Most of the biowaste produced in cities (such as garden and park waste, food and kitchen waste from households, restaurants, caterers and retail premises), as well as sewage sludge from urban wastewater treatment plants are processed into compost and biogas used for energy recovery or even landfilled without fully exploiting in a smart and innovative cascading fashion its potential as feedstock for valuable and precious compounds. New and emerging processing technologies can enable the recycling and valorisation of urban biowaste into higher-value biobased products (e.g. biobased chemicals and plastics, nutrients, human food or animal feed ingredients and proteins), thereby generating significant economic, social and environmental benefits. The successful implementation of urban biowaste recycling and valorisation technologies will require an integrated system innovation approach in a city context. Besides the technological challenges, there will be a need for public authorities to adopt new policies; changing citizens' behaviour will require social innovation initiatives, and new, profitable business models along the entire urban biowaste value chain will have to be developed.