Investigating the energy, environmental, and economic challenges and opportunities associated with steam sterilisation autoclaves

Despite steam sterilisation in autoclaves being a common industrial method of sterilisation, very little research has been conducted into quantifying the resources these processes demand and their associated environmental impacts. This paper aims to investigate industrial steam sterilisation in autoclaves with particular application to the biopharmaceutical industry. A mathematical model of a steam autoclave was developed to examine relationships between load size, load material properties and autoclave capacity with energy consumption, environmental impact and cost of sterilisation. The two main energy requirements are thermal energy to produce the clean steam for sterilising, and electrical energy for the vacuum pump. The study showed that thermal energy is dominant, particularly as load increases. The percentage of the maximum load at which the autoclave is operated has a major impact on the specific energy requirement or the energy required to sterilise per unit mass of load. For a given autoclave, the energy requirement increases with increased load but the specific energy requirement decreases. This in turn impacts on the emissions and the energy cost. It is thus shown that it is much more energy efficient to operate at higher loads, making the autoclave much more energy and cost effective, and with less environmental impact. There is potential for applying the analysis presented in this work for conducting optimisation studies for determining the sizes of autoclaves that could minimise the energy requirement, environmental impact and economic cost (3E) of investments for specified load versus time profiles.