Seaweed: More than Just Weeds of the Sea

Fields of blacked-out solar planes, majestic white windmills that span rolling hills, vast electrical dams for hydropower… numerous solutions have been put forth to solve the climate crisis.

Enter seaweed.

The brown-green vegetation that infests murky waters and entangles the limbs of hapless swimmers, whose slimy carcasses spoil otherwise sandy white beaches… However, this unassuming water plant might just be the future of green energy.

Marc von Keitz, a program director at Advanced Research Projects Agency explains that “in order to achieve major decarbonization of the U.S. economy … bioenergy will need to make up 20% to 25% of the country’s energy sources.”

Currently, only 5% of total U.S. energy use comes from crops such as corn, wood, and soybeans. Corn-based ethanol dominates the bioenergy industry, yet the most common biofuel crops have major environmental drawbacks. They compete with other agricultural crops for limited land and freshwater while the fertilizers and pesticides used in their cultivation also pollute nearby lakes and rivers.

Instead, seaweed is the crown jewel of biofuels.

Seaweed harvested for biofuel is grown in salt or waste water, minimizing its environmental impact and reducing land-use conflicts. Photosynthesizing at a much faster rate than land-based plants, seaweed can capture up to 20 times more carbon dioxide per unit area. With less than half the carbon footprint of gasoline, it absorbs copious amounts of carbon as it grows, offsetting the minor emissions that are released when it is converted to biofuel.

Furthermore, seaweed biofuel yields can be maximized using genetic modifications. Most domesticated seaweeds have been modified to increase their capacity to store energy-rich compounds, such as triacylglycerol (a lipid) and starch. The lipids extracted from seaweed are turned into biodiesel, which can be used in diesel engines without the need for new adaptations. Similarly, extracted starches create bioethanol, fuel that can be used as a gasoline replacement in vehicles.

Previously, mass adoption of seaweed biofuel was difficult, as it required farms to be near coastlines for human operation. However, researchers have recently invented new methods of seaweed farming in the Pacific Ocean. Submarine drones are used to implement a technique called “depth-cycling”: seaweed is brought to the shallow waters during sunshine hours and subsequently lowered 260 feet at night. This allows the seaweed to photosynthesize during the day while absorbing necessary nitrates that are only available in deeper waters during the night. This technique has yielded four times more seaweed biomass than previous farming techniques. Further, solar panels power the submarines, which can drag the seaweed deeper during extreme weather events for protection while also taking the seaweed to specific harvesting locations when needed. Once implemented, the process is self-sustaining and can operate nearly unmanned.

Considering their immense benefits, seaweed farms are worth the investment. Cindy Wilcox, president of Marine BioEnergy, estimates that in order to “replace 10% of liquid petroleum fuels used in the U.S., we would need to have an area under cultivation about the size of Utah.”

Thankfully, there are 705 Utahs in just the Pacific Ocean alone.