 | Food Miles in Australia | The Oil Drum: Australia/New Zealand | The Bullroarer - Saturday 1 December 2007 |  |
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While the jury is still out on the practicality of large scale biofuel production from algae, I feel the need to point out this doesn't sequester much carbon, as the resulting fuel gets burnt and the carbon ends up in the atmosphere.
All you have done is got a second go at the carbon emissions from the original power plant, using sunlight to help you reconstitute them as liquid fuels for the second pass.
This helps reduce total emissions for the energy produced, but doesn't actual stop the carbon flow into the atmosphere.
True indeed. However, if the stationary plants use biomass instead of fossil fuel, reprocessing of the CO2 into liquid fuels takes a second bite at the captured carbon before it goes back to the atmosphere (which makes it more difficult to recapture).
Good point - I hadn't thought of that - usually people twin algae with coal plants.
The remaining algae pulp gets sequestered in the soil. So it depends on how much oil gets extracted from the algae. This depends on the commercial viability of the algae species and the extraction processes used. I won't bother going into the details (since, as you imply, they depend on a thin web of assumptions and guesses), but if you are getting carbon credits for sequestering and getting paid for the carbon ash as a soil improver, then the commercials tend to favor a fast-growing algae that is only 40% oil, rather than a slow-growing algae at 75% oil.
So, actually, it is quite possible that in a commercial process quite a bit of carbon ends up sequestered (about 50-60%).
David C.
Interesting - I'd always thought that going for maximum oil production efficiency would be the goal, but if carbon credits are taken into account your scenario makes a lot of sense.