Biosphere Daily Earth Science Repost

Kelp farming – Commercial algae

The mention of algae conjures up images of slime in warm, summer lake-water, or perhaps toxic algae blooms that result in massive fish kills. Yet, the largest algae species on earth is giant kelp. Kelp is the anchor species for coastal marine ecosystems off the coast of California. But growing kelp is also a commercial enterprise. Kelp farming not only provides needed food, but it also bolsters carbon sequestration.   

Kelp has no roots. Instead, it attaches to rocks on the seafloor via a structure called a “holdfast.” From that holdfast, it can then tower more than 100 feet off the bottom, growing at rates of up to two feet a day. Kelp has a trick to keep it upright. Attached to every blade (leaf) on the plant is a gas-filled pod. Thus, buoyancy naturally sends the plant towards the ocean’s surface, keeping it upright.

Who eats algae?

Farming algae requires a commercial market to sell the final product. That market is larger than many might suspect. Kelp is consumed by humans, processed for various chemicals, and also used as animal feed. Take a trip to your local health-supplement store, and you will probably find kelp powder on the shelves. Then there is toothpaste, shampoo, salad dressings, and more that use products derived from kelp. Around 150,000 tons of kelp are harvested from California waters each year. 

Researchers found that by adding kelp to animal feed, they cut a cow’s methane production by 60 percent. Each year livestock pump out enough methane to equal the warming capacity of 7 gigatons of carbon dioxide. So, a little kelp could go a long way in combating global warming. 

How to farm kelp

Harvesting from kelp forests involves taking off the top four feet of the kelp plants and then returning when the plants reach the surface again, thus allowing several harvests each season. The process is sustainable and preserves the kelp forest ecosystem. It is also regulated by the State of California to ensure that commercial kelp beds are a sustainable resource for future generations. 

But companies are working on more innovative farming techniques. Off the coast of California, an experimental kelp elevator is testing new ways to farm the ocean. Kelp is attached to a large PVC structure, which in turn, is attached to a solar-powered buoy. During the day, the kelp is suspended near the surface to receive sunlight for photosynthesis. However, at night the buoy lowers the PVC structure to depths of 260 feet. 

This change in depth also corresponds to a change in temperature. The deeper water is colder than at the surface, but it is also richer in nutrients than the surface water. During the nights, the kelp absorbs the nutrient-rich water. Then during the day, the combination of sunlight and extra nutrients allows the kelp to grow faster than if it stayed at the surface. Kelp on the elevator grew three times faster and weighed four times more than kelp kept growing at the surface.

Kelp plants are algae with environmental and commercial value. Maintaining existing kelp forests, re-growing old ones, and creating new open-water habitats all make sense. Recreational divers and surfers benefit along with commercial interests. Sustainable, productive ecosystems are a win for everyone.


California kelp forests: Ecosystems in distress (Source: ArcheanWeb) –  Also:


Giant Kelp (Macrocystis pyrifera) (Source: Oceana) –  Also:

California’s critical kelp forests are disappearing in a warming world. Can they be saved? (By Todd Woody; National Geographic) –  Also:

How do people use kelp? (Source: NOAA) – Also:

Seaweed could make cows burp less methane and cut their carbon hoofprint (By: James Temple; MIT Technology Review) –  Also:

Giant Kelp (Source: California DFG) –  Also:

Feature Image: Kelp Forest (Modified) – By NOAA’s National Ocean Service – Kelp Forest, CC BY 2.0,  

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.