fertilizer from sunlight

So I thought, have a pond that grows algae, the algae use water and sunlight to create carbohydrates, feed the algae and water to a tank of yeast, the yeast eat the carbohydrates and produce alcohol, keep the alcohol and feed the dead yeast to bacteria, the bacteria eat the dead yeast to produce methane, keep the methane, and the dead bacteria can be used as fertilizer for plants. So from sunlight and water you get alcohol and methane some of which is used as fuels to drive the pumps that feed from one tank to another and you end up with fertilizer.