Figure 1. Swomitra Mohanty, pictured with beakers of algae, is part of a team that developed a jet mixer for turning algae into biomass using much less energy than other methods. Source: Dan Hixson, University of Utah College of Engineering.A specially designed jet mixer underpins a method to turn algae into biocrude oil more economically, say researchers at the University of Utah (UU), Salt Lake City.
Current methods to extract oil-rich lipids from algae require an energy-intensive process in which water is pulled from the algae first, leaving either a slurry or dry powder. That residue is then mixed with a solvent where the lipids are separated from the biomass. What’s left is the biocrude, used to produce algae-based biofuel. However, the water extraction requires so much energy that the process uses more energy than the resulting biocrude provides. Therefore, turning algae into biofuel thus far hasn’t been practical, efficient or economical, explains UU chemical engineering assistant professor Swomitra Mohanty.
The team’s extractor process cuts energy consumption and thus improves the prospects for making algae-based biocrude. It involves a reactor that shoots jets of solvent at algae, creating a localized turbulence in which the lipids “jump” a short distance into the stream of solvent. The solvent is then extracted and recycled for reuse in the process. An article in Chemical Engineering Science X contains more detail.
“Harvesting has typically been the most energy-intensive part of algal biofuel production. Use of impinging jet mixers accomplishes the extraction at ambient temperature and pressure, is exceedingly fast (fraction of a second), and uses less-toxic solvents in comparison to alternative techniques. This is the trifecta of extractive harvesting,” says Mohanty.
“The key piece here is trying to get energy parity. We’re not there yet, but this is a really important step toward accomplishing it,” adds Leonard Pease, a member of the research team. “We have removed a significant development barrier to make algal biofuel production more efficient and smarter. Our method puts us much closer to creating biofuels energy parity than we were before.”
While current research is still at bench scale, the team now is exploring expanding the use of the confined impinging jet mixers for processing other microorganisms, including bacteria and fungi, with lipid oil and potentially partnering with industrial firms for scale-up of the technology. “We have plans to start this work and are preparing proposals to fund it. Ideally, we hope to start additional studies this fall,” notes Mohanty. “Depending on the funding available, this could be scaled-up in the few years.” Their work already has attracted interest from domestic and overseas companies.
Achieving a scale suitable for industrial use doesn’t pose any issues, notes Mohanty. “Overall, we see no reason why the technology could not be proven outside the lab and scaled up,” he adds. “Scalability was an initial factor in selecting this impinging jet mixer design over others. However, a rigorous evaluation of scalability has not been performed. In addition, a full-scale design hasn’t been built or optimized, so additional technical development would be required. However, the initial costs of the system we published was modest.”
Mohanty admits that other portions of the biofuel production process remain a challenge. “Each step needs optimized as a holistic system. We have additional innovations in the pipeline, so stay tuned,” he concludes.