© Emmanuel Pinto Compared to jugs and cartons, milk bags use 20 to 30 per cent less energy, and produce 20 to 40 per cent fewer greenhouse gases.
The study says "pillow pouches," as they're known in the industry, use less energy and water for production, transportation and disposal than plastic jugs or cartons, and also cause less greenhouse emissions.
Compared to jugs and cartons, bags use 20 to 30 per cent less energy, and produce 20 to 40 per cent fewer greenhouse gases.
They also use about two per cent of the water cartons require, and 40 per cent relative to jugs.
"Milk bags are far superior," Dalhouse chemistry professor Mary Anne White said. "Even if they're disposed in a landfill. Even if jugs, for example, are completely recycled."
Milk bags made out of thin polyethylene were popularized in Canada in the 1970s after the country converted to the metric system because it was easier to modify their volumes compared to cartons or jugs.
But according to a 2010 UN report cited in the study, the most popular milk container sold in North America is still the jug (68 per cent of sales), followed by carton (24 per cent). Bags only account for seven per cent of sales.
White said she hopes her study leads more Canadian companies to adopt milk bags, particularly in the West, where they're not as widely available as in Eastern Canada.
"Milk bags are not used at all west of Ontario," she said. "If Western Canada introduced milk bags, we would really be saving 5,000 tonnes of plastic annually. That's because we drink so much milk.
"In Canada, the average is over 60 litres per person. So that's really a lot of containers: It's up to 2 billion milk containers purchased every year."
But she said challenges to milk bag dominance remain. The biggest one is that unlike countries such as Germany, bagged milk in Canada only comes in large quantities. In most parts of the country, they're exclusively sold in four-litre quantities.
"If you only need one or two litres of milk, there's no point in buying four litres and letting the rest of it spoil because that's even worse in terms of the energy wasted and greenhouse gases emitted," White said.
© Wilfredo Lee/AP Milk jugs are the most popular container in North America for milk.
Chad Mann, the CEO of P.E.I.'s Amalgamated Dairies Limited, said bagged milk also makes sense business-wise, but that consumers have historically preferred other types of containers. Only 15 per cent of ADl's milk is sold in bags.
"The bags are the most economical way to package milk, so that would be the one we would push," he said. "But again the consumer and the retailer seem to be more predisposed to cartons and plastic jugs just for convenience."
But he said White makes a good point on the lack of bagged milk options for consumers who don't have large families and don't need much milk.
"A lot of our consumers now for ADL on the fluid side are between 50 and 75 and they're usually buying two litres to one litre," Mann said. "That makes a very good point. Will there be an option to sell one bag units to the consumer at some point in time? I thought that was very intriguing."
White said that while choosing which milk container to use may seem trivial, it's important for people to remember everyday items have an environmental footprint.
"Everything that we use takes energy, produces greenhouse gas emissions and consumes water," she said. "Milk containers are only a smart part of it, but what are the bigger impacts in our life and are there things we can change without significantly changing our quality of life?
"We want to preserve this planet ... and we all have to think about this."