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Comment by woleium | Hacker News Reader

iirc, biosphere failed because the concrete absorbed carbon dioxide and caused crop failure. interestingly, this allowed Dr Roy Walford et al to study calorie restricted optimal nutrition (CRON) diets and discover their effects, slowing the aging process.

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Edit: sorry, rereading this it sounds a bit abrasive. That wasn't my intent. I'd never actually read up on it till I read your comment and wondered how concrete absorbed CO2. It was a fun 30min of Wikipedia! I thank you for the distraction!

The concrete absorbed oxygen not CO2. I don't think there was a crop failure so much as too many people, not enough plants? Apparently they also miscalculated the amount of sunlight coming through the windows and so the amount of photosynthesis occurring, so maybe that is form of crop failure: does X grams of crop have fewer calories in of its been light deprived?

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

Interesting read. I was surprised to find Steve Bannon's name in there.

They ended up growing and eating so much sweet potatoes that they turned orange after a while. They had to pump oxygen into the biosphere 2

This is a fantastic read https://dartmouthalumnimagazine.com/articles/biosphere-2-wha...

[..] Microbes in our organically enriched soils had produced carbon dioxide at a greater rate than our young plants could produce oxygen via photosynthesis. We discovered that most of the missing oxygen was converted to CO2 and had been absorbed by the unsealed concrete in our habitat.[..]

We don't really know whether the aging process has slowed. Some biomarkers changed but that doesn't necessarily indicate a longer life.

On the BBC there was an episode where CRON was discussed. It showed a man who peeled an apple threw away the apple and ate the peelings. It seems bizarre but I think this will be a trend in a few years. It ticks boxes of less food waste, less bulk, high nutrition, ultra low calories. Whether it works or not who knows since many diets tend to be for status not health; veganism with its absence of B12, Atkins with its high fat, Paleo based on inaccurate pre-history.

A lot of people use diets for health, not for status. E.g. vegans often supplement B12 externally.

But that's the issue vegans can't live without artificially supplementing with B12. To me that shows the vegan diet is not valid or survivable. If you were on a desert island or stuck in a remote location and were vegan you'd be dead after a few years from B12 deficiency.

https://www.bbc.co.uk/iplayer/episode/b01lxyzc/horizon-20122...

How do you reconcile “He threw the apple away” and “Less food waste”?

Not just that apple but overall the fewer calories of CRON means less food consumed.

For a billion people, calories is the most important nutrition

I think that's the point of the "ON" part in CRON, optimal nutrition. Eat enough calories to survive but be healthy by getting optimal nutrition.

Concrete absorbs carbon dioxide even after it's set? Shouldn't it like... grow, then? From accumulated carbon?

Don't mean to waive you off or anything, just never heard this before and it doesn't seem to make sense at first listen.

I don't much about biosphere 2 specifically, but I have read that concrete absorbs CO2 over long timescales. Hundred-year-old concrete is chemically different than it was when it was a month old. I don't know if it gets denser, or if the CO2 replaces something else.

Concrete samples from inside and outside the structure showed strikingly different levels of calcium carbonate, which was rapidly being formed inside the domes as huge amounts of carbon dioxide reacted with calcium hydroxide in the concrete. ... Severinghaus said of the calcium carbonate. "It's 10 times more than outside."

From https://www.nytimes.com/1993/10/05/science/too-rich-a-soil-s...

But how much was it relative to the total volume of concrete?

“ Concrete continues to set and cure for months and years, increasing its strength over time. It's a long-lived giant chemical reaction that continues on long after it has set.”

Source: https://interestingengineering.com/why-concrete-doesnt-actua...

But it continues to take up the same volume of space, so isn't there a limit to how much carbon dioxide it can remove from the atmosphere and store?

Yes of course it has a limit. Nobody said that it is an infinite sink.

If you are interested in the details I can recommend J.P. Severinghaus et al., “Oxygen loss in Biosphere 2“.

I'm just surprised because somebody said that the concrete soaked up so much carbon that the trees alongside it in the biosphere were unable to grow.

That sounds like a lot of carbon. Like, a lot. I'd expect that it would have to absorb enough carbon that it could displace some amount of the volume that it would have appeared as in tree form.

Can you fit a third of a small forest into the concrete around that small forest? It seems unlikely.

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