What exactly renders a returnable glass bottle for milk sustainable?

“People frequently ask me whether there is the one sustainable packaging, and the answer is quite clearly no. You will always have to consider the overall system with all its facets, looking at a packaging’s entire life cycle,” says Martina Birk, Head of Sustainability at Krones. Beverage producers themselves can’t control all the factors here. Whereas they are able to manage their operations and choose their products and target markets, parameters like a proper infrastructure for taking back and/or recycling containers, legal stipulations or consumer wishes are outside their sphere of influence. So it all depends on the specific situation. Krones offers a consultancy service designed to advise its customers on everything to do with sustainability. The Krones crew also includes specialists who help clients choose the optimal container. This article discusses the most important influencing factors as exemplified by the new returnable-glass line for fresh milk and cream at the Berchtesgadener Land dairy.

Essential preconditions: an appropriate infrastructure and a fully embraced reuse culture

The packaging has to suit the market. There would be little acceptance of a returnable glass bottle in countries where all processes have been optimised for the recycling of PET bottles. In Germany, by contrast, consumers have got used to returnable containers, and the requisite processes and take-back systems are firmly established. And reuse is also backed by policymakers: The target specified in the EU Packaging Directive 2019 is to increase the reuse quota for beverage containers from 41 per cent to date to 70 per cent. The Berchtesgadener Land dairy sells its products in returnable glass bottles, mainly in southern Germany, and can build on a properly functioning returnable-container system there.

Cleaning

Used milk bottles contain difficult-to-dissolve fats and proteins. That is why the cleaning process required is much more elaborate than that for mineral water bottles, for example. The factors of crucial importance for life cycle assessment are the consumption figures for energy, water and cleaning agent per bottle. Under the principle of the Sinner Circle, named for chemist Herbert Sinner, who devised it, there are four mechanisms of action for every cleaning process: temperature, time, chemicals and mechanical power. In the new bottle washer installed at Berchtesgadener Land, the Krones Lavatec D4, these four parameters have been optimally harmonised with each other in order to create one of the most economical systems in terms of water and cleaning-agent consumption for washing milk bottles. The process relies on the time parameter, providing 16-minute bottle treatment. A special caustic filtration system reduces consumption of water and caustic. Firstly, the bottles’ dwell time in the caustic is long, and they are only sprayed with fresh water in the last rinsing bath. Secondly, the interval between caustic changes is longer. Compared with its predecessor model at Berchtesgadener Land, water consumption of the Lavatec D4 has been reduced by 30 per cent (230 to 300 millilitres, depending on the bottle being treated) and its caustic consumption by 15 per cent (150 to 170 litres per day).

Transport

As far as fresh milk in returnable glass is concerned, transport assumes a particular significance for two reasons: Firstly because the cold chain must never be interrupted, and secondly because the bottles weigh about 400 grams each, which means they are relatively heavy. That also shows up in fuel consumption when transporting the empties back to the dairy. Figures for this part of the life cycle assessment can be improved by increasing transport efficiency, optimising bottle weight and – as far as they exist – by returnable-bottle pools used by several vendors that fill their products into the same standard bottle. Milk in returnable glass bottles scores points above all when sales are restricted to a certain region.

The Berchtesgadener Land dairy keeps transport distances within limits because it sells its products only in southern Germany. Thanks to an in-house vehicle fleet, the cooperative is itself in charge of transport efficiency. Its nine 40-ton trucks use only 27 litres of fuel per 100 kilometres on average, which is a good 20 per cent less than the EU average of 33 litres (2017) stated by the ICCT (International Council on Clean Transportation). This low figure is achieved by regular driver trainings and by fitting the trucks with a cruise control for fuel-efficient driving called Predictive Powertrain Control. The cooperative fills its products into standard bottles, enabling it to use a bottle pool together with a few other vendors, something that cuts transport distances.