are fossils really nonrenewable?
If you mean "are the fossil fuels we use today essentially non-renewable" then the answer is yes.
The term "renewable" means the reasonable ability to be replenished.
For example, lumber, used both in construction and fuel source, is considered renewable given the relatively short amount of time needed to grow new trees.
And that "amount of time" is the key. A person would be quite right to point out that new fossil fuels are being made all the time. After all, the process of fossilization did not stop when petroleum drilling started. However, every time you drive your car for one hour, you burn up many years worth (poss. thousands of years worth?) of stored photosynthetic energy. So the ratio of [rate of comnsumtion] to [rate of replenishment] (rC=rRx) renders the resource "nonrenewable".
Questions about how much oil is left and how it should be used are a mix of politics and physics.
For example, our estimates of how much oil is left have been steadily increasing. Some say that's because we've developed better models for estimating the size of reserves; others accuse countries of inflating their numbers so that they'll be allowed to export more oil.
It also means that many of the numbers I googled for the purposes of this *rough* estimate are open for debate, opposition, refute. I don't trust anybody's numbers on this subject, not without a lot of study.
I averaged a few guesses to come up with one trillion barrels of oil left in the world. From another site, I found out we're using oil at a rate of 130,000 barrels per minute (yes, minute), and that this rate has been fairly constant for the past twenty years.
So let's say we our consumption rate was a quarter of what it is now for twenty years before that, and a twentieth of what it is now for forty years before that (for a very crude model of an exponential curve). That means we've burned 2 trillion barrels of oil so far.
So it took the earth 4.5 billion years to make 3 trillion barrels of oil; that means that the earth produces about 700 barrels of oil every year.
As long as we use less than 700 barrels of oil every year, we'll never run out of oil.
One barrel of oil can be refined to make 20 gallons of gasoline; one gallon of gas can be used to move a reasonably efficient car 40 miles on a flat surface.
So we won't use up the world's oil by driving our fuel-efficient cars 10,000 miles a year...
...as long as there are only 56 cars on the planet.
The amount of oil used in driving a car for one hour works out to be very close to the amount of oil produced in an hour by the earth. (My ballpark figures gave me one and half hours for the replinishing time.) But the cost of driving half a billion autos for an hour...
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