- The fossil fuels burned in a year represent about 400 years' worth of accumulated ancient biomass. That is, you'd need to capture all the biomass grown for four centuries to give the fuel we consume in one year.
- But conversion and preservation aren't perfect. So it took five million years to form just the oil we consume annually (or did in 1997, though values have remained reasonably constant since). That is, only about 0.008% of ancient biomass was stored as petroleum.
I don't know the figures for carbon-cycle sequester and release rates, though at best we're looking at centuries to remove what we've put into the atmosphere in decades, if not longer.
I would also point out that today it is not possible to form new large scale coal/oil deposits.
Coal/oil deposits that we are using up now formed because at the time there was no bacteria that could digest dead plant/plankton matter.
This is also why all coal/oil deposits are very old. There is very little deposits after bacteria has evolved.
Nowadays there needs to be special circumstances for a piece of biological matter to not be digested by bacteria. For example it would have to be covered by permafrost or drown in oxygen-deficient lake for a very, very long time and then covered by soil.
So at least once we send ourselves extinct through fossil-fuel driven climate change, any intelligent life that comes after us won't have the resources to do the same.
I think energy is least of problems. At the beginning forests provide a lot of energy and would be enough to bridge to industrial times (at least for us).
The real issue, I think, is lack of easily available raw materials like iron, tin, copper, etc. We have depended A LOT on iron practically lying on the ground.
Without having some iron easily available any startup civilization wouldn't know to look deeper and even if they wanted, they would not have any tools to do so.
At least with energy there is multiple ways to acquire it.
On the other hand there’s a lot of already processed and extracted iron and steel we’ve conveniently dug up and left around for future societies to maybe harvest.
Most of it is exposed to weather - which means it'll oxidize and decay to uselessness rather quickly, and eventually dissolve and become diluted. With ores, we had it all in convenient form.
A lot of it yeah but large thick things like bridges will probably survive for quite a while in usable sized chunks. Copper too will be pretty available and protected in wires. It really depends on what timescale we're talking about though in the end. If we talking about humans rebooting there could still be usable bits around depending on how long it takes to begin rebuilding. If we're talking about a whole new intelligent species I agree they'll have vanishingly little to work with.
"Ore genesis" is the term of art in geology for how various mineral ores form. Typically this involves a source, transport, and trap. Biological processes can play a major role (iron, limestone).
Useful ore deposits tend to be vast, with absoutely immense amounts (many trillions tons) of paydirt. The value of ores are that the minerals of interest are concentrated, sometimes to very high levels (50% or more of total material), though increasingly lower-grade ores (1% concentration or lower) are utilised. This means that you've got to move 99 units of mass for every unit of primary mineral extracted (overburden).
Even very large human formations are small by geological standards. The World Trade Centre towers contained about 200,000 tonnes of steel. That's a lot for humans, but a minuscule amount on a geological scale. (https://hypertextbook.com/facts/2004/EricChen.shtml)
Current iron ore extraction is on the order of about 2.5 billion tons/year. That's roughly 1/3 ton per person on Earth.
I think it still works out to a net difficulty increase to any group trying to restart an industrialized civilization because of how much easy energy reserves have been permanently extracted. There’s basically no surface level coal/oil/gas that could be tapped into and finding the remaining reserves from scratch might be prohibitively difficult.
Then there’s the question of how much of the steel will still be usable when it’s time to extract it. That’s a variable problem depending on how long the ‘dark age’ is before people are rebuilding I suppose. It could be like Doctorow’s Walkaway where there’s abundant enough discarded resources you can almost achieve post-scarcity (but that world never wen through a hard crash it was more building a parallel society than a whole new one). Or it could be centuries later when a lot of the steel will be rust. Hard to say.
Without the easy energy source to bootstrap their tech, they may not get anywhere near having to consider that problem. They might not even make it to figuring out steel.
Is it possible for intelligent alien life to arise on a world without any oil/gas/coal reserves (maybe they don’t have the equivalent of plankton, or maybe they do, but bacteria that could eat the plankton evolved much earlier)? If so, would they be forever trapped on their planet, never able to go through an Industrial Age and eventually achieve rocket flight? Maybe this is one explanation for why no aliens, so far.
CO2 is mostly sequestered by reaction to form carbonates, not by reduction to biomass, but yes it will take a long time. In the intermediate it will dissolve into the deep ocean (mostly), but even that takes a while.
This reaction can also be accelerated by crushing basalts and other readily-available rocks to a fine sand/dust, and exposing that to the open air by spreading it over large areas of ground, such as fields or beaches. The process is not cheaper than other kinds of carbon sequestration, but it's definitely comparable and long-term sequestration of the carbon seems especially likely, since we're simply enhancing the existing geological carbon cycle.
Peridotites, in particular, with lots of olivine. Olivine weathers particularly quickly because its silicon atoms are in SiO4(4-) tetrahedra that are not covalently linked to each other (a "nesosilicate").
A problem with just spreading this out on beaches and the like is that these rocks are also often enriched in nickel vs. the average crustal rock, and this would release many millions of tonnes of nickel into the environment. There is some evidence that nickel release was part of the terrible events at the Permian-Triassic extinction. Nickel is crucial to the enzymes in the metabolic pathways leading to the production of methane in anaerobic environments. There's an idea that nickel injection into the oceans by fallout from the PT megaeruption in Siberia led to massive methane production.
This is (mostly) a non-sequitur to any modern discussion about climate, the atmosphere, and its effects on human life and civilization.
Life, at this point is used to a particular equilibrium. Sure, life has existed at different equilibriums. But we also know when those equilibriums are massively disturbed (via a great oxygenation event, massive asteroid, major volcanic eruptions, etc.) much of the life dies out (obviously depends on the intensity of the disruption) and it takes many years for life to adjust to and make a new equilibrium.
Humanity should be deeply concerned with how deeply we have disrupted the equilibrium, as this disrupts the world and biosphere that sustains us.
It might be useful if you're building an argument that humanity will be better off after the current mass extinction event is over. However, I tend to find this point more often leads to a George Carlin-esque cynicism and nihilism about earth being better off without humans (or human civilization) anyways.
I guess you don't understand what "sequestering" means.
Sequestering is a process where carbon becomes unavailable for biological processes.
So you have carbon circulating (present in biomass, returned to atmosphere, then back to biomass, etc.) and you have carbon that is not available for circulation.
Carbon in atmosphere is part of circulation. When a supervolcano erupts and emits a bunch of CO2, this adds carbon to atmosphere but then that carbon may very quickly be bound in biomass (for example algae, forests, etc.) This doesn't mean it is sequestered. The algae can die and ferment and forests can burn, releasing CO2 back to atmosphere.
Earth has ability to very quickly bind large amounts of CO2 from atmosphere, true.
But it does not have ability to sequester it, because as long as the carbon is present in biomass, that biomass can burn or rot and change to methane/CO2.
Current coal, oil and gas deposits are due to the fact that at early stages of evolution there was no bacteria that could process some parts of biomass. For example, plants rather than rot would just be covered with more plants and become coal deposits.
Today, it is not possible to form new coal or oil deposits, because any biomass would be quickly digested/fermented/rotted before it could be sequestered.
The pre-bacteria theory is pretty shaky fyi. There is evidence for relevant biomass-degrading bacteria being ubiquitous at the times of coal/oil formation. A more plausible theory imo is that geological conditions in the paleozoec/mesozoeic era lent themselves to greater fossil fuel formation - greater tectonic activity alone would produce the flooding and interment processes necessary to push significant volumes of biomass down to fuel the process.
So why can't peat deposits turn into coal under the right conditions? Those form all the time under certain conditions, but they can sequester a fair amount of biomass.
There's a fairly large amount of biomass that does get sequestered. Bogs, swamps, and tundra are particularly prone to this, and peat is effectively a low-grade coal (it played a major role in the development of Holland as well).
There is a huge amount of sequestered carbon in such landforms. I don't know how that compares with primordial carbon formations.
One factor that seems to have been significant in the formation of the coal belt that runs from the present-day Czech republic through Germany, France, northern Spain, England, and the Apallachians is that this was a region of forest and/or swampland adjacent to mountains (the Appalachians, which are literally older than dirt), with the swamps sinking rapidly into a shallow seabed. That may also have played a major role in depriving the biomass of oxygen which would permit it to rot.
My own rampant speculation: even given decomposers capable of breaking down woody plant tissue, it's possible that these were insufficiently numerous, or inefficient, or otherwise limited, in ways that aren't currently relevant, such that decomposition is more efficient and rapid today.
Interesting questions. Unlikely to be answered by any of us here soon.
