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I’ve gone and designed an entire earth-like planet where life had never evolved. Oil can be reached if needed—the purpose of this question is to find how far they can go and avoid it. (Oil is generated the same way it is on earth— formed over 30km deep in the asthenosphere and pushed up through fissures in the plates, creating deposits within 200M of the surface in some areas).

Settlement: A human civilization has grown to just over 3 million population in 5 major enclosed cities.

No life, so no oxygen. The outside air is toxic and the land is sterile (but has same basic elements we have so it’s easy for microbes to fertilize)

Agriculture and foresting land is about 15 persons per acre, and this is their main oxygen supply besides geothermal powered chemical reactors.

They use a trivial amount of combustion due to the scarcity of oxygen. No combustion engines or jets, or even open flames generally.

The problem

My story needs to be set before petrochemicals and oil production, I don’t know when oil will become necessary (or if I’ve passed it already).

Research:

  • Before petroleum we relied on animal fat, pectin, leather, rubber, etc., which is fine until you are taking your food supply to make plastics and lubricants. It’s unsustainable after a point, you need your plants and animals for food and oxygen and fertilizing.
  • Because oil has been successfully created in a lab, this problem accepts current abiogenic oil generation theory. Some have opinions, but biogenic oil isn’t a consideration in this problem.

So the question is, how far can I go and avoid drilling for oil?

When will the population density consume hydrocarbon products faster than the artificial biome can supply?

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  • $\begingroup$ Before I start bashing my way through this problem, I must know: how do the humans, agriculture, ect. survive in this hypothetical, no-life, toxic planet? (assuming they are humans and I didn't miss something) $\endgroup$ Mar 1 at 4:33
  • $\begingroup$ I added “enclosed” to the cities. Forgot that detail, Thanks $\endgroup$
    – Vogon Poet
    Mar 1 at 5:02
  • $\begingroup$ If it never evolved life, where did the petroleum come from? Long chain hydrocarbons don't occur in extractable quantities naturally. Where did the people come from, for that matter? Alien colonists? What provision have they made for fuel when establishing the colony? If they have no combustion what are they using for energy? Why use combustion now, given that it is the lowest level of energy technology--it's what cavemen started with $\endgroup$
    – nzaman
    Mar 1 at 5:11
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    $\begingroup$ The vast overwhelming majority of hydrocarbons are used for burning. The amount of petroleum used in the chemical industry can relatively easily be replaced with vegetable oil with comparatively little effort. (The proportion of petroleum used as a feedstock for the chemical industry is about 2%. For comparison, in the EU and the US we use 10% ethanol in our gasoline, and almost all of it is of agricultural origin. The point being that we already produce more ethanol from agriculture than what petroleum we use as a feedstock for the chemical industry.) $\endgroup$
    – AlexP
    Mar 1 at 13:41
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    $\begingroup$ It's perfectly legitimate to stipulate that abiogenic petroleum is the primary source of hydrocarbons on your planet, but it is something of a controversial hypothesis here on Earth. I might suggest that you frame the question as "this is how it happened on the world I'm building" rather than "this is how it happened on my world, just like on Earth" to avoid your question being hijacked by that particular rabbit-hole. $\endgroup$ Mar 1 at 21:27

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In the situation you describe, it looks like oil will hardly ever be a viable alternative.

They have easy access to geothermal energy, while oil is 30 km underground (on Earth we barely managed to reach 12 km, and just for peeking, not for mining). It sounds like it will be way easier to find another geothermal spot and use it than to drill that deep. And if they need more raw materials, they can just build more locations where they can grow plants, and use them as starters for organic chemistry instead of oil.

Unless there is scarce carbon in general on the surface, but I am hardly capable of figuring out how they made to their present moment with that situation.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Mar 2 at 4:38
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Ensure colonists don't need hydrocarbons for energy.

Since they got there from some where else. They use nuclear(fusion and fission) energy almost exclusively for energy. The colony planers knew ensured the new colony would have sufficient energy for their first 100 years. This would be to maximize probability of success. This would mean that demand for hydrocarbons as fuel would be near minimum.

The colonists would extract hydrocarbons as chemistry feedstock as soon as it was economically feasible to do so, which will take some decades depending on deposit depth/size. If the deposits are deep enough they may never be economically viable.

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They will never need oil.

Any hydrocarbons can be synthesized entirely artificially, or in bioreactors.

You have water, and you have carbon, because you can grow plants. They may use plants to generate oxygen because it's convenient, and they get food as a byproduct, but they don't have to--if you just wanted oxygen, it would be more energy-efficient to produce oxygen directly by electrolysis, so as not to waste energy on all the other stuff that plants do to keep themselves alive. Similarly, you can get carbon and hydrogen as byproducts of water or CO2 electrolysis.

Most likely, however, you don't even need to go that far. If life never evolved, so there's no atmospheric oxygen, there is almost certainly atmospheric methane. That can be extracted from the air and dehydrogenated. If there somehow isn't atmospheric methane, you can just use agricultural waste; dump manure into and inedible plant waste into a bacterial digester with bacteria artificially selected to maximize methane and oil production, and you'll be set. You don't need and can't use petroleum for energy (since there's no atmospheric oxygen to burn it with), so all you need to replace is chemical feedstocks, and that takes a far lower volume of material, which your colony should have no trouble synthesizing indefinitely if they don't start out dependent on large quantities of oil and thus don't need to transition away from it.

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    $\begingroup$ If there’s petroleum in the ground then there’s automatically methane in the ground as well. Hmmm. Wish I had the energy cost of all this handy, sounds too good to be true $\endgroup$
    – Vogon Poet
    Mar 1 at 22:59
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    $\begingroup$ The premise of this answer is what I was going to say. (a) There are other chemicals that can go boom. (b) Oil serves two purposes: lubrication and energy to turn something. Water can turn something. So can wind and electricity. Lubrication can come from fats and then synthetics. It may delay some technologies, but hydrocarbon-based oil is hardly a necessity for technological development. +1 $\endgroup$
    – JBH
    Mar 2 at 1:56
  • $\begingroup$ @JoinJBHonCodidact I have to disagree. "Petrochemicals are chemicals derived from petroleum or natural gas. They are an essential part of the chemical industry as the demand for synthetic materials grows continually and plays a major part in today's economy and society. Petrochemicals are used to manufacture thousands of different products that people use daily, including plastics, medicines, cosmetics, furniture, appliances, electronics, solar power panels, 3d-printed organs, Gore Tex, styrofoams, and wind turbines." $\endgroup$
    – Vogon Poet
    Mar 2 at 6:02
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    $\begingroup$ @VogonPoet Real Life cannot be an overriding limitation on any question unless specifically requested. You just quoted something from Real life, where hydrocarbons existed. Of course they are an essential and major part of our society - but they can be circumvented in every case. Why don't we? Because, thanks to existing, they're an inexpensive solution to various problems - but not the only solution. $\endgroup$
    – JBH
    Mar 2 at 14:39
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    $\begingroup$ @VogonPoet Every scientist worth their salt would agree with me. There's a considerable difference between "it's cheap and easy to find here, so it became the defining premise of technology between 1930 and 2022" and "It's impossible to develop technology without it." And as I said in my previous comment, Real Life cannot be an overriding limitation on any question unless specifically requested. $\endgroup$
    – JBH
    Mar 3 at 1:50

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