Why am I helping to plant 4,000 trees when I don't like gardening?

I was watching ‘An Inconvenient Sequel’ this evening with my son who is 11 years old and was reminded of an off-hand comment that someone made a while back that all my long distance air travel may not be the most environmentally responsible.

That’s hard to argue against and sadly my actions or inaction will probably affect my children and other people’s children more than we can ever imagine.

With this in mind I decided to look at the numbers and see how much extra carbon dioxide was being generated and if there was anything I could do about it.

Giving up flying is the over simplified option but that isn’t realistic for me or most others so much better to first quantify it and then work out a way to reduce it on a sustainable basis to show how easily it can be done.

The first thing to do was figure out how much carbon dioxide is generated by flying.

What do the numbers look like…

A typical trip for me is DUB-EWR-SFO-EWR-DUB, yes there are usually some additional short haul stops but the bulk of my mileage is transatlantic and transcontinental and this trip usually delivers around 11,500 frequent flyer miles.

Taking the quick option and using this calculator tells me a return flight like this in economy generates 2.53 tonnes which converts to around 5,578 pounds of carbon dioxide emissions.

Typically I take ten of the DUB-EWR-SFO-EWR-DUB trips a year so they all add up to 25.3 tonnes which seems like a lot considering the output per capita in the United States is ‘only’ 16.4 metric tonnes per annum...

But I wanted to be sure, so let’s sense check this with some maths and chemistry...

Jet fuel is a hydrocarbon (carbon and hydrogen molecules in a chain) which burns in a jet turbine combining with oxygen (O2) from the atmosphere to create carbon dioxide (CO2) and water (H2O).

The chemical equation looks something like this...

C8H18 + O2 ? CO2 + H20

This chap has done the hard work figuring out the molecular weights and calculates that each gallon or 6.5 pounds of jet fuel will combine with 23 pounds of oxygen and produce 20 pounds of carbon dioxide plus about 9 pounds of water.

So now all we need to do is calculate my average miles per gallon with United...

The aircraft type varies, but I’ve been using the 777 more and more on both the transatlantic and the transcontinental legs so we will use it as the aircraft type for the rest of the calculations.

Airlines use the passenger mile per gallon for an aircraft to figure out how far a gallon of fuel will take a single passenger. On a 2,000 to 3,000 mile trip the 777 comes in at 81 passenger miles per gallon according to Boeing.

We know that my round trip is around 11,500 miles so that means I’ve been responsible for using approximately 142 gallons of jet fuel every time I fly to San Francisco and back.

Next by multiplying the gallons of fuel used by the amount of carbon dioxide generated per gallon of fuel used (20 pounds) we find that each trip I make pumps 2,840 pounds of greenhouse gas into the atmosphere.

Converting back to metric numbers this is the equivalent of 1.29 tonnes which at first glance seems to be quite off compared to the online calculator figures.

However these figures assume a fully loaded aircraft and also rate business and economy (where I usually fly) equally so we’ll hang on to to the calculator figure of 2.53 tonnes for now...

Besides, I’ve never had a car that matched the manufacturer’s fuel consumption figures so no doubt there is some optimism in the aircraft figures too.

Over 2.5 tonnes is significant over 11,500 miles but it could be worse, if I was using a rocket to get to the ISS which is 'only' 250 miles overhead it would generate about 300 tonnes of carbon dioxide to get just a few of us there.

So how do we get rid of it?

The easiest way to take carbon dioxide back out of the atmosphere and lock it back up as carbon is a process called photosynthesis.

Luckily trees are very good at this and have been doing it unsupervised for millennia and a quick Google search indicates that a single tree can store up to 48 pounds of carbon dioxide per year averaged over it's lifetime.

Here’s the equation:

CO2 + H2O ? C6H12O6 + O2 + H2O

Effectively a tree takes carbon dioxide from the atmosphere adds light and water and thanks to photosynthesis turns it into sugar, oxygen and water.

The bigger the tree the more carbon it can lock up so we should probably reduce the figure to 24 pounds of carbon dioxide stored per annum per tree.

My ten DUB-EWR-SFO-EWR-DUB flights all add up to over 55,000 pounds of carbon dioxide in a year so here is the calculation of the number of trees needed to cope with that...

55,780 pounds ? 24 pounds per tree = 2,324 trees

Clearly that’s going to be a challenge before my next trip plus I’m not overly keen on gardening. I also have some idea of the effort involved because 15 years ago I planted 500 beech trees when we built our home and it took quite some time.

To make matters worse I do take additional flights and I probably have some catching up to do for past efforts. All in all, I felt to be on the safe side I needed to round this number up to 4,000 trees.

And besides, irrespective of conflicting views on global warming no-one can argue that planting 4,000 trees is a bad thing, right?

Note: If you are still unsure, check out this article by Thomas Friedman in the NY Times and the Great Green Wall project to get a sense of the massive impact planting trees could have aside from carbon dioxide reduction.

Hunting around the internet for a while I eventually found Trees for the Future who are using reafforestation to change the lives of some of those who need it the most. They checked out on Guidestar and were a perfect fit for what I wanted to do so I’ve ordered up a forest!

A few hundred dollars doesn’t seem like a bad deal in exchange for helping to offset the carbon footprint generated by my airline travel for the next decade and also to help some others improve their lives, what do you think?

P.S. If you know anyone who flies even moderately this may be worth a share, I was surprised that despite the amount of flying I do there was something I could do about it. #beinconvenient

References:

https://climatecare.org/calculator/

https://www.arborenvironmentalalliance.com/carbon-tree-facts.asp

https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft

https://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions_per_capita

https://www.greatgreenwall.org/great-green-wall/

https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references#seedlings has much less optimistic calculations on carbon sequestration for trees <10 years old so the trick seems to be to maximise the life of the tree so it uses more carbon dioxide as it gets really big.