The disposal of refuse waste from commercial and domestic premises is an ongoing problem in many countries. In the United Kingdom, around 85% of household waste is recycled, and around 15% goes to landfill. In major cities such as London it is increasingly difficult to find landfill sites, since many of the disused quarries around the cities are now full to capacity with waste. Further, there are increasingly stringent regulations concerning the proportions of waste which must be recycled. Governments and local authorities are increasingly discouraging the use of landfill by increasing taxes on waste sent to landfill, which are currently around £80 per tonne in the United Kingdom.
In United Kingdom, around 4 to 5 million tonnes of refuse waste is incinerated each year in the form of refuse derived fuel (RDF). Around 15% of this RDF is shipped out to the Netherlands for incineration to generate electrical power. The transportation of bulk RDF causes increased CO2 emissions as well as being expensive.
The RDF is packed into bales which are compressed and held together with wire straps and covered in plastic in order to contain smells from food waste and other waste constituents, and also to keep the moisture content of the RDF stable during storage and transportation. Ingress of water into bales during storage and transportation increases the weight of the bales and also reduces the combustion efficiency of the RDF at its final destination of incineration. During storage and transport, bales of RDF can stand in the open exposed to the environment for up to 2 months before they are finally incinerated.
To reduce volume for transport and storage, the RDF is compressed into bales under a force of around 100 tonnes. A problem with known bales of RDF wrapped in steel wire is that the steel wire needs to be cut to recover the steel wire, prior to incineration of the RDF, both to recycle the steel wire, and to prevent the steel wire damaging and/or reducing the efficiency of the incinerator. When the wire is cut, the bales unfold and expand over a large area. The released RDF is then pushed into an incinerator using a bulldozer or similar mechanical handling equipment.
The use of metal wire for producing bales of RDF allows for high compression of bales and for efficient transport of the bales without the bales coming apart. However the unwrapping of the bales prior to incineration and loading into an incinerator using a bulldozer or other mechanical handling equipment means that the bales revert to loose RDF at their final destination immediately prior to incineration. It is difficult to control the burn rate of incinerators by feeding in loose RDF, since the quantity of RDF fed into the incinerator is difficult to control and consequently the rate of production of power at RDF burning power stations has limits on its controllability.