Gowanus Canal kelp farm celebrates its first commercial harvest

On Thursday evening, a small, underwater farm in Gowanus celebrated its first harvest. The crop, 20 pounds of dried kelp, was stored in burlap sacks hanging from the rafters of an old, disused barge.

The RETI (Resilience, Education, Training and Innovation) Center, an environmental organization modeling climate adaptations, has been growing the kelp since December in Gowanus Bay, located at the mouth of the infamously polluted canal.

The project offers a natural means for cleaning the decades of industrial contamination infused in the waterway. But RETI is also marketing its harvest as an ingredient in “kelp-crete” – a stronger, less carbon-intensive alternative to conventional Portland cement. Concrete manufacturing currently represents 8% of global emissions, or twice that of all plane travel.

But the decision to monetize it has created some polite division among NYC’s kelp farming community (Yes, that’s a thing).

“We didn’t really have any expectations,” said Tim Gilman-Sevcik, executive director of RETI, which is headquartered in Red Hook. “We try a lot of things without knowing if they’re going to succeed, and oftentimes they don’t succeed at all. This has been a pretty amazing success.”

Kelp has been grown around the world far longer for food, or to be processed as a binding agent in toothpaste and cosmetics. But after more than a century of industrial abuse, the Gowanus Canal produces kelp so toxic even animals cannot eat it, and volunteers could only touch the seaweed with rubber gloves on Thursday.

That, according to Gilman-Sevcik, is exactly the point.

“There’s an uptake of the heavy metals and some of the other toxins that are in the water that get trapped into the kelp,” he said. With every frond harvested, Gowanus Bay grows a little cleaner.

This year alone, investments in commercialized kelp — a common,…