It is ironic that wind turbine blades, which typically last for 25 years, have decidedly un-green deaths. The fiberglass blades are not recyclable, and when they are decommissioned, they're typically crushed and burned as both fuel and raw material for producing cement. The crushing process alone burns a lot of energy, and burning the crushed parts as fuel creates CO2.Enter Reverlast, a Finnish company that's come up with a unique way to repurpose the blades. Company co-founder Johannes Peace, an engineer and sailor, realized that the fiberglass blades are made the same way as boats. And like boats, wind turbine blades are specifically fabricated to weather a harsh marine environment for decades.What the company does is use the blades for useful waterborne applications. "We repurpose turbine blades to build floating docks and pontoon structures," says company co-founder Ossi Heiskala. "This reduces the need for traditional pontoon materials like concrete and polyethylene plastic, making the solution even more environmentally friendly. Our prototype dock prevents roughly 2.6 tons of carbon dioxide emissions, and the larger and more numerous the docks we build, the greater the impact."Peace and Heiskala launched Reverlast this year through Finland's Kiuas Accelerator, a startup incubator. For their first project, they're tackling a community sauna at Aalto University:The sauna itself is a traditional wood-heated barrel sauna, assembled from a pre-made kit. But instead of being placed on land, it will be installed on a dock that floats on pontoons made from four wind turbine blades. The pontoons are filled with polystyrene, and each weighs over 300 kilograms. The dock is more stable than a traditional floating pontoon dock and extremely durable. The fibreglass layer in the blade sections used for the pontoons is up to 6 centimetres thickfar more robust than the 1-centimetre layer typical in sailboats. "The pontoon is incredibly strongit won't break, that's for sure. Our job is to design the other parts to ensure they'll last for decades as well," says Heiskala. The dock pontoons were cut from the midsection of the blade. The narrow tip of the blade, in turn, could be used for lighter structures, such as swimming platforms, Heiskala envisions. "We're starting with floating docks because our team has a lot of expertise in that area. However, we already have more ambitious plansthe sturdier sections of the blades could be used for larger structures, like breakwaters," he explains. The sauna should be ready by next spring. And as they grow, Reverlast will have no shortage of raw materials: Ten to 20 turbine blades are decommissioned each year, and that number is scheduled to grow in the next decade. Wind turbine operators, who are responsible for the cost of decommissioning the blades, will be happy to have them taken off of their hands.