Recyclability

At the end of service life, a cable can be recovered for recycling or left in place. With older oil-filled cable technology, leaving the cable in place may have risks associated with long term oil leakage. Modern XLPE cables, however, can be left in situ with little risk of release of hazardous substances. Of course, good environmental stewardship dictates that recycling should be a preferred option for XLPE cables, if possible.

A modern cable has three recycling-related aspects to consider:

1. Recovery of cables: Recovering a cable can require considerable excavation work, depending on the nature of the installation. Direct excavation is relatively costly, while physically dragging up the cable from the soil is significantly cheaper.
2. Recyclability of copper: A large power cable system may have three conductors, each with a 2500 mm2 cross section of copper. Each kilometer of this cable contains around 25 tonnes of copper whose scrap value can cover the costs of recovering the cable from the ground. This copper is fully recyclable into new copper products of all types, including electrical grades and new cables. Recovering this copper saves around 70 tonnes of CO2 emissions.
3. Dealing with cross-linked polyethylene: The polyethylene in a power cable is a special grade, which has cross-linked molecules to allow it to deal with extremely high temperatures without melting or flowing under load. This also means that it cannot be remelted once it has been stripped from a cable. This makes XLPE sheathing similar to rubber vehicle tyres, which are made from a cross-linked polymer. Options for dealing with cross-linked polymers include:
   • Energy recovery in cement kilns
   • Conversion into a crumb or power for use as a filler mixed with virgin material
   • Depolymerisation, the breaking down of the molecules into feedstock gases and feeding back into petrochemical processes

It is likely that given the low quantities of cable sheathing likely to enter the market, developing a specialist recycling route and associated specifications would not be worthwhile. Therefore, energy recovery is likely to be the most attractive solution, which displaces fossil fuels and avoids use of scarce landfill space.