Until now, aluminium production has generated significant greenhouse gas emissions. But a new process is emerging that produces aluminium without such emissions.
By Georg Mathisen - Published 28.10.2026
The method is 140 years old, and it is time to modernize in order to reduce climate emissions. October 19th marked an important milestone in this direction at Hydro’s Herøya aluminium research centre, Norway.
“In very simple terms, this is an alternative process for producing aluminium,” says Egil Skybakmoen, a research manager at SINTEF.
One kilo of aluminium results in 1.5 kilos of emissions
The technology currently used to produce aluminium was invented as far back as 1886. The process uses electricity to trigger a reaction between aluminium oxide—also known as alumina—and carbon through electrolysis, resulting in the formation of aluminium. The primary by-product of this process is carbon dioxide (CO₂), which is released into the atmosphere.
What is electrolysis?
Electrolysis is a chemical process in which a direct electric current is used to drive a chemical reaction that would not occur spontaneously.
Here’s what happens during the process:
- An electric current is applied and passed through the liquid via electrodes.
- Positive ions in the liquid move toward the negative electrode.
- Negative ions move toward the positive electrode.
- At the electrodes, ions either gain or lose electrons. This is how substances are separated from one another or new substances are formed.
Source: Store norske leksikon [Great Norwegian Encyclopedia (online)] /SINTEF
In the traditional process, “you end up with very high emissions. For every kilo of aluminium produced, one and a half kilos of CO₂ are released. This is a process that contributes a significant amount of CO₂ to the atmosphere,” says Skybakmoen.
The technology developed for CO₂ capture is not well-suited for use here. Current aluminium production methods result in CO₂ being mixed with large volumes of air.
Consequently, the CO₂ gas becomes so diluted that separating and collecting it would be extremely difficult and costly—although some projects are currently exploring this as well.
Operating in a closed loop
The primary objective of the new process is to avoid these greenhouse gas emissions. Skybakmoen explains that the concept behind the technology—which he and his colleagues at SINTEF and NTNU are developing in collaboration with Hydro—is not new:
“Another aluminium company, Alcoa, actually ran a pilot project using this process back in the 1980s. Now Hydro has revisited and further developed it,” he says. Hydro has patented its process.
Hydro, NTNU, and SINTEF have a long-standing and successful tradition of collaborating on a wide range of projects. In this particular project, NTNU has four doctoral students, with supervisors from both Hydro and SINTEF. Furthermore, SINTEF has held primary responsibility for two other sub-projects, as well as the construction and operation of the new laboratory at Tiller.
The new process is called HalZero. It converts alumina into anhydrous aluminium chloride through a chlorination process. The aluminium chloride is then broken down into chlorine gas and aluminium—that is, the metal itself. This takes place via electrolysis.
Here’s what happens in the chlorination process:
A process in which chlorine or a chlorine-containing substance reacts with another substance. Chlorination is used to modify a substance or to create a new one.
Source: SINTEF
New process produces no CO₂ emissions
The primary gases involved in the process are handled within closed loops. This allows them to be reused repeatedly, rather than being released. CO₂ is captured and converted into CO gas.
“The whole concept is that all the gases circulate in a loop, ensuring there are no emissions. It’s a very clever approach, but it’s also challenging. At SINTEF, we’re collaborating with NTNU and Hydro to explore this at a more fundamental level. Since January, Hydro has been demonstrating the technology through a pilot project at the Herøya research park in Porsgrunn municipality,” says Skybakmoen.
For its part, SINTEF has established a dedicated laboratory for the project at Tiller in Trondheim, where researchers are conducting fundamental studies in cooperation with NTNU.
Marking a key milestone at Herøya
October 19th marks the occasion of Hydro producing aluminium for the first time using the HalZero electrolysis technology—an event attended by Prime Minister Jonas Gahr Støre.
According to a press release from Hydro, the objective of the pilot project is to lay the groundwork for industrial-scale implementation of HalZero, with the ultimate goal of achieving net-zero emissions in producing primary aluminium.
“The studies and tests conducted so far indicate that an industrial-scale HalZero aluminium plant will require the same amount of energy and capital as an aluminium plant using current technology. The investment cost is also expected to be comparable,” says SINTEF researcher Skybakmoen.
The technology is being developed primarily to create new capacity. However, the long-term hope is that it can also be used when replacing outdated production lines, Hydro explains.
Enova has now granted an additional 82 million kroner for the project development of the next phase: an industrial concept pilot for HalZero.
Facts about the project:
- Hydro, SINTEF, and NTNU are collaborating on the ZEAL project to develop new technology for ZEro CO₂ Emissions in primary ALuminium production.
- Four PhD students are pursuing their doctorates through this project, which is funded by Hydro with support from the Research Council of Norway.
- The project began in 2022 and concludes this year. The partners have submitted a new application for funding from the Research Council of Norway and hope to resume activities in April 2027.