Is there a signal-to-noise problem if you don't do hyperpolarization, and just give someone an isotopically enriched molecule
Yes.
17O seems like a good try for that
MRI with oxygen-17 has been done. Here's a study from 1990. And here's a more recent paper which mentions some reasons it hasn't been widely used, including:
You didn't include the most important common aspect of cancers: It's very common for cancer cells to disable mitochondria-mediated apoptosis mechanisms.
OK, in that case we can talk by DMs as well. Some LLMs tend to make formal and polite writing with somewhat awkward wording and can do a cursory web search to add more citations than you should expect someone to read, but maybe you're a student in a country that also speaks something besides english.
Current biochar carbon removal costs range from $130-180/t-CO₂ according to recent studies
You shouldn't just be looking at biochar; there are other approaches, like drying, adding CaCl2, etc. I've seen some lower estimates for biomass burial, eg $50/ton CO2 here. Burial where gas from decomposition won't escape is another option, eg this paper.
My general advice to you would be to trust cost estimates in papers less. Professors will effectively lie to make their research seem more useful, and there are bad techno-economic analysis papers too. Judging the quality of such papers and learning what parts are trustworthy is just a skill you have to practice.
First, I'd just like to check: was that response written by AI?
The cheapest sources of CO2 are from ammonia production and fermentation tanks. But if you mean removing CO2 from the air, biomass is definitely the cheapest option.
The simplest thing you can do is bury byproducts like sugarcane bagasse, and do something (there are a few options) to prevent decomposition.
The most economically attractive option on a large scale, in my opinion, is conversion to levulinic acid + furfural for chemical products and fuel, and burying the hydrochar. But...
As for good ways to reduce CO2 emissions in the first place, I think those include:
Consider this, we're proposing a moonshot here, not just an incremental product improvement.
If it's a moonshot, you should either: (1) be working on better chemistries in a university lab or (2) have some experience with manufacturing chemical products relevant to bringing manufacturing costs down or (3) be able to impress people with your understanding of industrial chemistry costs.
In 2022, Hemmatifar showed a stackable bipolar cell capturing at 400 ppm with electrical work of ~0.7 MWh/t while maintaining >90% efficiency[1]. They even ran it continuously for 100+ hours without fouling issues.
That citation also only shows release of CO2 at similarly dilute concentrations. A bigger difference between absorption and release concentrations obviously tends to require more energy.
poly(vinylanthraquinone) + carbon nanotube electrodes aren't particularly cheap.
When such devices have shown a good cycle life, that's in a lab with pure materials, not in open air with its dust and various organic compounds.
Recent TEA in ACS Energy & Fuels modeled a 200 kt/yr electro-swing system with wind power and projected $56-97/t.
That citation says:
The CapEx is estimated by assuming analogies: the regeneration cell of the AEC process is assumed to have the same relative CapEx as redox flow batteries, and the electrochemical cell of the ESA process is assumed to have the same relative CapEx as lithium-ion batteries.
That's...a non-analysis. Here's something easy to understand and more accurate than that: the CapEx of an electrochemical MOF thing is much higher than the CapEx of alkaline CO2 direct air capture. This is always going to be true. The stuff required is just more expensive than "sheets of something or other with liquid running over it". Even if the energy costs are zero, I can't see total costs being lower. I know about how much it costs to make such stuff, and it's just too expensive.
Basalt mineralization (specifically the Carbfix method) injects CO₂-water directly into porous basalt formations.
Ah, you're pressurizing the CO2 and drilling; I didn't bother reading that far before. That's certainly possible, though the basalt isn't specifically necessary for mineralization. Also, while you're focusing on fast mineralization, that's kind of irrelevant for underground injection.
It seems to me that, if we could get people to do that, then we wouldn't be in the current situation in the first place.