There are attractive opportunities to use organic waste materials as a source of energy for several industries. This allows for the elimination of waste and residues, and at the same time saving money and minimising the use of fossil fuels. This entails important challenges due to the special nature of wastes and the need to focus on appropriate equipment design that minimise the risks involved, really obtain the economic advantages, keep environmental emissions within limits and ensure process safety and equipment stability. This study presents a review of some of the challenges that involve the use of organic waste materials as fuels in boilers, and how these can be resolved. Some real cases are presented.