Pioneered the hot-water recovery process for extracting oil from tar sands.
A chemist, Clark developed an interest in tar during his first post-university job as chief fof the federal Mines Branch's Road Materials Division. In 1921, he joined the Alberta Research Council, an arm of the University of Alberta the purpose of which was to apply science to the development of local resources.
The Athabasca oil sands of northeastern Alberta make up an enormous deposit of thick, tar-like crude oil mixed with sand and other materials. Clark's hot water flotation process separated oil from bituminous sand by mixing the oil sands with hot water, then aerating the resulting slurry and floating the oil off as an oil froth.
With the help of Sidney M. Blair and David Pasternack, Clark developed the first pilot plant to extract oil from these sands. Built in the basement of the U of A power plant and using a supply of tar sand provided by Thomas Draper of the McMurray Asphaltum & Oil Company, the plant was able to process 85 tons of sand. High heat costs and frequent shutdowns plagued this early project.
Over the next 20 years, Clark produced a series of experimental oil sands extraction facilities. Increasingly successful technically, these still suffered from economic woes and political disinterest, as well as periodic fires. In 1949-50, the Bitumount facilty near Fort McMurray opened and demonstrated the technical feasibility of the hot water extraction process. By 1949, the plant was processing 450 tonnes of oil sand a day, but it was closed because the government was not interested in launching a commercial venture.
For the last years of his career, Clark acted as a consultant for Great Canadian Oil Sands (later Suncor Ltd.), the first economically successful tar sands plant. The plant opened in 1967, the year following Clark's death. A second operation, Syncrude Canada Ltd., was built in the 1970's. Initially licensed to produce 125,000 barrels a day, Syncrude has now produced over a billion barrels of oil using Clark's process, and presently supplies 13 percent of the nation's petroleum requirements.