During World War I the Germans needed glycerol to make nitroglycerin, which is used in the production of explosives such as dynamite. Before the war, the Germans had imported their glycerol, but the British naval blockade during the war prevented such imports. The German scientist Carl Neuberg (1877–1956) knew that trace levels of glycerol are produced when the yeast Saccharomyces cerevisiae was used during the alcoholic fermentation of sugar. He sought and developed a modified fermentation process in which the yeast would produce significant quantities of glycerol and less ethanol. The production of glycerol was improved—and Neuberg’s procedure was implemented with the conversion of German beer breweries to glycerol plants, which produced 1,000 tons of glycerol per month. After the war ended, the production of glycerol was not in demand, so it was suspended.