(372j) Photobioreactor Design and Biodiesel Synthesis

Branch, K., University of Utah
Butterfield, A., University of Utah
The negative environmental impacts of combustion are well-known. As part of our introductory-level chemical engineering design and innovation lab, students learn about biodiesel as an alternative, cleaner, carbon-neutral fuel for diesel engines. Students are taught about the possibilities and difficulties associated with growing algae on a large scale, extracting the oil from it, and converting it to biodiesel. In the lab, students work in teams of three and are tasked with designing and constructing a photobioreactor for optimizing the growth of algae while minimizing water evaporation. Students track the algae growth over the course of four weeks by measuring its optical density with a spectrophotometer each day and obtain a cell count using a hemocytometer at the beginning and end of the project. While the algae are growing, the students synthesize biodiesel from their choice of a wide variety of other starting oils, such as vegetable, corn, olive, canola, peanut, avocado, and more. Students then analyze their biodiesel and traditional diesel for flame temperature, burn rate, qualitative viscosity and density. They further analyze their biodiesel using a variety of analytical equipment, including an FTIR-ATR, UV-Vis spectrophotometer, and refractometer.

Each group of students submit all of their collected data from the two projects and are then tasked with analyzing the data from the entire course, combining their own group’s data with that of their peers. Students must first assess the reliability of the various data sources and determine, with justification, which data they believe is inaccurate and should be omitted from the analysis. Their objectives are then to identify which photobioreactor designs are most effective and which starting oil yields a biodiesel product most similar to traditional diesel.