Archive | November, 2016

Plant two trees per hour of flight

1 Nov

How many trees do I need to plant to offset the carbon dioxide released in a flight?

If you look at the sites that calculate this, they come up with very complex calculations and many ifs and buts. Of course, there are many variables, but that does not help you to have a simple rule to apply if you want to help fight global warming and practical rule to compensate for your CO2 emissions during flight. That is how I got to the simple rule:

PLANT TWO TREES FOR EVERY HOUR OF FLIGHT

How did I arrive at that number?

First the amount of carbon that is emitted for your flight. Most carbon calculators work with 250 kg/550 pounds of CO2 per passenger per hour of flight. Yes, there are variables as per aircraft type, how long is your flight, if you fly coach or business etc. but let’s stick to this number.

If you plant a tree the CO2 take up as a sapling is of course low, so you need to assume that the tree is planted and protected well and half of them come to full size. It also depends per species and in general trees in the tropics absorb more CO2 than those in temperate zones. Given all this variability we take as a rule of thumb that a full-grown tree absorbs 20 kg/45 pounds of CO2 per year out of the atmosphere. Let’s keep the lifespan of the tree at 40 years, after which time it is cut down and used as timber, keeping the carbon sequestered. During the first 20 years, the CO2 absorption will go from zero to 20 kg per year, so you come to 600 kg/1320 pounds for the entire lifespan of the tree. With half of the saplings not making it to a full-grown tree, we come to 300 kg average per planted sapling over the course of its life.

However, the CO2 that you put in the air on the day of your flight, is starting to warm the Earth immediately, while your sapling is only slowly starting to have a real effect after a quite a few years, for which you need to compensate. CO2 brings peak heat within a decade of being emitted, with the effects then lingering 100 years or more into the future. So, you need to pay ‘’heat interest’’ over the delayed effect of your tree and for that sake we double the amount of captured CO2 needed in your trees to compensate for the early heat effect of your flight. So now you need to double the number of saplings.

Calculation:

1 hr of flight = 250 kg of CO2 emitted

1 tree over its lifespan is 600 kg of CO2 sequestered, so a full-grown tree sequestration capacity amounts to 2 hours and 24 minutes of flight.

½ of your trees do not make it, so per sapling you sequester 300 kg of CO2 or 1 hour and 12 minutes.

Delayed heat absorption effect necessitates doubling of sequestration so now your sapling only gives you 36 minutes of flight.

Rounding this off you come to 2 saplings per hour of flight.

And to help a bit more, you could do both: planting the trees and paying for the offsets through the plan the airline offers you 🙂

If you cannot plant your own trees, you can have them planted for you. My favorite is http://www.treesisters.org/

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