# Algae producing oxygen in diving cylinder?

• CognitiveNet
In summary, the conversation discusses the potential use of algae as a source of oxygen for diving. While it is theoretically possible, the practicality and difficulties involved make it less feasible compared to conventional gas cylinders. The conversation also mentions the potential use of algae in space, but the current technology and limitations make it a less viable option for now.
CognitiveNet
Since algae can produce oxygen in closed containers, which you can inhale as a byproduct, when provided CO2 from your lungs; you could in theory take diving cylinders filled with algae with you, when diving, correct? I suppose this hasn't been done before, why not?

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Did you check how much O2 they produce? I did not find that number, but something like ~100 biomass tons per year and hectare http://humanities.uchicago.edu/orgs/institute/bigproblems/Team1-1209.pdf. Assuming this is purely carbon from CO2, it releases about ~200 tons O2. Downscaled, this is 0.5milligram/(m^2*s) in full sunlight. NASA calculates ~10mg/s for a human, this would require 20m^2 of algae (more, if you dive so deep that a part of the sunlight is blocked). Not really practical compared to conventional gas cylinders.
Air exhaled from your lungs has a high CO2 concentration, so it might improve growth a bit. But still... does not look practical.

mfb said:
Did you check how much O2 they produce? I did not find that number, but something like ~100 biomass tons per year and hectare http://humanities.uchicago.edu/orgs/institute/bigproblems/Team1-1209.pdf. Assuming this is purely carbon from CO2, it releases about ~200 tons O2. Downscaled, this is 0.5milligram/(m^2*s) in full sunlight. NASA calculates ~10mg/s for a human, this would require 20m^2 of algae (more, if you dive so deep that a part of the sunlight is blocked). Not really practical compared to conventional gas cylinders.
Air exhaled from your lungs has a high CO2 concentration, so it might improve growth a bit. But still... does not look practical.

"6 liters of algae water will produce 600 grams of "food" (540 grams is 2500 calories, an average daily food requirement), 600 liters of oxygen, and consume 720 liters of CO2"

This does not include any time for the production, nor the required sunlight.
And "liters" is a volume, it depends on the pressure and temperature.
If I assume 600 liters of pure oxygen at standard pressure/temperature, this corresponds to ~1kg. With the additional assumption that the numbers are supposed to correspond to 1 day, it is ~10mg/s and enough for a human. As cross-check: In the same time, the human eats those 600g food, and converts the oxygen back to CO2 (720l are ~1.4kg). Looks quite consistent.
Now, how much radiation and which CO2 concentration do you need to get that?

mfb said:
This does not include any time for the production, nor the required sunlight.
And "liters" is a volume, it depends on the pressure and temperature.
If I assume 600 liters of pure oxygen at standard pressure/temperature, this corresponds to ~1kg. With the additional assumption that the numbers are supposed to correspond to 1 day, it is ~10mg/s and enough for a human. As cross-check: In the same time, the human eats those 600g food, and converts the oxygen back to CO2 (720l are ~1.4kg). Looks quite consistent.
Now, how much radiation and which CO2 concentration do you need to get that?

To make the world a little easier for you, here is a video:

The papers from the space agnecy or what ever was saying that 6 liters was enough to keep a man alive, indefinetly.

CognitiveNet said:
To make the world a little easier for you, here is a video:
That sounds almost insulting. The video never answers the question. Nor does (paraquote) "keeping a man alive indefinitely" answer whether this refers to oxygen or food requirements. In fact I don't see where in the video such a claim was even made at all.

Perhaps the video was just easier for you?

CognitiveNet said:
To make the world a little easier for you, here is a video:

The papers from the space agnecy or what ever was saying that 6 liters was enough to keep a man alive, indefinetly.

Have you considered the difficulty of providing light to the algae, the time it takes to produce the oxygen, the overall difficulty in culturing algae in a closed tank, and other major drawbacks?
It is simply far far easier to use standard pressurized air in diving tanks. In cases where you need air for a longer duration you can use a re-breather. Past that...well you should probably make sure you can come back to the surface before needing more.

Most of the same difficulties apply for uses of algae in space. Perhaps once we have manned spacecraft far away from Earth where they cannot be refueled regularly we will look into this.

## 1. How does algae produce oxygen in a diving cylinder?

Algae produces oxygen through the process of photosynthesis, where it uses sunlight to convert carbon dioxide and water into glucose and oxygen. This oxygen is then released into the surrounding environment, including the diving cylinder.

## 2. Is algae the only source of oxygen in a diving cylinder?

No, algae is not the only source of oxygen in a diving cylinder. The majority of the oxygen in a diving cylinder is supplied by a compressor, which compresses and filters air from the surface. Algae only contributes a small amount of oxygen through photosynthesis.

## 3. How much oxygen can algae produce in a diving cylinder?

The amount of oxygen produced by algae in a diving cylinder can vary depending on factors such as the type of algae, amount of sunlight, and the size of the cylinder. However, on average, algae can produce around 5-10% of the total oxygen in a diving cylinder.

## 4. Can algae in a diving cylinder be harmful to divers?

No, algae in a diving cylinder is not harmful to divers. In fact, it can be beneficial as it helps to replenish the oxygen supply in the cylinder. However, if the algae growth becomes excessive, it can clog filters and valves, which may cause equipment malfunctions.

## 5. How can divers prevent algae growth in their diving cylinders?

Divers can prevent algae growth in their diving cylinders by regularly cleaning and maintaining their equipment. This includes rinsing the cylinder with fresh water after each dive and storing it in a cool, dry place. Using an air filter can also help to prevent algae growth by removing any spores before they enter the cylinder.

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