Trees: nature's carbon-eating machines

06 October 2020 | OVO Energy

Beautiful trees

We recently pledged to plant a tree for every OVO member – every year they’re with us. To celebrate this tree-mendous moment, we collaborated with Simkin Studio to create some awesome illustrations that showcase just how much carbon our trees will absorb. 

We also put our science hats on to take you through exactly why tree-planting is one of the most effective ways of taking carbon out of the atmosphere

Let’s see what blue whales, transatlantic flights, barbecues and humans all have in common...

Over the coming year, we’re planning to plant around 900,000 trees right here in the UK. We’ll do this with our partners at the Woodland Trust and through our I Dig Trees programme with The Conservation Volunteers. As we’ll explain later, we use the US EPA figure that tells us a single tree will absorb about 60kg (or 0.06 metric tonnes) of carbon dioxide over a 10-year period as it grows. So, at 60kg per tree, the 900,000 trees we’re planting will absorb an incredible 54,000 tonnes of carbon dioxide as they grow over the coming decade!

To help contextualise how much carbon that is, Simkin Studio’s beautiful illustrations have brought to life just what 54,000 tonnes of carbon dioxide might be equivalent to...

Carbon trees blue whales

The blue whale is the largest animal on earth.  An average adult blue whale weighs 136 metric tonnes2 (150 tons). So 54,000 tonnes of CO2 is equivalent to about 54,000 / 136 = 397 blue whales. 

trees carbon flights new york london

When aeroplanes fly, they burn jet fuel that releases greenhouse gases including carbon dioxide. In fact, for every kilometre that’s travelled by a passenger on an average long-haul flight, 0.19562kg of CO2 is released according to UK government data3. We know that it’s a 5,585km flight to get from London to New York. So using this info we can work out that every passenger flying from London to New York releases 5,585 x 0.19562kg = 1.09 tonnes of CO2. This means that, for the 54,000 tonnes of CO2 absorbed by OVO’s trees, you could fly 54,000 / 1.09 = over 49,000 people from London to New York.

trees carbon barbecues

When you light up a gas-fired barbecue, you start burning fossil fuels (usually propane), which releases carbon into the atmosphere. Cooking up a hearty meal on a typical gas barbecue releases about 2.56kg (0.00256 tonnes) of carbon dioxide.  So, for 54,000 tonnes of CO2 absorbed by OVO’s trees, you could have about 54,000 / 0.000256 = 21.1 million barbecues.

Just like there’s no average tree, there’s no average human. But according to one global study, the average weight of an adult human is 62kg (or 0.062 tonnes).  So 54,000 tonnes of CO2 absorbed by OVO’s trees is about the same weight as 54,000 / 0.062 = 870,968 humans.  

How trees eat carbon: we explain 

It’s all well and good celebrating the carbon-busting benefits of our tree planting, but you might be wondering just how trees manage to do all their magical work.

And the answer is through photosynthesis. In this clever process, every tree absorbs carbon dioxide through its leaves and converts it into sugars that it can use to grow. And over time, as the tree grows it locks away the carbon it’sabsorbed from the atmosphere in its branches, trunk and roots - so that it’s no longer contributing to global warming. Happy days.

The amount of carbon a tree absorbs can vary 

Because, as you can imagine, it depends on all sorts of things. Like the species of tree, the context in which it’s planted (e.g. a woodland vs a city street), the climatic conditions (from chilly forests in the Arctic to tropical rainforests) and how it’s managed. 

But to give us a sense of how much carbon OVO’s trees will absorb, we use estimates. These are calculated by scientists, based on research they’ve done on trees planted in similar areas to where we plant our trees4.  

As we’ve already touched on, over a 10-year period as it grows, it’s estimated that one tree planted in an urban setting absorbs about 60kg (or 0.06 metric tonnes) of carbon dioxide (according to the US EPA).  As well as this, analysis from our friends at the Woodland Trust estimates that one tree in a UK woodland absorbs about 250kg of carbon dioxide over its lifetime.  

We hope that all of OVO’s trees live long and full lives – for many decades or even centuries! But, sadly, some trees won’t survive to reach their full carbon-eating potential due to natural causes, like damage during storms or drought. Or man-made causes, like being vandalised. 

So, to be conservative, we used the EPA’s estimate of 60kg of carbon dioxide absorbed over a 10-year period as a tree grows to calculate how much CO2 our trees will absorb for these illustrations. 

But we hope that our trees will survive to see OVO become a net zero carbon business in 2030, and go on to absorb more and more carbon over their lifetimes. That might be around 250kg if we take the average figure – but could even reach up to 500kg of CO2 in the case of a 30cm diameter English oak. 

That’s a whole lot of carbon

It sure is! Planting trees is great – but it isn’t the only thing we need to do if we want to keep global temperatures within safe limits.  Yes, trees suck carbon out of the air,but it’s better not to let carbon enter the atmosphere in the first place. 

At OVO, tree-planting will complement the other important ways that we’re fighting the climate crisis. We’re bringing OVO members 100% renewable energy as standard, reducing the carbon emissions from our own operations, helping our members be more energy efficient, supporting renewables and developing low carbon technologies for heat and transport. Phew.

So, although they aren’t a silver bullet, trees are an important part of the solution. 60kg of CO2 per tree might not sound like much – but when you scale that up to thousands of trees planted in hundreds of schools and parklands across the UK, it’s easy to see just how much good they can do. 

Scientists estimate that natural climate solutions, like trees, could offer as much as 37% of the carbon emission reductions needed to keep climate change within the limits set by the Paris Agreement. A whole lot of carbon, right there.

If you’re keen to learn more about all things carbon, we’ve put together a nifty jargon-busting guide to help you feel informed, empowered – and able to tell your carbon dioxide from your greenhouse gases.

And, of course, if you like the sound of 100% renewable, tree-planting energy check out our carbon-busting energy plans and more.

1 - Each year, OVO plants 1 tree for every member in partnership with the Woodland Trust. Trees absorb carbon dioxide from the atmosphere, so tree-planting helps to slow down climate change. 

2 - According to The Marine Mammal Center

3 - Based on UK BEIS emission factors 2019

4 - The trees we plant with our tree-planting partners through I Dig Trees and the Woodland Trust’s school and community tree packs scheme are grown in urban, peri-urban or rural settings across the UK.

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