, Introduction
Several recent studies have underscored the correlation between the deterioration of environmental conditions, exacerbation of kidney disease, and renal function decline [1,2]. Paradoxically, the treatment regimen for patients with kidney disease—particularly resource-intensive procedures such as dialysis—entails resources and by-products that impose a significant burden on the environment. In response, the Korean Society of Nephrology articulated its steadfast commitment to mitigating the ecological repercussions of kidney disease treatment and fostering resilient and sustainable kidney care. The Society provides actionable recommendations for reducing the environmental impact of various forms of dialysis treatment and aspires to spearhead the journey toward sustainable kidney care through concerted efforts aimed at advocacy and the furtherance of members’ proactive engagement. The Recommendations for Sustainable Kidney Care today represent the Society’s inaugural stride toward advancing the sustainable transformation of kidney care.
The recommendations for water conservation in hemodialysis
Key message
HD-Water 1. It is crucial to make proactive efforts to decrease reject water when producing dialysate in hemodialysis (HD).
1.1. We recommend regular monitoring and measuring reject water production and the recirculation rate of the reverse osmosis machine water filters on a regular basis for effective use and conservation of water resources.
1.2. We advise considering various approaches from different perspectives to reduce reject water.
HD-Water 2. It is crucial to make proactive efforts to reuse reject water when producing dialysate in HD.
2.1. We suggest reject water as a resource that may potentially be reused and recycled according to local demands.
2.2. We advise examining the components of reject water to determine its suitability for reusing reject water.
Maintenance hemodialysis (HD) is a treatment that consumes large quantities of water. Thrice-weekly, 4-hour sessions with a dialysate flow rate (Qd) of 500 mL/min consume approximately 20,000 L of water per year, and hemodiafiltration (HDF) consumes 10% to 30% more water than standard HD [1]. Priming, rinsing, and sterilizing dialysis machines require water. Dialysis-quality water is generated through a reverse osmosis (RO) treatment system that produces reject water to remove heavy metals and endotoxins. However, the term “reject water” may be a misnomer since it has already passed through multiple filters before being discarded (Fig. 1).
Low-efficiency RO systems reject up to 60%–70% of the feed water, whereas upgraded water treatment systems can lower this ratio to 20%. High-efficiency RO systems are advantageous because they conserve up to 50% of the feed water (feed water quality is an important consideration). However, they can be more expensive, and the lifespan of the filters is shorter than that of low-efficiency systems [3]. The temperature of the feed water also affects the amount of reject water; high temperatures increase the amount of product water, while low temperatures decrease it [4]. In Korea, which has four distinct seasons, more product water is produced during the summer months from May to September. A single-center study in Korea showed an average reject water of 30% to 40%, depending on the temperature (Fig. 2).
Globally, a few dialysis centers recycle reject water using a redirection system [4]. These centers utilize reject water according to local needs and resource availability. In Malaysia, treated reject water is used for fish breeding and vegetable farming (Fig. 3) [5]; in Australia, reject water is used to generate steam for medical equipment sterilization [6]; and in Morocco, demineralized reject water is used for the irrigation of gardens and landscape plantings [7].
Key message
HD-Water 3. Decreasing the dialysate flow rate (Qd) can be considered a way to save water resources as long as the efficiency of hemodialysis (HD) is undamaged.
3.1. When Qd is lowered by 20%, from the current standard of 500 mL/min to 400 mL/min, a maximum of 100 L of water can be saved from a single HD session.
3.2. We suggest HD with a Qd of 400 mL/min to save water because there is no significant difference in dialysis adequacy and/or short-term clinical outcomes compared to a Qd of 500 mL/min.
3.3. Application of an automatically adjustable Qd function may be considered for reducing water in HD, if available.
A Qd of 500 mL/min is widely accepted as the standard for HD and online HDF. Modern developments in hemodialyzer design and hollow fiber manufacturing have improved dialysate flow in dialyzers, enabling higher clearance at the same flow rate [6]. If Qd is decreased by 20% and lowered to 400 mL/min, 24 L to 100 L of water can be conserved per session, considering water rejection from low-efficiency RO systems [2]. However, the trade-off between water conservation and lower solute removal raises concerns regarding patient outcomes.
Recently, some dialysis machines have been equipped with a function that allows automated Qd adjustment, reducing the amount of water used in dialysis [7,8]. For example, the AutoFlow option installed on FMC 5008 machines (Fresenius Medical Care) automatically adjusts Qd to 1.5 times the blood flow rate (Qb). After adopting this system, a 9% reduction in water use was achieved, which was estimated to conserve approximately 1,140 m3 or 400 t of water per year and reduce annual carbon dioxide emissions by 3,715 kg CO2 [9]. Mesic et al. [10] reported a randomized crossover trial comparing online HDF using the AutoSub and AuoFlow functions of the FMC 5008 equipment and high-flow HD in 54 patients for 6 weeks. Their results showed that dialysate use decreased by 8% in the online-HDF group compared to the HD group, while Kt/V was 3.5% higher, suggesting that the application of automated Qd control in HDF helps reduce dialysate use without loss of efficiency. Canaud and Davenport [11] recommended that the ratio of Qd to Qb be maintained at 1.4 times when applying HDF, which is consistent with the current setting of the AutoFlow module. There was no difference in convection volume among the various Qd rates, and reducing Qd from 500 mL/min to 400 mL/min and 300 mL/min resulted in a decrease in Kt from 73 L to 71 L and 68 L, and the urea reduction ratio from 84.1% to 83.6% and 82.5%, respectively, without a change in middle molecule removal [12]. Alternatively, expanded HD using medium cutoff (MCO) dialyzers such as Theranova (Vantive) or Elisio Hx (Nipro Corp.) would provide additional options for effectively removing the middle molecule compared to conventional HD without consuming more water than online HDF. In addition, new methods that can reduce dialysate and water use are emerging with the development of HD technology. For example, sorbent dialysis, which reclaims used dialysate by recirculating it through a specialized membrane, only requires approximately 6 L of water; therefore, if commercialized, it is expected to reduce water use greatly [5]. Home HD using equipment such as NxStage (Fresenius Medical Care), which uses only approximately 10% of the water compared with conventional HD, is also a way to save water [13]. Recently, efforts to develop a system for home HD have been active in Korea. However, these efforts must be matched with methods for proper reimbursement systems to support home HD.
The recommendations for waste reduction in hemodialysis
Key message
HD-Waste 1. We recommend that the total waste in the dialysis unit be primarily classified into medical waste and nonmedical waste according to the guidelines of the respective region.
1.1. In Korea, medical waste is classified into infectious medical waste, hazardous medical waste, and general medical waste.
1.2. If general waste is not separated from medical waste and is discharged in a mixed state, it is considered medical waste, leading to increased disposal volume and costs.
Current issue
According to the World Health Organization guidelines, medical waste is defined as “the total waste stream from a healthcare facility” [14], but regulations for classifying and managing medical waste vary by region (Table 1). In Korea, medical waste is designated as waste subject to the Waste Control Act and is divided into infectious, hazardous, and general medical waste, which are further categorized into five types, as shown in Table 1. In the dialysis unit, several kilograms of waste are generated per dialysis session, including needles, lines, and dialyzers that come into contact with the patient’s blood and diverse items such as dialysate containers, packing paper, and cardboard. If these are not properly separated from general waste according to the guidelines and discharged in a mixed state, general waste is considered medical waste, resulting in an increased discharge volume and significant processing costs. In an online survey conducted at 126 general hospitals in Korea, 29 hospitals (23%) disposed of medical waste in general waste containers, and 66 hospitals (55%) disposed of general waste in medical waste containers [15]. According to the study by Piccoli et al. [16], depending on the degree of separation of medical waste in the dialysis unit, the amount of hazardous medical waste per dialysis session showed a large difference ranging from 1.11 to 8.09 kg, leading to significant differences in processing costs from 2.97 to 21.67 dollars. These results show the importance of properly classifying medical waste and general waste, primarily in reducing medical waste generation.
Key message
HD-Waste 2. An eco-friendly design for the environment is important from the manufacturing stage to reduce medical waste in the dialysis unit, and we suggest that the application of this design be extended not only to dialysis equipment and consumables but also to the entire dialysis system.
2.1. We suggest manufacturers apply a design for the environment to dialysis equipment and consumables to reduce medical waste in the dialysis unit effectively.
2.2. Although the central dialysis fluid delivery system is expected to have an advantage over the single-patient dialysis fluid delivery system regarding medical waste generation, clinical safety aspects must also be considered.
A design to minimize the amount of waste is very important because most of the items discharged from the dialysis unit come into contact with blood and are classified as medical waste. It includes eco-friendly materials, miniaturization, weight reduction, and 3R (reduce, reuse, and recycle) applications. With the recent visualization of global corporations’ environmental, social, and governance (ESG) declarations and national-level movements to legislate ESG, manufacturers in the dialysis-related industry are also focusing on the production of dialysis equipment and consumables, following environmentally friendly policies.
The dialysis fluid delivery system is broadly divided into the central dialysis fluid delivery system (CDDS) and the single-patient dialysis fluid delivery system (SPDDS) (Fig. 4) [17]. In Korea, the CDDS accounts for approximately 12%, and most use a central concentrate delivery system (CCDS), which supplies only concentrate A. An Italian study in which 11,000 dialysis treatments were performed with CCDS in 85% of patients over 1 year reported a saving of 25,220 euros by reducing 11,470 kg of plastic material and 7,150 kg of acid concentrate residuals. They also showed that the movement and/or management of 59,180 kg of material was avoided with a considerable reduction in the operators’ and caregivers’ efforts [18]. As seen above, the CCDS effectively reduces medical waste by decreasing concentrated waste and consumables, such as connection lines and packaging, compared to the SPDDS. Moreover, additional benefits are expected in terms of energy consumption related to dialysate transport and storage. However, CCDS requires attention to issues such as infection, system instability, and aspiration when mixed with acetic acid, and clinical safety aspects must also be considered (Tables 1, 2).
Key message
HD-Waste 3. The reuse of dialysis-related items is extremely limited due to infection; however, dialyzer reuse may be considered for expanding healthcare provision depending on economic considerations. However, strict disinfection standards must be observed, and studies on safety and systemic cost-benefit analysis should accompany the reuse process. Additionally, it is essential to investigate the environmental impact of the disinfectant chemicals used. While the reuse of dialyzers may reduce solid waste, it could potentially increase liquid waste and environmental pollution.
In the past, dialyzers were reused to expand healthcare provision by reducing costs; however, many countries now prohibit dialyzer reuse due to risks such as infection and exposure to disinfectants. However, it is necessary to reuse dialyzers in developing countries. Based on 50 years of clinical experience, it is generally agreed that the reuse process is safe when there is strict compliance with the standards set by the Association for the Advancement of Medical Instrumentation [16]. Studies have shown that reusing dialysis filters with strict disinfection standards does not increase patient morbidity and mortality [19]. Therefore, depending on the country’s economic situation, the reuse of the dialyzer may be considered.
The recommendations for energy saving in hemodialysis
Key message
HD-Energy 1. We suggest considering the energy optimization of hemodialysis (HD) facilities.
1.1. We suggest the installation and utilization of facilities that maximize energy efficiency in HD units, such as lighting, heating, ventilation, and insulation.
1.2. We suggest considering the maximum use of renewable energy sources to supply power to the HD unit.
1.3. Consider actively applying and managing methods to reduce unused energy in the facility installing sensors in locker rooms, cutting off power to machines that are not in use, and applying a master switch to turn off power during all nonoperating hours.
According to a report from the Korean Society of Nephrology, 107,015 patients undergo HD three times a week, with 87.7% receiving conventional HD, excluding HDF and other modalities. It is assumed that at least 19.86 million dialysis filters were used in HD centers in South Korea in 2023, with a similar number of sessions or more expected. Considering the power consumption per hour of HD machines available in Korea, ranging from 0.68 to 2.5 kWh (3.1 to 10 kWh per session) and assuming a session duration of 4.5 hours, without considering new dialysis initiation or special situations like sustained low-efficiency dialysis, the total energy consumption is estimated to be at least 48.9 to 179.7 million kWh [20]. Compared with the annual energy consumption in Korea in 2022, which is 10,652 kWh, the additional energy consumption per patient undergoing HD is estimated to be approximately 1,030.32 kWh per year, resulting in an approximately 10% increase in energy consumption for each additional patient. Active monitoring of the actual energy input to the treatment, minimizing wasted energy, optimizing dialysis machine operation time, and centralizing the control of all other electrical devices/facilities have been suggested [21].
Key message
HD-Energy 2. We encourage all members of the hemodialysis unit to participate actively in energy-saving efforts.
2.1. Corporations: Strive to develop additional optimization models for existing dialysis equipment to maximize energy efficiency.
2.2. Academic societies and governments: Propose standardized guidelines to promote the design and use of energy-efficient dialysis rooms and the use of eco-reporting systems.
2.3. Consider including education on energy conservation and carbon neutrality in patient and staff education programs to promote a culture of environmental conservation and change individuals’ environmental awareness.
For achieving ‘Green Nephrology’, not only are the efforts of healthcare professionals important, but the attention and commitment of companies manufacturing dialysis machines are also crucial, as the majority of energy consumed during dialysis occurs through these machines. Healthcare professionals should prioritize the selection of dialysis machines that maximize energy efficiency and encourage dialysis manufacturers to maintain continuous interest and participation in eco-dialysis. Since 2005, France has implemented an eco-reporting system, tracking and observing key performance indicators (KPIs) such as electricity and water usage, as well as the amount of waste generated from dialysis treatments over a period of approximately 15 years. During this time, electricity consumption decreased by 29.6% (from 23.1 to 16.26 kWh/session), while water usage decreased by 52% (from 801 to 382 L/session). Most of these reductions were achieved through the continuous remodeling of dialysis machines and water-related systems due to advancements in dialysis technology. Waste generated after dialysis decreased from 1.8 to 1.1 kg, attributed to education among healthcare professionals. Ultimately, carbon dioxide emissions decreased significantly, totaling 102,440 t, demonstrating the effectiveness of implementing eco-reporting as KPIs in dialysis rooms [22].
The recommendations for carbon footprint reduction in hemodialysis
Key message
HD-Carbon footprint 1. In order to reduce the carbon footprint during hemodialysis treatment, active consideration should be given to utilizing renewable energy sources.
HD-Carbon footprint 2. We propose educating patients and medical staff to utilize public transportation actively.
Given that HD treatment typically requires three sessions per week, the transportation of patients to and from the hospital during these sessions may contribute to ongoing emission-related issues. Although data on transportation emissions in domestic settings have not yet been provided, it is anticipated that as such data accumulate in the future, the associated burdens may become apparent, leading to efforts aimed at effective reduction.
The recommendations for water conservation in peritoneal dialysis
Key message
PD-Water 1. It is recommended that methods for the more efficient use of water resources in the production process of peritoneal dialysis (PD) fluid be actively considered.
PD-Water 2. It is suggested that solutions to prevent the wastage of dialysate during the PD treatment process be actively sought to use water resources more efficiently.
Peritoneal dialysis (PD) offers a more efficient use of water resources than HD due to its lower volume of dialysate utilized in treatment [6,23,24]. While HD may consume approximately 360 L of water per week with sessions lasting 4 hours, three times a week at a flow rate of 500 mL/min, and PD typically utilizes only 70 L/wk with a daily usage of 10 L/min. Dialysate for PD treatment is produced by a complex process involving chlorination to kill bacteria and other microbes, multimedia filtration to remove sediment and particulates, application of a softener to remove hardness (calcium and magnesium ions), and carbon filtration to remove odor, taste, and chlorine.
The amount of dialysate required in PD varies depending on the patient’s residual renal function and body weight. Special insurance covers PD fluid in Korea, which covers only 10% of patient payments. However, drainage bags are classified as medical materials and are not covered by dialysis reimbursement, leading to a higher patient copayment for drainage bags than PD fluid bags. Therefore, while it would be ideal to use only drainage bags in cases requiring drainage without using a connected dialysate, such as night intermittent PD and other treatments, the current medical environment results in the wastage of water resources due to the disposal of connected dialysate along with the drainage bags.
The recommendations for waste reduction in peritoneal dialysis
Key message
PD-Waste 1. Efforts are needed to reduce the environmental impact of peritoneal dialysis (PD).
1.1. It is proposed that dialysis bags be made from polyvinyl chloride (PVC)-free biodegradable materials wherever possible to minimize the use of PVC in manufacturing PD bags.
1.2. We propose the vitalization of recollecting the bags through a dialysate delivery system to increase the recycling rate in PD bags.
PD-Waste 2. Shipping boxes used for PD bag delivery should be made of paper and disposed of in a paper recycling bin.
Compared to HD, PD is thought to produce less waste per dialysis session than HD; however, because it is performed daily. The total amount of waste is reported to be slightly higher for PD than for HD when calculated per patient per year [6]. In addition, for PD, a significant portion of carbon emissions arises from the packaging of dialysis fluid, the manufacture of plastic dialysis bags, and the transportation process involved in delivering the PD solution to individual homes. Therefore, efforts to minimize these processes are urgently required. Biofine (Fresenius Medical Care) material currently used in PD does not contain chlorine; it has the advantage that it does not produce any environmentally harmful substances when incinerated. A comparison of current Biofine-based products with polyvinyl chloride (PVC)-based products showed that up to 88 kg of disposable waste could be saved per year for patients with continuous ambulatory PD (CAPD) and up to 29 kg for patients with ambulatory PD (APD). Even if the materials are recyclable, collecting only dialysis bags—a single recyclable material—is expected to greatly increase recycling efficiency rather than mixing them with other household waste. Currently, a Korean PD company collects all PVC material dialysis bags, recycles those that can be recycled through a process, minimizes those that cannot be recycled, and disposes of them. This process recycles more than 87% of the post-sorted PVC bags in Korea. The annual recycling amount was confirmed to exceed 250,000 kg. However, this process is currently available only in metropolitan areas. Therefore, it is necessary to expand the process nationwide.
The recommendations for carbon footprint reduction in peritoneal dialysis
Key message
PD-Carbon footprint 1. It is imperative to actively consider methods to minimize transportation to reduce the carbon footprint associated with emissions during the transportation process of peritoneal dialysis (PD) fluid.
PD-Carbon footprint 2. Continuous efforts should be made to enhance the efficiency of the transportation process of PD fluid, and actively considering the use of environmentally friendly vehicles during transportation is essential.
In the case of PD, the carbon footprint generated during the dialysis treatment process is estimated to be relatively low compared to that generated during HD [25]. Compared with HD, research on the carbon footprint of PD has not been actively conducted. A study reported from China estimates an annual carbon footprint emission of 1.4 t of CO2-Eq per person [26]. However, this study had limitations in terms of accurately calculating the transportation of dialysis bags. Therefore, it is believed that the main factors contributing to the carbon footprint in PD treatment are the emissions generated during the transportation of the dialysis fluid and accessories required for the treatment. Therefore, it is necessary to improve the carbon footprint in relation to these factors. A recent study from Australia by McAlister et al. [24] reported that the annual CO2-Eq per person for PD treatment was much lower than that for HD. Considering the variation in transport impact depending on distance, it was estimated to be 1,455 to 2,716 kg in CAPD, while APD was higher at 2,350 to 4,503 kg. Transporting PD fluid through maritime routes is estimated to generate 1 t of CO2-Eq annually for every 1,000 km transported per patient.
The recommendation for water conservation in continuous kidney replacement therapy
Key message
CKRT-Water 1. We recommend each institution to monitor the dose of dialysis delivered so that the delivered dose can be maintained between 20 and 25 mL/kg/hr.
CKRT-Water 2. We suggest avoiding routine replacement of the filter membrane every 24 hours in the absence of membrane failure.
2.1. We suggest that every institute implement a separate disposal of recyclable waste (packaging materials, support plate, dialysate bag) and that every manufacturer considers active recycling of the waste.
2.2. We suggest the use of regional citrate anticoagulation to increase filter life and reduce filter waste.
CKRT-Water 3. We recommend making active efforts to reduce repetitive priming by avoiding unnecessary interruptions in continuous kidney replacement therapy.
According to reports by Rhee et al. [27] and Lee et al. [28], the usual prescribed and delivered doses for continuous kidney replacement therapy (CKRT) in South Korea are between 35 and 40 mL/kg/hr, and the actual delivered dose ranges from 30 to 40 mL/kg/hr, which implies that more than 90% of the prescribed doses are delivered. In the implementation of CKRT, the prescription of an unnecessarily higher dose than required leads to an unnecessary increase in water usage. Based on this, the 2012 KDIGO (Kidney Disease: Improving Global Outcomes) acute kidney injury (AKI) guidelines recommend delivering an effluent volume of 20–25 mL/kg/hr for CKRT in AKI (evidence level 1A) [29]. However, when applying CKRT in clinical settings, a higher dialysis dose can be prescribed because of the downtime, which is the time to stop CKRT for various reasons (transfer, examination, filter replacement, etc.). Rhee et al. [30] reported that optimize CKRT dosing between 20 and 25 mL/kg/hr allowed for a 12.7% reduction in fluid consumption (i.e., 6.7 L/person/day). Given the absence of demonstrable clinical advantage with higher doses, adopting lower doses appears justified, aligning both with clinical prudence and sustainability considerations.
The Korean National Insurance system covers one filter per day, and the estimated mean CKRT filter life is 23 to 24 hours (estimated by the Korean Health Insurance Review and Assessment [HIRA] database; the total number of filters used/total frequency of CKRT procedure-claimed) in South Korea. Based on the frequency of CKRT procedure codes in the HIRA system (122,595 in 2022), the mean estimated duration of CKRT is 8 to 9 days, and the filter life is 23 to 24 hours, which is significantly shorter than those reported in the study by Zarbock et al. [31] (filter life 35–42 hours) with regional citrate anticoagulation (RCA). In South Korea, RCA is currently not applicable, and nafamostat or heparin is used as the anticoagulant for CKRT.
The CKRT filter kit is composed of a filter membrane, tubes connecting the filter, a supporting plate, and packaging. An empty bag of dialysate or replacement solution composed of pure polyolefin, weighing approximately 62 g (5 L bag) to 76 g (10 L bag), has been reported in previous research as suitable for high-quality recycling since it is a clean waste that can be easily separated from other wastes [32].
The recommendations for energy saving for continuous kidney replacement therapy
Key message
CKRT-Energy. We recommend making active efforts to reduce repetitive priming by avoiding unnecessary interruptions in continuous kidney replacement therapy.
The power consumption for CKRT priming was 33% higher than the energy consumption during the CKRT operation (average of 120 W per hour during priming versus 90 W per hour during operation) (Supplementary Fig. 1, available online). If the frequency of filter changes increases, not only does the consumption of CKRT filter kits rise, but the frequency of priming procedures also increases, leading to a corresponding increase in energy consumption. The reasons for interruptions and subsequent priming during CKRT are diverse. According to reports by Rhee et al. [33], the most common cause of membrane changes was not related to filter problems; transfers for examinations, procedures, and surgeries accounted for 50.8%, while exchanges due to filter clotting constituted 19.9%.
Discussion: Limitations and future research
Looking ahead, further research and development are needed with a multidisciplinary group approach. Reducing Qd to 400 mL/min offers a simple strategy to conserve water without compromising dialysis adequacy. The recent CONVINCE study has proven clinical relevance, high-volume HDF prolonged life expectancy compared with HD, but its excessive water demand raises sustainability concerns [34]. At the same time, expanded HD with MCO membranes provides comparable middle-molecule clearance and preservation of residual kidney function while avoiding the high-water burden of HDF [35]. Dialysis using MCO membranes is described as eco-friendly [36]. MCO membranes with the reducing dialysate flow need further investigation representing a feasible, resource-conscious alternative that balances patient outcomes with environmental responsibility. The application of extended producer responsibility to dialysis-related wastes that are easy to recycle should be considered (Table 3). It is also important to establish indicators that can quantify and monitor waste generation and recycling rates. Cost-effectiveness studies and safety analyses would be essential if dialyzer reuse were to be reconsidered. In the field of CKRT, improving the energy storage capacity of machines to enable longer operation without a power source represents a promising direction. Finally, refinement of national regulations on medical waste management will be necessary to ensure that potentially recyclable materials are effectively recovered and reused.
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