Did you know that for 50 percent of the breaths you take, you have the oceans to thank? Scientists believe that marine phytoplankton are responsible for more than half of the oxygen in Earth’s atmosphere! Photosynthesis from marine organisms is what originally made all life on Earth possible—and now, it may be the thing that helps keep global warming at bay. This is because phytoplankton, also known as marine microalgae, have the potential to provide us with two other things that we desperately need: a mechanism for carbon sequestration, and a source of sustainable energy.

The potential for carbon sequestration comes from the fact that marine microalgae are photosynthetic, meaning that they require light, water, and carbon dioxide to create the nutrients necessary for growth. Culturing large swaths of this algae would create a carbon sink, a reservoir that absorbs more carbon than it releases. This can be likened to planting a new grove of trees. But, unlike trees, microalgae is a highly productive species—they can double their mass on a daily basis, resulting in a growth rate up to 100 times faster than terrestrial plants.

An artist's depiction of algal farms in an arid environment adjoining the sea (Source: Greene, C.H., et al. 2016. Marine microalgae: climate, energy, and food security from the sea. Oceanography 29(4):10-15).


Marine microalgae could also be grown on otherwise non-productive, arid land, by using specialized growth chambers such as those illustrated above. This avoids the issue of land competition, since no food crops could be grown in these places. What’s more, marine microalgae do not require freshwater—an expensive and increasingly scarce resource. Instead they thrive on salt water, of which there is plenty (the ocean covers 71 percent of the Earth’s surface). Ribbons of algal cultivation facilities could be built along the shores of desert regions, which have otherwise unproductive land but plenty of sunlight and access to seawater.

Aside from its carbon sequestration benefits, microalgae could also become a major new source of energy in the form of biofuel. The potential use of algae for biodiesel has been studied extensively, since it is a renewable, eco-friendly alternative to fossil fuels. One of the largest research facilities is located in Koana, Hawaii, and is owned by the company Cellana. This center has demonstrated that algae can use photosynthesis to efficiently convert carbon dioxide into important oils and biomass, which can then be converted into feedstocks to produce Omega-3 fatty acid oils, animal feed, and biofuels.

 
Source: Modified for educational purposes by C.H. Greene from original figure produced by Cellana, LLC.     

There have been some apprehensions, however, which have slowed the progress of algal biofuels. One is that total liquid fuel demand in the United States is incredibly high; many believe algal biofuel will never be able to meet the demand. In 2016, the demand for liquid fuels was approximately 19.6 million barrels per day. Data collected from the Kona demonstration center shows that the productivity of algae is about 0.5 barrels/hectare per day. From these numbers, it is possible to calculate the approximate land area needed to grow enough algae to meet the United States’ liquid fuel demand: 151,352 square miles of land, or about 4 percent of the total U.S. land area (equivalent to about half the size of Texas). To put this in perspective, about 17 percent of U.S. land is currently being used to grow crops. Devoting 4 percent of U.S. land to growing algae might be a stretch, but it is not beyond the realm of possibility, especially if algal facilities are located in otherwise unproductive lands and designed to co-generate other useful products. Moreover, vehicle electrification and better fuel efficiency can help substantially reduce the need for liquid fuels, reducing the impact of biofuels production on the land.

One design developed by Cornell University professor Chuck Greene and his colleagues shows how algal farms could be set up as a combined, synergistic facilities, which could produce a variety of outputs other than just energy. For example, the algal ponds could serve as feed for an aquaponics center, allowing for sustainable fish farming. Additionally, another byproduct of this process would be raw protein; while this may not be a particularly useful output in America, where the average person has more than enough protein in their diet, there are many countries in the world where having a stable source of protein could mean saving lives.

What’s more, with the introduction of the Carbon Capture and Utilization Act of 2016, the cost of managing algal facilities would be greatly reduced. This program would grant tax credits for the capture and sequestration of carbon emissions from power generation and manufacturing, specifically to facilities that convert carbon dioxide into useable products and fuels, making algal biofuel facilities a perfect match.

Overall, algal facilities have the potential to fulfill many critical needs, and to create thousands of new jobs in the process. Continued research and development, both privately and publicly funded, can help bring down costs to make widespread algal farming a reality.

 

Author: Emma Dietz