French engineer Pierre-Émile Martin was the first to take out a license for the Siemens furnace and apply it to the production of steel in 1865. The Siemens–Martin process complemented rather than replaced the Bessemer process. Its main advantages were that it did not expose the steel to excessive nitrogen (which would cause the steel to become brittle), it was easier to control, and that it permitted the melting and refining of large amounts of scrap steel, lowering steel production costs and recycling an otherwise troublesome waste material. It became the leading steel making process by the early 20th century.