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  • 1.
    Akinbomi, Julius
    University of Borås, Faculty of Textiles, Engineering and Business.
    Fermentative hydrogen and methane productions using membrane bioreactors2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The role of energy as a stimulant for economic growth and environmental sustainabilityof any nation has made the focus on green fuels, including fermentative hydrogen (bioH2) andmethane (bioCH4), to be a priority for the World’s policy makers. Nigeria, as the most populousAfrican country, with worsening energy crisis, can benefit from the introduction of the bioH2 andbioCH4 technologies into the country’s energy mix, since such technologies have the potential ofgenerating energy from organic wastes such as fruit waste.Fruit waste was studied in detail in this work because of its great economic andenvironmental potential, as large quantities of the wastes (10–65% of raw fruit) are generatedfrom fruit consumption and processing. Meanwhile, bioH2 and bioCH4 productions involvinganaerobic microorganisms in direct contact with organic wastes have been observed to result insubstrate and product inhibitions, which reduce the gas yields and limit the application of thetechnologies on an industrial scale. For example, in this study, the first experimental work todetermine the effects of hydraulic retention times and fruit mixing on bioH2 production fromsingle and mixed fruits revealed the highest cumulative bioH2 yield to be equivalent to 30% ofthe theoretical yield. However, combining the fermentation process with the application ofmembrane encapsulated cells and membrane separation techniques, respectively, could reducesubstrate and product inhibitions of the microorganisms. This study, therefore, focused on theapplication of membrane techniques to enhance the yields of bioH2 and bioCH4 productions fromthe organic wastes.The second experimental work which focused on reduction of substrate inhibition,involved the investigation of the effects of the PVDF membrane encapsulation techniques on thebioH2 and bioCH4 productions from nutrient media with limonene, myrcene, octanol and hexanalas fruit flavours. The results showed that membrane encapsulated cells produced bioCH4 fasterand lasted longer, compared to free cells in limonene. Also, about 60% membrane protectiveeffect against myrcene, octanol and hexanal inhibitions was obtained. Regarding bioH2production, membrane encapsulated cells, compared to free cells, produced higher average dailyyields of 94, 30 and 77% with hexanal, myrcene and octanol as flavours, respectively. The finalpart of the study, which was aimed at reducing product inhibition, involved the study of theeffects of membrane permeation of volatile fatty acids (VFAs) on the bioreactor hydrodynamicsin relation to bioH2 production. The investigation revealed that low transmembrane pressure of104Pa was required to achieve a 3L h-1m-2 critical flux with reversible fouling mainly due to cakelayer formation, and bioH2 production was also observed to restart after VFAs removal.The results from this study suggest that membrane-based techniques could improve bioH2and bioCH4 productions from fermentation media with substrate and product inhibitions.

  • 2.
    Bakare, Fatimat Oluwatoyin
    University of Borås, Faculty of Textiles, Engineering and Business.
    Development of biocomposites from lactic acid thermoset resins and cellulose fibre reinforcements2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Synthesis of polymers from renewable origin has been reported by many authors and it has been found out that it has enormous potential and can serve as alternative to conventional thermoplastics and thermosets in many applications. The use of these renewable resources will provide sustainable platforms to substitute fossil fuel-based materials. To date, efforts made to produce 100% bio-based thermosetting materials have yet to be achieved. Many studies have been reported on increasing the renewability ratio of thermoset materials produced.

    A lot of reports have been made on the synthesis of thermoplastic resins from lactic acid for biomedical applications such as tissue engineering but only few reports have been made on composite applications. The issue of high melt viscosity of thermoplastic resins from lactic acid has been of paramount problem because of its difficulty in impregnation into fibre reinforcement. Bio-based thermoset resins have been produced for composite applications from plant oils and improved mechanical properties have been achieved.

    In this thesis, an alternative route for synthesis of lactic acid based thermoset resins have been explored to solve the above problem. Thermoset resins were synthesized from lactic acid with different co-reactants and were characterized using NMR, FT-IR, DSC, DMA and TGA. Their rheological properties were also investigated. The resins were reinforced with natural and regenerated cellulose fibres in non-woven and woven form, and with different fibre alignment and fibre loading. The resulting composites were characterized by mechanical testing regarding tensile, flexural and impact strength, and by SEM analysis regarding morphology.

    The results showed that these composites could possibly be used in automobile, transport, construction and furniture applications, particularly for interior purposes. The resins produced were found to be promising materials for composite production due to the good mechanical properties achieved.

  • 3. Carillo-Nieves, Danay
    et al.
    Zumalacárregui-de Cárdenas, Lourdes
    Franco-Rico, Rafael
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Kinetic of biogas production from oil palm empty fruit bunches2014In: Dyna, ISSN 0012-7353, Vol. 81, no 187, 96-101 p.Article in journal (Refereed)
  • 4.
    Ferreira, Jorge
    University of Borås, Faculty of Textiles, Engineering and Business.
    Integration of filamentous fungi in ethanol dry-mill biorefinery2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The industrial production of bioethanol as a replacement to gasoline is well-established worldwide, using starch- or sugar-rich substrates. Additionally, the bioethanol plants produce animal feeds derived from fermentation leftovers. The biorefinery character of bioethanol plants can be enhanced via process diversification. This entails the production of more value-added products, which can be accomplished by including edible filamentous fungi as the second biocatalysts while taking advantage of the available equipment for cost-effective inclusion. The process diversification can be achieved either via valorisation of the process leftovers or via inclusion of other residual substrates.

     

    In dry-mill biorefineries, baker’s yeast is unable to consume residual pentose sugars and other more complex substrates in the process leftovers so called whole stillage and thin stillage. Edible ascomycetes and zygomycetes fungi can be used to accomplish yeast and consume those residual substrates in stillage as well as from external substrates of lignocellulosic origin, e.g. spent sulphite liquor and wheat straw. The conversion of these substrates to ethanol, and biomass rich in protein, lipids, respective essential amino acids and fatty acids as well as chitosan was investigated in this thesis.

     

    Among the filamentous fungi studied, Neurospora intermedia was the best ethanol producer from thin stillage. Process developments included primary shake-flasks experiments, followed by pilot scale-up using 26 L, 2.3 m3 and 80 m3 bioreactors. The 26 L bioreactor, as a bubble column led to similar performance as an airlift bioreactor, and also a continuous mode could be successfully used instead of a batch process. By using a dilution rate of 0.1 h-1, around 5 g/L of ethanol and 4 g/L of biomass rich in protein, lipids, amino acids and fatty acids essential to humans were obtained. The inclusion of the process can potentially lead to a spent medium lower in solids and viscosity which may facilitate the energy-intensive evaporation and drying steps as well as the water recycling back to the process. By applying a two-stage cultivation with whole stillage, up to 7.6 g/L of ethanol could be produced using 1 FPU cellulase/g suspended solids and 5.8 g/L of biomass containing 42% (w/w) crude protein. In the first stage (ethanol production), N. intermedia was used, while Aspergillus oryzae was the biocatalyst in the second stage for further biomass production. Both strains were able to degrade complex substrates both in liquid and solid fraction of whole stillage. The extrinsic substrates included spent sulphite liquor and pretreated wheat straw slurry. When the former was used, up to around 7 g/L of Rhizopus sp. could be obtained in a 26 L airlift bioreactor. The biomass was rich in protein and lipids (30–50% and 2–7% on a dry weight basis, respectively). The monomers of the latter were continuously filtered for production of biomass under simultaneous saccharification fermentation and filtration. Biomass yields of up to 0.34 g/g of consumed monomeric sugars and acetic acid were obtained.

     

    The inclusion of the process for valorisation of thin stillage can potentially lead to the production of 11,000 m3 ethanol and 6,300 tonnes of biomass at a typical facility producing 200,000 m3 ethanol/year.

  • 5. Hashemi Gheinani, Ali
    et al.
    Haghayegh Jahromi, Neda
    Feuk-Lagerstedt, E
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad J
    University of Borås, School of Engineering.
    RNA silencing of lactate dehydrogenase gene in Rhizopus oryzae2011In: Journal of RNAi and Gene Silencing, ISSN 1747-0854, E-ISSN 1747-0854, ISSN 1747-0854, Vol. 7, 443-448 p.Article in journal (Refereed)
    Abstract [en]

    Rhizopus oryzae is a filamentous fungus, belonging to the order Mucorales. It can ferment a wide range of carbohydrates hydrolyzed from lignocellulosic materials and even cellobiose to produce ethanol. However, R. oryzae also produces lactic acid as a major metabolite, which reduces the yield of ethanol. In this study, we show that significant reduction of lactic acid production could be achieved by short (25nt) synthetic siRNAs targeting the ldhA gene. The average yield of lactic acid production by R. oryzae during the batch fermentation process, where glucose had been used as a sole carbon source, diminished from 0.07gm/gm in wild type to 0.01gm/gm in silenced samples. In contrast, the average yield of ethanol production increased from 0.39gm/gm in wild type to 0.45gm/gm in silenced samples. These results show 85.7% (gm/gm) reduction in lactic acid production as compared with the wild type R. oryzae, while an increase of 15.4% (gm/gm) in ethanol yield.

  • 6. Hashemi, Seyed Sajad
    et al.
    Karimi, Keikhosro
    Nosratpour, Mohammad Javad
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Efficient Biogas and Ethanol Production from Safflower Straw Using Sodium Carbonate Pretreatment2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 12, 10592-10601 p.Article in journal (Refereed)
  • 7. Holliger, Christof
    et al.
    Alves, Madalena
    Andrade, Diana
    Angelidaki, Irini
    Astals, Sergi
    Baier, Urs
    Bougrier, Claire
    Buffière, Pierre
    Carballa, Marta
    de Wilde, Vinnie
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Towards a standardization of biomethane potential tests2016In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 74, no 11, 2515-2522 p.Article in journal (Refereed)
    Abstract [en]

    Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.

  • 8.
    Kabir, Maryam M
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bioprocessing of Recalcitrant Substrates for Biogas Production2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The application of anaerobic digestion (AD) as a sustainable waste management technology is growing worldwide, due to high energy prices as well as increasingly strict environmental regulations. The growth of the AD industry necessitates exploring new substrates for their utilisation in AD processes. The present work investigates the AD of two recalcitrant biomass: lignocelluloses and keratin-rich residues. The complex nature of these waste streams limits their biological degradation; therefore, suitable pre-processing is required prior to the AD process.In the first part of the study, the effects of organic solvent pre-treatments on bioconversion of lignocelluloses (straw and forest residues) to biogas were evaluated. Pre-treatment with N-methylmorpholine-N-oxide (NMMO) resulted in minor changes in the composition of the substrates, while their digestibility significantly increased. Furthermore, due to the high cost of the NNMO, the effect of pre-treatment with the recycled solvent was also explored. Since it was found that the presence of small traces of NMMO in the system after the treatment has inhibitory effects on AD, pre-treatments of forest residues using other organic solvents, i.e. acetic acid, ethanol, and methanol, were investigated too. Although pre-treatments with acetic acid and ethanol led to the highest methane yields, the techno-economical evaluation of the process showed that pre-treatment with methanol was the most viable economically, primarily due to the lower cost of methanol, compared to that of the other solvents.In the second part of the work, wool textile wastes were subjected to biogas production. Wool is mainly composed of keratin, an extremely strong and resistible structural protein. Thermal, enzymatic and combined treatments were, therefore, performed to enhance the methane yield. The soluble protein content of the pre-treated samples showed that combined thermal and enzymatic treatments had significantly positive effects on wool degradation, resulting in the highest methane yields, i.e. 10–20-fold higher methane production, compared to that obtained from the untreated samples.In the last part of this thesis work, dry digestion of wheat straw and wool textile waste, as well as their co-digestion were studied. The total solid (TS) contents applied in the digesters were between 6–30% during the investigations. The volumetric methane productivity was significantly enhanced when the TS was increased from 6 to 13–21%. This can be a beneficial factor when considering the economic feasibility of large-scale dry AD processes.

  • 9.
    Kabir, Maryam M.
    et al.
    University of Borås, School of Engineering.
    Forgács, Gergely
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Biogas from lignocellulosic materials2015In: Lignocellulose-Based Bioproducts, Switzerland: Springer international publishing , 2015, 207-251 p.Chapter in book (Other academic)
  • 10.
    Kahoush, May
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business. ENSAIT.
    Behary, Nemeshwaree
    ENSAIT.
    Cayla, Aurélie
    ENSAIT.
    Nierstrasz, Vincent
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bio-Fenton and Bio-Electro-Fenton as sustainable methods for degrading organic pollutants in wastewater2017In: Process Biochemistry, ISSN 1359-5113, E-ISSN 1873-3298Article in journal (Refereed)
  • 11. Karimi, Keikhosro
    et al.
    Tabatabaei, Meisam
    Microbial Biotechnology Department, Agricultural Biotechnology Research Institute of Iran (ABRII.
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Kumar, Rajeev
    6 Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California.
    Recent trends in acetone, butanol, and ethanol (ABE) production2015In: Biofuel Research Journal, Vol. 2, no 4, 301-308 p.Article in journal (Refereed)
  • 12.
    Kumar, Rajeev
    et al.
    6 Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California.
    Tabatabaei, Meisam
    Microbial Biotechnology Department, Agricultural Biotechnology Research Institute of Iran (ABRII.
    Karimi, Keikhosro
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Recent updates on lignocellulosic biomass derived ethanol-A review2016In: Biofuel Research Journal, Vol. 3, no 1, 347-356 p.Article in journal (Refereed)
    Abstract [en]

    Lignocellulosic (or cellulosic) biomass derived ethanol is the most promising near/long term fuel candidate. In addition, cellulosic biomass derived ethanol may serve a precursor to other fuels and chemicals that are currently derived from unsustainable sources and/or are proposed to be derived from cellulosic biomass. However, the processing cost for second generation ethanol is still high to make the process commercially profitable and replicable. In this review, recent trends in cellulosic biomass ethanol derived via biochemical route are reviewed with main focus on current research efforts that are being undertaken to realize high product yields/titers and bring the overall cost down.

  • 13.
    Mahboubi, Amir
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ferreira, Jorge A.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Taherzadeh, Mohammad J
    University of Borås, Faculty of Textiles, Engineering and Business.
    Lennartsson, Patrik R.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Production of Fungal Biomass for Feed, Fatty Acids, and Glycerol by Aspergillus oryzae from Fat-Rich Dairy Substrates2017In: Fermentation, ISSN 2311-5637, Vol. 3, no 4Article in journal (Other academic)
    Abstract [en]

    Dairy waste is a complex mixture of nutrients requiring an integrated strategy for valorization into various products. The present work adds insights into the conversion of fat-rich dairy products into biomass, glycerol, and fatty acids via submerged cultivation with edible filamentous fungi. The pH influenced fat degradation, where Aspergillus oryzae lipase was more active at neutral than acidic pH (17 g/L vs. 0.5 g/L of released glycerol); the same trend was found during cultivation in crème fraiche (12 g/L vs. 1.7 g/L of released glycerol). In addition to glycerol, as a result of fat degradation, up to 3.6 and 4.5 g/L of myristic and palmitic acid, respectively, were released during A. oryzae growth in cream. The fungus was also able to grow in media containing 16 g/L of lactic acid, a common contaminant of dairy waste, being beneficial to naturally increase the initial acidic pH and trigger fat degradation. Considering that lactose consumption is suppressed in fat-rich media, a two-stage cultivation for conversion of dairy waste is also proposed in this work. Such an approach would provide biomass for possibly feed or human consumption, fatty acids, and an effluent of low organic matter tackling environmental and social problems associated with the dairy sector.

  • 14. Mirmohamadsadeghi, Safoora
    et al.
    Karimi, Keikhosro
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Improvement of Solid-State Biogas Production from Wood by Concentrated Phosphoric Acid Pretreatment2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 2, 3230-3243 p.Article in journal (Refereed)
    Abstract [en]

    Cellulose Solvent-And organic Solvent-Based lignocellulose fractionation (COSLIF) has been repeatedly shown to be a Cost-Effective and promising process to modify the structure of different lignocelluloses. It has been repeatedly reported to improve enzymatic hydrolysis and ethanol production from different lignocelluloses. In this study, COSLIF was used to improve biomethane production from pine (softwood), poplar (soft hardwood), and berry (hard hardwood) via solid state anaerobic digestion (SSAD). Feed to inoculum (F/I) ratio, which plays a major role in SSAD, was set to 3, 4, and 5. After the pretreatment, 39, 33, and 24% higher methane yield from pine was achieved for F/I ratios of 3, 4, and 5, respectively. However, the methane yield from the hardwoods was not improved by the pretreatment, which was related to overloading of the digester. Compositional analysis showed considerable reduction in hemicellulose and lignin content by the pretreatment. Structural changes in the woods, before and after the pretreatment, were examined by X-Ray diffractometer and scanning electron microscopy. The results showed that the crystallinity of cellulose was decreased and accessible surface area was drastically increased by the pretreatment.

  • 15. Mirmohamadsadeghi, Safoora
    et al.
    Karimi, Keikhosro
    Zamani, Akram
    Amiri, Hamid
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Enhanced solid-state biogas production from lignocellulosic biomass by organosolv pretreatment2014In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2014Article in journal (Refereed)
  • 16.
    Moradian, Farzad
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ash Behavior in Fluidized-Bed Combustion and Gasification of Biomass and Waste Fuels: Experimental and Modeling Approach2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the past few decades, a growing interest in the thermal conversion of alternative fuels such as biomass and waste-derived fuels has been observed among the energy-producing companies. Apart from meeting the increasing demand for sustainable heat and power production, other advantages such as reducing global warming and ameliorating landfilling issues have been identified. Among the available thermal conversion technologies, combustion in grate-fired furnaces is by far the most common mode of fuel conversion. In recent years, Fluidized-Bed (FB) technologies have grown to become one of the most suitable technologies for combustion and gasification of biomass and waste-derived fuels.In spite of the benefits, however, some difficulties are attributed to the thermal conversion of the alternative fuels. Ash-related issues could be a potential problem, as low-grade fuels may include considerable concentrations of ash-forming elements such as K, Na, S, Ca, Mg, P, Si and Cl. These elements undergo many undesirable chemical and physical transformations during the thermal conversion, and often cause operational problems such as deposition-related issues, slag formation in furnaces, corrosion of the heat transfer surfaces, and bed agglomeration of the fluidized-beds. Ash-related problems in the utility boilers are a major concern that may result in decreased efficiency, unscheduled outages, equipment failures, increased cleaning and high maintenance costs.This thesis investigated the ash behavior and ash-related problems in two different FB conversion systems: a Bubbling Fluidized-Bed (BFB) boiler combusting solid waste, and a Dual Fluidized-Bed (DFB) gasifier using biomass as feedstock. Full-scale measurements, chemical analysis of fuel and ash, as well as thermodynamic equilibrium modeling have been carried out for the BFB boiler (Papers I-IV), to investigate the impact of reduced-bed temperature (RBT) and also co-combustion of animal waste (AW) on the ash transformation behavior and the extent of ash-related issues in the boiler. For the DFB gasifier (Paper V), a thermodynamic equilibrium model was developed to assess the risk of bed agglomeration when forest residues are used as feedstock.The experimental results showed that the RBT and AW co-combustion could decrease or even resolve the ash-related issues in the BFB boiler, resulting in a lower deposit-growth rate in the superheater region, eliminating agglomerates, and a less corrosive deposit (in RBT case). Thermodynamic equilibrium modeling of the BFB boiler gave a better understanding of the ash transformation behavior, and also proved to be a reliable tool for predicting the risk of bed agglomeration and fouling. The modeling of the DFB gasifier indicated a low risk of bed agglomeration using the forest residues as feedstock and olivine as bed material, which was in good agreement following the observations in a full-scale DFB gasifier.

  • 17.
    Pagés Diaz, Jhosané
    University of Borås, Faculty of Textiles, Engineering and Business.
    Biogas from slaughterhouse waste: Mixtures interactions in co-digestion2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Global environmental concerns connected to the use of fossil fuels have forced the development ofalternative sustainable energy technologies. The application of anaerobic digestion, from waste streams thatcurrently have no use, can be utilized for bioenergy production. Due to the high protein and fat content,slaughterhouse waste has a high potential for biogas production. However, potential inhibitory compoundscan be formed during the degradation of the proteins and lipids, which can make the process sensitive andprone to failure. One of the ways to overcome these problems is co-digestion with carbohydrate-rich cosubstratesi.e., a mixture of agro-wastes with low protein/lipid content. This also leads to a better nutritionalbalance and enhanced methane yield due to the positive mixture interactions.

    In this study, four different waste fractions, i.e., solid cattle slaughterhouse waste (SB), manure (M),various crops (VC), and the organic fraction of municipal solid waste (MSW) were investigated in monodigestionand co-digestion processes. Different mixture ratios were prepared, and the methane yield (YCH4),the specific methanogenic activity (SMA), and a kinetic parameter (k0) were determined using the batchdigestion assays at thermophilic conditions (55oC). The SB had a lower degradation rate and lower SMAcompared with those of the other samples. In order to investigate the effect of the temperature, a selectedmixture ratio was also digested at mesophilic conditions (37oC), which resulted in a decrease in YCH4 and inthe kinetic parameters, specific methane production rate (rsCH4), and k0, by up to 57% compared to thoseobtained at the thermophilic conditions. During the next part of the work, a four-factor mixture design wasapplied aiming to obtain possible synergetic or antagonistic effects. The performance of the process wasassessed using YCH4and rsCH4as the response variables. Mixing all four of the substrates resulted in a 31%increase in the YCH4compared to the expected yield calculated on the basis of the methane potential of theindividual fractions and 97% of the theoretical methane yield, clearly demonstrating a synergistic effect.Nevertheless, antagonistic interactions were also observed for certain mixtures. In order to maximize boththe response variables simultaneously, a response surface method was employed to find the optimalcombination for the substrate mixture.

    The impact of the mixture interactions, obtained in the batch operation mode, was also evaluated undersemi-continuous co-digestion. Digestion of the SB as the sole substrate failed at an organic loading rate of0.9 gVS L-1d-1, while stable performance with higher loadings was observed for mixtures that displayedsynergy earlier during the batch experiments. The combination that showed the antagonistic effects resultedin unstable operation and poor representation of methanogens. It was proved that synergetic or antagonisticeffects observed in the batch mode could be correlated to the process performance, as well as to thedevelopment of the microbial community structure during the semi-continuous operation.

    In the last part of the work, the response of the methanogenic biomass to the consecutive feeding applied inthe batch assays was evaluated regarding process parameters such as YCH4, SMA, and degradation kinetics.The objective was to examine whether there is a possibility to correlate these findings to the expectedprocess performance during the long-term operation. Digestion of the SB alone showed a total inhibitionafter the second feeding, which is in correlation with the failure observed during the semi-continuous mode.Furthermore, enhanced SMA was observed after the second feeding in those mixtures that showed synergyin the previous batch assays as well as a good process performance during the semi-continuous operation.

  • 18.
    Pagés Díaz, Jhosané
    et al.
    University of Borås, School of Engineering.
    Pereda Reyes, Ileana
    Lundin, Magnus
    University of Borås, School of Engineering.
    Sárvári Horváth, Ilona
    University of Borås, School of Engineering.
    Co-digestion of different waste mixtures from agro-industrial activities: Kinetic evaluation and synergetic effects2011In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 23, 10834-10840 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Several wastes from agro-industrial activities were mixed in different ratios to evaluate the co-digestion process. Methane yield (YCH4), specific methanogenic activity (SMA) and a kinetic parameter (k0) were determined. A second feeding was also performed to examine the recovery of bacterial activity after exhaustion. Mixture ratios of 1:1:1:1 and 1:3:4:0.5 (w/w) showed the best performance, with YCH4 of 664; 582 NmL CH4/gVSsubstrate, as well as SMA of 0.12; 0.13 gCODNmLCH4/gVSinoculum/d, respectively, during the digestion of the first feed. It was possible to relate synergetic effects with enhancement in YCH4 by up to 43%, compared with values calculated from YCH4 of the individual substrates. All batches started up the biogas production after an exhaustion period, when a second feed was added. However, long lag phases (up to 21 days) were observed due to stressed conditions caused by the substrate limitation prior to the second feed.

  • 19.
    Pereda Reyes, Ileana
    et al.
    Centro de Estudio de Ingenieria de Procesos Study Center of Process Engineering (CIPRO), High Polytechnic Institute “José Antonio Echeverría”.
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Anaerobic Biodegradation of Solid Substrates from Agroindustrial Activities—Slaughterhouse Wastes and Agrowastes2015In: Biodegradation and bioremediation ofpolluted systems – New advances and technologies, Croatia: InTech , 2015Chapter in book (Refereed)
  • 20.
    Rajendran, Karthik
    University of Borås, Faculty of Textiles, Engineering and Business.
    Industrial Bioprocess Developments for Biogas and Ethanol Production2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Current biofuels face a noteworthy misfortune on commercialization because of its economiccomparison with low-cost fuel from the oil reserves. To compete with gasoline as a fuel, thebiofuels need to be economically feasible and demonstrated on a large-scale. Biogas and ethanolhave a great potential as commercial biofuels, even though it has difficulties, for example, highcapitalinvestment, absence of demonstrated innovations, and availability of raw materials and soforth. This thesis focuses on different application-driven bioprocess developments for improvingthe techno-economic feasibility of the biogas and ethanol industries.

    The biogas industry was studied from three different perspectives:

    1) Modeling approach in which a Process Simulation Model (PSM) model was developed forpredicting the biogas productions, as exploiting new substrates is vital for a biogas industrygrowth. The PSM model was created using Aspen Plus® which includes 46 reactions of differentphases in the Anaerobic Digestion (AD) processes. It also contains certain important processparameters, thermodynamics, rate-kinetics, and inhibitions involved in the AD processes. PSMwas a library model for the AD processes, which was validated against the laboratory andindustrial data. The validation showed that the PSM predicted the biogas production about 5% inexcess, which could ease the biogas industry to predict biogas from new substrates.

    2) Simulation approach to study the imperative components affecting the profitability of theplant. For this purpose, a local municipality plant was studied under distinct situations. The choiceof upgrading method, capacity, cost of waste and its processing, number of digesters used, etc.were exploited. The results showed that the collection and transportation fee, landfilling fee, andthe reduced operation of a plant were the main considerations in influencing its profitability.Moreover, it was identified that for bigger cities the decentralization strategy could beat theexpense of collection and transportation of waste, and the plant could obtain a 17.8% return oninvestment.

    3) Rethinking digester technology in which the cost of the digester was significantly lessenedusing a cutting-edge textile, which was principally intended for developing countries. The digestercost played an important role in consuming biogas for different applications. The textile digesterwas tested on a laboratory scale, followed by field tests in different countries including India,Indonesia, and Brazil. Textile digesters cost one-tenth of the conventional digesters, and thepayback was more or less between 1–3 years, when replacing the Liquefied Petroleum Gas (LPG)and kerosene as a cooking fuel for households.

    When it comes to ethanol, the first generation ethanol production using grains was financiallypossible with a payback of about 13 years. Nonetheless, with the fluctuation of the oil prices, theethanol industries need to look for alternative sources of revenues. Different retrofits wereconsidered, including the effect of thin-stillage/whole-stillage to ethanol and biomass, in additionto the integration of the first and second generation ethanol production. The results revealed that4% additional ethanol could be obtained when the thin-stillage was converted into ethanol andfungal biomass, while the payback was reduced to 11.5 years. The integration of the first andsecond generation ethanol production revealed that it has a positive influence on the overalleconomics of the process with a payback of 10.5 years. This could help the ethanol industries toconsider a revamp for a better environmental, economic, and energy efficient process.

  • 21.
    Ramamoorthy, Sunil Kumar
    University of Borås, Faculty of Textiles, Engineering and Business.
    Properties and performance of regenerated cellulose thermoset biocomposites2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biocomposites have been developed to address the sustainability issues of nonrenewableresource based materials. These composites are often produced by reinforcing natural fibres in petroleum based thermoset resins or thermoplastic polymers. Thermoplastic polymers from renewable resources are commercially available, whereas thermoset resins are predominantly derived from crude oil resources. Cellulose fibres have significant importance and potential for polymer reinforcement in lightweight composites. Natural fibres are chemically diverse and their properties vary largely which makes it difficult for them to be used in several applications. The natural fibre based products are limited by their characteristic odour emissions. These issues of natural fibres can be addressed by partly manmade fibres i.e. regenerated cellulose fibre which with little or no compromise in the environmental benefits of the natural fibres can be produced from biomass origin. Natural fibres and their composites have been observed and researched closely for many decades. Study of regenerated cellulose fibres and their composites is, on the other hand, relatively new. Regenerated cellulose fibres are prospective reinforcing material in the composite field due to their even quality and high purity. These fibres have good mechanical properties and also address the odour emission issue of the natural fibres. The development of biocomposites from regenerated cellulose fibre and thermoset resin synthesized from renewable resources has therefore been viewed with considerable interest.

    This thesis describes the development of biocomposites from regenerated cellulose fibres (lyocell and viscose) and thermoset resins synthesized from renewable resources (soybean oil and lactic acid). The performance and the properties of the composites were evaluated. Chemical surface treatments, alkali and silane, were performed on the fibres in order to improve the performance of the composites. Hybrid composites were also produced by mixing of two types of reinforcement in order to complement one type of fibre with other. The developed composites were evaluated through mechanical, thermal, viscoelastic and morphological properties among others. The results showed that the regenerated cellulose fibre thermoset biocomposites have reasonably good properties. Fibres before and after treatment were studied in detail. The silane treatment on these fibres improved the mechanical properties of the composites as the silane molecules act as a link between the fibre and resin which gives the molecular continuity across the interface region of the composite.

  • 22.
    Sárvári Horváth, Ilona
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Tabatabaei, Meisam
    Microbial Biotechnology Department, Agricultural Biotechnology Research Institute of Iran (ABRII.
    Karimi, Keikhosro
    Kumar, Rajeev
    6 Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California.
    Recent updates on biogas production-a review2016In: Biofuel Research Journal, Vol. 3, no 2, 394-402 p.Article in journal (Refereed)
    Abstract [en]

    One of the greatest challenges facing the societies now and in the future is the reduction of green house gas emissions and thus preventing the climate change. It is therefore important to replace fossil fuels with renewable sources, such as biogas. Biogas can be produced from various organic waste streams or as a byproduct from industrial processes. Beside energy production, the degradation of organic waste through anaerobic digestion offers other advantages, such as the prevention of odor release and the decrease of pathogens. Moreover, the nutrient rich digested residues can be utilized as fertilizer for recycling the nutrients back to the fields. However, the amount of organic materials currently available for biogas production is limited and new substrates as well as new effective technologies are therefore needed to facilitate the growth of the biogas industry all over the world. Hence, major developments have been made during the last decades regarding the utilization of lignocellulosic biomass, the development of high rate systems, and the application of membrane technologies within the anaerobic digestion process in order to overcome the shortcomings encountered. The degradation of organic material requires a synchronized action of different groups of microorganisms with different metabolic capacities. Recent developments in molecular biology techniques have provided the research community with a valuable tool for improved understanding of this complex microbiological system, which in turn could help optimize and control the process in an effective way in the future.

  • 23.
    Tabatabaei, Meisam
    et al.
    Microbial Biotechnology Department, Agricultural Biotechnology Research Institute of Iran (ABRII.
    Karimi, Keikhosro
    Department of Chemical Engineering, Isfahan University of Technology.
    Kumar, Rajeev
    6 Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California.
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Renewable Energy and Alternative Fuel Technologies2015In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141Article in journal (Other academic)
  • 24.
    Tabatabaei, Meisam
    et al.
    Microbial Biotechnology Department, Agricultural Biotechnology Research Institute of Iran (ABRII.
    Karimi, Keikhosro
    Department of Chemical Engineering, Isfahan University of Technology.
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Kumar, Rajeev
    6 Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California.
    Recent trends in biodiesel production2015In: Biofuel Research Journal, Vol. 2, no 3, 258-267 p.Article in journal (Refereed)
    Abstract [en]

    This article fully discusses the recent trends in the production of one the most attractive types of biofuels, i.e., biodiesel.with a focus on the existing obstacles for its large scale production. Moreover, recent innovations/improvements under three categories of upstream, mainstream, and downstream processes are also presented. Upstream strategies are mainly focused on seeking more sustainable oil feedstocks and/or enhancing the quality of waste-oriented ones. The mainstream strategies section highlights the numerous attempts made to enhance agitation efficiency including chemical and/or mechanical strategies. Finally, the innovative downstream strategies basically dealing with 1) separation of biodiesel and glycerin, 2) purification of biodiesel and glycerin, and 3) improving the characteristics of the produced fuel, are comprehensively reviewed.

  • 25.
    Teghammar, Anna
    et al.
    University of Borås, School of Engineering.
    Karimi, Keikhosro
    University of Borås, School of Engineering.
    Sárvári Horváth, Ilona
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad
    University of Borås, School of Engineering.
    Enhanced biogas production from rice straw, triticale straw and softwood spruce by NMMO pretreatment2012In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 36, 116-120 p.Article in journal (Refereed)
    Abstract [en]

    Softwoodspruce (chips and milled), ricestraw and triticale (a hybrid of rye and wheat) straw, were pretreated with N-methylmorpholine-N-oxide (NMMO or NMO) prior to anaerobic digestion to produce biogas. The pretreatments were performed at 130 °C for 1–15 h, and the digestions continued for six weeks. The digestions of untreated chips (10 mm) and milled (<1 mm) spruce, ricestraw and triticalestraw resulted in 11, 66, 22 and 30 Nml CH4/g raw material. However, the pretreatments have improved these methane yields by 400–1200%. The best digestion results of the pretreated chips and milled spruce, ricestraw and triticalestraw were 125, 245, 157 and 203 Nml CH4/g raw material (or 202, 395, 328 and 362 Nml CH4/g carbohydrates) respectively, which correspond to 49, 95, 79 and 87% of the theoretical yield of 415 Nml CH4/g carbohydrates. Although the experiments were carried out for six weeks, one and a half weeks was enough to digest the materials.

1 - 25 of 25
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