Dark hydrogen fermentations

The production of hydrogen is a ubiquitous, natural phenomenon under anoxic or anaerobic conditions. A wide variety of bacteria, in swamps, sewage, hot springs, the rumen of cattle etc. is able to convert organic matter to hydrogen, CO2 and metabolites like acetic acid, lactate, ethanol and alanine. In general, these bacteria live in the close vicinity of other bacteria which consume these metabolites, including hydrogen, producing their own endproducts like methane and CO2. In this way, a stable ecosystem is formed where potential feedback inhibition of the hydrogen producers by hydrogen, is annulled by the action of the hydrogen consumers. In view of the design of a bioprocess for the production of hydrogen from biomass, extreme thermophilic anaerobic bacteria have been selected because of their high yield with respect to hydrogen production. The yield is reported to be approximately 83-100¿f the maximal theoretical value of 4 mol hydrogen/mol glucose, in contrast to the strict anaerobic Clostridia which produce hydrogen with an approximate yield of 2 mol/mol and the facultative anaerobes which show a H2 yield of less than 2. Besides optimal H2 molar yields, high hydrogen production rates are needed. Product formation appeared to be dependent on cell densities. Thermophiles usually grow to low densities and, therefore production rates are expected to be low. High production rates are reported for Clostridia and Enterobacter of maximal 23 and 58 mmol/L.h, respectively. Hydrogen fermentations by co- and mixed cultures showed production rates of approximately 30-50 mmol/L.h

Study of the doubly charmed tetraquark T+cc

Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T+cc tetraquark with a quark content of ccu⎯⎯⎯d⎯⎯⎯ and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector T+cc state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T+cc state. In addition, an unexpected dependence of the production rate on track multiplicity is observed

Hydrogen from biomass

Hydrogen is generally regarded as the energy carrier of the future. The development of a process for hydrogen production from biomass complies with the policy of the Dutch government to obtain more renewable energy from biomass. This report describes the progress of the BWP II project, phase 2 of the Biological Hydrogen Production programme

Autorijden op waterstof uit aardappelschillen praktijkrijp

Als het aan wetenschappers uit Wageningen ligt, rijdt over een kleine tien jaar een deel van onze voertuigen op uit de aardappelschil gewonnen waterstof. Dr. Pieternel Claassen en dr. Truus de Vrije hebben daarvoor nu al een praktijkrijp productieproces ontwikkeld. Zij zetten daarmee aardappelstoomschillen, afkomstig van onze verwerkende industrie, om in zuivere waterstof en methaan. Nu is het nog wachten op voldoende waterstofmotore

Effect of pretreatment severity on the conversion of barley straw to fermentable substrates and the release of inhibitory compounds

The production of fermentable substrates from barley straw under various process conditions was studied. Pretreatment included chemical pretreatment with dilute-acid followed by enzymatic hydrolysis; the pretreatment conditions were expressed in a combined severity factor, CS, which ranged in the present study from -1.6 to 1.1. Considering the production of fermentable sugars and the release of inhibitory compounds, the optimal pretreatment conditions were 170 °C, 0% sulfuric acid and 60 min, corresponding to CS -0.4. Under these conditions, 21.4 g glucose/L, 8.5 g xylose/L, and 0.5 g arabinose/L were produced, while 0.1 g HMF/L, 0.4 g furfural/L, 0.0 g levulinic acid/L, 0.0 g formic acid/L, and 2.1 g acetic acid/L were released. The ratio of Ssugars/Sinhibitors proved to be a good tool for evaluating the suitability of a hydrolysate for fermentation purposes

Development of a fermentation-based process for biomass conversion to hydrogen gas

The production of hydrogen gas from biomass to meet the foreseen demand arising from the expected introduction of fuel cells is envisaged. Apart from the well-known gasification method, fermentative conversion can also be applied for this purpose. Two options of the latter method, that is, thermophilic fermentation and photofermentation can be combined in a two-stage process in which about 70% of hydrogen present in biomass is converted to gaseous form. It is expected that this process can be applied in decentralized, small-scale production units. The main stages of the fermentative hydrogen production process are the following: - biomass pretreatment to give fermentable feedstock and non-fermentables, - thermophilic fermentation in which fermentable feedstock is converted to hydrogen gas and organic acids, - photofermentation in which the organic acids are converted to hydrogen gas, - upgrading of hydrogen gas to meet product specification, - separation and treatment of non-fermentables. In order to develop a sustainable hydrogen production route based on fermentation, it is necessary to improve the existing knowledge of these process stages and to carry out process optimization studies. As a major step in this direction, the European research project HYVOLUTION has been organized under the 6(th) Framework Programme of the EU