Carbon counter: how green is your tree?

As the Christmas spirit flows, so do squabbles over Scrabble and Trivial Pursuit. Eco-conscious households have another source of febrile, festive debates. Which Christmas tree is better for the environment: real or fake?

The answer might seem obvious. Real trees are grown over the course of a decade. During that time they convert carbon dioxide into biomass, acting as a carbon sink. They also provide habitats for animals. By contrast, artificial trees are usually made from PVC plastic and travel long distances from factories abroad. Those factors add a significant carbon load.

However, those averse to picking up pine needles need not despair. If an artificial tree gets enough use, its carbon count can fall below that of repeatedly buying real trees. That is evident from a life cycle analysis undertaken for the American Christmas Tree Association. This compared the carbon from factory or field to the home for the two types.

The average artificial tree made in China is responsible for the emission about 18kg of CO₂ equivalent all in. That is equal to about 0.2 per cent of average annual per capita emissions in high income countries. 

A real tree will suck up about 9kg of CO2e as it is grown. Once cut, road transportation adds about 3kg to the equation. That is based on the assumption that the tree travels 150 miles, including a five-mile round trip for the consumer.

Whether the tree ends up as a net emitter or absorber of carbon mostly depends on the method used eventually to dispose of it. If it is buried in a landfill site, the bulk of the carbon will remain locked underground. Composting or incineration results in a final net carbon cost of about 5kg. 

That means households need to use an artificial tree for at least four years to get a carbon edge over using real trees that are composted or burnt. A real tree that goes to landfill provides the most eco-bragging rights of all the options. But consumers may not have much choice over tree disposal methods. It may be that the best they can do is cut the distance they drive to collect it.