Friedrich Wilhelm Erich Kaiser studied in the natural sciences and mathematics at the universities of Marburg, Munich and Bonn and worked as an assistant at the Institute for Mineralogy, University of Bonn, from 1894 to 1900. In 1897 he qualified as Doctor of Philosophy (D Phil) at the University of Bonn with a thesis on Versuche ueber das zusammenfliessen zweier fluessigkeitsmassen. That same year he became one of the university's private lecturers. However, in 1900 he was appointed at the Prussian Geological Institute in Berlin, while he also lectured at the Berlin Bergakademie (School of Mines). He carried out geological-agronomic surveys in the Rhinelands, prospected for minerals, and conducted pioneering studies on the erosion of building stone. In October 1904 he became professor of mineralogy at the University of Giesen, where he remained (with some interruptions) until October 1920. During this period he described the petrographic collections made by Heinrich Lotz* in German South West Africa (now Namibia).
In 1914 Lotz invited Kaiser to come to Namibia to continue his studies in the field. He arrived in July that year, but a few months later World War I (1914-1918) broke out, with the result that he served as an officer in the German Schutztruppe (colonial forces) in Namibia until September 1915, when the German troops surrendered to South African forces. During this period he collected information on the diamond deposits of the territory in his spare time and subsequently continued his geological and topographical studies of the southern Namib in collaboration with P.F. Werner Beetz*. Their results were eventually published in Kaiser's monumental work Die Diamantwueste Suedwestafrikas (2 vols, 1926). This work included reports by petrographers and palaeontologists who had studied the specimens sent to Germany by the two field workers. It also dealt with underground water, desert formation, and the effects of desert winds. Other publications by Kaiser on the geology of Namibia and South Africa, numbering more than 30, included the following: "Ueber Diamanten aus Deutsch-Suedwestafrika" (Centralblatt fuer Mineralogie, Geologie und Palaeontologie, 1909); "Die Suedafrikanischen Diamant Vorkommen" (Oberhessische Gesellschaft fuer Natur- und Heilkunde, 1912); "Studien waehrend des Krieges in SWA" (Zeitschrift der Deutschen Geologischen Gesellschaft, 1920); "Kaolinisierung und Verkieselung als Verwitterungsvorgaenge in der Namibwueste, Suedwestafrikas" (Zeitschrift fuer Kristallographie, 1923); "Surface geology in arid climates" (Transactions of the Geological Society of South Africa, 1927); and "Die junge terrestre Sedimentation in Sued- und Suedwestafrika" (Zeitschrift fuer Praktische Geology, 1929).
Kaiser returned to Germany after the war and in October 1920 was appointed professor of general and applied geology at the University of Munich, a post he held until his death in 1934. He returned to southern Africa in 1927, visiting the diamond fields at Alexander Bay and the manganese deposits near Postmansburg. Two years later he came down south for the last time, to attend the Fifteenth International Geological Congress in Pretoria. At this time the University of Cape Town conferred on him an honorary Doctor of Science (DSc) degree. He also used the opportunity to travel to Southern Rhodesia (now Zimbabwe), Northern Rhodesia (now Zambia), and Namibia.
Kaiser was co-editor of the Zeitschrift fuer Kristallographie for some time, and from 1922 co-editor of the Neues Jahrbuch fuer Mineralogie, Geologie und Palaeontologie. A terrestrial mollusc, Dorcasia kaiseri, was named after him. He was married to H. Rauff.