Recent years have shown increased awareness that the use of the basic resources water, food, and energy are highly interconnected (referred to as a ‘nexus’). Spatial scales are an important but complicating factor in nexus analyses, and should receive more attention – especially in the policy-oriented literature. In this paper, we ‘unpack' the nexus concept, aiming to understand the differences between water, food and energy resources, especially in terms of spatial scales. We use physical indicators to show the differences in terms of absolute magnitude of production and the distance and volume of physical trade, for seven resource categories: water withdrawal, crops, animal products, bio-energy, coal, oil, and natural gas. We hypothesize that the differences in trade extent are related to physical characteristics of these resources: we expect high priced, high density, geographically concentrated resources to be traded more and over longer distances. We found that these factors, taken together, can explain some of the differences in trade extent (and thus spatial scale involved), although for each individual factor there are exceptions. We further explore the spatial scales by showing the bidirectional physical trade flows at the continental scale for crops, animal products, bio-energy and fossil fuels. We also visualize how nexus resources are directly dependent on each other, using a Sankey diagram. Since both direct dependencies and physical trade are present, we investigate the role of resource-saving imports, which is a form of virtual trade. The resource-saving imports highlight the importance of continental and global scales for nexus analyses.

Water, Energy and Food (WEF) are key elements of economic and social sustainable development, and present a complex nexus. Existed WEF nexus research is mainly confined to qualitative analyses, and it needs constant improvement and increases quantitative analyses. In China, water security is the most prominent problem in the WEF-nexus, which is manifested in the competitive relationship between food and energy production for water. Therefore, the matter of alleviating water resources stress has become a difficult and hot issue. After improving the existed water footprint accounting method for food and energy production, this study calculated the food water footprints (blue water footprint and green water footprint) in the 31 provinces of mainland China in 2015, as well as the blue water footprints of major energy systems (coal, oil, natural gas and thermal power generation). This study proposed water resources pressure index (IWS), water resources pressure contribution rate of food and energy (WCR), water consumption rate of food and energy (n) and competition composite index (CCI) of WEF, which were used to evaluate the consumption of water resources in food and energy production in different regions, and assess the intensity of competition for water resources in food and energy production. The results showed that the national food water footprint in 2015 was 690.8 Gm³, and the blue food water footprint was 287.8 Gm³. The main water-consuming blue energy water footprint was 18.5 Gm³, and coal production accounted for 9.9% and thermal power generation accounted for 87.6%. According to the competition indicators, the competition relationship among the administrative regions of the 31 provinces in mainland China was obtained. For example, 5 provinces had serious competition and 19 provinces had weak competition. The water consumption of the energy industry continues to grow rapidly by economic development. Corresponding measures should be taken according to the different competition levels for water resources.

As the demand for services and products continues to increase in light of rapid population growth, the question of energy, water and food (EWF) security is of increasing importance. The systems representing the three resources are intrinsically connected and, as such, there is a need to develop assessment tools that consider their interdependences. Specifically when evaluating the environmental performance of a food production system, it is necessary to understand its life cycle. The objective of this paper is to introduce an integrated energy, water and food life cycle assessment tool that integrates EWF resources in one robust model and at an appropriate resolution. The nexus modelling tool developed is capable of providing an environmental assessment for food production systems utilising a holistic systems approach as described by a series of subsystems that constitute each of the EWF resources. A case study set in Qatar and characterised by an agriculture sub-system, which includes the production and application of fertilisers and the raising of livestock, a water sub-system represented by mechanical and thermal desalination processes and an energy sub-system, which includes fossil fuel in the form of combined cycle natural gas based energy production and solar renewable energy is used to illustrate the model function. For the nexus system analysed it is demonstrated that the food system is the largest contributor to global warming. The GWP can be reduced by up to 30% through the utilisation of solar energy to substitute fossil fuels, which, however, comes with a significant requirement for land investment.

The sustainability of food production systems is inherently linked with energy, water and food (EWF) resources directly and in-directly throughout their lifecycle. The understanding of the interdependencies between the three resource sectors in the context of food production can provide a measurable account for resource requirements, while meeting food security objectives. The energy, water and food Nexus tool developed by the authors has been designed to model the inter-dependency between energy, water and food resources, whilst conducting an environmental assessment of product systems. With emphasis on the inter-linkages between EWF resources, the tool quantifies material flows, natural resource and energy consumption at component unit process level. This work integrates greenhouse gas control and waste to power technologies within the energy, water and food Nexus tool and evaluates the environmental impact of a hypothetical food product system designed to deliver a perceived level of food self-sufficiency (40%) for the State of Qatar. Multiple system configurations, representative of different pathways for the delivery of consistent food products are evaluated, transforming a once linear product system into a circular design. The sub-systems added consist of a biomass integrated gasification combined cycle which recycles solid waste into useful forms of energy that can be re-used within the nexus. In addition, a carbon capture sub-system is integrated to capture and recycle CO2 from both the fossil fuel powered and the biomass integrated gasification combined cycle energy sub-systems. The integration of carbon capture with the biomass integrated gasification combined cycle transforms the carbon neutral biomass integrated gasification combined cycle process to a negative greenhouse gas emission technology known as bio-energy with carbon capture and storage. For the different scenarios and sub-system configurations considered, the global warming potential can be theoretically balanced (reduced by ∼98%) through the integration of photovoltaics, biomass integrated gasification combined cycle and carbon capture technologies. The peak global warming potential, i.e. a fully fossil fuel dependent system, is recorded at 1.73 × 10⁹ kg CO2 eq./year whilst the lowest achievable global warming potential is 2.18 × 10⁷ kg CO2 eq./year when utilising a combination of photovoltaics, carbon capture integrated with combined cycle gas turbine in addition to the integrated negative emission achieving system. The natural gas consumption is reduced by 7.8 × 10⁷ kg/year in the best case configuration, achieving a credit. In the same scenario, the photovoltaics land footprint required is calculated to a maximum of 660 ha. The maximum theoretically achievable negative emission is 1.09 × 10⁹ kg CO2/year.

As three resources that are necessary for human survival and production, water, energy and food are increasingly closely linked. In recent years, the water-energy-food nexus has attracted special attention from international organizations and academic circles. However, due to the lack of research on its internal mechanisms, there is still controversy on whether the water-energy-food nexus can be used as a new policy basis. The internal mechanisms of the water-energy-food nexus were analysed from the perspective of industrial linkages in this paper and empirically verified by constructing an SVAR (structuralvectorautoregression) model using China’s data. The results showed that there were two forms of conduction in China’s water-energy-food nexus: the water-energy-food nexus with nuclear power participation and that with natural gas participation. The characteristics of China’s water-energy-food nexus were derived. For the interactions of the water-energy segment in China’s water-energy-food nexus, the conduction from energy to water was consistent for different types of energy, while that from water to energy varied depending on the type of energy. Food production always had a negative impact on energy production, while the conduction from energy to food varied for different types of energy. The conduction between food and the water supply was not as significant as was generally considered. Especially, the impact of the water supply on food production was weak. The order of strength intensity and the duration were also available for reference. Accordingly, a new policy basis was presented under the framework of China’s water-energy-food nexus. Both our research design and research findings are significant in contributing to understanding the internal mechanisms of the water-energy-food nexus, and the policy implications are also helpful for achieving better policy effects.

Natural resources are a boon for human beings, and their conservation for future uses is indispensable. Most importantly, energy-food-water security (EFWS) nexus management is the utmost need of our time. An effective managerial policy for the current distribution and conservation to meet future demand is necessary and challenging. Thus, this paper investigates an interconnected and dynamic EFWS nexus optimization model by considering the socio-economic and environmental objectives with the optimal energy supply, electricity conversion, food production, water resources allocation, and CO2 emissions control in the multi-period time horizons. Due to real-life complexity, various parameters are taken as intuitionistic fuzzy numbers. A novel method called interactive neutrosophic programming approach (INPA) is suggested to solve the EFWS nexus model. To verify and validate the proposed EFWS model, a synthetic computational study is performed. The obtained solution results are compared with other optimization approaches, and the outcomes are also evaluated with significant practical implications. The study reveals that the food production processes require more water resources than electricity production, although recycled water has not been used for food production purposes. The use of a coal-fired plant is not a prominent electricity conversion source. However, natural gas power plants’ service is also optimally executed with a marginal rate of production. Finally, conclusions and future research are addressed. This current study emphasizes how the proposed EFWS nexus model would be reliable and beneficial in real-world applications and help policy-makers identify, modify, and implement the optimal EFWS nexus policy and strategies for the future conservation of these resources.