SAN DIEGO -- Tim Zenk is surrounded by green. In a lab near California's coast, shades of emerald, lime and chartreuse fill petri dishes, beakers, 14-foot plastic bags and long swirling pools. When Zenk looks around, he also sees gold. Inside the 70,000-square-foot lab sit thousands of strains of algae, the slimy substance that grows in swamps and dirty swimming pools. Sapphire Energy, the entrepreneurial company where Zenk works as vice president of corporate affairs, wants to turn the green liquid into fuel for cars, trucks, jets and potentially far more. Algae could someday shift the country's energy mix, Zenk said, blunting some of the need for oil and helping to limit climate change.