My wife is fastidious when it comes to reusing old stuff instead of buying something new. Recently while going through some of her things, she accumulated enough old paper and notebooks that, once reworked, were enough to keep her stocked for the new semester. Students will accumulate vast amounts of paper very quickly. It doesn't matter that a lot of students are using computers now, there will always be a place for paper when you need to write things down. While I'm a bit more anal when it comes to my notebooks, I should learn a few things from my wife, who has no qualms about reusing her notebooks over and over again to get things done.
There is a way about going about this without creating too much waste, especially if you are planning on keeping some of your notes. Once you've made a pile of your notebooks, go through them carefully. Generally, if a notebook has at least 20 pages free, it's worth keeping. Recycle old notes if you don't need them. If you do, cut them out using scissors or a utility knife. This will keep the papers nice and flat compared to ripping them out. Then create a laminated cover or bind those notes together to keep them organized, if you desire. (Staples or your university bookstore should be able to help you out with this. It can be really effective and professional-looking. Some of the ones we've seen even look like hardcover books.)
And there you have it! Just a simple reminder to find ways to make due with what you have.