Photosynthetic hydrogen production by Chlamydomonas reinhardtii

Hydrogen is a leading alternative fuel being explored for future use. Making the switch from gasoline and natural gases to hydrogen will allow the United States to decrease its dependency on foreign oil and decrease the negative impacts on the environment. While several methods exist for hydrogen generation, each method has limitations. Algal hydrogen production is a relatively new method that has several advantages. Research is currently being performed to optimize this process. Most of the research, however, is based in molecular-level microbiology and biotechnology. The objective of this project was to optimize the algal hydrogen production process from an engineering standpoint. Three parameters evaluated in this study included the effects of light wavelength, glucose addition, and constant mixing.; The wavelength experiments examined blue, red, and green light wavelength ranges as well as low intensity and full intensity full spectrum lights. These conditions were created through the use of light filters. It was hypothesized and observed that green wavelengths of light produce the largest amount of hydrogen gas. Hydrogen levels reached 54.81 (+/- 9.07) mg/L hydrogen (2.26x10-5 (+/- 6.60x10-6 ) mg/L/cell) under green light, compared to the control (full intensity full spectrum light) at 32.60 (+/- 5.90) mg/L hydrogen (1.30x10 -5 (+/- 5.24x10-7) mg/L/cell). It was also observed that more hydrogen is produced at the lower light intensity.; The glucose addition experiments examined the effect of three glucose concentrations (10, 50, and 100 mg/L) on hydrogen production. All batch reactors were under full intensity full spectrum light. It was hypothesized that glucose will increase hydrogen production. While the 10 and 50 mg/L concentrations did not show much change from the controls, 100 mg/L of glucose greatly increased the total amount of hydrogen produced. Overall hydrogen levels reached 475.84 (+/- 35.30) mg/L hydrogen with 100 mg/L glucose, compared to the control at 159.18 (+/- 3.99) mg/L hydrogen. The glucose was used to produce ATP for cell growth. Increased cell growth was observed proportionally in all concentration levels. Despite the drastic increase in hydrogen gas, it was determined that this is due to increased cell count from cell growth. Per cell hydrogen levels reached 1.70x10-4 (+/- 1.14x10-5) mg/L/cell hydrogen with 100 mg/L glucose, compared to the control at 3.92x10-4 (+/- 5.53x10 -6) mg/L/cell hydrogen.; The constant mixing experiments compared constantly mixed and nonconstantly mixed batch reactors. All batch reactors were under full intensity full spectrum light. It was hypothesized that constant mixing would increase hydrogen production. However, it was observed that constant mixing did not significantly increase hydrogen production. Hydrogen levels reached 170.48 (+/- 4.15) mg/L hydrogen (3.96x10-4 (+/- 1.32x10-5 )) mg/L/cell) with constant mixing, compared to the control at 159.18 (+/- 3.99) mg/L hydrogen (3.92x10-4 (+/- 5.53x10-6) mg/L/cell).; While this research provided insight into the optimization of algal hydrogen production, more research is needed to address additional questions. Some parameters that should be explored are optimal green light intensity, effect of mixing in larger reactors, effects of other nutrients, and combined effects of the optimization parameters tested.