Removal of Headspace CO₂ Increases Biological Hydrogen Production

Abstract

For biological hydrogen production by fermentation to be a useful method of hydrogen generation, molar yields of hydrogen must be increased. While heat treatment of a soil inoculum increases hydrogen yields by preventing loss of hydrogen to methanogenesis, hydrogen is still lost to acetic acid generation from hydrogen and CO2. To reduce hydrogen losses via acetogenesis, CO2 concentrations in the headspace were substantially reduced during hydrogen production using a chemical scavenger (KOH). CO2 in the headspace was decreased from 24.5% (control) to a maximum of 5.2% during the highest gas production phase, resulting in a hydrogen partial pressure of 87.4%. This reduction in CO2 increased the hydrogen yield by 43% (from 1.4 to 2.0 mol of H2/mol of glucose). The soluble byproducts in all tests consisted primarily of acetate and ethanol. Higher concentrations of ethanol (10.9 mM) remained in solution from bottles with CO2 removal than in the control (1.2 mM), likely as a result of hydrogen inhibition of biological ethanol conversion to acetic acid. These results show that hydrogen production can be increased by removing CO2 in the reactor vessel, likely as a result of suppression of acetogenesis.

Evaluation of Stability Factors in the Anaerobic Treatment of Slaughterhouse Wastewater

“…The samples were prepared and conserved based on the methodology proposed by Park et al [14]. The chemical analysis was carried out in a GC-FID by Agilent Technologies, Model G1530A with a capillary column DB-FAB (0.25mm x 30m) by the same company, using helium as the carrier gas.…”

Integrating dark and light bio-hydrogen production strategies: towards the hydrogen economy

“…the standard electrode potentials of the NAD and ferredoxin half-cells (-320 mV and -400 mV, respectively) are more positive than that of the H + half-cell (-414 mV) (McCormick 1998). A very low H 2 partial pressure (pH 2 ) (theoretically <60 Pa or <0.0006 bar) is required to drive this reaction forwards and H 2 yields exceeding 2 mol H 2 /mol glucose were obtained only under vacuum or with continuous gas purging to strip away H 2 (Park et al 2005). Indeed, a maximum yield of 3.9 mol H 2 /mol glucose was reported using E. cloacae under a vacuum of 330 torr (equivalent to 0.44 bar or 44 kPa) (Mandal et al 2006).…”

Effect of Environmental Parameters on hydrogen Production using Clostridium Saccharoperbutylacetonicum N1-4(ATCC 13564)

“…However, most hydrogen is usually produced from stored methane reserves and other nonrenewable materials, resulting in net increases of CO 2 in the environment. Shifting a fossil fuel economy to a hydrogen economy offers few environmental advantages if both are based on the net consumption of fossil fuels [1] . Thus, it is essential for reducing CO 2 emissions that hydrogen production not release a net amount of CO 2 into the atmosphere and that the technologies and materials used to produce hydrogen are sustainable.…”

“…The production of hydrogen using mixed anaerobic bacterial cultures has attracted substantial interest recently due to its high conversion and non-polluting nature features as an ideal, clean and sustainable energy in contrast to chemical processes [1][2][3][4] . The concept comprises hydrogen production from non-renewable and renewable energy sources, hydrogen transportation and storage, hydrogen utilization and hydrogen safety issues [5] .…”

“…Anaerobic fermentation is a promising method of sustainable hydrogen production since organic matter, including waste products, can be used as a feedstock for the process. The highest yields of hydrogen have been reported with strains of clostridia in pure cultures or mixed cultures where clostridia are predominant [1] . Therefore, Biological processes evolving hydrogen gas are categorized as a renewable energy source.…”