Tuesday, October 16, 2012

How many trees are needed to provide enough oxygen for one person?

Short answer: 8 trees

Long answer (but why take the trouble to read further if you already know the answer?):

Simple. It's to satisfy your (and my) curiosity; to answer your how, why, what, etc. Or just for a the fun of it. Whichever the case maybe, it's good to know.

Rainforest tree at Forest Reserve of Poring Hot Spring, in Ranau Sabah.

The mechanism behind the production of Oxygen

Trees release oxygen when they use energy from sunlight to make glucose from carbon dioxide and water. Like all plants, trees also use oxygen when they split glucose back down to release energy to power their metabolisms. Averaged over a 24-hour period, they produce more oxygen than they use up; otherwise there would be no net gain in growth.

It takes 6 molecules of CO2 to produce 1 molecule of glucose by photosynthesis, and 6 molecules of oxygen are released as a by-product. A glucose molecule contains 6 carbon atoms, so that’s a net gain of 1 molecule of oxygen for every atom of carbon added to the tree. A mature sycamore tree might be around 12m tall and weigh 2,000kg, including the roots and leaves. If it grows by 5% each year, it will produce around 100kg of wood, of which 38kg will be carbon. Allowing for the relative molecular weights of oxygen and carbon, this equates to 100kg of oxygen per tree per year.

So, how many trees?

A human breathes about 9.5 tonnes of air in a year, but oxygen only makes up about 21% of that air, by mass, and we only extract a little over a third of the oxygen from each breath. That works out to a total of about 740kg of oxygen per year. Which is, very roughly, seven or eight trees’ worth.

Fact source is from Sciencefocus, but the picture is mine.


tehr said...

pokok kat rumah aku ni tak banyak daun
mungkin perlu bilangan lebih

HoneyBUZZin said...

The place where I live now are surrounded by large trees. If i'm lucky, i could catch a glimpse of squirrel. The feel is different with trees around you.