A U.S. company this week began pumping a mix of an algae-based biofuel and gasoline at gas stations in California, a pilot project the company hopes will be a first step in providing a large-scale alternative to fossil fuels. The fuel, known as Biodiesel B20, contains 80 percent petroleum and 20 percent algae grown by San Francisco-based Solazyme. The fuel is produced in a fermentation process at Solazyme’s Illinois plant that combines sugar with an organism company officials will not identify. According to the company, the new fuel blend produces 30 percent fewer particulates, 20 percent less carbon monoxide, and 10 percent fewer hydrocarbons than other biodiesel fuels. So far, the fuel is being sold for diesel vehicles at four gas stations in the Bay Area for $4.25 per gallon, which is also the average price right now for diesel fuel in California. But Propel Fuels, which is providing the infrastructure for the fuel delivery, hopes to make the fuel available at hundreds of California stations, said Matt Horton, Propel’s CEO.