Matter does not disappear

There is one claim from the early Clean6 story that I have kept coming back to.

In the 2012 C6 presentation, the Vortex was promoted as producing no bottom ash and no fly ash. Later Clean6/Xetrov material softened that slightly, referring instead to around 98 per cent conversion and roughly 2 per cent residue. The basic proposition remained the same: burn the waste very effectively and leave almost nothing behind.

It is an attractive claim for a waste incinerator. Ash is inconvenient. It has to be removed, stored, tested and either reused or disposed of. If a technology can genuinely reduce that burden, that is a real advantage.

For quite a while I treated the ash claims as just another performance number to be checked against operating data. Then I realised residue is much more interesting than that. Following the material that does not burn takes us through some of the most important parts of the Xetrov story: the fuel, particle behaviour inside the vortex, the 2024 patent, cleaning and maintenance, the Glan Devon residue figures, particulate emissions and the still-undefined air-pollution-control system.

And the entire trail starts with one very ordinary fact.

Matter does not disappear.

What does “98 per cent conversion” actually mean?

Combustion can make a solid object appear to disappear because much of its mass becomes gas. Take a relatively clean hydrocarbon such as polyethylene. Its carbon and hydrogen react with oxygen during combustion and most of the original plastic can leave the furnace as gaseous products.

But a waste-derived fuel is not made entirely from combustible carbon and hydrogen. There can be dirt, mineral fillers, metals and other inorganic material. Timber has an ash fraction. Agricultural plastic can bring mineral material and other contaminants with it, depending on where it came from and how it was prepared. Chapter 5 matters here because until the commercial fuel is properly defined, neither is the amount of mineral material entering the Xetrov.

High temperature does not make those atoms cease to exist. Some materials may melt. Some can react chemically. Some elements can become volatile at high temperature and later condense as the gas cools. But somewhere in the complete process the material still has to be accounted for.

That is what makes the phrase “98 per cent conversion” surprisingly difficult to interpret. Conversion of what? Is it a 98 per cent reduction in the original solid mass? Conversion of combustible carbon? Destruction of organic material? Reduction in waste volume? Energy conversion? Those are very different measurements.

If it means that only 2 per cent of the incoming feed leaves through the main residue outlet, that tells me something useful about that outlet. It does not necessarily tell me what happened to the rest of the non-combustible material. Some may have left somewhere else.

The technical evidence assembled so far does not contain a representative Xetrov mineral mass balance that closes this question for the fuels proposed at Glan Devon. If a fuel contains more than 2 per cent non-volatile mineral matter, then a universal 2 per cent solid-residue claim requires another identified pathway for the remainder.

That turns the old “no bottom ash and no fly ash” claim into something much more useful than a historical curiosity. It gives us a trail we can follow through the actual engineering.

Pollington makes the story much more ordinary

Once I moved away from the brochures and into the Pollington permit, the residue story became much more conventional.

Pollington was not designed on the assumption that nothing solid would remain. The permitted process included prepared waste being screened, hammer-milled and screw-fed into the refractory cyclone. It also included a deliberate residue-handling system. The remaining solid material was to be augered out, quenched, dried and removed from the site.

That is exactly the sort of equipment I would expect to see in a real waste-incineration plant. Some material burns and some does not; the material that remains has to be removed.

This does not prove the earlier Clean6 claims were false. There may be a definition behind them that I have not found. Perhaps “no bottom ash” meant no conventional grate-ash stream. Perhaps the 2 per cent figure applied to a particular prepared fuel under particular operating conditions. Perhaps “conversion” referred mainly to the combustible fraction.

I do not have the evidence to choose between those explanations. What Pollington establishes is simpler and more important: a practical Xetrov installation expected solid residue and included machinery to remove it.

Then, in 2024, residue appears again. This time in Xetrov’s own patent.

The patent follows the material through the machine

Chapter 4 looked at the 2024 patent mainly because it showed what Xetrov engineers were still working on after more than a decade of public development. For the residue story, one part deserves another look.

The patent does not merely acknowledge that residue exists. It devotes specific engineering to where it collects, how it moves and how it gets out. The design includes a groove intended to collect combustion residue, an opening through which that material can leave, and an auger intended to remove it continuously. The same patent also addresses particle accumulation, access for cleaning and arrangements for separating and moving heavy refractory-lined sections of the chamber during maintenance.

That makes sense once I think about what the Vortex is actually doing. The machine is not a conventional grate furnace where material simply travels mechanically along a bed. It is deliberately using a fast-moving rotating gas field to influence particle behaviour.

Some of the feed burns almost completely. Some contains material that cannot burn. Different particles have different sizes, shapes and densities, and Xetrov’s own CFD work describes different particles taking different paths through the chamber.

So residue management has two linked questions: how much non-combustible material is entering, and where does that material actually go once it is inside the Vortex?

If it reaches the residue groove and leaves through the auger, the system is doing what the design intends. If it sticks somewhere else, it becomes a deposit. If it remains inside the machine, it may eventually have to be cleaned out. If it travels with the combustion gases, it becomes a downstream problem.

That begins to explain why particle behaviour, residue collection, cleaning access and refractory maintenance all appear together in the recent patent. They are not separate curiosities. They are different parts of the same solids-management problem.

The missing operating history matters here

The patent does not tell me why Xetrov developed these particular changes. I cannot say that they were responses to failures at Pollington or Daventry. They may have come from operating experience, laboratory work, CFD modelling or some combination of those things. The public record does not let me make that connection.

But there is another problem. I also do not have the long operating history that would show the earlier residue arrangements had already demonstrated reliable performance over commercial periods.

Pollington is clearly a real physical plant. Siemens described it as built and operating, and its permit contains proper operating and monitoring requirements. But the public record I have found does not establish sustained operation at its theoretical 8,000-tonne-per-year duty, annual availability or a long series of operating and emissions records. Xetrov’s own later description calls Pollington an R&D or pilot site rather than a replicated commercial reference.

There is also the reported 2026 enquiry with East Riding Council discussed in Chapter 3. The resident concerned said Council told him Pollington was mothballed, had run only briefly and had not produced the expected emissions-testing record because of that limited operation. I still do not have the underlying Council correspondence, so I cannot elevate that account into a primary finding. It does, however, sit consistently beside the broader absence of a public long-duration Pollington operating record.

Daventry does not close the gap either. Official 2024 material still described construction, commissioning and testing as under way.

That leaves the 2024 patent in an interesting position. It proposes new engineering for residue collection, particle movement, cleaning and maintenance while the public record does not contain the endurance history that would show how the previous arrangements behaved over thousands of commercial operating hours.

I cannot say the patent proves there was a prior operating failure. But neither can short pilot or commissioning runs demonstrate that the residue problem had already been solved for continuous commercial service.

That distinction becomes important when we get to Glan Devon.

Glan Devon gives us an actual number

The Glan Devon process documentation identifies a maximum ash and inerts rate of 71 kilograms per hour from the Xetrov process, with the material going to a bunker before off-site disposal or possible assessment for reuse.

That figure caught my attention because elsewhere the Glan Devon process assumes a nominal fuel rate of about 1,000 kilograms per hour. If the old 2 per cent residue figure were applied directly to that fuel rate, the result would be about 20 kg/h.

The Glan Devon process allows for a maximum of 71 kg/h of ash and inerts — equivalent to 7.1 per cent of the nominal hourly fuel input.

I do not think that arithmetic proves a contradiction. The figures may have different definitions and operating bases. One is a broad Clean6/Xetrov performance claim whose precise meaning has not been established. The other is explicitly a maximum design allowance for ash and inerts at Glan Devon.

But that difference is precisely why the mass balance matters. If the actual Glan Devon fuel can produce 71 kg/h of solid material, then the plant has to be able to manage that possibility regardless of what a generic “98 per cent conversion” statement says.

And 71 kg/h becomes surprisingly substantial when placed inside an industrial operating schedule. If — purely to show scale — the maximum rate occurred for 8,000 hours, the arithmetic is 568 tonnes.

That is not a prediction that Glan Devon will produce 568 tonnes of ash each year. The DA does not say the maximum rate occurs continuously, and converting a maximum directly into an annual forecast would be misleading. The calculation simply shows that this is capable of being a material industrial waste stream rather than a trace by-product.

Which brings us back to the engineering. Hundreds of tonnes do not simply vanish from a machine. They have to move through it.

There is more than one way out of a furnace

Imagine following the mineral part of the fuel rather than the combustible part.

A mineral particle enters the Vortex attached to, or mixed with, the prepared fuel. The organic material around it burns away. What happens next?

One possibility is exactly what the Xetrov residue system is designed for: the particle reaches the residue collection area and leaves through the auger. But that is not the only possible pathway.

Some material can strike or adhere to refractory surfaces. Some can deposit further downstream in heat-recovery equipment or ductwork. Some can remain suspended in the combustion gases and continue through the plant. At sufficiently high temperatures, some elements can enter the gas phase and later condense as the gas cools.

So a more complete mineral balance looks something like this:

incoming minerals → extracted residue + internal deposits + downstream deposits + particulate captured later + material leaving through the stack

The proportions are what matter.

If most of the material leaves cleanly through the residue auger, then the solid-handling system carries most of the burden. If more remains inside the machine, cleaning and maintenance become more important. If more travels with the flue gas, the heat-recovery and air-pollution-control systems carry more of the burden. And if some passes through those systems, it becomes an emissions issue.

This changes the meaning of “low bottom ash”. Low bottom residue is only a clear advantage after the rest of the mineral material has been accounted for. Otherwise the material may simply have changed location.

The fine material is where residue and emissions meet

This brings us back to one of the features that makes vortex combustion so effective.

The machine is very good at keeping particles moving in a strong gas flow. That helps produce the intense combustion described earlier in this series. But after the combustible part of a particle has burned, the remaining mineral matter does not necessarily become a large, convenient lump that drops into an ash bin.

Some of it can be fine, and fine particles are much easier for moving gas to carry downstream.

The old EPA vortex work showed this distinction particularly clearly. The combustion performance was impressive in one respect: the organic fraction of the collected particulate was low, indicating strong burnout. But the particulate-control performance was poor. Both reported particulate tests failed the applicable limit, and the material remaining after the cyclone was heavily skewed toward fine particles. Most was below about 12 micrometres, with roughly half below 2 micrometres in the reported analysis.

That was a different machine and I am not using those numbers as a prediction for Xetrov. The lesson is narrower: burning the combustible part of a particle well does not mean the remaining mineral particle disappears. It may simply become a very well-burned particle travelling in the flue gas.

That brings us to the Xetrov test being used at Glan Devon.

The polyurethane “dust” raises another unanswered question

The Glan Devon air-quality assessment gives us some information about particulate emissions, but not the information needed to follow the particles through the machine.

Vipac says the Xetrov source data it used came from a client-supplied document called the “Xetrov DRAX FBA Test Report.” That underlying report is not included in the public DA documents I have reviewed. What is available publicly is Vipac’s summary of selected results from it: the test used polyurethane dust, operated at about 70 per cent capacity, and had no emissions-control equipment at the test site.

That missing report matters here because the fuel is described as polyurethane dust.

How fine was it?

Was most of the material millimetres across? Hundreds of micrometres? Tens of micrometres? Finer again? And how did the size distribution of the material entering the Xetrov compare with the particulate leaving it?

That could be a very revealing comparison. If I knew the feed particle-size distribution and the emitted particle-size distribution, I could begin to ask what proportion of the fine material was carried through, what changed during combustion, and what new particulate may have formed as material burned or gases cooled.

I do not know whether the missing DRAX/FBA report contains those data. The point is that the public application material does not give them to me.

The Glan Devon air assessment does use particulate categories such as PM10 and PM2.5, but that is a different thing. Those are size classes used to assess the dispersion and potential impact of emitted particulate in the atmosphere. They are not a measured before-and-after particle-size distribution showing what happened to the solid material inside the combustor.

So there are two quite different particle questions.

The air model asks: if particulate is emitted in these size classes, where will it go in the atmosphere?

The engineering question asks: what size particles went into the Xetrov, what size particles came out, and where did the rest of the solid material go?

The public record does not yet let me answer the second question.

That is exactly the point where this residue story starts turning into the emissions story.

Then we reach the pollution-control system

There is another reason the mass balance cannot yet be closed.

The Glan Devon DA does not specify the final air-pollution-control system.

The February air assessment says the abatement-package details had not been determined and models the Xetrov source without abatement. Later May material says an emissions-abatement package and continuous emissions monitoring will be incorporated, but it does not identify the final components or their demonstrated performance. SARA’s further advice then explicitly objects to choosing the APC system after later stack testing rather than defining an adequate system at the design stage.

That matters because pollution-control equipment does not destroy matter either.

Whatever final system is eventually selected, if it captures particulate successfully, that particulate moves from the gas stream into another material stream. If sorbents are used to capture contaminants, the sorbent and captured material become residue. If material is collected in filters, it becomes filter dust. If deposits are later cleaned from ducting or heat-recovery equipment, they have to go somewhere as well.

Successful pollution control is therefore partly a process of moving contaminants out of the air and into something that can be contained and managed. That is a good thing, but it means the pollution-control system belongs inside the plant’s mass balance.

At Glan Devon, all three parts of that balance remain incompletely defined.

The commercial fuel specification does not yet tell us the representative mineral input. The available Xetrov operating record does not tell us how that mineral load divides, over long-duration operation, between extracted residue, deposits and entrained particulate. And the final APC system does not yet tell us how much downstream material will be captured or what additional residue streams that capture will create.

Now the original “no ash” claim looks very different.

This was never really just a story about ash

What started as a striking marketing claim turns out to reveal a fairly fundamental engineering question.

In 2012 the C6 proposition was no bottom ash and no fly ash. Later Clean6/Xetrov material talked about approximately 98 per cent conversion and around 2 per cent residue.

Then the practical engineering record became visible. Pollington had equipment specifically designed to remove solid residue. The 2024 patent contains further engineering for collecting residue, moving particles, cleaning accumulated material and gaining access to the refractory-lined chamber. And Glan Devon itself allows for a maximum 71 kg/h of ash and inerts.

None of those later provisions is surprising. Quite the opposite. They are what I would expect to find in the design of a real waste incinerator.

What they do is remove the simplicity from the old claim.

The important question is no longer whether Xetrov produces “ash”. It is whether the non-combustible material entering the system can be accounted for from one end of the plant to the other.

For Glan Devon that means knowing the mineral content of the actual commercial fuel, then following that material through the residue outlet, deposits, heat-recovery equipment, future pollution-control system and finally the stack.

I have not found that complete representative balance. Without it, “98 per cent conversion” is not enough information to tell me where the material went.

And this is where the residue story naturally turns into the next part of the investigation. Once particles and other material leave the combustion chamber in the gas stream, they are no longer just an ash-handling problem.

They are an emissions problem.

The next question is therefore the obvious one:

What actually comes out of the stack?

Next Chapter