So you want to use plants to reduce CO₂

I can think of plenty of excellent reasons the environment in the space station would lead to physiological issues. Sleep disturbance, stress, restrictions on diet and exercise, and the many severe effects of microgravity all come to mind. Again, you have to ignore humanity's extensive experience with other high-CO2 environments like submarines in order to believe that it's a significant factor compared to those other stressors.

> A definite global health concern is the increase in blood bicarbonate levels

It's hardy definite. It's another junk-science "study" out of Australia that took two epidemiological trends (bicarbonate level and mineral levels in blood over 20 years) and tried to interpret correlation as causation. You can use this kind of data-dredging to propose correlation between all kinds of unrelated trends. I'm seeing headlines blaming climate change for the obesity epidemic, for example, and you can be sure there's a junk science study behind every headline. In this case, I'm aware of no evidence from well-controlled studies (i.e., actual science) showing a causal chain from moderately elevated CO2 to physiological mineral deficiencies in real life. Again, we have lots of long-term data from high-CO2 environments like submarines. Show me some numbers.

> higher CO2 levels increase plant growth which impacts the plants mineral absorption, there are less naturally occurring micronutrients in our crops than there used to be just 20 years ago.

More questionable headline-generating studies. Yes, isolated increases in CO2 can cause carbohydrate dilution and subsequent changes in water usage and mineral uptake, but it also universally increases plant growth, and in many plants it increases production of other phytochemical nutrients. This is an extremely complex topic, and it's reductive to the point of absurdity to blame atmospheric CO2 for trends that are overwhelmingly influenced by soil depletion, water usage, and chemical fertilization.

Think about this logically: A substantial portion of our fruits and vegetables are grown in greenhouses. In the Netherlands-- the world's second-largest food exporter-- over one-fifth of produce is grown in greenhouses. Almost all modern greenhouses employ carbon dioxide enrichment, typically doubling the level of the atmosphere. If there's a brewing crisis of CO2-induced nutrient deficiency, don't you think the climate alarmists would be warning us about greenhouses? The fact that they aren't should tell you something.

It's common for people to filter on the latest fear-mongering headlines. Maybe these things are true, but "studies" like these that appear in corporate media headlines can't tell us one way or the other.

> I could not find references to concentrated CO2 treatments

It's a young field of research to be sure, but it took me about five seconds to find a bunch of recent papers. Here's the first result google gave me:

https://pmc.ncbi.nlm.nih.gov/articles/PMC11763298/ | Effects of Carbon Dioxide Therapy on Skin Wound Healing

> Carbon dioxide is bad for cognition.

is dubious and unsupported by science. As I point out downthread, we have extensive experience with very high-CO2 environments-- at levels regularly exceeding ten or twenty times current atmospheric levels-- and as yet little good evidence of uncompensated cognitive effects.

Beyond that, modern humans live much of our lives in moderately elevated CO2 with no apparent ill effect. Without deliberate ventilation, any enclosed space like a bedroom or classroom will rapidly achieve elevated CO2 levels, often into the thousand ppm range. Again, we have lots of data, and little of it points to a practical cognitive effect.

The US Navy maintain an informal goal to keep levels on board submarines to below 8000 ppm, loosely informed by what little evidence they have of its effects on crew performance. That's twenty times the current atmospheric levels. In practice, CO2 levels often go over 10,000 ppm, which apparently still doesn't cause them much concern.

You can leverage a sunny window for free.

I would have liked a more how many plants can do it, rather than the its impossible route.

AI says a snake plant and spider plant can produce oxygen night & day. Now assume I live in a tiny hovel (kinda true) how many plants do I need for "net oxygen surplus" (?)

Apparently, AI says, high yield crops of say wheat under intense LEDs or Spirulina make for optimal oxygen producers.

So 15 m^2 of spirulina in an aquaponics garden with intense led fixtures to supplement natural light might do it.

I'm open to the possibility that this is wrong, but as far as I can tell, the conventional scientific view is that high-CO2 environments are somewhat bad (although not catastrophic, even at 8000 ppm).