The Role of Cleaning and Conditioning Syngas in Sustainable Aviation

Syngas, or synthetic gas, is a versatile fuel produced through the gasification of waste feedstocks such as refuse-derived fuel (RDF). For Avioxx, this process transforms residual waste into a pathway of carbon-neutral fuels and power generation – but using raw syngas alone is not enough. For advanced applications like Solid Oxide Fuel Cells (SOFCs) and Fischer-Tropsch (FT) reactors, the gas must be rigorously cleaned and conditioned. This step breaks down unwanted elements into their basic forms and is essential for producing the highest-quality synthetic fuels.

Understanding RDF-derived syngas

Standard analysis of RDF-derived syngas highlights both its strengths and limitations. Alongside highly useful molecules such as carbon monoxide and hydrogen, it also can contain contaminants that make it unsuitable for direct use in reactors. A typical composition might be CO 27.15%, H₂ 20.08%, CO₂ 17.57%, N₂ 28.53%, CH₄ 6.31%, O₂ 0.37%, with an LHV of 7.84 MJ/m³.

The exact mix depends on the feedstock and the air or oxygen gasification technique, which is why cleaning the gas and carefully adjusting the CO and H₂ ratio are essential steps before it can be converted into liquid fuels. In practice, this ratio is tuned by enriching the syngas with hydrogen produced from electrolysis, ensuring the ideal balance for Fischer–Tropsch synthesis.

Contaminants include hydrogen sulphide, sometimes reaching 95 ppm, hydrogen chloride, ammonia, and trace metals such as copper, zinc and chromium. Without treatment, these species corrode reactors, poison catalysts and cut yields - which is why raw syngas cannot be fed straight into FT or SOFC systems.

Why cleaning is fundamental

Catalytic and electrochemical processes are highly sensitive, where even a few parts per million of sulphur or chlorine can deactivate a catalyst or damage costly components. Cleaning syngas is therefore not optional in this process, but fundamental.

The process involves several key stages:

• Removing particulates with cyclones or filters
• Taking out acid gases with CaO or NaOH guard beds
• Adjusting gas ratios, typically targeting a 2:1 hydrogen-to-carbon monoxide mix for FT use
• Polishing to eliminate residual metals and trace contaminants

Stripping out CO₂ further improves the calorific value and creates the right chemistry for synthesis. With technologies such as CaO beds or pressure swing adsorption, syngas can be made fully compatible with high-performance reactors.

The power of waste-derived inputs

The strength of syngas as a feedstock lies in its atoms that contain lots of energy - which in this case is carbon monoxide and hydrogen. Once these are released from waste through gasification, they become the building blocks of essential low-carbon fuels. Demonstrating that waste is therefore an effective feedstock as it cuts emissions whilst creating a pathway to fuels that can compete with fossil equivalents on cost.

But waste is never uniform – with feedstock compositions shifting from batch to batch, flexibility in this process is essential and involves cleaning stages with tolerance, dynamic ratio adjustment, and a strong control of downstream catalysts and reactors.

At Avioxx, artificial intelligence provides this control, continuously monitoring CO:H₂ ratios, predicting contaminant spikes, and adjusting flows, temperatures and guard bed performance in real time. This ability to turn highly variable waste into a consistent, reactor-ready gas stream is a core advantage of the Avioxx platform, and one that sets it apart in the race to produce scalable, low-cost sustainable fuels.

The Avioxx solution

Avioxx has developed a dual-vessel guard bed system positioned upstream of the X25 FT reactor and SOFC module. It removes acid gases and moisture, shields catalyst surfaces from permanent damage, and ensures a stable, conditioned gas stream enters the reactor. Each stream is validated before exposure, delivering consistent operating conditions and long-term reliability.

From waste to energy at scale

Every year the UK disposes of around 28.8 million tonnes of residual waste through incineration or landfill. If gasified, this material could generate roughly 44 billion cubic metres of syngas, equivalent in energy terms to around 1,100 petajoules or 30% of current UK natural gas demand.

Instead of being buried or burned, that waste could power the production of sustainable aviation fuel, e-diesel and e-gasoline while cutting emissions and reducing dependence on imported fossil fuels. Unlocking even a fraction of this potential would transform the UK’s waste problem into a domestic energy solution.

A foundation for the future

Clean syngas is not simply a fuel source; it is the platform on which low-carbon fuels are built. Converting waste into precise CO:H₂ ratios and contaminant-free streams allows reactors to operate at peak efficiency, protecting catalysts and ensuring long-term reliability. This engineering precision is what makes clean syngas scalable, cost-competitive, and ultimately capable of displacing fossil fuels. At Avioxx, syngas conditioning is not a by-product but the foundation of the fuels we create and the decarbonisation future we are building.