4 ms·

Actually not that much: The russian https://en.wikipedia.org/wiki/BIOS-3 https://en.wikipedia.org/wiki/BIOS-3 experiment tested this in the 70's, and found that

Actually not that much: The russian https://en.wikipedia.org/wiki/BIOS-3 https://en.wikipedia.org/wiki/BIOS-3 experiment tested this in the 70's, and found that given sufficient illumination, 17 litres of Chlorella Vulgaris algae are sufficient to provide oxygen for one person and scrub the exhaled CO_2 from the air. The talk about spacecraft life support systems linked below (https://media.ccc.de/v/rc3-158638-how_to_survive_in_spacecraft https://media.ccc.de/v/rc3-158638-how_to_survive_in_spacecra...) gives a thorough overview over the possibilities for plant-based oxygen generation.

Palomides 6y ago
I'm kinda skeptical about 17 liters but don't have the time to dig into the literature, so I'll just say that the number I gave is second-hand but seems well-founded of course there are lots of factors, especially with illumination/surface area
- nkingsy 6y ago
  Not sure of the math but I had about 17 liters of grow medium, 2w of air pumps, and 50w of leds 24/7 and was producing a shocking amount of biomass. Also, fresh spirulina is most comparable to tofu. Very little flavor, gag-worthy sponge-like texture. Was trying to make fish feed but had to eat most of it myself as the fish and the dog wouldn’t touch it. Shut down the operation after a few harvests. Mine was kept warm by sitting on top of a water reservoir that water cooled other grow lights for my main indoor garden, but keeping it warm would be the major cost in most climates, as it grows best in 90 deg F water.
  - dvh 6y ago
    Black soldier fly larvae (BSFL) are used to compost waste or convert the waste into animal feed. Fly larvae are among the most efficient animals at converting feed into biomass.
    - rripken 6y ago
      Are you suggesting that the parent should grow spirulina and feed that to BSFL and then feed the BSFL to the fish?
      - dvh 6y ago
        Yes, or to chicken
  - lazylizard 6y ago
    what fish?
  - labawi 6y ago
    At 8 MJ (2000 kcal) / day = 90W (average) diet, to scrub CO₂ you would need to bind about that much energy on average¹. Assuming optimistic 50% LED efficiency and 90% algae efficiency², you would need at least about 90W/50W / 0.5 / 0.9 = 4x as much production. So your setup could not scrub a typical person's CO₂. Nevertheless, fully optimized 17l of algae do seem believable, if well cared for. ¹ ignoring diet levels and differing CO₂ / H₂O ratio for fat vs. carbs etc. ² no idea how efficient algae are, but wikipedia says they are very efficient

Palomides 6y ago

I'm kinda skeptical about 17 liters but don't have the time to dig into the literature, so I'll just say that the number I gave is second-hand but seems well-founded of course there are lots of factors, especially with illumination/surface area

nkingsy 6y ago
Not sure of the math but I had about 17 liters of grow medium, 2w of air pumps, and 50w of leds 24/7 and was producing a shocking amount of biomass. Also, fresh spirulina is most comparable to tofu. Very little flavor, gag-worthy sponge-like texture. Was trying to make fish feed but had to eat most of it myself as the fish and the dog wouldn’t touch it. Shut down the operation after a few harvests. Mine was kept warm by sitting on top of a water reservoir that water cooled other grow lights for my main indoor garden, but keeping it warm would be the major cost in most climates, as it grows best in 90 deg F water.
- dvh 6y ago
  Black soldier fly larvae (BSFL) are used to compost waste or convert the waste into animal feed. Fly larvae are among the most efficient animals at converting feed into biomass.
  - rripken 6y ago
    Are you suggesting that the parent should grow spirulina and feed that to BSFL and then feed the BSFL to the fish?
    - dvh 6y ago
      Yes, or to chicken
- lazylizard 6y ago
  what fish?
- labawi 6y ago
  At 8 MJ (2000 kcal) / day = 90W (average) diet, to scrub CO₂ you would need to bind about that much energy on average¹. Assuming optimistic 50% LED efficiency and 90% algae efficiency², you would need at least about 90W/50W / 0.5 / 0.9 = 4x as much production. So your setup could not scrub a typical person's CO₂. Nevertheless, fully optimized 17l of algae do seem believable, if well cared for. ¹ ignoring diet levels and differing CO₂ / H₂O ratio for fat vs. carbs etc. ² no idea how efficient algae are, but wikipedia says they are very efficient