AskPablo: Pine or Plastic? The X-mas tree dilemma

x-mas tree.jpgTurkey day has come and gone, the Black Friday riots at the mall are over and X-mas 2006 is officially upon us. But this year we are faced with quite an ethical dilemma: Do we go to the forest and harvest our own Christmas tree or do we get a fake one?

Yes, they are obscenely tacky and don’t make your house smell like a coniferous forest but they won’t dry up and shed their needles all over the place before spontaneously combusting. And there’s the whole carbon sequestration issue… If you cut down a tree in the forest, you are taking away its ability to sequester carbon for many years to come. So, from the perspective of a world that already has more carbon dioxide than we know what to do with, which is better, a cut tree or a fake one?
Let’s start with the fake tree. I pick a model that is made in China, and weighs about 35 kg. The frame is made from steel and weighs about 25 kg. The remaining weight consists of small plastic parts made from high-density polyethylene, weighing about 3 kg, the “needles,” made from polyethylene foil and also weighing about 2 kg, and the pre-strung Christmas lights which consist of 2 kg of PVC, 2 kg of copper, and 1 kg of glass. Using the MIPS data tables provided by the Wuppertal Institute, I can determine that the amount of CO2 emissions from the extraction and production of the materials used is around 28.983 kg. Let’s add to this a 25% increase to take into account the manufacturing of the fully-assembled tree ( 28.98 kg + 7.25 kg = 36.23 kg). At 17 g/tkm, shipping 35 kg (0.035t) from China (10,000 km) is responsible for an additional 5950 g (5.95 kg) of CO2 emissions. So the estimated total CO2 emissions for the fake tree are 42.18 kg.
Now lets find out how many years you have to own this tree to justify the emissions from production compared to the carbon sequestration services provided by live trees. Well, it turns out that trees sequester somewhere around 172 kg (some as low as 36 kg, some as high as 342 kg) of CO2 per year. This would indicate that it is far more ecologically friendly to buy a fake Christmas tree once, at a CO2 cost of 42.18 kg, than to cut down a tree every year at a CO2 cost of 172 kg (annual for at least 25 years). Please note that this is not the amount of CO2 emitted by cutting the tree down, but the amount of CO2 not sequestered by the tree because it is now dead.
But wait, is there more to it? Well yes, there’s always more. Most Christmas trees are grown on tree farms and not in actual forests. These tree farms sequester CO2 constantly during the young trees’ period of vigorous growth. Since they were grown for eventual harvest, we are not actually decreasing the amount of CO2 sequestration capacity, but increasing it. What about other options? Well, I have a live Christmas tree in my room. The potted, live Christmas tree is a great alternative for many reasons. If you keep it properly watered it will not dry out, shed, and become a fire hazard. It will also continue to provide that pine-fresh scent throughout the holidays. But the best reason is that, when you are done with the tree, you need not kick it to the curb like your neighbors, but can plant it outside where it will provide carbon sequestration services for many Christmases to come.
Pablo Päster, MBA
Sustainability Engineer