Sustainable energy-water-food nexus integration and optimisation in eco-industrial parks

A Comprehensive Evaluation Framework of Water-Energy-Food System Coupling Coordination in the Yellow River Basin, China

For mankind's survival and development, water, energy, and food (WEF) are essential material guarantees. In China, however, the spatial distribution of WEF is seriously unbalanced and mismatched. Here, a collaborative governance mechanism that aims at nexus security needs to be urgently established. In this paper, the Yellow River Basin in China with a representative WEF system, was selected as a case. Firstly, a comprehensive framework for WEF coupling coordination was constructed, and the relationship and mechanism between them were analyzed theoretically. Then, we investigated the spatiotemporal characteristics and driving mechanisms of the coupling coordination degree (CCD) with a composite evaluation method, coupling coordination degree model, spatial statistical analysis, and multiscale geographic weighted regression. Finally, policy implications were discussed to promote the coordinated development of the WEF system. The results showed that: 1) WEF subsystems showed a significant imbalance of spatial pattern and diversity in temporal changes; 2) the CCD for the WEF system varied little and remained at moderate coordination. Areas with moderate coordination have increased, while areas with superior coordination and mild disorder have decreased. In addition, the spatial clustering phenomenon of the CCD was significant and showed obvious characteristics of polarization; and 3) the action of each factor is self-differentiated and regionally variable. For different factors, GDP per capita was of particular importance, which contributed most to the regional development's coupling coordination. For different regions, GDP per capita, average yearly precipitation, population density, and urbanization rate exhibited differences in geographical gradients in an east-west direction. The conclusion can provide references for regional resource allocation and sustainable development by enhancing WEF system utilization efficiency.

Comparison of Optimisation Algorithms for Centralised Anaerobic Co-Digestion in a Real River Basin Case Study in Catalonia

Anaerobic digestion (AnD) is a process that allows the conversion of organic waste into a source of energy such as biogas, introducing sustainability and circular economy in waste treatment. AnD is an intricate process because of multiple parameters involved, and its complexity increases when the wastes are from different types of generators. In this case, a key point to achieve good performance is optimisation methods. Currently, many tools have been developed to optimise a single AnD plant. However, the study of a network of AnD plants and multiple waste generators, all in different locations, remains unexplored. This novel approach requires the use of optimisation methodologies with the capacity to deal with a highly complex combinatorial problem. This paper proposes and compares the use of three evolutionary algorithms: ant colony optimisation (ACO), genetic algorithm (GA) and particle swarm optimisation (PSO), which are especially suited for this type of application. The algorithms successfully solve the problem, using an objective function that includes terms related to quality and logistics. Their application to a real case study in Catalonia (Spain) shows their usefulness (ACO and GA to achieve maximum biogas production and PSO for safer operation conditions) for AnD facilities.

Spatial and Temporal Differentiation of the Tourism Water Footprint in Mainland China and Its Influencing Factors

While tourism generates economic benefits at destinations, it also creates certain environmental pressures. In the global context of water scarcity, the spatial and temporal differentiation characteristics of water consumption at tourism destinations have become a focus of attention. Based on panel data, the present study calculates the change trends in China’s tourism water footprint (TWF) in the 2013–2018 period using input-output analysis, analyses the regional differences in TWF changes using kernel density estimation and the Theil index, and investigates the driving factors of the spatial and temporal differentiation of the TWF using the logarithmic mean Divisia index model. The results indicate that (1) the tourism water consumption in China increased year-by-year but that the tourism water use efficiency improved; (2) the proportion of the TWF for accommodation and food in the total TWF gradually increased, while the proportion of the TWF for transportation continuously decreased; (3) the TWF of each region increased continuously, with the absolute difference between regions gradually increasing and the difference in the TWF intensity gradually decreasing; and (4) decomposition analysis showed that the TWF in China was positively driven by per capita expenditure and the number of tourists, with the role of TWF intensity shifting from inhibition to promotion, and that each driving force changed with time. Based on the spatial and temporal differences in the TWF, the provinces in China are divided into five categories, and targeted countermeasures and suggestions are proposed.