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Waste glossary

This glossary explains some of the technical words about solid waste used by Waikato Regional Council.


Processed sludges from industrial activities (excluding agricultural effluents) that may be suitable for reuse as soil conditioners or fertiliser substitutes.


A type of landfill licensed to only take harmless waste, such as excavated soil or demolition rubble.

For the Waikato Regional Plan definition, click here.

Co-generation plants

Co-generation plants generate electricity and use the waste heat produced for another purpose, for example, some dairy factories use the excess heat to heat water.


At water treatment plants, a chemical, the “flocculant” is added to the waste water which makes dissolved or suspended solids heavy so that they settle into out, and can then be removed. The solids, which have come out of solution, are called “flocculated” solids.

For the Waikato Regional Plan definition of flocculation, click here.

Grease traps

Grease traps are settling systems designed to trap grease and suspended sediments in industrial liquid waste streams. Generally, grease traps consist of a grill and sump. They are used in mechanics’ workshops, service stations and a wide range of other industrial activities.

Hazardous substances

Any substance which is explosive, flammable, corrosive, toxic or oxidises other materials.

For the Waikato Regional Plan definition, click here.

Landfill gas

Gases such as methane and carbon dioxide (CO2), which are emitted from landfills as organic matter in the landfill rots.

Landfill gas can be a problem if there are houses near landfills, as the gas is very explosive if it is trapped in confined spaces, such as basements or closed drains. Landfill gases are also greenhouse gases (contribute to global warming through the greenhouse effect).


Leachate is rainwater that seeps through the landfill and becomes contaminated. If not contained and managed properly, leachate can get into our waterways, coastal areas and ground water, polluting them.

Organic material

Organic material is anything that originally came from a plant and or an animal (including garden and kitchen waste or manure), which can decompose naturally.