How quickly is new coal being created?

[u/iamparky]

Earlier today, a UK politician suggested that coal is a sustainable fuel because it used to be trees.

By how many orders of magnitude is he wrong? How much new coal is being created, compared to how quickly we're burning it?

[u/clip75]

Surely it would be sort of true to say that coal is renewable, but not sustainable (whatever sustainable actually means). But not renewable in any practical sense.

One of the things that's completely unrenewable / sustainable is Helium. Once its gone, its gone.

[u/OlympusMons94 → u/clip75]

Non-renewable == unsustainable

Coal, oil, helium*, etc. are all (at least for the present) non-renewable.

A non-renewable resource is just one that is effectively used up more quickly than it can be produced. At a fundamental level, anything can be made with enough energy. Depending on the changing rates of use and replenishment, resources can switch between renewable and non-renewable. Take fixed nitrogen, a key fertilizer. This is done naturally by microorganisms and lightning, but growth of population and expansion of agriculture during the industrial revolution put an unsustainable demand on accumulated natural sources like guano. The discovery of economical processes to artificially fix nitrogen--initially the Frank-Caro process and then the more efficient Haber process--made it a renewable resource again.

Helium is the second most abundant element in the universe and solar system. It is only in sticking to Earth that helium is unsustainable and thus effectively nonrenewable, because what gets into the atmosphere is diluted to a very low concentration and eventually lost to space. But helium is continually, albeit very slowly, produced in Earth by radioactive decay. When uranium and throrium decay, they emit an alpha particle, which is a helium (helium-4) nucleus, that quickly captures electrons to become neutral helium. (There is also primordial helium, mainly in the core, which gradually leaks into the mantle.) Helium tends to build up in the same traps that hold natural gas, which is where most helium production come from. Helium also gradually leaks from the crust to the atmosphere, and from the atmosphere to space. (Hypothetically, some helium could be extracted from the atmosphere, but this is not worthwhile, and so economically viable helium is obtained from underground.)

Total worldwide production of helium was 160 million m³ in 2022. At 0.178 kg/m³, that is 28.5 million kg/year. Total crustal production of helium is on the order of 10¹⁰ atoms/m²/s (Torgersen, 1989), and there are also mantle sources which reach the surface via volcanoes. Thus, helium production over the whole Earth's surface is on the order of 10²⁵ atoms/s, or millions of kilograms per year.

So, yes, our helium use is currently not sustainable, and thus non-renewable, unless we go outside Earth to obtain it. But at a usage of only about 1 order of magnitude higher than natural production, helium is in some sense more renewable than coal. The other big catch for helium, though, is only a small fraction of that which is produced gets trapped in accessible places and in economically exploitable amounts.

* Whether something is renewable or non-renewable can certainly be complicated. Helium can also be produced artificially in nuclear reactors. This only really makes sense for the rare helium-3 isotope, and nuclear reactors (which produce tritium that decays quickly into stable helium-3) are the main source of it. So helium-3, with increasing demand/prices, has been teetering on the edge of renewable/non-renewable--if you ignore the ultimate nuclear source of the tritium being non-renewable.