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    What exactly renders a returnable glass bottle for milk sustainable?

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    The most important variables influencing the sustainability of packaging, as exemplified by a new returnable-glass line for milk
    • Under the right conditions, the returnable glass bottle is a very sustainable packaging for milk.

    The Berchtesgadener Land dairy has been awarded the Reusable Systems Innovation Prize of the German environmental association Deutsche Umwelthilfe (DUH) and the Stiftung Initiative Mehrweg (SIM; Foundation for Reusable Systems) for its new Krones glass line. A welcome opportunity for us to take a look at the factors influencing the sustainability of packaging.

    “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.

    Milk in glass bottles is trending

    The glass bottle is the most commonly used returnable packaging for milk and practically the only one that is taken back. Consumers regard it as a sustainable container of a superior nature that protects top-quality fresh milk. And it has recently been making a comeback: In 2019, sales of milk in returnable glass bottles in Germany were up by about 30 per cent over the preceding year. But the overall reuse quota for containers of milk-based beverages, at about 1.3 per cent, is very low. That was not always the case: In 2015, the Institute for Energy and Environmental Research (ifeu) found that the proportion of returnable glass bottles for fresh milk had fallen by a good 90 per cent between 1995 and 2005. Demand for milk in returnable glass is now rising again. Berchtesgadener Land felt the full effect of this uptrend, which pushed the dairy’s old line to the limits of its capacity. With its new Krones filling line, the cooperative has doubled the output to 12,000 bottles per hour and is again able to respond in full to the demand of milk and cream fans.

    Krones consultancy service

    Krones offers beverage companies, in particular, a comprehensive energy and sustainability consultancy service, which also examines a packaging’s sustainability. Krones’ in-house experts specialised in the fields of recycling, product containers and product packaging work along the principles of eco-design and identify the most powerful levers customers have for choosing sustainable packaging and machinery. Analysis and classification of the packaging material concerned, advice on recycling systems for various types of plastic and on sustainable containers, including their design, and sustainable packaging machines are all part of Krones’ consultancy service. When designing a suitable container, the consultancy team joins forces with the customer to identify potential savings in resources, energy and material, and options for reducing CO2 emissions.

    Crucially important for a packaging’s life cycle assessment:
    cleaning, transport distances and number of use cycles

    The eco-design principles help customers decide which type of sustainable packaging to choose. Eco-design maps out all relevant facets along the supply chain, including production and weight of the containers, transport distances and transport fleet, the filling process consisting of cleaning, filling, labelling and packing, and also any additional outlay incurred for the system in question – in the case of returnables, this means sorting, storing and cleaning the bottles. When advising customers, the Krones specialists work along these principles and highlight the most powerful levers clients have for choosing suitable packaging and machinery.

    Life cycle assessments supply the data Krones needs to optimise its machines in regard to sustainability. “Our aim is to reduce a product’s cradle-to-grave footprint by scrutinising the most powerful levers able to achieve this. As far as returnable glass bottles for milk are concerned, a bottle washer with minimum energy and water consumption constitutes such a lever,” explains Martina Birk. Various life cycle assessments for beverage packaging, which explicitly examine milk in returnable glass, identify as crucially determinant factors the filling process (here the bottle washer in particular), transport and the number of use cycles, followed by bottle production and transport, and the production and handling of labels and closures, plus the outlay incurred for secondary packaging, meaning a crate for six one-litre bottles and a crate for 12 0.5-litre bottles respectively.

    Our aim is to reduce a product’s cradle-to-grave footprint by scrutinising the most powerful levers able to achieve this. As far as returnable glass bottles for milk are concerned, a bottle washer with minimum energy and water consumption constitutes such a lever. Erwin HächlMartina BirkHead of Sustainability at Krones


    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).

    Image 31060
    Water consumption of the new bottle washer Lavatec D4 has been reduced by 30 per cent and its caustic consumption by 15 per cent as compared to the predecessor model.


    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.

    Number of use cycles and returnable-bottle pools

    The number of use cycles (meaning how often a bottle can be refilled before it is replaced) exerts a significant influence on a container’s life cycle assessment. High rates of reuse reduce the amounts of energy and raw material needed to produce new bottles. Even though the impressive recycling quota for glass (about two thirds) means less raw material is needed, the amount of energy required still remains the same. The dairies cannot completely control how many times a bottle is reused. For example, a well-cared-for or a neglected returnable-bottle pool can have a positive or an adverse influence on the figures obtained. For milk, the Institute for Energy and Environmental Research (ifeu) stated a substantial pool deterioration in its 2015 life cycle assessment: Only seven out of the 23 dairies surveyed in 1995 still filled their products into returnable glass bottles in 2015. The sector has since been faced with a new challenge posed by companies whose bottles, processes and products filled, like nuts or muesli for example, do not comply with the relevant standards. The dairies reject such containers and have to buy new ones. The number of use cycles decreases, and energy and raw-materials consumption rises. Work to draw up a new guideline for the use of the returnable-milk-bottle pool started recently. So there is a prospect of further improvements in transport distances and reuse figures. Berchtesgadener Land estimates the number of turnarounds for its bottles to be ten to 15 – and has a chance of increasing that thanks to the revival of the returnable-milk-bottle pool.

    Important parameters for the sustainability of returnable glass bottles for milk

    • The right conditions: The market must have the appropriate infrastructure and an established culture of reuse.
    • Bottle washer efficiency: The bottle washer plays a far greater role in the life cycle assessment of milk bottles than it does for mineral water, for example. So it is all the more important to ensure low consumption figures for energy, water and cleaning agents.
    • Transport is likewise a major factor in the equation: Short transport distances and fuel-efficient vehicles and driving make for improvements in this part of the life cycle assessment.
    • Number of use cycles: The more often a bottle can be refilled, the better it is for its life cycle assessment. Using standard bottles increases the number of turnarounds.
    • Properly functioning returnable-bottle pools increase the number of use cycles and shorten transport distances.

    Returnable glass bottle for milk: in the case discussed here it’s a sustainable solution

    The returnable glass bottle is a sustainable solution for the Berchtesgadener Land dairy’s fresh milk, which is produced on environmentally compatible farms. Three factors make a major contribution here: the dairy’s focus on energy- and resource-efficiency by putting in place the requisite processes and equipment like the new returnable-glass line from Krones, using standard bottles and limiting the sales area for its products. It may well be that other companies looking for the most sustainable packaging find a different solution, depending on the specifics of each case. Krones’ specialists are able to assist customers here by examining the vast multiplicity of options, in order to find the best solution and translate it into hands-on reality.

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