The garbage disposal is located in the basement next to the bikeshed.
Make sure to empty the bins in your room and kitchen regularly to avoid nasty smells and bugs from being attracted.
If you want to donate good quality clothes or stuff, check the many second hand shops in the surroundings. Good quality clothes can also be put in special collection containers mostly located close to supermarkets or shopping malls.
If you want to donate your left-over food, you can bring it to Foodsharing Maastricht. A grassroots initiative that raises awareness of food waste and organises unconditional food redistribution.