We waste a lot of paper. While we have done a good job setting up recycling bins, we could save significant money on the purchase of paper if we found a way to internally re-use paper. For instance, many times PDF files print incorrectly, producing a line of indecipherable gobbledygook on a huge number of wasted sheets of paper. Turn these sheets over and they could be easily printed on again--so long as the person printing is only printing a document for internal use. (I.e., it doesn't require a perfect sheet of paper).
First step: have a place to collect such sheets of paper. (the person who printed the document tacitly approves that they be made available for re-use; i.e., there is nothing confidential or private on the mis-printed sheet.)
Second step: put them in a printer in a designated drawer.
Third step: the IT department (perhaps working with printer vendor) will create a means by which anyone printing can choose which drawer they are printing from (so that they can print to the lesser quality paper if they wish to)
Fourth step: Create 'job aid' sheets and distribute them to employees so they are aware of this option and how to use it.