At Oregon State University, chemical engineering professor Greg Rorrer’s work with diatoms has garnered interest ranging from National Geographic to the National Science Foundation, which recently awarded his department a $2 million grant. Diatoms are a type of algae—tiny, photosynthetic organisms—with shells of glass. Under a microscope, they appear in a startling array of shapes from pyramids and snowflakes to mandalas and lozenges. But it’s not their beauty that has researchers interested—rather, it’s their potential use in biofuel.
Unlike common biofuel crops such as corn, canola, or soybeans, diatoms grown on a commercial scale wouldn’t require acres of valuable farmland and tons of fertilizers and pesticides. Even better, diatoms can act as little biochemical factories, churning out valuable materials such as titania and glucosamine. This makes them far more economically viable than a low-cost crop like corn.
Biomineralization is one of the diatom’s greatest tricks. Diatoms take minerals dissolved in water and process them; typically, they use dissolved silicon to create their glass-like shells. This ability can be altered to mineralize other common elements, such as those used in the electronics industry. Rorrer has already managed to create an organism that manufactures titania, a mineral used in high-performance solar cells.
“We’re trying to see if a diatom could make a solar cell biologically,” said Rorrer.
The body of a diatom consists of lipids, or fats, which allow the organism to move up and down in the water. These lipids could be converted into biofuel, a high-volume, low-value product. Diatoms that also produced titania, a low-volume, high-value product, would make the pursuit of biofuel economically viable.
“We’re looking for a third product,” Rorrer noted. “Some species take the sugars that any photosynthetic organism would make and convert those sugars to a special type of polymer.”
For instance, diatoms also produce chitin, a substance that can be broken down into glucosamine, used for everything from a natural health supplement to a coating on sutures. Taken from diatoms instead of shellfish, it also becomes a vegetarian/vegan-friendly product.
Overall, Rorrer’s vision is a photosynthetic biorefinery that uses each part of the diatom for a specific purpose, using only sunlight, water, and carbon dioxide.
“The cell is like a little factory that takes all those raw materials and processes them into these high-end end products,” he said. “It’s totally sustainable.”
In Rorrer’s lab, researchers grow diatoms in containers no bigger than 12 liters, each containing several billion organisms. Growing diatoms on a large scale could be achieved inside factories with tightly controlled levels of lighting and nutrients. The organisms need water—but it doesn’t have to be the cleanest water. In fact, diatoms could subsist on otherwise unused saline aquifers.
“Even if it’s polluted, these organisms can handle it,” said Rorrer, who has in the past studied diatoms’ ability to remove munitions from a water supply.
Some diatoms replicate in a single day, so there is no limit in terms of growing seasons or harvests. Overall, Rorrer’s hoping to create a framework of knowledge that proves useful for industries such as aeronautics, which is limited when it comes to alternative fuel sources as airplanes cannot currently run on electric power.
“We’re out to explore fundamentally different ideas that may change the way you look at these types of problems,” said Rorrer.
Turning one of the most abundant life forms on the planet into a source of biofuel and other profitable byproducts would achieve just that.
By Jen Matteis