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The Environmental Cost of My Christmas Tree

2011-01-03

(From the ‘better-late-than-never’ department)

I have been aware of the Christmas tree debate about whether real or artificial trees are better for some time.  Just over 6 years ago, while living in Southern California, we purchased an artificial tree because it seemed like the right thing to do.  Real trees were expensive and most came from far away – some from as far away as New Brunswick in Eastern Canada.  We found a good quality artificial tree that we thought would last a long time and thought that we had made a better choice in terms of both price and effects on the environment.

Just before Christmas, I came across an environmental blog (Artificial Christmas Tree or Real?) comparing the environmental impacts of real and artificial Christmas trees. The conclusion of the article was that a real Christmas tree is more environmentally friendly than an artificial tree. However, the article was short on details and left me with many unanswered questions.

The cost benefit was pretty clear and we knew that, based on the cost of real trees, we would be ahead financial in only a few short years.  The environmental issue, however, is significantly more complex.  One part of the problem is that the concept of “environmentally friendly” is subjective and depends on what aspect of the environment is most important to a given person.  Is it greenhouse gas emissions and global warming?  Is it garbage and landfills?  Is it air and ground-water pollution from toxic chemicals and dioxins?  Is it issues surrounding land use, agriculture and ecosystem diversity?  Most likely it is some combination of all of these.  A second problem is that calculating the environmental effect can be very situation dependent and the ‘right’ answer can be different for different people.

This article tries to document my attempt at finding the ‘right’ answer for our tree.  I have chosen to initially focus on carbon footprint calculations as I consider global warming one of the more serious environmental problems facing humanity and because it was an issue for which I thought some form of objective measurement could be made.

I was able to find references to two studies, however, neither seemed to provide enough information for our particular situation nor were the details of the study’s methodologies available.

The first study, done by the sustainability firm PE Americas, was commissioned by the American Christmas Tree Association, or ACTA, (according to a Time article, they work with artificial tree manufacturers).  Their conclusion was that “a consumer using an average artificial Christmas tree has a significantly smaller carbon footprint than a consumer using average farm-grown Christmas trees.”  They assume 6-foot trees with the artificial tree lasting 10 years.  I have not seen a copy of the actual study and ACTA provides very few details about the methodology used to calculate their results.

The second study was performed by ellipsos, a consulting firm based out of Montreal (see also this Wikipedia article which references their report).  They claim a natural tree footprint of 3.1 kg CO2e per tree (assuming a 5 km trip to obtain the tree) while an artificial tree generates 8.1 kg CO2e per year over a period of 6 years which they give for the average lifetime of an artificial tree.  Like the PE Americas study, I have not seen the actual study so I cannot comment on the calculations or methodology.

This is my attempt to estimate of the carbon footprint of our artificial tree and of all the real trees that we did not acquire or that we are not going to acquire each year that we continue to use our tree.  As is commonly done, I will report the carbon footprint in units of kg CO2e (kilograms of CO2 equivalent).  The carbon footprint will be calculated by examining 3 main elements: production (manufacturing/growing), transportation and end-of-life disposal.

For our tree, some of the relevant information is as follows:  We have a 7-1/2 foot tree made by the National Tree Company (headquartered in New Jersey).  The tree was manufactured in China and has a gross weight of 28 kg and a net weight of 22 kg.  We purchased this tree just over 6 years ago while living in Simi Valley in Southern California.  In 2005, we moved to the Kingston area in eastern Ontario and in 2009 we moved to Coquitlam (near Vancouver) in British Columbia.  During the two long moves the tree travelled some 8000 km by truck.  So far the tree has spent 1 Christmas in LA, 4 in Kingston and 2 in Vancouver.  I assume that the tree will remain with us long enough to see its 20-th Christmas with (for lack of better information) the remaining 13 Christmases being spent at our current location.  We drive a Jetta TDI wagon that gets about 16 kilometers per liter of diesel.

Production Footprint

Our artificial tree shipped with a gross weight of 28 kg.  The actual tree has a net weight of 22 kg which is mostly steel with some plastic (mostly, I assume, PVC for the artificial foliage).  I will assume that the remainder of the gross weight is the corrugated cardboard box that it was shipped in and that we store the tree in between Christmas seasons.

According to the book “How Bad are Bananas” by Mike Berners-Lee, one kg of virgin steel has a carbon footprint of about 2.75 kg CO2e.  For recycled steel the value is only 0.42 kg CO2e.  This does not include the cost of getting the steel from the foundry to the manufacturing site or the cost of transforming it into the artificial tree.  Assuming that 20 kg are steel (and that these numbers apply to Chinese steel production), the steel in our tree has a footprint of 55 kg CO2e if made with virgin steel.  With all recycled steel this would drop to 8.4 kg CO2e.  Lacking exact data on the steel that went into my tree but knowing that worldwide demand is growing, I will assume a value of 40 kg CO2e which corresponds to about 2/3 virgin and 1/3 recycled steel content.  For the plastic, the article What’s the carbon footprint of your credit card? gives a value of 4.1 kg CO2e per kilogram of PVC produced.  Assuming roughly 2 kg of plastic in our tree, this adds 8 kg CO2e to the material production.  According to a life-cycle analysis of corrugated cardboard, the remaining 6 kg of packaging results in about 1 kg CO2e per kg of corrugated cardboard so the final footprint of the raw materials is about 54 kg CO2e.

I do not know how to accurately calculate the footprint for converting the steel, plastic and cardboard into the final tree packaged up and ready to ship.  I’ll just increase the manufacturing footprint by 50% to account for this.  My tree’s production footprint is now up to around 81 kg CO2e with significant uncertainty.

I have not been able to find any data for the farming part of a tree’s footprint.  The ellipsos study found a total real-tree footprint of 3.1 kg CO2e assuming purchasing 5 km from home.  Since the split between transportation and production was not specified in the article summary, I will simply assume an even split with a production footprint of 1.5 kg CO2e per tree.

Transportation Footprint

In order to calculate the transportation footprint I need to know how the tree gets from its point of manufacture to my door.  For my calculations I will use data from Greenhouse Gas Calculator Emission Factors from a CN Railway website.  For marine container shipping, rail and heavy truck transportation they use 11, 17.85 and 114 g CO2e/t-km (grams CO2-equivalent per metric-tonne per kilometer) respectively.

First, the marine portion of the trip.  I assume that my 28 kg tree travels directly from Hong Kong, a trip of almost 12,000 km by sea.  The emissions for this leg is about 3.7 kg CO2e.  I will add 2000 km of rail transport to cover transportation from manufacturer to the port for another 1.0 kg CO2e.  Once the tree arrives in LA it is not clear how it gets from ship to vendor.  If it ends up being shipped to a warehouse somewhere else in the US there could be a significant additional rail or truck shipping footprint getting it there and back to LA (remember, the manufacturing company is headquartered in New Jersey).  I’m going to assume that it stays reasonably close to LA and add another 4 kg CO2e which will allow for both heavy-truck and less efficient smaller truck transport around the LA area.  Where we lived in Simi Valley, the round-trip to the vendor to pick up the tree and bring it home was 18 km requiring about 1.1 liters of diesel in our Jetta.   A liter of diesel has a footprint of about 3.6 CO2e (2.7 kg is from the combustion and the rest is associated with extraction, refining and delivery – source: “How Bad are Bananas” by Mike Berners-Lee) resulting in a pickup footprint of 4.0 kg CO2e (note that this does not include any contribution from vehicle depreciation).  So far, the transportation footprint is about 12.7 kg CO2e.  For the 2 moves, I have an additional 8,000 km of heavy truck which adds an additional 25.5 kg CO2e to our tree’s footprint for a grand total to date of 38.2 kg CO2e.  Of course, this is amortized over the life of the tree so that the longer we keep the tree the better.

Now I need to estimate the transportation footprint that would have resulted if we had used a real tree every year.  In all cases I will assume a tree weighing 20 kg.  In the Los Angeles area, as previously mentioned, most of the real Christmas trees are shipped in from out-of-state.  According to an article on OregonLive.com, Oregon is the largest Christmas tree producing state with an expected 2010 harvest of almost 8 million trees.  80% of their harvest is exported and in 2009, half of their sales went to California.  Therefore, I will assume a tree shipped 1500 km from Oregon for my calculations.  Heavy truck transport will result in 3.4 kg CO2e.  Add 4.0 kg CO2e for the 18 km car trip and the footprint for a real tree is 7.4  kg CO2e.  After one year, we moved to the Kingston area where we spent two winters living in a rural area 30 km from town.  A 60 km round trip to pick up a tree means 3.75 liters of diesel resulting in 13.5 kg CO2e of emissions per year for those 2 years.  We then spent two more winters living in town where we could get a tree with a short 4 km round trip corresponding to 0.9 kg CO2e per year.  Ontario is a tree producing and exporting province so the tree supply will be closer.  I’ll use 1 kg CO2e for the transportation of the tree from farm to vendor assuming the tree was grown locally. 

Finally, the most recent 2 Christmases have been spent in Coquitlam which is in British Columbia, a province that also has a large tree-growing industry.  We do not need to go too far to find a tree so assuming 10 km round trip, the pickup footprint is 2.3 kg CO2e plus I’ll again assume a 1 kg CO2e farm-to-vendor cost.

Since there is a good chance that any of our tree pickup trips would have been combined with other activities requiring use of our vehicle, to make my tree-pickup calculations more accurate I will divide the pickup portion of all footprint values by 2.

Disposal Footprint

The disposal part of each footprint is small.  For the artificial tree this will likely be a large item pickup at the curb or a single trip to the dump.  I’ll assume 10 kg CO2e to get the tree to the dump.  For each real-tree, it will be pickup and delivery to a central location, the cost of chipping the tree into mulch and the cost of dealing with the resulting mulch.  I’ll assume 1 kg CO2e per tree.

Total Footprint

Now we can put the rough footprint estimates together.  My artificial tree has a manufacturing footprint of 81 kg CO2e and a transportation footprint of 38.2 kg CO2e for a total of 119.2 kg CO2e.  My estimate for the 20 real trees that we did not buy is about 30 kg CO2e for production and 76.1 kg CO2e for transportation for a total of 106.1 kg CO2e.  Per year, we are looking at:

 Artificial / real:  6.0 / 5.3 kg-CO2e/yr

Given the uncertainties in my calculations, the cost is pretty close to the same for both cases.

What If…

One problem that I have with the published studies that I have seen is that they are being used to try to provide a definitive answer to the issue of real vs artificial without any allowance for individual situations.  As I have discovered from my own analysis, the ‘right’ answer is heavily dependent on many factors many of which are unpredictable.  To demonstrate this, I’m going to extend my analysis to a number of plausible ‘what-if’ scenarios.

What if we had remained in Simi Valley for 20 years with our artificial tree?

Artificial / real: 4.7 / 7.9 kg-CO2e/yr

What if we had remained in Simi Valley 20 years and drove a pickup/SUV/minivan that got about 1/3 the gas mileage of our diesel Jetta (assuming dedicated tree pickup trip)?

Artificial / real: 5.1 / 17.9 kg-CO2e/yr

What if we had remained in rural Ontario for 19 years after moving from California (pickup still shared with other activities)?

Artificial / real: 5.3 / 10.2 kg-CO2e/yr

What if we had bought a smaller artificial tree weighing only 20% that of the actual one?

Artificial / real: 1.3 / 5.3 kg-CO2e/yr

What if we had gotten an artificial tree with built-in lights which failed this year so we decided to replace our tree next year (artificial tree lifetime drops to 7 years)?

Artificial / real: 17.0 / 6.5 kg-CO2e/yr

What if we lived in California and drove our truck/SUV/minivan (1/3 our Jetta mileage) 50 km each way to a local tree-farm where we cut our own tree (dedicated trip)?

Artificial / real: 5.1 / 69.0 kg-CO2e/yr

What if we didn’t have a tree or just decorated an existing house-plant?

No tree or houseplant: 0.0 kg-CO2e/yr

You get the picture.  For an artificial tree the carbon cost depends heavily on the manufacturing cost and how long you keep the tree.  For a real-tree the cost depends mostly on how you get the tree home.

Beyond the Carbon Footprint

The GHG emissions associated with the real and artificial trees are not the only relevant environmental issues.

One major argument against artificial trees is that they are usually made with PVC plastic which can be a source of lead in the environment (particularly with the older trees).  PVC is a cheap plastic that is easy to work with.  Lead is a common stabilizer used in the past that is used less commonly today.  There have also been issues with some of the plasticisers used in PVC production suggesting adverse health issues.

Besides the health issues, the PVC content and the way that the trees are constructed makes most artificial trees virtually impossible to recycle.  This means that the landfill is the main option (other than incineration) for the disposal of the typical artificial tree.  I looked at our tree to see if there was some easy way to separate the steel from the plastic.  Aside from the base, the plastic and steel are firmly connected and I can see no easy way of separating them.  The corrugated cardboard container will of course be recycled when it falls apart or is no longer needed.

The above comments on recycling begs the obvious question: “How hard would it be to make an artificial tree recyclable?”.  Designing an artificial tree that is made to last 20+ years and that is fully recyclable should not be complicated.  Being able to separate the metal from the rest of the material is a design issue that should be easy to resolve and there must be alternatives to PVC that don’t have the adverse environmental effects.  If the industry were told that in 5 years any tree that was not fully recyclable would be banned, I’ll bet that the industry could quickly come up with a better artificial tree.

I have one final bone to pick with the real-tree industry.  The real-tree growers would have you believe that their tree farms are environmentally friendly and support diverse eco-systems.  If my choice is between a tree-farm and a parking lot I definitely would choose the tree-farm.  If my choice is between a tree-farm and a field of corn, I probably would still choose the tree-farm.  However, if the choice is between a tree-farm and a natural forest, I would choose the forest as having the more diverse eco-system.  On the topic of diversity one reference states:

Christmas tree farms are havens for a wide variety of bird and mammal species including grosbeak, sparrows, chickadees, foxes, coyotes, mice, voles, and squirrels.

This is a little disingenuous since, according to a Wikipedia article, pine grosbeak, voles and squirrels only part of list of wildlife considered tree-farm pests.  Tree farms are a monoculture crop susceptible to many pests and diseases which farmers attempt to control through various means including the use of chemicals.  I cannot help but notice a certain amount of greenwashing on the part of the industry.

Beyond the environmental issues, the real-tree industry provides a large number of jobs to people in the tree-farming industry resulting, most likely, in a greater contribution to the North American economy.

Perspectives

The length of this article attests to the complexity of the issues.  If you are looking for the most environmentally friendly choice between a real and an artificial tree then you need to consider many factors.  A study published by a consulting firm may provide some guidelines as to what some of these factors are and how to handle them but it likely cannot provide the ‘right’ answer for your personal situation.

The Carbon Footprint of Nations site lists the 2001 per capita carbon footprint for the US as 29 t CO2e (for Canada the value is 20 t CO2e).  If we use the ellipsos value for the footprint of a real tree as 3.1 kg CO2e then for an American family of 4 this represents 0.000027 of their total annual footprint or just 14 minutes worth.  Using roughly one liter less gasoline during the year will compensate for these 3.1 kg of emissions.  Even the 8.1 kg CO2e for the ellipsos artificial tree would still only represent 37 minutes worth of the families annual footprint.

For another perspective compare the tree results with the carbon footprint of a single cheeseburger.  Mike Berners-Lee in “How Bad are Bananas” estimates the footprint of a 4-oz cheeseburger at 2.5 kg CO2e.  Another estimate by Jamais Cascio at openthefuture.com has a 130 g (4.6 oz) cheeseburger in the US having a footprint of between 3.6 and 6.1 kg CO2e.

In light of other sources of greenhouse gases, a Christmas tree hardly seems to count and can easily be compensated for by a few small sacrifices elsewhere over the year.  After all what you do every day has a bigger impact than a small extravagance once a year.

I would argue, however, that the Christmas tree is a symbol for unbridled consumption with little or no accounting of the associated environmental effects.  As I watch the economic news, the focus seems to be on the level of consumer spending and whether or not it is a sign that the economy is getting better or worse.  Imagine a news report discussing consumer spending and the rate of GHG emissions or garbage production.  By some estimates, in order to reach a sustainable world carbon footprints need to drop to 2 tonnes CO2e per capita per annum.  In that light, everything we do needs to be scrutinized in terms of its carbon footprint.  Perhaps the Christmas tree would make a good symbol around which such scrutiny might be focussed.  Perhaps we need other options besides real or artificial.

How about a living tree?  A Norfolk Pine, while not a traditional Christmas tree makes a nice permanent house plant that can be decorated.  Or choose a conifer that you use and then keep potted outdoors until the following year or plant it in the ground and get another next year.  There are also businesses offering trees for rent.  You use it and then the tree is returned either to be stored until the next year.  Just do the math – the production of these trees still has a carbon footprint and getting it from the nursery to your house and back, whether by you visiting the nursery or by delivery from the supplier can rack up a carbon footprint quickly.

Perhaps we need to consider something totally different – perhaps even a new tradition.

How about a piece of art depicting a tree and hanging on the wall.

How about a quilt depicting a tree or something meaningful during the holiday season.  Make it out of scraps of old material destined for the landfill.  Hang it on the wall.  Add loops of to attach your favourite tree decorations.  Include pockets for the few small gifts that you buy.  Travelling at Christmas?  Roll it up and take it with you.

End Note

The Environment Canada website has the following advice about Christmas trees:

While an artificial tree may automatically seem like the most ecological solution for the holiday season, the reality is more complicated.  In fact, a natural tree is a good alternative to take pride of place at the centre of your living room. However, if you already own an artificial tree, don’t hesitate to reuse it!

So, if we needed a tree next Christmas would I go real or artificial?  I don’t know and hopefully we won’t need to make such a choice for another 13 years or so.  It’s like answering the question: “Would you like paper or plastic?” in the grocery store line.  Sometimes the most satisfying answer is neither.

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