Any environmentally conscious individual will know the best way to lower your impact on the environment is to take action yourself. There are lots of ways we can all be proactive and take advantage of what we already have access to in order to cutback on our daily waste. One example, is by using public transport, walking or using a bicycle instead of taking your individual car.
There are many public transportation options in Berlin, such as U-Bahn, S-Bahn, bus, tram, train (Zug), and countless walking or cycling paths. There are also countless companies offering rental or cheap bicycles for you to use during your stay. Many bike lanes in Berlin even have their own traffic light which is great for ease and safety. Though, I still recommend using your helmet since Germany is known for their fast drivers!