We have a tendency to assume that, as long as our autoclave is producing sterile loads, it’s running fine. But that doesn’t really stand to reason: All devices begin to drift over time, and the more complex the device, the more factors can stack up to bring it wildly out of spec. Even when these increasing inefficiencies don’t have a dramatic impact on the unit’s core function, they can still have a profound impact on efficiency.
Since September of 2015, University of California, Riverside has conducted an ongoing study in their genomics and entomology labs, tracking the amount of water and energy consumed by two of the 37 high-quality medical-grade autoclaves installed across their campus. The results have been telling.
In a nutshell: Even a great autoclave will perform poorly when installed in the wrong place for the wrong task.
Verifying Poor Performance of Medical-Grade Autoclaves in Research Labs
Once you begin tracking your autoclave on a day-by-day, cycle-by-cycle basis, you’ll make startling discoveries. For example, this study found that these autoclaves were using five to six times as much water as seemed reasonable. As it turned out, the units’ bleeder valves (which cool autoclave waste water prior to it entering the sanitary sewage system) had drifted badly. Bleeder valve drift is a frequent issue with medical-grade sterilizers, especially when installed in research settings. The only effective fix is to monitor water usage via electronic log, and recalibrating the bleeder valves every time you see consumption creeping up.
But even with the sterilizers properly calibrated, the data still showed next to no correlation between the number of cycles run each day and water consumption. Ideally, water and energy usage should vary with the type of cycle — just as clothes washer water and energy usage vary between a small load of delicates or a large load of bath towels. Unfortunately, this is not the case with medical-grade autoclave installed in research facilities. Medical-grade units are optimized for round-the-clock use in hospitals, and thus need constant cooling. In a research setting — which is very low-usage by comparison — a bit more than half of their water consumption is to keep the unit cool while it sits idle.
One glaring example from the study: A 39-day period during which no cycles were run, yet the autoclaves still consumed almost 16,000 gallons of water.
Idle periods aside, on average each existing autoclave tracked in the study was using almost 700 gallons of water and 90 Kw/h of electricity per cycle. Across the campus’s 37 sterilizers, this added up annually to 1,134MWh of electricity and 8.8 million gallons of water (half of it when the machines weren’t even running) — and that was after they had a technician come and bring each unit back into spec. All told, each autoclave was using, on average, $3,300 in energy and water annually. That’s the maximum efficiency one might expect from these machines in this setting.
Comparing Research- and Medical-Grade Autoclaves
More telling was what Riverside found when they installed a research-grade sterilizer (a front-loading Priorclave 500L) in April of 2016, and tracked this autoclave’s performance against their existing medical-grade sterilizers. The results: in the first 26 weeks of their study, they found that the research-grade unit was using 81% less energy and 93% less water than a comparable medical-grade model (as of its 44th week, the numbers had improved further: 83% energy use reduction and 97% water savings). The utility savings alone in 15 years of owning one research autoclave could pay for its replacement.