Steven Wenetta Van Ginkel (swv102@email.psu.edu)

Department of Civil and Environmental Engineering

Pennsylvania State University

University Park, PA 16802

This study consisted of two experimental phases. In the first phase, four different bacterial seed sources were collected from nature to determine if hydrogen production could be achieved using mixed cultures of bacteria. These sources were agricultural soil where both potatoes and soybeans were grown in as well as two different kinds of compost, designated compost one and compost two. The seed sources were baked for two hours to inhibit hydrogen-consuming bacteria. The study used 250 mL anaerobic batch serum bottle cultures in a mesophilic condition in which 30 grams of the baked seed source was placed. A fractional factorial experimental design was used to explain the combined effect of sucrose concentration and pH on hydrogen production potential and rate. In the design, the sucrose concentration varied from 2 to 6 grams per bottle (15 to 45 g COD / L) while the pH varied from 4.5 to 6.5. Nine combinations of pH and sucrose concentration were used in the design. They were filled to the 150 mL level with seed source, sucrose, and nutrients allowing a 100 mL headspace. The average conversion efficiencies based on H₂–COD to sucrose–COD for potato, soybean, compost one, and compost two seed sources were 9%, 8%, 12%, and 10%, respectively. The highest hydrogen concentration in the biogas was 82% with an average of 55%. The highest values of hydrogen conversion rate using potato soil, soybean soil, compost one, and compost two as the seed sources were 12, 15, 18, and 19 mL / (g COD*L), respectively, while the highest hydrogen production rates were 572, 290, 672, and 592 mL / (L reactor volume*day), respectively. The average values of hydrogen conversion rate using potato soil, soybean soil, compost one, and compost two as the seed sources were 7, 9, 14, and 11 mL/ (g COD*L), respectively. The average hydrogen production rates were 512, 247, 568, and 514 mL / (L reactor volume*day), respectively. Overall, using potato soil as the seed source produced the highest average rate, while using compost one as the seed source produced the highest average potential. In conclusion, this research demonstrated that hydrogen could be produced using mixed bacterial cultures obtained from nature. The optimum pH and sucrose concentration combination was not conclusively determined in these experiments because the medium was not buffered with respect to pH and the pH became inhibitory at an unknown time. The pH would have to be maintained for more accurate results.

In the second phase, three buffered anaerobic batch experiments were conducted using 30 grams of heat-treated compost as the seed source to produce hydrogen gas. After heat treatment, the compost was passed through a 1.19 mm diameter sieve. The experiments used a fractional factorial design with the aim of discovering a pH and a sucrose concentration to optimize hydrogen production potential and hydrogen production rate. The experiments were buffered by using a 0.066 M KH₂PO₄ solution while the pH was adjusted to its final value using 0.94 M Na₂CO₃ and 1 M HCl. In the experiments, the pH ranged from 4.5 to 7.5. Three ranges of sucrose concentration were used. In the high range, the sucrose concentration ranged from 1.5 to 7.5 g COD/L. In the medium range, the sucrose concentration ranged from 1 to 4 g COD/L. In the low range, the sucrose concentration ranged from 0.5 to 1.5 g COD/L. The high sucrose concentration range produced the most amount of hydrogen (39 mL/g COD*L) and had the highest hydrogen conversion rate (1780 mL / L reactor volume*day). The highest conversion efficiency based on H₂ –COD to sucrose–COD was 21% at the high sucrose concentration range.