Spanish Winery Converts Fermentation CO₂ Into Renewable Methane

A team of researchers and wine industry partners has demonstrated at a Spanish winery that carbon dioxide released during fermentation can be captured on site and converted into renewable methane, offering a new way for wineries to cut direct emissions and produce fuel from a waste stream.

The work was presented at Enoforum 2026 in Zaragoza by Andrés Sanz-Martínez and colleagues from the CIRCE Research Center for Energy Resources and Consumption, Rovira i Virgili University and the wine group Gonzalez Byass. The demonstration took place at Viñas del Vero in the Somontano region of Aragon, Spain, as part of the European Union’s FUELPHORIA project, which is testing industrial uses for carbon captured from food and beverage processes.

Wine fermentation releases large amounts of biogenic CO₂ during alcoholic and malolactic fermentation. In most wineries, that gas is vented directly into the atmosphere. The project’s goal is to intercept that stream, purify it and turn it into a usable energy product at the same site where it is produced.

According to the researchers, the system installed at Viñas del Vero captures CO₂ from multiple fermentation tanks, purifies the gas to 99.95% and compresses it for storage. The process then combines the captured CO₂ with green hydrogen produced by electrolysis. In a two-stage methanation reactor, the gases react to form methane, or CH₄, which can be used as a renewable fuel.

The partners said the system was designed for winery conditions, where CO₂ production is concentrated during the grape harvest and fermentation season rather than spread evenly throughout the year. They described the unit as modular and scalable, so it can be adapted to different production volumes and seasonal operating patterns.

During the 2025 harvest, from Sept. 9 to Sept. 26, the winery recovered 17 metric tons of CO₂, according to the presentation. Part of that captured gas was then fed into the methanation demonstration unit. Tests using the real fermentation gas produced an outlet stream containing about 80% CH₄ on a dry basis and reached a CO₂ conversion rate of 90%. The reactor operated continuously for more than 300 hours without observed catalyst deactivation, a result the researchers said points to stable performance under working winery conditions.

The methanation system uses nickel-based catalysts, which the project team said were selected for their activity and stability in converting CO₂. Maintaining stable reactor performance is a central issue for this kind of technology because winery gas streams can vary during harvest and because methanation is sensitive to temperature control. The researchers said ongoing work is focused on improving thermal management so conversion can move closer to the thermodynamic limit and on validating numerical models to support future optimization and scale-up.

The project also points to other uses for captured CO₂ inside the winery before or alongside conversion to methane. The presentation said the gas can be used to mix solid and liquid phases during red wine production, which may improve homogenization while lowering electricity use. It can also be used to inert tanks and presses by displacing oxygen, a step that can help limit microbial growth and oxidation risks. Another application under evaluation is acidifying wash water to improve cleaning efficiency and reduce water consumption. The team also cited the possibility of recovering volatile aromatic compounds carried in the CO₂ stream and returning them to the wine.

Those additional applications are important because they show that captured fermentation gas can have immediate process value even before it is upgraded to fuel. For wineries, which face increasing pressure to reduce emissions, energy use and water consumption, that could make carbon capture more practical if several benefits can be combined in one system.

The researchers described the Viñas del Vero installation as the first integrated CO₂-to-CH₄ system operating in a winery in Europe. That claim, if sustained as more projects emerge, would place the Spanish demonstration at the front of a growing effort to apply carbon circularity technologies to agriculture and food processing rather than only to heavy industry.

The broader idea behind the project is to treat fermentation CO₂ not as an unavoidable emission but as a raw material. Methane produced from captured biogenic CO₂ and renewable hydrogen can be used locally for heating, process energy or potentially vehicle fuel, depending on purification and regulatory requirements. In a winery setting, that could help offset purchases of fossil natural gas while also reducing the climate impact of fermentation.

The project’s backers are working in a sector where decarbonization can be more complex than it appears. Wine production includes emissions from vineyards, fertilizers, glass, transport, refrigeration and processing equipment, but fermentation itself is one of the most visible point sources inside the cellar. Because the gas is released in concentrated bursts from tanks, it can be easier to capture than more diffuse emissions elsewhere in the value chain.

The challenge is economic and operational as much as technical. A winery’s harvest window is short, and equipment must fit around production demands that leave little room for disruption. Any carbon capture and fuel conversion system must also prove it can operate safely, reliably and at a cost that wineries can justify. The 2025 harvest trial did not settle those commercial questions, but it did provide evidence that the chemistry can work under real harvest conditions rather than only in a laboratory.

The results presented in Zaragoza drew on collaboration between energy researchers, chemical engineers and winery operators, reflecting the fact that the project spans several disciplines. CIRCE is based in Zaragoza, while the university team is from the Department of Chemical Engineering at Rovira i Virgili University in Tarragona. Viñas del Vero, part of Gonzalez Byass, hosted the demonstration in Barbastro, in northeastern Spain.

The work comes as wineries across Europe face stronger sustainability expectations from regulators, retailers and consumers, alongside pressure from drought, heat and rising energy costs. In that context, technologies that can cut emissions and produce usable energy on site are attracting more attention, especially if they can be integrated into existing winery operations without major changes to winemaking itself.

For now, the Viñas del Vero project remains a demonstration, but the data reported from the 2025 harvest give the industry one of its clearest case studies yet of how fermentation emissions can be captured and turned into renewable fuel within a commercial winery.