Trees come in an abundance of shapes and sizes, so their capacity to absorb CO2 varies wildly, from about 12 lbs per tree per year in forests typical of the US Northeast, to 50 lbs CO2 / tree-year for tropical trees. For the estimates below, I use 25 lbs CO2 / tree-year for a mature tree.
The question is: how many miles can you drive on the carbon absorbed by one tree? The answer, not surprisingly, depends on the fuel economy of your car. To find the number of miles offset by a tree in a year, you take the MPG of your car, multiply that by the amount of carbon absorbed annually by a single tree (25 lbs CO2 / tree-year), and divide by the amount of carbon released by burning a gallon of gasoline (19.4 lbs CO2 / gal). In short,
Miles / tree-year = 1.29 * MPG
It's a good reason to move ourselves around in a way that emits as little carbon per mile as possible.
Americans drive, on average, 13,500 miles a year. Supposing, generously, that you do that in a high-efficiency car (50mpg). You would need 210 trees to offset your annual driving, or about a third of an acre of forest (assuming 700 trees per acre).
You couldn't fit 210 trees in the average back yard.
By all means, plant a tree: we need every one of them (besides, they are beautiful). But it has more, and more immediate, impact to adjust your buying habits to prevent the cutting down of tropical forests. For instance, palm oil (called "vegetable oil" in ingredients lists) comes from palm plantations that have replaced old-growth tropical rainforest. A floor made of exotic woods may stroke your vanity, but the trees the wood came from are probably better off left unculled from the Brazilian rainforest.I'm sure you can think of many more products that lead to the destruction of forests that act as the planet's life support system. Time to start avoiding those products!
Trees are such a valuable resource, and it's incredible that even they cannot balance our massive carbon footprint. I agree that we need to do everything we can to stop destruction of our forests. I'm reading a really interesting book right now called Eating Dirt, by Charlotte Gill. It talks about the massive tree cutting industry in the Pacific North West. It's sad, but very eye opening as to how much lumber we actually consume.ReplyDelete
Anyways, great blog! Have a great day!
Eye opening is what we need! even though it's not always an easy read. I'm going to look up Gill's book, thanks for the pointer.Delete
Wow ... I suspected that we'd need a LOT of trees to offset our driving but I've never seen the numbers before. That's dramatic! I recently learned something interesting about trees. When they are cut, they release all the CO2, which they've been absorbing, back into the atmosphere. So cutting them not only removes them as "cleaners", it actually adds to the problem. We need to change our view of exotic woods ... perhaps rather than see them as exclusive and a sign of wealth, we really need to see them as what they are ... disrespect for our environment.ReplyDelete
Wait: surely plants don't release _all_ their carbon when cut - except when they are used for fuel - don't they get mostly turned into humus? But yes, it's certainly better to leave them standing for their whole lifetime!Delete
I like your blog a lot, it is very cool to have a mom car blog where you show how much driving impacts on our environment without banning it totally. Great work and I really want to plant a tree now, not because I want to drive a car but to help the environment against the pollution we already have!ReplyDelete
Thanks, Martha, and good luck with your tree adventure. There are many cities that successfully use green parks as their "lungs": e.g. New York would be a real concrete desert without Central Park.Delete
Wow! I drive a minivan; I wonder how many trees are needed to offset that.ReplyDelete
Thanks for linking up at Motivation Monday! Hope to see you wheeling in next week.
Take heart, Barb! Don't you have a large family? Then a minivan is totally justified, since as long as you fill every seat your minivan's carbon footprint _per passenger_ rivals that of European trains! It's only when it's just you in the minivan that the trains come our way ahead (did the math once for Thanksgiving travel: http://www.cellomomcars.com/2012/10/how-will-you-travel-for-thanksgiving.html )Delete
Thanks Cellomom, the numbers of trees to plant for each person to offset their driving miles are huge. The only solution for this would be to take the bus or ride the bike to work if you can. It also healthier for the person.ReplyDelete
Hi Mauro, your suggestion would be a win-win solution for the long term! To reach that place, we need a serious re-think of how we live: so many of us are stuck in suburbia now.Delete