###### Abstract
End use includes a large number of: chemicals (e.g., methanol, and ammonia), industry (refinery, steel, and cement), residential and commercial (e.g., blending into natural gas pipelines), mobility (e.g., fuel cells electric vehicle), power (e.g., power generation by turbine and storage as a backup power in fuel cells or tank storage), and space applications (e.g., rocket fuel). Previous efforts have focused, mainly, on hydrogen production resources and systems [11, 12, 13, 14, 15, 16, 17]. For example, [PERSON] et al. [11] assessed innovative hydrogen production methods under various criteria. [PERSON] et al. [12] highlighted the state-of-the-art hydrogen production technologies using renewable and sustainable energy resources. [PERSON] et al. [18] provided a review on sustainability of hydrogen production systems. [PERSON] et al. [14] focused on various hydrogen producing and storing methods for creating a hydrogen economy. When considering the impact of hydrogen on the environment, the focus rests on issues related to the leakage of hydrogen [19, 20, 21, 22, 23, 24]. For example, [PERSON] et al. [19] and [PERSON] et al. [20] investigated the safety of hydrogen fuel cells by a numerical simulation of hydrogen leakage from fuel cell ship and vehicle, while [PERSON] et al. [21] assessed the risk  
Figure 1: Hydrogen entire process stages. of an urban hydrogen refuelling station. The pathways of hydrogen use have received little attention in research or policy, which may be explained by the common belief that nothing but water is released as a by-product when hydrogen energy is used, a belief that is only true for the fuel cells pathway. Burning of hydrogen in the combustion pathway can produce Nitrogen Oxides (NO\({}_{x}\)), which have something in common between hydrogen and fossil fuel when burned at high temperatures [25; 26; 27]. NOx is a harmful air pollutant that can be formed in all fuel-air mixed in high flames (above 1300 \({}^{\circ}\)C); less than 750 \({}^{\circ}\)C no NOx is formed [26; 28]. This may pose a risk to the future of hydrogen energy as a combustion fuel. On the other hand, previous studies have employed different approaches to explore the future of hydrogen energy demand, such as the Geographic Information System (GIS) method [29; 30; 31], the Optimal Power Flow (OPF) technique [32], and the mathematical model [33]. However, there is a need to understand the dynamics underlying interactions among the components of any complex system, which is the domain of systems thinking and system dynamics approaches, as applications of these approaches in the hydrogen energy sector have been largely absent. Further, there is a need to focus on fields and/or sectors in which only hydrogen can play a vital role compared with other alternatives, which is missing in many previous studies, and has been taken into consideration in this paper. Exploring the future of hydrogen energy demand and highlighting the risks that may affect the sector are of paramount importance to understand the transition to a hydrogen economy. The aim of this study is twofold: (1) using a systems thinking approach to build a conceptual model for hydrogen energy, with a special focus on the pathways of hydrogen use, to assess the potential consequences that could lead to unintended impacts, and possible interventions; (2) using a system dynamics approach to highlight the possible demand growth of hydrogen energy until 2050. The demand meant here is the global demand, and it will be linked to a case study of a country that may be a leader in hydrogen production in the foreseen future [34; 35; 36]. Australia's path will be compared with the global path, hence potential opportunities need to be seized.