02-05-2007, 01:29 PM
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Ta ra ra boom de ay
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Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
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more:
"Knowing where to look
Take another look at those graphs above. One thing should strike everyone: a whale of a lot of energy is lost in conversions. The average refinery makes gasoline with 83% efficiency, but engines are so inefficient that more energy goes to refining losses than pushing the vehicle. An ethanol engine is potentially more efficient than the gasoline equivalent, but the conversion from biomass to ethanol loses so much that it takes more biomass energy than crude oil to do the same job! Biomass gasification may be more efficient than Iogen's hydrolization and fermentation, but even a 70%-efficient process yields barely 18% end-to-end efficiency at best. Still, the available energy from biomass looks to be several times the energy we actually use from crude oil. The conclusions are inescapable:
1. There is sufficient biomass energy to replace motor fuel and then some... if the energy is not wasted.
2. Using bio-ethanol in piston engines means taking between 4/5 and 9/10 of the captured energy and throwing it away.
3. Even burning biomass as a replacement for e.g. coal in conventional powerplants means 60% losses or more.
4. It looks impossible to grow enough biomass to take that path.
5. The old paradigm won't work any more. A new systems approach is required.
6. The essence of a successful system will be fewer conversions and minimizing losses.
The potential is enormous. If we can manage to get our hands on 20-odd quads worth of biomass each year, we could replace huge amounts of other demand. Here's a short list of what actually makes it to useful form:
* 17 quads of gasoline into 3-odd quads of useful work.
* 6 quads of diesel fuel into perhaps 2.4 quads of useful work.
* 6.7 quads of natural gas into 2.57 quads of electricity.
* 21 quads of coal into 6.88 quads of electricity.
The useful work we get out of all of these things comes to roughly 15 quads, far less than the 20-odd quads of biofuels we could get; the problem is getting enough of it in useful form. The key to a renewable economy is efficiency, and efficiency is one thing we aren't pushing hard enough. We could certainly do better. But none of this will change as long as people benefit more from the status quo."
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