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Estimates vary with species, age, climate and site, but a widely used figure is around 21 kg of CO₂ per year for a mature broadleaf tree — and something like a tonne over a ~100-year lifetime. A young sapling absorbs very little; a tree hits its stride only after years of growth.
That's exactly why TreeMonkey frames trees as a way to picture a tonne of CO₂, not as an offset you can bank. One tonne ≈ 48 trees working for a year — a vivid image, and a reminder that not emitting it in the first place is far quicker than growing it back.
Source: Forest Research and commonly cited urban-tree estimates. Figures are illustrative UK equivalents.
Related reading
Frequently asked questions
Is 21 kg exact?
No — it’s a representative figure for a mature broadleaf. Real absorption depends on species, age, climate and management, so treat tree counts as illustrative.