Autoclaves are closed chambers that apply both heat and pressure, and sometimes steam, over a period of time to sterilize medical equipment. Autoclaves have been used for a century to sterilize medical instruments for re-use. Surgical knives and clamps, for instance, are put in autoclaves for sterilization.
For medical waste that will be disposed of, autoclaves are a heat treatment are used to destroy microorganisms that may be present in medical waste before disposal in a traditional landfill.
Autoclaves are best for wastes that are unlikely to produce combustion or substantial off-gas. While incinerations can be built with pollution abatement systems, autoclaves are smaller and it is not economical to unit make a treatment system for vapors emitting from the unit.
Autoclaved medical waste is usually compacted after it cools down. The compaction process may include shredding before the compression. The compaction process reduces the volume of the treated waste significantly.
One problem with autoclaves is that the process can aerosolize chemicals present in the waste, leading to the potential for release of materials you would prefer to not release. This can pose a hazard to human operators and to some extent the environment – even though the facility HVAC system may take much of the brunt. It is possible this aerosolized material will deposit on surfaces in the facility – much as what happens in your kitchen. This is the source of much grime in kitchens.
Are autoclaves a substitute for incineration? Yes, to a large extent. Autoclaves can be used to process the large bulk of infectious waste produced at a hospital or clinic. Autoclaves come in a wide range of sizes and capacities. If you have steam in your facility, you can hook it up to a steam autoclave. Other autoclaves produce steam by electric heating.
Autoclaves are basically dumb hot chambers and with a combination of time and temperature you can sterilize pretty much anything, so there is a temptation to put all sorts of medical waste in it. While autoclaves were first used (over a century ago) to sterilize medical instruments so they could be reused, when people started worrying about infectious waste they were throwing away, the autoclave was sitting there and able to accomplish the disinfection/sterilization needed.
Modern medical waste management systems incorporate autoclaves for processing of waste cultures, sharps, gauzes, bandages, and more. Some surgery waste and plastic and metal waste contaminated with blood or other bodily fluids are put into autoclaves.
Autoclaves are "chemical free" and that appeals to many stakeholders in a complex waste management environment. Small autoclaves can be installed at the point of waste creation, removing the need to transport waste to an external treatment facility.
What can’t you put in an autoclave? Well, you can’t put in hazardous waste. You can’t put in heavy metals and expect them to be not hazardous when it comes out.
Could pathological waste - human tissue - be treated in autoclaves? In theory yes, In practice, no. Human and animal flesh has lower thermal conductivity than metal, so a longer time in the autoclave would be required than for surgical instruments of comparable size. There is also a concern that autoclaved pathological waste may contain low levels of radioactive material or cytotoxic compounds that has survived the heat. So that is a challenge for the engineer trying to determine appropriate residence time. But that sort-of doesn’t matter as the rules and norms in most parts of the world call for incineration of pathologicial waste.