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How bad for the climate is algal oil?
Alex Steffen, 16 Jul 09

Lots of people are buzzing about algal fuels, which promise to turn vats of seawater and CO2 into biofuels much like oil, and seem real enough that ExxonMobil is investing $600 million in the technology to make them.

But here's the question I can't seem to find answered: how much carbon is actually saved by running a car on algal oil instead of fossil oil? The press releases all pitch this as ALGAE THAT EAT CO2! Yet it would seem that the burning of the oil would release much of that CO2 back into the atmosphere, no? While I assume there are GHG savings in using that feedstock CO2 (presumably from coal plants or whatever) to create an oil-substitute instead of just releasing it into the atmosphere, this is also clearly not a carbon-neutral energy source (as implied by proponents). And, of course, changing fuels does nothing at all to change all the other climate impacts of cars.

Anyone got numbers, or educated perspectives on the issue? Good tech, half-measure or greenwash?

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A recent article on Technology Review discussed a new startup (now funded by Dow) developing algal ethanol, which claimed an 5.5:1 energy balance, comparable to cellulosic ethanol.

So you're right that it's not carbon neutral, but it's certainly not bad.

In the case of Algenol (as the company is called), the growth medium is saltwater, and for every unit of ethanol produced, they also produce a unit of fresh water. I'm not sure if that's included in the energy balance calculation above, but I would assume not, and desalinating water is a pretty energy intensive activity, so it's good news all around.

Posted by: Andrew on 16 Jul 09

My understanding is that the algal fuel systems all require concentrated CO2 sources (like a power plant, not the atmosphere) meaning that even at the very most optimistic, if you assume no energy required to set up the algae system or run it, you are going to at most get roughly double the usable energy per unit CO2 emitted. One part from the coal being burned, and another from the algal fuel being burned in a vehicle, at which point the CO2 is finally released into the atmosphere.

It might be more interesting to look at the carbon emitted per unit energy produced for a semi-closed-loop algal fuel power plant, in which the algal fuel is burned to produce electricity and/or heat instead of being used in vehicles, and the emissions recycled on-site. There'd certainly be energetic losses, and you'd need some other power source to make up for those, but it would be an interesting energy balance to look at.

Of course, you'd also need a vast, sunny area over which to spread the algae. What's their energy efficiency, as far as turning incident sunlight into useful chemical bonds? How does it compare to solar thermal or PV? Is algae really an efficient energy collection system, or is it only interesting because it allows that energy to be stored chemically? Even the most efficient macroscopic plants are depressingly inefficient at turning light into chemical bonds.

Posted by: Zane Selvans on 16 Jul 09

Smart comments. Eager to hear more.

The desalination angle is one I hadn't heard yet.

"Is algae really an efficient energy collection system, or is it only interesting because it allows that energy to be stored chemically?" Then, too, I have friends who maintain that the ecoefficiency of biofuels has always been beside the point, that their main purpose is to provide cover for continued use of oil for transport "in the meantime..." Not sure whether I believe that, but also not sure that it's possible to plumb the depths of oil company cynicism.

Posted by: Alex Steffen on 16 Jul 09

Here's what algae is good for:

Animal feed protein

It can displace about 50% of the CO2 foot print in agriculture.

There is some work on this right now:

There is potential for algae oil, but I've been looking at algae as a game-changer since the early 90s and the only thing real that I've seen is protein. If you're really interested, I could go into the touchstones of a viable algae fuel project, but no one is near it yet.

Posted by: James Bowery on 16 Jul 09

Oh, check this out too:

Posted by: James Bowery on 16 Jul 09

Algae is renewable, does not affect the food channel and consumes CO2. To learn more about the fast-track algae industry, you may want to check out this website: www.nationalalgaeassociation. They are the first algae trade association in the U.S.

Posted by: algaepreneur on 17 Jul 09

I’ve read many speculative reports claiming fuels made from algae do not produce a lot of the kinds of harmful emissions that petroleum products do because algae does not contain many toxins that crude oil does ( that is when algae is refined into gasoline or diesel fuel instead of ethanol). And I’ve seen reports from algae fuel producers claiming their testing shows that this is indeed the case. These are pollutants that are harmful to health and the environment as well as have been shown to cause changes in climate, new research that demonstrates clearly that weather patterns are dramatically effected by low level ozone causing pollutants and the ozone formation process itself.

This research is spearheaded by professor Drew Shindell of NASA where he proves CO2 may not be what is causing what we have come to call global warming. His theory is supported by James Hansen, also of NASA (Al Gores chief climate adviser for his book and movie).

The understanding of the causes of climate change is evolving very quickly in the scientific community but not so much politically. Perhaps we need more conclusive evidence of whether or not algae fuels truly have cleaner burning properties since it appears CO2 is not our most worrisome greenhouse gas as far as solving the issue of climate change. Shindell recommends we retool industries along with a amending auto and truck emissions to produce less health damaging pollutants while paying for it by reducing health costs.

Quite frankly I’m surprised that given the fact that we are talking about health care, energy, and climate issues so divisively in Washington, all at the same time, that no one has brought up this side of the issue.

Posted by: Bobby Fontaine on 17 Jul 09

Hadn't heard about protein. Interesting.

"Algae... consumes CO2."

Does it, though? Doesn't most of the CO2 get re-emitted when the algal oil is burned?

Posted by: Alex Steffen on 17 Jul 09

Bio-fuels vs. fossil fuels: Burning fossil fuel releases carbon that has been stored (sequestered) for thousands and thousands of years (a bad thing); burning bio-fuels (e.g. sugar cane ethanol) releases carbon that has been recently captured (not as bad).

Carbon-free hydrogen would be best!

Posted by: lunatic on 17 Jul 09

I absolutely agree that the original question needs careful scrutiny, I would also like to propose that we look at the source "fuel" for growing the algae.

I'm kind of curious about using sewage to feed the algae. It's not going away before we are AND it's difficult to treat.

Check out this company in New Zealand:

This process is also mentioned briefly in US Biodiesel Advocate Josh Tickell's film FUEL.

Really interesting film documenting the long, often very dark, history of the fuel business ending with a smart and hopeful pitch for a number of new ideas that are still in development.

Posted by: Kristy b. on 17 Jul 09

"Bio-fuels vs. fossil fuels: Burning fossil fuel releases carbon that has been stored (sequestered) for thousands and thousands of years (a bad thing); burning bio-fuels (e.g. sugar cane ethanol) releases carbon that has been recently captured (not as bad)."

Except that the inputs to that sugar cane are all GHG-generating, from farm equipment to fertilizers.

I don't share the view that biofuels are necessarily any great improvement, and when they compete for cropland on a hungry planet, I think there's a quite valid argument that they can be immoral.

Posted by: Alex Steffen on 17 Jul 09

First, let us be clear that the objective of biofuel from algae is both an effort to provide fuel for transportation AND to reduce the total CO2 going into the atmosphere. It is true that when we burn the biofuel we will be putting the carbon into the atmosphere, but we will have gotten almost twice the energy out of it. We need a liquid fuel because it's the most easily handled for transportation. Diesel has four times the energy of ethanol and diesel engines are roughly twice as efficient as gasoline engines. Algae it so attractive because it grows several orders of magnitude faster than other oil crops like soy bean and sun flower/canola and the surface used is water.
I know our farmers won't want to hear this, but ethanol is inherently a poor choice of fuels. Mostly, we make it from corn, a food crop of which there is a world shortage. Secondly, along with all the energy and petroleum base fertilizers used in growing and harvesting it, half of the corn sugar's Carbon is released in fermentation.

Posted by: Gray Kinnie on 17 Jul 09

Nothing is perfect, but compared to other short cycle biomass carriers of carbon used in combustion I became interested in algae because it has high productivity per acre and has a useful by product.
In discussing energy efficiency the quality of the energy needs to be considered as Zane Selvens pointed out. I prefer that power plant CO2 is sequestered, and decarbonised hydrogen is used for transport fuel, as lunatic notes.
However efficiency needs to be compared to the available alternative rather than the perfect solution with no investment constraints. For some countries and power generator sequestration is difficult, and sunlight + flue gas + warm water will be a efficient and sustainable displacement of oil for transport over the short to medium term.
I find it difficult to be certain of what is best without agreeing the context of the question.

Posted by: Alastair on 18 Jul 09

So, a crude summary of our discussion about energy sources releasing CO2 into the atmosphere might be this: Crop-based fuels are better than fossil fuels; algae-based fuels would be better than crop-based fuels; and carbon-free hydrogen would be best of all.

Now, if the U.S. can only build a network of hydrogen infrastructure, just like we built America's interstate highway system since WWII.

Posted by: lunatic on 18 Jul 09

Any consideration of algal fuel technology needs to include the side benefits that accompany it. First, drop-in liquid fuels are important in making rapid change rather than building a hydrogen economy from scratch. Second, the side products of algal oil can be used to replace plant matter currently being grown using fossil inputs. Third, the land used to grow the algae needs to be unused or underutilized, not valuable farm ground.

IMO if carbon taxes were in place algal technology would rapidly become cost effective. The true costs of fossil fuel need to be added to the fuel itself, and that will mean large increases in fossil fuel costs at the pump, which of course will reduce demand.

Posted by: Dave on 18 Jul 09

The University of Coimbra is expected to release an article in August regarding the production of algal oil.

The University has the worlds largest algaetech (over 13.000 samples of living algae). They also developed a special technology to increase the reproduction/growth rate of the algae. After years of investigation they have selected a micro algae with an awesome growth rate. After "harvesting" 50% of the algae is high quality oil.
In my opinion (correct me if I am wrong) that means that the algae will consume twice the carbon that will be realeased during the burning of the oil.

Posted by: Simão on 18 Jul 09

The thing to understand about protein is that agricultural fossil fuel consumption is largely about producing protein. More efficient mens of producing protein means less CO2 emissions, not because of carbon capture by protein, but by less emissions during its production. Some sequestration can be achieved by better handling of animal and human manure as well, but that is another issue. A preview excerpt from the Diogenes paper:


Photosynthesis consumes carbon dioxide and can produce food. Including animal fodder, potential world-wide demand for high quality food is nearly 20 times the carbon content of US fossil fuel electric effluent. This is calculated as follows:

Higher quality food – primarily protein – is part of a food chain that generally claims 9 out of 10 food calories for itself. The carbon content of potential world food (calculated as US per capita, all as protein) consumption by humans (at 1.2 billion metric tons per year) is nearly double the carbon content of fossil fuel electric plant effluent of the United States (at about 0.68 billion metric tons per year).

7e9persons*3500foodcal/day/person @ (44189*12/1011041.95)*1g/4foodcal
= Potential food carbon
= 1.17253E+09 metricton/year

Eq 1


= US fossil fuel electric effluent carbon
= 6.81818E+08 metricton/year

Eq 2

The animal fodder equivalent of alfalfa protein at 19cents/0.18kg, would have a market value of over a dollar/kg. In practice, there are no photosynthetic processes that produce pure protein. The best that we can practically do is about 60% protein in algae grown under high nitrogen conditions (See page 90 of this link). Ignoring the non-protein 40% of algal biomass (even though it might be of some food value) -- we can reasonably expect to get 60 cents per kg of algae if the right species is cultivated under high nitrogen conditions.

Fortunately, algae also has the highest photosynthetic efficiency of any potential cultivar. Algae insolated areal biomass production in tubular photobioreactors has been demonstrated at an annualized rate of over 70g/m^2/day (See Table 3 of this link). Scaling back expectations based on a variety of real world factors elucidated below (primarily to reduce photobioreactor costs and externalities) we will subsequently describe a low-cost tubular photobioreactor that will achieve only half of that efficiency, or about 35g/m^2/day; similar to that demonstrated in open raceway ponds under ideal conditions. By lowering the environmental impact and cost of the tubular photobioreactor, it becomes profitable to convert all fossil fuel power plants to emit a pure CO2 stream for sale as an agricultural input commodity. At the same time, these plants are converted to zero emissions systems that have end-to-end efficiencies as high as currently deployed systems.

Posted by: James Bowery on 18 Jul 09

Algae is carbon neutral because burning algal fuel releases into the atmosphere the same amount of CO2 algae consumes when growing. In those cases when algae is farmed on emissions from coal plants, carbonic emissions are recycled and reduction in emissions comes from the fact that the same volume of emissions was released both producing electricity and moving cars, otherwise an additional amount of carbon fuels has to be burned as motor fuel increasing CO2 emissions.

It should be probably pointed out that for the planet to become carbon neutral does not mean that humanity should become one. Nature has its own ways of absorbing and recycling CO2 like trees growing faster, a phenomena recently observed. The problem was created because the system got overwhelmed by the volume of CO2 released into the atmosphere over the last decades. For the balance to be restored CO2 emissions should be simply reduced, it does not mean that all of them should be recycled somehow.

Posted by: NB on 22 Jul 09

Your right to highlight the fact that when the combustion of the algaloil occurs in the vehicle Carbon is released into the atmosphere.

The issue here is the sourse of carbon - most likely to be the CO2 emmissions from Coal fired power plants (or perhaps gas fired).

Not all the carbon source is converted into a fuel.

In Australia for example, the algae-oil-CO2 process produces 3 main usuable and valuable products

1. Fuel Oil (about 30%)
2. Algae meal (about 60%) for animal fodder
3. Clean water supply

Now the second product of algae meal ends up int he food chain which is partially recirculated int he eco-system (although methane is a carbon source due to animal flatulence etc)

The Fuel oil when burnt will produce carbon but makes up 30% of the carbon that went into the algae converson process.

It seems to me that in the future perhaps even vehicles will store their carbon emmissions onboard the vehicle ins ome way and dispose of them when they fill up with fuel at the service station.

This will close the carbon loop in a significant way.

Its a good idea but like most things you need to look at the energy input and the costs to environment JUST so we can continue our decadent life styles in their usual unsustainable manner.

In the end human civilisations will have to change OR be forced to change or become extinct.

Humans may have great capacity for creativity but we also have great capacity for global destruction and following suicidal paths


Posted by: Rock on 30 Jul 09

The concept of low carbon dioxide emission algae fuel brings to my mind the energy conservation versus energy efficiency issue.

It may be much more efficient in terms of carbon released to burn algae than fossil fuels, but it will not necessarily reduce the amount of overall emissions if people use more fuel. For instance, if you halve the CO2 emissions of your fuel, but double the amount of cars being driven, you've gotten nowhere. Carbon-free hydrogen is the only way to go.

Posted by: V on 30 Jul 09

A lot of you are mentioning hydrogen, but we don't seem anywhere near finding a sustainable hydrogen source that can be used for mass production. The methods to obtain H2 today either release CO2, use as much energy as is gotten out, or can't be realized on a large scale (microbes, etc.).

Posted by: Jeff on 8 Aug 09

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