Short answers, pulled from the story.
Charles Martin Hall and Paul Héroult independently discovered the method to produce aluminium in 1886. Paul Héroult filed French patent number 175,711 on the 23rd of April 1886 and received it on the 1st of September 1886.
The Hall, Héroult process allows electrolysis to occur between 940 and 980 degrees Celsius. Liquid aluminium reaches a density of 2.3 grams per milliliter near 950 degrees Celsius while pure cryolite melts at 1007 degrees Celsius before alumina addition.
Over 12 tons of carbon dioxide emissions generate per ton of aluminium produced through the Hall, Héroult process. This reaction occurs when oxygen from the alumina combines with carbon anodes to form mostly carbon dioxide gas.
Charles Martin Hall opened his first large-scale plant in Pittsburgh in 1888 which later became known as the Alcoa corporation. Modern facilities often locate where cheap electric power is available such as Iceland or Quebec.
Factories operate these cells twenty-four hours a day to prevent solidification of the molten salt bath. Temperature inside the cell relies on electrical resistance to maintain stability and ensure liquid aluminium sinks to the bottom for collection.