In nature, there is no waste. Or, perhaps a bit more accurately, "waste" from any source becomes the feed for another. Everything is a raw material for some other process or system. Sometimes the changes are minor, as with the exchange of oxygen and carbon dioxide in respiration, while at other times they are hugely transformative, such as the use of soil to grow into a structure like a tree.
We're glad to find opportunities to increase efficiency in systems, as a method of waste reduction. Capturing energy is an easy way of improving efficiency and reducing waste. Co-generation systems get double use by generating both electricity and heat, the heat being a waste product of the electrical generation system.
A wide range of companies are pushing to reduce their waste, and "zero waste" is a concept that is being discussed in more and more boardrooms. A recent article in the Boston Globe discusses how this idea is spreading.