The project faces the program challenge of developing and implementing solutions for increasing energy efficiency and renewable energy production in public infrastructures. This issue is addressed by combining and integrating the relevant public infrastructures of municipal solid waste chain with the waste water treatment plants (WWTP), and by upgrading their input mix and their energy outputs through: (I) the enrichment of the upstream supply chain providing compatibility with a wide biomass mix from agriculture, agro-food and public green; (II) strengthening the integration and empowerment of internal processes for maximizing energy efficiency and renewable energy outputs (electricity, heat, biogas, bio-methane) to be locally consumed at the WWTP or fed into public/private grids or used in the public mobility and waste collection trucks. The project shows with five pilot feasibility studies of different REEF 2W models in as many WWTPs, how the new REEF 2W solutions lead to an abatement of energy needs and to a significant increase of renewable energy production. Pilot cases become key enablers for WWTPs energy self-sustainable, or even “renewable energy positive”, ideal for providing green energy to future smart-cities.  Induced profits can be reinvested in improving urban services or in renewing the WWTPs themselves. This last result can also solve a problem affecting many old WWTPs, relying on the need to fulfil stringent environmental regulations, with consequent negative energy balance and high operating costs. The project, with a transnational approach, will make available for public administrators and stakeholders knowledge, information about REEF 2W solutions, set up the criteria to identify suitable REEF 2W sites, provide tools for the feasibility studies, perform feasibility studies, start the design of new REEF 2W plants, identify and help to remove barriers/obstacles that can hinder REEF 2W realizations in program area, with more than 20.000 WWTPs.