WEEK #10

I've got further into the CO2 feeding issue.

There several ways which would be interesting for my scale. Some are from existing technologies, some are my ideas:

• Citric Acid + Baking Soda = CO2

This solution produce CO2 out of the chemical reaction between Citric Acid and Sodium Bicarbonate. As I calculated before,  I need about 112 g of CO2 a day to boost the growth efficiently.

Thus I had to calculate the yield of this first solution. How much Baking Soda and Acid do I need in order to get 112 g of CO2.

The chemical equation: 1 C6H8O7 + 3 NaHCO3 → 1 Na3C6H5O7 + 3 H2O + 3 CO2 

I found that I need 164 g of Citric Acid and 216 g of Sodium Bicarbonate every day ! 

This is a lot and require purchasing those elements from a factory. And for the acid it's equivalent to 1233 lemons a day !! This not efficient !

Conclusion : NO

• Sodium Bicarbonate feeding

We need 2 to 6 kg by kg of spirulina. Therefore, when we harvest 140 g of spirulina we need to inject around 560 g everyday. This doesn't look very sustainable... Unless we live in area with a lot of trona ores that we could easily extract transform into baking soda.

Conclusion : NO (but it's the most used technique)

• Fermentation Sugar + Yeast = CO2

There 2 reactions possible:

- Aerobic fermentation: C6H12O6 + 6 O2 → 6 H2O + 6 CO2 + energy

- Anaerobic fermentation: C6H12O6 → 2 CH3CH2OH + 2 CO2 + energy

As you can see the aerobic fermentation produce 4 time more CO2.

Later I will try to get some accurate calculation. But this process is way less stable than the acid and baking soda reaction. Also the reaction depend on the catalyzing rate by the enzymes of the yeast.

However, this would be a non-negligible source of CO2. Plus, the idea would be to send the CO2 emission from a food/human/animal waste composting reactor back into the spirulina greenhouse or directly into the ponds by an injector/diffuser. I need to develop this idea to see how I can integrate it in a living system.

Conclusion : not a lot but still interesting and good to combine with something else

• Human exhalation live capture

Humans exhale around 1 kg of CO2 everyday. This is 9 times what we need for our culture !

However this is very difficult to collect because the air we breathe out is composed by (still) 14% O2, 78% N2, 4% CO2.

But, in a closed room where 1 or more human is sleeping the concentration in CO2 increase. For example, outside it's supposed to be 400ppm of CO2 and inside in a room windows closed, it easily reaches 1500 ppm and more. In a classroom or office it can reach 3000ppm. 

One solution would be to send the air of a bedroom (or a room with humans or animals) directly to the greenhouse. Again some calculations are needed to get rates and yields. 

Conclusion : not a lot but still interesting and good to combine with something else

• Volcanic gases capture

Volcanic gases are very rich in CO2. If this living system is installed in a volcanic zone I guess it would be possible to capture gases directly from the soil.

Here we can see the composition of different fumarolic gases : https://www.sciencedirect.com/science/article/pii/S0377027396000960

The sulfur emission could be a problem for spirulina. Maybe we can find easy ways to neutralize it.

Conclusion: Need calculation

• Soda lakes input

Soda lake are already rich in CO2 it could be an interesting input to drain and change the water. If this living system is implemented near by a soda lake, it would be very useful.

Conclusion: Need calculation and further research

• Urine feeding

Urine contains almost all of what spirulina needs including carbon. Feeding the culture exclusively with urine increase the spirulina growth to around 2 g/m2/day. (need some more clarification and calculation).

Conclusion : Good




________________________________________________



True autonomy (and freedom) is to go back in time and be hunter-collectors again.

I think it's only important to reduce our consumption to the size of earth.
Therefore, there will always be dependencies to certain mines and factory but we need to minimize it, in order to make their impact on the environment very very tiny. 

I conclude that a society system is needed to continue.