So you want to use plants to reduce indoor CO₂
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Core Problem and Baseline Chemistry:
- Elevated indoor CO₂ impairs cognitive function; humans produce ~1 kg of CO₂ per day (~1 mole per hour).
- Photosynthesis converts 6 H₂O + 6 CO₂ + energy into 1 glucose + 6 O₂, requiring a theoretical minimum of ~477 kJ per mole of CO₂.
- A 100% efficient "magical" plant system would require a continuous power draw of at least 132.5 W per person.
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Physical and Biological Efficiency Losses:
- Real photosynthetic processes require 8 photons per molecule of CO₂; using optimal pure red light (~680 nm / 1.8 eV) raises the minimum physical chloroplast power requirement to 386 W.
- Accounting for ~30% photon reflection/transmission losses bumps the requirement to 551 W.
- Plants consume roughly 40% of their generated glucose for basic cellular respiration to stay alive (re-releasing CO₂), pushing the net requirement to 918 W of pure radiant red light.
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Practical and Engineering Realities:
- Translating 918 W of radiant light via standard LED grow lights (~50% electrical efficiency) requires ~1,836 W of continuous electrical power under ideal monochromatic red light.
- Using visible white light and accounting for light scattering across a real room pushes real-world power consumption to 5,000–10,000 W.
- Most of this energy dissipates into the room as heat, equivalent to running multiple space heaters continuously.
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Takeaways:
- Houseplants cannot meaningfully reduce human-generated CO₂ levels in standard residential conditions.
- To offset one human's respiration with plants, you would essentially need an intensely lit, high-biomass industrial vertical farm inside your room.
- The only practical and effective solution to lower indoor CO₂ levels is proper ventilation (e.g., opening a window or using mechanical HVAC).