The impact on life cycle carbon footprint of converting from disposable to reusable sharps containers in a large US hospital geographically distant from manufacturing and processing facilities

Study overview

The scope of the study was to examine the life cycle carbon footprint of DSC and RSC over a 12-month period of facility-wide usage at a hospital geographically distant from manufacturing and processing plants, and include all unit processes in Manufacture, Transport, Washing, and Treatment & disposal stages.

Using established principles for assessment of the life cycle GHG emissions of goods and services (British Standards Institute, 2011) we utilised a cradle-to-grave life cycle inventory (LCI) and a product-system GHG assessment tool developed specifically for sharps containers and containing some 750 data cells (Grimmond & Reiner, 2012). In a before-after intervention study using a calculation model, we compared the annual GHG emissions for facility-wide usage of DSC and RSC at Loma Linda University Health (LLUH). The facility is an 1100 bed university healthcare system with 5 general acute care hospitals and an expansive outpatient clinic system in Loma Linda, California. The GHG included were CO₂, CH₄ and N₂O as these represent more than 99.5% of CO₂eq generated during the major life cycle stages of sharps containers (American Chemistry Council, 2010; EPA, 2016a). Greenhouse gases, other than CO2, were converted to their CO2eq on the basis of their per unit radiative forcing using 100-year global warming potentials defined by the Intergovernmental Panel on Climate Change (British Standards Institute, 2011). The annual GHG emissions for each container’s life cycle were expressed in metric tonnes of carbon dioxide equivalents (MTCO₂eq). All GHG data sources used in the study provided GHG outcomes as MTCO2eq. Review Board approval by LLUH was waived as no patients, patient data or patient specimens were involved.

The LCI itemised all energy-using processes required by each containment system’s life-cycle as implemented at LLUH. Scope 1, 2 and 3 processes were included in both study years. Unit process GHG were collated into the following life-cycle stages: manufacture (of polymer and containers); transport; washing (RSC); and treatment & disposal. We assessed GHG emissions from all energy used in these processes (vehicle fuel, gas, electricity, water supply and treatment) and in the manufacture and life cycle of ancillary products (pallets, transport cabinets, cardboard boxes, wash products). The boundary of the system studied, together with inputs, outputs and exclusions, are shown in Fig. 1.

Data sources

The following data sources were used in calculating GHG: DSC and RSC resin manufacture (American Chemistry Council, 2010); primary energy input data for DSC and RSC container manufacture (Clarion, 2014) and RSC washing (Daniels, 2017); industry-specific data for DSC autoclaving (Daniels, 2012); RSC and DSC transport (DEFRA, 2015); eGRID values for California, Michigan and Illinois power generation (EPA, 2016b); National data for energy inputs for US water supply and treatment (Chini & Stillwell, 2018); Industry data for manufacture of wash products (Nielsen, Li & Zhang, 2013; Shahmohammadi et al., 2017); Industry data for manufacture of cardboard (NCASI, 2017), representative data for manufacture of transporters (USDOE, 2010); Industry-specific data for pallet life cycle GHG (DEFRA, 2010): and US national values for incineration of DSC (EPA, 2018). The same database and values were applied to the relevant unit processes in DSC and RSC systems. Emissions for RSC manufacturing were calculated using a worst-case scenario based on the actual age of the manufacturer’s oldest, most frequently used RSC still in service nationally. Although it is theoretically possible for RSC to be recertified for a further period when they reach their certified reuse expiration, for this study their “end-of-life” was conservatively taken to be the number of years under the above worst-case scenario. The GHG associated with manufacture of ancillary reusables (transport-cabinets and pallets) were calculated on a per trip basis using their expected life span. Data on container size, model number, number used, and total Adjusted Patient Days (APD) (workload indicator) were obtained from LLUH. Total polymer required for manufacture of DSC and RSC was determined by weighing an example of each model of container and multiplying by the number of containers. The conversion-transition period (2 years) was excluded to avoid system overlap. Emission totals for each system’s annual use were workload-normalized by dividing its life cycle MTCO2eq by the APD for that year. The two ratios were then analyzed using WinPepi v11.65 (WinPepi, 2016). A Yates-corrected χ2 test was used for the analysis of proportions. Statistical significance was set at P ≤ .05 and rate ratios calculated using 95% confidence intervals.

System function, boundary, allocation and classification

The system function provided by the alternative products (DSC, RSC) was the supply of sharps containers for the disposal of sharps waste (biological, chemotherapeutic, pharmaceutical) within LLUH. The functional unit was the supply of each system for a one-year period. Sharps waste is a sub-category of medical waste and comprises items capable of penetrating human skin (e.g., needles, scalpels) which may have the potential to transmit infectious disease or pose a physical or chemical hazard. Because of these hazards, at disposal, all sharps must be safely contained in either DSC or RSC and transported to a treatment facility. With DSC the container is used once and the intact container and contents are subjected to treatment (commonly autoclaving, or incineration) prior to landfill. With RSC, the container is automatedly decanted of its contents (which are treated and disposed), and the reusable container is robotically cleaned and decontaminated, and reused a defined number of times. The boundary of the system studied (Fig. 1) included the energy required for the following unit processes: raw material extraction; polymer manufacture and transport; container manufacture and transport; transport of full containers to treatment facility; RSC processing-energy (including water supply, water treatment, and wash products); treatment of DSC; transport of treated DSC to landfill; and energy required for electricity generation and supply. Transport fuel processes were calculated from well to wheel. Excluded from the system boundary were treatment of container contents (identical in both DSC and RSC), infrastructure and assets, and any inputs and outputs that comprised less than 1% of mass or energy (British Standards Institute, 2011), or were not relevant to carbon footprint.

The production of polymer from oil or gas is a multi-function process and allocation of emissions and resource use was performed on a mass basis, as was transport, autoclaving and pallet manufacture. The injection-molding of DSC/RSC and the processing (cleaning and decontamination) of RSC are single-function processes and no allocation to co-products was necessary. Incineration of chemotherapeutic and pharmaceutical DSC was carried out in waste to energy incinerators that co-produce electricity and the avoided utility emissions were subtracted to give net GHG emissions per ton of specific polymer incinerated (EPA, 2018). In cardboard production (1.7% of total DSC life-cycle GHG) allocation was averaged using cut-off and number-of-uses methods where appropriate (NCASI, 2017). Regional emissions reported in eGrid represent electricity generation only—any emissions used for purposes other than making electricity were excluded from the adjusted emissions (EPA, 2016b).

Global warming was the impact assessment category to which all inventory data was classified as it is well-known and commonly used and understood by healthcare facilities. A table listing the raw data for all unit processes including flow, units, conversion factors, total GHG, data sources and data-representativeness, accompanies this publication.

Background and impact of distances

Commercial RSC, first used in US and Australia in 1986, now represent approximately 50% and 75% respectively of the sharps containers used in these countries, and since 1999 have been increasingly used in Canada, UK, Ireland, New Zealand, South Africa and South America. Generally, RSC are reused many times per year and, with rugged construction and effective inspection and repair, may last several decades. Prior to marketing in the U.S., RSC and DSC are required by the US Food and Drug Administration (FDA) to pass identical performance tests and design requirements as stipulated in sharps container standards (FDA, 1993). However, prior to this testing, FDA require RSC to undergo “lifespan simulation” and suggest

1. The containers be filled & processed for the number of lifespan uses stated by the manufacturer (e.g., 500 times); then,

2. the same containers be subjected to a transport vibration test, e.g., US Department of Transport Packaging Vibration Standard (USDOT, 2001), and then,

3. the same containers must pass the tests and performance criteria of a Sharps Container Standard.

Likewise, the Canadian sharps container standard does not distinguish between DSC and RSC in its performance test requirements and requires lifespan simulation of RSC prior to testing (CSA, 2014).

One reason healthcare facilities adopt RSC is for environmental sustainability (PGH, 2013) but quantitative studies confirming this fact are rare (Unger et al., 2016; Karlsson & Ohman, 2005).

A government study in the UK confirmed medical waste containers are among the top 20 items that account for more than 70% of the supply chain footprint and, to reduce the footprint, recommended: manufacturers report footprints of their products; reductions in quantity purchased; and sourcing of low carbon alternatives; (NHS, 2017). Our study found that converting from DSC to RSC significantly reduced the carbon footprint, and eliminated 50.2 tonnes of plastic and 8.1 tonnes of cardboard from the sharps waste stream.

Although the same RSC may be reused several hundred times, energy is required for their robotic washing between uses and, being heavier than DSC, their greater weight means more energy is required per unit for transport and manufacture. Ali, Weng & Chaudhry (2017) noted that GHG increase considerably when medical waste is transported longer distances. A previous life cycle study found that when container-manufacturing plants and RSC processing plant are close to the healthcare facility (HCF), the conversion to RSC resulted in an 83.5% reduction in GHG, and transport contributed 25.8% to the RSC life-cycle GHG (Grimmond & Reiner, 2012). In our study, the HCF was 3,500 km from the RSC manufacturing plant, and, more importantly (because of daily delivery), the RSC processing plant was 440 km from the HCF. This resulted in transport GHG accounting for 90.6% of the RSC life-cycle GHG (see Fig. 2). However, notwithstanding that these longer distances lessened the GHG differential between DSC and RSC, the conversion to RSC significantly reduced total sharps waste management GHG by 65.3%. The reduced number of container exchanges with RSC (with associated labor reduction) was also noteworthy (Table 1). The reduction in sharps management GHG with RSC use, while only a small component of the total supply chain emissions at LLUH, has been a positive step in the institution’s sustainability strategies. Unlike GHG reduction strategies dependent on changes in staff behaviour (waste segregation, turning off lights, car-pooling, etc.), our study confirms that purchasing strategies can enable immediate, sustainable and institution-wide GHG reductions to be achieved.

Impact on GHG over 10 years

The impact of repeated DSC manufacture and one-off RSC manufacture is best illustrated over multiple years. In the LLUH scenario over a 10-year period, 484,600 DSC would need be manufactured compared to 2783 RSC (and 4,120 chemo DSC), and would divert 502 tonnes of plastic from landfill or incineration.

Sensitivity analysis

Manufacturing (of polymer and containers) gave the largest differential between the two systems (see Fig. 2) and is predominantly a function of the energy required for the higher total polymer weight needed to be annually manufactured and molded for DSC. Although more DSC required transportation from the distant manufacturing plant, the daily transport of RSC from the distant processing plant resulted in a similar transportation GHG for both systems over the year (see Fig. 2). The sensitivity analysis revealed that variations in RSC lifespan contributed little to the GHG result—reducing RSC lifespan from a theoretical 41.7 years to 26.4 years (used in this study) or 15 years, reduced the DSC:RSC GHG difference by only 0.4%, and 1.3% respectively.

Electricity “cleanliness” across US grids (e.g., wind, coal, hydro) is a key variable in comparative GHG analyses (Unger et al., 2016) and the sensitivity analysis in our study showed that differing US electricity sources can alter processing and manufacturing GHG by 82% which, when extrapolated to the total life-cycle, can alter DSC GHG by 23% and RSC GHG by 10%. Optimization of reprocessing of medical products is recommended to lower GHG (Unger et al., 2016) however, in this scenario, RSC reprocessing accounted for only 5.6% of total RSC life-cycle GHG. Our analysis confirmed findings of other studies (Grimmond & Reiner, 2012; Unger et al., 2016), that material reclamation could reduce DSC life-cycle GHG if reclaimed plastic is used to offset virgin polymer use.

Other impacts of RSC

The focus of this study was carbon footprint however cost reduction (Grimmond & Reiner, 2012) and sharps injury reduction (Grimmond et al., 2010) have also been associated with RSC use and these factors, together with sustainability and mandatory frontline staff evaluation, were considered prior to adoption of the RSC system by LLUH. In terms of environmental impacts, we considered only one, global warming, however other impact categories such as ozone depletion, ecotoxicity, acidification, particulate matter, eutrophication, and human toxicity, may enable additional conclusions to be drawn (Eckelman & Sherman, 2016).

Study limitations and strengths

One limitation of the study was the assumption made in the location of manufacture of polymer for the DSC. To limit the impact of this assumption, the location was conservatively assumed to be a United States polymer-supplier close to the point of manufacture of the DSC. A second limitation was the use of the UK DEFRA database for transport energy inputs. This was necessary as no relevant United States database using tonne.km was available; however, all databases were applied equally to DSC and RSC systems. Study strengths were in the availability of 12 months of detailed usage data for both systems; the large transport distances compared to previous studies; the use of a conservative RSC lifespan; and the primary and region-specific availability of energy input data for unit processes in both systems.