[nerdsniper]

To me (as someone who has worked on oil rigs, oil pipelines, oil refineries, and chemical plants), crude oil seems far more valuable as a material than as an energy source. It feels like a damned shame that we're still combusting so much of it for heat rather than reserving it for physical materials.

I understand the ways that economics are very important, and that the economics still currently favor burning a large fraction of the crude oil. But I also know that the right kinds of investments and a bit of luck can often change those economics, and that would be nice to see.

[whatever1]

We can always make polymers and HydroCarbons in general from other sources if we have energy abundance. We literally can just capture the CO2 we emitted from burning fossil and make it plastics.

Of course this does not make sense in a world where we do not have enough energy to even keep datacenters open.

Edit: To clarify, I do not propose burning fossils to capture CO2 and make plastics. I am a Thermo Laws believer.

[ok_computer]

Methane >> carbon dioxide as a polyethylene/linear polymers feed stock. Double bonded oxygens are hella higher affinity than four loose hydrogens. Also as pointed out, even in a concentrated combustion effluent stack CO2 is low concentration at atmospheric pressure.

I don’t know about methane as an aromatic/hybridized ring building block. Anything is possible with chemical synthesis but is it energy feasible.

There’s always plant hydrocarbon feed stocks but I think using arable land to make plastics is dumb and also carbon intensive. (I do wear cotton clothing tho because you need to make trade offs).

[whatever1]

Siemens has a collaboration with Porsche are piloting already eFuel production. Cost is super high (think like $10/liter). But thermodynamically feasible.

https://www.siemens-energy.com/global/en/home/press-releases...

[sonofhans]

That sounds like a hack from late-game Factorio: pollute enough that you can just pull iron filings right out of the air. Everyone wins! Except the meatbags who need to breathe the air …

[whatever1]

Assuming the damn rain does not throw your iron down to the ground before it reaches its destination. But then again you have rivers as a plan B.

[adrianN]

The problem with carbon capture from air is the low carbon concentration. Try to do the math for how much air you need to process to get even one barrel of oil worth of hydrocarbons from a DAC process.

[aethr]

The answer to this problem as it's currently being pursued is renewable carbon feedstocks. Growing things like canola on marginal land, harvesting it and turning it into biofuels and LCLFs (low carbon liquid fuels) using renewable solar/wind energy.

It's not a solved problem, though. Truly renewable carbon feedstocks have to source their carbon from the air, not the soil, which has to be continually measured. Land selection for carbon feedstock projects has to ensure it doesn't induce land-use change in other locations due to displacing other things like food production, etc. Otherwise the emissions and environmental harm from those downstream effects have to be included in the carbon positive/negative calculations for the project.

[pfdietz]

Remarkable amounts of carbon are available in waste streams, even if you exclude from the count plastics and other petrochemicals. Paper, cardboard, wood, natural fibers, carbon in sewage and waste food, and especially farm waste (parts of plants not otherwise consumed). Some of the latter is needed for soil conditioning, but most of that is from decay of roots, not stuff left at the surface.

All this can be extended by addition of hydrogen. Naively, if you process a carbohydrate into hydrocarbons, about half the carbon is lost as CO2. Adding hydrogen allows the oxygen to be carried off as water rather than CO2 (or, the CO2 to be converted to hydrocarbons and water in a second step.) Hydrogen currently comes from natural gas but that will have to change anyway, with the hydrogen being produced by (for example) electrolysis of water.

[marcosdumay]

There is way more carbon in the ground as rocks than as oil. If you have plenty of energy, the difference is quite manageable.

Besides, as somebody already pointed out, there is that CO2 on the air that we actually want to get rid of. It's nothing compared to the rocks, and a little harder to get, but getting it first would improve things a lot.

[ok_computer]

The carbon isn’t valuable elementally as much as it is structurally and molecularly. I mean that as aromatic rings and other ready made building blocks that conveniently can be fractionally separated with pressure and temperature conditions in a column as a gross generalization. All of this is energy intensive but much less so than building up from three atom molecules with strong bonds. And much much less energy intensive than separating a trace % molecule from the atmosphere at low atmospheric pressure and translating that to complex molecules.

There needs to be more appreciation for the laws of thermodynamics when discussing technology. Everything is not a 1-dimensional reduced abstraction.

[pfdietz]

The density of carbon in seawater is also higher much than it is in air. The relative concentration of bicarbonate in seawater is a few times lower than in air (as % by mass), but because water is nearly 1000x the density of air the true amount of bicarbonate there per volume is much higher.

[tesseract]

> there is that CO2 on the air that we actually want to get rid of

For this reason I have long been slightly baffled that development of compostable/biodegradable bio-based plastics is such a priority in materials research. Sure, it's interesting in the very long run, but for the foreseeable future, converting atmospheric CO2 (via plants as an initial step) into a long lived, inert material that can just be buried after an initial use seems like a benefit.

[sophacles]

Biodegradable is only one type of degradation. Some of those compounds break down over time, or with exposure to uv or random stuff in the ground, into nasty compounds that you certainly don't want entering the water cycle or food cycle. An additional attribute of biodegradable therefore is: keeps (non CO2 pollution down).

In addition, things that biodegrade don't immediately just turn into CO2. Things like biomass (that is everything alive and dead that isn't decomposed) use a lot of that carbon. A significant fraction of the carbon in rotting stuff doesn't end up in the atmosphere for decades or longer. The carbon cycle isn't just "CO2 becomes plants which become CO2"... there's a lot more steps in between (for example, next time you eat... you are a direct next step!). Some of those steps take a very, very long time.