According to the US Census Bureau estimates there are some 237,000,000 driving age adults living in the US. Of that number there are some 291,000,000 registered drivers (i'm guessing this number includes visitors), and 231,000,000 registered vehicles.
Now, the average MPG for most vehicles is around 22 (cars are higher than SUVs and trucks), and most cars have a 15 gallon tank meaning that cars, on average, get about 300 miles on a tank. i'm not providing references to those numbers because they only go to provide you with an understanding about how the heck we manage to consume about 7 million barrels of petroleum a day.
Let me repeat that so we're clear, that's 7 million barrels (294,000,000 gallons) a day. i'll note that the biofuel site EnergyFutureCoalition.org marks this as being 20 million barrels of fuel a day, so i'm actually being pretty conservative here.
Speaking of being conservative, i'll take the following numbers from the same bio-fuels site. According to that same page, it requires approximately a third of a bushel of corn to generate one gallon of ethanol. Well, at an estimated 600 kernels per ear and 90,000 kernels per bushel, that's about 150 ears per bushel, or 100 50 ears per gallon of ethanol (*Number adjusted per Josh's comments. Late night math skillz strike again. Still, i'm trying my best to be as optimistic with these numbers as i can). Now, let's assume that growers maximize their harvest at about 700 ears per acre, so that roughly translates to about 14 gallons per acre.
This means that to produce the required 294 Million gallons of ethanol required to replace the gas demands, we'd require 21,000,000 acres of corn. Ok, ok. Ethanol only offsets 10-15% of demand, so we're only talking about needing 2,100,000 acres of farmland per day to be converted into fuel. Oh, wait, that's per-day isn't it? So that means that we'd actually need 766,500,000 total acres of corn to sate the need. we could probably shave a quarter off that because the southern states can produce two yields per growing year, so we're only really talking about 574,875,000 acres for growing corn.
Now realize that the US only has a total land area of about 2.3 billion acres. Of that only 20% (455,000,000 acres) is considered "cropland".
Yeah, i'm not really a big backer of BioFuel as a viable alternative energy source.
(and before someone brings it up, switchgrass has many of the same growth and harvesting issues as corn does, although it's far less resource intensive to grow. Yeah, i didn't even touch on the fact that somehow these millions of acres need to be enriched with nitrogen from some unknown source in order to maintain their constant supply. It's not like we can let the nation lie fallow for a year or two.)
well it doesn't make much difference in the final conclusion, but it does half the number:
it requires approximately a third of a bushel of corn to generate one gallon of ethanol.
Well, at an estimated 600 kernels per ear and 90,000 kernels per bushel, that's about 150 ears per bushel
My math says that 150 ears times 1/3 is 50 ears of corn, not 100.
Again, the final conclussion is unchanged, as we're still an order of magnitude off with 28 billion compared to 455 million, but it is a significant error in the calculation.
–jr
Be easier to higher the age to drive to 21, limit each household to a max of 2 cars, ban suv's unless you own a farm or need to carry lots of stuff (kids not included in the def. of stuff) move all goods back on the rail, and bring back steam engines :)
I've just solved the world oil crisis - VOTE FOR LYNNE!
*sob* do you have any idea how hard it is to impress chicks when you've got a mouth full of corn silk dangling from your teeth? :((
or more appropriately :(≡(
I am curious where you pulled your "ears per acre" number from, as it is both inaccurate and irrelevant. Current USA corn production is in the 120-150 bushels of corn per acre range. This gives us 360-450 gallons of ethanol per acre, not the 14 gallons you are suggesting.
Your fundamental conclusion is, however, correct. We are not going to ever be able to grow enough corn to provide for energy independence. Corn is far too inefficient a crop — there are SIGNIFICANT energy and fertilizer requirements to produce this level of yields, and it is not cost-effective to do this without massive government subsidies that completely distort the true costs of production.
The only crop that has so far proven to be a cost effective biofuel is sugar cane. Unfortunately, sugar cane doesn't grow in the continental USA, and therefore lacks a powerful lobby in Washington like the corn farmers of Iowa have.
csfrequent: Sorry if the numbers are inaccurate. They come from the <University of Kentucky Corn and Soybean Science Group Newsletter (Sept 2005, Vol. 5 Issue 4.) as sited in the article. They specify several methods for determining projected yields (see section 2) that I figured was reasonably accurate for most growing areas of the US since it's in the mid-temperate zone of the USDA Plant Hardiness map.
That said, I Am Not A Farmer and thus lack actual knowledge of true yield per acre.
"700 ears per acre"
25000 ears per acre is more typical (your source material is right; you just read the wrong numbers). I could grow 700 ears of corn on my tiny bay area backyard.
While most biofuels are not currently economically viable (without subsidies), the become closer to viable every day as oil prices rise and as biofuel research improves the conversion process for cellulosic material.
Finally, did you know that California's gasoline mix is already more than 5% ethanol, and will be up to 10% by the end of next year?
Ok, I'm the first to admit my math sucks. So, at 25,000 ears per acre (at 600 kernels per ear and 90,000 kernels per bushel) we'd get 166 bushels per acre. Each bushel produces 3 gallons so it's 500 gallons per acre. 7 Million divided by 500 equals 14,000 acres per day * 365 days = 5,110,000 acres for biofuel production alone, or 0.01% of current croplands devoted to the production of fuel, or at 7984 square miles, an area a little less than the size of New Jersey.
Ok, so I was a little off.
Still, that's a fairly large chunk of production, assumes no crop loss and doesn't factor in things like growing costs.
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I didn't check your math, but biofuels in general suck for a different reason - net energy return on investment. Basically, how much energy you have to invest to get a barrel (equivalent) out.
The math is sometime fuzzy and certainly never precise, but it's pretty clear that ethanol is not strongly EROI positive, and should be avoided as a result. Never mind the other reasons. You know, like producing gases that people are uncomfortable with, and keeping farmers from producing feed corn that's used to make cows that are used to make burgers, etc.