Material Marvels – The lifecycle of the Christmas tree

Materials World magazine
,
27 Nov 2019

The Christmas tree has become a symbol of holiday festivities, but concerns over the impact they have on the environment are growing. Shardell Joseph looks into the history of the tree, and compares the lifecycles of modern materials.

The Christmas tree has surpassed its religious origins to become a essential decoration for many people worldwide. In the UK, 90% of the population will put up a Christmas tree each year. In the USA 56.4 million Christmas trees were bought in 2018 alone.

With the advent of artificial trees and their increasing popularity, for the benefits of being low cost and longer lasting, growing concerns have emerged over their impact on the environment. Parallel to these concerns, there has been greater academic interest in comparing the natural and the artificial tree, prompting research groups to conduct lifecycle assessments (LCA).

‘Their comparative environmental impacts are often a popular topic of discussion around Christmas time, with the common assumption being that real trees are probably better for the environment but artificial ones are lower maintenance,’ University of Bath Department of Mechanical Engineering Lecturer, Sophie Parsons CEng CEnv MIMMM, told Materials World.

Emergence of the artificial tree

The first written record of a decorated Christmas tree dates back to 1510 in Riga, Latvia. It was danced around by local merchants before being set alight. Although there have been records of Christmas trees elsewhere since then, for example in France, the tradition had taken root in Germany by the 17th Century, where they often decorated them with apples. German settlers introduced the Christmas tree to the USA in the 1800s, where commercialisation started in 1851. Parallel to this, the tradition was taken up in the UK in 1848 after London Illustrated News published a sketch of Queen Victoria's family dressing a tree, due to Prince Albert, which was soon emulated by the public.

While other parts of the world were gradually starting to decorate pine, spruce and firs, Germany had begun constructing artificial trees, the first example of which was created the German Moravian Church. In 1880, artificial trees were widely seen across Germany, as a convenient alternative to natural trees and to combat the problem of deforestation. These fake trees were produced using real goose feathers, which were dyed green, split, secured by wires and then attached to dowels which made up the roots. These goose feather trees were a hit, and soon spread throughout Europe.

The UK was next to commercialise the artificial tree in the early 1900s, when the Addis Brush Company created a much sturdier version. Famous for producing the first toilet brush, the company used the same bristles, dying them green, to create the leaves – able to hold significantly more weight than goose feathers.

For a short period of time in the 1960s, the aluminium tree was prevalent, specifically in the USA, due to its shiny silver aesthetic. The quick decline of aluminium trees has often been credited to comic book strip A Charlie Brown Christmas in 1965, where the characters openly mocked the tree and chose a natural one instead.

Dominating the artificial trees market, since its emergence in the 1980s is the plastic tree. The first and most commonly used plastic for trees is polyvinylchloride (PVC), due to the material’s flexibility and durability. The PVC is compressed and cut into tiny, flat strips, which are then affixed to the branches, giving it a lifelike appearance due to movement of the bristles. Polyethylene (PE), however, has also been used in the production of trees in recent years for a more realistic look. The PE needles are more three-dimensional, and the branches moulded so they seem like real wood. The needles do not bend as easily as the PVC, but are softer to touch.

The lifecycle

With its realistic aesthetic, light weight and mess-free qualities and easy assembly, plastic has become the preferred choice for artificial trees and is a strong rival of natural trees. In the USA, 42% of the 56.4 million trees bought in 2018 were artificial, but it has become a much debated topic on whether real or fake trees have lower environmental impact.

Two studies have been conducted that addressed the environmental issues of a Christmas tree - Life cycle assessment: comparative LCA of the environmental impacts of real Christmas and artificial trees, conducted by Wrap UK published in 2018, and Comparative life cycle assessment of an artificial tree and a natural tree, conducted by Thinkstep and published in 2010. Parsons analysed the two studies to provide greater insight into the Christmas tree’s LCA, highlighting the importance of assessing their whole life impact and recognising ways in which consumers can lessen that.

‘LCA studies are often used in the hope of definitively confirming one product or material is environmentally preferable than the other, but as these Christmas tree LCAs show, environmental impact more often than not comes down to “it depends”’, said Parsons.

‘This means that LCA information may need to be taken on a case-by-case basis, or that multiple scenarios and sensitivities need to be investigated in order to understand the nuances of environmental impact relating to products or services under different conditions or assumptions.

‘This is not just important point to think about when making Christmas tree choices, but is increasingly significant as LCA is used widely in policy-making or reporting in the media. This is particularly pertinent across the materials and extractives industries – from plastics and recycling to the role of materials in new technology.’

Production

According to the studies, the biggest contribution to global warming potential (GWP) from an artificial tree is its manufacture. The modern artificial Christmas tree consists of composed steel sheets, PVC and polypropylene (PP). The 2018 study lists the series of processing stages the raw materials undergo to complete the tree, including the components of branches, tree pole, tree stand and tree top insert, metal hinges and metal fasteners.

The processes included are:

  • Cutting the PVC
  • Combining PVC with steel wire for the branches
  • Production of PP yarn and attachment to the tip of branches
  • Steel sheet rolling and cutting
  • Powder coating metal sheets using epoxy resin to form tree poles
  • Injection of moulding PVC resin to form the stand and tree top insert
  • Stamp pressing and powder coating epoxy resin to form metal hinges
  • Stamp pressing steel sheets to form metal fasteners, and
  • Christmas tree packaging consisting of corrugated cardboard boxes sealed with plastic tape.

Assuming the bulk of manufacturing is in China, at 80%, Parsons highlighted the contributions of the production process on the environment globally. ‘PVC resin for the production of tree branches alone contributes 25% GWP impact. Raw materials contribute the majority of environmental impact for GWP, eutrophication, and use of non-renewable energy.’

Transportation

Another key contributor recognised by both studies is the transportation associated with both artificial and natural trees. To analyse the vehicle and fuel usage in the USA for transportation, Thinsktep used its GaBi database as a model, as reported in the 2010 study. The transportation of the artificial tree from China to the USA was modelled using a global truck – factory to port – and a container ship – Chinese to USA port. All truck transportation for within the USA, for natural trees, was modelled using the GaBi US truck transportation datasets.

‘Transportation contributes most to acidification, and impact from smog. For real Christmas trees, eutrophication and acidification potential, primary energy demand, and smog impact is greatest during cultivation. However, end-of-life options dictate GWP,’ Parsons said.

‘While often GWP is taken as the major environmental impact category of concern, the differences in environmental hotspots across different impact categories are what often makes comparative LCA studies difficult to decipher to make a clear choice, or clear strategy, where focus on lifecycle stage impact reduction should be.’

End-of-life

Disposal of artificial and natural trees was assessed by both the 2010 and 2018 LCA studies, looking at potential scenarios for end-of-life and their impacts. Parsons explained that the studies found that landfilling real trees was always preferable in terms of GWP, ‘whereas this was not always the case for municipal composting or incineration scenarios, which had break-evens of three to four years’.

The worst case scenario for the artificial tree is that it is landfilled at its end-of-life, however, it is assumed that all intermediate waste is sent to material-specific facilities and all landfill processes have energy recovery from methane production. It is also assumed that PVC steel artificial tree production waste streams in China are recycled.

For real trees, the scenarios for end-of-life that are considered are landfilling, incineration and composting.

The choice made of end-of-life for real Christmas trees can greatly affect the amount of carbon released and sequestered.

‘These differences relate to assumptions made around sequestration of carbon in USA landfill sites rather than energy credits from on-site energy generation,’ Parsons said. ‘This means that, if I landfill a real Christmas tree, my carbon footprint will always be lower than owning an artificial tree, but it will also always be lower than composting or incinerating it.’

Consumer impact

Another assumption made by the studies is that most people will not purchase an artificial tree and use it for only one year. It was demonstrated that if a customer purchases an artificial tree and used it for at least 4.7 years, versus purchasing the equivalent (4.7) real Christmas trees, the environmental burden shifts and the artificial tree would have a lower environmental impact.

Taking this into consideration, the results of the 2018 study showed that the choices made by the consumer are a significant contributor to the impacts of all Christmas trees. For the real Christmas tree customer, disposal of the tree is a major contributor to its impact. For the artificial Christmas tree purchaser, the length of use is the primary contributor to its overall impact.

According to the American Christmas Tree Association, studies have shown that most artificial Christmas trees are used for an average of 10 years – more than meeting the LCA’s recommendation of five or more. ACTA expressed that the purpose of conducting LCAs is to provide consumers with a comprehensive look at the environmental impacts of both types of Christmas trees so they can make an informed purchase.

Parsons reflected on the LCA of Christmas trees and consumer behaviour, concluding that ‘the environmental impact associated with artificial Christmas trees can be reduced by owning the tree longer and donating it to charity when looking to upgrade. For real trees, consumers can think about transport distances when purchasing a tree – choosing to purchase from a local tree farm for example. They can also think about using the tree in other applications, garden mulch etc., or replanting it.’

When choosing your decorations this year, remember, a tree is for Christmas, not for life.