Would CO2 emissions from ethanol production trump or equal emmissions from fossil sources?

Question

I'm thinking not, but a buddy of mine insisted that mass ethanol production would be just as bad as current CO2 emmissions with a fossil based fuel diet. I would think the increase in biomass from plant life might factor in, and also that much of the CO2 might be harvested to create optimal growth condition in "plant growth factories" etc...assuming hydroponic media would be used. Maybe I'm wrong, but it seems like the CO2 consumption of the plants harvested would outweigh the CO2 released during ethanol fermentation.

Answer 1

Without access to a lot more detailed information on the complexity of gasoline combustion (given the diversity of hydrocarbons in gasoline), the best I can say is that ethanol combustion should produce less CO2 than gasoline because it has only 2 carbon atoms in its chain while gasoline hydrocarbons contain 5-12 carbon atoms. However, any time you perform combustion with stoichiometric air (normal atmospheric air), the products of the reaction will vary, especially with varying temperatures and reaction conditions.

The big problem with ethanol, besides the fact that it still introduces greenhouse gases into the atmosphere, is that the demand for fuel *GREATLY EXCEEDS* our ability to provide it through ethanol. Brazil can do it (at a cost to its poorest citizens, some of whom have lost their land to agri-business so the necessary crops could be grown and have had to deal with higher food prices as a result), but the entire world can't.

Plants will definitely confine atmospheric CO2, but the process is slow and would take a long time, considering that we release approximately 3 billion metric tons carbon per year from petroleum alone, and have been producing over 2 billion metric tons per year (again, from petroleum only) since the 1970's. Currently, we produce approximately 6.5 billion metric tons of carbon annually, which include petroleum, natural gas, coal, and cement production.

But all of this doesn't matter much anyway. If global warming doesn't get us (by dramatically changing the environment we depend on) in the not-to-distant future, then "peak oil" (discussed in the "Future of Oil" link below) will with another decade or two... if we're lucky.

Answer 2

The CO2 emissions from burning ethanol would be the same as burning gasoline. However, assuming that we produce the ethanol from fermentation of corn or grass, the growth of the plants would consume an equal amount of CO2. This makes it better for controlling greenhouse gases than fossil fuels.

Other things to consider, though. 1) The ethanol production requires more energy than refining oil to make gasoline, so we might have to supplement with a lot of solar and wind to make up the difference. 2) No ethanol production process is perfectly efficient, so a large amount of carbon from the plants is going to have to be either recycled as fertilizer or buried in landfills. (Or burned for power) This could help shift the CO2 emissions a bit more in favor of ethanol.

Answer 3

Fossil fuels aren't really required to produce ethanol. Mainly fossil fuels are used because they are easy to get a hold of. However, an ethanol production plant could take what is left of the feedstock after production and make bio-fuel tablets for this purpose. Corn ethanol leaves half of the mass that is usually resold as cattle feed.

So nothing is definite on this issue.

Answer 4

No it would not. Chemically the burning of ethanol produces FAR less CO2 and far more O2. Your friend needs a chemistry class. Also, no the harvest really wouldn't do anything to even put a .0001% difference in atomospheric CO2.

Answer 5

Your friend sounds like a Bush croony.

Burning ethanol produces far less CO2 and more water. Also, you are correct in saying that growing corn reduces CO2.