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British energy company Octopus Energy claims on their blog:

If we keep burning fossil fuels at our current rate, it is generally estimated that all our fossil fuels will be depleted by 2060.

This doesn't seem very far away. Is this true?

2
49

No

First, this figure is for petroleum. For coal, the figure is much larger. Some of the figures I found for coal were 133 years, "anywhere from 68 years to a hundreds of years", and 357 years (in that last one, "we" may be referring to just the US).
Second, this number is for proven oil reserves. Proven oil reserves is oil that is
(1) known
and can be extracted
(2) at current market prices
(3) with current technology.

More deposits being found, oil prices increasing, and better extraction technology can all increase the amount of proven oil reserves.

According to Forbes, only about a third of oil is extracted. This would give another century in current oil reserves, plus all the oil left over from past reservoirs:

And beyond just crude oil, which is about 83% of total supply, there is a rapidly expanding stockpile of biofuels, natural gas liquids, synthetic fuels, and other sources that will continue to broaden the availability of liquid fuels. Additionally, ~66% of the oil in a reservoir is frequently left behind because it's too expensive or difficult to extract.

Some of this is not practical to recover for any reasonable price. Just how much is "left" is much fuzzier than it might seem at first glance, but it's certainly more than the forty years that Octopus Energy claims.

19
  • 3
    When renewables become cheaper than oil (despite oil burners not paying external costs), burning oil will become unprofitable and will eventually cease in any case. Not sure where that fits in with your three criteria.
    – gerrit
    Sep 22 at 7:24
  • 12
    @gerrit: Cheap green energy would effectively lower the market price of oil. With most consumers able to switch away from oil, the ones remaining (that need it for its chemical properties, e.g. to make plastic, not just as a fuel) could have their much smaller demand supplied from only the cheapest-to-extract oil reserves. And if oil isn't competing against other things as a fuel, demand for oil specifically may be less elastic. (i.e. even if it's cheap, customers won't want a lot more, unless it gets even cheaper than green energy.) At least that's my Econ 101 analysis, I'm no expert. Sep 22 at 8:07
  • 4
    For a real life example of how the definition of "oil reserves" is a moving target, remember the fracking boom of the past decade. Suddenly many more oil wells were available for economic extraction, and that was reflected by the drastic drop in gasoline prices.
    – Thegs
    Sep 22 at 14:46
  • 3
    @Dave but it might be more reflective of contextual realities to say "at the current rate, I'll run out of this cereal by the end of the week."
    – nitsua60
    Sep 22 at 15:08
  • 3
    @PeterCordes Yeah it would - you mostly need the aromatics from oil, and a lot of them get burnt up in the light fuels now. You can also make them from natural gas (but it takes a lot more energy than refining them out of oil).
    – CJR
    Sep 22 at 21:02
15

For oil, using proven reserves and current oil production, the date is more like 2067. World proven reserves are approximately 1.7 trillion barrels, or 1.7 million-million barrels (EIA figures]). Current rate of production is about 100 million barrels/day, (EIA figures). The 100mb/d rate will eat through the 1.8 trillion barrel reserves in about 47 years.

For natural gas it is about 2073; again using EIA numbers for reserves (7,300 trillion cf) and production (140 trillion cf/year).

For coal the IEA numbers yield an estimate of 2150 (reserves: 1.16 million-million short tons, production: 8,800 million short tons/year); again using the current production vs. known reserves benchmark.

The oil specific quote from the linked article states:

Different fossil fuels have different depletion dates. In 2018, the demand for oil rose by 1.3% - which is almost double the average annual rate seen over the 10 years prior. With demand predominately driven by the transport sector, our oil reserves are running out faster than our other fossil fuels. In fact, if we don’t find any additional oil reserves, it’s estimated that our known oil deposits will be gone by 2052.

Similar language is used to describe their assumptions for the other fossil fuels. Thus, the figures above are an apples-to-apples comparison with the assumptions used in the article.

Also note this overall disclaimer in the article:

The answer isn’t exactly straightforward. Different sources have given different estimates, with no universally agreed timeframe. There are lots of different factors that need to be taken into account, such as which fossil fuel we’re looking at, our current and future usage levels, and whether we discover any more reserves.

4
  • So is your answer "pretty close for oil and gas, but way off for coal?"
    – LShaver
    Sep 22 at 13:24
  • @LShaver In my view, the numbers speak for themselves; there seems to be significant discrepancies between what the article claims and what you get applying the same methodology using IEA numbers.
    – Dave
    Sep 22 at 14:06
  • 1
    @Dave I tend to agree, but this answer would benefit from a direct, clear response to the question.
    – LShaver
    Sep 22 at 22:03
  • Comments are not for extended discussion; this conversation has been moved to chat.
    – fredsbend
    Sep 29 at 18:54
7

On current trends, we won't run out of fossil fuels, even oil or gas.

This is a slightly misleading statement because the question asks about the current burn rate, and this answer rephrases to "current trends", which requires justification. It's a demand side argument; "current burn rate" ignores that demand is (or soon will be) a fast moving target.

Rather than justify the argument (which was deprecated here as "original research" and then "common sense or pure logic") just refer to a recent study from Oxford University illustrating the current trend in energy prices and how the economics make it unlikely that the current burn rate will be maintained

Basic economics must dictate the trend from there : oil is fundamentally a depreciating asset, and any oil company executives must, deep down, be painfully aware of that fact. (Notably, in recent years the Saudi royal family floated Aramco, i.e. partially divested themselves from it : note though that attributing this to future depreciation is my speculation)

EDIT : Since the original answer, Nature has published an article discussing this reframing of the question

0
5

While reading the other answers, you might get the impression that fossil fuel availability won't be a problem for 100 years.

Unextractable oil, fossil methane gas and coal reserves are estimated as the percentage of the 2018 reserve base that is not extracted to achieve a 50% probability of keeping the global temperature increase to 1.5 °C. We estimate this to be 58% for oil, 59% for fossil methane gas and 89% for coal in 2050. This means that very high shares of reserves considered economic today would not be extracted under a global 1.5 °C target.

  • The energy return on investment for oil and gas is decreasing. It was about 100:1 in the early days (meaning that 1% or less of the energy contained in a barrel of oil had to be expended to deliver that barrel of oil), it is about 20:1 for conventional oil, while the EROI of tar sands and oil shale are about 5:1 and 3:1, respectively. If the ratio is too close to 1:1, the source provides no net energy anymore. That specific form of energy can be convenient (e.g. batteries, hydrogen, ...) but it needs to be converted first, from a primary energy with an EROI clearly above 1. Peak oil and the low-carbon energy transition: A net-energy perspective

It means that:

  • we don't have enough fossil fuels to power our economy indefinitely
  • we have more than enough to completely destroy our climate. In this sense, we should not care much when we would run out of fossil fuels with our current consumption. This consumption should be drastically reduced anyway.

We will have to switch someday, and the sooner the better. Business as usual for over 50 years (see "Reserves-to-production ratio" in "BP statistical review of world energy"), with 84% of our energy coming from fossil fuels, would render some of the world’s most densely populated areas inhabitable.

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    Consider that a battery has a ratio below 1:1 (it requires more energy to create than what you can get by using it). It may be going too far to say that it would not make sense to extract; rather, it will be limited to scenarios where efficiency is not the overriding factor.
    – JBentley
    Sep 23 at 9:02
  • I'm missing where this is answering the asked question. It's interesting side info, but it needs to be accompanied by an actual answer to the question.
    – fredsbend
    Sep 24 at 0:28
  • @fredsbend: Thanks for the feedback. I've added sources, including a BP one directly answering the question. Sep 24 at 8:19
  • Thank you for the updates, but I'm afraid it still doesn't answer the question: when would we run out if we kept the current usage rate? Rather, you are answering whether we should use it all up in the first place. I just deleted another answer saying basically the same thing, but less developed. You need to answer the asked question or I will have to delete the post.
    – fredsbend
    Sep 29 at 19:00
  • @fredsbend: Thanks for the detailed comment. I've added a mention and a direct link to the "Reserves-to-production" ratio, which, AFAICT, is a direct answer to "when would we run out if we kept the current usage rate"? I trust BP to deliver reliable data about oil reserves. Is there anything else I should add? Sep 29 at 19:28

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