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Biomass algae for biofuel

Published on February 10th, 2016 | by Tina Casey

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Algae Biofuel Still In Play Despite Low Oil Prices, Says NREL

February 10th, 2016 by  


Biofuel has been taking some hits from the oil price crash, but just last week we were noticing that the US Department of Energy is plowing ahead with more funding for algae biofuel research, and now here comes the National Renewable Energy Laboratory with more proof-of-life for the algae biofuel field. Researchers at the lab are reporting a breakthrough system that ramps up the efficiency of the algae-to-ethanol process to a significant degree.

algae for biofuel

Scenedesmus Wins “Top Model” Algae Biofuel Face-off

The new algae biofuel process builds on NREL’s previous work with two algae strains, Chlorella and Scenedesmus. If Chlorella rings a bell, it’s a salt-tolerant strain that researchers in Australia are deploying for a system to cultivate algae for biofuel while capturing carbon dioxide from power plant emissions (the CO2 feeds the algae).

Scenedesmus is a new one on us, but it pops up on the NREL website, in a “bioprospecting” presentation partly funded by the Air Force Office of Scientific Research. The study identifies naturally occurring, biofuel-friendly algae in different regions of the US, from Brooklyn to the Salton Sea.

In the latest development, NREL has nailed Scenedesmus as its go-to algae for a new soup-to-nuts approach to commercializing algae biofuel.

Commercializing Algae Biofuel

The problem with the conventional approach to algae biofuel systems is that they lean heavily on increasing the lipids content of algae. That can only get you so far in terms of developing a commercially competitive process, so NREL has been focusing on a whole-body system that extracts lipids, carbohydrates, and proteins for further processing into marketable products.

Carbs can be converted to sugars, which can be fermented to produce ethanol, but for a while NREL was stuck on getting that part of the process down pat. They initially tinkered around with a separation process that converted the carbohydrates, but not very efficiently. About 37 percent of the sugars would require an additional, expensive washing step to be fermentable.

The new development leaps over the original separation idea and goes straight to an initial fermentation step using a mixed algae “slurry,” a system that NREL calls combined algal processing (CAP). The results in terms of gallons/gasoline equivalent (GGE) per ton of biomass were impressive:

Using Scenedesmus and the CAP, and after upgrading the lipids to renewable fuels, scientists were now able to produce a total fuel yield estimated at 126 GGE per ton. That’s 88 percent of the theoretical maximum yield and 32 percent more than the yield from lipids alone.

Don’t break out the pom-poms yet. Although NREL’s modeling demonstrates a significant cost reduction for the new process, the lab also notes that it still doesn’t come close to competing with petroleum.

However, the lab is optimistic that the new system shows a way forward for future competitiveness.

In addition, we’ll note that raw cost is not the only factor that could come into play in the new algae vs. fossil algae marketplace. We’re thinking that as the nation’s petroleum pipeline infrastructure is getting to the straw-that-breaks-the-camel’s-back stage (Keystone is still alive, and there are more exampleshere’s another one), the benefits of hyper-local algae biofuel facilities are becoming more apparent.

The value of carbon capture could also become a critical factor moving forward. Aside from the aforementioned project in Australia, the US energy company Duke Energy is beginning to explore algae cultivation for capturing emissions from power plants.

The Nitty-Gritty Of Competitive Algae Biofuel Production

For some further insight into just how serious the US Energy Department is about algae biofuel, check out the agency’s algae page (including a nifty video) under BETO, the Bio-Energy Technologies Office. The Energy Department also just issued another round of algae biofuel funding on top of two previous rounds, so stay tuned for that.

You can also get more details on the new NREL study under the title “Combined algal processing: A novel integrated biorefinery process to product algal biofuels and bioproducts” in the journal Algal Research.

For those of you on the go, here’s a snippet describing the CAP process in a bit more detail:

In CAP, whole algal slurry after acid pretreatment is directly used for ethanol fermentation. The ethanol and microalgal lipids can be sequentially recovered from the fermentation broth by thermal treatment and solvent extraction. Almost all the monomeric fermentable sugars can be utilized for ethanol production without compromising the lipid recovery.

The study authors also briefly note that, aside from extracting more value from the same algae, there are other opportunities to reduce costs, for example in the infrastructure required to cultivate and harvest algae. Last year we took note of one such approach, in the form of a “shape-shifting” glass tube for more efficient algae production.

Bottom line: corn ethanol is still a dominant force in the US biofuel field, but considering the land use issues at play, algae would be our choice to go mano a mano with petroleum over the long haul.

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Image (screenshot): microalgae via nrel.gov, by J. Pole, Brooklyn College of CUNY.


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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



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