Lipid droplets before (left) and after (right) ultrasonic lysis | Photo courtesy of Los Alamos National Laboratory
The Department of Energy’s sustained investment in biofuels technology is unlocking the huge potential for homegrown oil from algae. As Niketa Kumar noted a few weeks ago, we now have an excellent idea about just how huge that resource is: an April report from the Pacific Northwest National Laboratory found that up to 17 percent of the United States’ imported oil for transportation could be replaced with American-grown biofuels from algae. Yet understanding that potential and realizing it are two different things.
One significant challenge of using algae is cheaply separating it from the very thing that allows it to grow: water. It’s well known that under most cultivation conditions, microalgae reach a typical cell density of less than 1 gram per liter of water; that’s 999 parts water to 1 part algae. Removing that quantity of water to get to the algae is an uphill battle. Adding to the problem is scale; the optimal size of the commercial “open-pond” algae production facility is envisioned at more than a million liters of culture each. This means the harvesting technology not only has to concentrate the algae cheaply and effectively, but it must do so at a robust flow-through rate.
Enter the team of Department of Energy researchers led by Babetta Marrone of Los Alamos’ Bioscience Division, who are taking this challenge head-on. Marrone’s team is busy perfecting the Ultrasonic Algal Biofuel Harvester, which modulates the frequency of sound waves to separate oils, proteins and water from algae.
The prototype harvester unit consists of a set of ultrasonic transducers attached to a compact multi-chamber box. The harvester works at select sound wave frequencies to focus and concentrate the fluid-borne cells within the device. The concentrated algae can then be exposed to different frequencies, to break open the cells, releasing the lipids; and then separate the oils, proteins and water from one another. Each unit process (algae concentration, cell disruption and separation of lipids) is being developed and optimized separately, with the eventual goal to integrate the three processes into a single device.
Currently funded by the National Alliance for Advanced Biofuels and Bioproducts (NAABB) algae consortium, initial support for this key invention was provided jointly in 2010 by the Office of Energy Efficiency and Renewable Energy (EERE) and industry partner Solix Biosystems.
“For commercial algae production, the acoustic separation and lysing devices have the potential to lower the cost of those unit operations by multiple orders of magnitude,” says Dr. Joel Bulter, CEO of Solix Biosystems. Butler adds, “This represents a truly game changing innovation with applications beyond the algae industry. The liquid-solid separations market is over $6 billion globally, and this technology has obvious applications in the waste water, dairy, mining, and beverage industries just to name a few. At Solix BioSystems we place a great value on our collaboration with LANL and we will continue to work together to bring this technology to market.”
Based on measurements of the lab scale devices tested so far, scientists at the Los Alamos National Laboratory believe that they can develop a portable, energy-efficient, ultrasonic algae harvesting device that can concentrate 25 gallons of algae per hour for less than a penny per gallon of lipid. Such an improvement would drastically reduce the cost of separating water from algae, bringing us a big step closer to realizing the huge potential to displace imported crude with homegrown algal oil.
The Department of Energy’s continued R&D investment in innovative technologies – like the kind that is enabling the development of the Ultrasonic Algal Biofuel Harvester – form a critical component of the Department’s broad strategy to ensure commercially viable, domestically-produced and sustainable alternatives to foreign oil. Innovations like this one will ensure that the clean energy we need to power the country can be produced right here at home.
Joyce Yang is Technology Development Manager for the Biomass Program in the Office of Energy Efficiency and Renewable Energy.