Rather than replacing blast furnaces, as many decarbonisation efforts have tried, Helix converts the waste CO2 back into carbon monoxide and feeds it into the furnace, where it does the chemical work of stripping oxygen from iron ore. Co-founder and CEO David Brown argues any attempt to decarbonise steel without tackling the blast furnace will not work.

The key technical claim is that the company's electrolyzer, a device that uses electricity and a catalyst to remove an oxygen atom from CO2, can handle a blast furnace's entire raw exhaust stream. Most electrolyzers only work on purified, concentrated carbon dioxide, so exhaust normally needs processing first.

Iron producers using the injected carbon monoxide can burn less coke. How much less is still debated: some scientific papers suggest up to 90% could be eliminated, others 30% to 40%. Helix proposes starting by replacing 33% of coke, which it says would save producers $14 per ton of iron in a famously thin-margin, $2 trillion industry.

To earn revenue sooner, Helix plans to target the specialty chemicals industry first, making chemicals on-site from waste streams without needing to capture the CO2 first. Brown also notes the sector moves slowly because blast furnaces can last over 100 years.