According to the EC (19 November, 2008) “waste means any substance or object which the holder discards or intends or is required to discard.” Recycling materials and products – that are considered waste - is an ancient practice which shows that in times of resource scarcity (i.e. shortage of virgin materials) societies attach more economic and societal value to their own waste. This implies that throughout time the definition of waste can change as well. Generally speaking longer use or re-use of materials and products this is often mainly to cover a society’s needs.

Under the anaerobic (oxygen free) conditions of landfill sites, organic waste is broken down by micro-organisms, leading to the formation of landfill gas (LFG). LFG is a gaseous mixture which consists mostly of methane and carbon dioxide, but also of a small amount of hydrogen and occasionally trace levels of hydrogen sulphide.