Background Centralised energy and wastewater systems currently do not allow energy generation from sewage and in contrast, require considerable energy for the treatment of the black, grey and rain water. The HWC project is part of a new 35 ha real estate development, comprising some 700 apartments, of which 570 will take part in the project. These apartments will be fitted with water-saving vacuum sanitation technology and separate wastewater collection, drainage and treatment systems. The black water stream will be used for energy generation. The grey and storm water streams will be treated separately using a new and simplifies approach. Objectives The project’s overall objective is to demonstrate the technical, environmental and economic feasibility of an integrated and decentralized wastewater disposal and energy generation system for an urban housing district in Hamburg, Germany. The concept will bring together well-known technologies, as well as new and innovative prototypes – to be demonstrated for the first time on a large-scale. The system will be developed in different phases, in accordance with the different phases of construction. Specific objectives are to: Demonstrate an integrated wastewater disposal and energy generation system; Minimise the dilution of sewage with drinking water (flush) by the use of vacuum toilets within an urban district; Promote water quality, i.e. preventing rain and grey water from being polluted with black water; Save energy by systematically treating and utilising separated wastewater streams. This will be done by preventing energy consuming wastewater processing; Demonstrate an innovative decentralised energy generation concept based on a biogas plant and a combined heat and power plant, in combination with solar and geothermal plants. The concept will demonstrate the potential to minimise the use of non-renewable energy sources and the potential for energy generation based on separation of black water; Prepare for future phosphorus and nitrogen recovery and effective elimination of micro pollutants such as pharmaceuticals.Expected results: The main expected result will be an innovative urban wastewater and energy system comprising: Approximately 1 000 vacuum toilets, and a vacuum pipe system, reducing water consumption by 7.3 m³/year per person, by vacuum toilet; A biogas combined heat and power generation plant, generating approximately 800 kWh/year per person; A geothermal power plant generating about 1000 kWh/year per person;Overall, the target district will save around 500 tonnes/year of CO2 equivalents and will be self-sufficient in terms of wastewater treatment and heat supply. It will produce some 50% of its electricity demand locally.