Kelp to Biofuel and Beyond for Mitigating Climate Change

We look to seaweed for carbon sequestration, biofuel, and more, as atmospheric and oceanic carbon dioxide levels continue to climb. Macroalgae agriculture could be a key tool in fighting climate change.

This insight placed third in our fall blog competition.

Below the ocean’s surface appears a band of floating ghouls along lines tethered to the bobbing buoys. As the apparitions sway back and forth in the waves, a vessel pulls them to the surface one by one. This imagery is ominous, however upon closer observation, the undulating figures are revealed to be unintimidating stretches of seaweed farmed in the Faroe Islands. These billowing biomasses of green and brown might be a solution to the present issue of rising atmospheric and oceanic carbon dioxide (CO2) levels associated with climate change.

Seaweed is not just some malodorous beach debris, nor the green film wrapped around your tuna roll; seaweed has the potential to sequester excess CO2 that can be turned into valuable biofuels, pharmaceuticals, bioplastics, animal feed, and nutritious food. Kelp, or macroalgae, can accomplish all this and more without additional land use for successful growth. There is potential to grow various seaweed species off the shores of all continents in every season.

Moreover, coastal waters are often already rich in fertilizer from agricultural runoff, so there is no need to supplement the water with additional nutrients. The ubiquitous use of fertilizer on individual properties and agricultural lands affects CO2 emissions because fertilizers are refined from petroleum. According to Ocean Rainforest, a pioneer in this burgeoning industry, if 1% of coastal shelves cultivate seaweed, 306 million tons of CO2 would be sequestered within 3,000 tons of seaweed. In other words, cultivation in the marine biosphere on a mere sliver of the world’s continental shelf area has colossal potential for sustainable resource and land use. 

Carbon sequestration normally invokes the image of luscious forests. Unlike their terrestrial counterparts, kelp farms can sequester carbon without the risk of forest fires. Seaweed aquaponics increases habitat for fish and other marine life, which promotes biodiversity vital for adaptation to climate change. Likewise, kelp absorbs unwanted excess nutrients from water, which often leads to eutrophication and dead zones, if unmanaged. Supporting local fish populations through seaweed is also important for fishing economies and jobs. To boot, these farms can reduce ocean acidification, which is killing the Great Barrier Reef.

Unlocking the potential of kelp farming supports the UN’s Sustainable Development Goals, particularly:

  • SDG 12: Responsible Production and Consumption
  • SDG 13: Climate Action
  • SDG 14: Life Below Water

According to Carlos Duarte, the head of Sea Research at King Abdullah University of Science and Technology in Saudi Arabia, seaweed farming operations can sequester ten times more carbon per hectare than the rainforests of the Amazon. With regard to climate change, macroalgae agriculture is carbon negative. 

Beyond its growth stage, seaweed can be useful to humans in the form of biofuels used in energy and heat generation, especially as we wean from fossil fuels. Though it is not yet more cost effective to cultivate seaweed than corn and soybeans, as researchers optimize and innovate seaweed farming practices these profit margins stand to improve.

Some species of seaweed yield 20 tons per hectare per year, whereas corn yields are about 10 tons per hectare per year and soybeans 3 tons per hectare per year. The species Saccharina Japonica, for instance, grows almost seven times faster than sugarcane. Compared to conventional biofuel crops, seaweed proves there is much more to be explored in this regard.

So, can seaweed save humans from the existential threat of climate change? Not quite yet. Barriers to expansion of this industry include raising awareness about seaweed’s multitude capabilities and increasing government support, access to farming permits, and emphasis on monetization of CO2 emissions to create a market for carbon sequestration.

Perhaps the U.S. Department of Agriculture, the Bureau of Ocean Energy Management, the Department of Energy, in collaboration with other federal organizations could establish grants for kelp farming ventures alongside existing opportunities. Currently the BOEM only leases continental shelf space for offshore wind. Coastal states that seek to engage with this new industry could likewise organize protocols for establishment of macroalgae farms including incentives such as tax credits. Pioneer farms represent an exciting opportunity to combine expertise in fields of business, marine biology, ecology, and farming. 

Sage Basri

Student Advisory Council Member
Sage Basri is a Kleinman Center Student Advisory Council Member and an undergraduate in the School of Arts and Sciences majoring in Environmental Studies. Basri was also a 2021 Undergraduate Seminar Fellow.