Waste autoclave

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A waste autoclave is a form of solid waste treatment that utilises heat, steam and pressure of an industrial autoclave in the processing of waste. Waste autoclaves process waste in batches. Saturated steam is pumped into the autoclave at temperatures around 160°C ^[1]. The pressure in the vessel is maintained at 5 bar gauge for a period of up to 45 minutes to allow the process to fully 'cook' the waste. The autoclave process gives a very high pathogen and virus kill.

[edit] Process results

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The 'cooking' process causes plastics to soften and flatten, paper and other fibrous material to disintegrate into a fibrous mass and bottles and metal objects to be cleaned and labels etc to be removed. The process reduces the volume of the waste by ~60%. After 'cooking', the steam flow is stopped and the pressure vented via a condenser. When depressurised, the autoclave door is opened, and by rotating the drum the 'cooked' material can be discharged and separated by a series of screens and recovery systems.

The primary product is a fibre. This comprises the putrescible, cellulose and lignin elements of the waste stream. The biodegradability of putrescible waste has not been effected by the autoclave and so must undergo further treatment to reduce its reactivity prior to landfilling. The fibre can be fed into anaerobic digesters to reduce the biodegradability of the waste and to produce biogas. Alternatively the fibre could constitute a refuse derived fuel.

The secondary streams comprise of mixed plastics, which have normally been softened and deformed which eases separation, a glass and aggregate stream, which can be exceptionally clean of both plastic and paper, and separate ferrous and non ferrous metals. The heat and steam and rotating action of the autoclave vessel strip off labels and glues from food cans leaving a very high quality ferrous/non-ferrous stream for recycling.

The full process of loading, treatment and sorting is normally completed within 90 minutes.