Energy-efficient biocrude extraction

Chemical engineers have created a more rapid and energy-efficient method of converting algae to biocrude, a synthetic fuel.

Inside microorganisms such as algae are lipids, fatty acid molecules that can be extracted to power diesel engines. But so far, energy required to extract lipids and turn algae into this biocrude is more than the amount of energy it gives back.

Dr Leonard Pease, co-author of the findings, said: “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.

“The key piece here is trying to get energy parity,” he said. “We’re not there yet, but this is a really important step toward accomplishing it.”

Pease and his team of engineers at the University of Utah developed a new mixing extractor that shoots jets of the solvent at jets of algae. This creates a localised turbulence in which lipids “jump” a short distance into the stream of solvent.

Biocrude is used to produce algae-based biofuel. That fuel is combined with diesel fuel to power long-haul trucks and other machinery.

Current methods to involve extracting water from the algae to form a residue. Most of the energy is expended during this stage of the process. That residue is then mixed with a solvent to separate the lipids.

Co-author Swomitra Mohanty said: “Our designs ensure you don't have to expend all that energy in drying the algae and are much more rapid that competing technologies.

With the new technique, algae could be effectively harvested to produce an abundant, sustainable and natural fuel source that removes CO2 from the air. The process could be applied to a variety of microorganisms such as bacteria, fungi, or any microbial-derived oil.

In 2017, about 5% of total primary energy use in the US came from biomass, according to the US Department of Energy.

The engineers’ findings were published in Chemical Engineering Science X.