PapierslibThe fibres in paper and cardboard can get recycled approximately five times, depending on the type of paper which is being produced. The fibres are discarded in the pulping process and end up in a sludge we call paper sludge. This paper sludge is a valuable resource for many industries, both as an alternative fuel as well as an alternative raw material. Lignite boilers co-combust paper sludge, taking benefit from both the heating value as the calcium which is in the paper sludge.