He was a son of ship-owner Samuel Eyde (1819–1902) and his wife Elina Christine Amalie Stephansen (1829–1906).

He started his career in Hamburg, working with the railways where he planned new lines, bridges and stations.

In 1912 Eyde contributed to the development of Arendal Smelteverk at Eydehavn for the production of silicon carbide.

[7] In 1903, Eyde met with Kristian Birkeland, who was a scientist, inventor and professor of physics at the University of Christiania.

Birkeland was working on developing an electric arc, while Eyde had recently bought the rights to several waterfalls in Telemark.

This allowed Eyde to establish Det Norske Aktieselskap for Eletrokemisk Industri (today Elkem) along with members of the Wallenberg family who he had met in Sweden.