutable alternative to crumb rubber production.

TDF Compared to Material Recycling Routes

The comparison between TDF and material recycling routes (crumb rubber, civil engineering baling) is primarily economic and logistical rather than technical.

Revenue and cost structure. Crumb rubber production generates a product with commodity value that is sold to end-use markets. TDF disposal generates a disposal fee paid by the tyre processor to the cement kiln operator or EfW facility; the energy value of the tyre is not typically returned to the tyre processor as revenue. In some arrangements where the TDF is genuinely displacing high-cost fuel, the economics may involve a gate fee lower than alternative disposal routes, but the tyre processor is generally not paid for the energy content.

Market scale and accessibility. The UK cement industry’s capacity for TDF is finite and concentrated in a relatively small number of facilities. Tyre processors seeking TDF outlets compete for access to available capacity at these facilities. The crumb rubber market, while also finite, has more buyers and more distributed demand.

Regulatory and permit complexity. TDF acceptance at any facility requires that facility to hold environmental permits covering co-processing. The permit conditions regulate the quantity and specification of TDF that can be accepted. This regulatory gating means TDF is not always available to tyre processors in all locations, particularly where there is no local permitted facility within economic transport distance.

When TDF makes commercial sense. TDF is the practical route for tyre streams that genuinely cannot reach material recycling outlets: very contaminated tyres, mixed tyre waste with high filler content, OTR tyre fractions that are uneconomic to process to crumb rubber, and tyre material generated in locations where material recycling infrastructure is not accessible within economically viable transport distances.

“TDF is the right answer in specific circumstances, not a universal solution,” says Conor Murphy, Director of Gradeall International. “The businesses that manage tyre streams most cost-effectively are those that direct each tyre type to its highest-value route. Retreading for sound truck casings, PAS 108 baling for whole car tyres, crumb rubber for general tyre streams, and TDF for the residual fraction that can’t reach the higher routes. Getting the front-end processing right, with the right equipment for each tyre type, is what enables this tiered approach.”

Contact Gradeall International for tyre processing equipment that enables efficient processing across all end-of-life tyre routes.

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