EROI of Algae

I have posted before on algae andfocused mostly on integrating any such protocol into agriculture.  This work pretty much tells us that we canignore conventional thinking and look instead for breakthroughs that produceand excrete usable product on a continuous basis.   We ended up in much the same place with cellulose.  You really have to remove the handling aspectpretty completely in order to make it all work.

In the end, the input thatmatters is CO2 and that means we are looking to linking such technology topower plants and heat plants that use carbon. That technology is very much on the verge of true obsolescence as wewrite and the changeover to non CO2 technology is ready to happen in a numberof different ways.

Agricultural waste conversion to usablefuels and byproducts does have a bright future if only to optimize the farmeconomy.  Importing inputs is always aserious cost factor and been able to convert waste allows a lot of valuable processesto be supported.

The EROI of algae biofuels

In an earlier blog post (“TheAlgebra of Algae…to Biodiesel”) I discussed if the US was to reduce its CO2 emissions to 17%of those in 2005 (mimicking the ‘popular’ climate legislation from two yearsago in 2009), then the UScould produce 50 billion gallons of biodiesel from an algae feedstock.Aside from later being told that titling the blog “Algaebra” would have beenmuch better (what I agreed with at the time), I have now discovered that theweb is littered with discussions of brassieres made of algae. I’m glad I usedmy previous title!

But I digress, the caveat for my previous blog on algae biodiesel wasis that to meet the CO2emissions limits there could be no other source ofCO2 emissions other than the power plants that would be capturingCO2 and piping that CO2 to the algae farms. There is also thepossibility of using CO2 directly from the atmosphere to grow algae, butmost algae-facility designs assume a source of concentrated CO2 to growthe algae feedstock. Clearly we need to understand the limitations of usingambient air, and the inherent CO2 in the air, versus supplementalCO2 from anthropogenic sources.

Over the last year a student (Colin Beal) atthe University of Texas, Austin,has been characterizing the experimental set-up at the Center for Electromechanics fortesting an algae to bio-oil process. The process stops short of converting thebio-oil into biodiesel, and he presented the results at a recent conference:Beal, Colin M., Hebner, Robert E., Webber, Michael E., Ruoff, Rodney S., andSeibert, A. Frank. THE ENERGY RETURN ON INVESTMENT FOR ALGAL BIOCRUDE: RESULTSFOR A RESEARCH PRODUCTION FACILITY, Proceedings of the ASME 2010 InternationalMechanical Engineering Congress & Exposition IMECE2010 November 12–18,2010, Vancouver, British Columbia, Canada, IMECE2010-38244.

Colin counted the direct (electricity primarily) and indirect energy(nutrients, water, CO2, etc) inputs into the process along with the energycontent of two outputs: the biomass of the algae itself and the bio-oilextracted from the algae. He did not count the energy embodied in any capitalinfrastructure. What he found for this experimental, and very batch process wasthat the EROI of the experimental process was approximately 0.001.

This experimental EROI value for energy from algae must be kept inperspective of the stage of development of the entire technology and process ofinventing new energy sources and pathways. It is important that we understandhow to interpret findings “from the lab” into real-world or industrial-scaleprocesses. To anticipate the future EROI of an algae to biofuel process, Colinperformed two extra analyses to anticipate what might be possible ifanticipated advances in technology and processing occur: a Reduced Case andLiterature Model calculation.

The Reduced Case presents speculated energy consumption values for theoperation of a similar production pathway at commercial scale. Many energyinputs are simply not needed or would be much smaller in a continuous flowprocess. The Literature Model provides an estimate for the EROI of algalbiocrude based on data that has been reported in the literature. In this waythe Reduced Case is grounded on one side by the sub-optimal experimental dataand on the other side by the Literature Model, which is largely comprised oftheoretical data (particularly for biomass and lipids production from optimalalgae).

What Colin discovered was that the EROI of the Reduced Case andLiterature Model were 0.13 and 0.57, respectively. This shows that we have muchto learn for the potential of making viable liquid fuels. Additionally, Colin’scalculations for the experimental set-up (and Reduced Case analysis) show that97% of the energy output resides in the biomass, not the bio-oil. For hisidealized Literature Model, 82% of the energy output was in the biomass.

While these results seem discouraging, we do not have much ability toput these results into context of the rate of development of other alternativetechnologies and biofuels. How long did it take to get photovoltaic panels withEROI > 1 from the first working prototype in a lab? We have somewhat of anidea that it took one or two decades for the Brazilians to get reasonable EROI> 1 from using sugar cane for biomass and biofuel production (Braziliansugar cane grown and processed in Sao Paulo is estimated near EROI = 8).

I believe we need to strive to quantify EROI for new technologies eventhey are still in the laboratory stage. Perhaps some very early technologiesand processes are even too early for estimating or measuring EROI, but algaebiofuels are clearly in the mainstream of research given the $500 minvestment by Exxon-Mobil into genomics firms searching for the ideal strainsof algae. These ideal strains of algae might simply excrete hydrogen, ethanolor lipids such that all of the capital infrastructure and direct energy requirementsassumed for collecting algae and extracting the lipids even in Colin’sLiterature Model can be largely unnecessary. Let’s hope others join in tryingto assess the EROI of their experimental and anticipated commercial processesfor alternative energy technologies.

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