By Peter Lesniak

In order to begin to offset our carbon dioxide (CO2) emissions we must know two things; how much carbon we produce, and the means by which to offset it. One possible way to offset our emissions is through trees. Trees remove carbon dioxide from the atmosphere through photosynthesis and store the carbon in their leaves, branches, stems, bark and roots. Approximately half the dry weight of a tree’s biomass is carbon.

On average, one broad leaf tree planted in the UK will absorb in the region of 1 tonne of carbon dioxide during its full life-time. It is best practice however to take into account that, for many reasons, not all trees will reach maturity. It is for this reason we will take each tree as able to absorb 0.5 tonnes of CO2, i.e. at half capacity, as advised by TCV.

Half-life of carbon dioxide in the atmosphere

Before diving into the numbers, it is important to know one thing about CO2, and that is how long it stays present in our atmosphere. According to NASA, once added to the atmosphere, carbon dioxide stays there for a long time – between 300-1000 years. Thus, as humans change the atmosphere by emitting carbon dioxide, those changes will endure on the timescale of many human lives.

Good news is that, in its early years CO2 dissipates relatively quickly; its half-life is roughly 27 years, which means that for every tonne of CO2 released today, half of it will remain in the atmosphere after 27 years. This is mainly due to carbon dissolving into the oceans. However, the rest is removed by slower processes that take up to several hundreds of years.

Estimating our carbon footprint

Let’s consider a simple example of international travel, as it is something we have all missed during lockdown. Personally, Italy is my country of choice due to its culture and cuisine. Flight from London usually takes 2.5 hours. Using the Eco Passenger calculator, the emissions from a typical UK-Italy return flight are roughly 760 kg CO2 per passenger (which reduce down to 380 kg CO2 after 27 year). As mentioned above, an average tree planted in UK will absorb 500 kg CO2 over its lifetime. Doing a rough calculation, the planting of 1 tree would help offset this trip.

I also enjoy car travel, and the car I drive produces 114 g CO2 per km. I drive around 10,000 miles a year, which is roughly equivalent to 0.9 tonnes CO2 after accounting for its half-life. The planting of 2 tree would help offset my car emissions. Of course however, the best route to take is to account for the carbon footprint before planning a trip, and not travel unnecessary, or travel more economically.

General way to estimate carbon footprint

Estimating travel emissions is relatively straight forward, since things get more complicated when we account for emissions associated with production of food we eat, heating of homes, running of hospitals, etc. A simple way to estimate our overall emissions is by leveraging the information available to us online. According to the UK National Statistics, the total CO2 emissions in 2019 accounted to 351.5 million tonnes. As the population of UK at that time reached 66.65 million people, we can therefore estimate the overall CO2 emissions per capita – 5.27 tonnes CO2 per year. Taking half-life of CO2 into account, we can conclude that planting 5-6 new trees each year would help to offset our overall carbon footprint.

More Trees Campaign

Since not everyone has the opportunity to plant trees themselves, we have launched the More Trees Campaign, aimed to plant 500 new urban trees in central London by the end of 2020. We would love you to be the part of our project. For more information visit our GoFundMe page. 

© Photo credits by https://unsplash.com/@crissyjarvis

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