There is no need to ditch the bagged milk in the name of environmentalism yet. While glass is often preached as the more sustainable alternative to plastic, research by a student at Waterloo University found that bagged milk is usually the more eco-friendly option in terms of the packaging’s overall environmental impact compared with other options.
Alexander Cha, a graduate of the university’s Master of Environmental Studies in Sustainability Management program, saw an opportunity to explore how Canada’s packaging choices perform in the milk market.
“It’s an interesting topic, because it leads to the intersection between a lot of different packaging materials. So, you have reusable systems that include plastic. Mixed materials – what you see in the packaging board with carton – and I think it’s an interesting packaging type because it allows you to compare use through the different materials, and in some of the other sectors of packaging there’s maybe a little bit less diversity,” said Cha.
Cha’s research quantified the environmental impact of various milk packaging options being used in Canada, including paperboard cartons, plastic jugs, single-use and reusable glass bottles. He found that the production stage had the largest environmental impact.
“The 2025 kind of current year information between the single-use packaging, we do see that milk bags show the lowest impacts across the impact categories,” said Cha, adding that single-use glass had the highest environmental impact.
The higher impact is attributed to more greenhouse gas emissions and the energy-intensive sanitation required to process the material.
However, not all glass has the same carbon footprint.
“What we really see is between the different materials, depending on the situation; in the case of reusable glass, or single-use glass, you see some different results,” said Cha.
Under ideal reuse infrastructure, reusable glass bottles were shown to have a better environmental impact after several uses.
“The impact as you continue to reuse the glass up to around 25 reuses starts to become more optimal,” said Cha. He noted that reusing a glass bottle 25 times is the amount it takes to offset the footprint of sanitizing the glass and transporting it.
Factors such as the bottles travelling too far, not being reused enough times, or requiring too much energy and water to clean all contribute to the overall environmental impact of reusable glass.
Finding that people shouldn’t ditch bagged milk in favour of glass for environmental reasons might be surprising, as plastic is usually seen as the worst material. However, Cha’s research shows the nuances in Canada’s packaging industry. His findings support reducing packaging mass as an environmental solution rather than simply substituting one packaging material for another.
