Lessons Learned from an Experimental Campaign on Promoting Energy Content of Renewable Biogas by Injecting H 2 during Anaerobic Digestion

Direct injection of H 2 to an anaerobic reactor enables biological fixation of CO 2 into CH 4 (biomethanation) and consequently boosts methane content in the produced biogas. However, there has been only a small amount of literature reporting results on this technique in a continuous reactor framework to date. To fill this gap, the present study devoted an experimental work to direct H 2 addition to a fed-batch semi-continuous reactor, where the injected H 2 concentration increased gradually (~3–30 mmol), spanning a moderate operational period of about 70 days. As the results revealed, the reactor continued anaerobic operation for each level of H 2 dosing and produced an average methane content in the biogas ranging between 65% and 72%. The exhibited biogas upgrading trend appeared to be under-developed, and thereby suggests the need for further research.