Most vertical farms grow greens like lettuce or spinach, but a facility in a remote corner of Iceland, run by a startup called Vaxa Technologies, grows microalgae instead. A new study found that the farm’s process is carbon neutral.

The farm is on the site of a geothermal power plant, so it can run on the plant’s renewable energy. It uses natural carbon emissions from the power plant to help the algae grow. The geothermal plant also heats up water, so the farm can hook into its system of hot and cold water to regulate the temperature of the algae. “If you take a shower in Reykajavik, the hot water in your shower came from the same power plant,” says Isaac Berzin, cofounder and chief technology officer of Vaxa Technologies (not to be confused with Vaxa, another vertical farm in Iceland that does grow lettuce; vaxa, in Icelandic, means “grow”).

The new study, led by a researcher affiliated with Cambridge University’s Global Food Security Research Center, calculated that the farm uses so few resources that it has no carbon footprint. The algae, a type called spirulina, also has a nutritional profile rivaling beef; with iron, all essential amino acids, and, because of the specific way the company grows it, vitamin B12. If someone eats 1 kilogram (2.2 pounds) of the algae instead of 1 kilogram of beef, the researchers found, they could avoid 100 kilograms (220 pounds) of greenhouse gas emissions.

The indoor, vertical farm is better for the environment than traditional methods of growing algae in open-air ponds, says Berzin, who started working with algae more than two decades ago, originally in an attempt to make biofuels. (His previous company, GreenFuel, shut down in 2009 because algae-based fuel couldn’t compete with cheap fossil fuels.) Growing outdoors uses large amounts of water, and has a much larger carbon footprint because of the use of fertilizer and processing equipment, despite the fact that algae takes in CO2 as it grows. It also uses far more land.

Growing algae indoors has another advantage: It’s possible to tweak the environment to help boost its nutritients. The glowing pink lights in the farm improve the vitamin content. “If you cultivate your algae with [a] specific wavelength of light . . . you can ‘push a knob’ on the algae to produce B12 that the sunlight doesn’t push,” says Berzin. Algae grown in sunlight has a “pseudo B12” that humans can’t easily digest, but lab tests confirmed that the indoor-grown algae contains methylcobalamin, a form of B12 that is easily absorbable.

The startup currently grows 120 metric tons (132 U.S. tons) of the algae per year and sells it as an ingredient to be used in food or supplements. (They are scaling up to 400 metric tons per year, and have capacity for as much as 20,000 metric tons of production a year at the current location.) Locally, in Iceland, one restaurant uses it in smoothies—naturally blue from the algae—and in pizza crust, with an extra dollop of algae sauce as a topping. Unlike some other forms of algae, it tastes neutral and doesn’t have a fishy flavor, Berzin says. It could also potentially be used in plant-based meat to help improve nutrition. In the U.S., another startup, Triton Algae Innovations, is also producing microalgae, which is beginning to be used in fake meat products like Tofurky.