It is not, however, the first time McDonald's has tried to block such a move; the packaging tax was proposed in the German city of Kassel in the 1990s, but a McDonald's lawsuit overturned the attempt. However, Palmer is confident that Tübingen's packaging tax will prevail when the case is heard in March 2022. "We believe that a city has the right to frame such a tax, and then even a big company has to accept that. I can't believe why an international company can't switch to reusables if every small business can do that." This gives us hope that there might be a way to overcome global warming Palmer, who was appointed mayor in 2007, is credited by many for shaping Tübingen's green policies, such as obligatory solar photovoltaic systems on roofs and the free buses on Saturdays. "We have seen a reduction in the emission of carbon dioxide per capita by 40% in the last 15 years, while Tübingen's economy has grown by 40%," he said. "This gives us hope that there might be a way to overcome global warming and keep growing." While much can be learnt from Tübingen's model, perhaps it's hard to replicate the city's victories, as they emerge from a uniquely supportive social and political landscape. Some worry Tübingen runs the threat of going too far: a 2011 Spiegel article described the French Quarters, one of the greenest neighbourhoods in the city – and the country – as a "green hell", presenting its residents as intolerant and hypocritically green. Additionally, many feel that Tübingen is too academic to be considered a real-world example. "You will stay very much in the academic bubble if you live there," said Kathi Winkler, who lived in Tübingen for several years before moving to Berlin. Nevertheless, the example of Tübingen shows that paving the way for a greener planet can be achieved on a small scale, proving that small can be powerful, beautiful and inspirational. --- Join more than three million BBC Travel fans by liking us on Facebook, or follow us on Twitter and Instagram. If you liked this story, sign up for the weekly bbc.com features newsletter called "The Essential List". A handpicked selection of stories from BBC Future, Culture, Worklife and Travel, delivered to your inbox every Friday.