How much energy can algae produce?

Some say algae can grow faster than any other crop growing on land. The numbers range up to 150 (300) tonnes algal biomass/ha.year, which is several times higher than the best known arable crop. Can algae really deliver this enormous amount of biomass? At the first congress on algae in The Netherlands, Eugène Roebroeck from Lgem made some interesting calculations.

There is only a limited amount of energy reaching the earth’s surface which plants can use to grow.

First, let’s look at the sun and the energy it provides. The sun provides a limited amount of energy per square meter. At the tropics the sunshine is very intense, in contrary to the poles where there is little solar energy. Clouds are also an important factor; regions with more clouds recieve less solar energy at ground level. The World Metereological Organisation has combined these two factors and calculated the annual solar energy available at any given location.

The annual average of solar energy for the Netherlands (and for Belgium) is 110 W/m². This is the maximum energy you can use. But since the spectrum of sunlight has a range from 250 to 2700 nm, containing next to visible light also ultraviolet radiation and infrared radiation, not all of this energy can be used. The figure underneath shows the distribution of energy over the wavelengths. The red area between the two vertical lines is approxymately the energy algae can use: only 43% of the total energy of the sun.

Figure: the total solar spectrum. The red area is the energy at ground level. The red area between the two vertical lines is the part algae can use.

When we know that algae can only use 43% of 110W/m², we see that algae can only use 48 W/m².

Then, we have the efficiency of the photosynthetic apparatus of plants. Research shows that we need about 8-10 photons per captured CO2 molecule. Researchs on trees show that trees can take up only 5-6% of the available photons. This means we have in practice 3 W/m² which the algae can effectively use. Extrapolated to biomass this means we have a potential of 40 tonnes biomass/ha.year.

Since algal growth can be improved to reach higher effeciencies than the data shown above, the maximum value for photosynthetic efficiency can be 10%, which means a maximum potential of 5 W/m² or 68 tonnes biomass/ha.year.

In literature, this theoretical 10% efficiency is applied to areas (for example, the Sahara area) with much higher solar power (350 W/m² instead of 110W/m²), which results in the theoretical production rates of ~150 tonnes biomass/ha.year. This is the maximum amount of energy algae can capture per surface area.

But what has been proven? The NREL reported production rates of 50 tonnes algal biomass/ha.year, so this value can be achieved.

Is this enough to compete with other energy crops? Literature (Van Sark et al., 2006) suggests 8-12 tonnes DRY weight/ha.year for current bioenergy crops. At the congress some people argued that sugar beets can reach productivities of 25 tonnes dry mass/ha.year.

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16 Responses to “How much energy can algae produce?”

  1. Arjan Says:

    Mariah posted:

    I love this website because it shows how we can grow and use algae to lower prices on gas.

  2. will Says:

    Hello Arjan:

    I would like to follow your blog further. The subject is so fascinating. Do you or your professors have any recommendations for public investment in the field? I am interested in learning about options, as I think this industry is poised to take off once Obama is elected president.

  3. Prof.Hans-Jürgen Franke & Prof. Pengcheng Fu Says:

    ETHANOL-PRODUCTION WITH BLUE-GREEN-ALGAE
    A SOLUTION AFTER PEAK-OIL AND OIL-CRASH

    University of Hawai’i Professor Pengchen “Patrick” Fu developed an innovative technology, to produce high amounts of ethanol with modified cyanobacterias, as a new feedstock for ethanol, without entering in conflict with the food and feed-production .

    Fu has developed strains of cyanobacteria — one of the components of pond scum — that feed on atmospheric carbon dioxide, and produce ethanol as a waste product.

    He has done it both in his laboratory under fluorescent light and with sunlight on the roof of his building. Sunlight works better, he said.

    It has a lot of appeal and potential. Turning waste into something useful is a good thing. And the blue-green-algae needs only sun and wast- recycled from the sugar-cane-industry, to grow and to produce directly more and more ethanol. With this solution, the sugarcane-based ethanol-industry in Brazil and other tropical regions will get a second way, to produce more biocombustible for the worldmarket.

    The technique may need adjusting to increase how much ethanol it yields, but it may be a new technology-challenge in the near future.

    The process was patented by Fu and UH in January, but there’s still plenty of work to do to bring it to a commercial level. The team of Fu foundet just the start-up LA WAHIE BIOTECH INC. with headquarter in Hawaii and branch-office in Brazil.

    PLAN FOR AN EXPERIMENTAL ETHANOL PLANT

    Fu figures his team is two to three years from being able to build a full-scale
    ethanol plant, and they are looking for investors or industry-partners (jointventure).

    He is fine-tuning his research to find different strains of blue-green algae that will produce even more ethanol, and that are more tolerant of high levels of ethanol. The system permits, to “harvest” continuously ethanol – using a membrane-system- and to pump than the blue-green-algae-solution in the Photo-Bio-Reactor again.

    Fu started out in chemical engineering, and then began the study of biology. He has studied in China, Australia, Japan and the United States, and came to UH in 2002 after a stint as scientist for a private company in California.

    He is working also with NASA on the potential of cyanobacteria in future lunar and Mars colonization, and is also proceeding to take his ethanol technology into the marketplace. A business plan using his system, under the name La Wahie Biotech, won third place — and a $5,000 award — in the Business Plan Competition at UH’s Shidler College of Business.
    Daniel Dean and Donavan Kealoha, both UH law and business students, are Fu’s partners. So they are in the process of turning the business plan into an operating business.

    The production of ethanol for fuel is one of the nation’s and the world’s major initiatives, partly because its production takes as much carbon out of the atmosphere as it dumps into the atmosphere. That’s different from fossil fuels such as oil and coal, which take stored carbon out of the ground and release it into the atmosphere, for a net increase in greenhouse gas.
    Most current and planned ethanol production methods depend on farming, and in the case of corn and sugar, take food crops and divert them into energy.

    Fu said crop-based ethanol production is slow and resource-costly. He decided to work with cyanobacteria, some of which convert sunlight and carbon dioxide into their own food and release oxygen as a waste product.

    Other scientists also are researching using cyanobacteria to make ethanol, using different strains, but Fu’s technique is unique, he said. He inserted genetic material into one type of freshwater cyanobacterium, causing it to produce ethanol as its waste product. It works, and is an amazingly efficient system.

    The technology is fairly simple. It involves a photobioreactor, which is a
    fancy term for a clear glass or plastic container full of something alive, in which light promotes a biological reaction. Carbon dioxide gas is bubbled through the green mixture of water and cyanobacteria. The liquid is then passed through a specialized membrane that removes the
    ethanol, allowing the water, nutrients and cyanobacteria to return to the
    photobioreactor.

    Solar energy drives the conversion of the carbon dioxide into ethanol. The partner of Prof. Fu in Brazil in the branch-office of La Wahie Biotech Inc. in Aracaju – Prof. Hans-Jürgen Franke – is developing a low-cost photo-bio-reactor-system. Prof. Franke want´s soon creat a pilot-project with Prof. Fu in Brazil.

    The benefit over other techniques of producing ethanol is that this is simple and quick—taking days rather than the months required to grow crops that can be converted to ethanol.

    La Wahie Biotech Inc. believes it can be done for significantly less than the cost of gasoline and also less than the cost of ethanol produced through conventional methods.

    Also, this system is not a net producer of carbon dioxide: Carbon dioxide released into the environment when ethanol is burned has been withdrawn from the environment during ethanol production. To get the carbon dioxide it needs, the system could even pull the gas out of the emissions of power plants or other carbon dioxide producers. That would prevent carbon dioxide release into the atmosphere, where it has been implicated as a
    major cause of global warming.
    Honolulo – Hawaii/USA and Aracaju – Sergipe/Brasil – 15/09/2008

    Prof. Pengcheng Fu – E-Mail: pengchen2008@gmail.com
    Prof. Hans-Jürgen Franke – E-Mail: lawahiebiotech.brasil@gmail.com

    Tel.: 00-55-79-3243-2209

  4. Hiroshi Morikawa Says:

    I’m a Japanese,now staying Bangladesh. In this country we can produce the Snflower 3 times a year. I’m very much interested about Bio Fuel.

  5. What About Algae Biofuel Hype « The Air Vent Says:

    […] Here is a link which claims 3% with literature citing a maximum of 10% […]

  6. Rashid Faridi Says:

    A very good post.
    I have become a regular on your blog.

  7. indi86 Says:

    I like your post, but i would like to know how do you extrapolate from W/m2 to tonnes biomass/ha.year.
    Thanks in advance.

  8. draaronwolfbaum Says:

    There are several land-based crops which can make as much or more *biomass* per hectare than microalgae; however this is mostly cellulose, which is difficult to convert into anything useful. What makes algae interesting is that they can convert 50%+ of their biomass into oil and other useful products. For more info about the commercial and practical aspects of algae production check out
    http://draaronwolfbaum.wordpress.com/2010/01/07/post-1-the-algae-boom-bubble/
    thanks!

  9. H THomas Winn Says:

    I have a continued interest in this subject.

    Thanks for all the input.

  10. Antonio Says:

    There’s some fresh news on algal oil, coming from DARPA.

    http://www.energyrefuge.com/blog/is-the-algal-biofuel-dream-about-to-come-true/

  11. Roy West Says:

    The most important issue of all in this process of bio fuel production is the lack of fresh water to refine the algae into fuel. Until we can figure out how to produce copious amounts of fresh water to go into the refining process, there never will be a transition to a green centric economy.
    Typically where there is large amounts of sunlight, there is a lack of fresh water to go with it. If one looks at the overall energy budget, one must account for this issue. To ignore this is deceptive and a form of intellectual dishonesty.
    We have a moral obligation to look at the entire energy budget. That is to say when we examine the current system, it is clear that costs associated with the fossil fuel industry are not apparent. For example, the nearly half a trillion dollars we spend on securing oil from around the globe. Wars that must be fought and human life that is lost. This does not even take into account the counrtries who we have taken advantage to secure this oil. Do you really think we invaded Iraq to give Iraqi children Walmart Water? It is sickening grab for another soverign nations natual resources.
    We are killing the planet. The oceans are turning acidic and life is dying off at a record pace. The ocean dead zones have grown to more than 600 million square miles. Penguins washing up on beaches in South America. Why? The plankton soup that normally feeds the Krill could not form because of the ph level of the water was too high. The Krill did not grow and hence the fish that eat them and so on up the food chain. Entire ecosystems are being wiped out in a matter of years. We are pathetic. We look the other way and we let companies like BP destroy what was left of the Gulf of Mexico. I would like to point out that they had a campaign which states they we a new energy company. It was no longer British Petrolum. It was Beyond Pertrolum! What an incredible lie as we learned as hundreds of millions of gallons of crude oil poured into the Gulf of Mexico.
    My guess is that we will be next on the list of extinct species. This can not go on forever and there are no signs that the once greatest nation on earth is going to lift a finger to stop it. We are all doomed. I am glad that I did not have children. Seeing your child suffering and dying such a horrible and painful death has to be heart wrenching. These men are so consumed with greed that they will lie, cheat and steal to get what they want. Go ahead I say. They do not realize it but they will become extinct as well. Hundreds of millions of rotting corpes will lead to biological dissasters that will leave nothing untouched. Unless these people plan on taking a vacation to Mars, they will suffer the same fate as the rest of us. It will simply take a little longer.
    Do you really think that God made planet earth to have mankind come down and destroy it? Really, think for just a moment. God must have tears in his eyes looking down on what mankind has done to this once beautiful planet. We have nearly completly destroyed it! Why?

    • James Agans Says:

      There are a lot of people like me who are as concerned as you are Roy. Greedy people just dont get it. They never have enough. Once money becomes their god, they will actually kill themselves in its pursuit. I can see them sucking on a gold bar trying to extract the water and air they need to survive in the earths last days.

      Last days for man, at least.

      Homo Sapiens? I think not.

  12. Vanessa Says:

    i am very concerned abut the earth running out of petrol and other kinds of fuel, it’s really selfish for us not to help for the future generations because we consumed so much so far

  13. James Agans Says:

    Is it fair to assume that this method of energy production would reduce global warming because CO2 is consumed in the process? Is so this could be a win win situation that must be explored. I agree with the fresh water comment. All components must be considered to come to a sound conclusion.

  14. kent hytken Says:

    After attending a couple Algae oil conferences it seems to me that the issues of growing algae as a future fuel source are water, harvesting and extraction technologies. The economics still do not seem to be viable as a fuel source. Are there any technologies that can be recommended as a game-changing disruptive algae oil technology?

  15. kent hytken Says:

    How much does it cost to produce a gallon of algae?

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