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Waste stock enters one end via a bin tipper or feed hopper. A rotating tine-bearing shaft the length of the unit turns intermittently, in both forward and reverse directions to ensure the mix is uniform and moisture and heat is evenly distributed. Air is injected along the length of the cylinder ensuring the material is maintained in an aerobic state and the composting process proceeds at an optimum rate, without the evolution of nuisance odour. As the shaft rotates it releases excess heat, moisture and carbon dioxide which are extracted by fan and passed through a bio filter.

All HotRot units are fully enclosed and insulated meaning they do not need to be housed in a building, thus minimising capital and maintenance costs. It also means the significant problems of moisture and by-product gas build-up causing corrosion of structures and electronic components observed in within-building composting systems are completely avoided. The insulation protects the process from the influence of fluctuating ambient environmental conditions, including solar heat gain and moisture loss. The insulation is very effective; HotRot units operate effectively outdoors in Nova Scotia (-25C) and Papua New Guinea (32C). HotRot units are designed to provide optimal environmental conditions to maximise the natural composting process. Neither artificial heat nor microbes are added to the process.

Material is automatically discharged from the HotRot unit via a combination of shaft rotation and displacement down the unit, caused by waste additions at the opposite feed end of the unit. Material takes approximately 10-12 days to pass down the length of the vessel. Composted product is highly stable and mature on discharge (a maturity equivalent to that of windrow composted material after 6-9 months); the product is largely odour free with a slight "musty" or "earthy" smell. At this point the compost conforms to recognised compost standards however we recommend it is temporarily windrowed for 2-4 weeks to allow nitrogen fixing to complete. This also allows for sampling and quality assessment.

Each HotRot unit is equipped with monitoring equipment that provides on-line diagnostic facilities and an auditable record demonstrating compliance with international regulatory guidelines and standards.The HotRot composting system is fully modular allowing plant capacity to be easily extended by installing additional units as collection services or demand increases. Modularity also allows the plant to be configured to produce niche products from defined feed materials.

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