When an electrolytic pot reaches the end of its life, it is taken out of production and its contents are removed before it is rebuilt and put back into production. This process is called relining.

The waste product of this process is called spent pot lining or SPL. Since SPL contains fluorides, among other things, it is classified as hazardous waste. For a number of years, Hydro's primary metal plants in Norway have delivered this waste to disposal sites operated by the company NOAH on Langøya, outside Holmestrand in Vestfold county.

Used in the production of insulation

Under the recently signed contract with Rockwool, Hydro will separate the carbon-rich material from the SPL and deliver it to Rockwool's preprocessing plant in Germany. There Rockwool will crush the carbon and prepare it for use in its production of rock wool which is an important component in fireproof insulation.

"Rockwool uses such high heat in its production process that the harmful substances in the spent pot linings are destroyed. Therefore, this agreement is a very good environmental option," says Kristin Mørkved, manager of the SPL project in Hydro.

Director of group sourcing and procurement in Rockwool, Peter Løgtved, says both companies and the environment gain from the project.

"With this agreement, we ensure a good solution for our companies' bottom lines. At the same time, what used to be a hazardous waste now becomes a valuable resource," he says.

Reducing waste going to landfill

Hydro's executive management has previously set a target to reduce the 2010 level of waste to landfill by 60 percent by 2020. In addition, the Primary Metal business area has a target that 70 percent of annual waste generated will be recycled by 2020.

"This contract will make an important contribution to meeting these goals since it ensures that approximately 45 percent of our used pot linings will be recycled," says Mørkved.

The project already signed another contract last year to supply anode waste to Norcem's cement plant in Brevik in Telemark county.

Millions in savings

In addition to an environmentally beneficial impact, it is expected that the agreement with Rockwool will result in annual savings of about NOK 5 million.

"The agreement runs initially to the end of 2013, with an option for both parties to extend and renegotiate," explains Mørkved. She also adds that a formal export approval must be obtained from Norway's Climate and Pollution Agency (Klif) before the agreement can be implemented.

"The application process for this approval has started, and we have a good dialog with Klif," says Mørkved.