Sarau was born on June 7, 1839 in Segeberg, Germany. He moved with his parents to the United States in 1848, settling in Mishicot, Wisconsin. In 1854, he moved to Oshkosh, Wisconsin. He was assessor and then justice of the peace in Oshkosh. Sarau was admitted to the Wisconsin Bar in 1878 and was court commissioner. He died on August 24, 1903 after being struck by a street car while marching in a Knights of Pythias parade in Oshkosh, Wisconsin.