CO2
It strikes me as nothing short of miraculous that trees and humans are symbiotic in that we humans breathe in oxygen while trees breathe it out. The opposite is true for Carbon Dioxide (CO2). One species’ waste is another species’ resource. How about that for circular economy? It turns out that chlorophyll – the chemical that allows trees to store sunlight – is very similar to the haemoglobin in our blood. The two chemicals differ in that the iron in haemoglobin makes our blood red and the magnesium in chlorophyll makes the trees’ leaves green.
Haemoglobin delivers the oxygen we breathe in, allowing the carbon in our food to give us energy while chlorophyll allows trees to store energy from the sun while separating CO2 into the solid carbon in wood and the oxygen which they breathe out. Or something like that. Is that not mind-blowing? The mass of a tree comes largely from the air. Trees breathe in CO2 and turn it into wood.
In an attempt to offset our Charlotte flights, last Saturday a group of volunteers from Pianodrome planted 100 new trees at North Cloich hutting site in the Scottish Borders. One flight from Edinburgh to Charlotte produces around 490kg of CO2 so for a return it’s about a tonne.
To put this in context, the total average Carbon footprint per person in the UK including all travel, food, heating, infrastructure etc. is around 8 tonnes of CO2 per year. For the 6 return flights required to make this project happen Pianodrome produced around 6 tonnes of CO2.
Funnily enough Pianodrome Charlotte probably weighs around 6 tonnes so flying the build team over produced roughly an equivalent weight of Carbon Dioxide gas to the 40 or so pianos used in its construction. Heavy. Had these pianos been burned instead would this have produced as much CO2? But that's another question.
My question now is this: How long will it take for the trees we planted to breathe in the equivalent 6 tonnes of CO2 we produced and turn it into living timber?
Based on an hour’s googling my possibly flawed and highly approximate calculation is as follows: 6 tonnes of CO2 is roughly equivalent to 1.5t of Carbon (the other 4.5t is Oxygen). Divided between 100 trees that’s 15kg of Carbon per tree we planted. About half of the mass of a tree is Carbon therefore our trees will have to weigh 30kg each before collectively they have offset our flights. A tree weighing 30kg is around 12cm measured round its trunk. To grow to this size takes about 5 to 10 years.
On our weekly zoom meeting today Laura suggested we arrange a picnic at North Cloich to celebrate when the trees we planted have done their job of offsetting the Charlotte flights. Matt suggested we cycle there to reduce our carbon emissions on the day. So. On 22nd April 2033 you are all invited to cycle to North Cloich with us and have a picnic in the shade of our lovely trees!
One last calculation. A mature tree absorbs around 50g CO2 per day. Flying Edinburgh to Charlotte takes about half a day. To absorb CO2 at the same rate that your flight releases it on your behalf you need a forest of 10 000 trees. When I picked my 10 year old up from school today and told him all this he immediately jumped to the only conclusion I can meaningfully extract from this – we, humans, surely have to stop flying.
