Influence of distiller's grains and condensed tannins in the diet of feedlot cattle on biohydrogen production from cattle manure

Biohydrogen production from the manure of cattle fed diets containing corn dried distiller's grains with solubles (DDGS) diets was assessed. Four types of manure were obtained from cattle fed four diets (DDG, %of dietary dry matter): 0 (CK), 20 (DG20), 40 (DG40) and 40 plus 2.5% of dietary dry matter as condensed tannins (DG40CT) and evaluated for biohydrogen production using dark fermentation. Each treatment was evaluated in quadruplicate using 2 L continuously stirred biodigesters operating at 55 °C in batch culture with an organic loading rate of 20 g L−1 volatile solids and a total operation time of 4 d. Gas samples were taken daily to determine hydrogen production, and slurry samples were analyzed daily for volatile fatty acid concentration, total ammonia nitrogen, volatile solids degradation, and soluble ion concentration. The DG0 and DG40 treatments demonstrated the greatest hydrogen production, with DG40CT producing the least (P < 0.001). The inclusion of tannins in the diet of cattle had a negative effect on biohydrogen production from cattle manure, and thus the economic feasibility of using manure as a substrate in anaerobic digestion could be negatively impacted by the inclusion of tannins in the diet.