Resumo

Climate change impacts various aspects of the climate system and holds substantial implications for the biosphere and socioeconomic development. Predominantly caused by the combustion of fossil fuels and the emission of greenhouse gases, a critical solution lies in enhancing energy efficiency and transitioning to cleaner energy sources. Green hydrogen (GH) emerges as a promising clean energy carrier, offering a potential leap in the energy transition and sustainable development.

A better in-depth comprehension of water resources is crucial for GH production, especially in semi-arid regions with, which are likely to be severely affected by climate change. Challenges related to climate, and abuse of water resources can further unbalance water availability, exacerbating existing vulnerabilities and potentially creating new ones. this study aims to evaluate the production of green hydrogen comparing the use of two different water sources: recycled water, representing a circular economy approach, and seawater desalination, representing a linear economy approach.

Hydrogen can be obtained by electrolysing water. Managing water consumption in the green hydrogen sector is a challenge due to the possible long-term impacts on ecosystems and local water availability. In water management, recycled water for industrial applications is preferable to seawater desalination, a linear economy approach. The circular economy, in contrast to the linear "take-make-dispose" model, minimises resource input, waste and emissions. Brine from seawater desalination contains high salinity and chemicals, which can cause ecological impacts when disposed of at sea.

This research employes System Dynamics (SD), combining qualitative and quantitative methods for exploratory and descriptive purposes. We conducted 11 interviews and analyzed several documents, such as Environmental Impact Assessments. The Causal Loop Diagram was developed from two perspectives: multifaceted interactions among technological, ecological, and social factors, and comparing circular and linear economy approaches. The Stock and Flow Diagram aims to estimate GH production under different water supply assumptions, simulating from 2026, when the first hydrogen plant starts, until 2050.

Regarding to operational aspects of the GH hub, use solely recycle water shows the best performance due to highest values of GH production and the lowest values of energy consumption, while using 100% of seawater desalination is the second in values of GH production, however, is the one with the highest energy consumption. Considering the impacts, recycle water shows the best performance, demonstrating the benefits of circular economy. Relying solely on seawater desalination worst performance due to the higher values of brine disposal in the surrounding areas of the hub.

Adopting a linear economy approach in a large-scale, export-oriented hydrogen hub could exacerbate social inequalities and increase environmental degradation. We argue that the abundance of renewable energy and an industrial and port infrastructure cannot be decisive arguments for the hydrogen economy. It is imperative to consider the influence of hydrogen production on social and ecological aspects. We recommend that stakeholders adopt a circular economy approach to better address social-ecological-technological systems (SETS) and ensure energy justice for the GH project in Ceará.

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