Achieving high hydrogen productivities of 20 L/L-day via microbial electrolysis of corn stover fermentation products

Microbial electrolysis cells have the potential to generate renewable hydrogen from underutilized waste streams, however current devices have not reached very large productivity targets using real waste products at any scale. This study used a waste from fermented corn stover known as corn stover fermentation product to reach performance metrics that could be commercialized, if adequately scaled. Average current densities in MECs with mature biofilms reached 17.9 ± 1.6 A/m2 at an organic loading rate of 30 grams of chemical oxygen demand per liter of anode volume per day (g/L-day), reaching a maximum current density of 27.2 ± 2.9 A/m2. Hydrogen productivities reached 20.2 ± 2.0 L of H2 per L anode volume per day (L/L-day). These represent the highest current densities and highest hydrogen productivities using a complex feedstock in a microbial electrolysis cell. Organic acids and sugars present in untreated substrate were converted at high percentages in MECs, with most above 90% conversion, at organic loading rates of 10, 20, and 30 g/L-day. The effect of periodic high liquid flow rates through the anode on performance was assessed. These tests, called pulsing, showed that hydrogen productivities and current densities increased most dramatically as flow was pulsed every hour at a baseline flow rate of 0.3 mL/min. These productivities show promise for high performance systems, if adequate scale up can be achieved.