these tools are contributing to the growing science of cities this initiative envisions the use of circular economy techniques to link an urban extension to existing settlements the initiative aims to incentivize ideas for decentralized closedloop models of spatial planning and periurban service provision that replace fossil energy with renewables derive new water biogas and fertilizer from wastewater and produce food and biofuel with recycled inputs all cogenerated at near netzero waste each reneww zone would offer within walking or cycling distance a green space for community recreation recycling and sanitation services as well as a place to purchase fresh food recycled goods biofuels and safe drinking water