How this calculator works
A natural Christmas tree is a crop. It absorbs carbon while it grows for six to ten years, and the question is what happens next: a tree that is composted or mulched releases little, while one that decays in landfill produces methane, a much stronger greenhouse gas. Ellipsos, a Montreal sustainability consultancy, measured a two-metre tree grown and sold locally at about 3.1 kg CO2e if it goes to landfill and about 0.9 kg if it is composted. A two-metre plastic tree made in China and shipped to Montreal came to about 48.3 kg CO2e, and it has to be reused for well over a decade before its annual share falls below the natural option. Driving to collect the tree also counts: a 16 km round trip in a petrol car adds roughly 2.7 kg CO2e, which can be more than the tree itself if the trip is only for that purpose.
Formula
transport (kg CO2e) = one-way distance x 2 x car factor, where the petrol factor is 0.17 and the diesel factor 0.19 kg CO2e per km. natural footprint = disposal factor x size multiplier + transport, with 3.1 for landfill, 0.9 for compost, 2.0 for burning and 0.3 for replanting, and size multipliers of 0.6, 1.0 and 1.8. plastic footprint = 48.3 x size multiplier + transport + 0.5 for disposal. annual plastic footprint = lifetime footprint / years reused. Break-even = plastic lifetime / natural annual footprint.
Worked example
A medium natural tree, 8 km away, collected by petrol car and composted. Transport is 8 x 2 x 0.17 = 2.72 kg CO2e and the tree is 0.9 kg, for 3.62 kg a year. The same trip for a plastic tree gives 48.3 + 2.72 + 0.5 = 51.5 kg. At that natural footprint the plastic tree needs 51.5 / 3.62 = 14 years to break even.
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Frequently asked questions
Is a real tree better than a plastic one?
For a typical household that buys a plastic tree and uses it for six or seven years, the natural tree usually wins, especially if it is composted and collected without a special trip. A plastic tree used for 20 years can come out ahead, but only if it is actually kept that long.
Does the tree have to be chipped or mulched?
Any end that avoids landfill helps. Many municipalities collect trees for chipping into mulch, which avoids the methane from anaerobic decay. Burning releases the stored carbon at once but avoids methane, so it lands between composting and landfill.
What about a living tree with roots?
A replanted tree can be reused for several years and has the lowest footprint of the natural options, but survival rates are modest and the tree has to be stored and watered. The calculator treats it as a very low annual footprint, roughly the transport plus a small share of the growing emissions.
Are the size multipliers exact?
No. A taller tree carries more biomass and often more plastic, and the two do not scale in the same way. The multipliers are a simple scaling of the two-metre reference; use the medium setting when you want the published figures exactly.