Researchers develop one-step algae harvesting, FAME conversion

By Ron Kotrba | September 04, 2012

Researchers from the University of Texas at Austin have developed a proof-of-concept design to harvest, dewater and convert the dried algae to biodiesel in a one-step process using resins.

In a paper titled, “Use of Anion Exchange Resins for One-Step Processing of Algae from Harvest to Biofuel,” University of Texas at Austin scientists Jessica Jones, Cheng-Han Lee, James Wang and Martin Poenie note that to circumvent the cost-prohibitive obtainment of algae oil due to the pumping and processing of large volumes of dilute algal suspensions, they used Amberlite anion exchange resins to simplify the process, which has the potential to greatly reduce processing costs.

In their design, the researchers packed a column with the beaded, fixed-charge Amberlite anion exchange resins and poured dilute algae water through. The algae bind with the resins and, at the point of saturation, the water coming out of the bottom of the column changed from clear to green-colored. Then, the researchers eluted the algae off the resins with a mix of methanol and sulfuric acid, essentially regenerating the resins for reuse.

“In this study, we show that anion exchange resins such as Amberlite can concentrate and dewater algae (i.e., harvest algae) and then be eluted with 5 percent sulfuric acid/methanol reagent,” the researchers note in the paper. “The eluted algae appear to dissolve in the sulfuric acid reagent and esterified fatty acids are converted to FAMEs (biodiesel).”

One of the researchers, Martin Poenie, told Biodiesel Magazine they achieved 40 percent dry weight conversion to biodiesel, “which is very good,” he said. “And then we used a hydrophobic resin to pull the biodiesel out. We don’t think that’s a commercial way to do it, but we were just showing that there are ways to pull the biodiesel out of the sulfuric acid and methanol mix. And then you can recycle the sulfuric acid and methanol.”

Poenie said the current generation of resins is limited in this work because they hold a little bit of water, “and that’s not good,” he said, adding this is why acid and not base catalysis was used in the proof-of-concept. “With this particular batch of resins, it doesn’t work well with base because the resin itself can bind with base and there is some water that’s held by the resins. So in this particular incarnation, acid works better.” The researchers have another paper coming out soon, specifically on the use of resins for harvesting. “Those resins can be used in the same capacity and, in that case, the base catalysis might work much better,” Poenie said.  

The fixed-charge resins used in the proof-of-concept design work, but Poenie said they’re not the best for the job because, in addition to holding water, they don’t have a very high binding capacity. “We’ve come out with two resins that have much better binding capacities, and just changing the pH causes the algae to be released,” Poenie said. “We’re not talking about drastic changes [but it] causes the algae to be released, so it’s particularly good for harvesting. We haven’t tested them for one-step biodiesel, but it’s likely they’ll be good for that as well.”  

Poenie also said more resin design work needs to be done. “We don’t think beads are the best form,” he said. “They’re porous beads, so because of the porosity they hold water. We envision belt harvesting using resin-based belts. We have spent a good bit of research on design and synthesis of resins, a lot of that was trying to get resins that don’t bind nonspecifically, that don’t foul, and yet have very high binding capacity. The resin in this one did not have a high binding capacity, but we’ve developed resins that can bind up to 150 milligrams dry weight algae per gram of resin. We elute at quite high concentrations, 50 grams per liter.” At 100 grams per liter, the algae is paste-like.

The beauty of this, Poenie said, is that you could devise a process using resins where you don’t need to pump water to harvest the algae because the resins just suck them up. “And then it allows you to elute the algae into a very concentrated form rather easily,” he said, “so this seems to be an inexpensive and clean way to harvest algae.” 



10 Responses

  1. Durwood M. Dugger



    This is an interesting process - at least academically. Unfortunately, the researchers seem to have no concept of the scales involved for this kind of biofuel process to have significant commercial impact, the economic consequences of the process required resources, or the probability/limitations of it having a significant impact on our energy needs. They fail to mention that the components of their process (algae, sulfuric acid, methanol, and anion resins) are all directly or indirectly dependent for their independent production on the petroleum products that the process would seek to replace physically and fiscally. Without an accompanying projected economic and cost sensitivity analysis of the process at a projected commercial scale we have no idea if the process provides any real economic savings over existing methods, or just academic swaps (or increases) with the existing costs of pumping, harvesting, and processing algae in the traditional "press" methods. Without a comparison of the expected costs of anion resin beds, eluent chemicals, recycling processes for those chemicals and the associated energy budgets - it's hard to get very excited and more importantly to justify supporting this work on tax dollars. Reporting process development work without it's associated economic and resource impacts and implications is not only incomplete, it is unprofessional and essentially self-destructive. This is why algae biofuels haven't progressed more rapidly - not for a lack of technological innovation, but rather a lack of focus on and demonstration of the pertinent process economics to produce algae and terrestrial biofuels that are competitive with either petroleum, or other alternative energies like solar, wind and tide. This leaves not only the public, and national leadership inadequately informed and unable to make competent decisions regarding our energy source future, but it leads the researchers themselves not understanding whether the direction their work takes is economically possible, or an economic dead end. Consider that four major mass balance studies have all concluded that any significant energy production from biofuels - algae biofuels included, will require NPK fertilizer - massive amounts of NPK. As a direct result any at scale biofuels will compete directly with food production demand for NPK. This is a critical life threatening and unavoidable consequence of biofuel development, in a world whose food production is already 85-95% dependent on NPK fertilizers and the petroleum used to produce NPK. NPK production itself is dependent on and uses large amounts of petroleum products - in a country supposedly very concerned about it's petroleum addiction and declining economically accessible petroleum reserves. Besides the need for petroleum to make NPK, NPK also uses imported phosphates. According to the 2011 USDA Fertilizer Import Summary - "U.S. nitrogen and potash supplies largely depend on imports. More than 54 percent of nitrogen (N) and 85 percent of potash (K2O) supply was from imports in calendar year 2011. Because domestic production capacity is limited, any increase in nitrogen and potash demands will have to be met largely by imports." In addition, we imported 15% of our phosphates from Morocco in 2011. Morocco is estimate to have the bulk 75-85% of the worlds remaining unexploited phosphate reserves. This growing fertilizer import import trend is from a country who a decade ago was a net exporter of NPK. In other words - over half the US's food production fertilizers were imported in 2011. Significant biofuel production - that production beyond the total possible production using wastes (estimated potential of less than 1% of our energy needs) only add to our reliance on foreign imports. In a country (USA) that worries day and night about foreign oil imports because it makes transportation costs inconvenient, it is beyond incredible that the same country doesn't worry about the consequences of having to import the fertilizer that its life and very existence (food production) is dependent upon. Some experts have calculated that if we use biofuels to solve our imported oil problem - we could quadruple our NPK demand and fertilizer imports. The competition between large at scale global biofuel production and global food production is and avoidable consequence and it makes non-waste based biofuels production not only non-renewable, and unsustainable, it makes them a threat to our way of life and arguably in the extreme - our existence. Can our leadership possibly be so ignorant and short sighted in their strategic planning to ignore the consequences of large scale NPK based biofuel production? Sadly they are. In an election year - neither party has a competent and well thought out renewable, sustainable energy/resource plan that provides security and stability for our future. Unlike our ignorant leadership, continued squandering of peak critical resources - especially those essential to food production will direct our way of life and not in ways that any of us would chose independently.

  2. Durwood M. Dugger



    Coincidently - in the news today: Nestle's CEO Paul Bulcke says that the U.S. and EU must change their biofuel targets to prevent future food shortages.

  3. Gabe



    Durwood sounds an awful lot like an oil company stooge. Any other facts you want to spout off about the wonders of oil and the dangers of advanced biofuels?

  4. Durwood M. Dugger



    Gabe, While extracting your foot from you mouth why don't you invest a little effort and do an internet search to see who I am. Hint, I've been producing algae commercially for the last 40+ years - but not for biofuels.

  5. Gabe



    Durwood, Google me and learn some respect.

  6. Leroy



    Durwood is like the people with offices on the second floor in hospitals. People enter on the main floor and enter the Chapel for prayer. Totally unnecessary in these hospitals just go up to second floor and talk directly with God.

  7. anonymous



    Can we get away from religion, egos and political biases and intelligently discuss the merits of the research?

  8. Robert



    Dugger I currently work at a bio-diesel plant and just to let you know that despite what Nestle's CEO says. We use 100% waste oil to produce bio-diesel, so we do not harm the food market at all there are ways to produce bio-diesel and avoid harming the food market.

  9. rusty shackelford



    once all the farm land is being used and farmers are not paid not to grow crops to keep prices high we can have the food vs. fuel argument

  10. David Wood



    WOW!! That old Food Vs Fuel chestnut again !!! Take a look at who made the comment about Food vs Fuel, An International Food Conglomerate Executive. The two largest fuel crops in the US are Corn and Soy Beans, BOTH crops are used primarily for Livestock feed, NOT, sit-down-for-supper corn-on-the-cob, people food. Acording to the Soy Bean Check-off people, 95% of the Soy Bean crop is used for feeding Livestock while 50% of the Corn crop is used for animal feed (another VERY Large % is used for High Fructose Corn Syrup Manufacture [probably the real shortage the Food Executive is worried about!]). Consequently, very little food (in the form of Corn and/or Soy Beans) actually reach your dinner table. So, you say, if we use the crops for fuel then we can't use the crops for animal feed and thus, the Food vs Fuel argument is valid... NOT SO!!! Production of Biofuels creates by-products which are Excellent sources of Livestock feed. Ethanol production, from Corn, generates DDGs (Dried Distillers Grains) which is basically, Sugar-Free Corn, which is then fed to livestock. Biodiesel production uses only the oil from Soy Beans, Soy Bean Meal, which is left over after extracting the oil, is an EXCELLENT source of food for People or Animals. So, if we grow more Corn for the Ethanol Industry and we grow more Soy Beans for the Biodiesel Industry we will ACTUALLY INCREASE the Supply of Food available for Livestock (Corn) and/or People (Soy Beans)!!!! In the end, Neither, Ethanol or Biodiesel production, reduces the food supply, if anything, biofuel production actually increases the supply of food available for human consumption by creating better sources for livestock feed than the "Raw" (unprocessed) Corn or Soy Beans.


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