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Estimating a conversion factor for the gears used in the industry survey
Hal, R. van; Reijden, K.J. van der - \ 2016
IJmuiden : IMARES (Report / IMARES C004/16) - 35 p.
dover soles - plaice - fishing vessels - fishing gear - conversion - surveys - fish stocks - fishery management - fishery resources - north sea - tong (vis) - schol - vissersschepen - vistuig - conversie - karteringen - visstand - visserijbeheer - visbestand - noordzee
Lignin solubilisation and gentle fractionation in liquid ammonia
Strassberger, Z. ; Prinsen, P. ; Klis, F. van der; Es, D.S. van; Tanase, S. ; Rothenberg, G. - \ 2015
Green Chemistry 17 (2015). - ISSN 1463-9262 - p. 325 - 334.
technical lignins - renewable chemicals - catalysts - extraction - conversion - fuels - kraft - wood - purification - valorization
We present a simple method for solubilising lignin using liquid ammonia. Unlike water, which requires harsh conditions, ammonia can solubilise technical lignins, in particular kraft lignin. A commercial pine wood Kraft lignin (Indulin AT) was solubilized instantaneously at room temperature and 7–11 bars autogeneous pressure, while a commercial mixed wheat straw/Sarkanda grass soda lignin (Protobind™ 1000) was solubilized within 3 h at ambient temperature, and 30 min at. 85 °C. Hydroxide salts were not required. Wheat straw, poplar and spruce organosolv lignins, as well as elephant grass native lignin (MWL) were also solubilized, albeit at lower values. Different sequences of solubilisation and extraction were tested on the Protobind™ 1000 lignin. The remaining lignin residues were characterized by FTIR, size exclusion chromatography (SEC), elemental analysis (ICP), 2D-NMR and 31P NMR. Liquid ammonia is not an innocent solvent, as some nitrogen was incorporated in the residual lignin which then rearranged to higher molecular weight fractions. Nevertheless, the mild solubilisation conditions make liquid ammonia an attractive candidate as a solvent for lignin in future biorefinery processes.
Lignin pyrolysis for profitable lignocellulosic biorefineries
Wild, P.J. de; Gosselink, R.J.A. ; Huijgen, W.J.J. - \ 2014
Biofuels Bioproducts and Biorefining 8 (2014)5. - ISSN 1932-104X - p. 645 - 657.
wheat-straw - organosolv lignin - biomass - phenols - separation - valorization - pretreatment - hydrolysis - conversion - chemicals
Bio-based industries (pulp and paper and biorefineries) produce > 50 Mt/yr of lignin that results from fractionation of lignocellulosic biomass. Lignin is world's second biopolymer and a major potential source for production of performance materials and aromatic chemicals. Lignin valorization is a key-issue for enhanced profitability of sustainable bio-based industries. Despite a myriad of potential applications for lignin and decades of research, its heterogeneity and recalcitrance still preclude commercial value-added applications. Most lignin is utilized for heat and power. Unconventional solutions are needed to better exploit lignin's potential. Organosolv lignins are especially suitable as feedstock for high-value chemicals. At ECN, a lignin biorefinery approach (LIBRA) has been developed, involving a dedicated lignin pyrolysis protocol that is robust, continuous, and capable of processing different lignins. Typical product yields are 20% gas, 35% char, and 45% oil. The oil contains approximately 45% oligomeric phenolic substances, 23% monomeric phenols, and 33% water. The future perspective is scale-up of the process to produce larger lignin pyrolysis oil samples for separation, purification, and industrial application tests. Presently, small lignin pyrolysis oil samples are investigated as feedstock for extracting high-value chemicals, as a substitute for phenol in several applications, and as a feedstock for hydrotreating. The biochar is tested as growth enhancer and as substitute for carbon-black in rubber. Regarding the large lignin side streams from (future) bio-based industries, the LIBRA pyrolysis technology has ample potential to increase the profitability of lignocellulosic biorefineries provided that for both the liquid product and the solid char value-added applications are developed.
Birth, death, and diversification of mobile promoters in prokaryotes
Passel, M.W.J. van; Nijveen, H. ; Wahl, L.M. - \ 2014
Genetics 197 (2014)1. - ISSN 0016-6731 - p. 291 - 299.
branching-process model - transposable elements - population-genetics - sequence evolution - escherichia-coli - dna - genomes - innovation - conversion - selection
A previous study of prokaryotic genomes identified large reservoirs of putative mobile promoters (PMPs), that is, homologous promoter sequences associated with nonhomologous coding sequences. Here we extend this data set to identify the full complement of mobile promoters in sequenced prokaryotic genomes. The expanded search identifies nearly 40,000 PMP sequences, 90% of which occur in noncoding regions of the genome. To gain further insight from this data set, we develop a birth–death–diversification model for mobile genetic elements subject to sequence diversification; applying the model to PMPs we are able to quantify the relative importance of duplication, loss, horizontal gene transfer (HGT), and diversification to the maintenance of the PMP reservoir. The model predicts low rates of HGT relative to the duplication and loss of PMP copies, rapid dynamics of PMP families, and a pool of PMPs that exist as a single copy in a genome at any given time, despite their mobility. We report evidence of these “singletons” at high frequencies in prokaryotic genomes. We also demonstrate that including selection, either for or against PMPs, was not necessary to describe the observed data.
Synthesis of bio-based methacrylic acid by decarboxylation of itaconic acid and citric acid catalyzed by solid transition-metal catalysts
Notre, J.E.L. le; Witte-van Dijk, S.C.M. ; Haveren, J. van; Scott, E.L. ; Sanders, J.P.M. - \ 2014
ChemSusChem 7 (2014)9. - ISSN 1864-5631 - p. 2712 - 2720.
renewable resources - supercritical water - reaction pathways - fatty-acids - chemicals - biomass - decarbonylation - deoxygenation - conversion - plastics
Methacrylic acid, an important monomer for the plastics industry, was obtained in high selectivity (up to 84%) by the decarboxylation of itaconic acid using heterogeneous catalysts based on Pd, Pt and Ru. The reaction takes place in water at 200–2508C without any external added pressure, conditions significantly milder than those described previously for the same conversion with better yield and selectivity. A comprehensive study of the reaction parameters has been performed, and the isolation of methacrylic acid was achieved in 50% yield. The decarboxylation procedure is also applicable to citric acid, a more widely available bio-based feedstock, and leads to the production of methacrylic acid in one pot in 41% selectivity. Aconitic acid, the intermediate compound in the pathway from citric acid to itaconic acid was also used successfully as a substrate.
Specific conversion of amino acids as a means for their separation
Teng, Y. - \ 2014
University. Promotor(en): Johan Sanders, co-promotor(en): Elinor Scott. - Wageningen : Wageningen University - ISBN 9789462570658 - 205
aminozuren - scheiding - elektrodialyse - conversie - chemicaliën uit biologische grondstoffen - onderzoek - biobased economy - amino acids - separation - electrodialysis - conversion - biobased chemicals - research
Aminozuren (AZ) zijn interessante uitgangspunten voor stikstofhoudende (amine) chemicaliën. Zij kunnen gewonnen worden als mengsel uit de hydrolyse van potentieel goedkope eiwitten verkregen van de bijproducten van de biobrandstofproductie of agrarische en voedselafvalstromen. Echter, AZ verkregen van zulke bronnen bevinden zich in een mengsel. Hierdoor is een scheiding nodig om de individuele AZ te verkrijgen voor vervolgomzettingen en toepassingen. Electrodialyse (ED) is een veelbelovende scheidingsmethode die toegepast kan worden in continue modus en op grote schaal.
Synergistic action of enzyme preparations towards recalcitrant corn silage polysaccharides
Neumüller, K.G. ; Streekstra, H. ; Schols, H.A. ; Gruppen, H. - \ 2014
Biomass and Bioenergy 60 (2014). - ISSN 0961-9534 - p. 88 - 97.
talaromyces-emersonii - wheat-straw - hydrolysis - pretreatment - ethanol - plant - lignocellulose - fermentation - efficiency - conversion
Corn silage, its water unextractable solids (WUS) and enzyme recalcitrant solids (ErCS) and an industrial corn silage-based anaerobic fermentation residue (AFR) represent corn substrates with different levels of recalcitrance. Compositional analysis reveals different levels of arabinoxylan substitution for WUS, ErCS and AFR, being most pronounced regarding acetic acid, glucuronic acid- and arabinose content. By screening for enzymatic degradation of WUS, ErCS and AFR, enzyme preparations exhibiting high conversion rates were identified. Furthermore significant synergistic effects were detected by blending Aspergillus niger/Talaromyces emersonii culture filtrates with various enzymes. These findings clearly highlight a necessity for a combinatorial use of enzyme preparations towards substrates with high recalcitrance characteristics to reach high degrees of degradation. Enzyme blends were identified, outperforming the individual commercial preparations. These enzyme preparations provide a basis for new, designed enzyme mixtures for corn polysaccharide degradation as a source of necessary, accessory enzyme activities.
Concurrent formation of furan-2,5-and furan-2,4-dicarboxylic acid: unexpected aspects of the Henkel reaction
Thiyagarajan, S. ; Pukin, A. ; Haveren, J. van; Lutz, M. ; Es, D.S. van - \ 2013
RSC Advances : An international journal to further the chemical sciences 3 (2013)36. - ISSN 2046-2069 - p. 15678 - 15686.
chiral building-blocks - renewable resources - crystal-structure - glucose dehydration - terephthalic acid - biomass - conversion - manufacture - chemistry - products
The concurrent formation of furan-2,5- and furan-2,4-dicarboxylic acid under solvent free conditions via a disproportionation reaction is described. By reacting potassium-2-furoate at 260 degrees C in the presence of 22 mol% of (Lewis acidic) catalysts like CdI2 or ZnCl2, potassium-2-furoate is disproportionated to furan and furandicarboxylic acids. Besides furan and furan-2,5-dicarboxylic acid (2,5-FDCA) as the main products, furan-2,4-dicarboxylic acid (2,4-FDCA) is also formed as a by-product. Experimental evidence has been obtained that, under the reaction conditions applied, 2,5-FDCA and 2,4-FDCA are formed by separate reaction pathways. Selectivity towards the different FDCA isomers is affected by the type of catalyst used. Single-crystal X-ray analysis shows that 2,4-FDCA has a more 'linear' character compared to 2,5-FDCA and hence is structurally more comparable to terephthalic acid (TA), making it an interesting monomer for synthetic polyesters.
Carbon Nanofiber Supported Transition-Metal Carbide Catalysts for the Hydrodeoxygenation of Guaiacol
Jongerius, A. ; Gosselink, R.W. ; Dijkstra, J. ; Bitter, J.H. ; Bruijnincx, P.C.A. ; Weckhuysen, B.M. - \ 2013
ChemCatChem 5 (2013)10. - ISSN 1867-3880 - p. 2964 - 2972.
molybdenum nitride catalysts - lignin model compounds - reaction network - aromatic chemicals - organosolv lignin - vegetable-oils - fast pyrolysis - depolymerization - conversion - hydrogenolysis
Hydrodeoxygenation (HDO) studies over carbon nanofiber-supported (CNF) W2C and Mo2C catalysts were performed on guaiacol, a prototypical substrate to evaluate the potential of a catalyst for valorization of depolymerized lignin streams. Typical reactions were executed at 55 bar hydrogen pressure over a temperature range of 300–375¿°C for 4 h in dodecane, using a batch autoclave system. Combined selectivities of up to 87 and 69¿% to phenol and methylated phenolics were obtained at 375¿°C for W2C/CNF and Mo2C/CNF at >99¿% conversion, respectively. The molybdenum carbide-based catalyst showed a higher activity than W2C/CNF and yielded more completely deoxygenated aromatic products, such as benzene and toluene. Catalyst recycling experiments, performed with and without regeneration of the carbide phase, showed that the Mo2C/CNF catalyst was stable during reusability experiments. The most promising results were obtained with the Mo2C/CNF catalyst, as it showed a much higher activity and higher selectivity to phenolics compared to W2C/CNF.
Integration of first and second generation biofuels: Fermentative hydrogen production from wheat grain and straw
Panagiotopoulos, I.A. ; Bakker, R.R.C. ; Vrije, G.J. de; Claassen, P.A.M. ; Koukios, E.G. - \ 2013
Bioresource Technology 128 (2013). - ISSN 0960-8524 - p. 345 - 350.
thermophiles caldicellulosiruptor-saccharolyticus - dilute-acid pretreatment - thermotoga-neapolitana - extreme thermophiles - bioethanol production - biomass - inhibition - conversion - ethanol - pulp
Integrating of lignocellulose-based and starch-rich biomass-based hydrogen production was investigated by mixing wheat straw hydrolysate with a wheat grain hydrolysate for improved fermentation. Enzymatic pretreatment and hydrolysis of wheat grains led to a hydrolysate with a sugar concentration of 93.4 g/L, while dilute-acid pretreatment and enzymatic hydrolysis of wheat straw led to a hydrolysate with sugar concentration 23.0 g/L. Wheat grain hydrolysate was not suitable for hydrogen production by the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus at glucose concentrations of 10 g/L or higher, and wheat straw hydrolysate showed good fermentability at total sugar concentrations of up to 10 g/L. The mixed hydrolysates showed good fermentability at the highest tested sugar concentration of 20 g/L, with a hydrogen production of 82–97% of that of the control with pure sugars. Mixing wheat grain hydrolysate with wheat straw hydrolysate would be beneficial for fermentative hydrogen production in a biorefinery.
Exploring different forest definitions and their impact on developing REDD+ reference emission levels: A case study for Indonesia
Romijn, J.E. ; Ainembabazi, J.H. ; Wijaya, A. ; Herold, M. ; Angelsen, A. ; Verchot, L. ; Murdiyarso, D. - \ 2013
Environmental Science & Policy 33 (2013). - ISSN 1462-9011 - p. 246 - 259.
greenhouse-gas emissions - tropical forests - carbon emissions - oil palm - deforestation - degradation - land - opportunities - conversion - cover
Developing countries participating in the mitigation mechanism of reducing emissions from deforestation and forest degradation and the role of conservation, sustainable management of forests and enhancement of forest carbon stocks (REDD+), need to determine a national forest reference emission level (REL) as part of their national monitoring system, which serves as a benchmark to measure the impact of their REDD+ actions. Using data from Indonesia, we show that the choice of a forest definition can have a large impact on estimates of deforestation and forest degradation areas, on assessment of drivers of deforestation and on the development of a REL. The total area of deforestation between 2000 and 2009 was 4.9 million ha when using the FAO definition, 18% higher when using a ‘natural forest definition’ and 27% higher when using the national definition. Using the national and natural forest definitions, large areas (>50%) were classified as shrubland after deforestation. We used regression models to predict future deforestation. Deforestation was much better predicted than degradation (R2 of 0.81 vs. 0.52), with the natural forest definition giving the best prediction. Apart from historical deforestation and initial forest cover, gross domestic product and human population were important predictors of future deforestation in Indonesia. Degradation processes were less well modeled and predictions relied on estimates of historical degradation and forest cover.
“In situ” removal of isopropanol, butanol and ethanol from fermentation broth by gas stripping
Vrije, G.J. de; Budde, M.A.W. ; Wal, H. van der; Claassen, P.A.M. ; Lopez Contreras, Ana - \ 2013
Bioresource Technology 137 (2013). - ISSN 0960-8524 - p. 153 - 159.
acetobutylicum atcc 824 - clostridium-acetobutylicum - batch fermentation - product recovery - aqueous-solution - n-butanol - adsorption - acetone - conversion
In this study, the removal of IBE from aqueous solutions by gas stripping has been characterized. The effect of one or more components in the solution on the kinetics of the separation has been studied, both at 37 °C and at 70 °C. Gas stripping has been applied to batch, repeated batch and continuous cultures of Clostridium beijerinckii grown on a glucose/xylose mixed sugar substrate mimicking lignocellulosic hydrolysates, with the aim of finding optimal conditions for a stable IBE-producing culture with high productivity. An innovative repeated-batch process has been demonstrated in which the gas-stripping is performed at 70 °C, resulting in a prolonged stable IBE culture.
Thermal Preference of Juvenile Dover Sole (Solea solea) in Relation to Thermal Acclimation and Optimal Growth Temperature
Schram, E. ; Bierman, S.M. ; Teal, L.R. ; Vis, H. van de; Rijnsdorp, A.D. - \ 2013
PLoS One 8 (2013)4. - ISSN 1932-6203
turbot scophthalmus-maximus - final preferendum - climate-change - fish - senegalensis - ectotherms - physiology - conversion - tolerance - ecology
Dover sole (Solea solea) is an obligate ectotherm with a natural thermal habitat ranging from approximately 5 to 27°C. Thermal optima for growth lie in the range of 20 to 25°C. More precise information on thermal optima for growth is needed for cost-effective Dover sole aquaculture. The main objective of this study was to determine the optimal growth temperature of juvenile Dover sole (Solea solea) and in addition to test the hypothesis that the final preferendum equals the optimal growth temperature. Temperature preference was measured in a circular preference chamber for Dover sole acclimated to 18, 22 and 28°C. Optimal growth temperature was measured by rearing Dover sole at 19, 22, 25 and 28°C. The optimal growth temperature resulting from this growth experiment was 22.7°C for Dover sole with a size between 30 to 50 g. The temperature preferred by juvenile Dover sole increases with acclimation temperature and exceeds the optimal temperature for growth. A final preferendum could not be detected. Although a confounding effect of behavioural fever on temperature preference could not be entirely excluded, thermal preference and thermal optima for physiological processes seem to be unrelated in Dover sole
Structural features and water holding capacities of pressed potato fibre polysaccharides
Ramasamy, U. ; Kabel, M.A. ; Schols, H.A. ; Gruppen, H. - \ 2013
Carbohydrate Polymers 93 (2013)2. - ISSN 0144-8617 - p. 589 - 596.
cell-wall material - sugar-beet pulp - solanum-tuberosum - nonstarch polysaccharides - aspergillus-aculeatus - nmr characterization - purification - xyloglucan - methylation - conversion
Pressed potato fibre (PPF) has a high water holding capacity (WHC) affecting its processing as an animal feed. The aim of this study was to characterize cell wall polysaccharides (CWPs) in PPF and investigate their WHC. This was done via sequential extractions. Half of all CWPs were recovered in the hot buffer soluble solids extract as pectins (uronic acid and rhamnose) and galactans wherein most pectins (76%) from PPF were water soluble. Most likely, the network of CWPs is loosened during processing of potatoes. PPF showed a WHC of 7.4 expressed as the amount of water held per g of dry matter (mL/g). Reconstituting hot buffer soluble solids with buffer insoluble solids in water gave a WHC comparable to that of PPF. Removal of alkali soluble solids, which mainly comprised xyloglucans, lowered the WHC of the final residue. The results indicated that interactions between CWPs could affect the WHC of PPF.
Bioelectrochemical production of caproate and caprylate from acetate by mixed cultures
Eerten-Jansen, M.C.A.A. van; Heijne, A. ter; Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Sleutels, T.H.J.A. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
ACS sustainable chemistry & engineering 1 (2013)5. - ISSN 2168-0485 - p. 513 - 518.
microbial electrolysis cells - fuel-cells - hydrogen - biomass - conversion - ethanol - reduction - transport - membranes - butyrate
The use of mixed cultures to convert waste biomass into medium chain fatty acids, precursors for renewable fuels or chemicals, is a promising route. To convert waste biomass into medium chain fatty acids, an external electron donor in the form of hydrogen or ethanol needs to be added. This study investigated whether the cathode of a bioelectrochemical system can be used as the electron donor for the conversion of acetate into medium chain fatty acids. We show that medium chain fatty acids were produced in a bioelectrochemical system at -0.9 V vs. NHE cathode potential, without addition of an external mediator. Caproate, butyrate and smaller fractions of caprylate were the main products formed from acetate. In-situ produced hydrogen was likely involved as an electron donor for the reduction of acetate. Electron and carbon balances revealed that 45% of the electrons in electric current and acetate, and 31% of the carbon from acetate were recovered in the formed products. This study showed for the first time production of medium chain fatty acids caproate and caprylate from acetate at the cathode of bioelectrochemical systems, and offers new opportunities for application of bioelectrochemical systems.
Dilute-acid pretreatment of barley straw for biological hydrogen production using Caldicellulosiruptor saccharolyticus
Panagiotopoulos, I.A. ; Bakker, R.R.C. ; Vrije, G.J. de; Claassen, P.A.M. ; Koukios, E.G. - \ 2012
International Journal of Hydrogen Energy 37 (2012)16. - ISSN 0360-3199 - p. 11727 - 11734.
thermotoga-neapolitana - extreme thermophiles - inhibitory compounds - wheat-straw - biomass - fermentation - hydrolysis - severity - microflora - conversion
The main objective of this study was to use the fermentability test to investigate the feasibility of applying various dilute acids in the pretreatment of barley straw for biological hydrogen production. At a fixed acid loading of 1% (w/w dry matter) 28-32% of barley straw was converted to soluble monomeric sugars, while at a fixed combined severity of -0.8 30 -32% of the straw was converted to soluble monomeric sugars. With fermentability tests at sugar concentrations 10 and 20 g/L the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus showed good hydrogen production on hydrolysates of straw pretreated with H3PO4 and H2SO4, and to a lesser extent, HNO3. The fermentability of the hydrolysate of straw pretreated with HCl was lower compared to the other acids but equally high as that of pure sugars. At sugar concentration 30 g/L the fermentability of all hydrolysates was low.
An investigation into the chemical composition of alternative invertebrate prey
Oonincx, D.G.A.B. ; Dierenfeld, E.S. - \ 2012
Zoo Biology 31 (2012)1. - ISSN 0733-3188 - p. 40 - 54.
iron storage disease - nutrient composition - tenebrio-molitor - beta-carotene - nutrition - insects - birds - food - arthropods - conversion
The aim of this study was to determine the chemical composition of eight invertebrate species and evaluate their suitability as alternative prey. The species selected were rusty red cockroaches (Blatta lateralis), six-spotted cockroaches (Eublaberus distanti), Madagascar hissing cockroaches (Gromphadorhina portentosa), fruit flies (Drosophila melanogaster), false katydids (Microcentrum rhombifolium), beetles of the mealworm (Tenebrio molitor), and superworm beetles (Zophobas morio), as well as woodlice (Porcellio scaber). Dry matter (DM), crude protein, crude fat, neutral detergent fiber, acid detergent fiber, ash, macro and trace minerals, vitamins A and E, and carotenoid concentrations were quantified. Significant differences were found between species. Crude protein content ranged from 38 to 76% DM, fat from14 to 54% DM, and ash from 2 to 8% DM. In most species, calcium:phosphorus was low (0.08-0.30:1); however, P. scaber was an exception (12:1) and might prove useful as a dietary source of calcium for insectivores. Vitamin E content was low for most species (6-16¿mg/kg DM), except for D. melanogaster and M. rhombifolium (112 and 110¿mg/kg DM). The retinol content, as a measure of vitamin A activity, was low in all specimens, but varied greatly among samples (0.670-886¿mg/kg DM). The data presented can be used to alter diets to better suit the estimated requirements of insectivores in captivity. Future research on the topic of composition of invertebrate prey species should focus on determination of nutrient differences owing to species, developmental stage, and diet.
Carbon stocks and dynamics under improved tropical pasture and silvopastoral
Mosquera Vidal, O. ; Buurman, P. ; Ramirez, B.L. ; Amezquita, M.C. - \ 2012
Geoderma 189-190 (2012). - ISSN 0016-7061 - p. 81 - 86.
northeastern costa-rica - soil organic-matter - brazilian amazonia - eastern amazonia - forest - conversion - delta-c-13 - rondonia
To evaluate the effect of land use change on soil organic carbon, the carbon contents and stocks of primary forest, degraded pasture, and four improved pasture systems in Colombian Amazonia were compared in a flat and a sloping landscape. The improved pastures were Brachiaria humidicola, and Brachiaria decumbens, either in monoculture or in combination with native legumes. The age of the treatments was 30 years for degraded pasture and 10 or 15 years for each of the improved pastures. Carbon fractions were Total C, Oxidizable C, and Non-Oxidizable (stable) C. Stocks were compared using a fixed soil mass base. The degraded pasture in the flat landscape was abandoned and dominated by weeds, while that in the sloping area was overgrazed. The latter had much lower C stocks than the former. B. humidicola monoculture had the highest stocks both in flat and sloping areas, while the effect of the other three treatments varied. C replacement based on d13C indicated that after 30 years, the degraded pasture still contained more than 50% forest-derived C in its topsoil. The fraction in the topsoil that is not replaced roughly coincides with the Stable C fraction. d13C values suggest that the changes in carbon stocks ascribed to differences in land use may be – at least partially – inherited from the previous land use, thus confusing the interpretation of land use effects. Nevertheless, the introduction of improved pastures on degraded grassland is a feasible alternative of land use both for carbon sequestration and as an attractive economic alternative to farmers.
The oxidative esterification of glycerol to methyl glycerate in methanol using gold on oxidic supports: an insight in product selectivity
Pazhavelikkakath Purushothaman, R.K. ; Haveren, J. van; Es, D.S. van; Heeres, H.J. - \ 2012
Green Chemistry 14 (2012). - ISSN 1463-9262 - p. 2031 - 2037.
aqueous-phase oxidation - bimetallic catalysts - commodity chemicals - carbon-monoxide - au catalysts - lactic-acid - derivatives - adsorption - conversion - kinetics
Gold nanoparticles on different oxidic supports (TiO2, Al2O3 and ZnO) have been studied for the oxidation of glycerol in methanol, using molecular oxygen as the oxidizing agent in a batch set-up. The main oxidation products are methyl glycerate and dimethyl mesoxalate in over 95% selectivity at high glycerol conversion, indicating that C–C bond scission occurs at a significantly lower extent compared to glycerol oxidations in water. The product selectivity is a function of the support. Highest selectivity (82% at 72% conversion) to methyl glycerate is observed in the case of Au/TiO2 as the catalyst. The use of a base is not essential for the glycerol oxidation reaction to occur, although for TiO2 and Al2O3 higher initial activities are found in the presence of sodium methoxide. Au/ZnO gives comparable activity and selectivity both in the presence and absence of a base. Oxidation experiments with reaction intermediates indicate that oxidation of methyl glycerate to higher oxygenates does not occur to a significant extent in methanol. An alternative pathway for the formation of dimethyl mesoxalate involving dihydroxyacetone is proposed.
Making conservation research more relevant for conservation practitioners
Laurance, W.F. ; Koster, H. ; Grooten, M. ; Anderson, A.B. ; Zuidema, P.A. ; Zwick, S. ; Zagt, R.J. ; Lynam, A.J. ; Linkie, M. ; Anten, N.P.R. - \ 2012
Biological Conservation 153 (2012). - ISSN 0006-3207 - p. 164 - 168.
wicked problems - amazon - biology - forest - oil - biodiversity - conversion - future - tigers - brazil
Conservation scientists and practitioners share many of the same goals. Yet in a majority of cases, we argue, research conducted by academic conservation scientists actually makes surprisingly few direct contributions to environmental conservation. We illustrate how researchers can increase the utility and impact of their scientific findings for real-world conservation, using examples of pressing environmental challenges. These examples demonstrate some practices and principles that scientists can adopt to better assist conservation practitioners and advance specific conservation outcomes. These include (1) producing time-critical research rapidly enough to affect political outcomes; (2) attacking ‘wicked’ problems that transcend traditional scientific approaches; (3) using multidisciplinary approaches that link science with fields such as economics, sociology, and politics; and (4) communicating in a bolder, more direct manner in the public arena to advance environmental conservation. We conclude with a plea for more proactive dialogue between conservation scientists and practitioners when devising research priorities.
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