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Comment by CapitalistCartr | Hacker News Reader

I can't figure out what would be providing more CO2. The container is near full of greenery; where does it get air exchange? Maybe the cork leaks just enough is all I can figure.

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Plants suck in CO2 when they are storing energy, but when they spend their energy they make CO2 just like us. Plants have a respiration process just like animals. They just tend to remove more CO2 than they put out (until they get burned/turn into coal, oil, etc)

Bacteria in the soil. One of the reasons Biosphere 2 fell apart.

> Biosphere 2 fell apart

Wait, what's this? What happened?

Biosphere2 was an experiment to seal humans and plants i to a dome and not open it for some time.

Fungus and other pests destroyed some important plants and the eco system collapsed.

It had been built in the middle of a desert but urban expansion means the site is reasonably near housing now.

There were a bunch of photos of the dusty derelict interiors floating around a few years ago.

I kind of wish people would try again, just becuase.

I thought the biggest problem was the concrete. That is, soil microbes produced excess CO2, which would have been okay because the plants should have been able to photosynthesize it to O2, but instead the excess carbon dioxide reacted with the concrete, thus reducing the O2 levels.

Ah, here's a summary of the various things that went wrong, including details about the concrete: http://biology.kenyon.edu/slonc/bio3/2000projects/carroll_d_... .

It doesn't mention fungus, but does talk about other ecosystem problems (the pollinating insects died out, the morning glories took over, etc.).

Evidently it's not derelict anymore... the University of Arizon has owned it since 2011. Lookin' pretty cool!

https://en.wikipedia.org/wiki/Biosphere_2

If you're ever in Tucson, you should go for a tour. It's a fascinating place, and they've repurposed the facility to do a lot of worthwhile and interesting science.

I can't see how decaying plant matter would provide enough CO2 to keep the larger greenery healthy. Perhaps the original soil had an exceptional amount, but it would take time for it to break down; plants can empty a container such as that of CO2 in a day or so.

Isn't it how the world worked before animals evolved? Or is there some yet another source of CO2?

Fungus produces CO2 from plant tissues as well, so they are probably an important component of this ecosystem.

Did you just imply Fungi are plants?

Huh... no, what would make you think that?

From what I understand the container was sealed 11 years after the initial planting. I guess all the carbon entered from the atmosphere before the final watering in 1972. The total biomass must have remained roughly constant since.

From a related article: "But the eco-system also uses cellular respiration to break down decaying material shed by the plant. In this part of the process, bacteria inside the soil of the bottle garden absorbs the plant's waste oxygen and releasing carbon dioxide which the growing plant can reuse."

Was this a planned hack, or does this naturally occur?

My first thought was also, "Where does the CO2 come from?"

I suspect this is a very fine balance - if you're off by just a little, one or the other would die. There's not much room for error in a jar.

> I suspect this is a very fine balance - if you're off by just a little, one or the other would die.

This is an illusion; it's a dialectic between the two. Problems lead to a shift in balance, not a death.

Most bacteria and plants can survive in a huge range of CO2 and O2 concentrations. Humans are the ones that cannot.

> I suspect this is a very fine balance - if you're off by just a little, one or the other would die. There's not much room for error in a jar.

Why would all bacteria die if there is less oxygen? I imagine the weakest bacteria would die, thereby increasing the amount of O2 per bacteria, and thus reaching equilibrium again.

> There's not much room for error in a jar.

Article mentions that most of the jars failed.

Exactly, where is the plant mass coming from? Can bacteria break soil down into carbon that the plant can use to build more leaves/stems/roots?

The container was last watered twelve years after it was planted. Twelve years is plenty of time for most plants (especially something many people would consider a weed) to reach that size. At this point it's simply in maintenance mode - similar to a bonsai which never requires trimming.

The Daily Fail version claims so, but that doesn't seem sufficient. Nonetheless, its clearly working. It'd be interesting to insert a probe through the cork and run a real-time analysis of the air composition.

I don't think we can say it's clearly working... This seems like an extraordinary claim and it's hard to know if there's any truth fudging.

Another puzzling factor is the clarity of the glass. When I've seen bottle gardens, they all develop a thick scum from minerals in condensation, algae, and bacterial plaques.

This is a great GREAT point.

It would be nice to hear an explanation.

Magnetic scrubbing brushes. They're commonly used in aquariums.

There is also, Cellular respiration in night within the plant itself, which release some CO2 in the atmosphere. So may be combined with CO2 released by Bacteria and Cellular respiration in plant, it can survive.

Hmm. So over time the soil mass will decrease into nothing as the plant expands?

Bits of the plant are going to decay back into soil.

Most of the mass of plants comes from the atmosphere, not the soil. 95%+ of a given plant is oxygen, hydrogen, and carbon. The soil provides trace elements and a place from which to absorb water.

Aerobic bacteria takes in oxygen and produces CO2 in the same way that animals do.

Probably root fungus and bacteria symbiosis. These have been made in biology classes for decades, this is just a particularly massive example.

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