TDF vs Tire-Derived Aggregate (TDA): Processing & Uses

TDF and TDA can start with the same discarded tire and even leave the same primary shredder. They are not interchangeable products. Tire-derived fuel is bought for controlled combustion; tire-derived aggregate is accepted as an engineered material for civil works.

The decisive difference is the function after the tire plant

TDF is sold for energy recovery in facilities such as cement kilns, pulp and paper mills and suitable industrial boilers. Its useful properties are fuel value and, depending on the user, the mineral contribution from tire steel. TDA replaces or supplements conventional civil materials where low unit weight, drainage, compressibility, thermal insulation or vibration behavior is valuable. CalRecycle lists lightweight fill, road and embankment repair, drainage and vibration mitigation among established applications.¹

A fuel user is concerned with stable feeding and combustion. A civil engineer is concerned with the installed layer and its interaction with soil, water, loads and construction equipment. Calling all rough tire chips “TDF” or “TDA” hides the most important commercial fact: the same lot may be acceptable to one receiver and rejected by the other.

Size labels are useful only inside a named specification

The YUXI Tire TDF Plant describes a standard 50–80 mm setting and an adjustable range up to roughly 150 mm. Those figures explain one equipment configuration. A cement kiln that accepts larger chips and a boiler with a smaller feed opening may write different limits.

TDA terminology spans a wider coarse range. ASTM D7760-18 covers hydraulic-conductivity testing for tire chips, tire shreds and TDA with particle sizes of approximately 12–305 mm.² CalRecycle illustrates Type A at about 2–3 inches and Type B at approximately 8–12 inches.¹

Processing routes: shared front end, different finishing logic

Both products normally begin with tire inspection, removal of prohibited items, metered feeding and size reduction. Large truck or OTR tires may need bead-wire removal or pre-cutting to fit the selected shredder and reduce shock loading. From there, the routes diverge.

TDF route

A typical route uses shredding, screening and an oversize-return loop. Finer settings increase recirculating load: material that does not pass the screen returns to cutting, so headline shredder throughput is not finished-product capacity. Fuel buyers may accept steel-bearing TDF, request bead removal, or impose tighter limits. The practical rule in the TDF quality specification guide still applies here.

TDA route

TDA can use a coarser screen, a different cutter arrangement or a controlled bypass, but coarse does not mean uncontrolled. Long strips, partially cut sidewalls and hazardous protruding wire can create placement and safety problems even when the average piece looks large enough. The project may also restrict soil, glass, free liquid and other contaminants. If a plant is quoting a dual-product line, it should show how the discharge route prevents a previous fuel recipe from contaminating a civil-material lot.

Steel is not a simple “remove or keep” decision

Steel condition is one of the easiest places to write a misleading comparison. For TDF, some cement users value part of the steel as process input, while other fuel-handling systems restrict loose or exposed wire. For TDA, the design specification may permit steel-bearing pieces but limit protrusions that could injure workers, damage geosynthetics or complicate placement. Complete liberation and magnetic recovery, by contrast, move the output toward wire-free mulch rather than coarse TDA.

Record bead treatment separately from belt-wire condition, then define maximum exposed length, loose-wire policy and inspection or sampling method. Buyers comparing a coarse route with a wire-free mulch plant should also recognize that the latter adds secondary reduction and steel liberation to make a different 10–20 mm product.

Applications and the proof each market expects

ASTM D6270-25 is the current listed practice for scrap tires in civil engineering applications.³ Its scope makes the design engineer responsible for deciding whether the material is appropriate and which tests and specifications facilitate construction and environmental protection. A 2022 Vermont Agency of Transportation report, for example, evaluates TDA specifically for underdrain applications rather than treating every coarse tire shred as a generic aggregate.⁴ That is a different governance model from a fuel acceptance agreement.

For TDF, the receiving facility must remain within applicable operating and emissions requirements. EPA’s archived technical FAQ notes that combustion performance depends on properly designed equipment, good combustion control, particulate controls and compliance testing.⁵ The industrial boiler guide explains why feed system limits and permit conditions should be confirmed before a chip size is promised.

Can one plant switch between TDF and TDA?

Yes, when the equipment and operating documents are designed around two validated recipes. The business case should not assume instant changeover. A larger TDA opening can reduce return load, but a screen change, bypass setting, conveyor cleanout and separate stockpile may consume production time. Switching back to a tighter TDF recipe can temporarily increase oversize until the circuit stabilizes.

A credible dual-product quotation identifies:

• the exact feed envelope used for each capacity claim;
• the installed screen, alternate screen or bypass arrangement;
• bead removal and loose-wire handling for each recipe;
• how mixed transition material is quarantined;
• weighing and sampling points for accepted product, return, steel and rejects;
• changeover labor, lifting equipment and expected downtime;
• separate guarantees for TDF and TDA rather than one “maximum throughput.”

A supplier can use the format in the TDF plant RFQ guide, but the TDA appendix should be signed off by the project engineer. A fuel user’s specification cannot stand in for civil design.

Do not release TDA until the civil project passes four gates

TDF normally has a repeat receiver that can test incoming fuel. TDA often moves against a specific construction package, so the processor needs a project-release gate before manufacturing inventory. EPA describes civil-engineering tire material as a substitute for materials such as lightweight fill, drainage aggregate or soil—not as a generic disposal route.⁶

ASTM D6270-25 includes design and construction guidance intended to minimize internal heating and limits the practice’s application to TDA fills below the thickness boundary addressed by its guidance.⁷ A processor should never turn that into a universal fill-thickness recommendation: the current standard, project design and local approval must govern the actual installation.

Give every lot a product passport

Each production lot should carry a compact record that links the receiving contract to what happened on the line. This prevents coarse transition material from being relabeled after production merely because another buyer appears.

Write the disposition options before a failure occurs: reprocess, downgrade to another already-approved specification, return, or reject. Any downgrade must preserve traceability and satisfy the second receiver’s written requirements.

Compare economics at the delivered, accepted product boundary

Coarser TDA may require less cutting energy and fewer recirculation passes than smaller TDF. TDA can be project-based, ordered by volume, and sensitive to the construction schedule. Its low bulk density can use trailer volume before legal payload is reached. TDF may be denser or smaller, but it still carries storage, fire-control and fuel-user delivery constraints.

Use a scenario model rather than a generic cost-per-ton promise:

The useful equation is contribution per accepted delivered unit, not price minus shredder electricity. Include feed acquisition, preparation, processing, changeover, sampling, storage, loadout, freight, rejection allowance and any recovered-steel credit. When TDA is sold by volume, show the assumed loose or compacted density; otherwise a per-cubic-yard margin cannot be compared with a per-ton TDF margin.

Normalize mass-based TDF and volume-based TDA before choosing a route

A spreadsheet should preserve both mass and volume instead of forcing one estimate into the other’s unit.

Measure loose bulk density from representative product. For placed TDA, keep loose delivery volume separate from compacted in-place volume. Settlement and compaction belong to the civil design and construction records. For TDF, keep received mass separate from any moisture or contamination adjustment in the buyer’s settlement formula.

Run at least three commercial cases: contracted base load, delayed TDA project, and temporary loss of the fuel receiver. This exposes whether the plant has genuine outlet flexibility or simply two product names competing for one stockpile area.

Contract fields that make a dual-product guarantee enforceable

Factory acceptance test for a dual-product claim

Run the TDF and TDA recipes as separate stable tests using representative feed. The same weighing discipline applies to both, but each product needs its own conformity check.

1. Freeze feed and settings. Record tire categories, preparation, cutter arrangement, screen or bypass and control settings.
2. Use a stable observation window. Report machine running time and elapsed test time; list stops, reversals and interventions.
3. Weigh routes separately. Input, accepted product, oversize/return, recovered steel, other rejects and retained material should not be merged.
4. Reconcile the balance. Report unexplained difference separately instead of hiding it inside “losses.”
5. Test the named product. TDF: size, oversize, steel/contamination and contract analyses. TDA: project gradation, maximum piece, protruding wire, cleanliness and required engineering tests.
6. Keep traceability. Seal retained samples, photos, scale records, settings and the test report to the lot and recipe.

The same discipline is expanded in the TDF plant factory acceptance test. For a dual-purpose line, add a witnessed changeover and verify the first conforming lot after the switch.

A practical selection sequence

1. Secure at least one realistic offtake route for each proposed product.
2. Obtain the full receiver or project specification, not a verbal size request.
3. Map every requirement to feed preparation, cutting, screening, separation, handling and test equipment.
4. Trial the worst credible tire mix rather than clean passenger tires only.
5. Calculate accepted delivered economics under low, expected and high demand.
6. Buy dual-product flexibility only when the changeover method and both guarantees are written into the contract.

This sequence prevents a common capital mistake: purchasing a coarse tire shredder first and searching for a legal, specification-compliant market afterward. TDF and TDA are both established outlets, but neither is simply “shredded tires.”

Frequently Asked Questions

Engineering References

1. CalRecycle, TDA guide. Applications and examples.
2. ASTM International, D7760 standard. Hydraulic-conductivity testing.
3. ASTM International, waste standards. Scrap-tire civil-use context.
4. VTrans, underdrain report. TDA field context.
5. U.S. EPA, TDF FAQ. Fuel-use questions.
6. U.S. EPA, civil applications. Processed scrap-tire uses.
7. ASTM International, D6270 standard. Civil engineering applications.