Wednesday, February 7, 2007


One way we all participate in Real Energy is to eat. True, fossil fuels make up a portion of the way we get food, but at base we all rely on photosynthesis to eat. The food chain is grounded in this. Actually, it is better to call it a food web and in a more immediate way than usually taught in school. For most of our lives, when we eat we are not making a bigger us, adding mass to our bodies, we are making a more active us. If we sum up at the end of our lives what we've eaten and subtract what we've eliminated and what's left to bury there is a whole lot of food mass that is missing. Where did it go? It's been pushing up daisies all along.

The carbon that plants pull from the air to construct their bodies is sent right back to them when we eat and then exhale that carbon back to the atmosphere. We are carbon evaporators built to feed plants. Plants are carbon catchers built to feed us. The plants have it a little easier because they don't have to chew.

While the picture of returning our bodies to the solid soil and the web of life is correct, it misses the main show which is the passing back and forth of carbon through the tenuous air. At the center of all this is the process of photosynthesis that frees the carbon we've bound to oxygen and makes it available to make the starch and sugar we eat.

Another way many of us participate in photosynthetically mediated real energy is through combustion. The ethanol that is added to our gasoline to reduce smog comes from plants and those who heat with wood or pellet stoves also use combustion to evaporate carbon back to plants. The question I'd like to look at is: Can we do this more to get away from ghost energy and participate more fully in real energy?

I've mentioned algae before and there is a reason for that. The amount of oil you can get from algae compared to rooted plants is much greater. The main thing is to look at energy per unit area per unit time. For ethanol production we get:

400 gal/acre Corn
665 gal/acre Cane
1000 gal/acre Switchgrass

For oil production we get:

18 gal/acre Corn
48 gal/acre Soy
110 gal/acre Peanut
10,000 gal/acre Algae

And you get about as much ethanol from algae to boot. Ethanol comes in at about 20 Mega Joules per liter and oil comes in at around 33 Mega Joules per liter so taking an acre to be 4047 square meters and a liter to be 0.264 gal and one year to be 3e7 seconds we get 0.25 watts per square meter for corn ethanol, and 0.02 watts per square meter for corn oil. For algae we get about 11 watts per square meters from the oil. The algae is getting close to what we can get from silicon solar cells (about 40 watts per square meter averaged over day and night).

There is a catch though, for the algae, the high efficiency is boosted by using a concentrated source of carbon dioxide such as a power plant. So, a source that could provide something like the amount of liquid fuel we consume for transportation is stuck to consuming fuel in another way. People like to enclose the algae to ensure that the particular strain that is good for producing oil is not out competed by a less useful strain and also to reduce water evaporation but this makes getting the carbon dioxide to the algae a little tough. Sounds like a job for hemoglobin or something like it.

If we demand less in the way of liquid fuels so that we are not setting up a competition between food and fuel, then there is an opportunity to reduce the extra carbon we've put into the atmosphere and still derive some fuels from plants. Not too surprisingly, the method is organic.

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