Environmentally conscious consumers often ask me if a real Christmas tree or artificial tree is the most viable option. As a researcher of horticulture and forestry, I know that this issue is also a reflection on the Christmas tree industry, which is cautious about reducing the market share of artificial trees.
And they have good reason: Of the 48.5 million Christmas trees purchased by the Americans in 2017, 45% were artificial and this share is growing. Many factors can influence this option, but the bottom line is that both real and artificial Christmas trees have negligible environmental impacts. Which option "wins" in terms of carbon footprint depends solely on the assumptions about how much consumers would keep an artificial tree relative to how far they would drive each year to buy a real tree.
From sowing to wood
Many consumers believe that truly Christmas trees are collected from wild forest stands and that this process contributes to deforestation. In fact, the vast majority of Christmas trees are grown on farms for this explicit purpose.
In order to assess the overall impact of a Christmas tree, researchers use a method called the Life Cycle Assessment to develop a record of the inputs and outputs required for their production, use and disposal. For natural Christmas trees, this covers everything from planting nurseries to harvesting trees and making them available, including using equipment, fertilizers and pesticides, and drinking water for irrigation.
Life cycle estimates will often also assess the carbon footprint of a system. Fuel use is the biggest source of greenhouse gas emissions for Christmas tree production. Using 1 gallon of gas or diesel to feed a tractor or truck sends carbon dioxide to 20 to 22 kilograms of carbon dioxide in the atmosphere.
On the positive side, Christmas trees absorb and store carbon from the atmosphere as they grow, which contributes to offsetting emissions from activities. Carbon represents about 50 percent of the dry weight of wood in a tree at harvest. According to recent estimates, coniferous Christmas trees store about 20 pounds of carbon dioxide in their tissues above the ground and probably store similar amounts underground at their roots.
However, using 1 gallon of gasoline produces about the same amount of carbon dioxide, so if a family drives 10 miles each way to get their real tree, they probably have already compensated for the coal that was isolated from the tree. Buying a tree closer to home or a tree during your daily move can reduce or eliminate this impact.
And natural trees have other effects. In 2009, Scientific American has specifically stolen the Christmas tree industry for the washing of greenery because the farmers' press releases ranged on the absorption of carbon from Christmas tree plantations while ignoring the use of pesticides and carbon dioxide emissions from plant management,
Is it better synthetic?
Artificial trees have a different set of impacts. Though many people think that trees from factories in China consume a lot of energy, shipping is in fact very efficient. The greatest use of energy in artificial trees is in construction.
The production of polyvinyl chloride and of the metals used for the production of artificial trees creates greenhouse gas emissions and other pollutants. China is working to reduce pollution from its chemical industry, but this can lead to the prices of these materials and the products made from them.
In addition, to look at sustainability from a broader perspective, the production of real Christmas trees supports local communities and economies in the United States, while the artificial tree market mainly supports manufacturers in China.
Going to the head
Recently, the American Christmas Tree Association, which represents artificial tree producers, commissioned a life cycle assessment to compare real and artificial Christmas trees. The analysis looked at the environmental aspects of sustainability but did not address the social or economic impacts.
The report concluded that the environmental point of "balance" between a real Christmas tree and an artificial tree was 4.7 years. In other words, consumers should keep artificial trees for five years to offset the environmental impact of buying a real tree every year.
A major disadvantage of this analysis was that it ignored the contribution of tree roots – which farmers usually leave in the soil after harvesting – in the storage of coal. This omission could have a significant impact on the recovery analysis, as the increase in soil organic matter by only one percent could withhold 11,600 lb. of carbon per acre.
Reuse or recycle your tree
Consumers can not influence the way farmers grow their live trees or how producers produce artificial versions but can control what happens after Christmas on the trees they buy. For artificial trees, this means reusing them as many times as possible. For natural trees, it means recycling.
This is necessary to optimize the carbon footprint of a real tree. Sanding used Christmas trees and using them for sauce returns organic matter to the ground and can help build coal in the ground Many sections of public works across the United States collect ordinary and use christmas trees after a break. If local tree recycling is not available, the trees can be thrown out and added to the composting piles. They can also be placed in yards or lakes to provide bird or fish habitats.
Instead, if a used tree falls into fire, all of its carbon content returns immediately to the air as carbon dioxide. This also applies to tree asparagus. And if used trees are placed in landfills, their carbon content will eventually return to the atmosphere as methane due to the destruction of the materials buried in landfills. Methane is a greenhouse gas 21 times more powerful than carbon dioxide for a century, so this is the most environmentally harmful way of discarding a used tree.
All factors affect choices for Christmas trees, from fresh tree aroma to family traditions, travel plans and the desire to support farmers or buy locally. Regardless of your choice, the key to relieving environmental stress plans to reuse or recycle your tree. Then you can focus on the gifts to put them under it.
Bert Cregg is Professor of Horticulture and Forestry at the University of Michigan. This article was originally introduced in The Conversation.