Sludge from pulp and paper mills for biogas production

The main focus of this book is on energy efficient strategies for sludge management, with special focus on anaerobic digestion which produces biogas to replace fossil fuels. Pulp and paper mill sludge is currently treated as a poor quality biofuel and some mills treat it solely as a disposal problem. Our results show that electricity used for aerators in the wastewater treatment plant should be kept to the minimum required for sufficient reduction of dissolved organics. If more electricity is used, i.e. if more air is used for wastewater treatment, this will reduce the energy value of the sludge as the bio-sludge will be degraded. Biogas production using anaerobic co-digestion of pulp- and paper mill sludge together with either municipal wastewater treatment sludge or with manure and grass silage has been studied from several perspectives. It was found that anaerobic digestion is a feasible option for pulp and paper mill sludge management, provided that co-digestion with other substrates is used for nutrient supplementation.