Background Sewage sludge generated in urban wastewater treatment plants (WWTPs) is a complex, heterogeneous mixture of microorganisms, inorganic materials and organic substances. It is classified as a non-hazardous waste. Sludge disposal can represent up to 50% of the WWTP management costs. Sewage sludge must undergo some treatment in order to reduce its volume, improve its characteristics (e.g. odour elimination and organic matter content reduction) and reduce associated health problems. The Urban Waste Water Treatment Directive (91/271/EC) stated that urban centres of more than 2 000 inhabitants should have introduced treatment of wastewater by 2005. This produced an annual increase in sewage sludge production of around 50% for the period 1992-2005 in the then EU-15. Data on sewage sludge production, however, is unavailable for several countries, while other countries have questionable figures. The highest sludge production was recorded in France, Germany, Italy, Spain and the UK, contributing to more than 60% of total sludge produced in Europe. Sewage sludge production will possibly be around 20% higher in EU-15, while a rise of 100% could be expected for new Member States. Therefore, it is important to set up the basis for sustainable and environmentally friendly management of sewage sludge in EU in small to medium-size urban WWTPs, where there is a need for viable and feasible solutions for sewage sludge treatment and disposal. Objectives The project LIFE-ANADRY will test Dry Anaerobic Digestion (AD) technology under thermophilic (55 °C) and mesophilic (35 °C) conditions as a more effective treatment method for the sewage sludge produced in WWTPs. The implementation of dry AD of sewage sludge at semi- or pre-industrial scale has not been carried out to date. The project will test this technology in a 20 m3 pilot plant to be installed in the urban WWTP of Mula (Murcia, Spain). It will demonstrate that the abovementioned process offers a vast improvement in terms of effectiveness, cost-effectiveness and sustainability over other methods for sludge treatment in small to medium-size WWTPs. The process will offer: 1. Enhancement of biogas production with a concomitant reduction in energy use; 2. Reduction of the operating costs in the WWTPs; 3. Sludge stabilisation and hygienisation; 4. Reduction of carbon emissions due to the minimisation of the use of inorganic fertilisers (recycling sludge as fertiliser); and 5. Comprehensive data that supports the attractiveness of the technique for full-scale application. Expected results: An inovative solution for sludge treatment that will resolve the environmental problem the EU is facing in the wastewater treatment sector, resulting in the demonstration of the technical and financial feasibility of high-solid anaerobic digestion technology; Sludge stabilisation (volatile solids 40-60% at the effluent); A 30% reduction in transport costs and therefore environmental impacts linked to transportation – around 0.225 kg CO2/km emissions avoided; Improvement in the quality of sludge produced with an expected reduction of 50-99% in pathogen content; An 80% reduction of reactor volumes compared to conventional wet digestion (compact digester with higher volumetric organic loading rate), and consequently less consumption of material resources; A Reduction in GHG emissions in sludge stock deposits due to the reduction of quantities of sludge generated and the process applied; Resource recovery from organic matter as green energy: the biogas produced contributes to the energy self-sufficiency of the WWTP. It is estimated that 376 000 kWh of electricity and 446 760 kWh of thermal energy will be produced by a facility that treats 2 500 m3/day; A 70% substitution of inorganic fertilisers thanks to the use of sludge recycled in agriculture and reduction of carbon emissions associated; and Operating cost reduction in the WWTP.