Wrong trophic level!

Thanks to our inestimable leader, the topic of making fuel from corn and other cellulose sources has received renewed airplay. Unfortunately it suffers from the same problem as every other time this has been discussed:Cellulose Molecule Cellulose is an incredibly long-chain hydrocarbon that looks very little like the alkanes that predominate in fuel oil. For reference, existing gasoline consists of 7-11 carbon hydrocarbons. Because cellulose is almost all sugars, it has to be degraded almost down to nothing, aka ethanol.Ethanol Molecule By the time you get to ethanol, you have not only broken the expensive 1,4 bond between individual sucrose molecules, you’ve also broken the 6 sugar beta-glucose subunits into three pieces. Needless to say, most of the energy in this process has gone to whatever organism or chemical operation you used to break it down that far.

This is why most traditional ethanol producing factories start from the corn kernels from which they can get free, or more cheaply linked, polysachharides. Which is fine, except for the fact that the ears represent a fraction of the mass of the corn plant, and the sugars represent a fraction of the mass of the ear. Additionally, it takes 125 days or so before a corn plant is ready to harvest, so even if you could theoretically get energy from the entire corn plant, you would get 79 * 1015 Btu out of the entire US corn harvest, which would fall short of our current energy demands by over 10 billion Btu/annum.

This problem persists with all macroatomic plants: the bits that are easy to degrade are a small fraction of the plant, and the rest is mostly cellulose.

If you switch to prokaryotes, however, the situation is much better. Take Anabaena, a filamentous bacteria that is incredibly common. In the right conditions, you can get exponential growth that covers the surface of your medium within a month. The bulk of anabaena consists of a polysaccharide mucilage, phospholipids (fat), and peptidoglycan. Peptidoglycan consists of polysaccharides connected with small proteins. We are awash in enzymes that will degrade these molecules; even our tears contain peptidoglycan degrading enzymes.

The phospholipids can be broken down into hydrocarbons (fatty acids) and glycerine fairly easily, using processes similar to those used to make soap. The peptidoglycans can be degraded with the aforementioned enzymes, and the (cheaply linked) polysachharides can be degraded any number of ways.

All this means more of Anabaena can be cheaply utilized to make gasoline-like substances. Even using batch methods, it can be harvested almost 12 times a year and will give you a much larger annual yield than the same acerage devoted to corn. Furthermore, I just picked Anabena because it is very common; there are literally millions of species of bacteria and other microorganisms out there, some of which most certainly are made up of molecules even more amenable to this form of transformation.

Furthermore, breeding bacteria is a process that takes months, not years, so we can selectively breed whatever strains we’re using for more optimal yield.

The general idea that living biomass is the most likely replacement for fossil biomass is dead on: the notion that it will come from plants or other macroorganisms is absurd.

2 thoughts on “Wrong trophic level!

  1. I agree 100% with what you’re saying here, Ethan, as far as where we get our fuel-biomass from. However, living in the corn capitol of the world (or is it pork?), I have a newfound ‘respect’ for the way the infrastructure here is setup. Keep in mind that a percentage of the corn grown here is sold for feed (actually, that’s where most of it goes-to feeding animals; yet another inefficient venture). I’d say about 80% of the corn America grows is feed corn, the other 20% is human consumable. Also keep in mind that the majority of farming is privately done; getting these people to switch over to something different is not only expensive for them (a typical combine costs anywhere from 100,000$ to 500,000$), many mid-western folks are just plain stubborn and wouldnt like the idea of changing to something that their daddy, and grand-daddy never had to do.

    And yes, the entire corn plant is procees-able. Not all of it is as rich in sugars as the kernals are, but the processing places around here use all, or almost all of the plant.

    Let’s not forget soy beans either. 🙂

    As with many, many other things I see ‘wrong’ in this country, until the infrastructure is changed, nothing else will. Sadly, since our country revolves around a short term profit, most people would rather keep going in the ‘wrong’ direction and make more $$ than spend a little now and have a more viable solution for the long term. I think figuring out how to get around that blockage will be a much bigger solution than where we get our biomass/fuel/etc. But that’s just me.

  2. If I succeed in my research agenda, I will be able to provide farmers with a “seed kit” of algae, some long transparent plastic tubes for them to float in and the associated pump miscellany along with “instant ocean: just add salt and water”. Using whatever spare sewage they have (pig shit wil be particularly useful) they mix some instant ocean and put the tubes down on a fallow field.

    I am a few days away from having harder numbers on this, but I believe they will be able to generate the oil they will need to ‘operate’ 5-10 acres for every acre they devote to these tubes.

    The tubes will need to be set apart from each other to help keep the average temp of the water around 20ºC during warmer months, and the fact that they will displace 0.5m2*length earth in order to maintain their shape, the rows around the crop can be used as decomposition windrows during the winter months to keep the temperature of the water up.

    The difference between cultivating Anabena and growing soybeans is that with soybeans, as with all plants, a substantial portion of the light energy and nutrient resources the plant utilizes in the construction of its body that is not rendered into the highest margin terminal crop.

    Anabena requires nothing further than the right pH, the right salinity, enough dissolved CO2 in the water, and the right temperature. Given those conditions and no predators it grows exponentially.

    We talked, once upon a time, about how going from trees to grass gets you better yield. One factor is that you can harvest hemp two to four times a year, while trees can only be harvested every 25 years. Another is that hemp has less, lignin than a tree – precisely because it is smaller, and needs less structural support – and thus a greater proportion of the biomass goes directly to the intended product.

    Of course, the one other thing you have to assume farmers can operate is a distillery. I think history is on my side on this one.

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