Another renewable option involves liquid biofuels- products such as ethanol and biodiesel made from plants and organic wastes. Unfortunately, growing most biofuel species (such as corn) and manufacturing and delivering the liquid fuel to consumers actually costs more in energy than it produces. Hydropower from dams is a renewable energy source but it too has drawbacks. For example, dams in rivers of the Pacific Northwest and California generate a great deal of electricity, but they also prevent endangered salmon from returning to streams above the dam to breed. As the salmon populations have suffered, so have endangered whales that feed on salmon in the ocean. There are other alternatives, although none has yet proven itself for widespread use. In windy places, the mechanical energy of wind generates electricity as wind turns giant turbines. Analysts have estimated that a wind power corridor" stretching from Texas north through South and North Dakota would