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  • 1.
    Atasoy, Merve
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Eyice, Ozge
    Queen Mary Univ London, Sch Biol & Chem Sci, London E1 4NS, England..
    Cetecioglu, Zeynep
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Volatile fatty acid production from semi-synthetic milk processing wastewater under alkali pH: The pearls and pitfalls of microbial culture2020In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 297, article id 122415Article in journal (Refereed)
    Abstract [en]

    Volatile fatty acids (WA) are one of the most promising sustainable and environmentally friendly bioproduct owing to their wide usage area and high market demand. For this reason, in this study, the evaluation of VFA production from pure and mixed bacterial cultures was aimed. Three different mixed cultures with C. aceticum, C. butyricum and P. acidipropionici as pure cultures were used for inoculation of milk processing wastewater fermentation under pH 10 for 15 days. The mixed culture fermentation had the highest VFA production efficiency whereas the highest amount of acetic, butyric and propionic acid productions were obtained by C. aceticum, C. butyricum and P. acidipropionici, respectively. Also, the mixed cultures demonstrated faster pH regulation and acclimation than the pure cultures tested. Therefore, development of synthetic cultures may offer a useful approach to produce VFA mixtures with one-dominant acid type and with high production efficiency.

  • 2.
    Atasoy, Merve
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Eyice, Ozge
    Queen Mary Univ London, Sch Biol & Chem Sci, London E1 4NS, England..
    Schnurer, Anna
    Swedish Univ Agr Sci, Dept Mol Sci, Bioctr, SE-75007 Uppsala, Sweden..
    Cetecioglu, Zeynep
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Volatile fatty acids production via mixed culture fermentation: Revealing the link between pH, inoculum type and bacterial composition2019In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 292, article id 121889Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to investigate the effects of operational parameters, inoculum type and bacterial community on mixed culture fermentation to produce one dominant acid type in the mixture of volatile fatty acids (VFA). The study was performed using three different inocula (large&small granular and slurry) with glucose under various initial pH. The VFA production efficiency reached to 0,97 (gCOD/gSCOD) by granular sludge. VFA composition was changed by initial pH: in neutral conditions, acetic acid; in acidic conditions, acetic and butyric acids, in alkali conditions butyric acid were dominated, respectively. The VFA production was positively affected by the high relative abundance of Firmicutes. On the contrary, a negative correlation was seen between VFA production and the relative abundance of Chloroflexi. The results revealed the physical sludge structure of inoculum was the key factor for production efficiency, whereas, pH was the most important parameter to affect VFA composition.

  • 3.
    Atasoy, Merve
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Owusu-Agyeman, Isaac
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Cetecioglu, Zeynep
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Bio-based volatile fatty acid production and recovery from waste streams: Current status and future challenges2018In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 268, p. 773-786Article, review/survey (Refereed)
    Abstract [en]

    Bio-based volatile fatty acid (VFA) production from waste-stream is getting attention due to increasing market demand and wide range usage area as well as its cost-effective and environmentally friendly approach. The aim of this paper is to give a comprehensive review of bio-based VFA production and recovery methods and to give an opinion on future research outlook. Effects of operation conditions including pH, temperature, retention time, type of substrate and mixed microbial cultures on VFA production and composition were reviewed. The recovery methods in terms of gas stripping with absorption, adsorption, solvent extraction, electrodialysis, reverse osmosis, nanofiltration, and membrane contractor of VFA were evaluated. Furthermore, strategies to enhance bio-based VFA production and recovery from waste streams, specifically, in-line VFA recovery and bioaugmentation, which are currently not used in common practice, are seen as some of the approaches to enhance bio-based VFA production.

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  • 4.
    Azeem, Muhammad
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Borg-Karlson, Anna Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Sustainable bio-production of styrene from forest waste2013In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 144, p. 684-688Article in journal (Refereed)
    Abstract [en]

    A strain of Penicillium expansum was studied for the production of styrene using forest waste biomass as a feeding substrate. The fungal strain was cultivated on bark of various trees supplemented with yeast extract and the volatiles produced were collected on Tenax TA and analyzed by gas chromatography-mass spectrometry. Fungus cultured on grated soft bark of pine (Pinus sylvestris) stems (GPB) and mature bark of oak (Quercus robur) supplemented with yeast extract produced relatively the highest amounts of styrene. The maximum styrene production rate was 52.5 mu g/h, 41 mu g/h and 27 mu g/h from fungus cultivated on 50 mL liquid media with 10 g GPB or mature bark of oak and potato dextrose broth respectively. These promising results suggest that the fungal strain could be used to produce "green" styrene plastics using renewable forest waste biomass.

  • 5. Cadena, Edith M.
    et al.
    Du, Xueyu
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Fillat, Amanda
    García-Ubasart, Jordi
    Vidal, Teresa
    Colom, Josep F.
    On hexenuronic acid (HexA) removal and mediator coupling to pulp fiber in the laccase/mediator treatment2011In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 4, p. 3911-3917Article in journal (Refereed)
    Abstract [en]

    Flax soda/AQ pulps were treated with different fungal laccase-mediator combinations followed by physical and chemical characterization of the pulps to obtain a thorough understanding of the laccase/mediator effects on hexenuronic acid (HexA) removal and the coupling of mediator onto pulps for fiber functionalization. Large differences were found and the presence of lauryl gallate (LG) during Trametes villosa laccase (TvL) treatment (TvL + LG) resulted in a much larger reduction of pulp-linked HexA than the combination of p-coumaric acid (PCA) and Pycnoporus cinnabarinus laccase (PcL). A major portion of LG became attached to the pulp as revealed by an increase in the kappa number and further confirmed by thioacidolysis and H-1 NMR analysis of solubilized pulp fractions. Additional experiments with other chemical pulps and isolated pulp xylan and lignin revealed that HexA seems to be the sole pulp component attacked by TvL + LG. As a substrate for TvL, the reaction preference order is PCA > HexA > LG.

  • 6.
    Chen, Xiaowen
    et al.
    University of Maine, USA.
    Lawoko, Martin
    University of Maine, USA.
    van Heiningen, Adriaan
    University of Maine USA.
    Kinetics and mechanism of autohydrolysis of hardwoods2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 20, p. 7812-7819Article in journal (Refereed)
    Abstract [en]

    Autohydrolysis using water is a promising method to extract hemicelluloses from wood prior to pulping in order to make co-products such as ethanol and acetic acid besides pulp. Many studies have been carried out on the kinetics and mechanism of autohydrolysis using batch reactors. The present study was performed in a continuous mixed flow reactor where the wood chips are retained in a basket inside the reactor. This reactor is well suited to determine intrinsic kinetics of hemicellulose dissolution because the dissolved products are rapidly removed from the reactor, thus minimizing further hydrolysis and degradation of the hemicelluloses in solution. The xylan removal rate follows an S-shaped behavior. GPC analysis of the continuously removed extract shows that the dissolved xylan oligomers have a DP smaller than about 25. Lignin-free xylan oligomers and cellulose oligomers are the major components dissolved in the initial stage of autohydrolysis, while xylan covalently bound to lignin (i.e. an LCC) is the major component removed during the later stage of autohydrolysis. The molecular weight of the dissolved components decreases with time in the second stage. The kinetics of xylan removal are explained in terms of a mechanism based on recent knowledge of the ultrastructure of the cell fibre wall.

  • 7. Corbin, Kendall R.
    et al.
    Hsieh, Yves S. Y.
    University of Adelaide, Australia.
    Betts, Natalie S.
    Byrt, Caitlin S.
    Henderson, Marilyn
    Stork, Jozsef
    DeBolt, Seth
    Fincher, Geoffrey B.
    Burton, Rachel A.
    Grape marc as a source of carbohydrates for bioethanol: Chemical composition, pre-treatment and saccharification.2015In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 193, p. 76-83, article id S0960-8524(15)00816-0Article in journal (Refereed)
    Abstract [en]

    Global grape production could generate up to 13 Mt/yr of wasted biomass. The compositions of Cabernet Sauvignon (red marc) and Sauvignon Blanc (white marc) were analyzed with a view to using marc as raw material for biofuel production. On a dry weight basis, 31-54% w/w of the grape marc consisted of carbohydrate, of which 47-80% was soluble in aqueous media. Ethanol insoluble residues consisted mainly of polyphenols, pectic polysaccharides, heteroxylans and cellulose. Acid and thermal pre-treatments were investigated for their effects on subsequent cellulose saccharification. A 0.5M sulfuric acid pre-treatment yielded a 10% increase in the amount of liberated glucose after enzymatic saccharification. The theoretical amount of bioethanol that could be produced by fermentation of grape marc was up to 400 L/t. However, bioethanol from only soluble carbohydrates could yield 270 L/t, leaving a polyphenol enriched fraction that may be used in animal feed or as fertilizer.

  • 8.
    Cucarella, Victor
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Zaleski, Tomasz
    Department of Soil Science and Soil Protection, Agricultural University of Cracow.
    Mazurek, Ryszard
    Department of Soil Science and Soil Protection, Agricultural University of Cracow.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Effect of reactive substrates used for phosphorus removal from wastewater on the feritlity of acid soils2008In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 99, no 10, p. 4308-4314Article in journal (Refereed)
    Abstract [en]

    Reactive substrates used in filter systems can reduce phosphorus (P) pollution and, once saturated with P, may be recycled in agriculture. These substrates are usually calcium carbonate derivates with high pH values, which may be particularly beneficial for acid soils. Three reactive substrates (Filtra P, Polonite and wollastonite) saturated with P were used as amendments to an acid soil in a pot experiment. Substrate amendments tended to improve ryegrass yield and P uptake compared with control and potassium phosphate treatments. Polonite produced the highest yield/amendment ratio, while Polonite and Filtra P significantly increased the concentrations of P and Ca in the ryegrass. Addition of all three substrates increased the pH, AL-extractable P and cation exchange capacity of soils during the experiment. These substrates can therefore be applied to acid soils in order to recycle P and improve soil properties.

  • 9. Ermolaev, E.
    et al.
    Sundberg, Cecilia
    Swedish University of Agricultural Sciences.
    Pell, M.
    Jönsson, H.
    Greenhouse gas emissions from home composting in practice2014In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 151, p. 174-182Article in journal (Refereed)
    Abstract [en]

    In Sweden, 16% of all biologically treated food waste is home composted. Emissions of the greenhouse gases CH4 and N2O and emissions of NH3 from home composts were measured and factors affecting these emissions were examined. Gas and substrate in the compost bins were sampled and the composting conditions assessed 13 times during a 1-year period in 18 home composts managed by the home owners. The influence of process parameters and management factors was evaluated by regression analysis. The mean CH4 and N2O concentration was 28.1 and 5.46 ppm (v/v), respectively, above the ambient level and the CH4:CO2 and N2O:CO2 ratio was 0.38% and 0.15%, respectively (median values 0.04% and 0.07%, respectively). The home composts emitted less CH4 than large-scale composts, but similar amounts of N2O. Overall NH3 concentrations were low. Increasing the temperature, moisture content, mixing frequency and amount of added waste all increased CH4 emissions.

  • 10. Gosselink, Richard J. A.
    et al.
    Teunissen, Wouter
    van Dam, Jan E. G.
    de Jong, Ed
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Scott, Elinor L.
    Sanders, Johan P. M.
    Lignin depolymerisation in supercritical carbon dioxide/acetone/water fluid for the production of aromatic chemicals2012In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 106, p. 173-177Article in journal (Refereed)
    Abstract [en]

    Valorisation of lignin plays a key role in further development of lignocellulosic biorefinery processes the production of biofuels and bio-based materials. In the present study, organosolv hardwood and wheat straw lignins were converted in a supercritical fluid consisting of carbon dioxide/acetone/water (300-370 degrees C, 100 bar) to a phenolic oil consisting of oligomeric fragments and monomeric aromatic compounds with a total yield of 10-12% based on lignin. These yields are similar to the state-of-the-art technologies such as base-catalysed thermal processes applied for lignin depolymerisation. Addition of formic acid increases the yield of monomeric aromatic species by stabilizing aromatic radicals. Supercritical depolymerisation of wheat straw and hardwood lignin yielded monomeric compounds in different compositions with a maximum yield of 2.0% for syringic acid and 3.6% for syringol, respectively. The results of the present study showed that under the applied conditions competition occurred between lignin depolymerisation and recondensation of fragments.

  • 11.
    Grimm, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Zanzi, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Björnbom, Emilia
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Cukierman, A. L.
    Tecnología Especial, Depto Tecnología Farmacéutica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires.
    Comparison of different types of biomasses for copper biosorption2007In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 99, no 7, p. 25559-2565Article in journal (Refereed)
    Abstract [en]

    Three biomass, birch wood Betula sp., marine brown alga Fucus vesiculosus, and terrestrial moss Pleurozium schreberi, have been compared as raw materials for preparation of biosorbents for removal of copper ions from diluted water solutions. Small sample doses (0.5 g/100 ml) of the biosorbents prepared from alga and moss enabled more than 90% removal of Cu(II) ions from diluted water solutions (5-20 mg/l). The sample from sawdust was less effective.A pseudo-second-order rate model properly described the experimental kinetic data for the biosorbents. The maximum sorption capacities (X,) determined from the experimental equilibrium isotherms by applying the Langmuir model showed that the alga had the best copper-binding ability (X-m = 23.4 mg/g), followed by the moss (X-m = 11.1 mg/g), and the sawdust (X-m = 4.9 mg/g). No visible damages or performance losses were detected for the alga and moss after five sorption-desorption cycles using diluted HCl as eluent.

  • 12.
    Hylander, Lars D.
    et al.
    Department of Earth Sciences, Uppsala University.
    Kietlinska, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Simán, Gyula
    Division of Plant Nutrition, Department of Soil Science, Swedish University of Agricultural Sciences.
    Phosphorus retention in filter materials for wastewater treatment and its subsequent suitability for plant production2006In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 97, no 7, p. 914-921Article in journal (Refereed)
    Abstract [en]

    Constructed sand filter beds are advantageous for the treatment of wastewater in areas with a low population density. Phosphorus-sorbing materials with additional beneficial characteristics may be used instead of sand. This study aimed at determining and comparing phosphorus (P) retention capacities of amorphous and crystalline blast furnace slags, limestone, opoka, Polonite (R) and sand, for filtering domestic wastewater through columns over a period of 67 weeks. The P-enriched filter materials were subsequently tested for their fertilizer effectiveness in a pot experiment where barley was cultivated. Polonite (R), i.e. calcinated bedrock opoka, was most effective in removing P. This Occurred at a relatively high hydraulic conductivity that reduced the risk of clogging. Barley grown in two types of slag, with a grain size of 0.25-4, mm. was most effective in dry matter production followed by Polonite (R). Fine-grained slags and Polonite (R) were suggested its most suited of the investigated materials to recycle P back to agriculture.

  • 13.
    Ibarra, David
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Köpcke, Viviana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Larsson, Per Tomas
    Jääskeläinen, Anna-Stiina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Combination of alkaline and enzymatic treatments as a process for upgrading sisal paper-grade pulp to dissolving-grade pulp2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 19, p. 7416-7423Article in journal (Refereed)
    Abstract [en]

    A sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction and a final endoglucanase treatment was investigated as a process for upgrading non-wood paper-grade pulps to dissolving-grade pulps for viscose production. Five commercial dried bleached non-wood soda/ AQ paper pulps, from flax, hemp, sisal, abaca, and jute, were studied for this purpose. Commercial dried bleached eucalyptus dissolving pulp was used as reference sample. Sisal pulp showed the highest improvement in Fock's reactivity, reaching levels nearly as high or even higher than that of eucalyptus dissolving pulp (65%), and a low hemicellulose content (3-4%) when was subjected to this sequence of treatments. The viscosity, however, decreased considerably. A uniform and narrow molecular weight distribution was observed by size exclusion chromatography. C-13 nuclear magnetic resonance spectroscopy and Raman microspectroscopy revealed that the cellulose structure consisted of cellulose I.

  • 14.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Effective water content reduction in sewage wastewater sludge using magnetic nanoparticles2014In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 153, p. 333-339Article in journal (Refereed)
    Abstract [en]

    The present work compares the use of three flocculants for sedimentation of sludge and sludge water content from sewage wastewater i.e. magnetic iron oxide nanoparticles (MION), ferrous sulfate (chemical) and Moringa crude extract (protein). Sludge water content, wet/dry weight, turbidity and color were performed for, time kinetics and large-scale experiment. A 30% reduction of the sludge water content was observed when the wastewater was treated with either protein or chemical coagulant. The separation of sludge from wastewater treated with MION was achieved in less than 5. min using an external magnet, resulted in 95% reduction of sludge water content. Furthermore, MION formed denser flocs and more than 80% reduction of microbial content was observed in large volume experiments. The results revealed that MION is efficient in rapid separation of sludge with very low water content, and thus could be a suitable alternative for sludge sedimentation and dewatering in wastewater treatment processes.

  • 15.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Effect of magnetic iron oxide nanoparticles in surface water treatment: Trace minerals and microbes2013In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 129, p. 612-615Article in journal (Refereed)
    Abstract [en]

    The existing water treatment process often uses chemicals, which is of high health and environmental concern. The present study focused on the efficiency of microemulsion prepared magnetic iron oxide nanoparticles (ME-MIONs) and protein-functionalized nanoparticles (MOCP. +. ME-MIONs) in water treatment. Their influence on mineral ions and microorganisms present in the surface water from lake Brunnsviken and örlången, Sweden were investigated. Ion analysis of water samples before and after treatment with nanoparticles was performed. Microbial content was analyzed by colony forming units (CFU/ml). The results impart that ME-MIONs could reduce the water turbidity even in low turbid water samples. Reduction of microbial content (98%) was observed at 37 °C and more than 90% reduction was seen at RT and 30 °C when compared to untreated samples from lake örlången. The investigated surface water treatment method with ME-MIONs was not significantly affecting the mineral ion composition, which implies their potential complement in the existing treatment process.

  • 16.
    Li, Jiebing
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Toven, Kai
    Steam explosion lignins; their extraction, structure and potential as feedstock for biodiesel and chemicals2009In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 100, no 9, p. 2556-2561Article in journal (Refereed)
    Abstract [en]

    In the present study, a steam explosion wood pre-treatment process, optimized earlier with respect to ethanol production, has been applied to both softwoods (Picea abies and Pinus sylvestris) and hardwoods (Betula verrucosa and Populus tremula). The alkaline extractable lignins have then been isolated to investigate lignin separation efficiency and lignin structure and to evaluate their potential for producing value-added products, such as biodiesel components or chemicals, in terms of the purity, molecular size, functional groups, beta-O-4' inter-unit linkage content, and degradability in a subsequent processing treatment. The mechanism of lignin modification and possible improvements to the steam explosion pre-treatment process are discussed.

  • 17.
    Li, Jiebing
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lignin depolymerization/repolymerization and its critical role for delignification of aspen wood by steam explosion2007In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 98, no 16, p. 3061-3068Article in journal (Refereed)
    Abstract [en]

    Steam explosion is an important process for the fractionation of biomass components. In order to understand the behaviour of lignin under the conditions encountered in the steam explosion process, as well as in other types of steam treatment, aspen wood and isolated lignin from aspen were subjected to steam treatment under various conditions. The lignin portion was analyzed using NMR and size exclusion chromatography as major analytical techniques. Thereby, the competition between lignin depolymerization and repolymerization was revealed and the conditions required for these two types of reaction identified. Addition of a reactive phenol, 2-naphthol, was shown to inhibit the repolymerization reaction strongly, resulting in a highly improved delignification by subsequent solvent extraction and an extracted lignin of uniform structure.

  • 18.
    Malovanyy, Andriy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Trela, Jozef
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. IVL Swedish Environmental Institute, Valhallavägen 81, Stockholm, Sweden.
    Plaza, Elzbieta
    Mainstream wastewater treatment in integrated fixed film activated sludge (IFAS) reactor by partial nitritation/anammox process2015In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 198, p. 478-487Article in journal (Refereed)
    Abstract [en]

    In this study the system based on the combination of biofilm and activated sludge (IFAS - integrated fixed film activated sludge) was tested and compared with a system that relies only on biofilm (MBBR - moving bed biofilm reactor) for nitrogen removal from municipal wastewater by deammonification process. By introduction of suspended biomass into MBBR the nitrogen removal efficiency increased from 36 +/- 3% to 70 +/- 4% with simultaneous 3-fold increase of nitrogen removal rate. Results of batch tests and continuous reactor operation showed that organotrophic nitrate reduction to nitrite, followed by anammox reaction contributed to this high removal efficiency. After sCOD/NH4-N ratio decreased from 1.8 +/- 0.2 to 1.3 +/- 0.1 removal efficiency decreased to 52 +/- 4%, while still maintaining 150% higher removal rate, comparing to MBBR. Activity tests revealed that affinity of NOB to oxygen is higher than affinity of AOB with half-saturation constants of 0.05 and 0.41 mg/L, respectively.

  • 19.
    Malovanyy, Andriy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Yang, Jingjing
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Trela, Jozef
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Combination of upflow anaerobic sludge blanket (UASB) reactor and partial nitritation/anammox moving bed biofilm reactor (MBBR) for municipal wastewater treatment2015In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 180, p. 144-153Article in journal (Refereed)
    Abstract [en]

    In this study the combination of an upflow anaerobic sludge blanket (UASB) reactor and a deammonification moving bed biofilm reactor (MBBR) for mainstream wastewater treatment was tested. The competition between aerobic ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) was studied during a 5 months period of transition from reject water to mainstream wastewater followed by a 16 months period of mainstream wastewater treatment. The decrease of influent ammonium concentration led to a wash-out of suspended biomass which had a major contribution to nitrite production. Influence of a dissolved oxygen concentration and a transient anoxia mechanism of NOB suppression were studied. It was shown that anoxic phase duration has no effect on NOB metabolism recovery and oxygen diffusion rather than affinities of AOB and NOB to oxygen determine the rate of nitrogen conversion in a biofilm system. Anammox activity remained on the level comparable to reject water treatment systems.

  • 20.
    Naqvi, Muhammad
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Dahlquist, Erik
    School of Sustainable Development of Society and Technology, Mälardalen University, Sweden.
    Black liquor gasification integrated in pulp and paper mills: A critical review2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 21, p. 8001-8015Article, review/survey (Refereed)
    Abstract [en]

    Black liquor gasification (BLG) has potential to replace a Tomlinson recovery boiler as an alternative technology to increase safety, flexibility and energy efficiency of pulp and paper mills. This paper presents an extensive literature review of the research and development of various BLG technologies over recent years based on low and high temperature gasification that include SCA-Billerud process, Manufacturing and Technology Conversion International (MTCI) process, direct alkali regeneration system (DARS), BLG with direct causticization, Chemrec BLG system, and catalytic hydrothermal BLG. A few technologies were tested on pilot scale but most of them were abandoned due to technical inferiority and very fewer are now at commercial stage. The drivers for the commercialization of BLG enabling bio-refinery operations at modern pulp mills, co-producing pulp and value added energy products, are discussed. In addition, the potential areas of research and development in BLG required to solve the critical issues and to fill research knowledge gaps are addressed and highlighted. (c) 2010 Elsevier Ltd. All rights reserved.

  • 21.
    Naqvi, Muhammad
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Dahlquist, Erik
    School of Sustainable Development of Society and Technology, Mälardalen University, Sweden.
    Energy conversion performance of black liquor gasification to hydrogen production using direct causticization with CO2 capture2012In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 110, p. 637-644Article in journal (Refereed)
    Abstract [en]

    This paper estimates potential hydrogen production via dry black liquor gasification system with direct causticization integrated with a reference pulp mill. The advantage of using direct causticization is elimination of energy intensive lime kiln. Pressure swing adsorption is integrated in the carbon capture process for hydrogen upgrading. The energy conversion performance of the integrated system is compared with other bio-fuel alternatives and evaluated based on system performance indicators. The results indicated a significant hydrogen production potential (about 141MW) with an energy ratio of about 0.74 from the reference black liquor capacity (about 243.5MW) and extra biomass import (about 50MW) to compensate total energy deficit. About 867,000tonnes of CO2 abatement per year is estimated i.e. combining CO2 capture and CO2 offset from hydrogen replacing motor gasoline. The hydrogen production offers a substantial motor fuel replacement especially in regions with large pulp and paper industry e.g. about 63% of domestic gasoline replacement in Sweden.

  • 22.
    Naqvi, Muhammad
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Froling, M.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Bio-refinery system of DME or CH4 production from black liquor gasification in pulp mills2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 3, p. 937-944Article in journal (Refereed)
    Abstract [en]

    There is great interest in developing black liquor gasification technology over recent years for efficient recovery of bio-based residues in chemical pulp mills. Two potential technologies of producing dimethyl ether (DIME) and methane (CH4) as alternative fuels from black liquor gasification integrated with the pulp mill have been studied and compared in this paper. System performance is evaluated based on: (i) comparison with the reference pulp mill, (ii) fuel to product efficiency (FTPE) and (iii) biofuel production potential (BPP). The comparison with the reference mill shows that black liquor to biofuel route will add a highly significant new revenue stream to the pulp industry. The results indicate a large potential of DME and CH4 production globally in terms of black liquor availability. BPP and FTPE of CH4 production is higher than DME due to more optimized integration with the pulping process and elimination of evaporation unit in the pulp mill.

  • 23. Nehrenheim, E.
    et al.
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Kinetic sorption modelling of Cu, Ni, Zn, Pb and Cr ions to pine bark and blast furnace slag by using batch experiments2008In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 99, no 6, p. 1571-1577Article in journal (Refereed)
    Abstract [en]

    Storm water and landfill leachate can both contain significant amounts of toxic metals such as Zn, Cu, Pb, Cr and Ni. Pine bark and blast furnace slag are both residual waste products that have shown a large potential for metal removal from contaminated water. There are however many variables that must be optimized in order to achieve efficient metal retention. One of these variables is the time of which the solution is in contact with each unit of filter material. Metal sorption was studied in two laboratory experiments to improve the knowledge of the effects of contact time. The results showed that pine bark was generally more efficient than blast furnace slag when the metal concentrations were relatively small, whereas blast furnace slag sorbed most metals to a larger extent at increased metal loads. In addition, sorption to blast furnace slag was found to be faster than metal binding to pine bark. A pseudo-second-order kinetic model was able to describe the data well within 1000 s of reaction time.

  • 24.
    Owusu-Agyeman, Isaac
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Eyice, Özge
    Cetecioglu, Zeynep
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    The study of structure of anaerobic granules and methane producing pathways of pilot-scale UASB reactors treating municipal wastewater under sub-mesophilic conditions2019In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 290, article id 121733Article in journal (Refereed)
    Abstract [en]

    This study was carried out to investigate the relationship between the methane producing pathways and the characteristics of anaerobic granules treating municipal wastewater. For this purpose, two pilot scale upflow anaerobic sludge blanket reactors with different granule size distribution (1-2 mm and 3-4 mm) were investigated at operating temperatures of 20 degrees C and 28 degrees C for 239 days. There was an increased and stable biogas production when temperature was elevated to 28 degrees C likely due to reduction in methane solubility. Larger granules had multi-layered internal microstructures with higher acetoclastic methanogenic activities (250-437 mL CH(4)g(-1) VS d(-1)) than smaller granules (150-260 mL CH(4)g(-1) VS d(-1)). The relative abundance of acetoclastic methanogens of larger granules was higher, confirming acetoclastic methane producing pathway was more prominent. However, there was no significant difference in the performance of the two reactors because they were operating below their capacities in terms of organic loading rate to volatile solids ratio.

  • 25. Persson, F.
    et al.
    Sultana, Razia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Suarez, M.
    Hermansson, M.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Wilén, B. -M
    Structure and composition of biofilm communities in a moving bed biofilm reactor for nitritation-anammox at low temperatures2014In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 154, p. 267-273Article in journal (Refereed)
    Abstract [en]

    It is a challenge to apply anaerobic ammonium oxidation (anammox) for nitrogen removal from wastewater at low temperatures. Maintenance of anammox- and aerobic ammonia oxidizing bacteria (AOB) and suppression of nitrite oxidizing bacteria (NOB) are key issues. In this work, a nitritation-anammox moving bed biofilm pilot reactor was operated at 19-10°C for 300d. Nitrogen removal was decreasing, but stable, at 19-13°C. At 10°C removal became unstable. Quantitative PCR, fluorescence in situ hybridization and gene sequencing showed that no major microbial community changes were observed with decreased temperature. Anammox bacteria dominated the biofilm (0.9-1.2×1014 16S rRNA copies m-2). Most anammox bacteria were similar to Brocadia sp. 40, but another smaller Brocadia population was present near the biofilm-water interface, where also the AOB community (Nitrosomonas) was concentrated in thin layers (1.8-5.3×1012 amoA copies m-2). NOB (Nitrobacter, Nitrospira) were always present at low concentrations (<1.3×1011 16S rRNA copies m-2).

  • 26. Prasetyo, Endry Nugroho
    et al.
    Kudanga, Tukayi
    Ostergaard, Lars
    Rencoret, Jorge
    Gutierrez, Ana
    del Rio, Jose C.
    Ignacio Santos, J.
    Nieto, Lidia
    Jimenez-Barbero, Jesus
    Martinez, Angel T.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gellerstedt, Goran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lepifre, Stephane
    Silva, Carla
    Kim, Su Yeon
    Cavaco-Paulo, Artur
    Klausen, Bente Seljebakken
    Lutnaes, Bjart Frode
    Nyanhongo, Gibson S.
    Guebitz, Georg M.
    Polymerization of lignosulfonates by the laccase-HBT (1-hydroxybenzotriazole) system improves dispersibility2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 14, p. 5054-5062Article in journal (Refereed)
    Abstract [en]

    The ability of laccases from Trametes villosa (TvL), Myceliophthora thermophila (MtL), Trametes hirsuta (ThL) and Bacillus subtilis (BsL) to improve the dispersion properties of calcium lignosulfonates 398 in the presence of HBT as a mediator was investigated. Size exclusion chromatography showed an extensive increase in molecular weight of the samples incubated with TvL and ThL by 107% and 572% from 28400 Da after 17 h of incubation, respectively. Interestingly, FTIR spectroscopy. C-13 NMR and Py-GC/MS analysis of the treated samples suggested no substantial changes in the aromatic signal of the lignosulfonates, a good indication of the ability of TvL/ThL-HBT systems to limit their effect on functional groups without degrading the lignin backbone. Further, the enzymatic treatments led to a general increase in the dispersion properties, indeed a welcome development for its application in polymer blends. (C) 2010 Elsevier Ltd. All rights reserved.

  • 27. Singh, Rajesh
    et al.
    Kumar, Anil
    Kirrolia, Anita
    Kumar, Rajender
    KTH, School of Chemical Science and Engineering (CHE).
    Yadav, Neeru
    Bishnoi, Narsi R.
    Lohchab, Rajesh K.
    Removal of sulphate, COD and Cr(VI) in simulated and real wastewater by sulphate reducing bacteria enrichment in small bioreactor and FTIR study2011In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 2, p. 677-682Article in journal (Refereed)
    Abstract [en]

    The present study was conducted to investigate the chromium(VI), COD and sulphate removal efficiency from aqueous solution and treatment of real effluent (CETP) in a small scale bioreactor using sulphate reducing bacteria consortium. Effect of different hydraulic retention times (HRTs), initial metal concentrations, various carbon sources and temperatures were studied on removal of chromium(VI), COD and sulphate. Maximum chromium(VI) and sulphate removal was found to be 96.0% and 82.0%, respectively, at initial concentration of 50 mg l(-1) using lactate as carbon source. However, highest COD removal was 36.2% in medium containing fructose as the carbon source and electron donor. NADH dependent chromate reductase activity was not observed which indicated the anaerobic consortium. Initially consortium medium with a strong negative oxidation reduction potential indicated the reducing activity. The FTIR spectrum of the sulphate reducing bacteria consortium clearly shows the existence of the sulphate ions and signifies that sulfate reducing bacteria have used sulfate during the growth phase.

  • 28. Skoulou, V.
    et al.
    Swiderski, Artur
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Zabaniotou, A.
    Process characteristics and products of olive kernel high temperature steam gasification (HTSG)2009In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 100, no 8, p. 2444-2451Article in journal (Refereed)
    Abstract [en]

    Exploitation of olive kernel for bioenergy production, with respect to the green house gases (GHGs) mitigation, is the main aim of this work. In this study, olive kernels were used as a solid biofuel, and high temperature steam gasification (HTSG) was investigated, in the fixed bed unit at KTH Sweden, with regard to hydrogen maximization in the produced gasification gas. Experiments were carried out in a temperature range of 750-1050 degrees C, with steam as the gasifying agent. The behaviour of olive kernels, under residence times from 120 up to 960 s, has been studied. At 1050 degrees C, a medium to high calorific value gas was obtained (LHVgas = 13.62 MJ/Nm(3)). while an acquired H-2/CO molar ratio equal to four proved that olive kernel HTSG gasification could be an effective technology for a hydrogen-rich gas production (similar to 40%vv H-2 in the produced gasification gas at 1050 degrees C). The produced char contained 79%ww of fixed carbon, low chlorine and sulphur content, which enables it for further re-use for energetic purposes. Tar content in the produced gas at 750 degrees C was 124.07 g/Nm(3), while a 1050 degrees C at 79.64% reduction was observed and reached the value of 25.26 g/Nm(3).

  • 29. Song, Han
    et al.
    Dotzauer, Erik
    Thorin, Eva
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Annual performance analysis and comparison of pellet production integrated with an existing combined heat and power plant2011In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 10, p. 6317-6325Article in journal (Refereed)
    Abstract [en]

    Three optional pellet production processes integrated with an existing biomass-based CHP plant using different raw materials (wood chips and solid hydrolysis residues) are studied. The year is divided into 12 periods, and the integrated biorefinery systems are modeled and simulated for each period. The annual economic performance of three integrated biorefinery systems is analyzed based on the simulation results. The option of pellet production integrated with the existing CHP plant with the exhaust flue gas and superheated steam as drying mediums has the lowest specific pellet production cost of 105 epsilon/t(pellet), the shortest payback time of less than 2 years and the greatest CO2 reduction of the three options. An advantage in common among the three options is a dramatic increase of the total annual power production and significant CO2 reduction in spite of a small decrease of power efficiency.

  • 30. Starfelt, F.
    et al.
    Thorin, E.
    Dotzauer, E.
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Performance evaluation of adding ethanol production into an existing combined heat and power plant2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 2, p. 613-618Article in journal (Refereed)
    Abstract [en]

    In this paper, the configuration and performance of a polygeneration system are studied by modelling the integration of a lignocellulosic wood-to-ethanol process with an existing combined heat and power (CHP) plant. Data from actual plants are applied to validate the simulation models. The integrated polygeneration system reaches a total efficiency of 50%, meeting the heating load in the district heating system. Excess heat from the ethanol production plant supplies 7.9 MW to the district heating system, accounting for 17.5% of the heat supply at full heating load. The simulation results show that the production of ethanol from woody biomass is more efficient when integrated with a CHP plant compared to a stand-alone production plant. The total biomass consumption is reduced by 13.9% while producing the same amounts of heat, electricity and ethanol fuel as in the stand-alone configurations. The results showed that another feature of the integrated polygeneration system is the longer annual operating period compared to existing cogeneration. Thus, the renewable electricity production is increased by 2.7% per year.

  • 31.
    Sundberg, Cecilia
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Franke-Whittle, I. H.
    Kauppi, S.
    Yu, D.
    Romantschuk, M.
    Insam, H.
    Jönsson, Håkan
    Characterisation of source-separated household waste intended for composting2011In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 3, p. 2859-2867Article in journal (Refereed)
    Abstract [en]

    Large-scale composting of source-separated household waste has expanded in recent years in the Nordic countries. One problem can be low pH at the start of the process. Incoming biowaste at four composting plants was characterised chemically, physically and microbiologically. The pH of food waste ranged from 4.7 to 6.1 and organic acid concentration from 24 to 81mmolkg -1. The bacterial diversity in the waste samples was high, with all samples dominated by Gammaproteobacteria, particularly Pseudomonas and Enterobacteria (Escherichia coli, Klebsiella, Enterobacter). Lactic acid bacteria were also numerically important and are known to negatively affect the composting process because the lactic acid they produce lowers the pH, inhibiting other bacteria. The bacterial groups needed for efficient composting, i.e. Bacillales and Actinobacteria, were present in appreciable amounts. The results indicated that start-up problems in the composting process can be prevented by recycling bulk material and compost.

  • 32.
    Sundberg, Cecilia
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Smårs, Sven
    Jönsson, Håkan
    Low pH as an inhibiting factor in the transition from mesophilic to thermophilic phase in composting2004In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 95, no 2, p. 145-150Article in journal (Refereed)
    Abstract [en]

    During composting of household waste, the acidity of the material affects the process during the initial phase of rising temperature. In this study, the effects of temperature (36-46°C) and pH (4.6-9.2) on the respiration rate during the early phase of composting were investigated in two different composts. A respiration method where small compost samples were incubated at constant temperature was used. The respiration rate was strongly reduced at 46°C and pH below 6, compared to composts with a higher pH or lower temperature. The combination of high temperature and low pH is a possible adverse factor in large-scale composting of food waste.

  • 33.
    Umeki, Kentaro
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Roh, Seon-ah
    Min, Tai-jin
    Namioka, Tomoaki
    Yoshikawa, Kunio
    A simple expression for the apparent reaction rate of large wood char gasification with steam2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 11, p. 4187-4192Article in journal (Refereed)
    Abstract [en]

    A simple expression for the apparent reaction rate of large wood char gasification with steam is proposed. Large char samples were gasified under steam atmosphere using a thermo-balance reactor. The apparent reaction rate was expressed as the product of the intrinsic rate and the effective factor. The effective factor was modified to include the effect of change in char diameter and intrinsic reaction rate during the reaction. Assuming uniform conversion ratio throughout a particle, the simplified reaction scheme was divided into three stages. In the initial stage, the local conversion ratio increases without particle shrinkage. In the middle stage, the particle shrinks following the shrinking core model without change in the local conversion ratio. In the final stage, the local conversion ratio increases without particle shrinkage. The validity of the modified effective value was confirmed by comparison with experimental results. (C) 2010 Elsevier Ltd. All rights reserved.

  • 34. Wen, Zhenzhong
    et al.
    Yu, Xinhai
    Tu, Shan-Tung
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Dahlquist, Erik
    Biodiesel production from waste cooking oil catalyzed by TiO2-MgO mixed oxides2010In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 24, p. 9570-9576Article in journal (Refereed)
    Abstract [en]

    Mixed oxides of TiO2-MgO obtained by the sal-gel method were used to convert waste cooking oil into biodiesel. Titanium improved the stability of the catalyst because of the defects induced by the substitution of Ti ions for Mg ions in the magnesia lattice. The best catalyst was determined to be MT-1-923, which is comprised of an Mg/Ti molar ratio of 1 and calcined at 923 K, based on an assessment of the activity and stability of the catalyst. The main reaction parameters, including methanol/oil molar ratio, catalyst amount, and temperature, were investigated. The catalytic activity of MT-1-923 decreased slowly in the reuse process. After regeneration, the activity of MT-1-923 slightly increased compared with that of the fresh catalyst due to an increase in the specific surface area and average pore diameter. The mixed oxides catalyst. TiO2-MgO, showed good potential in large-scale biodiesel production from waste cooking oil.

  • 35. Wen, Zhenzhong
    et al.
    Yu, Xinhai
    Tu, Shan-Tung
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Dahlquist, Erik
    Intensification of biodiesel synthesis using zigzag micro-channel reactors2009In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 100, no 12, p. 3054-3060Article in journal (Refereed)
    Abstract [en]

    Zigzag micro-channel reactors have been fabricated and used for continuous alkali-catalyzed biodiesel synthesis. The influences of the main geometric parameters on the performance of the micro-channel reactors were experimentally studied. it has been found that the zigzag micro-channel reactor with smaller channel size and more turns produces smaller droplets which result in higher efficiency of biodiesel synthesis. Compared to conventional stirred reactors, the time for high methyl ester conversion can be shortened significantly with the methyl ester yield of 99.5% at the residence time of only 28 s by using the optimized zigzag micro-channel reactor, which also exhibits less energy consumption for the same amount of biodiesel during biodiesel synthesis. The results indicate that zigzag micro-channel reactors can be designed as compact and mini-fuel processing plant for distributive applications.

  • 36. Winkler, M. K. H.
    et al.
    Yang, Jingjing
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Kleerebezem, R.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Trela, Jozef
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Hultman, Bengt
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    van Loosdrecht, M. C. M.
    Nitrate reduction by organotrophic Anammox bacteria in a nitritation/anammox granular sludge and a moving bed biofilm reactor2012In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 114, p. 217-223Article in journal (Refereed)
    Abstract [en]

    The effects of volatile fatty acids (VFAs) on nitrogen removal and microbial community structure in nitritation/anammox process were compared within a granular sludge reactor and a moving bed biofilm reactor. Nitrate productions in both systems were lower by 40-68% in comparison with expected nitrate production. Expected sludge production on VFAs was estimated to be 67-77% higher if heterotrophs were the main acetate degraders suggesting that Anammox bacteria used its organotrophic capability and successfully competed with general heterotrophs for organic carbon, which led to a reduced sludge production. FISH measurements showed a population consisting of mainly Anammox and AOB in both reactors and oxygen uptake rate (OUR) tests also confirmed that flocculent biomass consisted of a minor proportion of heterotrophs with a large proportion of AOBs. The dominant Anammox bacterium was Candidatus " Brocadia fulgida" with a minor fraction of Candidatus " Anammoxoglobus propionicus" both known to be capable of oxidizing VFAs.

  • 37. Wojtasz-Mucha, J.
    et al.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hydrothermal pretreatment of wood by mild steam explosion and hot water extraction2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 241, p. 120-126Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to compare the two most common hydrothermal pre-treatments for wood – mild steam explosion and hot water extraction – both with the prospect of enabling extraction of hemicelluloses and facilitating further processing. Although both involve autohydrolysis of the lignocellulosic tissue, they are performed under different conditions: the most prominent difference is the rapid, disintegrating, discharge employed in the steam explosion opening up the structure. In this comparative study, the emphasis was placed on local composition of the pre-treated wood chips (of industrially relevant size). The results show that short hot water extraction treatments lead to significant variations in the local composition within the wood chips, while steam explosion accomplishes a comparably more even removal of hemicelluloses due to the advective mass transport during the explosion step.

1 - 37 of 37
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