Every year after the festive December season, the majority of Christmas trees ends up in landfills. But not in Vienna. Since 1990, every time right after Christmas, collection points open, so residents of Austria's capital city can bring their old Christmas trees (usually until mid January) and leave them there to support a common green cause.

Last year, Vienna gathered no less than 685 tons or about 157,000 old Christmas trees; since the first ever collection, 2.4 million trees were collected. The trees were thermally processed and converted into 1,700 MWh of pure energy, used to provide elctricity as well as heating. This way, enough clean energy was produced to supply 960 households with electricity and 2,200 households with central heating for an entire month.

To make the entire process more simple and efficient, the city of Vienna kindly asks all participating residents to remove all decoration, including tinsel, prior to setting the tree at the curbside for collection. Furthermore, a mobile app has also been developed, showing the collection points, nearest to the app user.