I made some claims about the carbon footprint of algae oil in another thread which, well… probably were not correct.
What is the straight dope? How does algae oil compare to gasoline in terms of carbon footprint?
It’s essentially 100% carbon-neutral.
Really? I originally thought that way: that the carbon released by combustion is offset by the carbon soaked up by the algae you’re growing for the next batch.
However, there is only ever one batch of algae growing at any one time. It offsets this year’s algae oil carbon footprint, but the carbon released from all the previous years is not offset.
So I don’t understand. Can you explain how it is carbon neutral?
Just stop at your first sentence.
That cycle makes it carbon-neutral - why would think that to be “neutral” you need to offset anything more than what you emit?
Ideally algal biodiesel is completely carbon-neutral. The algae pulls carbon dioxide from the atmosphere when it makes its oils. Thus there is no net loss or gain of CO2 from the atmosphere with an (ideal) biofuel. Fossil fuels, on the other extreme, release lots of CO2 which hasn’t been part of the atmosphere for tens of millions of years.
Of course, the real world is messier than that. Algae will need some amount of fertilizer, most of which is currently synthesized from fossil fuels in a very energy-hungry process. Storage, transportation, and distribution costs should be comparable to that of fossil fuels. Most estimates I’ve seen say that producing and burning algal fuels (and other biodiesels) will result in much less carbon emission than burning an equivalent amount of fossil fuels. Corn ethanol, on the other hand, doesn’t really reduce carbon emissions (though estimates vary).
Too bad we can’t collect the agricultural runoff that’s causing algae growth where we don’t want it.
Probably because I was looking at it wrong. I viewed the algae grown year after year as only temporarily soaking up carbon, with the carbon released piling up year after year. IOW I was right the first time, then switched to a dumb idea :smack:
Absolutely. In my dream world we grow algae in ponds that collect agricultural runoff and waste water effluent.
Though one of the potential advantages of algae is that you can grind up the remaining solids (after extracting the fuels) and use them as fertilizer in the next batch, with little net loss of nutrients. Some of the experimental technologies are very nearly closed systems.
It’s a common oversimplification that plants remove carbon from the atmosphere. More accurately, growing plants remove carbon from the atmosphere. A plant or collection of plants that isn’t putting on weight (like, say, a mature forest, where the trees are dying and rotting as quickly as they grow) is holding onto carbon, but it’s not taking out any more. Since the algae has to keep on growing back to replace the stuff that was processed into fuel, it keeps on removing carbon.