To evaluate the environmental impact of two medical sterilization packaging options, a consequential Life Cycle Assessment (cLCA) was conducted, to assess the environmental consequences of both products, using OpenLCA and the ecoinvent database largely based on ISO 14040/44 standards (23). This analytical approach cLCA allowed for the assessment of the potential outcomes resulting from decisions made within and outside of the system being evaluated (16, 24), with this approach, different scenarios for the two products were compared.
3.1 The Products
This study considered the single use HALYARD H200 Sequential Sterilization Wrap (25) made of SMS non-woven and recyclable polypropylene (PP) (101 cm X 101cm) as a reference for ‘Blue sheets’ and a Medline Steriset TVA60 RSC (26) made of stainless steel and aluminum (596 mm (23 15/32”) x 275 mm (10 53/64”) x 120 mm (4 23/32”) (Fig. 7). Both products are used to encase a standard format instrument tray (European Standard DIN: 480 × 250 × 60 mm) of surgical tools during steam sterilization.
3.2 Goal and Scope
The primary aim of this study was to compare the potential environmental impacts of two distinct sterilization packaging systems: single-use and multi-use. These systems were evaluated throughout their entire lifecycle, with a focus on their Functional Unit; the specific function they serve. By understanding their environmental impacts, we sought to provide decision support for improved sustainable decision-making. The ReCiPe2016 Midpoint (H) method was applied. ReCiPe2016 offers a robust framework for assessing multiple environmental impacts (27).
The scope of this study is a cradle to grave assessment which considers four product phases 1) production of the products (including raw material extraction), 2) transportation from the extraction of raw materials, through manufacturers and suppliers, to the reference hospital, 3) the use phase (i.e., sterilization, disinfection, and hand washing), and 4) end of life (i.e., incineration and potential recycling). The production of capital goods (autoclave and disinfection cabinet) was excluded from the scope as they were assumed to have a negligible impact (28)
3.3 Functional Unit
As further explained below, the functional unit used in the comparison was:
548 uses over a period of 10 years.
Based on information from our reference hospital and the product manufacturer, RSCs were used approximately once per week, suggesting 548 uses within the ten-year life span (assuming that the boxes can be used throughout their ten years of warranty and are discarded once their warranty expires, regardless of their condition).
Both packaging types function under the same steam sterilization process regulated under the European Standard for sterilization- steam sterilizers (DS/EN 285:2015 + A1:2021). After the sterilization process, both products are ready for use, after passing quality inspection, and are brought to the OT for another visual inspection before unpacking. The following two subsections elaborate on some of the differences between the two compared products.
3.4 Modelling
The assessment was done using openLCA (v2.0.0), using the ecoinvent (v3.9.1) consequential database for background life cycle inventories and primary data combined with literature for describing the foreground processes.
The modelling is consequential, and as the results later pointed to energy consumption being an impact hot spot, the energy marginals were replaced with current supply mixes for heat and electricity to further test the influence of background energy on results. This means that there are two sets of results for the compared systems.
Of interest was also finding breakeven points where multi-use and single-use have the same impact potential. This can also serve as decision support for investments that are initially less sustainable but become better in a longer-term perspective. To calculate the two different products over different modifications to the life cycle, different sets of results were reached in the study, in which the environmental impacts from both products over 548 cycles were assessed and quantified in CO₂e (cradle to grave). While ‘Figure 3’ serves as a baseline to better understand the current system, ‘Figure 4’ can function as decision support for the relevant actors (hospitals, waste handlers, and policy makers).
Figure 3 results (Baseline) are based on a system where heat and electricity are produced from the current Danish energy mix without any recycling of the Blue sheets. Due to the OT context, the Blue sheets are classified as ‘hazardous waste’ through the Statutory Order on Waste ((29)). This is a 1998 ministerial guideline that specifies how hazardous medical waste should be treated and this is still valid at the time of writing. According to this guideline, all Danish hazardous medical waste must be incinerated, which makes recycling of the Blue sheets illegal. Therefore, energy recovery of the Blue sheets is the current practice and is calculated as a negative input assuming substitution of the average fuel in the Danish energy mix (2023). This scenario serves as a baseline scenario.
Figure 4 (100% incineration of Blue sheets) results are modelled based on a system where heat and electricity are ‘greener’ based on (30, 31)(). A shift to renewable energy is assumed, in accordance with the Danish Climate Act, in which a 70% reduction of GHG emissions are pursued and should be reached by 2030 (12)).
Figure 4 results (60% recycling, 40% incineration of Blue sheets) represent the same shift towards renewable energy as in the former, and further implements a 60% recycling rate of the Halyard sheets, as part of a take-back scheme proposed by the producers, where the percentage is based on the producer’s estimate. For the remaining 40%, incineration in the future Danish energy grid is assumed (substituting the marginal supply). This scenario serves as a ‘what if’ scenario, where we explore the idea of instead of only removing plastics from our society, we pursue a ‘greener’ plastic usage where recycling is encouraged. Hence, scenario 3 should also be interpreted as decision support.
3.5 Impact Assessment
This study primarily focused on GWP, where the results from the contribution screening identified hotspots in the use phase. This led to sub-sequent iterations to further scrutinize the discovered hotspots and to better understand how emissions occur in the contemporary Danish context versus the projected most likely future. A multi-impact category analysis was performed to further detail the results and to provide more data for further research.
3.6 Life Cycle Inventory
3.6.1 Background systems
The modelled systems were constructed within an Excel spreadsheet, utilizing inventory data sourced from ecoinvent. When necessary, custom processes were modelled in OpenLCA and subsequently integrated into said spreadsheet. In this manner, OpenLCA acted as a bridge between the ecoinvent database and the resulting emission data, which served as building blocks in the primary Excel sheet.
Deviations from ecoinvent in energy recovery:
Consistency within the consequential methodology was ensured by making sure the marginal supply of energy was modelled appropriately. Therefore, custom modelling was applied to the heat and electrical grids of all three scenarios. The customized energy grids reflect data gathered from literature, combined with building blocks from ecoinvent data.
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System 1 is based on the current mix of heat and electricity set in a Danish context and will be referred to as ‘Energy Mix’ (30).
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Systems 2 and 3 both share the same energy grid and is referred to as ‘Marginal Future’ (Bisinella et al., 2022; Dansk Fjernvarme, 2022), combined with ecoinvent data).
For the Marginal Future scenario, the heat supply was modelled using the ‘2-degree’ scenario where the supply represented 73% from electricity and 27% from biomass. (The electricity was modelled based on the projected marginal supply mix for electricity generation).
3.6.2 Foreground systems
The model includes an average of 19.1 kWh of energy consumed per cycle of steam sterilization, averaged from three studies that assumed 15, 20, and 22.3 kWh respectively (18, 32, 33). The model assumes full capacity of 9 baskets per cycle (medical instrument baskets packaged with either RSCs or Halyard Blue sheets), as referenced in the product catalogue (34). Data pertaining to the disinfection cabinet, KEN IQ6 were obtained from the product catalogue and description and included 18.5 kWh of energy consumed per cycle, 23.5 liters of water, and 0.006g and 0.0006g of detergent and pH regulator, respectively (35). An additional hand washing process is included for the RSCs and assumed the consumption of 5L of water and 5 grams of soap per wash/RSC. The use phase for the autoclave was modelled for marginal and energy mix scenarios, where the marginal scenario considered electricity consumption at medium voltage (DK), formaldehyde, tap water, and wastewater. The use phase of the disinfection cabinet for the marginal and energy mix scenarios considered electricity at medium voltage, non-ionic surfactant, potassium carbonate, tap water, and wastewater. Handwashing of the RSCs for both scenarios considered soap, tap water, and wastewater (average).