The effect of enzyme additives on the anaerobic digestion of energy crops

The mechanisms governing the efficiency of commercial fiber-degrading enzyme additives at improving the anaerobic digestion of energy crops were investigated. Standard batch digestion trials (BMP-assays) were performed using the Hohenheim Biogas Test (HBT) on maize straw, maize corn, and rye silage with different inocula. These BMP-assays showed no significant effect of enzyme additives (including commercial cellulase, xylanase, pectinase, laccase) on the methane production rate. However, batch digestion trials performed on grass silage under suboptimal conditions with inoculum of weak bacterial activity revealed significant increases of methane production up to 40%. In another experiment semi continuous acidogenic fermentation was performed in laboratory digesters with maize silage and water added for dilution at OLR 4 kg VS/(m3 × d), HRT 5 days, with the medium kept in the pH range 5 5.5 through quicklime addition. Enzyme additives at a dosage of 10 g/kg substrate VS significantly increased VFA release (+10%) as well as gas production, including H2 production (+20%). The results show that the efficiency of enzyme additives in anaerobic digestion depends on substrate (fibre length and composition) and process parameters (retention time, loading rate, pH, efficiency of bacterial substrate degradation).In der Promotionsarbeit wurde die Wirkungsweise von Enzymzusätzen auf die anaerobe Vergärung von Energiepflanzen systematisch untersucht. Standard-Batchgärversuche mit Energiepflanzen mit dem Hohenheimer Biogasertragstest (HBT) unter Anwendung verschiedener Inokula zeigten keine signifikante Wirkung der Enzymzusätze (handelsübliche Zellulase, Xylanase, Pektinase und Laccase) auf die Methanbildung. Hingegen zeigten Batchgärversuche mit Grassilage, die unter suboptimalen Bedingungen mit einem mikrobiologisch wenig aktiven Inokulum durchgeführt wurden, signifikante Steigerungen der Methanbildung bis zu 40%. In einem weiteren Versuchsansatz wurde die acidogene Vergärung von Maissilage semi-kontinuierlich unter Zugabe von Wasser und Branntkalk bei einer Raumbelastung von 4 kg oTS/(m3 × d), einer hydraulischen Verweilzeit von 5 Tagen und einem pH-Wert von 5-5,5 durchgeführt. Dabei brachten Enzymzusätze mit einer Dosierung von 10 g/kg oTS eine signifikante Erhöhung der Fettsäureproduktion (+10%), sowie der Gas- und Wasserstoffproduktion (+20%). Die Ergebnisse deuten darauf hin, dass die Wirksamkeit von Enzymzusätzen in der anaeroben Vergärung von Substrateigenschaften (Faserlänge und chemische Zusammensetzung) und Verfahrensparametern (Verweilzeit, Raumbelastung, pH-Wert, Effizienz des bakteriellen Substratabbaus) abhängt

Batch anaerobic digestion of banana waste - energy potential and modelling of methane production kinetics

Different fractions of banana (stalk, peel, and flesh) as well as the whole unpeeled banana were studied in a laboratory Biochemical Methane Potential (BMP) assay. After completion of 35-day digestion at 37°C in 2L-reactors, specific methane yields reached 0.256, 0.322, 0.367 and 0.349 m³/kg VS (volatile solids) for stalk, peel, flesh, and unpeeled banana respectively. Considering the country of Uganda, East Africa, the collection of peels and stalks from banana production would yield a theoretical potential of about 60 GWh of electrical energy per year in biogas plants. In order to verify the suitability of banana fractions to the biogas process, their chemical composition was analyzed, and their methane production kinetics was estimated with exponential and logistic models. Banana peel was found to be easily degradable, and well suited for biogas production. Banana flesh had the fastest degradation rate of all banana fractions, and banana stalk had the slowest degradation rate, respectively. Methane production kinetics was fitted with first order and logistic models. The kinetics of methane production from banana flesh correlated well with a logistic model, but did not with exponential models. Alternately, methane production kinetics from banana stalk correlated well with exponential models, but did not with the logistic model. Methane production kinetics from banana peel did not correlate well with any model. Hence, the biochemistry of anaerobic processes may follow different patterns depending on substrate degradability, explaining the difficulty of finding a universal explanatory model of methane production kinetics in batch mode

Zinc and cobalt complexes based on tripodal ligands: synthesis, structure and reactivity toward lactide.

International audienceThe coordination chemistry of a series of pro-ligands ([L¹]-[L⁶]) with cobalt and zinc derivatives has been studied. All complexes have been characterized by multinuclear NMR, elemental analysis, and by single-crystal X-ray diffraction studies. Polymerization of rac-lactide takes place at 130 °C in the presence of cobalt and zinc complexes to yield polymers under solvent free conditions with controlled molecular masses and narrow polydispersities

Preliminary Results of Innovative Two-Stage Torrefaction Technology Applied for Thermochemical Treatment of Sunflower Husk

This article proposes an innovative two-stage technology for biomass torrefaction generating high-quality biochar, more specifically biocoal, as solid fuel, and offering a promising solution to the challenges posed by the combustion of biomass. In particular, the higher quality of biochar as solid fuel reduces the build-up of unmanageable deposits on fired surfaces, as these deposits inhibit heat transfer and reduce the efficiency of biomass boilers. The proposed two-stage technology involves torrefaction in a hearth-type reactor at temperatures up to 250 °C, followed by a subsequent stage of cooling achieved through washing with water. The two-stage torrefaction technology is integrated within a vertical hearth reactor vessel composed of three superimposed trays serving for biomass input, torrefaction, and water washing combined with biomass cooling, respectively. Upon contact with torrefied biomass, cooling water turned into water vapor; hence, eliminating the requirement for subsequent biomass separation and drying. The system was tested on sunflower husk, and results showed a reduction in the content of problematic elements such as alkali metal chlorides or sulfur compounds in biochar ash, suggesting lower corrosion rates of convective heating surfaces of the boiler under ash sediments. It is hypothesized that, while water exited hot biomass in the form of water vapor instead of liquid water, as is typically the case in water-washing processes, a share of undesirable elements may still have been removed from biomass through vaporization, without necessitating any additional process for ash removal. Hence, the index values calculated according to the chemical analysis of biomass ash suggested that sunflower husk biochar (biocoal) resulting from the proposed two-stage torrefaction process may display fuel characteristics similar to biomasses whose combustion ash may form reduced levels of deposits on boiler surfaces. Therefore, the proposed technology holds the potential to improve solid fuel characteristics of biomass, targeting enhanced efficiency and sustainability of biomass-fired power plants

Pushing Raman spectroscopy over the edge: purported signatures of organic molecules in fossil animals are instrumental artefacts

International audienceWidespread preservation of fossilized biomolecules in many fossil animals has recently been reported in six studies, based on Raman microspectroscopy. Here, we show that the putative Raman signatures of organic compounds in these fossils are actually instrumental artefacts resulting from intense background luminescence. Raman spectroscopy is based on the detection of photons scattered inelastically by matter upon its interaction with a laser beam. For many natural materials, this interaction also generates a luminescence signal that is often orders of magnitude more intense than the light produced by Raman scattering. Such luminescence, coupled with the transmission properties of the spectrometer, induced quasi-periodic ripples in the measured spectra that have been incorrectly interpreted as Raman signatures of organic molecules. Although several analytical strategies have been developed to overcome this common issue, Raman microspectroscopy as used in the studies questioned here cannot be used to identify fossil biomolecules

Pushing Raman spectroscopy over the edge: purported signatures of organic molecules in fossil animals are instrumental artefacts

International audienceWidespread preservation of fossilized biomolecules in many fossil animals has recently been reported in six studies, based on Raman microspectroscopy. Here, we show that the putative Raman signatures of organic compounds in these fossils are actually instrumental artefacts resulting from intense background luminescence. Raman spectroscopy is based on the detection of photons scattered inelastically by matter upon its interaction with a laser beam. For many natural materials, this interaction also generates a luminescence signal that is often orders of magnitude more intense than the light produced by Raman scattering. Such luminescence, coupled with the transmission properties of the spectrometer, induced quasi-periodic ripples in the measured spectra that have been incorrectly interpreted as Raman signatures of organic molecules. Although several analytical strategies have been developed to overcome this common issue, Raman microspectroscopy as used in the studies questioned here cannot be used to identify fossil biomolecules

Bibliometric analysis of the evolution of biochar research trends and scientific production

International audienceBiochar has caught great attention over the last decade, yielding a large number of publications in a broad range of disciplines. This scientometric study produces a combined qualitative–quantitative assessment of 10,000 publications recorded in the period 2005–2019 in the Web of Science (WoS) database, based on innovative methods and indicators, and focusing in particular on biochar production and valorization pathways. The cumulated number of publications was analyzed with power and logistic models, and the economic indicator CAGR (Compound Annual Growth Rate) for the estimation of future academic output. Mapping of the evolution of academic output revealed the worldwide diffusion of academic production toward many countries and continents. According to the analysis of collaboration networks of most productive countries, the development of academic output may be linked to high levels of international collaboration, as well as the diversity of these networks. Furthermore, the rise of academic output in the African continent may preclude an evolution toward a multipolar academic world. The average number of citations per paper at both author level (number of citations/number of papers) and journal level (total citations/total papers) was found to be a useful indicator of scientific productivity. In particular, academic journals with impact factors as low as 2.5–3 still ranked high on this criterion, revealing their high impact on academic research in the biochar sector. Finally, the analysis of targeted keywords co-occurrences emphasized the diversification of research on biochar applications, from its initial use as soil improver toward engineered biochar for versatile applications