Comparing the carbon footprint of plastic and glass wine bottles
A few days ago, we wrote about our first encounter with plastic wine bottles with a 2008 Beaujolais Nouveau from Labouré-Roi. This winery thinks it’s understood that plastic wine bottles have a lower impact on the Earth than glass ones. But do they? That is, all aesthetic issues aside, is there a real environmental motivation to using plastic wine bottles – do they really reduce the carbon footprint of the wine they hold?
This question leads to more questions. How much carbon dioxide (CO2) is produced during the manufacturing of each? Clearly, plastic bottles weigh less than their glass counterparts and therefore generate less CO2 as they are transported, but how much less? And what about disposal? Are both glass and plastic wine bottles recyclable and, if so, how much CO2 does the recycling process produce? (And as always when recycling comes up, you must ask how likely the bottle is to actually be recycled.)
So when you take all these factors into account, can using plastic wine bottles really help you sleep better at night because you’re helping the Earth?
Three major components of the carbon footprint of plastic and glass wine bottles
As written in the questions above, there are three major components of a wine bottle’s carbon footprint (specifically, how much global-warming CO2 its existence releases into the atmosphere):
- (1) the manufacture each type of bottle
- (2) the transportation of the bottle from the manufacturer to the consumer, and
- (3) the disposal of the emptied wine bottle by the consumer
We’ll consider each component for the glass and plastic bottles in the three sections that follow.
The CO2 for (1) the manufacture each type of bottle
An Australian wine bottle manufacturer, Amcor, reports that it generates about 0.6 oz of CO2 per oz of glass wine bottles produced. A simple, empty wine bottle weighs about 23 oz, so about 13.8 oz of CO2 is generated for each glass wine bottle manufactured.
The US Environmental Protection Agency (USEPA) reports that the manufacture of plastic drink bottles generates 1 oz of CO2 per oz of plastic bottles. Even though a ton of plastic generates more CO2 than a ton of glass, a ton of plastic makes many more bottles since a plastic bottle weighs much less than a glass bottle. A typical plastic wine bottle is composed of Polyethylene Terephthalate (PET) and weighs approximately 1.9 oz, which means that manufacturing each plastic wine bottle generates about 1.9 oz of CO2 .
So for the manufacturing component of the carbon footprint, about 7.3 times more CO2 is generated by a glass wine bottle than a plastic one.
The CO2 for (2) the transportation of each type of bottle
The CO2 generated during transportation of the two types of wine bottles is directly related to the difference in weight between the glass and plastic wine bottles.
Assuming the wine in each bottle weighs the same, a filled glass wine bottle weighs approximately 48 oz, and a filled plastic bottle weighs about 27.3 oz — so the glass bottle weighs about 1.8 times more than the plastic one. The actual amount of CO2 generated depends on the distance the wine bottle is transported, but for the same distance, the glass bottle will generate 1.8 times as much CO2 as the plastic bottle.
The CO2 from (3) the disposal of the emptied wine bottle
What happens when the wine bottle is empty? In the U.S., we recycle about 22% of our plastic bottles and about 34% of our glass bottles. Unfortunately, recycled plastic is about 40% more expensive than brand new material, so there are not many folks buying recycled plastic to remake drink bottles.
There is a much greater demand for recycled glass. In the U.S., recycled glass accounts for about 25% of all glass on the market. Also, using recycled glass reduces the carbon footprint of the resulting bottle by about 25%.
Comparing the best case scenario for glass bottles, and the worst case for plastic ones
Since glass is often used in new wine bottles and plastic isn’t, let’s consider the most conservative but totally fictitious case where all glass bottles are made from 100% recycled glass, and all plastic bottles are burned to make electricity. We’ll ignore transportation since the glass bottle always produces 1.8 times the CO2 than the plastic one.
If all glass wine bottles were manufactured using 100% recycled glass, the carbon footprint for manufacturing would drop to about 10.4 oz of CO2 per bottle, still about 5.5 times as much as is generated when a plastic bottle is manufactured from virgin plastic.
To account for the fact that very little recycled plastic is used to make wine bottles, we assumed a worst case scenario that all of the plastic bottles are incinerated to generate electricity. While plastic wine bottles are an excellent source of combustion energy, burning the bottle releases CO2. Incinerating waste plastic wine bottles to generate electricity would add another 1.9 oz of CO2 per plastic bottle.
If we add this to the carbon footprint produced when plastic bottles are manufactured, we get a total CO2 emission for a plastic wine bottle of 3.8 oz per bottle compared to 10.4 oz for a glass bottle. This means that you can manufacture and dispose of about 2.7 plastic wine bottles for the same carbon footprint that you could manufacture and recycle 1 glass bottle.
So what’s the final answer?
Of course, there are lots of other issues with plastic bottles that we haven’t talked about, including possible contaminants in plastic, aging potential, general aesthetics, and the impact of extracting raw materials on aspects of the environment other than CO2 emission. However, when we are talking about the carbon footprint, plastic bottles clearly have a lower impact on the Earth.
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