Inhibiting rumen methanogenesis often causes hydrogen accumulation, potentially negatively affecting the rumen fermentation process. We hypothesized that the use of hydrogen acceptors when methanogenesis is inhibited would reduce hydrogen accumulation and improve production of useful fermentation end-products. In this study, phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, and gallic acid were examined as hydrogen acceptors by in vitro batch culture. Three experiments were performed: in experiment 1 (Exp.1), 0, 2, 4, and 6 mM of each phenolic compounds were examined to find their optimum concentration; in experiment 2 (Exp.2), each phenolic compound at its optimum concentration obtained from Exp.1 was combined with 2-bromoethanesulfonate (BES) at 3 μM as a methanogenesis inhibitor; in experiment 3 (Exp.3), the long-term effects of phloroglucinol (36mM) with or without BES (3 μM) were examined by sequential incubation. The use of 6 mM phenolic compounds in Exp.1 did not negatively affect volatile fatty acid (VFA) production, ammonia production, and total gas production. Hence, 6 mM of each phenolic compound was used in Exp.2. In Exp.2, phloroglucinol, gallic acid, and pyrogallol combined with BES significantly increased acetate production by 47%, 39%, and 36%, respectively. Whereas methane production was reduced by 75%, none of the phenolic compounds decreased hydrogen accumulation in the early stages of fermentation. In Exp.3, after three sequential incubations, phloroglucinol combined with BES decreased hydrogen accumulation by 72% and further inhibited methanogenesis as compared to BES alone. Interestingly, phloroglucinol alone significantly decreased methane production by 99% with just a numerical increase in hydrogen accumulation compared to control. Also, phloroglucinol with or without BES increased total VFA, acetate, and total gas productions and decreased ammonia production. Our results confirmed the potential of phloroglucinol to capture excess hydrogen and redirect it towards VFA production. These findings will further be evaluated in vivo.