Focus on the future: 3D printing : Trend report for assessing the environmental impacts / Publisher: Umweltbundesamt, Section I 1.1 Fundamental Aspects, Sustainability Strategies and Scenarios, Sustainable Resource Use ; Authors: Keppner, Benno; Kahlenborn, Walter; Richter, Stephan; Jetzke, Tobias; Lessmann, Antje; Bovenschulte, Marc