How Much CO2 Does a Tree Sequester?

This is a simple question with a very complicated answer, which is nested in a million caveats! But the short answer is that, here at SearchScene, we assume that an average tree sequesters around 10 kg of CO2 per year over a 20 year lifespan, which gives us a total figure of 200 kg of CO2 per tree (over a 20 year lifespan).

Each tree planted sequesters 200 kg of CO2 (over a 20 year lifespan)

The real answer is extremely complex and depends on a wide variety of factors, such as the tree species, the age of the tree, its location, the growing conditions, water availability, sunlight, local climate, soil nutrients, its current growth stage, the root system and various site specific factors, such as biotic factors (e.g., insects, and other flora and fauna, diseases, etc.).

Our chosen tree planting charity is Eden Reforestation Projects and we invest in their general tree planting fund (at a cost of $0.10 per tree). This cost covers all expenses, including nursery costs, transportation of seedlings to the reforestation sites, planting, guarding, and weeding to allow a head start on vegetation. These trees comprise a variety of native species planted in Ethiopia, Madagascar, Nepal, Haiti, Indonesia, Mozambique and Kenya.

The largest factor in determining a tree’s CO2 sequestration rate seems to be the age of the tree, with young trees absorbing around 6 kg of CO2 per year (a figure that’s backed up by ecocharco.org), whilst mature trees absorb an average of around 22 kg of CO2 per year. Carbonpirates.com similarly claims a figure of between 6 kg of CO2 per tree (for a young tree) to 22 kg of CO2 for a tree that’s around 10 years old.

Ecotree.green features an in-depth analysis that concludes that a tree can absorb anywhere from 10 kg of CO2 to 44 kg of CO2 per year (averaging 25 kg of CO2 per tree), depending on a whole host of factors, whilst encon.be quotes a range of between 21.77 kg of CO2 per tree to 31.5 kg of CO2 per tree and has settled on a similar figure of 24 kg CO2/tree. However, it is important to note that these figures are based on mature trees, whilst we will be planting saplings.

Carbonify.com also quotes an average of 22 kg of CO2 per tree annually (but over 40 years), for trees planted in the humid tropics.

With so many sources quoting such a range of figures for an “average” tree (if there is such a thing), it can be hard to know which figures to rely on. It should be noted that some of these sources are from tree-planting schemes designed to offset your CO2, so it is in their best interests to cherry-pick higher figures for CO2 offsets, whilst other sources may not be independent and may have quoted each other. As we do not wish to be accused of greenwashing (or rather, treewashing) the figures, it is important to come up with a realistic and credible estimate for CO2 sequestration per tree.

With a general consensus of 6 kg – 22 kg of CO2 sequestered over a 20 year lifespan, our chosen figure of an average of 10 kg of CO2 per year per tree over a 20 year lifespan then seems like a very conservative estimate (and is based one what seems to be a very in-depth analysis by OneTreePlanted.org). This gives us a total of 10 kg x 20 years = 200 kg of CO2 sequestered per tree (over a 20 year lifespan).

Another factor to consider is that not all trees make it to maturity. As they grow trees may compete for resources and some may die or be destroyed – not all will achieve their full carbon sequestration potential. Apparently, around 80% of trees planted by Eden Reforestation survive. But each tree can also spread its seeds and give rise to other trees, with each tree becoming 3 trees. With regard to mangroves, earthly.org states that Eden Reforestation have discovered that tree mortality becomes irrelevant as natural regeneration occurs – whereby, typically, regeneration exceeds 200% of the original number of mangroves planted.

So with trees typically naturally multiplying in numbers by 2-3 times over the course of their lifetimes, we could reasonably state that the effect of planting a tree is not 10 kg/year of CO2 sequestered, but 20-30 kg/year of CO2 sequestered. Also, trees typically live much longer than the 20 year lifespan we’ve quoted – they may easily live longer than 40 years, so we could easily double the figures again and quote sequestration figures of 40 – 60 kg of CO2 per tree. But that seems like taking liberties with the data, so we will stick with our extremely conservative estimate of 10 kg/year per tree over 20 years.

As a rough guide, one search on SearchScene raises approximately $0.005 for charity. If you only selected Eden Reforestation Projects as your supported charity, then Eden would get the full benefit of that. At a cost of $0.10 per tree, you would plant a tree after just 20 searches. At a sequestration rate of 200 kg of CO2 over 20 years, each search on SearchScene would therefore remove around 10 kg of CO2 from the atmosphere (over the next 20 years). However, if you selected all 6 of our supported charities, Eden Reforestation Projects would only get 1/6th of the benefit of each search you make, meaning that each search on SearchScene would remove around 1.7 kg of CO2 from the atmosphere (over the next 20 years).

Web searches have been quoted by Google as contributing 0.2 grams (0.0002 kg) of CO2 to the atmosphere per search. As you can see, that figure is completely dwarfed by the CO2 sequestered by tree planting when you perform a search on SearchScene.

Of course, we have all seen the awful of news on TV of huge forest fires in Canada, the USA, Germany, and in other countries in recent years. When trees burn down, almost all the carbon they’ve sequestered over their lifetimes is released back into the atmosphere and all the money spent to plant those trees has been for nothing. We need to limit global warming so that forest fires become less frequent and less intense. Also, planting saplings is no substitute for the deforestation of mature trees that happens at an alarming rate in the Amazon rainforest and elsewhere around the world. This is why, at SearchScene, we don’t just focus on tree planting. We take a holistic approach to the climate crisis and allow you to support a range of charities with the searches you make. So whilst supporting Eden Reforestation Projects will enable you to fund tree-planting programs, your support for WWF will help fund lobbying to prevent deforestation in the first place as well as lobbying to cut the use of fossil fuels and help cut the carbon emmissions that are fuelling our warming climate that make forest fires more likely and more intense. Our other charities are also well worth supporting in the fight against climate change. You can read about them here.