Z3 (zero energy, zero water and zero waste)
The Zero Energy concept: making the whole greater than the sum of the parts to meet the Paris Climate Agreement’s objectives.
Urban areas, which are expected to host more than two-thirds of the world’s population by 2050, provide unique opportunities for the implementation of the radical policies needed to meet the Paris Climate objectives. Pioneer municipalities in Europe are leading the transformation needed to achieve zero energy and/or zero carbon communities by integrating policies across different sectors (buildings, transport, waste, water and energy supply).
In 2013, urban areas were occupied by 53% of the global population and were responsible for 64% of the global primary energy use and 70% of the global CO2 emissions . By 2050, urban areas are projected to host more than two-thirds of the global population  leading to an increase in cities’ contribution to global warming and energy demand. The level of resilience of urban areas to climate change will, therefore, determine the global resilience as cities and metropolitan areas are considered to be the scale at which the battle for sustainability and against climate change will be won or lost .
The aim of the initiatives is to achieve zero energy and zero carbon or Z2 (zero energy and zero waste) or Z3 (zero energy, zero water and zero waste) communities by putting into practice the waste-energy nexus or the waste-water-energy nexus.
The Current Opinion journals were developed out of the recognition that it is increasingly difficult for specialists to keep up to date with the expanding volume of information published in their subject.