Waste Tyre Gasification: Yields, Limits and Reality

Waste tyre gasification is one of the few waste-to-energy topics where the search results are almost entirely paywalled abstracts. That is a problem for anyone with an actual tyre pile to deal with. Europe alone generated 3.45 million tonnes of end-of-life tyres in 2019, with Germany at 434,000 tonnes and Spain at 238,080 tonnes, and most of the energy-recovery share went into cement kilns. Gasification promises something better than kiln fuel: a syngas you can clean, burn in an engine or upgrade to hydrogen, plus a carbon-rich char and clean steel.

This is the operator's version. It covers what a tyre actually is as a feedstock, the operating window the published trials measured, why zinc and sulphur are the real engineering problem, why co-gasification with biomass is the route most likely to work, and an honest reading of where the technology stands against tyre pyrolysis.

What waste tyre gasification is and what comes out

Gasification is partial oxidation. You starve the reactor of oxygen so the rubber does not burn to CO2 and water, but cracks into a gas of hydrogen, carbon monoxide, methane and light hydrocarbons, leaving a solid carbon residue behind. For most waste streams the solid is ash. For tyres it is something more interesting.

Tyre composition: why the feedstock is unusual

A passenger car tyre is roughly 43% rubber, 28% carbon black and silica, 13% metal, 5% textile, 2% zinc oxide and 1% sulphur by the ECHA composition table, with 7% process oils. Truck tyres swap textile for more steel, at 25% metal. Three things follow for a gasifier operator:

• Very high volatile and carbon content, almost no ash. Compared with sewage sludge or municipal waste, tyre rubber is a dense, dry, energy-rich feed. The char that remains is mostly the original carbon black filler, not mineral ash.
• Steel has to come out first. No gasifier bed tolerates 13 to 25% steel wire. Shredding and magnetic separation are part of the plant, not an option.
• Zinc and sulphur are built into the recipe. Both volatilise in the reactor and both end up where you do not want them. More on that below.

Syngas, carbon black and steel

In the most cited lab study, an air-blown fluidized bed produced 550 to 650 grams of carbon black per kilogram of tyre alongside the gas. That is the central economic fact of tyre gasification: more than half the mass leaves as a solid carbon product, not as gas. Whether that solid is a revenue line or a disposal cost depends on its quality, and the same study measured a surface area of only 20 to 30 square metres per gram, well below what tyre makers expect from recovered carbon black.

The operating window the data supports

Temperature and equivalence ratio

The fluidized-bed work ran from 400 to 800 C at equivalence ratios between 0.2 and 0.6, meaning 20 to 60% of the air needed for full combustion. The authors landed on 650 to 700 C and an equivalence ratio of 0.2 to 0.4 as the practical window. Above 700 C the gas heating value barely improved, so extra temperature bought little. Above 600 C the carbon balance closed at 85 to 95%, a sign the chemistry was behaving.

A different reactor concept, a hybrid filtration bed of tyre particles mixed with alumina spheres, ran far hotter. Its reaction wave reached 1,100 to 1,500 K with air and with steam, producing hydrogen and carbon monoxide as the main products and emitting fewer solid particles than runs below 1,100 K. The lesson across both: tyre rubber gasifies readily, and the designer's choice is between a cooler bed that preserves more char and a hotter one that pushes conversion to gas.

Syngas yield and heating value

In the 650 to 700 C window the fluidized bed gave 1.8 to 3.7 normal cubic metres of gas per kilogram of tyre with a lower heating value of 4,000 to 9,000 kJ per cubic metre. That is a lean producer gas, diluted by the nitrogen in the air, and it sits in the range a gas engine can run on. Yield rose linearly with equivalence ratio while heating value fell, the usual gasification trade-off: more air, more gas, weaker gas.

Hydrogen from tyres: what the reviews say

Tyres appear alongside municipal waste and plastics in the 2024 KIT and KTH review of hydrogen from waste gasification. Its literature survey found hydrogen productivity ranging from 15 to 300 grams of H2 per kilogram of feedstock, a twentyfold spread that depends on the feedstock and on whether the gasifying agent is air, steam or oxygen and steam. Air gasification lands at the bottom of that range. Steam reforming of the volatiles and the water-gas shift push it towards the top.

The same review is blunt that hydrogen from waste gasification has a high productivity potential but needs frame conditions or subsidies to reach the market. That matches what we see in grant-funded deployment.

For a reference point on what nitrogen-free operation looks like, Zero-X's X-150 ran 1,939 continuous hours in Paris on 16,382 kg of digestate pellets in oxy-steam mode, with 33% hydrogen in the syngas and an H2 to CO ratio of 1.95 to 1. That was digestate, not tyres, and we do not claim tyre-specific results. The point is the mode: oxy-steam without nitrogen ballast is how a small gasifier gets from a 5,000 kJ producer gas to a hydrogen-rich gas worth cleaning.

Why zinc and sulphur decide whether a tyre gasifier survives

Most articles on this topic stop at syngas yield. The projects that fail, fail downstream of the reactor.

Sulphur to H2S

The 1% sulphur that vulcanised the rubber leaves the reactor largely as hydrogen sulphide. In a gas engine it becomes sulphuric acid in the oil and the exhaust. In any catalytic step, whether a shift reactor for hydrogen or a methanol synthesis loop, it poisons the catalyst. The Oboirien and North review of waste tyre gasification lists loss of catalyst activity in tyre gasification and co-gasification as a gap that still needs research. For an operator that translates to: budget for sulphur removal from day one, not as a retrofit.

Zinc in the char and the gas

The 2% zinc oxide is a cure activator in the rubber. At gasification temperatures part of it stays in the char, which affects what you can do with the carbon product, and part of it carries over with fine particles. The hybrid filtration reactor study detected zinc and iron peaks in its solid emissions by X-ray spectrometry, which is exactly what a filter and a stack monitor will see on a real plant.

Real-time measurement instead of guesswork

This is where small-scale waste gasification has moved on since most of the tyre literature was written. Zero-X's SyngaPure gas-cleaning module was selected for Germany's BMWK go-inno programme in December 2025 precisely because it measures tar, H2S, ammonia and particulates in real time and uses that signal to control the cleaning train. In the Paris campaign the system held tar conversion at 99.98% over 80 days. Tyres are a harder gas to clean than digestate because of the sulphur and zinc load, which is why we treat them as a blend feedstock rather than a sole feed, and why the gas-cleaning stage is the first thing to size, not the last. Our full breakdown of the problem is in tar removal from syngas.

Co-gasification with biomass: the realistic route

The Oboirien and North review draws one conclusion that matters more than any yield figure: co-gasifying tyres with biomass is advantageous. It increases the rate of tyre gasification and, in the modelled case, lowers the cost of producing methanol from the gas. It also notes there are few studies on the combination, and that a database of reaction kinetics for tyre-char and biomass-char blends is still missing.

From an operating standpoint the logic is simple. Tyre rubber brings energy density and carbon. Biomass, sludge or digestate brings oxygen, moisture for in-bed steam reforming and, crucially, the mineral content that dilutes the zinc and sulphur concentration in the gas. A fixed-bed downdraft unit handles a dense, uniform rubber crumb in a blend far more comfortably than it handles a pure rubber bed that fuses. We documented the same blend logic for plastic waste gasification, where pure plastic melts and bridges the bed, and for sewage sludge gasification, where high ash does the opposite and starves the gas.

For a tyre collector, this changes the project shape. Instead of a dedicated tyre gasifier that nobody has built at scale, you look for a nearby stream of agricultural residue, wood waste or sludge and design the plant around the blend.

Gasification vs pyrolysis for end-of-life tyres

Readers who search for tyre gasification are often really asking which thermal route to choose, and pyrolysis is the one with built plants and published economics. A 2024 open-access study modelled a 60 tonne per day tyre pyrolysis facility in Australia, with a conservative product split of 20% light oil, about 65% furnace oil and 7% carbon black. Running on its own fuel gas, the plant turned cash-flow positive in under four years, with internal rates of return between 15 and 35% across six scenarios.

The industry body Tyres Europe positions pyrolysis around recovered carbon black, which it says cuts tyre makers' CO2 emissions by up to 85% compared with virgin carbon black. That is the pyrolysis value proposition: oil and a material product.

Gasification is the energy and hydrogen route. It converts more of the mass to gas, it can run hotter and crack the oils that pyrolysis sells, and its product can feed a gas engine, a hydrogen separation step or a chemical synthesis. The cost is a leaner solid product and a harder gas-cleaning problem. If your offtake is heat and power for a site, or hydrogen, gasification is the right question. If your offtake is oil and rCB sales, pyrolysis is. We cover the general trade-off in gasification vs pyrolysis.

What is commercially real in 2026

Here is the honest status, because the research record is clear even if the marketing is not.

• Tyre gasification exists at lab and pilot scale. Fluidized beds, filtration reactors and co-gasification trials have all been published. A dedicated commercial tyre gasifier has not appeared in the peer-reviewed record that ranks for this query.
• Tyre pyrolysis exists at plant scale, with modelled paybacks under four years at 60 tonnes per day and an industry body actively promoting its carbon black.
• The incumbent is the cement kiln. In the 2019 ETRMA accounting, 1.37 million tonnes of European tyres went to energy recovery, with 75% of the mass sent to cement kilns counted as fuel. Tyres Europe reports a 95% collection and treatment rate, so this is a stream that is already managed, not a free resource.

For a developer, the credible path is not a bespoke tyre gasifier. It is a validated small waste gasifier with industrial-grade gas cleaning, taking tyre crumb as a blend partner next to a primary feedstock the machine already handles. The X-150 is validated on high-ash sludge, municipal waste and digestate, the feeds that fuse or clinker in clean-wood gasifiers, and its partner model is built around grant routes that fund 56 to 70% of project CAPEX in Wave 1 markets. A tyre stream adds energy density to that project; it does not need to carry it alone. The economics of that plant class are in our guide to small-scale waste-to-energy systems.

The research community has asked for a techno-economic model of tyre gasification since 2017 and still does not have one. The way that model gets written is with operating hours on real blended feed, not another lab run.

FAQ

Can you gasify whole tyres?

No practical gasifier takes whole tyres. Every published trial used shredded tyre particles with the steel removed first, because the 13% metal in a car tyre and 25% in a truck tyre would wreck a bed and block a grate. Shredding, wire separation and sizing are part of the plant design and part of the CAPEX.

Is tyre gasification better than burning tyres in cement kilns?

Cement kilns are the incumbent and they are cheap because the kiln already exists. Gasification wins only when you need a product the kiln cannot give you: a syngas you can clean and use for on-site power, hydrogen or chemicals, plus a recoverable carbon solid. If your region's tyres already have a kiln outlet, a gasification project has to pay for itself on those extra products.

What is the carbon black from tyre gasification worth?

Less than pyrolysis rCB in most cases. Gasification char from the fluidized-bed trials had a surface area of only 20 to 30 square metres per gram, and zinc partitions into it. It is a fuel or a soil and construction additive before it is a tyre-maker input. Treat it as a lower-grade product in the business case.

How much hydrogen can a tonne of tyres make?

The review literature gives 15 to 300 grams of hydrogen per kilogram of waste feedstock, so 15 to 300 kg per tonne, with air-blown systems at the bottom and steam or oxy-steam systems with shift and separation at the top. Tyre-specific commercial data does not yet exist, so size a hydrogen project on measured pilot data for your actual blend.