Kelp can be harvested in the ocean and turned into carbon-neutral biofuel. Because kelp can grow more than a foot a day and is easy to process, the production can be cost-competitive with fossil fuels. A startup is using elevators to grow kelp farther out in ocean waters. The technology is currently being tested off the coast of California, and if successful, the startup wants to use similar technology to begin farming large tracts of the open ocean between California and Hawaii.