Algae can be used for sustainable products, but you need enough of it — enough biomass — to do so. Researchers at Michigan State University say they've developed a way to more evenly distribute sunlight in algae cultivation systems, which leads to more algae growth.
Xinyue Liu is a co-author on a paper on the topic and an assistant professor in the department of chemical engineering and materials science at Michigan State University. She said as the algae thickens, lower layers will not receive sunlight, so they can’t photosynthesize and will not grow. The outer layers receive more sunlight than necessary.
“But when the algae is growing more and more, it’s becoming denser,” she said. “The sunlight, used to perform this kind of energy conversion, is a critical ingredient that can only reach a very thin layer near the surface.”
Growing algae may seem like an odd goal, especially as other projects attempt to reduce algae, but she said this type of algae is not toxic. She said this algae can be used for sustainable products.
“In this case, algae can be beneficial,” she said. “They are intentionally created to manufacture some new products, like proteins, food ingredients, omega-3, and lipids.”
Once algae begins to photosynthesize, some nutrients like nitrogen and phosphorus accumulate, which helps turn the sunlight, water, and air into proteins and carbohydrates. In the MSU experiments, these have been used to feed farm animals, like chickens.
Currently, LED lighting is used to increase algal biomass because it can spread the light needed for photosynthesis further into the layers, but that takes power.
“LED is indeed powerful in terms of generating higher biomass, but it also has a very high energy consumption,” she said.
The team chose to test how hydrogel optical fibers can be used to distribute natural sunlight. The fibers scatter the light further into the algae, instead of only on the surface layers. The researchers found it can increase the photosynthetic capability by up to six times.
“Basically, we do not consume any external energy,” Liu said. “Practically speaking, we do need to consider whether this system automatically generates a net carbon removal.”
Algae uses large amounts of carbon dioxide in its photosynthesis process, but Liu said they won't know if increasing the biomass capability will overall capture more carbon.
“It depends on the life cycles, how the algae is processed, how the products are made, and also how much energy is consumed throughout the entire process,” she said. But the process still removes the energy used from the LED lights, making it more sustainable than before, and that’s a good first step, she said.
Using the hydrogel optical fibers to scatter natural sunlight was also more effective. The energy efficiency of light to chemical energy was higher with the optical fibers than it was with the LED lights.
She said the optical fibers look like cords, and when the sunlight enters one side of the cord it doesn’t just exit the other end like traditional fibers. Instead, they designed them so light will exit multiple areas after entering, scattering them enough to permeate deeper layers of the algae.
Wei Liao, a professor in the department of biosystems and agricultural engineering at Michigan State University, was also involved in the study. He said algae is important globally.
“If you look at the global carbon cycle, algae play an important role in sequestering carbon on the front end,” he said. And on the back end, the algae can then be turned into sustainable products.
He said the research team can also use it for animal feed.
“We did feed chickens on Michigan State’s campus and they love it,” he said. “They love the fishy smell of the algae.”
He said lipids can be extracted from algae and used in biodiesel.
Liao said if the process becomes more efficient, the algae can capture more carbon while providing more sustainable products.
Liu said there are several next steps they can take with this research. She said they can use some of the carbon dioxide produced from MSU’s power plant to enhance biomass production. They can also scale up the production.
“Right now it’s lab scale products, about one-liter reactors in total size, which is fine for lab validation, proof of concept validation,” she said. “But maybe people want to see more in terms of scaling up and how it can benefit agricultural products. I think that’s scaling up into hundreds of liters or even larger than that.”
Algae has also been used to make plastics, pharmaceuticals and other products.
