Seaweed Aquaculture: An Answer to Sustainable Food and Fuel?

When copying the model of land-based industrialized farming, current aquaculture practices can have many of the same negative environmental impacts inherent in industrial-scale agriculture.

U.S. aquaculture operations, primarily producing shellfish, are subject to stringent environmental regulations. But due to the poorly regulated use of high amounts of chemicals and antibiotics to maintain massive, centralized monocultures of fish and shrimp particularly in South America and southeast Asia, aquaculture farms have gained a reputation for polluting water and producing poor-quality food.

But it doesn’t have to be this way. The Atlantic had a fantastic piece this week on the growing movement to clean up aquaculture operations — producing better food, sustainable biproducts, and making them a solution to environmental problems:

Unsurprisingly, once information got out among the general public, “aquaculture” quickly became a dirty word. Industry responded with a strategy of mislabeling seafood and upping their marketing budgets, rather than investing in more sustainable and environmentally benign farming techniques.

But a small group of ocean farmers and scientists decided to chart a different course. Rather than relying on mono-aquaculture operations, these new ocean farms are pioneering muti-tropic and sea-vegetable aquaculture, whereby ocean farmers grow abundant, high-quality seafood while improving, rather than damaging, the environment.

One of the keys? Seaweed. This type of algae, which can be used for everything from food to fertilizer, could be a major piece of creating a network of sustainable farming operations:

Seaweed farms alone have the capacity to grow massive amounts of nutrient-rich food. Professor Ronald Osinga at Wageningen University in the Netherlands has calculated that a global network of “sea-vegetable” farms totaling 180,000 square kilometers — roughly the size of Washington state — could provide enough protein for the entire world population.

The goal, according to chef Dan Barber — named one of the world’s most influential people by Time and a hero of the organic food movement — is to create a world where “farms restore instead of deplete” and allow “every community to feed itself.”

But here is the real kicker: Because they require no fresh water, no deforestation, and no fertilizer — all significant downsides to land-based farming — these ocean farms promise to be more sustainable than even the most environmentally-sensitive traditional farms.

Along with being a fantastic source of food, seaweed could be a substantial feedstock for biofuels production. A lot of research has been done on seaweed as a biofuel source, and some pioneers are beginning to farm it for energy production. And while there are no seaweed-based biofuels being produced at commercial scale, there are a lot of good reasons to continue pursuing it.


Firstly, seaweed is not a major source of food globally. And it’s also one of the fastest growing plants in the world. It can grow 9–12 feet in three months. Additionally, fifty percent of seaweed’s weight is oil, so we would theoretically only need to set aside three percent of the world’s oceans for seaweed farming to meet world energy needs.

If you compare efficiency of algae as a fuel source to other proven sources, there’s no comparison. Soy produces 40 to 50 gallons of biofuel per acre, rapeseed between 110 and 115, mustard 140, and palm oil 650. Algae, on the other hand, has the potential to produce 10,000 gallons of biofuel per acre. And most importantly, seaweed can absorb five times more carbon dioxide than land-based plants.

The Atlantic explores the potential for seaweed-based biofuels further:

Finding a clean replacement for existing biofuels is becoming increasingly urgent. A report commissioned by the European Union found biofuels from soy beans can create up to four times more climate-warming emissions than equivalent fossil fuels. Biofuels have also forced global food prices up by 75 percent — far more than previously estimated — according to a confidential World Bank study. And a recent report from the International Food Policy and Research Institute, warned that U.S. government support for corn ethanol was a major factor behind this year’s food price spikes.

Seaweed and other algae is increasingly looking like a viable substitute. About 50 percent of seaweed’s weight is oil, which can be used to make biodiesel for cars, trucks, and airplanes. Scientists at the University of Indiana recently figured out how to turn seaweed into biodiesel four times faster than other biofuels, and researchers at the Georgia Institute of Technology have discovered a way to use alginate extracted from kelp to ramp up the storage power of lithium-ion batteries by a factor of ten.

The Pentagon has taken a special interest in seaweed and other algae-based biofuels as well. In the words of Alan Shaffer, the Pentagon’s principal deputy director of defense research and engineering: “The beauty with algae is that you can grow it anywhere and to grow it needs to absorb carbon dioxide, so it’s not only a very effective fuel, in theory it’s also a carbon sink. That’s a pretty good deal.”

A pretty good deal indeed.

– Cole Mellino is an intern on the energy team with the Center for American Progress. Climate Progress blogger Stephen Lacey contributed to this story.