Biorefinery Scheme Research Articles

Total utilization of lignin and carbohydrates in Eucalyptus grandis: an integrated biorefinery strategy towards phenolics, levulinic acid, and furfural

BackgroundLignocellulosic biomass, which is composed of cellulose, hemicellulose and lignin, represents the most abundant renewable carbon source with significant potential for the production of sustainable chemicals and fuels. Current biorefineries focus on cellulose and hemicellulose valorization, whereas lignin is treated as a waste product and is burned to supply energy to the biorefineries. The depolymerization of lignin into well-defined mono-aromatic chemicals suitable for downstream processing is recognized increasingly as an important starting point for lignin valorization. In this study, conversion of all three components of Eucalyptus grandis into the corresponding monomeric chemicals was investigated using solid and acidic catalyst in sequence.ResultsLignin was depolymerized into well-defined monomeric phenols in the first step using a Pd/C catalyst. The maximum phenolic monomers yield of 49.8 wt% was achieved at 240 °C for 4 h under 30 atm H2. In the monomers, 4-propanol guaiacol (12.9 wt%) and 4-propanol syringol (31.9 wt%) were identified as the two major phenolic products with 90% selectivity. High retention of cellulose and hemicellulose pulp was also obtained, which was treated with FeCl3 catalyst to attain 5-hydroxymethylfurfural, levulinic acid and furfural simultaneously. The optimal reaction condition for the co-conversion of hemicellulose and cellulose was established as 190 °C and 100 min, from which furfural and levulinic acid were obtained in 55.9% and 73.6% yields, respectively. Ultimately, 54% of Eucalyptus sawdust can be converted into well-defined chemicals under such an integrated biorefinery method.ConclusionsA two-step process (reductive catalytic fractionation followed by FeCl3 catalysis) allows the fractionation of all the three biopolymers (cellulose, hemicellulose, and lignin) in Eucalyptus biomass, which provides a promising strategy to make high-value chemicals from sustainable biomass.

Highly efficient and selectivefractionation strategy for lignocellulosic biomass with recyclable dioxane/ethylene glycol binary solvent

Poplar is among the short-rotation and dedicated energy crops which serve as lignocellulosic feedstock for future bio-refinery. In this study, a promising bio-refinery strategy was developed to efficiently fractionate poplar wood into its three components with dioxane/ethylene glycol as reaction medium and H2SO4 as catalyst under microwave irradiation. Up to 94.5% lignin and 95.1% hemicellulose can be selectively separated from raw poplar while achieve 78.5% cellulose retention at 120 °C with 1.5wt% H2SO4 for 10min. The characterization of recovered lignin implied that it has relatively low molecular weight as well as less condensed structures, which enable its easy dissolving in common solvents and facilitate its further applications. In addition, pure cellulose comparable to commercial α-cellulose can be obtained by slightly increasing fractionation time and temperature. The high quality fractions, easy-handle operation process and the possible solvent recovery entitle the proposed fractionation approach have great potential to scale up for industrial implementation.

System-Level Analysis of Lignin Valorization in Lignocellulosic Biorefineries.

SummaryWe study the economics and energy efficiency of biorefineries employing lignin valorization. We use superstructure-based process synthesis to study different configurations under different types of constraints. Using optimization, we examine the impact of various parameters for lignin valorization such as bioproduct selling price, production cost, conversion coefficient, and energy requirement. The results show that the optimal strategy leading to a minimum ethanol selling price (MESP) of $3.44/GGE does not include lignin valorization. Results indicate that under certain scenarios, the optimal biorefinery strategies with lignin valorization tend to be energy deficient, and thus the optimal pretreatment technology may switch from γ-valerolactone-based deconstruction to ammonia fiber expansion. Further analysis is performed to study how improvements in combinations of selected parameters can lead to lower cost for a thermal-neural biorefinery.

Constructing ethanol-derived bioactive extracts using the brown seaweed Zonaria tournefortii (J.V.Lamouroux) Montagne performed with Timatic extractor by means of response surface methodology (RSM)

Understanding the biochemical and antioxidant composition and capacity of a target biomass is the first step to its selectivity as functional food which can enhance the ability to promote health by reducing the risk of chronic diseases. The main purpose of this work was to employ response surface methodology (RSM) to determine the effect of the independent variables, % of ethanol (50–96%), time of sonication (0–20 min), and number of extraction cycles (6–18 cycles) in the primary extract of brown seaweed Zonaria tournefortii, studying the yield variation of some bioactive compounds, assessing the potential of these bioextracts to integrate as a natural additives or supplements in the functional food industry. The extractions were performed employing “Green Chemistry” techniques executed with the Timatic extractor, which applied pressurized ethanol solution at a maximum pressure of 8.5 bar through milled dehydrated biomass in the extraction vessel. Several parameters were assessed in the primary bioactive extract which included extract yield (11.56–28.49 g (100 g)−1 dw), total chlorophyll content (0.14–1.42 g (100 g)−1 dw), total carotenoid content (0.35–0.80 g (100 g)−1 dw), total fucoxanthin content (0.04–0.13 g (100 g)−1 dw), total phenolic content (3.58–5.84 g (100 g)−1 dw), total flavonoid content (0.22–4.70 g (100 g)−1 dw), DPPH (56.05–76.45%), and reducing activity (3.83–6.04 g (100 g)−1 dw). A second objective was to determine the suitability of the residue for subsequent extraction of valuable compounds such as fucoidan (4.87 to 6.59 g (100 g)−1 dw) and cellulose (18.88 to 20.27 g (100 g)−1 dw), implementing the first step to a biorefinery strategy, using a cascade approach.

Lignocellulosic Biomass Fractionation by Mineral Acids and Resulting Extract Purification Processes: Conditions, Yields, and Purities.

Fractionation of lignocellulose is a fundamental step in the valorization of cellulose, hemicelluloses, and lignin to produce various sustainable fuels and chemicals. Mineral acid fractionation is one of the most applied process and leads to the solubilization and hydrolysis of cellulose and hemicelluloses, whereas most of the lignin remains insoluble and can be separated from the extract. The obtained monomeric sugars in the acid extract are in solution with salts, sugar degradation products, and phenolic molecules. Downstream processing is required to purify the sugars and further valorize them into fuels or chemicals with the use of chemical or biochemical reactions. This purification step also allows the recycling of the mineral acid and the valorization of the sugar degradation products and the co-extracted phenolic molecules, adding value to the whole biorefinery scheme. Many purification techniques have been studied, providing several options in terms of yields, purities, and cost of the process. This review presents the conditions used for the mineral acid fractionation step and a wide variety of purification techniques applied on the obtained hydrolysate, with a focus on the associated yields and purities. Values from the literature are expressed in a standard way in order to simplify comparison between the different processes.

Sequential Fractionation of Lignocellulosic Biomass Using CO2‐Assisted Hydrolysis Combined with γ‐Valerolactone Treatment

A biomass biorefinery strategy for the selective fractionation of poplar into its three main compositions (hemicellulose sugars, lignin, and high‐purity cellulose) with a two‐step process is developed. The first step consists of the selective hydrolysis of hemicellulose at mild conditions in a CO2/H2O system. This leads to various hemicellulose sugars and other intermediates in the water‐soluble fraction, with more than 87.90% of the hemicellulose being extracted from the original poplar (180 °C, 2.0 MPa CO2, 10 min). The pretreated sample is subsequently used for extracting lignin in a γ‐valerolactone (GVL)/H2O with acid catalysts for the next step. Meanwhile, four acid catalysts, including sulfuric acid and solid heteropoly acids (phosphomolybdic acid, silicotungstic acid, and phosphotungstic acid), are studied for the selective delignification in the GVL/H2O system, resulting in more than 91.35% of the original lignin being removed in the cellulose‐rich substrates (140 °C, 30 mM silicotungstic acid, 3 h). Overall, the biorefinery approach fractions the poplar wood into three primary components: 1) various oligosaccharides, monosaccharides, and other intermediates derived from hemicellulose; 2) cellulose‐rich substrate with a purity of cellulose as high as 90.76%, which has great potential as biochemicals or biomaterials; and 3) high‐purity and proportion lignin recovered from biomass.

Review: Bio-polyethylene from Wood Wastes

There is a global trend of substitution of fossil fuels for renewable energy sources, which are preferred by reasons including sustainability, reduction of greenhouse gases that contribute to climate change, regional and social systems advancement, among others. This review is part of the studies carried out on the integral use of wood industrial wastes due to its low costs and high availability. A possible high-value product is ethylene, obtained by catalytic dehydration of second-generation bioethanol from lignocellulosic materials and which can be an effective alternative for the production of polymers such as polyethylene (PE), which is conventionally obtained from petroleum. Biobased polyethylene or biopolyethylene (BioPE) may potentially contribute to close a pine biorefinery scheme to obtain high-value products, using processes of low pollution and contributing to the global environmental balance. The process involves the following stages: pretreatment, enzymatic saccharification, fermentation, dehydration, and polymerization. This review includes the different processes for second generation (2G) bioethylene productions from pine wastes as an example and the technologies that can potentially be applied on an industrial scale for BioPE production, focusing on the catalytic dehydration of 2G bioethanol through the use of catalysts able to achieve high ethanol conversions and ethylene selectivity.

Integral exploitation from olive cake for energy production in a biorefinery scheme

This research aims to optimize the hydrothermal pretreatment based on previous studies, with the objective of extracting and determining value-added products from olive cake, and improve the energy solid properties. For this purpose, a hydrothermal pretreatment following of an autohydrolysis of the resulting solid were carried out in a biorefinery scheme.To the best of our knowledge this process has not been previously tested with olive cake by other authors. The conditions of the hydrothermal pretreatment were 30°C and 1h to prepare a suitable solid with mild conditions because polyphenols, water soluble extracts and tars precursors were eliminated. Sucrose was the value-added product with the best extraction 2.48% at this conditions. Therefore, resulting solids were subjected to an autohydrolysis to improve the value-added products extractions. The autohydrolysis was based on a design of experiments with temperatures of 120, 140, 160 and 180°C and time of 30, 60 and 90min to study the influence between the independent variables and the dependent variables (yield % and calorific value from each resulting solid and saccharides extractions from liquid extracted). The saccharides extracted were glucose, xylose, fructose, sucrose and glucose and xylose oligomers. Glucose and xylose oligomers contents were highest with 4g and 19.24g per 100g of solid respectively. The solid energy properties were improved because a solid with a calorific value of 5970kcal/kg was obtained. All experimental results were fitted to neural-fuzzy and polynomial model.

Consumption of sugars and inhibitors of softwood hemicellulose hydrolysates as carbon sources for polyhydroxybutyrate (PHB) production with Paraburkholderia sacchari IPT 101

The future industrial success of the compostable bio-polyesters known as polyhydroxyalkanoates, which includes polyhydroxybutyrate (PHB), depends mainly on their production using cheaper carbon sources than food-derived glucose. The existing pulp and paper infrastructure enables an alternative sugar supply in the form of wood hydrolysates. Softwood hemicellulose hydrolysates have a favourable sugar profile for fermentations and can be produced in such emerging integrated forest biorefineries. The processes can lead to varying amounts of inhibitors which can lead to the reduction or prevention of bacterial growth. A dilute acid pretreatment was used to produce a softwood hemicellulose hydrolysate containing the sugars mannose, xylose, glucose, galactose, and arabinose. To study the effects of increasing sugar diversity and inhibitor concentration, the softwood hydrolysate was mixed in varying proportions with a hardwood holocellulose hydrolysate obtained from the TMP-Bio process (a thermomechanical pulping-based process producing glucose and xylose). In fermentations with Paraburkholderia sacchari IPT 101, the sugars were depleted at different rates in the following order: glucose, mannose, xylose, galactose, and arabinose. All potential inhibitors except phenols were metabolized. The maximum cell dry weight reached 6.7 ± 0.1 g/L with 71 ± 5% PHB with hardwood holocellulose hydrolysate after 48 h. The analyses of the sugar and inhibitor consumption provided valuable information to validate approaches for the detoxification of softwood hemicellulose hydrolysates. Overall, the detoxification would allow PHB production in an integrated softwood biorefinery scheme.

Integrated biorefinery strategy for tofu wastewater biotransformation and biomass valorization with the filamentous microalga Tribonema minus

This study focused on the feasibility of using different concentrations of tofu wastewater (TW) as alternative media for Tribonema minus cultures to produce valuable biorefinery feedstock. T. minus grew mixotrophically in 100% TW with larger carbohydrate (30.99% of dry weight (DW)), protein (15.56% of DW) and chrysolaminarin (6.93% of DW) accumulations than that of in mBG-11 medium. The highest biomass concentration, 7.77 g/L, was achieved in 100% TW, and nutrient removal efficiencies of T. minus at this concentration ranged from 60.49% to 93.60%. Although smaller neutral lipid and palmitoleic acid amounts were detected in 100% TW, their productivities reached 133.77 and 67.19 mg/L/d, respectively, due to the largest biomass yield contribution, which were comparable to those in mBG-11 medium. These findings demonstrated that TW is a promising alternative medium, and an integrated TW biotransformation and biomass valorization process is proposed to achieve better economic performance and environmental sustainability.

Multicomponent emulsifiers from sunflower seeds

The increasing demand for new ingredients with high functionality can be compensated to some extent by an improved utilization of plant derived materials, like proteins. Abundant amounts of proteins exist in plants; however, the current biorefinery strategies are not suitable for their sturdy matrix and complex composition. Milder and simpler processes should be developed in order to avoid chemicals and conditions that either disregard useful ingredients or hinder the functionality of proteins. This review presents new approaches to how the availability of oilseed emulsifiers could be materialized. A key factor is an altered focus towards native multicomponent emulsifiers rather than preparations consisting of pure components.

Ultrasound-Assisted Extraction as a First Step in a Biorefinery Strategy for Valorisation of Extracted Olive Pomace

Currently, interest in finding new feedstock as sources of natural food antioxidants is growing. The extracted olive pomace (EOP), which is an agro-industrial residue from the olive pomace extracting industries, is generated yearly in big amounts, mainly in the Mediterranean countries. EOP was subjected to an ultrasound assisted extraction with ethanol-water mixtures. The effect of main parameters, such as ethanol concentration (30–70% v/v), ultrasound amplitude (20–80%), and extraction time (5–15 min), on the extraction of antioxidant compounds was evaluated according to a Box–Behnken experimental design. The antioxidant capacity of the resulting extracts was determined by measuring their content in total phenolic compounds (TPC) and flavonoids (TFC), as well as their antioxidant activity by DPPH, ferric reducing antioxidant power (FRAP), and ABTS assays. Considering the simultaneous maximization of these five responses, the optimal conditions were found to be 43.2% ethanol concentration, 70% amplitude, and 15 min. The ultrasound assisted extraction of EOP under these optimized conditions yielded an extract with a phenolic and flavonoid content (per gram of EOP) of 57.5 mg gallic acid equivalent (GAE) and 126.9 mg rutin equivalent (RE), respectively. Likewise, the values for DPPH, ABTS, and FRAP assay (per gram of EOP) of 56.7, 139.1, and 64.9 mg Trolox equivalent, respectively were determined in the optimized extract.

An eco-friendly biorefinery strategy for xylooligosaccharides production from sugarcane bagasse using cellulosic derived gluconic acid as efficient catalyst

A novel approach was proposed for the production of xylooligosaccharides by direct pre-hydrolysis using gluconic acid as catalyst. Maximum xylooligosaccharides (degree of polymerization 2–6) yield of 53.2% could be obtained in 60 min through 5% gluconic acid hydrolysis of sugarcane bagasse at 150 °C. Furthermore, the yield of glucose from solids following gluconic acid hydrolysis treatment was 86.2% after fed-batch enzymatic hydrolysis with 10% solids loading. Results indicated that gluconic acid pretreatment combined with enzymatic hydrolysis could be successfully applied to sugarcane bagasse substrate. Subsequently, glucose could be efficiently bio-oxidized to gluconic acid by Gluconobacter oxydans ATCC 621H with 93.1% yield, and sugarcane bagasse derived gluconic acid has been proved to be an effective catalyst for xylooligosaccharides production. In this study, xylooligosaccharides production from sugarcane bagasse by gluconic acid hydrolysis demonstrated a great potential with respect to the production of these probiotics around the world.

Production and characterization of lignin and cellulose fractions obtained from pretreated vine shoots by microwave assisted alkali treatment

This work deals with the optimization of the second stage of a biorefinery scheme to separate simultaneously cellulose and lignin from hydrothermally pre-treated vine shoots. For this, the suitability of the microwave-assisted alkaline delignification was assessed and optimized through a Box-Wilson experimental design. The optimum conditions (150 °C, 6 wt% NaOH, 30 min) allowed maximizing the lignin removal (82 wt%) and minimizing the loss of the cellulose (35 wt%) present in the pre-treated vine shoots. A thorough characterization of the two fractions obtained at optimum conditions was performed: the cellulose rich solid was analyzed by XRD and FTIR and the lignin was subjected to HPSEC, Py/GC–MS, 13C- and 1H NMR. This purposed second stage would allow performing an integral biorefinery with low energy requirements and environmentally friendly conditions. This approach aligns with the circular economy and the zero waste production philosophies, promoting the sustainable development.

Assessing the environmental sustainability of glucose from wheat as a fermentation feedstock

In recent years, the need to substitute fossil fuels with renewable biomass has been a key driver in the development of the biorefinery concept. One of the possible routes towards the development of bioproducts under this scheme is through a sugar intermediate. Sugars, such as glucose, can be produced through starch crops, for instance wheat. While there are many environmental assessment studies that consider sugar as a platform for biofuel production, the main focus is on the end product of the value chain (typically bioethanol), but not on sugars as the basic feedstock. Taking the bottom-up perspective as a roadmap, the assessment of technological, economic and environmental barriers in the biorefinery scheme must take into account the sustainability of sugar production with the aim of improving its current framework or finding novel technologies. This study investigates the environmental sustainability of wheat cultivation and grain processing in different European countries by applying the life cycle assessment (LCA) methodology with a cradle to gate approach. Moreover, 1 kg of glucose at the factory gate has been considered as a functional unit for reporting the environmental results. The chosen impact categories are climate change (CC), particular matter (PM), human toxicity (HT), freshwater eutrophication (FE), terrestrial eutrophication (TE), acidification (AC) and abiotic depletion (AD). Mass and economic allocations are evaluated as the processing of grain wheat generates different valuable by-products, namely wheat bran, gluten meal and gluten feed. The results show that agricultural activities play an important role in the environmental impacts, predominantly due to the production of agrochemicals and field emissions derived from fertilisation. In addition, the choice of allocation has a greater environmental influence (both positive or negative) on the by-products than the main product under investigation.

Conceptualization of a biorefinery for guishe revalorization

The extraction of fiber from Agave lechuguilla Torrey produces 15% of ixtle and 85% of guishe. Guishe is a pulpous by-product, without commercial value, composed of several phytochemicals which could be used as raw material for the synthesis of high added value products. The objective of this work was to conceptualize the integration of transformation processes into a biorefinery scheme, through a mass balance analysis, to identify opportunities for the revalorization of guishe. The processing of 1 ton of guishe is employed as a computing unit. Three fundamental transformation processes were considered: solvent extraction, thermochemical, and biological processing. The information was obtained from ixtle producers and implemented processes at lab scale by the authors. The obtained results show that the transformation of 1 ton of guishe allows producing: 260 kg of saponins, 104 kg of phytochemicals, 7.6 L of ethanol, 24 m3 of hydrogen, 15 kg of biochar and 32 m3 of methane. The evaluated technology is commercially available, and then it is feasible to implement the proposed alternatives at an industrial scale.

Multiproduct biorefinery from vine shoots: Bio-ethanol and lignin production

Vine shoots were hydrothermally processed and the effect of the different assayed severities on the subsequent enzymatic saccharification of the remaining solids was evaluated. The solid obtained at a severity of 4.47 showed the highest yield on glucose (74.01%) and therefore, it was used as the substrate for the obtaining of bio-ethanol through a SSF process. Under the evaluated conditions (LSR 10 g/g, 20 FPU/g and 10 IU/FPU) 13.3 g/L of bio-ethanol were produced (corresponding to 67.4% of ethanol conversion). Moreover, lignin has been extracted by an alkali delignification treatment from the vine shoots unprocessing and from the solids resulting from the stages of the proposed biorefinery scheme, which were the autohydrolysed vine shoots and the bio-ethanol residue. The isolated lignins were characterized by HPLC, total phenolic content, FTIR, HPSEC, Py-GC/MS and TGA and it was observed that the successive stages of processing to which the vine shoots were submitted provoked chemical and structural changes in the extracted lignins. The knowledge of the structural modifications that the lignin present in the vine shoots during the autohydrolysis and the SSF process could help determining at which stage of the bio-ethanol production would be suitable to recover the lignin for value-added applications.

Environmental and techno‐economic evaluation of β‐carotene production from Dunaliella salina. A biorefinery approach

AbstractIn this work, a solvent‐based extraction procedure and a procedure using supercritical CO2 to obtain β‐carotene from Dunaliella salina were compared from environmental and economic perspectives. Both processes were simulated using a biorefinery scheme in which β‐carotene was obtained and the waste biomass was used to produce energy. The results were used to carry out a life‐cycle assessment (LCA). The LCA results showed that a supercritical process was better in terms of energy consumption and greenhouse gas emissions. However, the low extraction yield of this technology makes it necessary to use large amounts of nutrients, whose production increases toxicity‐related impacts related to organic solvent extraction. This also affects the β‐carotene price, which is twofold higher in the case of a supercritical extraction process‐based biorefinery. The results therefore indicate that the potential benefits of the supercritical process in terms of environmental issues do not balance the drawbacks related to its low extraction yield. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Optimization of Laccase/Mediator System (LMS) Stage Applied in Fractionation of Eucalyptus globulus.

In a biorefinery framework, a laccase/mediator system treatment following autohydrolysis was carried out for eucalyptus wood prior to soda-anthraquinone pulping. The enzymatic and autohydrolysis conditions, with a view to maximizing the extraction of hemicelluloses while preserving the integrity of glucan, were optimized. Secondly, pulping of solid phase from Eucalyptus globulus wood autohydrolysis and the enzymatic process was carried out and compared with a conventional soda-anthraquinone (AQ) pulping process. The prehydrolysis and enzymatic delignification of the raw material prior to the delignification with soda- Anthraquinone (AQ) results in paper sheets with a lower kappa number and brightness and strength properties close to conventional soda-AQ paper and a liquid fraction rich in hemicellulose compounds that can be used in additional ways. The advantage of this biorefinery scheme is that it requires a lower concentration of chemical reagents, and lower operating times and temperature in the alkaline delignification stage, which represents an economic and environmental improvement over the conventional process.

Biorefinery processes for the valorization of Miscanthus polysaccharides: from constituent sugars to platform chemicals

A biorefinery scheme was proposed for manufacturing platform chemicals (furfural, denoted F, and 5-hydroxymethylfurfural, denoted HMF) from Miscanthus polysaccharides (including hemicelluloses and cellulose). The feedstock was first subjected to hydrothermal processing, which caused an extensive hemicellulose solubilization, yielding solids enriched in cellulose and aqueous solutions rich in saccharides. The acidic processing of the aqueous solutions in the presence of methyl isobutyl ketone (MIBK), which acted as an extracting agent, led to the formation and the in situ separation of F from pentoses at high molar yields (up to 78%). Moreover, HMF and levulinic acid were obtained from the hexoses released from the feedstock.The cellulose-enriched solids from hydrothermal processing were used as a substrate for HMF manufacture, employing a combination of enzymatic and chemical treatments. The enzymatic hydrolysis yielded glucose (in concentration up to 59 g /L), which was enzymatically isomerized into fructose in the presence of sodium tetraborate at yields up to 80%. Acidic treatments of the resulting reaction media at low temperature (134 °C) in the presence of H2SO4 enabled the formation of HMF at yields about 49%. Under the assayed conditions, glucose remained practically unaltered, facilitating its reutilization in the isomerization stage.