Steam sterilisation's energy and water footprint

Objective. The aim of the present study was to quantify hospital steam steriliser resource consumption to provide baseline environmental data and identify possible efficiency gains. We sought to find the amount of steriliser electricity and water used for active cycles and for idling (standby), and the relationship between the electricity and water consumption and the mass and type of items sterilised. Methods. Welogged a hospital steam steriliser's electricity and water meters every 5 min for up to 1 year. Weobtained details of all active cycles (standard 1348C and accessory or 'test' cycles), recording item masses and types. Relationships were investigated for both the weight and type of items sterilised with electricity and water consumption. Results. Over 304 days there were 2173 active cycles, including 1343 standard 1348C cycles that had an average load mass of 21.2 kg, with 32% of cycles <15 kg. Electricity used for active cycles was 32 652 kWh (60% of total), whereas the water used was 1 243 495 L (79%). Standby used 21 457 kWh (40%) electricity and 329 200 L (21%) water. Total electricity and water consumption per mass sterilised was 1.9 kWh kg(-1) and 58 L kg(-1), respectively. The linear regression model predicting electricity use was: kWh = 15.7+ 0.14 x mass (in kg; R-2 = 0.58, P < 0.01). Models for water and item type were poor. Electricity and water use fell from 3 kWh kg(-1) and 200 L kg(-1), respectively, for 5-kg loads to 0.5 kWh kg(-1) and 20 L kg(-1), respectively, for 40-kg loads. Conclusions. Considerable electricity and water use occurred during standby, load mass was only moderately predictive of electricity consumption and light loads were common yet inefficient. The findings of the present study are a baseline for steam sterilisation's environmental footprint and identify areas to improve efficiencies.