Traditionally, Germans liked their mineral water strongly sparkling and out of refillable glass bottles, unlike most other countries in Europe and around the world where most people have been drinking uncarbonated water out of disposable plastic bottles for a very long time.
Yet, consumer attitudes in Germany have changed over the past decade. Though the preference for gassy water has remained (about 90  % of mineral waters sold in Germany are sparkling), consumers have increasingly chosen to replace glass bottles by the much lighter and unbreakable PET bottles. Their market share for mineral waters has more than doubled since 2002 from 41  % to 83  % in 2009. This share is further split into refillable PET bottles (currently about 15  % of the total market share) that were introduced to the German market in the early 1990's and disposable bottles (about 68  %) that only started about 10 years ago.

Continuous Market Growth of Disposable PET Bottles
One-way bottles are still experiencing a constant market growth despite the fact that a mandatory deposit system was imposed by the German government in 2003 for environmental reasons. This deposit system was meant to stop the continuous growth of non-refillable bottles, as well as to reduce littering and increase recycling rates. Each disposable bottle is since charged with a deposit of €0,25 that gets refunded to the consumer when he brings the bottle back to the shop. Although the deposit could not prevent the further growth of disposable bottles, it considerably helped improving their environmental performance, leading to a return rate of bottles estimated at 98.5  % and providing a fairly clean and homogenous PET fraction sought after by the PET recycling industry.
Probably no other product on the German market has been analysed as intensely as beverage containers from an environmental point of view. In 2000 and 2002, shortly after the market appearance of disposable PET bottles, the German Federal Environment Agency (UBA) decided to conduct an environmental life cycle assessment on beverage containers. This was followed by a life cycle assessment by PETCORE in 2004 and another one by GDB ((Association of German Wells (Genossenschaft Deutscher Brunnen)) in 2008, to mention only a few but important studies.
Luckily, refillable PET bottles soon proved to be of a high environmental performance. Especially due to their light weight which saves fuel consumption during transport they even outperform refillable glass bottles. However, one-way PET bottles were clearly lagging behind the refillable systems, both PET and glass, that have the ecological advantage of being reused about 15 times in case of PET bottles and even much more often in the case of glass bottles.

Paradigm Change
Yet, a current life cycle assessment performed by the Ifeu Institute for Energy and Environmental Research Heidelberg for IK, the German Association for Plastics Packagings and Films, shows a different picture. By now, 81.3  % of the researched market of mineral waters and carbonated soft drinks show an ecological equivalence with the benchmark refillable glass bottles (Fig. 1). This constitutes a paradigm change in the formerly black-and-white debate since generalised judgements despising disposable PET bottles are not valid anymore under the current market circumstances in Germany.
Four market segments were under review: carbonated water and soft drinks on the one hand and natural water on the other hand, with both markets further split into a "home storage" segment consisting of larger bottles (0.7 l and above) and a "convenience" segment of smaller bottles (less than 0.7 l ) as typically consumed to go. (Fig. 1). In all four segments the refillable PET bottles still proved to be the most favourable containers from an environmental point of view. Yet, the disposable 1.5 l PET bottle for carbonated water and soft drinks improved that much that it has caught up with the refillable glass bottle in the most important market segment.
In fact, the ecological performance of disposable PET bottles is a result of many factors along the bottle's life cycle, e.g. design of the bottle (especially weight and content of recycled PET), energy efficiency of the bottle manufacturing and filling processes, distribution distances as well as waste collection and treatment systems. Recent important investments of the industry into new machinery equipment and continuous efforts on bottle design have led to strong improvements, especially of the 1.5 l bottle for carbonated water and soft drinks. A bottle weight of 33 g with 25  % recycled PET nowadays constitutes the market average. The beverage industry herewith reveals how cost driven improvements and scales of economy can create win-win situations for the environment.
The Ifeu research institute, who also carried out the above mentioned earlier studies, applied a consistent methodology to allow for comparison with previous study results. Compared to the GDB study from 2008 the performance of the disposable 1.5l PET bottle improved by 31 to 55  % with regard to climate change as the most relevant impact category as well as regarding to fossil fuel consumption, summer smog, acidification, terrestrial eutrophication and respirable dust (PM10) (Tab. 2).

Continuous Improvement
Most important for the PET bottle industry is now to further drive the improvements, especially in those markets where no ecological equivalence of refillable systems has yet been achieved, like in the natural water segment. Joint efforts along the supply chain, from machinery producers to retail, will be necessary e.g. to secure and further increase the contents of recycled material. But political decisions are also crucial factors to keep the deposit and collection systems alive in determining the future ecological performance of disposable PET bottles.