Trees respire. They breath in and out. At night time, many trees emit more CO2.

And trees don't exist in isolation as these napkin calculation articles consider them (spherical cows and all that). Every single tree on earth relies on mycorrhizal fungi for the vast majority of its nutrients. Fungi break things down release CO2.

Most of our oxygen comes not from forest but from oceans (specifically from phytoplankton, algae, and photosynthetic bacteria). Between 50-80% of it in fact. Likewise, most of the CO2 that has been captured has been captured by the ocean not by forests. About 25-30% of all human emissions have been captured by the ocean.

Forests (and grasslands) are tremendously important for ecosystems and our health but I think this focus on CO2 and oxygen is simply misleading. If that's your concern you should really be focusing on the ocean. Which IMO is in an even more dire strait than our forests

The BBC did this in their 2012 documentary mini-series "How to Grow a Planet" with Iain Stewart. It was a lovely series; I highly recommend it.

What if the plants were algae?

I don't really understand this. First of all, you can just weigh the plant, and tell how much CO2 it has captured, right?

Second of all, what does it matter how much CO2 I produce? What's harmful is the additional CO2 that goes into the atmosphere for burning fossil fuels. All other CO2 is just in the same cycle that's been happening for ever.

EDIT: My child comment is dead and vouching doesn't resurrect it, but now the post makes sense, thanks for the clarification.

Bamboo it is.

How is it that 132.5 watts is 3 light bulbs but 918 watts is 765 light bulbs? Is there a typo?

That one final number is all one needs as a reply for "but they help a little".

> Real plants do photosynthesis through a physical process

(nit) it is more accurate to call this a biological process, or chemical process

Saying "physical process" makes me think of inclined planes, free-body diagrams, and EM fields.

no, we are useing solar PV to eliminate the excess carbon bieng added to the atmosphere, and plants, rocks, and many other natural processes will return CO² levels to a more moderate level.

This seems trivial: if you could add enough plants to your room to reduce CO2, we could easily do the same thing at planet-scale and global warming wouldn't be an issue.

Sadly I am a bit hopeless about climate change. Even if every person on earth dropped everything and started making biochar to be buried it would not sequester enough carbon to make a difference.