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[en] Highlights: • Two processing routes using green solvents were used to fractionate Miscanthus. • Purified cellulose fibres were analysed using physicochemical & statistical tools. • Different processes generated fibres with different physicochemical properties, which impacted in downstream processing. - Abstract: Using a biorefinery approach, biomass polymers such as lignin and carbohydrates can be selectively purified from lignocellulosic feedstocks with the aim of generating not only lignocellulosic bioethanol but also high value bio-based compounds. Furthermore, the efficient use of the entire biomass can increase overall feedstock value and significantly contribute to process cost-effectiveness. Therefore, the aim of this work was to fractionate the main compounds of the energy crop Miscanthus x giganteus (MxG) using ‘green’ solvents in order to obtain cellulose-enriched fibres as well as non-toxic streams rich in hemicellulose and lignin. Two processing routes were compared: a direct 1-step modified organosolv method for simultaneous lignin and hemicellulose removal; and a 3-step sequential process using subcritical water extraction for recovery of first extractives then hemicellulose, followed by modified organosolv lignin extraction. Both methods successfully generated cellulose-enriched fibres; from a complex mixture of compounds present in MxG, it was possible to obtain fibres comprising 78% cellulose without the use of commonly-applied toxic solvents that can potentially limit end uses for processed biomass and/or need additional neutralization steps. Fibres generated by the direct and sequential processes were very similar in composition; however, physicochemical analysis of the fibres using scanning electron microscopy, Fourier-transform infrared spectroscopy and principal component analysis confirmed structural differences resulting from the two processing routes, which were demonstrated to have an impact on downstream processing.
[en] The structure of the lignocellulosic materials and the chemical composition of their main constitutive polymers, cellulose, hemicelluloses and lignin are described. The most promising transformation processes according to the type of biomass considered: hardwood, softwood an herbaceous and the perspectives of biotechnological processes for bio pulping, bio bleaching and effluents decolorisation in the paper pulp industry are also discussed. (Author) 7 refs
[en] Highlights: • Predictive kinetic reaction model applicable to any lignocellulosic feedstock. • Calculates pyrolysis yields and product composition as function of reactor conditions. • Detailed modelling of product composition (33 model compounds for the bio-oil). • Good agreement with literature regarding yield curves and product composition. • Successful validation with pyrolysis experiments in bench scale fast pyrolysis rig. - Abstract: This paper presents a novel kinetic reaction model for biomass pyrolysis processes. The model is based on the three main building blocks of lignocellulosic biomass, cellulose, hemicellulose and lignin and can be readily implemented in Aspen Plus and easily adapted to other process simulation software packages. It uses a set of 149 individual reactions that represent the volatilization, decomposition and recomposition processes of biomass pyrolysis. A linear regression algorithm accounts for the secondary pyrolysis reactions, thus allowing the calculation of slow and intermediate pyrolysis reactions. The bio-oil is modelled with a high level of detail, using up to 33 model compounds, which allows for a comprehensive estimation of the properties of the bio-oil and the prediction of further upgrading reactions. After showing good agreement with existing literature data, our own pyrolysis experiments are reported for validating the reaction model. A beech wood feedstock is subjected to pyrolysis under well-defined conditions at different temperatures and the product yields and compositions are determined. Reproducing the experimental pyrolysis runs with the simulation model, a high coincidence is found for the obtained fraction yields (bio-oil, char and gas), for the water content and for the elemental composition of the pyrolysis products. The kinetic reaction model is found to be suited for predicting pyrolysis yields and product composition for any lignocellulosic biomass feedstock under typical pyrolysis conditions without the need for experimental data.
[en] This study presents a methodology to estimate the leaf biochemical compounds specific absorption coefficients and to use them to predict leaf biochemistry. A wide range of leaves was collected including variations in species and leaf status. All the leaves were dried out. The biochemical composition was measured using classical wet chemistry techniques to determine lignin, cellulose, hemicellulose, starch, and protein contents. Concurrently, leaf reflectance and transmittance were measured with a high spectral resolution spectrophotometer in the 800–2500 nm range with approximately 1 nm spectral resolution and sampling interval. In addition, infinite reflectance achieved by stacking leaves was also measured. The PROSPECT leaf optical properties model was first inverted over a selection of wavebands in the 800–2400 nm domain to provide estimates of the scattering characteristics using leaf reflectance, transmittance, and infinite reflectance data. Then, the model was inverted again over all the wavelengths to estimate the global absorption coefficient, using the previously estimated scattering properties. The global absorption coefficient was eventually explained using the measured biochemical composition by fitting the corresponding specific absorption coefficients after substraction of the measured contribution of the residual structural water absorption. Results show that the derived specific absorption coefficients are quite robustly estimated. Further, they are in good agreement with known absorption features of each biochemical compound. The average contribution of each biochemical compound to leaf absorption feature is also evaluated. Sugar, cellulose, and hemicellulose are the main compounds that contribute to absorption. Results demonstrate the possibility of modeling leaf optical properties of dry leaves with explicit description of leaf biochemistry. Estimates of the detailed biochemical composition obtained by model inversion over the 1300–2400 nm spectral domain show poor predictive performances. In particular, the protein content is very poorly retrieved. The retrieval performances of several combinations of the biochemical compounds are investigated. Results show that the total amount of dry matter per unit leaf area is the only variable to be accurately retrieved. Possible improvements of these results are discussed. (author)
[en] Highlights: • Combustion behaviours of single biomass particles investigated with a visual DTF. • Flame contour size and luminous intensity deduced from captured high-speed videos. • Volatile and char combustion phases seen for all 3 kinds of biomass particles. • 2 peaks seen in volatiles correspond to devolatilisation of hemicellulose & cellulose. • Ratio between char burnout time and VM combustion time increases with FC:VM ratio. - Abstract: Combustion behaviours of single particles (125–150 μm) of eucalyptus, pine and olive residue were investigated by means of a transparent visual drop-tube furnace, electrically heated to 1073 K, and a high-speed camera coupling with a long distance microscope. All three types of biomass samples were found to have two evident combustion phases, i.e., volatile combustion in an envelope flame and subsequent char combustion with high luminance. Yet, due to differences in chemical compositions and properties, their combustion behaviours were also seen somewhat discrepant. The volatile flame of the olive residue was fainter than that of pine and eucalyptus due to its high ash mass fraction. During the char combustion phase, fragmentation took place for most pine particles but only for a few particles of olive residue and eucalyptus. For all three types of biomass samples, the flame size and the average luminous intensity profiles were deduced from the captured combustion video images whilst the combustion burnout times of the volatile matter and char were also calculated and estimated. There were two peak values clearly shown on the profiles of both the flame size and the average luminous intensity during the volatile combustion process of pine and eucalyptus particles, which, according to literature, could not be observed by optical pyrometry. The observed peaks correspond to the devolatilisation of hemicellulose and cellulose. The ratio between the estimated char burnout time and volatile combustion time increases quadratically with the fixed carbon to volatile matter mass ratio, confirming char combustion is much slower than volatile combustion.
[en] Biomass pretreatment aims at separating and providing easier access to the main biomass components (cellulose, hemicellulose and lignin), eventually removing lignin, preserving the hemicellulose, reducing the cellulose crystallinity and increasing the porosity of the material. Pretreatment is an essential step towards the development and industrialization of efficient 2nd generation lignocellulosic ethanol processes. The present work reviewed the main options available in pretreatment. Autohydrolysis and steam explosion were then selected for further investigation. Experimental work was carried out on batch scale reactors, using Miscanthus as biomass feedstock: the effects on sugar solubilization and degradation products generation have been examined for each of these two pretreatment systems. A new process using only water and steam as reacting media was then developed, experimentally tested, and results compared to those achieved by the autohydrolysis and steam explosion processes. Products obtained with the new pretreatment contained a lower amount of usual fermentation inhibitor compounds compared to that typically obtained in steam explosion. This result was achieved under operating conditions that at the same time allowed a good xylan yield, preventing degradation of hemicelluloses. The new pretreatment process was also able to act as an equalization step, as the solid material from the pretreatment phase had a similar composition even under different operating conditions. As regards the effect of pretreatment on enzymatic hydrolysis, the new process achieved yields similar to steam explosion on glucans: however, this was obtained reducing the formation of degradation products from sugars, mainly from C5 sugars. These results made the proposed pretreatment system suitable for further development and industrialization on pilot and industrial scale.
[en] Ligno-cellulosic biomass from different sources presents variable composition. The main aim of this work was to develop a method to predict the gas yields after flash pyrolysis (and tar cracking) at 950 deg. C in an Entrained Flow Reactor of any biomass from its composition in the three main components - cellulose, hemicellulose and lignin. For this approach to be successful, three conditions need to be met: (C1)Pyrolytic behaviour of celluloses from different biomasses is similar, as is hemicellulose and lignin behaviour. (C2)There is no interaction between the components. (C3)Extractives and ashes have no impact on the pyrolysis process. Two approaches were chosen to investigate the condition C1: (i)Celluloses, hemicelluloses and lignins of various sources were pyrolysed. Results show that hemicelluloses and lignins from different sources do not form the same quantities of gases. (ii)An attempt was made to identify the gas yields of 'theoretical components' that are able to predict flash pyrolytic behaviour of any biomass. Results tend to show that this is not possible. The condition C2 is investigated by comparing the gas yields of the components taken separately and the gas yields of mixes of the components. Two types of mixing were carried out: simple mixing and intimate mixing. Results show that interactions occur between the components during flash pyrolysis. The condition C3 was not investigated here; it can nevertheless be concluded that the behaviour of a biomass during flash pyrolysis at high temperature cannot be predicted from its composition in cellulose, hemicellulose and lignin
[en] Highlights: ► Multifunctional enzymes offer an interesting approach for biomass degradation. ► Size and conformation of separate constructs play a role in the effectiveness of chimeras. ► A connecting linker allows for maximal flexibility and increased thermostability. ► Genes with functional similarities are the best choice for fusion candidates. -- Abstract: The reduction of fossil fuels, coupled with its increase in price, has made the search for alternative energy resources more plausible. One of the topics gaining fast interest is the utilization of lignocellulose, the main component of plants. Its primary constituents, cellulose and hemicellulose, can be degraded by a series of enzymes present in microorganisms, into simple sugars, later used for bioethanol production. Thermophilic bacteria have proven to be an interesting source of enzymes required for hydrolysis since they can withstand high and denaturing temperatures, which are usually required for processes involving biomass degradation. However, the cost associated with the whole enzymatic process is staggering. A solution for cost effective and highly active production is through the construction of multifunctional enzyme complexes harboring the function of more than one enzyme needed for the hydrolysis process. There are various strategies for the degradation of complex biomass ranging from the regulation of the enzymes involved, to cellulosomes, and proteins harboring more than one enzymatic activity. In this review, the construction of multifunctional biomass degrading enzymes through end-to-end gene fusions, and its impact on production and activity by choosing the enzymes and linkers is assessed.
[en] Highlights: • The sugarcane bagasse is very recalcitrant against the action of cellulases. • Treatments are necessary for an effective hydrolysis on bagasse. • The residue from carrageenan processing can be hydrolyzed to glucose. • The residue from carrageenan processing have potential for the production of biofuels. - Abstract: Macroalgae and sugarcane biorefineries are designed to generate bioproducts for commercial use. Due to the high carbohydrate content of Kappaphycus alvarezii and sugarcane bagasse (SCB), biorefineries are aimed at generating such bioproducts as bioethanol, sucrose, carrageenan, and electricity production. Although there are several studies on SCB, the comparative study between residue carrageenan extraction and SCB has not yet been published. The samples were chemically characterized followed by structural, ultrastructural, and enzymatic hydrolysis analyzes. The content of protein in the wastes varied depending on the method used. Galactan (8.2%) and glucan (55.3%) were major polysaccharides in the residue carrageenan extraction, whereas in SCB, major polysaccharides were hemicellulose (25.2%) and glucan (38.2%). SCB was found to contain 24.5% of lignin, but the residue carrageenan extraction showed the presence of only 4.5% of insoluble aromatic compounds. ATR, NMR, and UV-Visible data on the residue carrageenan extraction revealed that the glucan fraction was similar to that in SCB. In contrast, the XRD analysis of SCB revealed a higher index of crystallinity than in the residue carrageenan extraction. The residue carrageenan extraction from the K. alvarezii does not show any type of recalcitrance against the enzymatic hydrolysis of cellulases, being hydrolyzed 100% in glucose. However, SCB showed a maximum conversion to glucose of 30%, requiring an additional pretreatment step. Thus, a biorefinery of K. alvarezii can be exploited not only to produce carrageenan but also to generate glucose for future bioenergy generation. An example would be the production of fourth generation bioethanol.
[en] Highlights: • Exogenous P increases Cd accumulation in the root cell wall. • P increases cell wall pectin and hemicellulose 1 content. • PME activity was enhanced by P application in the presence of Cd. - Abstract: Phosphorous (P) is an essential element that mediates various stresses in plants. In this study, the effects of P on polysaccharides in the root cell walls of two hydroponically cultivated mangrove seedlings (A. marina and K. obovata) that differ in Cd accumulation ability were examined in the context of Cd stress. The results showed that A. marina exhibited a higher degree of tolerance to Cd than K. obovata. In both mangrove seedlings, pectin and hemicellulose 1 increased significantly with increasing P levels, the effects of which were greater in A. marina under Cd stress. In addition, cell wall pectin methylesterase (PME) activity was markedly increased in the presence of Cd and P compared with Cd alone. These effects were more pronounced in A. marina than in K. obovata. Taken together, the results of this study provide further insight into the mechanisms of P-mediated alleviation of Cd stress in mangrove seedlings.