Never throw out your suggestions and the ideas submitted by your employees. Those ideas that seem poorly reviewed or are irrelevant, unworkable, uninteresting or not feasible will seem different over time. What seemed lousy yesterday may shine next month. Just the simple concepts themselves sometimes provoke different thoughts or further thinking once reviewed by different sets of eyes. Time changes everything, or, it may not. Never throw ideas away; sit on them.
For example, an idea once rejected by quality control, production and process control personnel sitting on a panel assigned to review ideas may very well be thought of as intriguing, by a different panel of judges made up of marketing, sales and engineering people. What should be paid attention to, especially by management and those reviewing suggestions are those new uses for your products. This does not happen very often; the opportunity to broaden the market for an existing product is rare so sit up and pay attention. If someone suggests a new benefit or use, this reveals an expanded market.
Retain all of the ideas submitted to your company. It costs you almost nothing to do this and may pay off over time. Make sure these ideas are retained and this accumulated list is pulled out and presented to another different set of eyes in the future. Present the rejected list to this new panel without comment and let them discuss any of their thoughts on the concepts.
Example: A type of glue was developed and ultimately rejected by a company many years ago. It was turned down because it did not stick very well; it failed laboratory tests. A smart secretary who worked for the firm noticed these failing properties and asked if she could have that rejected batch. Her reaction and subsequent follow-up led to the creation of the glue that was used for making post-it notes. No one in engineering, production or even the sales department saw the future possibilities of this rejected substance, most likely to their personal regret.