So far as feedstocks for the production of biofuels go, kelp is a highly promising one on many fronts, and a new technology promises to boost its credentials even further. Scientists at the University of Southern California (USC) have demonstrated how raising and lowering it in the ocean environment with a "kelp elevator" can significantly boost biomass yield, by maximizing its exposure to both sunlight and nutrients.
One of the key reasons kelp is seen as potentially greener source of biofuel is because unlike other feedstocks, such as corn, sugarcane or canola, it doesn't require any land to grow. This is good news for both the preservation of vital natural habitats that might otherwise be cleared away and farmers who can instead use their precious space for agriculture purposes. Further to that, it doesn't require freshwater, pesticides or fertilizer, instead growing naturally within the marine environment.
So much so, kelp is one of nature's fastest-growing plants, but raising it in controlled aquaculture settings raises a few challenges. The plant needs to be fixed to a substrate within sun-drenched waters to really thrive, but these parts of the ocean don't offer the same abundance of nutrients found in deeper waters. So the USC team came up with an idea to get the best of both worlds, called the kelp elevator.
The elevator consists of fiberglass tubes, stainless steel cables and horizontal beams, which are used to subject the kelp to depth cycling as the entire structure is raised and lowered. This was put to the test off the coast of California where over the course of 100 days, scientists raised the kelp species Macrocystis pyrifera to the sunny surface during the daytime and lowered to it depths of around 260 ft (80 m) at night, so it could soak up vital nutrients like nitrate and phosphate. Raising the kelp in this way saw it grow much faster, producing four times the biomass of regular kelp.
“The good news is the farm system can be assembled from off-the-shelf products without new technology,” said Brian Wilcox, co-founder and chief engineer of company Marine BioEnergy, which came up with the elevator. “Once implemented, depth-cycling farms could lead to a new way to produce affordable, carbon-neutral fuel year-round.”
Marine BioEnergy is now working on adapting its kelp elevator for use in open-ocean kelp farms. The research was published in the journal Renewable and Sustainable Energy Reviews, while the video below offers an overview of the research.
