A recent article I read had the author stating that the burning of ethanol creates significantly less CO2 than the burning of gasoline. This surprises me. I know it produces less CO, but it seems to me that it should not produce that much less CO2.
Now, ethanol may have a slightly higher ratio of C to H compared to gasoline, but on a lb per hp-hour, since one has to burn nearly twice as many pounds, I doubt that it produces less CO2. Does anyone have any hard data?
When ethonol is made, it pulls CO2 out of the atmosphere.
Er...no, it doesn't. Read up on how ethanol is made.
Not exactly. When ethanol is made from petroleum, there is no such effect.
Plants convert CO2, water, and sunlight to make starches, cellulose, and sugars which can be converted to ethanol by fermentation processes. The plants take the CO2 out of the atmosphere regardless of whether ethanol is made or not.
When you burn ethanol, you still create CO2. Not quite as much on a weight basis, but if you want to relate it back to energy output, it would generate more.
But when it is formented, it puts it back in. Is it a 1:1 ratio? I doubt it. I am looking for quantitative answer.
Fermentation yields not only ethanol, but also CO2. So when you FERMENT a carbohydrate, it is not 1:1 production of ethanol.
There is a difference between anaerobic fermentation and aerobic fermentation.
To give a quantitative answer would be oversimplifying the situation.
Maybe the link will help a little.
When plants are grown, they pull carbon out of the air for use in their construction. When they are converted into something other than what they are, they may release it back into the atmosphere, unless they are converted into something stable, like furniture, or housing.
Plants are only "carbon sinks" to the extent that they are not permitted to re-release their carbon.
When corn stalks are ploughed back under as fertilizer and allowed to rot, carbon is released. When wood is burned, it releases its carbon. When leaves or branches fall to the ground and rot, carbon is released. When animal excrement is emitted and rots, carbon is released. When YOU die and your body rots, carbon is released. Need I continue?
If you turn a plant into ethanol, atmospheric carbon is released to the extent that the plant is permitted to decompose. If you take the waste from ethanol production and convert it into a permanent, acrylic-encased statue of Maurice Strong, then that carbon will never be re-released into the atmosphere. You could then say that ethanol production results in lower carbon emissions.
I agree 100%.
Now THAT is quantitative. The question of whether ethanol is a greater or lessor generator of greenhouse gases requires a quantitative answer. What I am looking for are quantitative reports, similar to the ones I CAN find that look at the NET energy output from ethanol as a fuel. These seem to indicate that, yes, there IS a net positive energy output from ethanol as a motor fuel. Depends on how it is grown and generated- if not done properly there is actually a net loss.
I'd like to see something similar for ethanol before we all run off and lock ourselves in on ethanol as the answer to the petroleum shortage.
Looked at in another way, energy in fuels like gasoline and ethanol is stored in carbon bonds. To do a given amount of work, i.e. move a mass (the car) a given distance (to the grocery store) takes a given amount of energy. That energy comes from a given amount of carbon bonds whether you burn alcohol or gasoline, and releases the same amount of carbon to the atmosphere. From that standpoint the only way to reduce carbon is to reduce burning carbon-based fuels, either by simply driving less, or switching to an energy chain that's not dependant on carbon based fuels. One such chain would be nuclear-->electric-->battery-->car, or any other chain that starts with a non-carbon energy source such as wind, geothermal, hydro, solar, tidal, wave, etc.
There are lots of ways to do this, but as long as the incentives and profit motives point to carbon there's going to be carbon, no matter how dire the consequences for our short and long-term future as a society and a species.
JazzMan
Agree mostly. Energy comes from reaction of hydrogen in the fuels with oxygen to give water and energy, and reaction of carbon with oxygen to give CO2 and energy.
The hydrogen oxidation is the most energetic part of the equation. Hydrogen as a fuel would be good with respect to the environment if it could be produced and stored.
Don, if you want quantitative answers, the link I posted to you will give you some of it. You will have to do a complete materials and energy balance to get to the bottom line however. You will likely have to have fuel to cultivate the crops which lead to ethanol production, to harvest them, to prepare them, to distill them, etc. The fate of the waste products might have to be factored in. (Are you going to feed the waste mash to horses or mules to cultivate the crops, or are you going to use a John Deere?)
Cows, horses, people, and bacteria produce methane from metabolism of some of these crops, and methane is also a greenhouse gas. If you recovered it in a digester, you could compress it and use it for fuel too.
In chemistry of this sort, the total path needs to be accounted for, as I am sure you understand. That is one of the reasons there is so much controversy.. the path is not totally clear.
It *CAN* be produced and stored - with amazing ease. The problem is, how much was burned to supply the energy to produce and compress it for storage to begin with?
It's all well and good to say "Yeah, I drive a hydrogen car - The only thing coming out the tailpipe is steam! Zero carbon emissions, baby!" but that doesn't pay any attention to the "X" tons of CO2 that was produced by the coal/oil/LP/corn-cob/buffalo-chip/whatever-fired boiler that spun the turbine that turned the generator that made the electricity to split the water and run the pumps and compressors that made the "Y" cubic feet of compressed hydrogen you pumped into the on-board storage tank to move you "Z" miles down the road.
As you say further on, the whole chain has to be considered, and that chain can be anything from a straight line to a fractal tree complex enough to make the boundaries of the Mandelbrot set look like a precision straightedge.
That's because on balance, carbon (and specifically petrochemical carbon) is the least expensive and most efficient source of automotive energy. It allows maximum productivity out of any given amount of capital.
That situation would invert if the billions of dollars in direct and indirect subsidies and incentives were redirected from petrochemical to non-petrochemical sources of energy.
JazzMan
There was studies that showed,,the enviormental impact was the same as if the crop rotted in the field,,,not to mention lowering the dependence on foregin oil sources,,,the money spent to purchase the fuel,,produce the fuel and so on does not leave our shores,,thus not adding to the trade imbalance A win,,,win situation until better solutions come to market
think green,,,go yellow!!!!!!!!
re info
Technologically, yes, it can be produced with ease. Just takes energy.
The storage question is not as easy. Most research that I have heard about is aimed at bypassing compressed hydrogen, and going to storage as a complex.
To try to compress, deliver, and store quantities of hydrogen gas would take a massive undertaking, and is dangerous. I doubt that it is in our future in this way.
To generate hydrogen under current technology would generate just as much carbon dioxide, or MORE, than just burning the carbonaceous fuels. This is no solution to anything.
Hydrogen burning vehicles already exist. I have ridden in them. But if we are going to save the world, Superman, we are going to have to be able to generate clean and economic hydrogen fuel. Fusion reactors could do it, in theory, but they don't exist right now.
Fission reactors might do it too, but our American experience with fission reactors has been pretty spotty, and the fuel wastes are particularly nasty.
We are pissing away our petroleum reserves at an amazing pace. Even if we stopped totally, today, using hydrocarbons and carbonaceous fuels, global warming would continue for perhaps centuries. And you know we are not going to do this..It would harm our economy.
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