A fast way to turn algae to biocrude

University of Utah chemical engineering assistant professor Swomitra Mohanty, pictured with beakers of algae, is part of a team that has developed a new kind of jet mixer for turning algae into biomass that extracts the lipids with much less energy than the older extraction method. It is a key discovery that now puts this form of energy closer to becoming a viable, cost-effective alternative fuel.Photo credit: Dan Hixson/University of Utah College of Engineering

Physicists have discovered a new effect, which makes it possible to create excellent thermal insulators which conduct electricity. Such materials can be used to convert waste heat into electrical energy.

Biofuel experts have long sought a more economically viable way to turn algae into biocrude oil to power vehicles, ships and even jets. University of Utah researchers believe they have found an answer. They have developed an unusually rapid method to deliver cost-effective algal biocrude in large quantities using a specially-designed jet mixer.

Packed inside the microorganisms growing in ponds, lakes and rivers are lipids, which are fatty acid molecules containing oil that can be extracted to power diesel engines. When extracted the lipids are called biocrude. That makes organisms such as microalgae an attractive form of biomass, organic matter that can be used as a sustainable fuel source. These lipids are also found in a variety of other single-cell organisms such as yeasts used in cheese processing. But the problem with using algae for biomass has always been the amount of energy it takes to pull the lipids or biocrude from the watery plants. Under current methods, it takes more energy to turn algae into biocrude than the amount of energy you get back out of it.

A team of University of Utah chemical engineers have developed a new kind of jet mixer that extracts the lipids with much less energy than the older extraction method, a key discovery that now puts this form of energy closer to becoming a viable, cost-effective alternative fuel. The new mixer is fast, too, extracting lipids in seconds.

The team’s results were published in a new peer-reviewed journal, Chemical Engineering Science X. The article, “Algal Lipid Extraction Using Confined Impinging Jet Mixers,” can be downloaded here.

“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,” says Leonard Pease, a co-author of the paper. “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.”

Right now, in order to extract the oil-rich lipids from the algae, scientists have to pull the water from the algae first, leaving either a slurry or dry powder of the biomass. That is the most energy-intensive part of the process. That residue is then mixed with a solvent where the lipids are separated from the biomass. What’s left is a precursor, the biocrude, used to produce algae-based biofuel. That fuel is then mixed with diesel fuel to power long-haul trucks, tractors and other large diesel-powered machinery. But because it requires so much energy to extract the water from the plants at the beginning of the process, turning algae into biofuel has thus far not been a practical, efficient or economical process.

“There have been many laudable research efforts to advance algal biofuel, but nothing has yet produced a price point capable of attracting commercial development. Our designs may change that equation and put algal biofuel back in play,” says University of Utah chemical engineering assistant professor Swomitra “Bobby” Mohanty, a co-author on the paper. Other co-authors are former U chemical engineering doctoral student Yen-Hsun “Robert” Tseng and U chemical engineering associate professor John McLennan.

The team has created a new mixing extractor, a reactor that shoots jets of the solvent at jets of algae, creating a localized turbulence in which the lipids “jump” a short distance into the stream of solvent. The solvent then is taken out and can be recycled to be used again in the process. “Our designs ensure you don’t have to expend all that energy in drying the algae and are much more rapid than competing technologies,” notes Mohanty.

This technology could also be applied beyond algae and include a variety of microorganisms such as bacteria, fungi, or any microbial-derived oil, says Mohanty.

In 2017, about 5 percent of total primary energy use in the United States came from biomass, according to the U.S. Department of Energy. Other forms of biomass include burning wood for electricity, ethanol that is made from crops such as corn and sugar cane, and food and yard waste in garbage that is converted to biogas.

The benefit of algae is that it can be grown in ponds, raceways or custom-designed bioreactors and then harvested to produce an abundance of fuel. Growing algae in such mass quantities also could positively affect the atmosphere by reducing the amount of carbon dioxide in the air.

“This is game-changing,” Pease says of their work on algae research. “The breakthrough technologies we are creating could drive a revolution in algae and other cell-derived biofuels development. The dream may soon be within reach.”

Learn more: Turning algae into fuel



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Biocrude oil from sewage is the future – and it’s almost here

Sludge from Metro Vancouver’s wastewater treatment plant has been dewatered prior to conversion to biocrude oil at Pacific Northwest National Laboratory. Courtesy of WE&RF

Sludge from Metro Vancouver’s wastewater treatment plant has been dewatered prior to conversion to biocrude oil at Pacific Northwest National Laboratory.
Courtesy of WE&RF

Technology converts human waste into bio-based fuel

It may sound like science fiction, but wastewater treatment plants across the United States may one day turn ordinary sewage into biocrude oil, thanks to new research at the Department of Energy’s Pacific Northwest National Laboratory.

The technology, hydrothermal liquefaction, mimics the geological conditions the Earth uses to create crude oil, using high pressure and temperature to achieve in minutes something that takes Mother Nature millions of years. The resulting material is similar to petroleum pumped out of the ground, with a small amount of water and oxygen mixed in. This biocrude can then be refined using conventional petroleum refining operations.

Wastewater treatment plants across the U.S. treat approximately 34 billion gallons of sewage every day. That amount could produce the equivalent of up to approximately 30 million barrels of oil per year. PNNL estimates that a single person could generate two to three gallons of biocrude per year.

Sewage, or more specifically sewage sludge, has long been viewed as a poor ingredient for producing biofuel because it’s too wet. The approach being studied by PNNL eliminates the need for drying required in a majority of current thermal technologies which historically has made wastewater to fuel conversion too energy intensive and expensive. HTL may also be used to make fuel from other types of wet organic feedstock, such as agricultural waste.

What we flush can be converted into a biocrude oil with properties very similar to fossil fuels. PNNL researchers have worked out a process that does not require that sewage be dried before transforming it under heat and pressure to biocrude. Metro Vancouver in Canada hopes to build a demonstration plant.

Using hydrothermal liquefaction, organic matter such as human waste can be broken down to simpler chemical compounds. The material is pressurized to 3,000 pounds per square inch — nearly one hundred times that of a car tire. Pressurized sludge then goes into a reactor system operating at about 660 degrees Fahrenheit. The heat and pressure cause the cells of the waste material to break down into different fractions — biocrude and an aqueous liquid phase.

“There is plenty of carbon in municipal waste water sludge and interestingly, there are also fats,” said Corinne Drennan, who is responsible for bioenergy technologies research at PNNL. “The fats or lipids appear to facilitate the conversion of other materials in the wastewater such as toilet paper, keep the sludge moving through the reactor, and produce a very high quality biocrude that, when refined, yields fuels such as gasoline, diesel and jet fuels.”

In addition to producing useful fuel, HTL could give local governments significant cost savings by virtually eliminating the need for sewage residuals processing, transport and disposal.

Simple and efficient

“The best thing about this process is how simple it is,” said Drennan. “The reactor is literally a hot, pressurized tube. We’ve really accelerated hydrothermal conversion technology over the last six years to create a continuous, and scalable process which allows the use of wet wastes like sewage sludge.”

An independent assessment for the Water Environment & Reuse Foundation calls HTL a highly disruptive technology that has potential for treating wastewater solids. WE&RF investigators noted the process has high carbon conversion efficiency with nearly 60 percent of available carbon in primary sludge becoming bio-crude. The report calls for further demonstration, which may soon be in the works.

Demonstration Facility in the Works

PNNL has licensed its HTL technology to Utah-based Genifuel Corporation, which is now working with Metro Vancouver, a partnership of 23 local authorities in British Columbia, Canada, to build a demonstration plant.

“Metro Vancouver hopes to be the first wastewater treatment utility in North America to host hydrothermal liquefaction at one of its treatment plants,” said Darrell Mussatto, chair of Metro Vancouver’s Utilities Committee. “The pilot project will cost between $8 to $9 million (Canadian) with Metro Vancouver providing nearly one-half of the cost directly and the remaining balance subject to external funding.”

Once funding is in place, Metro Vancouver plans to move to the design phase in 2017, followed by equipment fabrication, with start-up occurring in 2018.

“If this emerging technology is a success, a future production facility could lead the way for Metro Vancouver’s wastewater operation to meet its sustainability objectives of zero net energy, zero odours and zero residuals,” Mussatto added.

Nothing left behind

In addition to the biocrude, the liquid phase can be treated with a catalyst to create other fuels and chemical products. A small amount of solid material is also generated, which contains important nutrients. For example, early efforts have demonstrated the ability to recover phosphorus, which can replace phosphorus ore used in fertilizer production.

Learn more: Fuel from sewage is the future – and it’s closer than you think



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