There are many paths to an environmental career. Most disciplines in engineering have green paths these days. Depending on what you are interested in and where you decide to go to school, I think you will be able to find something really interesting. You mention that you like recycling and inventing. One area that is really exciting right now is green design. If you pursue a Mechanical Engineering degree, you can focus on how to design environmentally friendly products. Since electronic products have such a quick turn over these days, research into ways to use scrap electronics is big right now as is designing greener products in the first place. I wish you the best of luck finding a great fit for your interests!