The Great Algae Race
Figure 1. Experimental setup for "The Great Algae Race."Copyright 2013 Robert Bair, University of South Florida
In a multi-week experiment, student groups gather data from the photobioreactors that they build to investigate growth conditions that make algae thrive best. Using plastic soda bottles, pond water and fish tank aerators, they vary the amount of carbon dioxide (or nutrients or sunlight, as an extension) available to the microalgae. They compare growth in aerated vs. non-aerated conditions. They measure growth by comparing the color of their algae cultures in the bottles to a color indicator scale. Then they graph and analyze the collected data to see which had the fastest growth. Students learn how plants biorecycle carbon dioxide into organic carbon (part of the carbon cycle) and how engineers apply their understanding of this process to maximize biofuel production.
Environmental engineers grow algae in photobioreactors for biofuel and fertilizers, or to treat wastewater. To grow successfully, algae need adequate carbon dioxide, which is one of the conditions students test in this activity. Algae sequester carbon dioxide during photosynthesis, making biofuel production a potentially closed loop system. Thus, for engineers, this process serves as a way to biorecycle excess carbon dioxide in the atmosphere or generated from industrial processes such as electricity production, into organic carbon and biofuel.
After this activity, students should be able to:
- Explain how algae use carbon dioxide to grow during photosynthesis and how its availability affects their growth rates.
- Describe a photobioreactor and explain its purpose.
- Demonstrate how to record, analyze and interpret data.
- Describe the difference between renewable and nonrenewable energy.
- Describe how biofuels fit into the carbon cycle and how they biorecycle carbon dioxide into energy.