From theory to reality: A circular pathway for pink hydrogen in Japan beyond 2040

This is article 1 of 3 in the "From Theory to Reality" series. 

Section 1: Introduction

This article builds upon the author's seven-part series of articles on illuminem, "Green vs. Pink Hydrogen Production in Japan: a Partial Circular Economy Approach" (Anderson2025a, Anderson2025b, Anderson2025c, Anderson2025d, Anderson2025e, Anderson2025f, Anderson2025g). These articles are based on the author's thesis, "Comparative Analysis of Green and Pink Hydrogen Production in Japan based on a Partial Circular Economy Approach," submitted to Johns Hopkins University in December 2024, in compliance with the requirements for the Master of Science (Energy Policy and Climate) (Anderson, 2024a). The thesis received the university's highest academic merit award for this program, "2025 Outstanding Capstone Project Award" (Johns Hopkins, 2025).

The article is organized as follows. Section 1, "Introduction," reviews the background and methodology of the original research study, "Comparative Analysis of Green and Pink Hydrogen Production in Japan based on a Partial Circular Economy Approach." Section 2 examines significant developments in Japan's nuclear, hydrogen, and wastewater management sectors since December 2024 and evaluates the extent to which these developments reinforce the relevance and practical applicability of the author's original research study. Section 3 concludes the article.

Background

Earlier, at "Japan Energy Summit & Exhibition – 2024" in Tokyo, the author presented her innovative "Begin at the Beginning" strategy: nexus-integrated policies for clean hydrogen domestic production and integration into high-priority, heavy industry sectors of Japan (Anderson, 2024b). The author's research study utilizes the term "clean hydrogen," as the most frequently used in the global energy sector (Li et al., 2024, 1). Clean hydrogen is a vital opportunity for the global and Japanese energy sectors due to the current aspirations to confront climate change and boost energy and food security while leading toward more sustainable and cleaner energy sources (IEA, 2026; IEA 2024a, IRENA 2024). It is important to note that clean hydrogen is not entirely a clean energy source since all energy systems have pollutants, emissions, and other externalities in their lifecycles and along their supply chains (Sullivan 2022; Gencer 2024).

The main idea of the "Begin at the Beginning" strategy focuses on sustainable clean hydrogen production in domestic clean H2 (green or pink hydrogen) hubs from unused tertiary effluents from co-located wastewater treatment plants and integration into chemicals, refining, and steel sectors (Anderson, 2024b). Clean hydrogen hubs are "networks of clean [hydrogen] producers, consumers, and connective infrastructure that [would] help accelerate the large-scale production and use of clean [hydrogen]" (DOE, 2024, p. 1), as seen in Figure 1.

Tertiary treatment represents the final purification stage in a wastewater treatment plant, following preliminary (removal of large debris), primary (solids settling), and secondary (biological treatment) treatments (CMS, 2025). Since the freshwater supply would continue declining in the future, the author believes that Japan might utilize wastewater with untapped potential as a renewable and virtually infinite energy source. Moreover, from an economic standpoint, recycled water for clean hydrogen production has the potential for cost advantages compared to desalinated water and freshwater (Anderson, 2024a).

Current studies and projects in Japan focus not on a large-scale domestic clean hydrogen production but primarily on building supply chains (Watanabe, 2024). The author's thesis research at Johns Hopkins University was timely, since, in the spring of 2024, the Japanese government started to revise its Strategic Energy Plan (the 7th plan) and update the National Energy Outlook for 2040, which informed how the country plans to meet its 2050 carbon neutrality pledge and describe its NDC for 2035 under the Paris Agreement (Nakano, 2024). Lastly, the Clean H2 Joint Undertaking (2024) affirmed that as clean hydrogen matured as a valid market value proposition, it was necessary to focus on sustainability and environmental aspects while applying the circular economy approach in its development. Moreover, the author's research study was necessary since it sought to build on the existing global research and provide the answer to the following research question: Given the country's energy and environmental situations, which type of clean hydrogen (green or pink) produced in Japan based on a partial circular economy approach would be a more reasonable, practical, and economic future (2040-beyond) energy source?

Circular economy is "an industrial system that is restorative and regenerative by intention and design" (RTS, 2021, p. 3). Sullivan (2022) defines circular economy as "a system within systems nested in systems and then linked to other systems and a recurring circle of resources and products. The circles need to be closed." Ellen MacArthur Foundation (2024) describes the complete circular economy as one based on three principles, driven by its design to: 1) remove waste and pollution, 2) circulate materials and products (at their highest value), and 3) regenerate nature. The complete circular economy has two cycles, biological and technical, which address material production and consumption and the use of natural resources (Figure 2).

The author's research revealed a lack of specific public data on individual complete circular systems nested within Japan's domestic green or pink hydrogen production. Therefore, after consulting with the master's thesis mentors, the author decided to perform a qualitative, multi-criteria comparative analysis of green and pink hydrogen production in future Japanese clean H2 hubs based on a partial CE approach (technical cycle), using public quantitative and qualitative resources from Japan and other countries. The primary criteria for the comparative analysis of Japanese green and pink hydrogen production based on a partial circular economy approach were grouped into four broad areas: 1) economic, 2) impact on the environment, 3) safety, and 4) workforce availability (Anderson, 2024a). The next section describes the methodology of the original research study.

Original methodology

The research study's focus on applying a partial circular economy approach for future Japanese green or pink hydrogen hubs was initially inspired by the Japanese mottainai movement (reduce, reuse, recycle, and respect) (Government of Japan, 2024). The methodology for answering the research question was based on three theoretical frameworks. The first theoretical framework relied on the technical cycle of the Ellen MacArthur Foundation (2024)'s circular economy system diagram (Figure 2). This diagram illustrated that the larger outer loops encircled the smaller inner loops. The inner loops were considered more valuable since most of the value was captured while retaining more of the embedded value of the product by keeping it whole. These loops also represented cost savings to businesses or customers as they used products and materials already in circulation. The study viewed a future Japanese green or pink hydrogen hub as a hypothetical product user in the center of the technical cycle of the Ellen MacArthur Foundation's (2024) circular economy system diagram. Also, throughout the comparative analysis, the study identified the existing or potential elements of these loops or stages in the technical cycle in the development of Japan's green and pink hydrogen hubs, namely 1) share, 2) maintain/prolong, 3) reuse/redistribute, 4) refurbish/remanufacture, and 5) recycle.

The study also utilized the author's two qualitative concepts developed in previous research papers during the Johns Hopkins Energy and Policy Master's in Science program. These concepts were the quasi-revolutionary transition for developing US coastal green hydrogen hubs (Anderson, 2022, 2024c) and nexus-integrated policies for Japan (Anderson, 2023). First, the quasi-revolutionary transition was the transition governance model for developing US coastal green hydrogen hubs (Anderson, 2022). The transition governance model, initially formulated by the Dutch Research Institute of Transitions (DRIFT), was "radical in the long-term, diplomatic in the short-term" (Loorbach, 2022, p. 2). Anderson's (2022) concept was based on the DRIFT's model, transformed by the inclusion of van den Bergh's evolutionary-technical perspective on sustainable development (Zachary, 2014), Sheer's "Energy Imperative" (2012), and the author's additional recommendations. The modified DRIFT's pillars informed the vision and recommendations for developing US coastal green hydrogen hubs: 1) systemic (engage with emerging dynamics across societal levels), 2) back-casting (focus on the desired transition as a starting point), 3) selective (work with transformative agencies already engaging with the transition), 4) adaptive (experiment with multiple goals and transition pathways), and 5) learning-by-doing and doing-by-learning.

Second, nexus-integrated policies for Japan were cross-sectoral policies for improving Japanese environmental and energy situations (Anderson, 2023). This concept was based on the Stockholm Environment Institute (SEI) framework (Hoff, 2011) and the author's proposed sectoral actions for energy and environmental resilience and reliability as well as environmental security. The policies were anchored on the SEI's framework pillars: 1) economy (creating more with less), 2) environment (investing in sustaining ecosystem services), and 3) society (acceleration of integration and better integration of the poorest). The framework accounted for population growth, climate change, and urbanization as pressures on ecosystems and limited resources. Finance, innovation, and governance were vital for implementing these nexus-integrated policies (Hoff, 2011). Moreover, the nexus-integrated policies proposed additional policy recommendations: 1) appreciation that the most feasible options to reinforce energy situations require longer timeframes and might not be similar actions to solve environmental challenges, 2) formulating a multi-dimensional circular economy, 3) analyzing the supply chains and lifecycle emissions of cleaner energy alternatives and choosing the best options for the energy transition, and 4) assuring the just and orderly energy transition, while accounting for various net externalities and tradeoffs (Anderson, 2023; Sullivan, 2022).

The next section describes the significant developments in Japan's nuclear, hydrogen, and wastewater management sectors since December 2024.

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