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Here's an even harsher assessment of plant-derived ethanols from Dr. Tad Patzek, chairman of the Department of Petroleum & Geosystems Engineering at The Univers
by gojomo 14y ago
Here's an even harsher assessment of plant-derived ethanols from Dr. Tad Patzek, chairman of the Department of Petroleum & Geosystems Engineering at The University of Texas at Austin:
Basically, [corn] ethanol is obtained from burning methane, coal, diesel fuel, gasoline, corn kernels, soil and environment. We destroy perhaps as many as 7 units of free energy in the environment and human economy to produce 1 unit of free energy as corn ethanol, and make a few clueless environmentalists happier and a few super rich corporations richer. The story is even worse for switchgrass ethanol.
(As quoted from http://www.theoildrum.com/node/9619 http://www.theoildrum.com/node/9619 )
- uvdiv 14y agoWe destroy perhaps as many as 7 units of free energy in the environment and human economy to produce 1 unit of free energy as corn ethanol And yet they still make a profit, and it is still highly rational to do so. Because it turns out 1 Joule of liquid hydrocarbons is more valuable than 7 Joules of methane or coal or sunshine.
- alsocasey 14y agoA comment below mentions subsidies - that's certainly part of the answer. In addition, for mobile applications, not all energy sources are equal. Transportability (stability, energy density, etc.) also contribute to liquid hydrocarbon Joules being more valuable than methane, coal or sunshine.
- sliverstorm 14y agoTangent- we have LPG, and from what I understand it's actually very successful in niche applications. Have we tried liquefied methane gas? We have many more sources of methane than propane.
- surrealize 14y agoMethane has a much lower boiling point (-182 C) than propane (-42 C), so liquefying methane (and keeping it liquid) is substantially harder.
- sliverstorm 14y agoCan you not simply roughly double the pressure you store it at? Or is LPG already stored at borderline risky pressures.
- DaniFong 14y agoVapor pressure is exponentially related to temperature; you really need to keep it cold.
- surrealize 14y agoIf you really want to produce a liquid transportation fuel from methane, the usual approach is F-T synthesis: http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process Generally, it hasn't been very economical to do so, although I wonder what the numbers are now that we've got so much natural gas production in the US.
- maxerickson 14y agoNatural gas is increasingly being shipped on the oceans: http://en.m.wikipedia.org/wiki/LNG_carrier http://en.m.wikipedia.org/wiki/LNG_carrier When used as a portable fuel it is usually just compressed.
- gojomo 14y agoBut would they make a profit without government subsidies and set-asides for corn-derived fuels? That's what is at issue.
- jules 14y agoThis is why a tax on carbon is better than subsidies. Then that 7 fossile fuel Joules to 1 biofuel Joule would be a huge loss. Incentivize what you actually want to optimize.
- raverbashing 14y agoHe's talking about corn. Generalizing this to "plant-derived ethanols" is a stretch But yes, Corn ethanol is not good for a series of reasons. Other plant based ethanols may not suffer from the same problems. Ok, I read the article, typical "only oil is good" atitude. And by the way: efficiency with respect to sunlight doesn't matter because sunlight is free. (enough) free * anything -> free (It matters in respect to other processes)
- gojomo 14y agoHe also mentions switchgrass as a problematic source. What other plant sources of ethanol should be considered that would offer a better tradeoff?
- mr_luc 14y agoSugarcane. There are still problems with any plant-based biofuels, but they're problems with scaling, crop rotation, pesticides, and the current state of the art of ag in countries where sugarcane is grown. But the energy return of sugarcane ethanol is high enough to make it non-silly.
- niels_olson 14y agoCompared to solar, they're all silly. You live the glow a giant nuclear reactor, so large it is contained only by its own gravity. A .01% yield on the energy incident on earth would power everything we ever need.
- raverbashing 14y agoExcept for nuclear, geothermal and tidal wave generation (and other lesser used energy sources) all energy in planet Earth is solar, accumulated during different time frames. Sure, solar is great, except current technology is really bad at using it.
- Evbn 14y ago
- johnrgrace 14y agoAlmost everything on TheOildrum.com is not a mainstream view, some of the minority views are right many are not. An ethanol plant has more outputs than ethanol. Distillers Grain is a major output stream, which is a useful lifestock feed. The paper, which I have read, counts as energy inputs all the energy required to make ALL of the inputs and takes every step possible to make the largest energy input amount possible. Ethanol isn't the most efficent process, but the tech is being pushed ahead and the end output is a liquid high energy density fuel which is more useful that some of the energy input into the system. And yes, I am energy economist iaee.org
- btilly 14y agoAs an energy economist would you mind commenting on Elon Musk's assertion that the best case with a perfect plant for making biofuel, the efficiency per unit of land used is still 2 orders of magnitude less than capturing energy with solar cells? He also claimed that for most nuclear power plants, if you covered them and their exclusion zones with solar cells, you'd generate more energy than the plant itself generates. (Both assertions seem pretty strong. Both were made during the interview at Oxford that was put online yesterday.)
- enraged_camel 14y agoMusk's assertion regarding biofuels was correct, but I think it was made within the context of using them as fuel. He didn't discuss many side-products that are generated during the production of biofuels.
- dsl 14y agoThe problem with counting "side effect" products is nobody ever takes into account the supply/demand for that product. Sure making enough biofuel for the entire US produces 100 tons of X. But if the worldwide demand for X is 5 tons, then you've now generated 95 tons of waste that needs to be disposed of.
- 14y ago