philaphonic wrote:Running through some publicly available stats, I thought I was going to come up with some zinger of a condemnation against the refinery industry, in the sense of energy used to refine a gallon of gas. But unless I got some basic math wrong, it looks pretty efficient. Feel free to verify:
In 2005, US refineries processed 6,250,625,000 barrels of crude oil, and 48% of the output was gasoline (1). They used 48,891,000,000 kWh of electricity to do so (2), resulting in 89.4 Wh electricity consumed for every gallon of refined gasoline produced.
48891000000 / 6250625000 = 7.822 kWh/bbl crude oil
42 gallons/bbl -> 7.822/42 = 186 Wh/gal crude oil
186 * 48% = 89.4 Wh/gallon refined gasoline
In the last step you should divide by 48% instead of multiply, giving you 388 Wh/gallon. Others have made excellent points also about further consumption of energy in delivery, storage, etc. Also consumption of natural gas is no small matter. And don't forget all the potable water that is consumed, which is at least as important if not more so than the energy consumed. And we're leaving out the energy cost of getting the oil out of the ground and delivered to the refinery, which is probably higher than refining and transporting the gasoline.
I'm still looking for the source, but I've seen estimates around 8 kwh consumed per gallon of gasoline produced. If that's true that means a Leaf would go further on the energy to produce a gallon of gas than the average gas car would burning it.
EDIT: Admittedly a biased webpage, but Darell from evnut.com came up with over 12 kwh / gallon. He also pointed out that Nissan has advertised 7.5 kwh / gallon in their Leaf marketing: http://evnut.com/gasoline_oil.htm
EDIT 2: Still trying to figure out why your result is so low. I think your approach to getting the total barrels processed is an overestimate. It seems you took the 17,125,000 barrels/day CAPACITY from the NPRA source and multiplied that by 365 to get your 6,250,625,000 figure. I really doubt that 100% of U.S. refineries are running at 100% capacity 100% of the time, while the electricity consumption figures are what was actually used, not what they would consume at capacity.
EDIT 3: I found a figure of 2,225,344,000 barrels of gasoline PRODUCED by U.S. refineries in 2005 (link
), so that brings your result up by almost a factor of 3. Getting closer.
EDIT 4: Your source for the 49 billion kwh figure doesn't seem too reliable, so going back to eia.gov I found this
. Unfortunately that's for '98 so it's probably an underestimate. These numbers are also useful because they give total energy consumption, not just grid electricity (which I assume the 49 billion kwh is, although specifics aren't given on that page.) So for '98 we have 7,130 trillion BTUs consumed by petroleum refineries, or a little over 2 trillion kwh. We could use the 48% number to say only half of that goes directly to gasoline production, but that's still 20 times larger than the 49 billion kwh figure you found. And I'm sure the 2005 numbers are even higher!