Yup, another global warming thread. Assume that 100% of auto transportation fuel was biomass and assume that the 53% of our electricity that comes from coal was coming from biomass instead (ie you burn biomass instead of coal in all of the coal plant). How much land would it take to grow that kind of biomass? How much energy in BTU, KJ, or whatever would this require?
It simply can not be done.
There simply isn’t enough land within the US to produce sufficient biomass to produce more than a fraction of our energy requirements. Biomass has such a low in energy density that it is impossible to produce it internationally and ship it to the US.
So in asnwer to your specific questions: it would require an infinite amount of land an in infinite maount of energy.
To which I should add the caveat that my answer assumes no energy enhancement of the biomass. It is certainly possible to use another energy source such as nucelar to increase the energy density of biomass .Such processes essentially make biomass an energy stroage medium rather than an energy source but they have the advantage of producing much cleaner hydrocarbons.
I did a rough calcuation, and the volume of corn production alone is the equivalent of 2.2 billion barrels per-year and the yearly consumption of oil in the US is about 7.3 billion barrels. I don’t know what percent of the corn’s mass can get converted to ethanol and corn oil, but the figures on the potential of biomass seem fishy to me.
One thing to consider is that flex-fuel vehicles can use either E85 (the ethanol-based fuel) or gasoline. So ethanol could be used to suppliment our automotive fuel supply, without necessarily replacing it.
Corn is crap for biomass. Corn gives about 328 gallons of ethanol per acre. Sugarcane gets around 600, switchgrass 1,150 and some crops get up to 1500 per acre. So no, using corn it would be impossible. But if you use switchgrass it would be easier.
What’s the deal with switchgrass? Is it starchier than other crops, produce more mass per-acre, or just grown in Texas?
What’s the deal with switchgrass? Is it starchier than other crops, produce more mass per-acre, or just grown in Texas?
Also, can you use corn oil for bio-diesel?
Bear in mind that everything we eat has been tinkered with - if not outright invented - in order to improve its qualities as food, while no crop has ever been specifically designed for fuel. Give the bioengineers a few years and I’m sure they’ll come up with a plant that gives us an energy yield ten times as high as anything that exists in nature.
Almost certainly not. While you are correct that few plants have been specifically bred to produce fuel the processes we are talkng about are not significantly different from those involved in producing food or plant biomass. At the end of the day sugar is sugar, and whether a plant is bred to produce sugar for adding to coffee for sugar for bacterial fermentation the breeding process is identical. The same is true for biomass for plant fired power stations, with plants having evolved for eons to produce maximal biomass.
There really isn’t a lot of scope for improvement in this process.
Another thing to remember is that the crop yields we’re used to are based on modern mechanical farming techniques. Simply put, it takes a lot of fuel to grow crops. I’ve heard that it would take more than a gallon of fuel to grow the crops that would produce a gallon of fuel.
That is what Cecil says. It is certainly true for current US maize based ethanol production though it may not be for large scale cane based ethanol production…
I’m curious about that switchgrass that Wesley Clark mentioned. Wikipedia says that it’s being seriously considered, but there’s disagreement on what its yield of ethanol would be. In any case, it’s a native plant species that grows throughout the midwest, so hopefully it wouldn’t require as much effort to grow as corn does.
Question: what percentage of the solar energy deposited in a field of switchgrass can be later converted to electricity?
Well that’s assuming we will breed plants the same as the past, but step in genetic engineering and I can see better fuel plants AND better microbs to digest it, being able to convert celulose and other parts along with sugars, perhaps converting it directly to oils which would eliminate the expensive distilling part.
Also a clarification please on the bold part of yor post, AFAIK alcohol is made with yeast not bacterial fermentation, do they use bacteria for this now? I think they can use bacteria for methane production.
I doubt anyone has even bothered to find out. It would be trivial.
Photosynthesis is terribly inefficient, with less than 5% of the energy falling on a plant being converted into sugar. Then factor in that less than 1% of that sugar is converted into biomass over daily or longer timescales. Then figure in that at least 50% of that biomass is below ground and hence unobtainable.
Even if we assume that our process for conversion of biomass to electricity is 25% efficient then we have 0.05 * 0.01 * 0.5 * 0.25 = 0.00625 % of the solar energy deposited in a field of switchgrass being converted to electricity. And that is the best case. In reality I would expect less than one hundred-thousandth of percent would actually be converted.
That’s certainly possible though at the moment the real improvements are in the nuts and bolts technology, not the biotech.
No, that was what is technically termed a brain fart. IOW I stuffed up. Glad someone spotted it. I imagine there would be some bacterial fermentation used especially for methanol production, but for sugar fermentation you’re quite correct AFAIK.