Students are learning about aquaponics and hydroponics at Ranken Technical College in Troy, Missouri. Nearly double-digit growth is expected in the indoor farming industry over the next decade, but high energy costs remain a challenge.

The sound of running water fills the lab as students navigate between large plastic tubs and styrofoam sheets holding green plants in one of the classrooms at Ranken Technical College’s campus in Troy, Missouri, outside of St. Louis.

Tilapia at different life cycle stages fill the blue tubs. Their water is then filtered to draw out nitrogen that passes through tubes to the other half of the room, where it fertilizes the various plants growing under bright lights.

Ranken’s facility is providing its students a chance to work in one of several indoor farming formats, many of which are popping up around the country and in Missouri. The U.S. is home to an estimated 2,000 indoor farms, and the industry is expected to grow at 9.8% annually between now and 2033. Though many of these facilities have appeared in recent years, the industry remains relatively small due to how new it is, said Nick Crosse, who teaches Ranken’s aquaponics class.