How many plants do I need to breath?

January 12, 2006 10:55 PM

Given an airtight room with bright enough lights to fuel photosynthesis, how many plants would it take to provide an average person, at rest, with sufficient oxygen (assuming it is possible at all).

I have tried to google around for resting heart rate O2 consumption and plant / photosynthesis O2 production, but while I can find equations they don't seem to suggest rates. This is just idle curiousity but I really want to know. Thanks in advance.

posted by lucasks to Science & Nature (7 answers total)

These two pages provide a good jumping off point. They seem to use the same estimate for per-leaf oxygen production, but different numbers for the human side of things. Anyway, taken together, they give 300-400 and 500 plants. I figure that points towards 400, but of course it all depends on what you mean by 'plant.'

Also, my understanding is that algae and phytoplankton have the best oxygen production rates, but I don't have a reference for that handy.
posted by jedicus at 11:11 PM on January 12, 2006

In 1991, some people tried to create exactly this type of airtight room in the Arizona desert. They had 3.15 acres for 8 people, but they were ambitious and tried to reproduce a complete closed ecosystem that could feed people as well as provide oxygen. Their experiment failed, but you might try Googling "Biosphere 2" and tracking down the scientific papers that came out of it.
posted by fuzz at 11:23 PM on January 12, 2006

i think it would be a difficult experiment to predict as different plants carry out photosynthesis at vastly different rates. also environmental factors that would affect the rates of photosynthesis (ie. temperature, water supply, the concentration of CO2 in the surrounding air etc) could not be sufficiently predicted.

Also, individual consumption of O2 by humans would be different too.
posted by tnai at 4:37 AM on January 13, 2006

and also, as jedicus pointed out, algaes and phytoplankton in our oceans is said to produce as much as half of all the O2 that we breath. with plants being quite slower in carrying out photosythesis. I have a feeling (though no proof) that the small quantity of plants you would be able to fit into a room would be insuffcient to meet O2 requirements.
posted by tnai at 4:42 AM on January 13, 2006

Reminds me of my professor's questions about estimating the daily flow of the Mississippi or the amount of ATP in the average human body.

It seems guvmint scientists answered a similar question with 300-400 plants (assuming a plant with 30 leaves of average size). Since high carbon dioxide concentrations can be toxic to humans and low carbon dioxide concentrations are bad for plants we should also take take CO2 uptake and production into account, so I'll probably go poke into that this afternoon.
posted by Mercaptan at 6:42 AM on January 13, 2006

Make sure you keep the lights on.
posted by Rothko at 7:30 AM on January 13, 2006

The problem with Biosphere 2 wasn't that the plants didn't create enough oxygen or that the animals used too much. As it was explained to me, they hadn't realized ('cause nobody had ever done anything like this before...) that the cement the had used in the flooring absorbed some of the oxygen in some sort of chemical reaction going on within it.
posted by pwb503 at 2:41 PM on January 13, 2006