Although we accept that the science of calculating greenhouse gas emissions is evolving, and that the accuracy of calculating kgCO2e is in its infancy, the calculated emission saving of 33,841 kgCO2e is hugely significant. For a 30-bed dialysis unit, the 30 plus tonnes of CO2e/year emission savings would be equivalent to driving the average car 85,500 miles (136,800 km) [10], more than three times around the equator. Even with this inexact science, our calculations can be used to generate a useful metric in that installing central acid delivery will save in the region of 1000 kgCO2e per dialysis station per year. This reduction in the amount of acid-concentrate required would lead to an annual financial saving of £18,400 (€ 21,500) calculated at current UK prices [112]. Many factors influence the cost of installing a central acid delivery system but within this project we expect the savings in acid concentrate to pay for the installation over a 3-to-4-year period.

We expected that the majority of greenhouse gas savings would come from not manufacturing and delivering the additional 40,000 L of acid concentrate required when using individual 5.0 L plastic containers. The fact that the removal of the high-density polyethylene plastic containers alone generated 22,444 kgCO2e of savings came as a surprise. The weight of each 5.0 L high-density polyethylene container is 250 ± 5 g (see Supplementary materials) making the total weight of plastic required to deliver 140,000 L of acid concentrate equal to 7000 kg. In comparison the one hundred 1000 L linear low-density polyethylene liners required to deliver 100,000 L of concentrate have a total weight of 227.5 kg. This difference in the amount of plastic required, and subsequent waste disposal, accounts for the vast majority of the greenhouse gas savings associated with moving to a central acid delivery system. Thus, switching to a central acid delivery system reduces not only the amount of single-use plastic required to be manufactured, transported, and then disposed of, but also reduces the volume of acid concentrate required by the dialysis unit.

Though outside of the scope of this study, there will be other further reductions in greenhouse gas emissions by using central acid delivery. The transport emissions required to deliver 28,000 empty 5.0 L containers to the manufacturing site will undoubtedly be significantly more than when delivering 100 plastic liners. As well as this, the additional 40,000 L required to be manufactured if using 5.0 L containers will need additional manufacture and delivery of chemical consituents to the factory.

Overall, as well as the reduction in carbon emissions, switching to a central acid delivery system produces less waste to be disposed of, along with reduced staff manual handling and time saved setting up and clearing away after the dialysis session. Using a central acid delivery system and the subsequent saving of one third of each 5.0 L cannister will also, over time, reduce the financial cost of dialysis. The reduction in greenhouse gas would have been even greater if we had been supplied with 6.0 L plastic containers for dilution at a 1:34 ratio, rather than 5.0 L containers for dilution at a 1:34 ratio, in terms of water requirements for production of acid concentrate, additional size and weight and of containers for transportation and waste disposal.

We accept that the advantage of choosing individual 5.0 L acid concentrates allows individualisation of the dialysis prescription, but no dialysis centre has the storage capacity to offer patients every conceivable variation in calcium, potassium, magnesium, and acetate concentrations. As with most UK dialysis centres, we currently offer several different acid concentrates, and moving to a central acid delivery system would lead to a reduction in the number of available concentrates. However, most of our patients used one of two concentrates and some 5 L containers will continue to be used for patients requiring an individual prescription.

Some countries, such as Japan, have favoured a single-batch dialysate delivery system, delivering a fixed electrolyte and bicarbonate dialysate [13]. Although this system would potentially further reduce greenhouse gas emissions, this does not allow for any individualisation of dialysate prescriptions [14]. Thus, compared to a single dialysate delivery system, a central acid delivery system does allow flexibility in the final dialysate composition via a choice of concentrate and adjustable dialysis machine settings.

Other systems such as Granumix™ (Fresenius Medical Company, Bad Homburg, Germany) are available, whereby a dry acid concentrate powder is delivered, then diluted, and mixed within the dialysis unit, designed for use with a central acid delivery system. As such, this would potentially additionally reduce the transport weight of the water and thus greenhouse gas emissions, but the system is not currently marketed within the UK. Another alternative has been to supply 3.5 or 5.0 L pre-mixed acid concentrate in soft polyvinyl chloride plastic bags (SoftPac™, Baxter Health Care Corporation, Illinois, USA), but this approach is limited to a number of specific dialysis machines. Although lighter than the equivalent high-density polyethylene containers, these are still single-use and thus any emissions savings are likely to be small in comparison to a central acid delivery system.

Haemodialysis is a well-established treatment for patients with kidney failure world-wide, however treatments require large volumes of treated water, mixed with acid concentrate and bicarbonate. Although many authors have concentrated on reducing or recycling the amount of water used for dialysis treatments [15,16,17], this study demonstrates that the main environmental impact is caused by the amount of single use plastic required. Rizan and colleagues demonstrated the dramatic increase in greenhouse gas emissions associated with the increase in single use, rather than a circular system of recycling and re-using medical plastic waste [18]. Our study supports their conclusions. The environmental consequences of delivering the acid concentrate in single-use disposable plastic containers, along with the wastage of the actual product, is viewed as completely unsustainable.