how it works


The STERM™ is a thermal drying process that produces – in an economical and environmentally friendly way – a high-grade sterile fuel from bio-solids resulting from the wastewater treatment process. The fuel produced by the system provides the energy to run the STERM™, leaving only an inert sand/ash as the end product.

The STERM™ takes dewatered bio-solids through a proprietary drying process, converting them into sterile fuel source. The moisture-laden air is sterilized and deodorized and the fuel created is recycled back through a special combustion process to provide energy for the system. The inert sand/ash end product of the combustion process has offsite uses as an aggregate in concrete or plaster, or as road fill.

Although the STERM™ is capable of processing primary, secondary and digested sludge, it is primary undigested sludge that provides the highest specific energy, leaving a fuel surplus available for off-site uses, e.g. energy co-generation.

In addition to creating its own energy, the STERM™ has only three principle outputs from the process:
   •  Surplus sterile fuel source (from processing primary undigested bio-solids).
   •  Exhaust gases (filtered and deodorized).
   •  Inert sand/ash (7% of wet volume of bio-solids introduced to the process).

Proof of concept was achieved in November 2006. Following proof of concept, the plant has been converted to commercial standard to allow the finalisation of an Enviro Energy-Hamilton City Council contract to eliminate up to 25% of the city’s digested sludge each day.

Enviro Energy is now ready to manufacture the STERM™ 2000 which has a processing capacity of up to 100 wet tons per day. The STERM™ can be installed in parallel for processing volumes greater than 100 tons and is suitable for use in either new treatment facilities or can be retro-fitted to existing facilities.