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What is the carbon footprint for both cardboard boxes (single and double wall) as well as plastic storage boxes (polypropylene plastic - virgin and recycled), and what are the environmental pros and cons of using each?
Hello, and thank you for your request for the carbon footprint of cardboard and plastic boxes. The most helpful sources for this project are TimeForChange.org and Green Ration Book. In short, we looked for information on the carbon footprint, or the amount of greenhouse gasses produced, in the production of both single and double walled cardboard boxes as well as virgin and recycled polypropylene plastic. We found that the carbon footprint of cardboard is 3.31 tonnes per tonne of cardboard. Polypropylene has a carbon footprint of 3.456 metric tonnes CO2eg per tonne.
Below you'll find a deep dive of the research, some additional helpful findings on the carbon footprint of different types of plastics, and some of the pros and cons of each material.
CARBON FOOTPRINT OF CARDBOARD BOXES
The Green Ration Book reports that the carbon footprint of cardboard is "3.31 tonnes Co2e per tonne of cardboard."
There is no specific reporting on the carbon footprint of cardboard based on single wall versus double wall status. Instead, the carbon footprint is measured by weight. Double walled boxes are stronger, therefore they are heavier and require more raw materials. Based on these facts, we can assume that they have a larger carbon footprint than will single wall boxes.
CARBON FOOTPRINT OF PLASTIC BOXES
According to AZO CleanTech, "polypropylene is a polymer plastic that...[is] a highly versatile material that has many beneficial physical properties, and most importantly it is also recyclable." They go on to say that most recycled polypropylene (or PP) products are made up of a blend of "‘virgin’ plastic (i.e. plastic that has not been produced via recycling) in a ratio of around 1:3 to produce new plastic products."
AZO CleanTech reports that "a main benefit of recycling PP is the reduction in the consumption of raw, finite resources, such as oil and propene gas. It is estimated that around 8% of the oil used worldwide around 400 million tons) is implemented in the traditional methods of plastic production with 4% as ‘feedstock’ and another 4% in manufacturing." The article goes on to say that recycling plastic to make other plastic products provides an "88% reduction in energy usage".
One challenge in determining PP's carbon footprint is that according to a 2011 IHS Markit study, "a diversity of manufacturing routes leads to a diversity of carbon footprints for the product that range by almost a factor of six." The study was able to determine that bio-propylene, which is made from vegetable oil, has "a much higher production footprint than its fossil counterpart." That being said, an Intertek study (also from 2011), reports that PP's total carbon footprint is 3,456kg CO2 eg per tonne, or 3.456 tonnes CO2eg per tonne. They did not differentiate between virgin and recycled materials.
There is a significant number of studies on polyethylene plastic, they primary material in plastic bags, bottles and food packaging. TimeForChange.org reports that the carbon footprint of polyethylene (also known of LDPE or PET) is "about 6 kg CO2 per kg of plastic." The Intertek study noted above claims PET has a significantly higher carbon footprint than PP. The study found that PET had a total carbon footprint of 4,523 KG CO2 eg per tonne (or 4.523 metric tonnes CO2eg).
When looking at the raw data, it is easy to think that cardboard would have the lower carbon footprint. However when you consider that these data points are based on weight, the lightweight plastics likely are better for the environment. The University of Oregon's Chemical Professor David Tyler says plastic bags "produce less greenhouse gas, they use less water and they use far fewer chemicals compared to paper or cotton. The carbon footprint...is less than that of a paper bag or a cotton tote bag."
The carbon footprint of 85% recycled polyethylene terephthalate (PET) trays has been calculated by Science for Environment Policy as 1.54kg Co2e for 1kg of trays. The report says, "the greatest proportion of greenhouse gas emissions of any life-cycle stage (45%) were attributed to the supply of the raw material (15% virgin PET and 85% recycled PET). The results indicate that if trays were made of 100% recycled materials, carbon footprint would be reduced by 24%."
Riverford Organics, a UK vegetable box producer, told the Guardian in 2010 that it had plans to switch from cardboard to plastic boxes because it "could reduce the carbon footprint of the company's packaging by 70%."
PROS AND CONS
Cardboard, which is essentially layers of paper glued together, needs land to grow its primary source material - trees. Green Ration Book reports that 1 tonne of cardboard "requires
The Guardian reported back in 2010, that "when considered over the entire life of the packaging, paper and cardboard embody far more greenhouse gases than their plastic equivalents." This is in large part due to the amount of energy required to make a paper product versus that needed for a plastic one. Additionally, the article goes on to report that unlike plastic, "any paper and cardboard products...end up in local authority landfill, where they rot down anaerobically, creating the greenhouse gas methane in the process." While this Guardian source is older than Wonder usually likes to present, the information presented is still highly applicable to your question.
The University of Oregon's David Tyler says that plastic bags are the greener choice as compared to paper. He tells the University's Cascade Magazine, "paper is just typically considered a fairly polluting industry. Whereas the petroleum industry, where we get our plastics, doesn’t waste anything. Chemists have had sixty to seventy years to make the production of plastics fairly efficient and so typically there is not a lot of waste in the petroleum industry."
CONCLUSION
To sum it up, the carbon footprint of cardboard is 3.31 tonnes per tonne of cardboard. Polypropylene has a carbon footprint of 3.456 metric tonnes CO2eg per tonne. Experts agree that plastics are better for the environment than cardboard or paper products.
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