Sludge from pulp and paper production is generated in many thousands of tonnes every year. With a complex mix of organic and inorganic components and a high water content, sludge is hard to recycle or combust for energy recovery. Consequently, sludge has to be disposed of in landfill, causing environmental damage. This goes against Swedish waste management guidelines, which prioritise recycling or energy recovery. In this study, we aim to develop bioremediation processes to minimise the volume of sludge waste and encourage its recycling. We are mainly working on precipitation sludge (PS), a waste stream of which ~8,000 tonnes is generated each year. Our microcosm experiments have revealed extensive microbial activity and enzymatic breakdown of sludge fibres, but the microbial species and enzymes involved remain unknown. Our current goal is to reveal what species and enzymes are found in PS, to develop them as biological tools for PS recycling. To accomplish this, 16S rRNA marker gene sequencing was employed to reveal microbial profiles in PS microcosms supplemented with different carbon sources. Moreover, a shotgun metagenomic sequencing study is giving insight into the species profile and the distribution of carbohydrate-active enzymes (CAZymes) in the sludge microbial metagenome. While metagenomics gives a good indication of the genomic potential for sludge recycling, it does not give insight on which enzymes are actively expressed and involved in fibre degradation. To address this, we have performed a metatranscriptomic sequencing study to discover exactly which CAZymes are involved in degrading sludge fibres. After annotation of our data reveals the CAZyme profiles in the functional sludge microbiome, candidate CAZymes will be selected for further biochemical characterisation for development as a biological tool for sludge recycling. Eventually, this work will contribute to new bioprocesses that can minimise the amount of sludge sent to landfill, resulting in a more sustainable future for the Swedish pulp and paper industries.