Let’s assume we wish to consume petroleum in a sustainable way. That is, we wish to consume oil at the same historical rate that it is generated by the planet. In this scenario, what’s your fair daily ration of petroleum? Several barrels per day? A few tens of gallons? Let’s find out, and let’s be extremely lavish and generous in our estimation.

Earth’s total endowment of petroleum is estimated to be equivalent to 7 trillion barrels of oil. This includes both conventional forms (crude oil) and unconventional forms (tar sands, oil shale, etc.). Just for fun, let’s imagine that this estimate is a factor of 1000 too low and that the real endowment is 7 quadrillion barrels. That is, we are claiming that there are 20,000 yet-to-be-discovered Saudi Arabias somewhere on the planet. Wow. That’s a lot. That’s about 200 undiscovered Saudi Arabias per country. Where might these resources be hiding? Anyway…

Let’s further assume that these 7 quadrillion barrels of oil were formed over the 600 million years that life has existed on Earth. Check that. We said we were going to be lavish. Let’s say that the 7 quadrillion barrels formed in just the past 100 million years. Thus, the rate of generation of petroleum under our assumptions is (7 × 10^{15} barrels) ÷ (1 × 10^{8} years) = 7 × 10^{7} barrels per year.

There are about 7 × 10^{9} people on Earth, so each individual’s yearly share of this sustainable flow would be (7 × 10^{7} barrels/year) ÷ (7 × 10^{9} persons) = 0.01 barrels per year per person. Each barrel is about 55 gallons or about 7000 fluid ounces, so your yearly petroleum ration is (0.01 barrels/person/year) × (7000 ounces/barrel) = 70 ounces per person per year. There are about 350 days in a year, so your daily ration of petroleum is (70 oz/person/year) × (1 year/ 350 days) = 0.2 oz/day. **Thus – in spite of our ridiculously generous assumptions – we conclude that the sustainable ration of petroleum is only about one teaspoon of petroleum per day per person.**

Are you currently consuming one teaspoon per day? Me either. Hell, I blow through my entire *annual* budget of 1/2 gallon/year each time I mow my back yard. There’s simply no way we can continue to each consume several gallons per day. The stuff *must* run out.

Keep in mind that these estimates were made in an extremely generous fashion. Your daily sustainable petroleum budget is a teaspoon, and that’s assuming there are 200 undiscovered Saudi Arabias in your country. Your real budget is probably hundreds or even thousands of times less than a teaspoon per day. Given the fact that we are consuming petroleum at a rate millions of times faster than it is being formed, and given the fact that * there is simply no practical substitute for a barrel of oil*, Humanity’s predicament is dire.

**Note to the Abiotic Oil Proponents:** Before you pounce, think about it. Is the *mechanism* of oil formation really relevant to the above estimate? In order to sustain a consumption rate of just 1 teaspoon per person per day – and assuming that all the oil formed in just 100 million years, or just 1/40^{th} the age of the Earth – we would need a *minimum* of 200 undiscovered Saudi Arabias per country, regardless of *how* oil is generated. If oil formed over a longer period then 100 million years, then the required reserves get even larger. Where are these vast reserves? If the answer is “50 miles underground”, the answer might as well be “on Titan”.