He was the youngest son of Joseph-Désiré Hannon (1822–1870), doctor of natural sciences and medicine, and professor at the Université libre de Bruxelles (ULB).

Édouard became a civil engineer, graduating from the École polytechnique in Ghent in 1875, then joining the Solvay Company in 1876, where he became technical director (1883),[1] and then one of its managers (1907–1922).

He was the longtime head of Solvay's soda plant in Dombasle-sur-Meurthe, France, just south of Nancy, where he became attracted to the works of the Art Nouveau artists Emile Gallé and Louis Majorelle.

En 1894, he won the gold medal at the first exhibition of the Photo-club de Paris with his Matinée d'Automne ["Autumn Morning"] and participated in international photography shows in Berlin (1896) and Brussels (1902).

His name is perpetually associated with the Hôtel Hannon, an example of Art Nouveau architecture where he lived from 1904 onwards, and which housed, from 1988 to 2014, his collection of photographs as part of the Espace photographique Contretype.