# Life cycle sustainability assessment of a proton exchange membrane fuel cell technology for ecodesign purposes

Mitja Mori, Diego Iribarren, Julie Cren, Emmanuelle Cor, Andrej Lotric, Jure Gramc, Bostjan Drobnic, Laurent Rey, Felipe Campos-Carriedo, Gonzalo Puig-Samper, et al.

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Mitja Mori, Diego Iribarren, Julie Cren, Emmanuelle Cor, Andrej Lotric, et al. Life cycle sustainability assessment of a proton exchange membrane fuel cell technology for ecodesign purposes. International Journal of Hydrogen Energy, 2023, 48 (99), pp.39673-39689. 10.1016/j.ijhydene.2023.05.255. cea-05064700

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# Life cycle sustainability assessment of a proton exchange membrane fuel cell technology for ecodesign purposes

Mitja Mori<sup>a</sup>, Diego Iribarren<sup>b</sup>, Julie Cren<sup>c</sup>, Emmanuelle Cor<sup>c</sup>, Andrej Lotrič<sup>a</sup>, Jure Gramc<sup>a</sup>, Boštjan Drobnič<sup>a</sup>, Laurent Rey<sup>d</sup>, Felipe Campos-Carriedo<sup>b,e</sup>, Gonzalo Puig-Samper<sup>b</sup>, Eleonora Bargiacchi<sup>b</sup>, Javier Dufour<sup>b,e</sup>, Rok Stropnik<sup>a,*</sup>

## HIGHLIGHTS

* A life cycle sustainability assessment of PEMFC stack manufacture is conducted.

* The carbon footprint of the 48 kWe PEMFC stack is estimated to be 1160 kg CO2 equivalent.

* The cost, for a production rate of 50,000 PEMFC stacks/year, is 2233 €/stack.

* Platinum production in South Africa arises as a sustainability hotspot.

* Ecodesign actions on Pt loading and recycling lead to high carbon footprint reductions.

## ARTICLE INFO

**Article history:**

Received 25 January 2023

Received in revised form

29 April 2023

Accepted 25 May 2023

Available online xxx

**Keywords:**

Sustainability

Environmental life cycle assessment

Life cycle costing

Social life cycle assessment

Ecodesign

Proton exchange membrane fuel cell

## ABSTRACT

The EU-funded project eGHOST supports the fuel cells and hydrogen (FCH) industry in shaping the eco (re)design of hydrogen-related products such as proton exchange membrane fuel cell (PEMFC) stacks. Within this framework, a life cycle sustainability assessment (LCSA) of a PEMFC stack was conducted to evaluate its potential environmental, economic, and social impacts. The climate change indicator for one 48 kW<sub>e</sub> PEMFC stack is 1160 kg CO<sub>2</sub> eq., with platinum accounting for 63.5% of the total value. The cost depends mainly on the production rate, and it is 2233 €/stack for an annual production of 50,000 stacks. Social hotspots are mainly associated with platinum production in South Africa. Illustrative ecodesign actions allow a reduction in climate change of 31% and 46% in the realistic (short-term) and optimistic (long-term) concept, respectively. A further reduction in climate change (54% in the optimistic concept) is achieved if 95% recycled Pt is used.

© 2023 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

<footnote><sup>a</sup> University of Ljubljana, Faculty of Mechanical Engineering, Aškerčeva 6, Ljubljana, SI-1000, Slovenia</footnote>

<footnote><sup>b</sup> IMDEA Energy, Systems Analysis Unit, E-28935 Móstoles, Spain</footnote>

<footnote><sup>c</sup> Univ. Grenoble Alpes, CEA, Liten, F-38000 Grenoble, France</footnote>

<footnote><sup>d</sup> SYMBIO, F-73370 Le Bourget-du-Lac, France</footnote>

<footnote><sup>e</sup> Rey Juan Carlos University, Chemical and Environmental Engineering Group, E-28933 Móstoles, Spain</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: rok.stropnik@fs.uni-lj.si (R. Stropnik).
https://doi.org/10.1016/j.ijhydene.2023.05.255</footnote>

<footnote>0360-3199/© 2023 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).</footnote>
**Introduction**

The European Union (EU) has set an ambitious goal to reduce net greenhouse gas emissions to zero by 2050 while ensuring economic and social sustainability. One of the key documents is the European Green Deal [1], which sets out a path to achieving this overall goal by accelerating a series of policy changes that affect many aspects of the EU economy and society. The EU's concern about climate change and depletion of natural resources has sparked interest in fuel cells and hydrogen (FCH) technologies, along with the search for sustainable ways to produce, transport, and use hydrogen [2]. In this context, and due to its multiple applications, hydrogen is expected to play a key role in a future carbon-neutral economy by enabling zero-emission transportation, heating, industrial processes, and energy storage. To underline its importance and facilitate the deployment of hydrogen applications, the EU Commission adopted the EU Hydrogen Strategy [3], in 2020, which aims to accelerate the development of clean hydrogen. Under the Clean Hydrogen Partnership [4], the EU supports research and development of FCH technologies that are currently either uncompetitive or technologically immature and are expected to contribute to climate neutrality by 2050. While some FCH technologies are ready for their use in various applications, it is imperative to develop circular and sustainable approaches in technology development to meet environmental and social principles. The main benefit of the circular economy principle is to add value to the economy, society, and businesses while minimising resource consumption and environmental and social impacts. In this context, Life Cycle Sustainability Assessment (LCSA), which combines Environmental Life Cycle Assessment (E-LCA), Social Life Cycle Assessment (S-LCA) and Life Cycle Costing (LCC), is key to assessing and achieving these ambitious goals.

E-LCA of FCH systems has been covered extensively by other authors. Rinawati et al. conducted a systematic literature review of the technical aspects and methodological choices in E-LCA studies of the use of hydrogen for road transport [5] and power generation [6]. Valente et al. [7] performed a thorough literature review on the methodological choices made in LCA studies of hydrogen energy systems. To extend the analysis of FCH technologies, LCC has been introduced by other researchers to study the life-cycle economic performance of an FCH technology. For instance, in a study by Li et al. [8], a life-cycle optimization modelling framework was introduced to evaluate a hydrogen supply chain network design. Specifically, the LCC methodology and the E-LCA approach were coupled through a bi-objective optimization. Ahmadi and Kjeang [9] conducted E-LCA and LCC of hydrogen fuel cell passenger cars to compare their greenhouse gas (GHG) emissions and life-cycle costs with those of conventional gasoline passenger cars based on a real driving cycle for semi-urban driving conditions for the case of hydrogen production by electrolysis in British Columbia, Canada. Overall, literature results suggest that fuel cell vehicles (FCVs) are becoming both technologically and economically viable compared to conventional vehicles and represent a viable option for deep transportation emissions reductions. Miotti [10] evaluated the environmental impact (E-LCA) and cost

(LCC) of a proton exchange membrane fuel cell (PEMFC) system for use in lightweight FCVs and integrated these results into a comparative assessment between FCVs, battery electric vehicles (BEVs), and internal combustion engine vehicles (ICEVs). The results show that FCVs can reduce life-cycle greenhouse gas (GHG) emissions by 50% compared to gasoline-powered ICEVs when hydrogen is generated from renewable electricity, and thus have similar emission levels to BEVs charged with the same electricity mix. A large contributor to GHG emissions is the PEMFC system, specifically the Pt in the catalyst and the carbon fibres in the hydrogen tank. The large amount of carbon fibre used in the tank was also the reason why FCVs may not be fully cost-competitive with ICEVs or BEVs, even assuming significant technological development and mass production of all components. Furthermore, Wulf and Kaltschmitt [11] investigated the economic viability (LCC) and E-LCA of different hydrogen production technologies using different renewable and fossil energy sources for Germany. In addition, Gulotta et al. [12] conducted a comprehensive review focusing on E-LCA and LCC of PEMFCs. In terms of life cycle thinking methods, only 7 of the analysed papers used both methods. The authors concluded that, given the increasing interest in E-LCA and LCC, decision makers and developers need to fully understand the uncertainties of E-LCA and LCC methods and their implications on identifying appropriate strategies. Additional aspects related to social impact assessment within a broader sustainability assessment of FCH technologies have been analysed by other authors. Assessment of the social acceptance of hydrogen for transportation was conducted by Iribarren et al. [13]. Salim et al. [14] reviewed LCSA impacts of solid oxide fuel cells (SOFCs). A literature review on LCSA shows that there are not many studies on FCH technologies that include sustainability assessment with a life cycle approach, with exceptions such as Valente et al. [15] and Norouzi [16].

In addition to the LCSA of FCH technologies, the European Commission considers ecodesign [17] as a key factor to fulfil its commitment to a carbon-neutral and circular economy by 2050. The current Ecodesign Directive 2009/125/EC has a long track record of delivering benefits to businesses, consumers and the environment [18]. Therefore, the sustainability performance of FCH systems needs to be evaluated in an integrated approach that includes environmental, economic, and social aspects with ecodesign measures. The EU-funded project eGHOST [19] provides a first preparatory study of FCH products according to the principles of the Ecodesign Directive, and improve the understanding of FCH technologies from a perspective of sustainable investments by applying a full LCSA. Since the end-of-life (EoL) phase of FCH products is not well defined yet [20], the synergies with the partnering EU-funded project Best4Hy [21] will be incorporated into the EoL phase (recycled platinum use) alongside the ecodesign measures proposed by the eGHOST project.

Within this context, the current study presents a full LCSA of a PEMFC stack, thereby comprehensively addressing the three main sustainability dimensions (environmental, economic, and social impacts). Unlike the combination of separate studies, the fact that this work jointly addresses the environmental, economic, and social life-cycle performance
of the same observed system with common inventory data provides the study with a robust basis for sustainability interpretation. In addition, the observed system in the study is a 48 kWel PEMFC stack, which corresponds to a very relevant size within the automotive industry. Finally, this novel study goes a step further by evaluating the potential of illustrative ecodesign measures before a high market deployment of PEMFC products, estimating carbon footprint reductions associated with technology improvement (reduced Pt loading) and the implementation of recycled Pt in the manufacturing of PEMFC stacks.

## Materials and methods for life cycle sustainability assessment

The methodologies applied were E-LCA, LCC, and S-LCA for evaluation of the sustainability of a PEMFC stack. Standard databases were used for E-LCA (GaBi – Sphera, and ecoinvent), and the PSILCA database for S-LCA.

### Environmental Life Cycle Assessment framework

The E-LCA methodology standardised according to the ISO standards 14,040 [22] and 14,044 [23] includes four phases: (i) goal and scope, (ii) life cycle inventory (LCI) analysis, (iii) life cycle impact assessment (LCIA), and (iv) interpretation of the results. The study refers also to the International Reference Life Cycle Data System (ILCD) guidelines [24] and the guidance document for performing an LCA on FCH technologies by HyGuide [25].

### Goal, scope, and functional unit

The main goal of the E-LCA study is to evaluate the environmental impacts of manufacturing one 48 kWel PEMFC stack used for passenger transportation in a light-duty vehicle, which represents the functional unit (FU), without balance of plant (BoP) components. The scope of the study is ‘cradle to gate’ (manufacturing phase) excluding the use and EoL phases of the product. The PEMFC stack is manufactured to be subsequently used in transportation applications (light vehicles). Regarding geographical and time scope, production in Europe was considered based on current conditions. The reference year of the data is 2021 and data sets could be considered valid until 2024 [26].

### Life cycle inventory analysis

The detailed technical specifications and bill of materials (BoM) were provided by the industrial eGHOST partner, where the list of material and energy flows identified to produce one reference PEMFC stack was collected. The stack consists of 280 membrane electrode assembly (MEA) units with an active area of 200 cm² each. The amount of Pt in the stack is 0.5425 g/kW, with a power density of 1.36 kW/kg. The LCI of the 48 kWel PEMFC stack is presented in Table 1. The foreground system for LCA comprises all processes related to the production of the PEMFC stack itself. This includes the main production processes for the main components, such as the manufacturing of the catalyst coated membrane (CCM), subgaskets and gas diffusion layers (GDL) which comprise the

MEA. Manufacturing processes for gaskets, bipolar plates (BPP), current collectors (CC), screws, springs, and end plates were also included in the inventory. The background system supports the foreground system described above and its processes. It deals with all material and energy flows going to and coming from the foreground system. As for secondary data, ecoinvent v3 [27] and GaBi – Sphera [26] databases were used.

### Life cycle impact assessment

The Environmental Footprint (EF3.0) method was used to evaluate the selected environmental impact categories. The selected impact categories are in line with the guidelines of one of the main documents for LCA of FCH technologies, the HyGuide [28]. In recent years, the European Commission’s Joint Research Centre started to support the EF3.0 method for evaluation of environmental impacts. The EF3.0 method includes 16 environmental impact indicators, from which the target indicators presented in Table 2 were included in the analysis. Target indicators were selected based on previous studies [5,29] and the eGHOST ecodesign strategy. For ecodesign purposes, the climate change indicator was analysed more in detail because it is the most frequent environmental indicator [30] addressed in the EU policy-relevant documents and guidelines and it is widely used in other studies related to FCH technologies [31,32].

### Life Cycle Costing framework

The cost model was based on several EU-funded projects such as IMPALA [33], MATISSE [34], and COBRA [35]. Hence, the model was based on the methodology of activity-based costing (ABC), which breaks down the batch manufacturing process into elementary process steps with the detailed contributions of raw materials, tool depreciation, labour, energy, consumables, maintenance, and quality control (Fig. 1).

### Product process description

The annual production rate is a key parameter for LCC. It depends on the application, market size and business cycle of the product (start-up, growth, maturity, decline). The selected annual production rates are 100–1000–10,000 – 50,000 stacks/year. The first value (100 units/year) corresponds to laboratory scale, while the final one (50,000 units/year) corresponds to a medium-scale plant, close to mass production. The annual production rates included the production of the following annual quantities: 561 m² (100 stacks), 5606 m² (1000 stacks), 56,056 m² (10,000 stacks), and 280,280 m² (50,000 stacks). For medium production volumes, the cost model automatically adjusted the process parameters to the new scale. Material costs corresponding to annual purchase volumes were interpolated using Equation (1), which accounts for both scale and learning effects (the latter based on three or more price quotes corresponding to different annual purchase volumes).

$$P_n = P_0 \times \text{Pr} \left( \frac{\ln \left( \frac{Q_n}{Q_0} \right)}{\ln 2} \right) \quad (1)$$

where Pn is the price at the desired annual production quantity Qn, given the initial bid price P0 at an initial quantity Q0, and a
<table><caption>Table 1 – Life cycle inventory of the 48 kWel PEMFC stack used for the base case.</caption><thead><tr><th rowspan="2">Material</th><th>Total</th><th>Amount</th><th>Share</th><th rowspan="2">Process and used database</th></tr><tr><th>Amount</th><th>per kWel</th><th>[w%]</th></tr></thead><tbody><tr><td>Silicone</td><td>1.265 kg</td><td>26.34 g</td><td>3.6%</td><td>EU-28: Silicone sealing compound (EN15804 A1-A3) Sphera</td></tr><tr><td>Stainless steel</td><td>21.623 kg</td><td>450.47 g</td><td>61.3%</td><td>DE: Stainless Steel slab (X6CrNi17) Sphera &lt;p-agg&gt;</td></tr><tr><td>Carbon cloth fibres</td><td>1.249 kg</td><td>26.02 g</td><td>3.5%</td><td>EU-28: Polyacrylonitrile Fibres (PAN) Sphera</td></tr><tr><td>PET film with glue</td><td>1.82 kg</td><td>37.92 g</td><td>5.2%</td><td>EU-28: Polyethylene terephthalate fibres (PET) Sphera</td></tr><tr><td>Platinum</td><td>0.0268 kg</td><td>0.54 g</td><td>0.1%</td><td>GLO: Platinum mix ts</td></tr><tr><td>Carbon black</td><td>0.039 kg</td><td>0.81 g</td><td>0.1%</td><td>DE: Carbon black (furnace black; general purpose) Sphera</td></tr><tr><td>PFSA (Nafion)</td><td>0.144 kg</td><td>3 g</td><td>0.4%</td><td>CA: Nafion - for use in fuel cell ts</td></tr><tr><td>Water</td><td>0.49 kg</td><td>10.21 g</td><td>1.4%</td><td>EU-28: Water (desalinated; deionised) Sphera</td></tr><tr><td>Alcohol</td><td>0.22 kg</td><td>4.58 g</td><td>0.6%</td><td>EU-28: C12-15 Alcohol (petro) Ethoxylate, 7 mol EO ERASM</td></tr><tr><td>Glass reinforced thermoplastic (GRTP)</td><td>3.8 kg</td><td>79.17 g</td><td>10.8%</td><td>RER: glass fibre reinforced plastic production, polyamide, injection moulded ecoinvent 3.7.1</td></tr><tr><td>Chromium steel</td><td>0.852 kg</td><td>17.75 g</td><td>2.4%</td><td>RER: steel production, chromium steel 18/8, hot rolled ecoinvent 3.7.1</td></tr><tr><td>Copper</td><td>0.950 kg</td><td>19.79 g</td><td>2.7%</td><td>EU-28: Copper Wire Mix (Europe 2015) DKI/ECI</td></tr><tr><td>Steel product</td><td>2.820 kg</td><td>58.75 g</td><td>8.0%</td><td>DE: EAF Steel billet/Slab/Bloom Sphera &lt;p-agg&gt;</td></tr><tr><td>Electricity</td><td>410.2 kWh</td><td>8.5 kWh</td><td>—</td><td>EU-28: Electricity grid mix Sphera</td></tr></tbody></table>

<table><caption>Table 2 – Impact categories from the EF 3.0 method used in this E-LCA study.</caption><thead><tr><th>EF impact category</th><th>Indicator</th><th>Unit</th></tr></thead><tbody><tr><td>Climate change</td><td>Global Warming Impact Potential (GWP)</td><td>kg CO<sub>2</sub> eq.</td></tr><tr><td>Acidification</td><td>Accumulated Exceedance (AE)</td><td>mol H<sup>+</sup> eq.</td></tr><tr><td>Eutrophication, terrestrial</td><td>Accumulated Exceedance (AE)</td><td>mol N eq.</td></tr><tr><td>Eutrophication, aquatic freshwater</td><td>Fraction of nutrients reaching freshwater and compartment (P)</td><td>kg P eq.</td></tr><tr><td>Eutrophication, aquatic marine</td><td>Fraction of nutrients reaching marine and compartment (N)</td><td>kg N eq.</td></tr><tr><td>Resource use, minerals and metals</td><td>Abiotic resource depletion – elements (ADP ultimate reserves)</td><td>kg Sb eq.</td></tr><tr><td>Resource use, energy carriers</td><td>Abiotic resource depletion – fossil fuels (ADP-fossil)</td><td>MJ</td></tr></tbody></table>

<figure><img src="image_4.png" /><figcaption>Fig. 1 – Schematic representation of the PEMFC cost model.</figcaption></figure>
rate of progress Pr. Pr can be derived from industry data if there are at least two sets of price bids. In evaluating stack costs, each subcomponent of the stack was considered independently, with material and process costs evaluated from cost models, supplier quotes, or bibliographic data. Cell and stack assembly was assumed to be vertically integrated (Fig. 2).

### Main process cost parameters

Process costs can be divided into six main cost categories: infrastructure and surface costs, energy and consumables costs, labour costs, maintenance costs, raw materials, and scrap rate and processing losses. Some of their parameters depend on the location of the plant, such as labour costs and energy costs. The cost of infrastructure was evaluated considering the floor area (m²) of each machine and multiplied by a factor of 3 to determine the area of the process building (m²), and by a factor of 2 for the equipment and the administration building. It was assumed that the plant is located in Europe and the infrastructure costs (rent, cleaning, lighting, insurance, etc.) for these buildings are 200 €/m²/year. The electricity price values depend on the annual consumption and are given without refundable taxes and levies (Table 3).

Labour costs were retrieved from the Eurostat database, which provides average labour costs per hour in EU member states for 2020 [37], with labour costs per hour ranging from 6.5 €/h in Bulgaria to 45.8 €/h in Denmark, being 23 €/h in Spain. The number of working hours per year in the production plant were adjusted depending on the organization of shift work (1 × 8, 2 × 8, 3 × 8, 5 × 8), as well as the wage supplements for shift work (Table 4).

<table><caption>Table 3 – Electricity price in industry without refundable taxes and levies (source: Eurostat [36]).</caption><thead><tr><th></th><th>20-500<br>MWh/yr</th><th>0.5-2<br>GWh/yr</th><th>2-20<br>GWh/yr</th><th>20-70<br>GWh/yr</th><th>70-150<br>GWh/yr</th></tr></thead><tbody><tr><th>Spain</th><td>99</td><td>83</td><td>65</td><td>61</td><td>53</td></tr><tr><th>Euro area</th><td>101</td><td>84</td><td>72</td><td>63</td><td>55</td></tr></tbody></table>

<table><caption>Table 4 – Labour input according to shift work scheme.</caption><thead><tr><th>Shift work<br>scheme</th><th>Number of effective<br>days per year</th><th>Number of effective<br>hours per year</th></tr></thead><tbody><tr><td>1x8</td><td>198</td><td>1584</td></tr><tr><td>2x8</td><td>198</td><td>3168</td></tr><tr><td>3x8</td><td>198</td><td>4752</td></tr><tr><td>5x8</td><td>330</td><td>7920</td></tr></tbody></table>

It was assumed that the calculation of effective days per year considers the necessary maintenance time, which was assumed to be 35 days per year. The organization of work can vary from one process step to another, especially if there are large time differences between the individual production steps. Salary premiums were considered for morning/afternoon, morning/afternoon/night, or morning/afternoon/night/weekend. Employment of the various socio-professional categories was calculated based on the working time related to the use of equipment, implementation of time ratios and supporting work tasks. In the category of investment and depreciation costs, the prices of the tools were taken from quotations and multiplied by 1.3 to consider the installation costs. The CEPCI [26] index for chemical plant costs was used

<figure><img src="image_5.png" /><figcaption>Fig. 2 – Vertical manufacturing integration of a PEMFC stack.</figcaption></figure>
to update the prices determined a few years ago [38]. Capital depreciation was calculated based on a depreciation period of 20 years for buildings, 10 years for equipment, 10 years for furniture, and 5–10 years for tools. Annual maintenance costs of 4% of the purchase price of the machine were included if the machine is used continuously, and 3% of the purchase price of the machine in other cases. If the machine is used below its rated load, the maintenance costs were assumed to be proportional to the effective machine time. Regarding the scrap rate and raw material loss cost category, the scrap rate was set according to the production rate (Table 5).

Additionally, the loss of raw materials was 20% for chemicals and 30% of cutting waste for metal and mica sheets. For process tooling, the various tooling manufacturers involved in the process line were consulted to determine the specifications of the appropriate equipment: capital cost, labour, consumables, maintenance rate, and floor space requirements. Quotes from raw material suppliers and data from the Metals and Critical Materials Market Database [39] allowed the construction of a raw material database. Cost requests were made for three or more production rates to determine the relationship between price and quantity purchased using Equation (1).

The influence of the selected production rates on process and materials data is presented in Table 6. The cost value for the MEA materials and assembly equipment were retrieved from Ref. [40], with Pt catalyst and metallic bipolar plate cost from the CEA database [41]. The value of the Pt catalyst includes (i) the value of the precious metal (market price), which can vary widely [42], and (ii) the markup costs, which cover the production costs and the indirect costs of the manufacturer. According to recent information from suppliers, these costs amount to 10–20 €/g Pt, depending on the quantity. The Pt cost (date June 04, 2021) is 33.16 €/g. The catalyst price was determined by Equation (2) which was derived based on results of a EU funded project MATISSE [34]. The Pt catalyst price

is composed of two parts: (i) a first part related to the Pt market price, and (ii) a second part related to the purchased quantity, with the effect described by the “learning curve” part.

$$P_{Pt}(€/g) = 33.16 + 20 \times P_r \left( \frac{\ln\left(\frac{Q_{Pt}}{\ln 2}\right)}{\ln 2} \right) \quad (2)$$

with $P_r$ (progress ratio) of 0.9 and $Q_{Pt}$ standing for the annual amount of Pt. Table 7 shows the main characteristics of the PEMFC stack manufacturing plant for different production rates.

## Social Life Cycle Assessment framework

S-LCA is a methodology to estimate the potential social impacts of product systems through their supply chain. In this case, in line with the goal of the eGHOST project, the focus was placed on identifying the most relevant social hotspots along the supply chain of the PEMFC stack to further support the prioritisation of ecodesign actions to be subsequently developed. Results must therefore be interpreted in a relative manner within the product system boundaries, with no benchmarking purposes across other technologies. Updated guidelines for S-LCA of products were developed within the framework of the United Nations Environment Programme (UNEP) [43] and were considered in the assessment. The FU for the S-LCA, in line with the aforementioned LCA and LCC studies, was also defined as one manufactured 48 kWel stack, without BoP components [44].

Three specific supply-chain tiers were modelled for the assessed product system (Fig. 3): tier 1 for the stack manufacturing plant itself, tier 2 for the plants related to the production of the components and energy flows required by the stack manufacturing plant, and tier 3 for the plants related to the material and energy flows required by the components manufacturing plants. Spain was set as the manufacturing country in tier 1 to facilitate future comparative studies [15,45]. The identification of the countries involved in the supply chain considers the protocol available in Ref. [46]. Global trade data was acquired and analysed for every component included in tier 2. If the export-import balance resulted positive (more

<table><caption>Table 5 – Scrap rate according to manufacturing scale.</caption><thead><tr><th>Process steps</th><th>150 m²/yr.</th><th>15,000 m²/yr.</th></tr></thead><tbody><tr><td>Cell manufacture</td><td>18%</td><td>4%</td></tr><tr><td>Stack conditioning</td><td>10%</td><td>2%</td></tr></tbody></table>

<table><caption>Table 6 – PEMFC BoM and unit price according to quantity purchased.</caption><thead><tr><th rowspan="2">BoM</th><th rowspan="2"></th><th rowspan="2">Quantity</th><th colspan="4">Unit Price (€/unit)</th></tr><tr><th>stacks/yr</th><th>100</th><th>1000</th><th>10,000</th><th>50,000</th></tr></thead><tbody><tr><td rowspan="3">Components<br>Catalyst</td><td>Materials</td><td>per stack</td><td>Unit \ m²/yr</td><td>560</td><td>5600</td><td>56,000</td><td>280,000</td></tr><tr><td>PtC (46.9% Pt)</td><td>26</td><td>g Pt</td><td>57.0</td><td>50.0</td><td>45.0</td><td>42.0</td></tr><tr><td>Nafion D2020 (22%)</td><td>0.018</td><td>kg</td><td>1163</td><td>678</td><td>395</td><td>271</td></tr><tr><td></td><td>Propanol</td><td>0.11</td><td>kg</td><td>0.9</td><td>0.8</td><td>0.7</td><td>0.6</td></tr><tr><td>GDL</td><td>GDL</td><td>13.96</td><td>€/m²</td><td>512.7</td><td>149.5</td><td>43.6</td><td>18.4</td></tr><tr><td>Membrane<br>frame</td><td>Membrane</td><td>6.0</td><td>€/m²</td><td>835.7</td><td>321.4</td><td>123.6</td><td>63.4</td></tr><tr><td>BPP</td><td>PTFE</td><td>21.0</td><td>€/m²</td><td>1.4</td><td>1.3</td><td>1.2</td><td>1.2</td></tr><tr><td></td><td>Steel roll</td><td>17.36</td><td>kg</td><td>5.0</td><td>5.0</td><td>5.0</td><td>5.0</td></tr><tr><td></td><td>Coating</td><td>8.4</td><td>g</td><td>0.8</td><td>0.8</td><td>0.8</td><td>0.8</td></tr><tr><td>End plates</td><td>Stainless steel</td><td>1</td><td>unit/stack</td><td>101.0</td><td>46.0</td><td>41.0</td><td>32.0</td></tr><tr><td>Assembly equipment</td><td>Assembly hardware current<br>collector, clamping,<br>compression bar</td><td>1</td><td>unit/stack</td><td>54.0</td><td>50.0</td><td>47.0</td><td>45.0</td></tr></tbody></table>
<table><caption>Table 7 – PEMFC stack manufacturing plant economic information.</caption><thead><tr><th>Process</th><th>Production rate<br>(stacks/yr)</th><th>100</th><th>1000</th><th>10,000</th><th>50,000</th></tr></thead><tbody><tr><td>Bill of materials</td><td>1400 k€</td><td></td><td>5586 k€</td><td>27,703 k€</td><td>98,183 k€</td></tr><tr><td>Operating shift</td><td>1 × 8</td><td></td><td>1 × 8</td><td>3 × 8</td><td>3 × 8</td></tr><tr><td>Cells (MEA) manufacturing<br>process</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Catalyst preparation</td><td>Ball milling</td><td>1 line</td><td>2 lines</td><td>2 lines</td><td>4 lines</td></tr><tr><td>Layers deposition</td><td>Screen printing</td><td>1 tool</td><td>1 tool</td><td>4 tools</td><td>18 tools</td></tr><tr><td>Hot press</td><td>Hot press</td><td>1 tool</td><td>1 tool</td><td>5 tools</td><td>9 tools</td></tr><tr><td>Cutting</td><td>Cutting</td><td>1 tool</td><td>1 tool</td><td>1 tool</td><td>3 tools</td></tr><tr><td>Control</td><td>Control (IR, leak test ...)</td><td>1 tool</td><td>1 tool</td><td>2 tools</td><td>3 tools</td></tr><tr><td>Bipolar plate (BPP)<br>manufacturing process</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Metal foil preparation</td><td>Decoiling, flattening</td><td>1 tool</td><td>2 tools</td><td>2 lines</td><td>4 lines</td></tr><tr><td>Forming</td><td>stamping, cutting</td><td>1 tool</td><td>1 tool</td><td>2 tools</td><td>9 tools</td></tr><tr><td>Welding</td><td>laser welding</td><td>1 tool</td><td>7 tools</td><td>6 tools</td><td>26 tools</td></tr><tr><td>Coating</td><td>coating</td><td>1 tool</td><td>1 tool</td><td>2 tools</td><td>13 tools</td></tr><tr><td>Control</td><td>Control (IR, leak test ...)</td><td>1 tool</td><td>1 tool</td><td>1 tool</td><td>3 tools</td></tr><tr><td>Stack assembly</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Assembly</td><td>Automate</td><td>1 tool</td><td>2 tools</td><td>2 tools</td><td>10 tools</td></tr><tr><td>Press</td><td>Press</td><td>1 tool</td><td>1 tool</td><td>1 tool</td><td>2 tools</td></tr><tr><td>Test</td><td>bench</td><td>1 tool</td><td>1 tool</td><td>1 tool</td><td>3 tools</td></tr><tr><td>Capital investment</td><td>(equipment)</td><td>7856 k€</td><td>13,842 k€</td><td>24,561 k€</td><td>111,750 k€</td></tr><tr><td>Building cost</td><td></td><td>250 k€/yr</td><td>580 k€/yr</td><td>876 k€/yr</td><td>3870 k€/yr</td></tr><tr><td>Process build. surface</td><td></td><td>400 m²</td><td>1500 m²</td><td>2190 m²</td><td>9445 m²</td></tr><tr><td>Tooling, consumables</td><td></td><td>13 k€/yr</td><td>134 k€/yr</td><td>1340 k€/yr</td><td>6740 k€/yr</td></tr><tr><td>Energy consumption</td><td></td><td>100 MWh</td><td>1058 MWh</td><td>11,000 MWh</td><td>52,813 MWh</td></tr><tr><td>Maintenance cost</td><td></td><td>292 k€/yr</td><td>640 k€/yr</td><td>1770 k€/yr</td><td>10,327 k€/yr</td></tr><tr><td>Manpower</td><td></td><td>32 k€/yr</td><td>512 k€/yr</td><td>1647 k€/yr</td><td>2320 k€/yr</td></tr><tr><td>Labour total operators,<br>technicians, managers</td><td></td><td>2 operators,<br>1 technician, 1 manager</td><td>5 operators,<br>2 technicians,<br>1 manager</td><td>17 operators,<br>4 technicians,<br>2 managers</td><td>80 operators,<br>12 technicians,<br>7 managers</td></tr></tbody></table>

exports than imports measured in economic value), then the component under scrutiny was considered to be manufactured in Spain. If this was not the case, the main country-specific exporter was set as the component manufacturing country. The result of this step is therefore one manufacturing country for each of the product components. After the identification of the manufacturing countries for every component in tier 2, a similar procedure was followed for the materials included in tier 3. Each component manufacturing country was set as declarant for every material flow within that component. Afterwards, its global trade data was acquired and analysed. If the export-import balance turned out positive, then the material under scrutiny was assumed to be manufactured in the same country as the component. If this was not the case, the most relevant country-specific exporters were identified according to Ref. [46]. The result of this step is a mix of manufacturing countries for each of the materials in tier 3. Trade information was gathered mainly from the UN Comtrade database [47], using the commodity code that better adjusts to the component/material characteristics. When the information available on this site was not considered to be specific enough for a particular component/material, alternative sources were explored (such as the Eurostat database [36]). The inventories used for E-LCA and LCC arose as the main source of data for the social LCIs, along with the use of the PSILCA database [48]. At each tier, the working hours per FU were directly or indirectly quantified for each block in Fig. 3. When working hours were not directly available for an entity (i.e. for those related to

energy flows and materials), they were estimated based on its attached economic flows by using country- and sector-specific factors from the PSILCA database. When such monetary values were required, they were retrieved from the data used in the LCC section for an annual production of 10,000 stacks.

### Social impacts evaluation procedure

The evaluation method employed for S-LCIA follows the procedure explained in Valente et al. [45]. Social indicators were estimated from (i) the working hours (i.e. activity variable) at each plant *p* per FU ($W_p$), and (ii) the risk factor specific to each social indicator *j* and plant *p* ($R_{j,p}$, expressed in medium risk hours –mrh– per working hour for negative social impacts, and in medium opportunity hours –moh– per working hour for positive social impacts). Each social indicator ($S_j$, in mrh per FU) was therefore assessed according to Equation (3).

$$S_j = \sum_{p=1}^{n} W_p \bullet R_{j,p} \qquad (3)$$

where *n* is the number of plants included in the product system. If working hours were not available directly, they were inferred from the economic flow associated with that block according to Equation (4).

$$W_p = V_p \bullet W'_p \qquad (4)$$

where $V_p$ is the economic value in United States Dollars (USD) per FU linked to the plant *p*, and $W'_p$ is the number of working
<figure><img src="image_6.png" /><figcaption>Fig. 3 – Inventory segmentation for S-LCA.</figcaption></figure>

hours per USD for the plant *p*, which can be found –for the country and sector associated with this plant– in the PSILCA database [48].

### Social impact indicators

The selection of stakeholders, impact categories, and social indicators addressed in this study (Fig. 4) was based on the specific goal and characteristics of the eGHOST project, literature findings from previous S-LCA studies on FCH and energy systems [15,45,49,50], available guidelines [43,48,51], and alignment with the United Nations Sustainable Development Goals (SDGs).

Regarding the stakeholder “workers”, the impact categories of child labour, forced labour, discrimination, and fair salary were selected. These have high relevance when dealing with multiregional supply chains. The social indicators of children in employment (total) and gender wage gap were chosen based on the available S-LCA literature on hydrogen systems [45,51]. The frequency of forced labour indicator was selected as it involves a broad-spectrum accounting for human trafficking, debt bondage, forced or servile marriage, and the sale or exploitation of children [48]. This is consistent with the SDG target 8.7, which calls to “take immediate and effective measures to eradicate forced labour, end modern slavery and human trafficking” [52]. Concerning the stakeholder “society”, the impact category of “contribution to economic development” was selected to assess the potential economic growth that the involved countries could experience with the diffusion of PEMFC technologies. Thus,

contribution of the sector to economic development was selected as the only indicator with a positive connotation. Still within the stakeholder “society”, health expenditure was selected as the social indicator for the impact category “health and safety” based on eGHOST project goals and specific literature [15,45,51]. To build the social life-cycle inventory of the PEMFC stack (Fig. 5, with monetary values expressed in 2015 United States dollars), the supply chain of the product was segmented into the following plants delivering.

* Product: PEMFC stack.

* Components: MEA, bipolar/end plates, gaskets, connectors, and current collectors.

* Materials: platinum, PFSA (perfluorosulfonic acid), polyethylene terephthalate (PET), thermoactive adhesives, carbon-containing compounds, stainless steel, glass-fibre-reinforced thermoplastic, and silicone.

### Ecodesign of FCH technologies

Ecodesign strategies consist of integrating environmental/sustainability protection criteria over a service or a product life cycle. The main goal of ecodesign is to anticipate and minimise negative environmental impacts (of manufacturing, use and EoL of products) [53]. Ecodesign also keeps a product quality level according to its ideal usage and at the same time does not compromise its functionality [54].

The ecodesign of FCH technologies is currently being addressed within the framework of the eGHOST project [55].
<table><caption>Fig. 4 – Social life-cycle indicators addressed in the study.</caption><thead><tr><th>Stakeholder</th><th>Impact category</th><th>Indicator</th></tr></thead><tbody><tr><td rowspan="4">Workers</td><td>Child labour</td><td>Child labor, total</td></tr><tr><td>Fair salary</td><td>FS = f(Living wage gap (LB), Living wage gap (UB), Living wage per month, Minimum wage per month, Sector average wage per month)</td></tr><tr><td>Forced labour</td><td>Frequency of forced labour</td></tr><tr><td>Discrimination</td><td>Gender wage gap</td></tr><tr><td rowspan="2">Society</td><td>Contribution to economic development</td><td>Contribution of the sector to economic development</td></tr><tr><td>Health and safety</td><td>Health expenditure</td></tr></tbody></table>

The ecodesign strategy addresses different levels: product component, product structure, and product system [54]. In PEMFC technologies, Pt is a key material in the product component level when it comes to implementing ecodesign actions that include (i) the selection of low-impact material – use of recycled Pt, and (ii) the reduction of material use – lower Pt loadings based on technology development. For the base case, virgin Pt was considered as an input material in PEMFC stack manufacturing, thus serving as a benchmark to subsequently explore the effect of reduced Pt loading and the use of recycled Pt in manufacturing of PEMFC stack. In this work, as a preliminary assessment of ecodesign actions in terms of carbon footprint effects, the inputs for reduced Pt loadings were obtained from FCH technology experts, partners within the eGHOST project, and references from relevant

documents [56,57]. Moreover, a process for Pt recycling was implemented in the LCA model in aggregated form based on results of the EU-funded project BEST4Hy [21], in which recycling of Pt with current and novel recycling technologies is conducted on laboratory scale. The carbon footprint of recycled Pt (including additional energy consumption, secondary waste flows, additional support materials, emissions, etc.) from the BEST4Hy project is 14.8 kg CO₂ eq./g [58,59], while virgin Pt production from the GaBi – Sphera database is 28.2 kg CO₂ eq./g. Within the BEST4Hy project, the objective is to test if using 95% of the mass input from recycled Pt (Clean Hydrogen JU 2024 target [2]) in the PEMFC stack production would be technically and economically feasible, and if the PEMFC stack using recycled Pt would achieve the same performance. For this purpose, the same ratio was considered in

<figure><img src="image_7.png" /><figcaption>Fig. 5 – Supply-chain inventory of the 48 kWel PEMFC stack.</figcaption></figure>
<figure><img src="image_8.png" /><figcaption>Fig. 6 – LCA model of the 48 kWel PEMFC stack manufacturing phase.</figcaption></figure>

this study when exploring the use of recycled Pt as an illustrative ecodesign action. In particular, in addition to the base case with only virgin Pt input and 0.465 mg Pt/cm², two concepts were defined based on Pt loading reduction: (i) realistic concept, and (ii) optimistic concept. In each concept, two scenarios were assessed: (i) 100% virgin Pt use, and (ii) 95% of

recycled Pt and 5% of virgin Pt in the manufacturing phase. Pt loading in the realistic concept was assumed to be 0.235 mg Pt/cm² [56,57], and 0.125 mg Pt/cm² in the optimistic concept [2,60]. The ecodesign principle in this study was used just at the product component level to demonstrate the application of the methodology as a further step in designing sustainable

<table><caption>Table 8 – Absolute values of environmental indicators for 48 kWel PEMFC stack manufacturing.</caption><thead><tr><th></th><th>EF 3.0<br>Acidification<br>[mol H<sup>+</sup> eq.]</th><th>EF 3.0 Climate<br>Change - total<br>[kg CO<sub>2</sub> eq.]</th><th>EF 3.0<br>Eutrophication,<br>freshwater<br>[kg P eq.]</th><th>EF 3.0<br>Eutrophication,<br>marine<br>[kg N eq.]</th><th>EF 3.0<br>Eutrophication,<br>terrestrial<br>[mol N eq.]</th><th>EF 3.0<br>Resource<br>use,<br>fossils [MJ]</th><th>EF 3.0 Resource<br>use,<br>mineral and<br>metals<br>[kg Sb eq.]</th></tr></thead><tbody><tr><td>PEMFC stack, total</td><td>20.8</td><td>1160</td><td>0.005</td><td>1.44</td><td>15.4</td><td>13,800</td><td>0.052</td></tr><tr><td>Electricity</td><td>3.32E-01</td><td>1.53E+02</td><td>4.41E-04</td><td>7.45E-02</td><td>7.82E-01</td><td>2.74E+03</td><td>4.13E-05</td></tr><tr><td>Platinum</td><td>1.96E+01</td><td>7.37E+02</td><td>6.54E-05</td><td>1.24E+00</td><td>1.36E+01</td><td>8.81E+03</td><td>4.52E-02</td></tr><tr><td>Ionomer (Nafion)</td><td>1.92E-04</td><td>1.38E+02</td><td>1.36E-07</td><td>3.97E-05</td><td>4.40E-04</td><td>4.04E+02</td><td>2.77E-08</td></tr><tr><td>Carbon black</td><td>2.20E-04</td><td>9.48E-02</td><td>1.26E-07</td><td>1.39E-05</td><td>1.48E-04</td><td>2.52E+00</td><td>1.49E-08</td></tr><tr><td>Steel</td><td>2.53E-03</td><td>1.06E+00</td><td>3.39E-06</td><td>6.59E-04</td><td>7.03E-03</td><td>1.27E+01</td><td>4.02E-07</td></tr><tr><td>Stainless steel</td><td>5.92E-01</td><td>7.29E+01</td><td>7.90E-05</td><td>5.54E-02</td><td>6.13E-01</td><td>8.18E+02</td><td>4.75E-03</td></tr><tr><td>Alcohol</td><td>1.52E-03</td><td>5.49E-01</td><td>9.55E-07</td><td>2.68E-04</td><td>2.85E-03</td><td>1.56E+01</td><td>1.48E-07</td></tr><tr><td>Copper</td><td>3.52E-02</td><td>3.66E+00</td><td>2.09E-05</td><td>4.67E-03</td><td>5.14E-02</td><td>3.60E+01</td><td>1.88E-03</td></tr><tr><td>Polyacrylonitrile fibres<br>(PAN)</td><td>1.66E-02</td><td>6.40E+00</td><td>8.68E-06</td><td>6.67E-03</td><td>6.65E-02</td><td>1.41E+02</td><td>6.36E-07</td></tr><tr><td>Polyethylene<br>terephthalate fibres<br>(PET)</td><td>7.7846E-03</td><td>4.98E+00</td><td>1.85E-05</td><td>2.12E-03</td><td>2.31E-02</td><td>1.35E+02</td><td>5.96E-07</td></tr><tr><td>Silicone</td><td>2.82E-02</td><td>8.86E+00</td><td>1.47E-05</td><td>6.10E-03</td><td>6.60E-02</td><td>1.41E+02</td><td>1.71E-04</td></tr><tr><td>Water (desalinated;<br>deionised)</td><td>1.19E-06</td><td>5.74E-04</td><td>2.98E-08</td><td>4.42E-07</td><td>3.85E-06</td><td>9.31E-03</td><td>1.40E-10</td></tr><tr><td>Glass fibre reinforced<br>plastic</td><td>1.37E-01</td><td>3.35E+01</td><td>3.10E-03</td><td>4.41E-02</td><td>2.21E-01</td><td>5.24E+02</td><td>6.53E-05</td></tr><tr><td>Chromium steel</td><td>2.38E-02</td><td>3.78E+00</td><td>1.33E-03</td><td>4.48E-03</td><td>4.80E-02</td><td>5.15E+01</td><td>1.34E-04</td></tr></tbody></table>
<table><caption>Table 9 – Relative contribution of electricity and materials to total environmental impacts for manufacturing one 48 kWel PEMFC stack.</caption><thead><tr><th></th><th>EF 3.0<br>Acidification<br>[mol H<sup>+</sup> eq.]</th><th>EF 3.0 Climate<br>Change - total<br>[kg CO<sub>2</sub> eq.]</th><th>EF 3.0<br>Eutrophication.<br>freshwater<br>[kg P eq.]</th><th>EF 3.0<br>Eutrophication.<br>marine<br>[kg N eq.]</th><th>EF 3.0<br>Eutrophication.<br>terrestrial<br>[mol N eq.]</th><th>EF 3.0<br>Resource use.<br>fossils [MJ]</th><th>EF 3.0<br>Resource use.<br>Min.&met.<br>[kg Sb eq.]</th></tr></thead><tbody><tr><td><strong>PEMFC stack - total</strong></td><td>100%</td><td>100%</td><td>100%</td><td>100%</td><td>100%</td><td>100%</td><td>100%</td></tr><tr><td>Electricity</td><td>1.6%</td><td>13.2%</td><td>8.7%</td><td>5.2%</td><td>5.1%</td><td>19.9%</td><td>0.1%</td></tr><tr><td>Platinum</td><td>94.2%</td><td>63.5%</td><td>1.3%</td><td>86.1%</td><td>88.3%</td><td>63.8%</td><td>86.6%</td></tr><tr><td>Ionomer (Nafion)</td><td>0.0%</td><td>11.9%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>2.9%</td><td>0.0%</td></tr><tr><td>Carbon black</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td></tr><tr><td>Steel</td><td>0.0%</td><td>0.1%</td><td>0.1%</td><td>0.0%</td><td>0.0%</td><td>0.1%</td><td>0.0%</td></tr><tr><td>Stainless steel</td><td>2.8%</td><td>6.3%</td><td>1.6%</td><td>3.8%</td><td>4.0%</td><td>5.9%</td><td>9.1%</td></tr><tr><td>Alcohol</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.1%</td><td>0.0%</td></tr><tr><td>Copper</td><td>0.2%</td><td>0.3%</td><td>0.4%</td><td>0.3%</td><td>0.3%</td><td>0.3%</td><td>3.6%</td></tr><tr><td>Polyacrylonitrile<br>fibres (PAN)</td><td>0.1%</td><td>0.6%</td><td>0.2%</td><td>0.5%</td><td>0.4%</td><td>1.0%</td><td>0.0%</td></tr><tr><td>Polyethylene<br>terephthalate<br>fibres (PET)</td><td>0.0%</td><td>0.4%</td><td>0.4%</td><td>0.1%</td><td>0.2%</td><td>1.0%</td><td>0.0%</td></tr><tr><td>Silicone</td><td>0.1%</td><td>0.8%</td><td>0.3%</td><td>0.4%</td><td>0.4%</td><td>1.0%</td><td>0.3%</td></tr><tr><td>Water (desalinated;<br>deionised)</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td><td>0.0%</td></tr><tr><td>Glass fibre reinforced<br>plastic</td><td>0.7%</td><td>2.9%</td><td>61.0%</td><td>3.1%</td><td>1.4%</td><td>3.8%</td><td>0.1%</td></tr><tr><td>Chromium steel</td><td>0.1%</td><td>0.3%</td><td>26.2%</td><td>0.3%</td><td>0.3%</td><td>0.4%</td><td>0.3%</td></tr></tbody></table>

<figure><img src="image_9.png" /><figcaption>Fig. 7 – LCC PEMFC cost distribution according to the production rate (values for one PEMFC stack).</figcaption></figure>
FCH products. At this point, for illustrative purposes, only the carbon footprint indicator was assessed for the considered ecodesign actions.

## Results and discussion

In the first part of this section potential environmental impacts of the PEMFC manufacturing phase are presented, followed by life-cycle costs and social impacts. Preliminary ecodesign results at the product component level, addressing Pt use in the PEMFC manufacturing phase, are then discussed.

### Environmental impacts of the PEMFC stack

Potential environmental impacts of the 48 $kW_{el}$ PEMFC stack manufacturing are presented and assessed separately for each component and material used in the production process of the stack. The E-LCA model in GaBi software environment for one PEMFC stack consists of different materials used in the membrane, catalytic ink, sub-gaskets, GDL, and BPP manufacturing phase (Fig. 6). The electricity needed for all manufacturing processes was included. Waste streams and energy losses related to the manufacturing phase were partly included due to gaps in the inventory.

Table 8 shows the absolute values of the environmental impact indicators for acidification, climate change, eutrophication, and resources consumption for the 48 $kW_{el}$ PEMFC stack manufacturing. For a more detailed analysis and a hotspot analysis, the results for the relative contribution of electricity and materials to total environmental impacts of the production phase were analysed (Table 9). Colours from green (low environmental impact) to orange and red (high environmental impact) were used to get immediate impression regarding the significance of the environmental impact contribution.

From results presented in Tables 8 and 9, we can see that the carbon footprint of the 48 $kW_{el}$ PEMFC stack manufacturing is 1160 kg $CO_2$ eq., which corresponds to 24.2 kg $CO_2$ eq. per $kW_{el}$. Electricity and, mainly, Pt production were found to have the highest contribution to the climate change indicator. Namely, Pt and electricity represent 63.5% and 13.2% of the carbon footprint, respectively. The third most influential material in the climate change indicator was found to be the ionomer, with a relative contribution of 11.9%. Glass fibre reinforced plastic was found to have the highest impact contribution to freshwater eutrophication, with 61.0% relative contribution, followed by chromium steel (26.2%) and electricity (8.7%). Except for the latter indicator, Pt arose as the main source of impact in all environmental impact indicators (despite the total mass share of Pt in the whole PEMFC stack being only 0.074%), generally followed by electricity.

<figure><img src="image_10.png" /><figcaption>Fig. 8 – BoM cost distribution according to production rate (values for one PEMFC stack).</figcaption></figure>
Life cycle costs of the PEMFC stack

The cost of the stack is very dependent on the production rate. The transition from laboratory (100 stacks/year) to industrial scale (50,000 stacks/year for a medium size company) enables reducing costs more than three times by acting on both process and material costs. In Fig. 7, the distribution of costs along the manufacturing process is presented for four different production rates on an annual basis. Comparing the total costs of the PEMFC stack for different production rates, the biggest stepwise reduction (70%) was found when the production rate was increased 10-times from laboratory scale to 1000 stacks/year. Further increase in the production rate leads to further reduction in total costs for one PEMFC stack. At a production rate of 50,000 stacks/year, the estimated cost is just 7% of the cost of the stack at a production rate of 100 stacks/year. The biggest reduction in costs comes in the BPP and MEA production processes.

In the case of laboratory production rate, BoM costs represent the biggest share (44.1%) in total costs per stack. When scaling the production rate to 50,000 stacks/year, the absolute BoM costs for one PEMFC stack are reduced from

14,001 €/stack to 1964 €/stack, but the share of BoM costs in the total stack cost is increased from 44.1% to 88.0%. Going more into detail in the analysis of BoM costs (Fig. 8), it was found that the Pt cost has a much higher share at higher production rates. On the laboratory scale the share of Pt cost represents 11.1% of total BoM costs, while 24.2%, 43.8% and 57.5% at rates of 1,000, 10,000 and 50,000 stacks/year, respectively. That means particular attention should be paid to reducing the amount of Pt in the stack and recovering the Pt at the end of the stack's life [21]. It could be possible to recover also metal BPP or the ionomer, but the cost-effectiveness so far remains unclear. Nevertheless, several analyses of Pt recycling have already been conducted [20,61] and 80–95% of the initial Pt load in the stack is foreseen to be recovered [21].

The cost of recycling should be considered, as well as the cost of the supply chain of the salvage. Based on current practice, the salvage expects to be paid by the recycling company at about 70%–75% of the total value of recycled Pt, with the remaining Pt value going to the recycling company as a payment for the recycling process. Due to Pt market price volatility, it is unlikely that the Pt price will be the same at

<figure><img src="image_11.png" /><figcaption>Fig. 9 – Contribution to the potential social impacts for the 48 kWel PEMFC stack.</figcaption></figure>
<figure><img src="image_12.png" /><figcaption>Fig. 10 – Potential carbon footprint reduction through reduced platinum loading and/or the use of recycled platinum.</figcaption></figure>

system purchase and 10 years later at the time of recycling. For the baseline LCC, the price of Pt was held constant at the purchase price used for the catalyst within a new stack (50 €/g). The amount of Pt in the 48 kW PEMFC stack is 26.8 g, so the recycling credit would therefore be 819 €/stack. For LCC purposes, the production and EoL steps were considered in the scope of the study. Cash flows that were realized during the lifetime of the product were discounted. Considering the 10 years lifetime of a stack and a discount rate of 8% [41] (usual for innovative processes), the discounted value linked to the recycled Pt is 410 € per stack (Fig. 7). The relative reduction in the stack production cost including Pt recycling credits is 1.3%, 4.2%, 12.9% and 18.4% for production rates of 100, 1,000, 10,000 and 50,000 stack/year, respectively.

## Social life-cycle impacts of the PEMFC stack

Regarding the S-LCIA results, process contribution to the selected social indicators is shown in Fig. 9. In all social indicators with a negative connotation, Pt production in South Africa was identified as the main social hotspot despite the small amount of material embodied in the product. In particular, for child labour, Pt production was found to account for more than 95% of the impact. This is due to both the high economic flow that Pt entails due to its high unit costs (i.e. price per unit of mass) and the sector-specific risks associated with the production country. Additionally, bipolar and end plates production in Spain was found to account for 25–30% of the fair salary and forced labour impacts. In this case, the interpretation of the results is different, as they are driven by the high number of working hours attributed to this plant (which are likewise conditioned by the high mass ratio of these components) and not to country-specific relevant risks. The production of carbonaceous compounds in China arose as the most relevant contributor to economic

development, the only positive social indicator assessed. Overall, it was found that material production factories (tier 3) are more relevant to social impacts than the facilities belonging to tiers 1 (final product) and 2 (components). Finally, it should be noted that the social risks associated with energy flows were found to be negligible.

## Ecodesign concept with recycled and reduced loading of platinum

Ecodesign actions based on reduced Pt loading and recycled Pt use in production show a large potential in carbon footprint reduction. If 95% of all Pt mass input in the base case was recycled Pt (instead of virgin) with 14.8 kg CO₂ eq./g, then the reduction in the carbon footprint of manufacturing one PEMFC stack would be 29%. The carbon footprint of one 48 kWel would be reduced from 1160 kg CO₂ eq. to 829 kg CO₂ eq., considering all emissions, energy inputs, waste streams, and other supporting materials and solutions needed in the recycling process (Fig. 10). Further, the carbon footprints calculated for a realistic (short-term) and an optimistic (long-term) concept with reduced Pt loading suggest a climate change reduction of 31% and 46%, respectively, compared to the base case. When additionally considering the use of recycled Pt (95% recycled Pt and 5% virgin Pt) in the realistic and optimistic concepts, the potential for climate change reduction increases to 46% in the realistic concept and 54% in the optimistic concept (Fig. 10).

## Conclusions

To discuss the sustainability of the manufacturing phase of PEMFC stacks, life-cycle environmental, economic, and social aspects need to be addressed. Combining these three pillars
allowed us to perform a thorough analysis and identify
important hotspots not only from an environmental
perspective, but also from an economic and social standpoint.

In the environmental assessment, Pt was found to account for 63.5% of the total carbon footprint (1160 kg CO₂ eq.) to manufacture the 48 kWel PEMFC stack. A high relative contribution of Pt was also found for all other environmental indicators assessed, except for freshwater eutrophication.

When evaluating life-cycle costs, Pt costs were found to account for a significant share of total manufacturing costs and, at a high production rate, an even larger share of BoM costs. At a laboratory-scale production rate (100 stacks/year), Pt costs represent 4.9% of total life-cycle costs (11.1% of BoM costs), as other materials (such as the membrane - ionomer, the GDL - carbon cloth) and processes (such as the BPP manufacturing process) account for the majority of the costs due to the small amounts of specifically purchased materials to manufacture and cut the components only for the needs of PEMFC stack production. At an annual production rate of 50,000 stacks, the cost of these materials drops significantly. The relative share of Pt in the total production cost (2233 €) for a PEMFC stack is as high as 50.6% at a production rate of 50,000 stacks/year.

Pt production in South Africa was also identified as a social hotspot, accounting for the largest share of all social indicators with a negative connotation. With the illustrative ecodesign approach at the product component level, significant impact reductions could be achieved through lower Pt loading and the use of recycled Pt, as shown in terms of carbon footprint for the environmental dimension (up to 54% carbon footprint reduction in an optimistic product concept).

Overall, Pt is a sustainability hotspot of the PEMFC technology. While ecodesign is often applied to widely commercialised products, this study shows – through an illustrative approach based only on Pt and carbon footprint performance – that it would also be very beneficial when addressing emerging technologies before market deployment. In this sense, ecodesign actions based on reduced Pt loading and recycled Pt use could reduce 29–54% of the carbon footprint of the PEMFC stack, which is expected to be enhanced when considering additional ecodesign actions defined within the scope of the eGHOST project.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was done within the eGHOST project, which has
received funding from the Fuel Cells and Hydrogen 2 Joint
Undertaking (now Clean Hydrogen Partnership) under Grant
Agreement No 101007166. This Joint Undertaking receives
support from the European Union's Horizon 2020 Research
and Innovation programme, Hydrogen Europe, and Hydrogen

Europe Research. The contents of this document are provided "AS IS". It reflects only the authors' view, and the Joint Undertaking is not responsible for any use that may be made of the information it contains. The authors also acknowledge the financial support from the Slovenian Research Agency (research core funding No. P2-0401).

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