Spirulina Algae Photobioreactor (2017) | Hacker News Reader

Spirulina Algae Photobioreactor (2017)

mikechatzidakis.com

66 pointsseesawtron19 comments

This was just mentioned in this talk about spacecraft life support systems: https://news.ycombinator.com/item?id=25590724

I suppose you got it from there as well?

It's surprising how simple a setup this turns out to be, for creating a working bioreactor that produces oxygen.

Also interesting on the spacecraft angle: Apparently spirulina will grow in dilute urine as a growth medium: "Attempts were made to culture Spirulina platensis in human urine directly to achieve biomass production and O2 evolution, for potential application to nutrient regeneration and air revitalization in life support system. The culture results showed that Spirulina platensis grows successfully in diluted human urine, and yields maximal biomass at urine dilution ratios of 140~240" https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1361757/

There are a lot of purported uses[1] for algae. The OP talks about oxygen generation[2] and food[3]. I've personally been really interested in cultivating algae as a source of carbon neutral jet fuel[4], specifically for personal energy independence. And, finally as fertilizer[5]. I haven't had time to do any experimentation yet but I'm excited to see that a DIY approach is so accessible.

[1] https://en.wikipedia.org/wiki/Algae#Uses [2] https://scholarlycommons.obu.edu/scholars_day_conference/202... [3] https://en.wikipedia.org/wiki/Spirulina_(dietary_supplement) [4] https://en.wikipedia.org/wiki/Algae_fuel [5] https://en.wikipedia.org/wiki/Seaweed_fertiliser

I remember a great article in Make Magazine that described growing Spirulina. I believe it was this article by Dr. Aaron Wolf Baum:

http://www.algaelab.org/2011/05/09/algaelab-diy-spirulina-ar...

A recent post (11/20/2020) on that blog announces that Dr Baum has started GreenSpring Farms in Brentwood,CA and is selling fresh Spirulina.

https://www.freshspirulina.com/our-spirulina

This is quite interesting for improving indoor air quality as well. We know high levels of CO2 cause a cognitive decrease. Maybe the solution is a bioreactor in every meeting room?

Someone would have to do the math on how much spirulina + light you’d need to process e.g. a conference room’s worth of adult’s CO2

enough algae to balance out one person's daily CO2 generation is in the hundreds of gallons, it's a fun idea but wildly impractical compared to opening a window or using a fan

Actually not that much: The russian 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_spacecra...) gives a thorough overview over the possibilities for plant-based oxygen generation.

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

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.

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.

Are you suggesting that the parent should grow spirulina and feed that to BSFL and then feed the BSFL to the fish?

Yes, or to chicken

what fish?

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

Define "high levels"?

More likely a calcium hydroxide, or a lithium scrubber, as amine scrubbers will make you smell like a submariner.

Is a bioreactor an amine scrubber?

A scrubber is a way simpler, and can operate continuously.

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