Initially, eight people (or biospherians) lived in the building for two years, trying to use only the food, water and oxygen that Biosphere 2 could produce. Although it was 20 years ago, I remember it all happening and the main story on the news was that it didn’t work. Having visited now, I know quite a bit more about it and there were three main problems:

• First – they underestimated the amount of CO2 that the curing of the concrete would absorb. This in turn led to the plants photosynthesising less which meant that there was less oxygen being produced.
• Second – it was an El Nino year and so Arizona was (very unusually) cloudy for much of the Winter, meaning that the plants again didn’t photosynthesise as much as predicted.
• Finally, they underestimated how much oxygen the microbes in the soil would absorb.

All this led to the oxygen content of the sealed space gradually declining until it reached 14% rather than the 20% we’re all used to. This wasn’t dangerous as such but made it really hard to work and made them all a bit grumpy so there was a split after 10 months that never healed. Half of the biospherians refused to talk to the other half – they even gave the two teams names: ‘them’ and ‘us’. In the end, once they had worked out why the oxygen levels had gone down, they added some more so they could continue to stay in the experiment.
I’d read about the project in Kevin Kelly’s Out of Control but hadn’t realised quite how big it was. It’s on a scale pretty similar to the Eden Project in Cornwall but its purpose was far more tightly defined. And the engineering is far more impressive, especially considering how quickly it was built. Only 10% of the air was lost during the 2 years and 20 minutes of the first experiment which is less than the Space Shuttle lost in a single mission and none of the water in the system was lost at all – which is incredible. The underground systems that kept everything working are huge and give you some idea of what we’d need to keep ourselves alive in space or on another planet. It’s the closest I’ve ever come to seeing a spaceship in action.

I also didn’t know that one of the biospherians was British. She’s Jayne Poynter and her talk at TEDxUSC is well worth a watch.

20 years on and Biosphere 2 itself is starting to age a little. It’s now managed by the University of Arizona and the site of a number of scientific experiments – particularly about how water affects ecosystems. It’s all good stuff but not quite with the ambitions of the original project. None of the projects require the original airtight seals. Biosphere 2 now mingles fairly freely with Biosphere 1 as the structure has degraded and the windows have gaps where maintenance has slipped. Just looking around you realise it would take a lot of work to get the thing working properly again.

The received wisdom is that Biosphere 2 was a failure but having learned a bit more about it I don’t think it was at all. A little written story is that the second batch of biospherians thrived. Having sealed the concrete and improved the food growing systems, they didn’t have problems with breathing and managed to be completely self sufficient food wise. They didn’t fix the human relationship problems though – the experiment ended after 10 months after the mission director fell out with the management.

If you happen to be in Southern Arizona, it’s well worth a visit.