The son of a carpenter who died when he was 8, Grünewald apprenticed as a baker but found work difficult to come by when the First World War ended and the demobilised soldiers entered the labour market. Attracted to the nationalist propaganda prevalent at the time Grünewald joined the Freikorps before signing on with the army for a 12-year stint. Leaving the army as a staff sergeant in April 1931 Grünewald again struggled to find employment and so joined the Sturmabteilung. He rose to the rank of Obersturmbannführer in the SA before switching to the SS shortly after the Night of the Long Knives.
In 1943 he succeeded Karl Chmielewski as commandant of Herzogenbusch concentration camp however like his predecessor he too was tried and found guilty of causing the deaths of prisoners by excess cruelty, in his case for the Bunker Tragedy. He was sentenced to fifteen years imprisonment but was then pardoned. He finished the war with the 3rd SS Division Totenkopf and died in battle. His final rank was SS-Sturmbannführer.
- Tom Segev, Soldiers of Evil, Berkley Books, 1991, p. 71
- Robert Melvin Spector, World Without Civilization: Mass Murder and the Holocaust, History and Analysis, Volume 1, University Press of America, 2005, p. 375
- Segev, Soldiers of Evil, p. 153
- Ernst Klee: Das Personenlexikon zum Dritten Reich: Wer war was vor und nach 1945. Fischer-Taschenbuch-Verlag, Frankfurt am Main 2005