The New Republic

"But when algae fuel is burned in an engine, guess what — the carbon dioxide is released."

This you call excellent?  I'd call it ignorant.  OF COURSE the CO2 is released.  But since an exactly equal amount of CO2 was fixed in the creation of the biofuel, the net result is a carbon neutral source of solar energy storage.  In principle algae biofuels are no less clean than wind- or solar-generated electricity.  

Now, the rest of the quoted portion may well be correct.  Maybe there are big engineering hurdles to overcome before oilgae makes sense economically or environmentally.  And if harvesting oilgae proves to be as energy intensive as Fehrenbacher suggests it might be, that would obviously put the kibosh on it as a clean-energy solution.  And if energy companies use oilgae farms to scrub their power plant emissions and thereby justify the ongoing use of coal as a fuel to produce electricity, then its development could prove detrimental to the environment.  But none of this can excuse Fehrenbacher's misrepresentation of the basic principle.

Too many journalists on the climate change beat seem ignorant of fundamental concepts such as conservation of matter.  It's all about stoichiometry, baby!  You get out exactly what you put in, no more and no less.

- aeromonas

August 6, 2009 at 8:06am

>>>>This you call excellent?  I'd call it ignorant.  OF COURSE the CO2 is released.  But since an exactly equal amount of CO2 was fixed in the creation of the biofuel, the net result is a carbon neutral source of solar energy storage.<<<<<

Yeah, she notes that in the very next paragraph.

- Brad Plumer

August 6, 2009 at 11:07am

Er, isn't this the definition of carbon neutral? At least as far as the algae is concerned. True, if used to 'double-dip' on CO2 by coal plants, that isn't too bad, halving carbon output.

The real problem I see with algae is that it is in essence solar energy. I'm not sure how you extract anything more than the kW/m2, and probably a lot less, so significant energy extraction requires algae ponds on massive scales, with concomitant water and nutrient requirements. Unless I'm misunderstanding something. I love that the output is petroleum like and can be distributed and refined in the existing infrastructure.

- dbhuff

August 6, 2009 at 11:24am

The key determinant of algae's value as a clean/green fuel is the ratio of the energy consumed in the concentration, distillation, and transportation of the fuel produced to the solar energy stored in the fuel itself.  If that ratio is >1--as, at present, it appears to be for corn-based ethanol--then algae is worthless from a CO2 reduction standpoint.  But if that ratio is substantially <1, then algae may have a future.  It should be noted that so long as this ratio remains <1, oilgae remains entirely carbon neutral.  Even if to make diesel from algae you have to expend 90% as much energy as you get out, so long as you burn oilgae to generate the energy required, you're not adding any additional CO2 to the atmosphere; you're just operating at rather low efficiency.

In the first paragraph you quoted, Fehrenbacher is creating something of a straw man and in the process sowing confusion.  She seems to be implying that because the burning of oilgae releases CO2 that oilgae is IN PRINCIPLE deficient, i.e. not carbon neutral.  This simply isn't the case.  Thereafter she highlights valid concerns as to whether IN PRACTICE oilgae will turn out to be a net CO2 generator and therefore not a useful technology in the move to a carbon-free economy.  Maybe there is good reason to predict that things will turn out this way.  I don't know enough to comment.  But to imply as KF does--"Here's the rub with algae fuels..."--that because when you run your car on oilgae CO2 comes out the tailpipe there's something wrong with them intrinsically is to damn them unfairly.

The key in the future will be to hold algae fuels to the proper standard.  I can see how there might be some risk that even if the necessary efficiencies are never achieved, parties interested in the continued extraction and combustion of fossil fuels could latch onto a technology like oilgae so as to appear to be helping the environment even though the product is worthless as a green substitute fuel, basically using oilgae to "launder" their CO2 emissions just as someone might launder ill-gotten money.

- aeromonas

August 6, 2009 at 12:26pm

Yeah, I think her post basically lines up with what you're saying, but, fair enough, it could've been worded better. The big debate is over whether you need more energy to produce the biofuel than you get, and that's where studies and analyses are still all over the map.

- Brad Plumer

August 6, 2009 at 12:42pm

dbhuff, you're right.  It IS solar energy, and it would require a LOT of surface area.  But 5 kWh--which is about the amount of incident solar energy on 1 sq meter in one day = 0.13 gallons of gasoline.  I read somewhere that these oilgae guys and gals are hoping to operate at 60% efficiency with their energy conversion.  That's WAY more efficient than corn or PV cells, and if realistic would generate something like .08 gallons of gas per m2 per sunny day.  Is it realistic?  Who the hell knows.  

As for the water, they say that waste water would work.  (Sea water too at least in part?  I don't know.)

- aeromonas

August 6, 2009 at 12:44pm

Good points Aero, though I thought sunlight was ~1kW/m2. 60% is a lot better than any but the most expensive triple junction cells used in space, research cells are just getting there now. Unfortunately, in practice, this solar flux would best be found in hot dry places like AZ, not a lot of water, sea or otherwise, a high evaporative coefficient, and not even a lot of coal fired plants to bubble output from...

I had heard that waste water could provide both solution and nutrient, for an added benefit. And as for collection, I understand some of the new genetics are creating algae that secrete oil that can be skimmed off.

I calculated once that with 20% solar cells about 40000 sq mi of cells would provide all our energy needs, just to get an idea of the area needed, even if 1/3rd as much.

- dbhuff

August 6, 2009 at 2:18pm