Take a look below to find the definition of some of the terms used on the HRRA website.

Use the Contact Us link to ask for additional definitions you’d like to see here.


A material containing bacteria which is used to start the composting process, eg dirt, manure or compost.

A process which occurs in, and needs, oxygen.

A light silvery-grey metal, which is commonly used for packaging.

A process which occurs without oxygen.


Tiny organisms which can turn plant and animal material into energy.

A renewable product, made from plant or animal material, that breaks down easily in the environment.

A substance or material which can be broken down by micro-organisms and other decomposers, such as fungi.

Biomass energy
Energy produced using organic matter.

Biomass fuel
Plant or animal matter which is used to produce electricity, by capturing and burning gases produced when the materials break down.

Bioreactor landfill
A landfill in which the biological reactions that occur when organic matter is broken down are used to produce energy.

The solid waste leaving wastewater treatment systems.


Carbon dioxide
A colorless odorless gas which is created naturally by burning fossil fuels, and is a major greenhouse gas.

Carbon monoxide
A colorless, odorless gas which is poisonous to humans. It is formed by the incomplete burning of carbon.

The dirt-like substance produced by worms breaking down organic matter.

Closing the loop
The process of using products made from recycled material, then recycling these products again when they become waste.

The process of burning something.

A dirt-like material resulting from the breakdown (or decomposition) of organic matter.

Recycling organic waste into compost, by speeding up the natural decomposition process, to release nutrients and minerals.

Any substances in a material which makes it impure.

To add something to a substance which makes it impure or unclean.

Broken or waste glass that is used in the manufacture of new glass.


To break down into smaller components.

Bacteria and fungi which break down dead plant and animal matter, returning nutrients to the soil or water.

A naturally occurring process where organic material is broken down by bacteria or fungi into smaller components.


Ecological footprint
A measure of the impact that an individual or a population has on their environment.

Devices and appliances that are run by electricity or batteries.

Substances (solids, liquids and gases) let out into the environment.

The natural or man-made surroundings in which people, animals and other organisms live.

A type of plastic expanded polystyrene used to make products like disposable cups and protective packaging.


A substance added to soil to make it more fertile.

A substance added to a furnace during metal smelting or glass-making which combines with impurities to form slag.

Fossil Fuels
Fuels created naturally beneath the Earths surface over long periods of time, from the remains of once-living things, eg coal, oil, and natural gas.

Fungus (Fungi)
Molds, mildews, yeasts, mushrooms and other organisms which obtain their nutrients from decaying organic matter.


A hard, brittle substance, usually see-through, which is made by melting together sand, limestone and soda and then cooling quickly.

Global warming
An increase in the average temperature of the Earth, thought to be caused by the greenhouse effect.

Greenhouse effect
A warming effect of the Earth’s atmosphere and surface, due to a build-up of greenhouse gases in the atmosphere.

Greenhouse gas
A gas which acts like the glass in a greenhouse, trapping heat in the earth’s atmosphere, to cause the greenhouse effect. Two of the most common greenhouses gases are carbon dioxide and methane.


Hazardous waste
Substances that can significantly harm the health of humans or the environment if they are not handled and disposed of correctly. Household hazardous waste consists of hazardous products used and disposed of by residential consumers, rather than industry.

A type of plastic high density polyethylene used for make containers like milk and detergent bottles.

Heavy metals
Metals which tend to accumulate in the food chain and can harm living things at very low concentrations eg chromium, cadmium, mercury and lead.


A substance used to kill or stop the growth of insects.


Landfill / Landfill Site
Disposal site for solid waste, where waste is buried and covered over with soil.

A type of plastic low density polyethylene used to make products like grocery bags and trash can liners.

Liquid containing contaminants from a landfill site.


A heavy metal that can build up in the environment and is very harmful if breathed or swallowed.

A natural gas produced when plant or animal matter breaks down. It is one of the major greenhouse gases and can be collected to produce biomass energy.

Any process that involves micro-organisms.

A microscopic organism, such as a bacteria, virus or fungus.

Material Recycling Facility
A facility where solid waste is sorted out for recycling or disposal in landfill.

Putting a layer of plant material (like straw, dead leaves or woodchips) around plants to hold moisture, stop weeds going and add nutrients to the soil.

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Any material which contains food or other products, and is used to transport, protect, and provide information about those contents.

Chemicals used when growing plants and crops, to kill unwanted insects, weeds and other pests.

A type of plastic polyethylene terephthalate used to make containers like soft drink and water bottles.

Crude oil and any products derived from crude oil that are liquids at normal temperature and pressure, eg motor fuel, jet oil, and lubricants.

Compounds made from chains of polymers, which can be moulded into rigid or pliable materials, for packaging, construction, fabrics, etc.

Long chained molecules made up of many smaller units, repeated many times. These units are often a combination of carbon and hydrogen, along with other elements added to change the properties of the polymer.

A group of interbreeding organisms (members of the same species) that live in a particular area.

Burying food waste in holes in the ground, where it breaks down, returning nutrients to the soil.

A type of plastic polypropylene used to make products like margarine containers and reusable and microwaveable containers.

Precious metals
Name given to gold, silver and platinum.

A type of plastic  polystyrene used to make products like yogurt tubs and CD cases.

A mushy mass of fibers from rags, wood or recycled paper, which is used to make paper and cardboard.

A type of plastic polyvinyl chloride used to make products like pipes and pipe fittings, and some bottles.


Radioactive waste
Waste products which emit radiation. Radioactive waste often lasts a long time in the environment and can be very harmful to living things.

Raw materials
Unprocessed substances, or resources, used to make new products.

Recovering and reprocessing materials that would otherwise become garbage.

Renewable energy
Energy produced from resources that can be used over and over again, eg solar energy.

Renewable resource
A natural resource which can be replaced once it is used up, or used over and over again, eg water, trees.

To fix items, so that they can be reused.

A material which is found naturally in the environment and is used for food or energy or to produce other materials. eg coal, timber.

To use materials again, instead of letting them become garbage.


Natural gas
A fossil fuel formed underground over millions of years from the remains of tiny dead sea plants and animals that were buried on the ocean floor. Natural gas burns cleaner and has fewer emissions than coal or oil.

Natural resource
A material which is found naturally in the environment and is used for food or energy or to produce other materials. eg coal, timber.

Non-renewable energy
Energy which comes from a source which can only be used once and cannot be replaced once it is used up, eg energy from burning fossil fuels.

Non-renewable resource
A natural resource which can only be used once and cannot be replaced once it is used up, eg coal, oil and natural gas.

Substances which are used by plants or animals as food.


Anything that is, or comes from, a living organism.

Organic waste
Any waste which comes from plant or animal matter.

A colorless toxic gas. Ozone is important in the upper levels of the atmosphere, to protect us from the radiation of the sun. But when it is produced close to the ground in photochemical smog it is a dangerous pollutant.


A material containing bacteria which is used to start the composting process, eg dirt, manure or compost.

The ability to use resources now in a manner which will allow them to continue to be used in the future.

A practice which does not put the environment or future resources at risk.


A silvery-white metal which is used to line steel cans, to protect the contents and prevent rusting.

The top layer of soil, which contains most of the available nutrients.

A material that is poisonous, and a risk to human health and the environment.


Anything that a person owns which is considered no longer useful and needs to be disposed of.

Worm farm
A type of compost bin that uses worms to help break down organic matter more quickly.