Denmark-based biotech start-up Again is using gas fermentation technology to convert industrial carbon dioxide (CO2) emissions into chemicals and fertilisers, aiming to enhance industrial resilience and reduce carbon emissions in chemical supply chains.
Speaking at gasworld’s European CO2 Summit 2025 in Rotterdam, the Netherlands, Harshvardhan Khotia from Again explained the company’s three-stage gas fermentation process, which utilises specialised bacteria to transform CO2 emissions into commercially useful products.
The start-up is moving towards commercial-scale deployment. Following over 10,000 operational hours at its pilot plant near Copenhagen, Denmark, Again is building its first full-scale facility, TXS-1, in partnership with Finnish energy group Helen and an undisclosed chemical company. The facility will produce glacial acetic acid, commonly used in paints, lacquers, and varnishes, as well as ammonium sulphate fertiliser.
“We have signed an off-take agreement with Helen for all the acetic acid produced,” Khotia said, adding that the 10-year deal provides off-take certainty for up to 50,000 tonnes of acetic acid production annually, supporting Again’s commercial rollout.
Again has a flexible business model, offering both build–own–operate facilities and technology licensing tailored to site-specific needs. Khotia noted that facilities could become fully operational within 15 to 18 months from sign-up.
The process requires CO2 and hydrogen, with hydrogen needing 95% purity at a hydrogen-to-CO2 ratio of 1:10. Again said it adapts its solutions according to the purity of the available CO2 at each site. The modular design of Again’s bioreactors allows installation without disrupting existing operations, integrating with standard downstream processes such as distillation and crystallisation.
“Emitters can now convert their waste gas emissions into high-value products,” Khotia said.
According to the latest market research, glacial acetic acid, just one of these high-value products, is expected to hit sales with a global value of approximately $16.5bn by 2034, from $8.8bn in 2024.
