A description of the application
A transmission power cable uses overhead or underground technology. Typically it consists of conductor bundles - copper or aluminium - and insulation material, mostly different kind of plastics. Considering the overhead lines there is no need of an insulator, but in the case of aluminium bundles, usually a core of steel is necessary for ensuring required strength.
The challenges that appear regarding this application
The End-of-Life of transmission cables depends on the technology used.
In the case of overhead technology, the materials will be recycled, as they are clearly and easily identifiable, their disassembly and separation is a simple process and thus the efforts make the process worth it. Aluminium goes into secondary aluminium recycling, typically a re-melting and steel goes into secondary steel production, typically electro furnace.
In the case of underground technology, this is not so straight forward and easy.
Considering the copper, the recycling of the cables is usually economically viable.
In the case of aluminium, it depends on the amount collected and on the effort to collect it, e.g. civilization barriers, depth, length and width of digging, logistics interruptions due to digging and many more. So, in some cases, the aluminium cables may remain underground on their End-of-Life getting lost.
If the material of the cable is not known, the cables might be collected due to their potential economic interest – even if not for sure, they might be copper cables, which are in any case economically relevant.
How copper serves as a key factor to overcome this hurdle
In the End-of-Life, there are usually four different aspects to consider that influence the recycling:
- Identification of value
- Collection rate
- Yield of the recycling process
In the context of the End-of-Life of underground cables, the identification of value and the collection rate are aspects which sometimes are not clear: visual inspection is not easy and in some cases, since the cables were installed a long time ago, it is no longer possible track back if the material is copper or aluminium.
In this sense, copper drives the recycling of underground cables, since its value motivates the collection even without a clear identification of related cost and efforts for excavation. Certainly, once the cables are collected, they will be recycled in both cases.
Even in the situations when this is not profitable from an economic perspective (for example, if the cables are aluminium), the recycling of these metals is beneficial from an environmental point of view. This is particularly relevant especially because in both cases, copper and aluminium, can substitute primary materials, avoiding the burden of extracting them from the Earth crust.
In the case of copper, it can be even used in the same application (cables), as the copper is purified back to electrolytic copper (99.999% pure copper) – full closed loop.
In the case of aluminium, it will probably not be used in the cables application due to the lack of exact specification in terms of alloy composition. But it can be used in other applications and even replace primary aluminium where the alloy composition doesn’t affect the intended property.
The key message as a conclusion
Copper drives the recycling of underground cables, since its value motivates the collection of underground cables. Even if there is only the estimation that it is copper and a clear identification is not possible, the potential benefit of underground buried value motivates an excavation.
Besides the direct economic uncertainty, closing the loop is in any case (aluminium or copper) beneficial from an environmental perspective. Moving towards a more circular economy allows saving on primary raw materials, reducing the environmental impact.
Furthermore, recycling of metals in general has a positive effect in the management of supply challenges, such as mitigation of dependency on metal providing countries, volatile metal prices, import taxes, logistics, insurance and in-time delivery.
Copper or Aluminium cable conductors, broadly compared in a life cycle perspective. BOONE, BAL (DNV GL) KACKER (PE- International); 2015