Algae Energy Analysis, or You Do The Math: The Clarens Paper

Instead of getting into algae economics right away, I am in this post responding to a current event of interest…

The algae cycle? from

The headline sure looks bad: “Engineers Find Significant Environmental Impacts With Algae-Based Biofuel.”  The New York Times, U.S. News and World Report, and Science Daily all join the hue and cry:

“The U.Va. research, just published in the journal Environmental Science & Technology, demonstrates that algae production consumes more energy, has higher greenhouse gas emissions and uses more water than other biofuel sources, such as switchgrass, canola and corn.”

Algae has been sold on its green-ness, so this is a stab at the very heart of the nascent industry.  The Algae Biofuel Association fired back the next day, pointing out that much of the data used by the study was from the 70’s and 80’s, and that newer algaculture techniques invalidate the numbers they used.
Now, I have no doubt that new technology will improve algae biofuel’s carbon footprint.  But having read the paper and the online supporting materials, I don’t think that simply invoking the promise of new technology really gets at what the paper was about.

I’d like to do that here.

Part 1:
Is a pile of sticks really the same as a tank of gas?

The authors open their paper with a premise that wipes many of algae’s advantages off the map at the outset.  They declare that they will compare algae to corn ethanol, soy biodiesel, and switchgrass ethanol on a purely energy basis, including the stalks and leaves as equal in value to the starch and oil portions that are currently used for fuel.  Now, plants make their structure out of materials evolutionarily designed to be resistant to breakdown — cellulose, hemicellulose, and lignin — and so making it into fuel requires highly specialized, finicky organisms, or high temperatures to decompose these tough compounds.  All this requires a lot of infrastructure, and a lot of energy (which is why it takes about as much energy as is in corn ethanol to make it), as does gathering up and chopping up plant materials until they are digestible chunks sitting in a bin in a biorefinery.

Algae are a very different picture, and this is one of the main reasons for all the interest in them.   Their biomass can be over 50% vegetable oil (compared to 2-3% for typical conventional oil crops), which can be pumped and pipelined to a standard refinery and transformed with conventional, low-energy methods into gasoline, diesel, and jet-fuel equivalents.    Uncle Joe can also make it into biodiesel in his garage with minimal inputs or even know-how. Try doing that with a pile of damp switchgrass.

But this is a minor objection compared to what the authors did next.

Part 2:
These algae are made for recycling, and that’s just what they’ll do

From the headline, one might assume that the excessive energy use claimed arises from the operations of the algae farm — paddlewheels, centrifuges, and such — after all, it seems like a higher-tech form of farming, involving more gear — but a quick glance at the energy breakdown shows that something altogether different is going on.  In fact, over 97% of the claimed water use and 94% of the energy use arises from the manufacture of fertilizer, CO2, and other chemicals.  Now the technology for synthetic fertilizer (the Haber-Bosch process) was originally developed for explosives, so it should come as no surprise that their manufacture consumes a lot of energy.  That the authors take this into account is valid in theory, but they make an assumption that runs against the most basic economic considerations of algae farming — that the farmers, after extracting the lipid fraction of their algal harvest, will inexplicably burn the remaining fraction for the meager heating value retained therein, then throw the nutrient-rich ash into a landfill.  Assuming that the algae farmer has even a lick of sense, she’ll put those nutrients back into the pond.  The ability to recycle nutrients almost completely is one of the great advantages of algae farming over traditional farming.

Nutrient recycling, plus the use of exhaust for CO2 (which every biofuel algae farmer I’ve ever met intends to do), profoundly changes the analysis, and in fact reverses the result that was trumpeted across all the headlines.  With 100% nutrient recycle, using the authors’ numbers, algae biofuels come out well ahead of corn, canola, and switchgrass, even using the authors’ approach of equating haybales and barrels.  With 95% nutrient recycle, algae still comes out on top of all comers except a slight loss to switchgrass on water use.  This is comparing apples to oranges, though, as switchgrass requires scarce fresh water, and algae can grow in salt- and waste-water.

Part 3:
The Land will have the last word.

The authors chose to ignore the greenhouse gas impacts of indirect land-use changes, which can be a hundred times greater than the annual emissions thought to be saved by land crop-based biofuels, and really, IMO, should rule out any land crop-based biofuel not grown on truly marginal land.  Algae do not use arable land, and so avoid this impact as well as competition with food production.


So a little digging reveals that the media’s presentation of the results of this paper are entirely misleading.  I do agree with the authors regarding the advantages of the use of wastewater (the NASA project I’m working on is designed to use wastewaster for nutrients and exhaust for CO2), and as far as source-separated urine as an algae nutrient source goes, this has been a favorite research area of mine (bottom line: it works great!), so we don’t disagree about everything.

But it’s hard to overlook the fact that a result so contrary to the algae industry’s founding notions is music to the ears of some in the ethanol crowd, who are beginning to feel some competition from algae for the title of “fuel of the future”.

P.S. If you wonder about my qualifications to evaluate the quality of another scientist’s energy analysis, please take a look at my recent paper comparing energy use in organic farming to that of conventional methods, (here’s a link to a pdf of my slides) in unprecedented detail (which turns out to be pretty important).  I have also written a consulting report on biofuel energy balances, so I feel qualified to say that these guys are way off the mark, for reasons much more fundamental than those cited by the ABO.

But I encourage you all to look at the paper itself, and to give comments and feedback.  Thanks!


10 Responses

  1. Algae ponds have been studied at ubiversities for years. Every algae pond has contamination issues and wll not generate more than 5,000 gallons per acre per year.

    The US Government has spent over $2.5 billion dollars on algae research in the last 35 years and all we have to show for it are shelves full of useless patents. Algae have been researched at universities and in laboratories in the US for over 50 years, financed in significant part by government funds. One of the largest problems is that the research has been done in laboratories and at universities, using federal funds, and there is fear at that level that commercialization will ‘ruin it for them’. What it will ruin is the steady stream of ‘free’ money flowing from the DOE, NREL, the DOD, DARPA and other Washington-based agencies to University Row. It was most disconcerting to hear from more than one agency that the funds it awards are, by Congressional mandate, restricted to research. If we could invest one years’ worth of awards into commercialization instead of research, we could easily move this industry into commercialization. The research would be needed to improve technologies, but Microsoft and the American Petroleum Industry, among others, can confirm that this is a necessary component of any industry growth.

    According to my sources. another large problem is, in order to be a grant award recipient, the algae technologies must be investigated and approved by NREL, and that NREL is not particularly supportive of the private initiative. NREL is the same government agency that ran out of money and stopped the otherwise successful Aquatic Species Program after 18 years of federal funding. After the Consortium grant announcement, sources at various government agencies, including NREL itself, shared the fact that grants would only be awarded to proposed groups that included government agencies in their consortia. The truth of that statement lies in the fact that one of the groups that recently received an award is led by NREL and the other by the David Danforth Plant Science Center, and includes two national laboratories (one of which is also a participant in the NREL award) and 11 universities. According to its website, “Scientists at the Danforth Center receive more than half of their funding from federal agencies via competitive grant programs, with the rest of the funding coming from private companies and foundations. In addition to the USDA and the NSF, other federal granting agencies that fund research at the Center include the National Institutes of Health, the U.S. Agency for International Development, the U.S. Department of Energy, and the Environmental Protection Agency…”. In the last 2 years, it has received grants from the Department of Transportation and the National Sciences Foundation relating to biofuels, in addition to housing one of the DOE’s Energy Frontier Research Centers.

    Federal agencies are incapable of commercializing anything. The only ones that are even remotely designed to earn money are those that regulate the financial institutions, and we all know that the American banking system has failed us miserably. Until someone in Washington who has power and authority to stop this steady stream of funding to nowhere, listening as the algae researchers continue to claim that they are 3-5 years away from completing their research, it’s too expensive and they need more time and money, they will receive grant money from the DOE, NREL, DOD and DARPA. Nothing will ever get commercialized at the university level. Until there is an industry, there is no value to the results of the research. Until development of this industry is taken out of the hands of the research community, and put into the hands of the business, not corporate, community, this industry will never support reducing our dependence on foreign oil.

    The question you need to be asking is ” Does the US really want to get off of foreign oil or do we want to continue to fund the algae researchers at the universities.” The problem is we can grow, harvest and extract algae today with all “off-the-shelf” proven technology. We no not need genetic modification at all when there are existing algae strains currently on the market with 30-60% oil content. Algae production requires far less land and water than any other terrestrial crop (see page 194 of the DOE’s National Algal Biofuels Technology Roadmap), which has the farmers in an uproar right now. The ethanol credits went away, allegedly shutting down an industry – can it really be that without the tax credit, years of time, effort and expense will be for naught, leaving us with unedible genetically modified corn fields? The DOE is still awarding grants for algae pond research when it was established years ago that all algae ponds get contaminated and will never produce enough algae to get us off of foreign oil. Stop wasting monies on research.

    • You didn’t read this post, as far as I can tell, but I’ll reply anyway.

      The issue of open ponds vs. enclosed bioreactors is a popular one, and something I’ll take up after dealing with algae economics. If you read my last post, you’d know that even the cleverest ponds or photobioreactors will never get more than about 6,000 gallons per acre per year.

      As for your allegations regarding funding of research, there may be a few folks doing research with more of an eye to their careers than on commercialization, but the vast majority (if not all) of the people I know working in the algae biofuel field, in and out of universities and government labs, are highly oriented toward the fastest possible commercialization of their work. There are many well-funded companies working to commercialize ASAP.

      If you read my previous post, and my next post when it’s up, maybe that will help you understand that the “off-the-shelf” technology is not up to the task of producing algae biofuel economically. Some algae companies feel they can develop (or adopt) the necessary technology in the short term, so they are building pilot plants, but there are still many open research topics which will probably need to be addressed for long-term success, and many wild ideas which are too high-risk for private investment, but ought to be investigated for their high possible pay-off.

      • With all due respect, all ponds get contaminated and will never be used for industrial production. That has been tried for over 35 years. That is why many ponds are changing over to PBR’s.

        Commercial-scale vertical PBR’s are built today with all off-the-shelf existing proven technology. Benchmarked results start at 50,000 gallons per acre per year up to 500,000 gallons per acre per year. One question, have you personally ever built a commercial-scale vertical PBR to date?

        Algae research grants are being investigated. There are some algae researchers today that have set up their own private companies using grant money.

      • @cecore, You might want to do a bit more research before making such claims.

        “all ponds get contaminated and will never be used for industrial production.”

        Thousands of tons of microalgae are grown industrially every year worldwide, 99+% in open ponds. Obviously the contamination issue is not a show-stopper. Serious, well-funded companies are pursuing open pond algae biofuels.

        “Benchmarked results start at 50,000 gallons per acre per year up to 500,000 gallons per acre per year.”

        See my last post. Anyone claiming over 6,000 gallons per acre per year is just blowing smoke, no matter how clever their design.
        That said, PBRs have some important advantages (as well as disadvantages) compared to open ponds (and are in fact what we are pursuing in the NASA OMEGA project), and are definitely worth talking about, but their cost per acre must be kept to an absolute minimum…

  2. Hi Aaron,

    Great website, love the irreverent writing style!

    I wrote two articles on this area myself, here:
    Algae Biofuels – Not Sustainable (
    Taking stock of Phosphorus and Biofuels (

    I’m sure I’ve gotten some stuff wrong in the analysis.

    You raise a good point that I couldn’t find information on.

    Can you fully recycle the nutrients?

    Is there evidence where this has been done?

    How much of the phosphorus etc reacts with the dissolved metals in the water?

    Do you just dump the remains into the pond, and then they naturally recirculate? Does this affect the optimum nutrient ratio in the pond?

    My reading of the study was that they stopped at the biomass stage. They left out the most intensive part of the algae process – extracting the oil. I think the study did the best it could given the dearth of information. Apparently the researcher is going to work with the algae biofuels association after they give him their ‘updated’ data.

    What would you envisage the best case lifecycle Energy Return On Investment (EROI) to be? 2:1, 3:1? To be honest, that’s still pretty poor.

    Best Regards,

    • Hi Eamon,

      Thanks! I like your site as well, especially the phosphorus article. Obviously we came to very different conclusions on Clarens’ article, and on the feasibility of algae biofuels in general. I do agree, though, that there is a great excess of hype in the field, and an unfortunate number of companies making unsupportable claims, probably to attract naive investment dollars.

      In answer to your Q’s re:nutrient recycle, because the biofuel portion of the algae doesn’t contain any of the NPK, 100% nutrient recycling is theoretically possible, but hard data are not easy to come by. I don’t think that many companies or research groups are grappling with this problem directly, as it will only become a significant issue at the larger scales of production no one has reached yet, because of economic issues I will address in my next post. (Dmitrov’s analysis has several caveats, there is still hope to be sure!)

      Algae are highly adept at getting at all natural sources of P, as it is frequently a limiting nutrient in the wild, producing a range of phosphatases and P-storage mechanisms, and often co-habitate with bacteria that perform nutrient-extraction for them, so I would not be too worried about availability. Also, if some fraction (e.g. struvite) of precipitated nutrients were to be used as higher-value conventional fertilizer, the energy/carbon costs would still be ameliorated.

      If there is minimal nutrient loss in the product extraction, the nutrient ratio would still be optimal for algae growth, as it would be the exact ratio inside the algae.

      Inventing an economic (and thus presumably energy-efficient) dewatering & extraction process (or avoiding having to do this altogether, by having the critters excrete the product) is one of the most important challenges to commercial algae biofuel production.

      Your dismissal of wastewater-based algae production is profoundly mistaken (read up on the work of Oswald & co.) and I believe that this is one of the greatest opportunities for algae going forward…


      • BTW, I forgot to point out here that though the dewatering-extraction costs for algae may be high, they are certainly high for land crop-based biofuels as well despite what their boosters say.

        If nutrient recycling is 95% or better algae have a shot at better energy ratios than their land-based competitors, depending on whether dewatering & extraction can be made less energy-intensive than the gathering, drying, and processing of cellulosic stock. If wastewater is used, especially if some of the current ww energy use can be eliminated using algae (very much possible!), the energy ratio will be far better. This does not count the other great advantages of algae on land use, runoff, water use, etc.

      • Thanks for the replies. I don’t doubt that nutrient mining from wastewater is both very doable and more economical than stand alone production.

        The nutrients content of wastewater would, I imagine, be quite variable. Furthermore, the Clarens paper supporting info ( looked into the issue of using wastewater and said: “additional chemical fertilizers would be required to meet the N and P requirements.”

        Also, looking at the phosphorous cycle from my article, it seems that worldwide about 30% of annual phosphorus production ends up in wastewater. It is incredibly dispersed among thousands of treatment plants globally. Also, in the developing world they often can’t afford treatment plants. China and India routinely discharge untreated effluent.

        I recall a stat that up to 20% of Pakistani farm produce is fertilized with raw wastewater and considerable amounts in India also. Dana Cardell suggests collecting urine and using it as fertilizer. So there are competing uses for these nutrients.

        For argument’s sake 10% of annual phosphorus production might be practically accessible. This would require algae plants at most treatment plants in the developed world.

        10% of world current annual phosphorus production could give you between 0.5 and 3 million barrels per day depending on yield if Figure 17 from the phosphorus article is correct.

        Although from this you have to subtract the lifecycle energy input to wastewater algae. This input will be moderated somewhat by biogas production and some free nutrients. I think you would be lucky to get 2 units of biodiesel energy out for every unit of non-solar energy needed along the production chain.

        So taking the middle yield of 1.75mb/d and an EROI of 2, the actual useful energy got from the sun would be 1.15mb/d.

        The current global consumption is 85mb/d. It’s a nice helper and welcome, but nowhere near the amount required to sustain current lifestyles.

        The phosphorus market is going to be very tight in the 2020s. There were riots at high fertilizer prices by Indian farmers in 2008 and they couldn’t afford to fertilize their fields. The notion that algae have no interaction with the food chain is thus mistaken.

        Furthermore, because of the significant energy input needed for algae production, their costs are to some extent coupled with the global price of energy. The argument that they get relatively cheaper as oil prices go up might not be totally accurate.

      • Thanks Eamon, this is a subject in which I am quite interested, so I’m happy to get into more detail.

        I know several wastewater specialists, and algae in ww specialists, and have read a lot of the literature. The nutrient content of ww has been found to be sufficiently constant to grow algae consistently in every case, the only exception being systems where storm drains are combined with sewage, in which case they get excessively diluted during rainstorms. Algae are much less picky about N to P ratios than the Redfield ratio would suggest. The main question would be how dense a culture could be sustained on a particular effluent; concentrating the stuff (hopefully recovering the water which you’re at it) is generally a good idea, and we have a neat scalable way of doing that in the NASA OMEGA.

        Your figure 17 in your phosphorus article doesn’t include the possibility of nutrient recycling, which would change the result dramatically, more than an order of magnitude. With nutrient recycling algae farming is far more nutrient-efficient than any other crop, and thus will be extremely attractive in a P-limited future.

        As far a EROI goes, with nutrient recycle algae has a good shot at being better than any land crop. The NASA OMEGA bags use the ocean for zero-energy mixing and dewatering, and wastewater for nutrients, so we think we may be able to achieve a good EROI, we’ll get back to you on that as we just got funded…

        Not sure if you are counting animal wastewater streams as well, they are comparable in total nutrient content to municipal streams, so another opportunity there.

        That said, you won’t find me saying that algae are likely to replace our current consumption level of fossil fuel all by themselves. If algae biofuel were to hit 3M barrels/day, I’d be pretty happy.

  3. Hi Aaron,

    like the style and level of youre comments. I work on a pilot plant for algaefarming in the Netherlands and closely try to monitor all developments. I found your blog’s and intent to follew them closely. I also like the Omega project and corresponded in the past with Dr. Trent. I am looking forward to see them getting productive..

    The pilot plant consists of 4 hybrid PBR’s, 20 M3 well type reactors with submerged LED support to reduce respiratory losses at night and in the winterseason. Were tightly connected to an dairyfarm with an anaerobic digester (producing enough biogas to run a 700 kW generator), we use 2 % of the energy, low value heat and pipe the exhaust gas as CO2 source into our algaeponds. Two reactors are run in chemostatmode and two in turbidostat mode with continuous harvesting by centrifuges. This last mode is actually a recycling experiment, the centrifuge is only partially removing the cells and flowthrough is returned to the reactor.. After some months of running the turbidostat I learned that it is possible but it takes very close monitoring of the conductivity to keep it productive. however the nutrient use is much more efficient compared to the chemostat’s where the supernatant is discharged in a open pond.
    Goal of the project is to produce foodgrade PPO and may be some biodiesel in future. first we like to get the concept running at the dairyfarm. my main point is i like to bring forward is that algaeindustry should be more directed towarde the farmerswold, they are the kings of biomas and marginal profits. If algae cannot be made profitable by farmers no one can earn a dime with algae… only hustlers and scientists…..
    Every pilot that runs on a farm gets some credibility from me, pilots a remote and desolate sites without any agricultural cooperation or culture seem to me deemed to perish…

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