Although the carbon footprint of a real tree depends on the method of its disposal, it is invariably lower than that of an artificial tree. According to the Carbon Trust, a 2m tall real tree that ends up in a wood chipper or bonfire has a carbon footprint of 3.5kg of carbon dioxide (CO2). If the tree ends up as landfill, the footprint increases significantly to 16kg CO2.
Both of these figures pale in comparison to the carbon footprint of a 2m-tall artificial tree, which is estimated to be 40kg of CO2. This means you would have to reuse your artificial tree for 12 years to make it greener than a real tree that was burned. If you want to be environmentally friendly this Christmas, your best option would be to buy a potted tree which can be replanted and re-used year after year.