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How and when to switch from plastic to re-usable glass milk bottles

Earlier this year, a team at Zero Waste Scotland’s head office in Stirling (at least, the tea and coffee drinkers in the office) switched from using single-use plastic milk bottles, to re-usable glass ones. The change is one of many initiatives the organisation has implemented to minimise the office’s environmental impact.

If you are considering making the switch to re-usable glass milk bottles, we thought sharing the lessons that Zero Waste Scotland has learned would save you some time and effort – your day job no doubt keeps you busy enough after all.

So, we sat down with Zero Waste Scotland’s Environmental Policy Advisor, Michael Lenaghan, to find out more. We started by asking an important question: ‘Is switching to glass milk bottles actually more sustainable?’


Is switching to glass milk bottles actually more sustainable?

That’s a good question. The very first thing we did was to determine whether re-usable glass milk bottles are, in fact, more sustainable than single-use plastic ones.

We did some research and found a great 2010 report from our friends at WRAP that gave us two key things to consider before making the switch.

The first was around the energy used in washing, rinsing and refilling re-usable glass bottles. In 2010, WRAP found this responsible for up to 25% of glass bottle impacts. However, given the growth in renewable energy generation, the UK energy grid has decarbonised by 50% since 2010 and these impacts will now be much lower. This has improved the carbon competitiveness of glass and makes the switch to re-usable milk bottles a sustainable option.

The second consideration, and a critical one for any businesses thinking of making the switch, relates to how many times a glass bottle is re-used. The WRAP report indicated e-usable glass milk bottles had to be re-used at least 20 times to have a lower carbon footprint than single-use plastic (though this figure is probably lower today thanks to the reduced washing impacts mentioned above).

We contacted our milk supplier who confirmed the average re-use rate was more than 20 times. That was great news and a green light for us to proceed.

I would recommend anyone thinking of making the switch speak to their supplier to make sure their glass bottles are going to be re-used at least 20 times on average.


How did you find and choose a supplier?

We were fortunate our existing milk supplier had recently started offering glass bottle delivery. However, we still did some shopping around – it’s a positive sign that many suppliers now offer glass bottle deliveries, and this gives businesses a good opportunity to shop around and find the best deal. And it’s not always about choosing the cheapest.

For example, while we did find one supplier that was slightly cheaper, we decided to stick with our existing supplier as it is located nearby, meaning there would be lower transport emissions associated with our milk delivery. The company is also a living wage employer.


Did you involve your colleagues?

Yes, absolutely. Making any change is easiest when you involve the people that will be most affected as early as possible.

We identified our Facilities Team as a key stakeholder group. Team members had expressed concerns that a re-usable bottle system might mean extra work for them. And, in my experience, nobody is keen to take on extra work unless they can see some value in it and feel rewarded for their effort. So, we involved our Facilities Team in our planning and decision making. We also set up and ran a trial period which they were involved in. Their input proved highly valuable.

We also prepared a short presentation describing the change and its environmental benefits. We presented it first to senior management and then to all staff during team meetings. We made it clear that we would trial the system for 3 months and encouraged all staff to provide feedback. At the end of the trial, we had widespread support from across the organisation.

I would encourage businesses planning to make the switch to make sure they get their colleagues on board early in this way.

Likewise, once you’ve made or are trialling the switch, remember to share news on how successful the change has been. For example, let your colleagues know how many single-use plastic milk bottles your business has stopped using. This will help you secure their support for the long term.

What other factors should businesses consider when making the switch?

There are three features of plastic milk bottles that re-usable glass bottles don’t have – sealed screw tops, large sizes and use-by dates. This means there a few things that businesses will probably need to do when making the switch.

First, arrange your fridge. Most businesses will be used to having two or three 2-litre plastic milk bottles in their fridge at a time (each bottle probably lying on the bottom shelf until it is opened and then tucked inside the fridge door when it is).

However, standard glass milk bottles are smaller at 1 pint (568ml), and have foil lids, so they need to be stored vertically. So, the first thing to do is adjust your fridge shelving to ensure you have adequate space for your re-usable milk bottles to be stored.

Second, mark your bottles – and use the oldest ones first. Because re-usable glass bottles don’t have a use-by date on them, you won’t automatically be able tell which milk in your fridge is the oldest and should be used first.

Our solution is to mark bottles when they come in (we mark bottles with the initial of the delivery day [e.g. ‘M’ for Monday], using a liquid chalk pen). We also place newer bottles behind the older bottles, with the chalk letters facing forward. This helps us ensure that the ‘F’ bottles are finished before any ‘M’ bottles are opened, reducing the chance milk will go off and to waste.

Third, recycle your foil lids. The foil lids on glass milk bottles can be recycled, so we put a jar beside the fridge to collect them. (You might also find the foil lids hard to re-use once opened; we ordered re-usable silicon lids which are easy to find online).


Would you encourage other businesses to make the switch?

Yes, I would – providing they can find a supplier that re-uses glass bottles at least 20 times on average.

We’re nearly a year on from making the switch and our re-usable glass bottle system has been a great success. Not only have we eliminated hundreds of single-use plastic milk bottles, we’ve also reduced milk waste, thanks to our improved stock management system. Today, we buy and waste less milk despite overall staff growth.


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