Hidrólisis y separación de biomasa lignocelulósica en un proceso al sulfito con el objeto de valorizar las principales fracciones dentro del concepto de bio-refinería (original) (raw)
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Dissolving cellulose is a low-yield chemical pulp (30-35 %) with a high alpha-cellulose content (91-93 %) and relatively low hemicellulose (1-10 %) and lignin (<0.05 %) content.Sugar-rich residual streams generated during sulphite pulping for dissolving pulp manufacture convert such factories into potential lignocellulosic biorefineries by integrating several modifications into the current processes by means of chemical, thermo-chemical or biochemical pathways. Mixed five and six carbon sugar platforms produced from the hydrolysis of hemicelluloses serve as substrate for biological conversion providing fuels as hydrogen or ethanol, biopolymers, and chemicals as lactic, succinic, or levulinic acids, sorbitol, furfural or xylitol. Within this hypothesis, this dissertation evaluates the possibilities of producing fermentable substrate stream, transforming an acid sulphite pulping industry located in Cantabria (Spain) into a modern lignocellulosic biorefinery. The main objective of this thesis is to study the acid sulphite process in a factory in the north of Spain and to identify the factory improvements within the biorefinery concept. First several physico-chemical characterisation methods of the feedstock (Eucalyptus globulus), product (dissolving pulp) and waste streams (hydrolysates) were carried out. In addition, four chromatographic methods for carbohydrate and derivative quantification of woody samples were set up. Afterwards, mass balance of the main components was carried out at industrial scale in order to give some conclusions about the fractionation processes and valorisation opportunities in the factory. From the study of the industrial digestion and bleaching processes, it can be concluded that there is a good cellulose separation during wood digestion (99.64 %) with the presence of 87.23 % hemicellulose and 98.47 % lignin in the spent liquor. As an example of valorisation option, 0.183 L of second-generation ethanol per kilogram of dry spent liquor can be obtained by the mill. The following step was to study the sulphite digestion stage and the effect of the most important parameters on the final dissolved sugars. The best results of the digestion step increased the amount of total monosaccharide of the spent liquor at 1.01T of dwell temperature, 0.196R and 6.20 % total SO2. Experimental cooking results were modelled giving theoretical increases of 7.33 % of monosaccharides within the spent liquor. Liquid samples were externally hydrolysed. Diluted-acid hydrolysis and concentrated-acid hydrolysis were chosen as the most adequate depolymerisation treatments. A factorial design of experiments was done to study the effect of temperature, acid concentration, acid-to-liquor ratio and time on hemicellulose depolymerisation. Diluted-acid hydrolysis showed the best results getting monosaccharide improvements of 7.9 % using 0.5 % w/w of H2SO4 at 80 ºC for 60 minutes with acid-to-liquor ratio of 10 v/v. Finally, to separate sugars from the rest of fermenting inhibitors (lignin-derived and carbohydrates-derived constituents) several detoxification techniques were implemented. Overliming, adsorption, ion exchange and liquid-liquid extraction were studied. Treatment with anionic resins was proposed as the best solution with maximum total inhibitor removals of 91.8 %. In addition, six regeneration cycles of resin were proposed for phenolics and lignosulphonate recovery. Adsorption was also adequate for lignosulphonate, phenolics and acetic acid removals reaching a maximum of 74.5 % of acetic acid removal using activated charcoal. However, adsorption processes gave high losses of sugar in the hydrolysate. Maximum bioethanol potentials of 1.231, 1.818 and 1.799 L.EtOH/Kg.dry SSL were obtained after detoxification with overliming and liquid-liquid extraction with chloroform and diethyl ether. This research proposes some recommendations and improvements in the factory in order to valorise the residual streams, not only enhancing the separation of sugars from the rest of wood constituents for fermenting purposes, but also maintaining the quality properties of the main product, dissolving pulp. Based on the whole study, diluted-acid hydrolysis, detoxification, fermentation and purification steps should be incorporated to the current sulphite mill for carbohydrates valorisation within the biorefinery concept.
Detoxification of a Lignocellulosic Waste from a Pulp Mill to Enhance Its Fermentation Prospects
Detoxification is required for sugar bioconversion and hydrolyzate valorization within the biorefining concept for biofuel or bio-product production. In this work, the spent sulfite liquor, which is the main residue provided from a pulp mill, has been detoxified. Evaporation, overliming, ionic exchange resins, and adsorption with activated carbon or black carbon were considered to separate the sugars from the inhibitors in the lignocellulosic residue. Effectiveness in terms of total and individual inhibitor removals, sugar losses and sugar-to-inhibitor removal ratio was determined. The best results were found using the cation exchange Dowex 50WX2 resin in series with the anion exchange Amberlite IRA-96 resin, which resulted in sugar losses of 24.2% with inhibitor removal of 71.3% of lignosulfonates, 84.8% of phenolics, 82.2% acetic acid, and 100% of furfurals. Apart from exchange resins, the results of evaporation, overliming, adsorption with activated carbon and adsorption with black carbon led to total inhibitor removals of 8.6%, 44.9%, 33.6% and 47.6%, respectively. Finally, some fermentation scenarios were proposed in order to evaluate the most suitable technique or combination of techniques that should be implemented in every case.
The evolution of lignin, five- and six-carbon sugars, and other decomposition products derived from hemicelluloses and cellulose was monitored in a sulfite pulp mill. The wastewater streams were characterized and the mass balances throughout digestion and total chlorine free bleaching stages were determined. Summative analysis in conjunction with pulp parameters highlights some process guidelines and valorization alternatives towards the transformation of the traditional factory into a lignocellulosic biorefinery.The results showed a good separation of cellulose (99.64%) during wood digestion, with 87.23% of hemicellulose and 98.47% lignin dissolved into the waste streams. The following steps should be carried out to increase the sugar content into the waste streams: (i) optimization of the digestion conditions increasing hemicellulose depolymerization; (ii) improvement of the ozonation and peroxide bleaching stages, avoiding deconstruction of the cellulose chains but maintaining impurity removal; (iii) fractionation of the waste water streams, separating sugars fromthe rest of toxic inhibitors for 2nd generation biofuel production. A total of 0.173 L of second-generation ethanol can be obtained in the spent liquor per gramof dry wood.The proposedmethodology can be usefully incorporated into other related industrial sectors.
Cellulose, 2019
The main source of cellulosic fibre used for pulp and paper production comes from wood, while non-wood fibres are used to a lesser extent. However, a renewed interest exists in the use of non-woody raw materials due to their abundance as source of low-cost fibres and because they are sometimes the only exploitable source of fibres in certain geographical areas, mainly in developing countries. Moreover, the great variety of characteristics, fibre dimensions and chemical composition of these alternative raw materials give them a great potential to produce different types of papers. On the other hand, the pulp and paper industry is an excellent starting point for the development of lignocellulosic biorefineries, possessing the necessary technology and infrastructure as well as extensive experience in lignocellulosic biomass transformation. Since its beginnings, the pulp and paper industry has been practicing certain aspects of the biorefinery concept, generating the energy necessary for the production of cellulosic pulp from the combustion of lignocellulosic waste and black liquors, recovering the chemical reagents used and generating high value-added products (e.g. tall oil) together with cellulosic pulp. However, the evolution of the pulp and paper industry to a lignocellulosic biorefinery requires technological innovations to make bioenergy and new bioproducts available alongside traditional products.
Bioresource Technology, 2017
In this work, a competitive process consisting of polyelectrolyte flocculation, active carbon absorption, and ion exchange was developed for hemicelluloses-derived saccharides (HDSs) purification from prehydrolysis liquor (PHL) of lignocellulose. Results showed that colloidal lignin counted for 20% of non-saccharide compounds (NSCs) and could be eliminated by flocculation at 500 mg/L polyaluminium chloride and 50 mg/L anionic polyacrylamide. Active carbon was very effective for decoloration of flocculation-treated PHL, but showed limited absorption selectivity toward NSCs. Lignin, the dominant component of NSCs, is characterized with phenolic hydrogen groups. Phenolic lignin could be easily captured by anion exchange resin with 80% removal. The proposed process showed great industrial potential because of the high value saccharides, but also low molecular phenolic lignin.
Lignocellulosic feedstock conversion, inhibitor detoxification and cellulosic hydrolysis – a review
The current review is an attempt to cover various pre-treatment strategies such as physical, chemical, organosolve and biological pre-treatment in order to change the crystallinity of lignocellulosic biomass along with methods and strategies for inhibitor detoxification for improving the cellulose hydrolysis and fermentation. The presence of lignin in lignocellulosic biomass is the biggest hurdle and therefore a judicial pre-treatment selection technique is important, based on lignocellulosic mass composition analysis for improving overall saccharification. The production of inhibitors during pre-treatment is another cause of low saccharification owing to deactivation of cellulase enzyme. In this review a comprehensive discussion has been made of the impact of various pre-treatment strategies on overall hydrolysis and saccharification in view of the varied composition of lignocellulosic biomass. Various detoxification approaches have also been discussed, along with the economical bioprocessing issue, and their advantages and disadvantages. Bio refinery approaches have been important in this regard to make bioethanol production more economical
Biotechnology progress
This study demonstrates sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) for robust bioconversion of hardwoods. With only about 4% sodium bisulfite charge on aspen and 30-min pretreatment at temperature 180 degrees C, SPORL can achieve near-complete cellulose conversion to glucose in a wide range of pretreatment liquor of pH 2.0-4.5 in only about 10 h enzymatic hydrolysis. The enzyme loading was about 20 FPU cellulase plus 30 CBU beta-glucosidase per gram of cellulose. The production of fermentation inhibitor furfural was less than 20 mg/g of aspen wood at pH 4.5. With pH 4.5, SPORL avoided reactor corrosion problem and eliminated the need for substrate neutralization prior to enzymatic hydrolysis. Similar results were obtained from maple and eucalyptus.
Enhancement in enzymatic hydrolysis by mechanical refining for pretreated hardwood lignocellulosics
Bioresource Technology, 2013
Mechanical refining improved the enzymatic hydrolysis sugar recovery. The increase in sugar recovery correlated with the water retention value. Mechanical refiners with different mechanisms affected the biomass digestibility differently. A maximum in absolute enzymatic hydrolysis improvement due to refining was observed. The maximum occurred at conditions that produced intermediate hydrolysis conversions.
Enzymatic pulping of lignocellulosic biomass
With advances in biotechnology, enzyme technologies have been increasingly applied to pretreat lignocellulosic biomass before the production of pulp. There are several driving forces, which include decreasing environmental impact from the traditional pulp and paper manufacturing processes, decreasing the overall production cost, and improving the product properties. This paper reviews recent developments in the area, particularly, related to the production of bleached pulp, dissolving pulp and pulp refining. This paper focuses on the mechanism and influencing factors of enzymatically assisted pulp bleaching to reduce adsorbable organic halide (AOX) formation and dissolving pulp production and focuses on saving energy in pulp refining. The enzyme technology is in the marketplace of the pulp and paper processes, and it is expected to gain more importance in the future.