Most of what has been published on sustainable kidney care measures one thing: environmental impact, usually carbon. KitNewCare was designed on the premise that this is not enough, and a group of the project's publications is now mapping what the field still does not know.

Anyone who has attempted a life cycle assessment in healthcare knows where the work actually goes. Not in the modelling, but in the weeks beforehand: dismantling every consumable in a treatment pathway, weighing each component, identifying each polymer, and reconstructing the clinical process in enough detail that the inventory means something. It is unglamorous, it is slow, and it is repeated from scratch by nearly every team that tries.

If a dialysis service wanted to reduce its environmental impact by choosing between haemodialysis and online haemodiafiltration, a KitNewCare study in Modena has an unhelpful answer: it barely matters. The more useful finding sits elsewhere in the same numbers.

Sustainability in dialysis has no shortage of good ideas. What it has lacked is a reliable way of telling the significant ones from the merely virtuous. Four KitNewCare-linked publications now put numbers on that question, and some of the answers are counter-intuitive.

Few things in a dialysis unit look less like a strategic decision than the container the acid concentrate arrives in. Three KitNewCare studies, carried out independently in Spain, the Netherlands and Italy, have arrived at the same conclusion from different starting points: it is one of the most consequential procurement choices a haemodialysis service makes.

Peritoneal dialysis is often assumed to be the greener form of dialysis. It is done at home, it needs no water treatment plant and it spares patients three journeys a week to a clinic. A group of KitNewCare studies now shows that this reassurance is only half the story, and that where a patient is treated can matter almost as much as which therapy they receive.