The Feedstock File — What the X-150 Has Actually Burned

Every small-scale gasifier on the market is rated for one fuel: clean dry wood chips, typically DIN Plus wood pellets. The X-150 ran for 1,939 hours on digestate pellets from municipal solid waste, sewage sludge, and horse manure at the COMETHA campaign in Paris. No clinkering. No feedstock-related shutdowns. The data is published. The machine is not a prototype. What makes the X-150 different is not what it can be rated for but what it has already proven on.

Why Now

Every gasifier operator's nightmare looks the same. The fuel bed is sintering into glass. Gas flow drops. The grate is clogged. The machine must be shut down, cooled, and manually cleared. For fixed-grate systems running on anything other than clean wood chips, this happens every 200 to 500 operating hours. The shutdown alone costs a day of production plus the labor of manually breaking clinker.

This is the reason the small-scale gasification market has been stuck for 20 years. Volter (40-140 kg/h), Spanner Re (30-150 kg/h, 500+ units deployed), Syncraft (60-100 kg/h), Burkhardt (100-500 kWth) — every one of them runs fixed grates. Every one of them is limited to clean wood chips. Every one of them would clinker within 500 hours on digestate pellets from municipal waste.

The world does not produce enough clean wood chips to power distributed gasification at meaningful scale. The world produces 2 billion tonnes of municipal solid waste annually, plus 120 million tonnes of sewage sludge, plus an enormous volume of agricultural residues. The only way distributed gasification scales is if the machines can burn what is locally available rather than what is ideally processed.

The X-150 is the only machine in its class that has proven it can.

What We Built

The X-150 is a fixed-bed downdraft gasifier built around a single mechanical difference from every competitor: the Walzenrost, a rotating roller grate instead of a fixed grate. A fixed grate relies on the fuel bed staying porous as ash melts and sinters. The roller grate rotates continuously, mechanically breaking up any forming clinker before it can consolidate. The thermal profile at 950C in the oxidation zone is severe enough to soften the ash of most non-woody feedstocks. The roller grate's shearing action prevents those softened particles from sticking.

The COMETHA campaign ran at the Syctom waste treatment facility in Paris from March 2025 to February 2026. The machine processed 16,382 kg of digestate pellets across three distinct feedstock types over 1,939 continuous hours.

The first feedstock was digestate pellets from municipal solid waste separation, with an ash content of 8-15%. This is the standard output from a mechanical biological treatment plant: the organic fraction of household waste, digested anaerobically, dried, and pelletized. The ash contains typical city waste contaminants: elevated levels of potassium, chlorine, and trace heavy metals. Ash fusion temperature sits well below that of clean wood.

The second was sewage sludge digestate from wastewater treatment, with ash content of 15-25%. Sewage sludge digestate is one of the most difficult fuels in the gasification industry. The ash is rich in phosphorus, iron, and calcium from wastewater treatment chemicals. The ash melting point is low, and the phosphorus can form low-melting eutectics that accelerate clinkering. Most fixed-bed gasifiers cannot handle sewage sludge at any blend ratio.

The third was horse manure digestate, ash content 10-18%. Horse manure has high silica content from soil ingestion during grazing and high potassium from the forage diet. This combination produces low-ash-fusion-temperature silicates that are notoriously aggressive on refractory linings and grates.

Over 1,939 hours, across these three feedstocks with ash contents ranging from 8-25% and widely different ash chemistries, the machine recorded zero clinkering events. The overall ash content across all batches averaged 19-34% depending on the batch. Moisture content ranged 9-15%. Carbon content ranged 29-37%. Total system efficiency measured 59.1% chemical-plus-thermal, with a cold gas efficiency of 72% at steady state.

The syngas composition was consistent across feedstock transitions: 33% hydrogen, 16.6% carbon monoxide, 38.8% carbon dioxide, 5.3% methane. The catalytic reformer maintained 99.98% tar conversion. The machine ran through feedstock changes that would have destabilized a sequential control system.

Beyond the COMETHA campaign, the MFC engineering team has validated the platform on wood pellets (DIN Plus), agricultural straw, fermentation residues, and organic waste fractions. The mechanical poker system extends the ash handling capability further: a driven poker penetrates forming slag layers from above in the oxidation zone, preventing bridging above 1,100C, while the water-cooled crusher grate at the bottom continuously discharges ash and slag fragments.

The mechanical modifications during the COMETHA campaign were minor and routine for pilot operation: a tar trap mesh insert, an upgrade to two stronger roller grate bearings, trace heating optimization on the ceramic filter and gas lines, and a syngas flare replacement. All are standard engineering learning adjustments, not fundamental redesigns.

The question is not whether the X-150 can burn non-woody feedstocks. The question is what happens when it encounters a feedstock it has not seen before.

The answer depends on ash chemistry. The Walzenrost handles the mechanical problem of clinkering by breaking up softened ash before it consolidates. But ash chemistry determines how corrosive the ash is to the refractory, how much alkali metal vaporizes into the syngas and fouls downstream surfaces, and how the char behaves at the bottom of the reduction zone. A feedstock with very high chlorine content (above 1%), extreme potassium levels, or very low ash fusion temperature approaching 800C would need pre-treatment blending or additive injection (dolomite or CaO at 2-5%) to raise the effective ash melting temperature.

The X-150 feedstock specification sheet, documented as X150-FSS-001, defines 13 hard and soft limits including maximum moisture of 20%, maximum particle size of 30 mm, maximum ash content of 50%, and maximum chlorine of 1%. Any feedstock within those limits is runnable with adjustment to the steam-to-carbon ratio and the oxidation zone temperature setpoint. Feedstocks outside those limits require drying, shredding, blending, or additive treatment before feeding.

The pre-treatment infrastructure is well understood. Solar or waste-heat belt dryers bring moisture from as high as 50% down below 15%. Industrial hammer mills or shredders handle particle size. Pelletizing solves bridging in the gravimetric feeder. Blending with wood pellets at 30-70% starter ratios allows a ramp-up to full target feedstock over days or weeks. None of this is R&D. All of it is commercially available at costs that are small relative to the EUR 2.3 million total project CAPEX for a CHP installation.

Why It Matters

For the operator in the field, feedstock flexibility is the difference between a machine that runs and a machine that is a liability. A resort in Bali produces food waste. A palm oil mill produces 22 million tonnes of empty fruit bunches annually across the region. A municipal waste processing facility produces digestate pellets as a daily output. Each of these feedstocks is available at zero or negative cost because the producer needs to get rid of it. An X-150 operator can buy fuel at EUR 0-20 per tonne instead of EUR 150-300 per tonne for DIN Plus wood pellets.

For the investor, this is the critical differentiator. Every other small-scale gasifier is structurally dependent on the clean wood chip supply chain, which is geographically constrained, seasonally variable, and priced against competing uses (pellet stoves, industrial heating, animal bedding). The X-150's feedstock flexibility decouples the unit economics from a single fuel market. If wood chip prices spike 40% in winter, the operator switches to the local digestate supply. The IRR model changes from marginal to bankable.

For the engineer, the open questions are well defined. Ash chemistry variability across different digestate sources needs a larger database. The long-term effect of high-phosphorus sewage sludge ash on the refractory is not yet quantified beyond the 1,939-hour run. The alkali vaporization rate from high-potassium feedstocks and its impact on the downstream heat exchanger fouling need dedicated measurement. These are engineering studies, not fundamental technology risks. The machine has proven it can handle the mechanical and thermodynamic challenge. The remaining work is optimizing the pre-treatment and maintenance schedule for each specific feedstock family.

One thousand nine hundred thirty-nine hours on three of the most difficult feedstocks in the waste industry. Zero clinkering events. Consistent 33% hydrogen output. The feedstock file is not a theory. It is the operating log from a machine that ran for 80 straight days in Paris and did not stop.