I was thinking about this last night. CO2 is one of the prime concerns in global warming, its one of the things that man produces in abundance. In using biofuels, that is plant based fuels, would we not be helping that problem at the same time? Consider this, plants typically produce their energy by consuming CO2 and H20, with O2 as the byproduct. We burn that fuel using O2 to produce CO2 and H2O as the byproducts. Obviously the equation isn't balanced and we produce far more CO2 than plants consume, but by using plants to produce our fuel aren't we perhaps drastically reducing the amount of excess CO2 produced every year?

 

In theory and in paper -- maybe. In practice -- not as much as you'd think. I'm not familiar with bio-diesel so this may not apply to that, but when making ethanol, one need quite a bit of heat for distillation, and if that comes from a fossil source, you only move the source of CO2 emission to someplace else.

I know Bush got ridiculed for hydrogen, and even here many people don't have a good opinion about H2, but one way to drastically reduce C02 emission is use hydrogen as a fuel in IC engines while generating electricity with nuclear power or with some enviromentally friendly renewable source. (wind or solar)

Another is to have more electric cars. Most peiople's daily commute is well within the range of today's electric cars (100 - 150 miles).

 

A lot of ethanol do not rely on fossil fuels for heat. They use other plant byproducts.

When we burn fossil fuels, we release carbon that was stored in the earth for hundereds of millions of years, and would naturally take a very long time before it ever reached the atmosphere. Essentially, we're adding new carbon to the atmosphere. With biofuels, the plants intake CO2 as they grow, releasing O2. When we burn the biofuels and plant matter, the CO2 is released, to be soaked up again with next years crop.

I guess it comes down to, what is more efficient? A solar cell, or a leaf? I'm guessing the leaf...

 

What byproducts?

You guessed wrong. The solar cell is significantly more efficient than the leaf, though it may not have many of the additional benefits the leaves may provide.

 

I assume he is referring to things like bagasse for sugarcane (what is left when the sugarcane is crushed for it's syrup) or lignin when you are talking about switchgrass and other cellulosic ethanol feedstocks. These can be used to fuel the ethanol production process. Most US ethanol is not made with these, though the future looks bright for switchgrass taking over for corn.

-Jim

 

My understanding of sugar cane processing is that they can practically power nearby towns with all the excess energy the bagasse provides.

 

Yes, bagasse is apparently sufficient when making sugar; however, I doubt that's enough when making ethanol that require at least 2 additional distillation steps. (that Pimental article lists 3, BTW) Now, if someone figures out some tricky way to separate ethanol from water, then it would be all different.

Corn may be a different since it has more burnable waste and less sugar. (starch, to be precise)