Anglesey Aluminium Metal Ltd., which shut down on 30 September 2009, was a joint venture between the Rio Tinto Group and Kaiser Aluminum. Its aluminium smelter, located on the outskirts of Holyhead, was one of the largest employers in North Wales, with 540 staff members, and began to produce aluminium in 1971. It was built on the Penrhos Estate, 500 acres of which were sold by the Stanley family for the project. Up until its closure it produced up to 142,000 tonnes of aluminium every year and was the biggest single user of electricity (255 MW) in the United Kingdom. Alumina and coke shipped from Jamaica and Australia would berth at the company's private jetty in Holyhead harbour. This jetty is linked by a series of conveyor belts passing through tunnels to the plant. A spur rail link from the main Holyhead to London rail line runs into the plant and was used for both receipt of raw materials and despatch of aluminium.
The plant was powered from the National Grid and received most of its electricity from Wylfa nuclear power station 15 miles away. AA was used as a base load for Wylfa and saved the grid the cost of keeping a power station on standby. The power contract terminated in 2009, and the aluminium smelting operation was shut down as no new contract was negotiated. The company has announced tentative plans for a biomass plant on the site, but smelting operations have been halted and the plant mothballed until 2016.