This section of the present web site is dedicated to the foundations of the CRUNCH research and, particularly, to  the definition of knowledge needs, glossary and best practices, with the aim to implement the FEW-Nexus solutions for urban settings.

Being an inventory, this section will stay open during the next three years and be constantly updated by the CRUNCH researchers, in order to provide an archive for future research developments in the field.

Definitions of  FEW-Nexus and Circularity

The Nexus describes the key interactions between parts of a system or systems (Lehmann, 2018).

The Urban Nexus is frequently described as the interrelated complex system where food, water, energy and waste treatment systems intersect (Gold & Bass, 2010).

The holistic Nexus approach is based on the untapped inter-dependencies between the sectors with potential for resource-efficiency (Lehmann, 2018)

The term Urban Nexus refers to linkages, interconnectivity and interdependencies in urban systems (energy, water and food and material provisioning systems) and to the need for integrated holistic approaches across these sectors (Bazilian et al., 2011).

The 3 key concepts (resource nexus, circular economy and decoupling) are not exactly the same – each has another focus – however, they have all resource efficiency of urban systems at their core. The multi-scale EWFW Nexus approach aims to introduce integrated urban planning and management processes that will increase the efficiency of natural resource use, reduce emissions and waste and as a result contribute substantially to the resilience of cities and their regions.

The Circular Economy is “an economy which balances economic development with environmental and resources protection. It puts emphasis on the most efficient use and recycling of resources, and environmental protection. A Circular Economy features low consumption of energy, low emission of pollutants and high efficiency; it involves applying cleaner production processes in companies, eco-industrial park development and integrated resource-based planning for development in industry, agriculture and urban areas” (UN EP, 2013, pp. 16–18).

There are clear overlaps in the Resource Nexus and in the concept of Circular Economy. The decoupling concept is key to the circular economy and urban metabolism concepts (as outlined in the Hannover Principles by McDonough & Braungart, 1992, which led to the Cradle-to-Cradle concept).

In contrast to an unsustainable linear economy, a Circular Economy is restorative and regenerative by design and can be seen as a practical solution to the emerging resource crunch which has resulted in growing tensions around geopolitics and supply risks, contributing to volatile and insecure conditions (Lehmann, 2018).

The EWFW Nexus outlines an approach to the design of sustainable urban development solutions where the systems are integrated, providing benefits to each other. (Davoudi and Porter, 2012, Davoudi, 2014).

Definition of needs

When land is converted through the process of urban development, the landscape is intensely transformed and precipitation systems, hydrological cycles, productivity of the ecosystem, energy balance and local climates are all disrupted and modified (Alberti, 2005, Foley et al., 2011).

While cities currently use merely 2% of worldwide land cover (Scheider, Friedl, & Potere, 2009: 182), resource availability constraints and climate change create challenges for the provision of healthy food, essential energy and clean water supply for a growing population (Lehmann, 2018).

The Nexus reflects “the need to integrate resource management processes that increase the efficiency of natural resource use and infrastructural systems, transform planning practice and reduce CO2 emissions and waste generation. The approach is based on the untapped inter-dependencies between the sectors; for instance, looking holistically at the energy and water system as part of a multi-dimensional network of urban systems” (Lehmann, 2018).

More and more urban experts agree that the currently used systems of food, water and energy provision and waste treatment for material recovery are on an unsustainable course (Bringezu and Bleischwitz, 2009).

Policy and decision makers are concerned that climate change impacts, an overuse of land, increasing inequality and other urban challenges threaten our food, water and energy security and place pressure on future cities globally (Lehmann, 2018).

With targets to cut greenhouse gas emissions, stakeholders from civil society, industry and government are looking for support and guidance for ‘good’ decision-making in urban design and development (Lehmann, 2018).

The circular economy can help to stabilise these issues by decoupling economic and urban growth from resource consumption. Key principles of the Circular Economy include: to preserve and enhance natural capital by controlling finite stocks and balancing renewable resource flows, to optimise resource yields by designing for remanufacturing, refurbishing and recycling to keep materials and components circulating and contributing to the economy, and to foster system effectiveness by revealing and designing out negative externalities (Ellen MacArthur Foundation, 2014).

The importance of FEW-Nexus integrated approach has frequently been acknowledged and there is now increasing recognition of the dynamic interplay of resources and their supply systems in the urban context, such as the close interconnection that energy, water, food and material flows could provide as an opportunity for a ‘policy nexus’ to better integrate planning and resource management within and across urban boundaries, sectors and jurisdictions that can be translated into tangible, handbook-like insights for cities and regions elsewhere. (Daher & Mohtar, 2015).

Typically, options for solving problems facing the food, water, energy or waste sectors are approached in isolation and in piece-meal planning, eg. exploring how to meet water needs, whilst overlooking the implications for energy consumption, or setting targets to change land-use and ignoring knock-on impacts for agriculture. This 'silo' mind-set does not allow important interconnections between these systems and explore the potential benefits or trade-offs (Lehmann, 2018).

The proposed EWFW Nexus recognises the linkages and aims to better respond to the need for integrated policies and implementation mechanisms with systems optimisation through an approach to counter silo-thinking between the urban sectors, transforming the inefficient system and moving away from out-dated single-purpose solutions (Lehmann, 2018).

The effectiveness of the use of water and energy resources and the successful recovery of materials/waste is still limited and widely determined by the fragmentation of systems, availability of technology and by the type of resource management (Lehmann, 2018).

The Urban Nexus is still an immature, emerging concept requiring more clarification and testing in cities (Lehmann, 2018).

The urban planning and transformation has so far not paid adequate attention to the resilience of city systems and appears poorly prepared to face adaptation and mitigation challenges (Davoudi and Porter, 2012, Davoudi, 2014).

Best practices

An attempt to decouple growth from the use of resources was successfully initiated in Curitiba (Brazil) in the 1990–2000s: Community-level decoupling is achieved through the exchange of recyclable waste for bus vouchers and fresh local produce, such as locally grown vegetables. Curitiba's Bus Rapid Transit (BRT) is a lower cost alternative to rail transit. 90% of Curitiba's residents are involved in daily recycling activities of their waste and achieve around a 70% recycling rate. This highly successful initiative creates a strong link between integrated public transport, waste recycling and job creation (empowerment of unemployed people) (Lehmann, 2018).