Background The pulp and paper industry in Europe and globally is a major user of electricity and emits large quantities of CO2 (five per cent of the world’s total industrial energy consumption in 2007, amounting to two per cent of direct CO2 emissions from the industrial sector). The wastewater treatment within pulp and paper industry normally comprises a primary treatment for removal of suspended solids such as fibres and bark particles. Sedimentation, flotation and filtration techniques can be applied. The remaining wastewater needs to be cleaned to remove dissolved organic matter and an aerobic biological treatment is thus applied. Chemical oxygen demand (COD) is reduced by the action of active microorganisms, degrading the organic matter in the wastewater. Normally the biological treatment is run to obtain the lowest possible sludge yield, while obtaining a high COD-reduction. One of the reasons is that the sludge is seen as a waste that needs to be disposed of and not as a resource. The waste sludge within pulp and paper production is often dewatered and disposed of by incineration. Incineration of wet waste sludge has a negative energy balance and fuel needs to be supplied, which is a cost for the mills. Objectives The main aim of the EffiSludge for LIFE project is to build and operate the first ever demonstration plant that substantially increases the biogas potential from wastewater generated within the pulp and paper industry, and at the same time lowers electricity consumption by 50%. The project will introduce an innovative process at pilot scale, by modifying the aerobic bio-treatment for increased production of waste sludge. The waste sludge from the bio-treatment will be used as a substrate for anaerobic digestion to biomethane, with sludge production being optimised for this purpose. The final volume of residue sludge, after implementation of the EffiSludge concept, including anaerobic digestion, will be less than if the actions had not been implemented. In addition, biomethane will be produced from the organic matter in the wastewater. Expected results: In comparison with the state-of-the-art within wastewater treatment at European pulp and paper mills, the EffiSludge for LIFE project is expected to give the following results: The electricity consumption in the aerobic wastewater treatment will be reduced by at least 50% per unit of wastewater; Biomethane corresponding to 0.10 – 0.15 m3/kg ingoing wastewater COD will be produced; and No negative effect on the quality of the outgoing wastewater should be observed, i.e. the levels of outgoing COD, N (nitrogen) and P (phosphorus) will be the same or lower than before the process change, and the final amount of residue sludge (after anaerobic digestion) will be less than that currently generated in the aerobic treatment; and The residue sludge generated from the EffiSludge process (after anaerobic digestion) will be less problematic to dewater then the waste sludge generated in the conventional bio-treatment, and higher dry matter content can thus be obtained before incineration.