Giant kelp is the planet’s largest species of marine algae. That makes it an attractive source for making biofuels. Now scientists have tested a new strategy for growing the plant that could continuously produce it on a large scale. The trick is to cycle the kelp stocks daily from the near-surface waters for sunlight to the deeper, darker waters for nutrients.
Today’s energy crops, like soybean and corn, require land, freshwater, and fertilizer. Kelp doesn’t, and it can even grow over a foot a day under ideal conditions. The challenge is getting it to achieve this potential.
Kelp typically grows in shallow areas near the coast, thriving only where both nutrients and sunlight are plentiful. However, the ocean’s sunlit layer extends about 665 feet (200 meters) or less below the surface, but this zone frequently doesn’t contain sufficient nutritional elements to support kelp growth.
Most of the surface of the open ocean is nutrient-poor year-round. In coastal areas, upwelling occurs – when deep water rises to the surface, bringing nutrients – but the event is seasonal. On the other hand, deeper water is rich in nutrients but lacks the necessary sunlight.
Fortunately, the new study demonstrated that kelp could withstand day-to-day alterations in water pressure of a cycle going between 30 feet (9 meters) deep to 262 feet (80 meters) deep. The team used a custom-made “kelp elevator” to cycle the plants. It was anchored on California’s Catalina Island, near the USC Wrigley Marine Science Center, and powered by solar energy.
The researchers’ cultivated kelp acquired sufficient nutrients from the deeper, dark environment to create a quadruple the growth than kelp that they had transplanted to a native coastal kelp habitat. This is excellent news because making biofuels from kelp or other marine plants would be far more sustainable, scalable, and efficient than terrestrial plants.
Producers can also convert marine biomass into different forms of energy, like ethanol, which could replace the corn-derived additive currently blended into US gasoline. However, bio-crude (oil derived from organic materials) is probably the most appealing end-product.
Bio-crude, produced through hydrothermal liquefaction (which utilizes heat and stress to transform materials like algae into oils), can be processed into bio-based fuels in existing refineries. It can be used by planes and trucks. Biofuels would be ideal since it isn’t practical to run long-distance transportation modes on electricity yet because they’d require gigantic batteries.
By the researcher’s calculations, producing enough kelp to power the entire US transportation sector would require using a tiny percentage of the US Exclusive Economic Zone – the ocean area from the coastline extending out 200 nautical miles.
Several unknowns remain, like could raising kelp on a large scale have unintended environmental consequences, and what would the processes for permitting and kelp regulating be? Nevertheless, the researchers believe marine biomass energy has the potential to help meet 21st-century sustainability challenges.