(428f) Photobioreactor Design & Algae Biodiesel Production Teaching Module

The area of photobioreactor (PBR) design for the purpose of producing algae biofuel holds many opportunities for teaching core chemical engineering concepts.  Concepts of reactor design and microbial growth are of obvious importance.  Additionally, the necessity to keep algae suspended in a PBR introduces concepts of fluid dynamics.  Light penetration and dissolved gas concentrations provide additional design consideration which may be related to beer’s law and thermodynamics.  Solvent extraction and two phase reactions may also be introduced during the processing of the algae into biodiesel.

Lab modules based on algae biofuels are also highly desirable among our student body.  Biofuels are of significant interest to a large portion of students due to their potential as a carbon neutral source of energy.  Furthermore, because the technological hurdles in scaling-up production of algae crops have yet to be overcome, this area is also an interesting example to students of the type of unsolved problems faced by practicing engineers.

To capitalize on this interest and educational potential, we have developed a PBR/biodiesel teaching module that has found wide use in both our curriculum and outreach efforts.  In this open-ended design module, students are given access to a wide variety of containers, air and liquid pumps, spargers, tubing, and lighting options.  We have amassed a materials list of inexpensive, yet effective components which allow this project to be accomplished with little investment. Each team begins with the same concentration of algae and nutrients from a common source.  After being given some instruction and preliminary data, students are asked to design a reactor to grow algae as quickly and efficiently as possible, within several other design constraints.  Over a two week period students track algae growth using optical density measurements.  While the algae are growing, students convert a variety of biological oils into biodiesel, compare their products using a range of analytical techniques, and complete a project on scaling-up their process.  Once the module is completed the students should be able to use their data to identify phases of batch microbial growth, and calculate doubling times and maximum growth rates within their reactor.

In student surveys, this teaching module has been ranked well above average in both enjoyment and educational effectiveness by students. The teaching module or some variant has found use from our freshman design laboratory to our senior capstone lab, proving itself to be versatile in its sophistication.  Furthermore, PBR design projects have been an important outreach tool for our department, used in several summer camps and in a two-week introduction to chemical engineering course taught by our outreach team for a local high school.