Here are some other adjectives that can be used to describe waste:
* Discarded
* Unused
* Unwanted
* Unnecessary
* Inefficient
* Excessive
* Squandered
* Mismanaged
* Polluting
* Harmful
The best adjective to use will depend on the specific context. For example, if you are talking about waste in a business context, you might use the adjective inefficient. If you are talking about waste in an environmental context, you might use the adjective polluting.