Biorefinery Scheme Research Articles

Optimized Production of Xylooligosaccharides from Poplar: A Biorefinery Strategy with Sequential Acetic Acid/Sodium Acetate Hydrolysis Followed by Xylanase Hydrolysis

Optimized Production of Xylooligosaccharides from Poplar: A Biorefinery Strategy with Sequential Acetic Acid/Sodium Acetate Hydrolysis Followed by Xylanase Hydrolysis

Evaluation of sustainable technologies for the processing of Sargassum muticum: cascade biorefinery schemes

Cascade biorefinery schemes using sustainable technologies were proposed for a complete valorization of the invasive macroalgae Sargassum muticum.

Enhanced medium chain length-polyhydroxyalkanoate production by co-fermentation of lignin and holocellulose hydrolysates

Biological lignin and holocellulose conversion to medium chain length-polyhydroxyalkanoates (mcl-PHA) as an excellent platform for bioplastics production and attractive alternative for current biorefinery schemes.

Hydrothermal treatment and biorefinery of sewage sludge for waste reduction and production of fungal hyphae fibers and volatile fatty acids

Sewage sludge poses a serious environmental problem for large cities, and large amounts of materials in sludge, including organics, should be recovered rather than wasted. To achieve both sludge reduction and organic resource recovery, this study developed a new biorefinery technology that includes the hydrothermal treatment of sludge followed by fungal fermentation to form hyphae fibers and acidogenic fermentation to produce volatile fatty acids (VFAs). Hydrothermal treatment at 160 °C or 180 °C allows solubilization of approximately 40% of solid organics in sludge into the supernatant, resulting in significant sludge reduction and dewaterability improvement. The fermentation of the fungus Aspergillus niger converted waste organics in the hydrolyzed sludge liquor, with a chemical oxygen demand (COD) concentration of around 15,000 mg/L, into hyphae fibers, resulting in fungal biomass production of more than 1.7 g/L. After the recovery of hyphae fibers, the residual sludge liquor was further fermented to produce VFAs to a concentration of about 2500 mg COD/L. The genera Petrimonas, Arcobacter, and Aminobacterium played important roles in acidogenic fermentation. The stepped biorefinery strategy can transform approximately 35% of waste organics in the hydrothermal sludge liquor into valuable fibrous materials and VFAs for effective resource recovery.

Highly efficient fractionation of corn stover into lignin monomers and cellulose-rich pulp over H2WO4

In this work, we investigated the fractionation of raw biomass based on a “lignin-first” biorefinery strategy that enables the fractionation of corn stover into a stable lignin oil and a cellulose-rich pulp. Lignin fraction was completely disassembled into monomers with a yield of 25.1 wt% in methanol with a H2WO4 catalyst at 200 °C for 6 h. Higher temperature (≥220 °C) and longer reaction time (≥6 h) were in favor of higher delignification and hemicellulose removal, but led to lower cellulose retention and lignin monomer yield. Particle size of corn stover has minor impact on the delignification but significant for hemicellulose removal. A two-step mechanism is proposed for the fractionation of corn stover, in which ether and ester bonds between lignin and hemicellulose cleave to form oligomers through methanol solvolysis first, while the depolymerization of lignin oligomers to methyl hydroxycinnamates, e.g. methyl p-coumarate and methyl ferulate, as the major products happens in the catalytic steps.

Avocado-Derived Biomass as a Source of Bioenergy and Bioproducts

The avocado (Persea americana Mill.) is a tree native to Mexico and Guatemala. Avocado consumption, fresh or in the form of processed products, is growing everywhere and it has caused a large number of countries to invest heavily in avocado production. The industrialization of avocado gives as a result a huge amount of waste, not only the peel and stone but also that waste generated by the pruning practices and oil extraction. These biomasses could be converted into raw materials to obtain different types of co-products, but this implies changes in the use of these resources, the design of efficient production systems, and integration to take full advantage of them, e.g., by developing biorefinery models. Therefore, this review firstly gives a snapshot of those residues generated in the avocado industry and provides their chemical composition. Secondly, this review presents updated information about the valorization ways of avocado-derived biomass to obtain bioenergy, biofuels, and other marketable products (starch, protein, phenolic compounds, and biosorbents, among others) using a single process or integrated processes within a biorefinery context. Green technologies to obtain these products are also covered, e.g., based on the application of microwaves, ultrasound, supercritical fluids, etc. As a conclusion, there is a variety of ways to valorize avocado waste in single processes, but it would be promising to develop biorefinery schemes. This would enable the avocado sector to move towards the zero-waste principle.

Techno-economic analysis of Scenedesmus dimorphus microalgae biorefinery scenarios for biodiesel production and glycerol valorization

In this work five biorefinery scenarios are proposed for the production of five different target products. Two of these scenarios included biodiesel production from Scenedesmus dimorphus microalgae biomass and glycerol valorization through bioconversion into dihydroxyacetone (DHA) with the bacteria Gluconobacter oxydans. Experimental data of microalgae biomass composition were used as inputs to simulate reactive distillation column (RD) and continuously stirred tank reactor (CSTR) for microalgae oil transesterification stage. Optimum methanol/microalgae oil molar feed ratio, catalyst mass and reflux ratio were determined from simulated conditions with the Aspen Plus® V.10.0 Software. The biorefinery with the best economic performance integrated RD and glycerol valorization processes and achieved an internal rate of return (IRR) of 19.8%. The results showed that the combined use of reactive distillation (RD) with the biological oxidation of glycerol into DHA allows economically feasible biorefinery schemes using Scenedesmus dimorphus microalgae biomass as a feedstock.

Identification of environmental aspects of citrus waste valorization into D-limonene from a biorefinery approach

Citrus waste (CW) consists mainly of peels and pressed pulp (seeds and segment membranes), which represent approximately 50% of the fruit weight. In the framework of bioeconomy, this type of waste could serve as a valuable raw material for the manufacture of biofuels and other commodities. Specifically, CW comprises high levels of pectin, cellulose, hemicellulose and soluble sugars, and to lesser extent essential oils. d-limonene is a terpenic compound and main component of essential oils in CW. In the present study, alternative and low environmental impact technologies for the valorization of CW are evaluated in the framework of a biorefinery strategy. Although d-limonene is the target product, a “closing the loop” strategy has been incorporated obtaining biogas and digestate as co-products from the residual side-streams. Plant-wide simulations are performed according to four different scenarios (Scenario I to Scenario IV) comprising four sections: pre-treatment, extraction, purification and anaerobic digestion. The main differences between the scenarios correspond to the extraction (hydrodistillation, cold pressing and solvent extraction) and purification stages. Scenarios III and IV use ethanol and hexane, respectively, as extractive agents. The results show that Scenario I has the worst environmental profile, while Scenario II has the best profile of all the scenarios analysed. In addition, purification stage is the main responsible for the highest environmental burdens in scenarios I, II and IV due to the energy required. In Scenario II, pre-treatment and extraction steps are identified as hotspots, due to the high electricity requirements. There is therefore still room for improvement, and future research should focus on optimising the purification stages to reduce the impacts of those scenarios with poorer environmental profiles.

A biorefinery for the valorization of marigold (Calendula officinalis) residues to produce biogas and phenolic compounds

Marigold (Calendula officinalis) market is focused on the extraction of compounds from the flower for homeopathic applications. However, most of the body plant is left as waste for final disposition. This work aims to show an integral valorization of leaves and stem of marigold to produce biogas and phenolic compounds such as vanillin and vanillic acid in a biorefinery scheme. An alkaline pretreatment was carried out to obtain black liquor and to favor the digestibility of the solid residue. The black liquor was oxidized in a high-pressure reactor, reaching experimental yields of 5.09% and 1.16% (based on lignin) for vanillin and vanillic acid, respectively. The remaining solid fraction was fermented through anaerobic digestion, achieving biogas productivity of 1621.3 mL/g of volatile solids. Afterward, these experimental results were used as input parameters to simulate and analyze a potential biorefinery. It was demonstrated that the anaerobic digestion stage affects up to 59% of the capital costs and that the positive economic gains were achieved at flow rates greater than 6.64 ton/h.

Improving revenue from lignocellulosic biofuels: An integrated strategy for coproducing liquid transportation fuels and high value-added chemicals

In conventional biomass-to-biofuel production processes, cellulose and hemicellulose are converted only to biofuels. However, to improve the economics of the process, it is desirable that some fractions of biomass be produced as fuels and other fractions as chemicals. This coproduction of fuels and chemicals also enables a flexible response to the market conditions of bioproducts, rather than producing only biofuels or biochemicals. Moreover, the use of all fractions, not only cellulose and hemicellulose but also lignin, improves the economics of the process. We propose a biorefinery strategy for the coproduction of liquid hydrocarbon fuels and chemicals from lignocellulosic biomass. In this study, all three primary components of biomass were converted into high-value products that can be commercialized: (1) cellulose, which is converted into butene oligomers (BO) for transportation fuels, (2) hemicellulose, which is converted into 1,5-pentanediol (1,5-PDO) that can be used as polyester and polyurethane components, and (3) lignin, which is converted into carbon products, such as carbon fibers or battery anodes. By maximizing the biomass utilization up to 47.8% from biomass to valuable products, the economic viability of the proposed process can be increased. Technoeconomic analysis shows that the minimum selling price of BO is $4.21 per gallon of gasoline equivalent in the integrated strategy, indicating that it is a promising alternative to current biofuel production approaches.

Oxygen reduction catalyst element, method of its production, and uses thereof

Non-isothermal autohydrolysis, an environmentally friendly pretreatment, was employed for the production of second generation bioethanol from fast-growing Paulownia wood, comparing two biorefinery strategies: (i) one-stage autohydrolysis pretreatment, and (ii) sequential two-stage autohydrolysis pretreatment. The first strategy allowed to either recover high amounts of hemicellulosic-derived compounds in the liquid phase (at lower severities) or to achieve high enzymatic susceptibility of the cellulose in the solid phase (at higher severities). Solid phase from lower severities pretreatments (optimal for the recovery of hemicellulosic compounds) achieved glucan to glucose conversions of 38.6–72.2% in the enzymatic hydrolysis assays. In this context, conditions for the obtainment of a liquor enriched in hemicelluloses and a highly enzymatically susceptible solid are not compatible. Therefore, the employment of the second strategy (sequential pretreatments in two stages) allowed to recover up to 85% of initial xylan as xylooligosaccharides and xylose in autohydrolysis liquor from first stage of autohydrolysis (at severity, S01 = 4.08) and enhance the enzymatic susceptibility of the solid phase to a glucan to glucose conversion close to 100% with the second stage of autohydrolysis (S01 = 4.08, S02 = 3.76, with a global severity of S0G = 4.25). Fermentation experiments confirmed the advantages of the sequential two-stage autohydrolysis (with a glucan to ethanol conversion close to 100% and high volumetric productivity). Finally, an overall mass balance and energy analysis were carried out, reflecting a suitable fractionation of Paulownia wood that would accomplish an energy recovery of 97.5%.

Sequential two-stage autohydrolysis biorefinery for the production of bioethanol from fast-growing Paulownia biomass

Non-isothermal autohydrolysis, an environmentally friendly pretreatment, was employed for the production of second generation bioethanol from fast-growing Paulownia wood, comparing two biorefinery strategies: (i) one-stage autohydrolysis pretreatment, and (ii) sequential two-stage autohydrolysis pretreatment. The first strategy allowed to either recover high amounts of hemicellulosic-derived compounds in the liquid phase (at lower severities) or to achieve high enzymatic susceptibility of the cellulose in the solid phase (at higher severities). Solid phase from lower severities pretreatments (optimal for the recovery of hemicellulosic compounds) achieved glucan to glucose conversions of 38.6–72.2% in the enzymatic hydrolysis assays. In this context, conditions for the obtainment of a liquor enriched in hemicelluloses and a highly enzymatically susceptible solid are not compatible. Therefore, the employment of the second strategy (sequential pretreatments in two stages) allowed to recover up to 85% of initial xylan as xylooligosaccharides and xylose in autohydrolysis liquor from first stage of autohydrolysis (at severity, S01 = 4.08) and enhance the enzymatic susceptibility of the solid phase to a glucan to glucose conversion close to 100% with the second stage of autohydrolysis (S01 = 4.08, S02 = 3.76, with a global severity of S0G = 4.25). Fermentation experiments confirmed the advantages of the sequential two-stage autohydrolysis (with a glucan to ethanol conversion close to 100% and high volumetric productivity). Finally, an overall mass balance and energy analysis were carried out, reflecting a suitable fractionation of Paulownia wood that would accomplish an energy recovery of 97.5%.

Hydrothermal treatments of walnut shells: A potential pretreatment for subsequent product obtaining

Walnuts are nowadays widely consumed. Since the edible part of walnuts does not account more than 50–60% of their total weight, the total amount of shells produced annually is huge. However, as walnut shells are part of lignocellulosic biomass, they could be valorised via a biorefinery approach in order to extract their diverse constituents. For this reason, the aim of this work was to valorise walnut shells by a biorefinery scheme. The latest involved multiple microwave assisted and conventional hydrothermal treatments for the subsequent valorisation of oligosaccharides. Then, an organosolv delignification of the solid that permitted the maximum oligosaccharide yield was performed, in order to isolate the lignin. Finally, it was treated for cellulose nanocrystal obtaining. The results showed, on the one hand, that the hydrothermal treatments leaded to xyloligossacharide-rich liquors (1–17 g/L). On the other hand, the organosolv delignification resulted into the extraction of a highly pure lignin (93.6%) and a weight average molecular weight of 7000 Da. Moreover, the solid from the delignification treatment was suitable for a successful nanocrystal production. The extracted fractions could be employed in many applications and could be considered renewable precursors for new materials and chemicals. Hence, the proposed biorefinery scheme would allow an integral valorisation of currently undervalued walnut shells.

Chemical characterization, bioactive and fuel properties of waste cork and phloem fractions from Quercus cerris L. bark

Waste biomass composed of cork-rich and phloem-rich granules obtained from the fractioning of Quercus cerris L. bark were characterized for bulk density, chemical composition, bio-active components, ash composition, and higher heating value.Bulk density of the fractions relate to their cork content and deceases with smaller particle size due to a cork enrichment in the finer particles. The bulk density may therefore be used as an indicator of suberin content of waste cork and phloem fractions. Waste cork fractions are rich sources of lipophilic and polar extracts while waste phloem fractions contain high amount of polar extracts. The polar extracts of both biomass fractions showed very high antioxidant capacities with IC50 values between 2.5 and 7.3 μg extract mL-1 for cork fractions and 5.8 and 11.7 μg extract mL-1 for phloem fractions.Higher heating values in waste cork fractions increase with decreasing particle size and ranged between 20 and 22 MJ kg-1. A biorefinery scheme was developed for the valorization of the waste cork and phloem fractions based on their physical, chemical, bioactive, and higher heating values.

Fermentation of organic wastes and CO2 + H2 off-gas by microbiotas provides short-chain fatty acids and ethanol for n-caproate production

• Caproate was produced in a two-stage process. • In the first stage SCFAs were produced from three complex substrates. • In the second stage CO 2 + H 2 promoted the production of ethanol. • Caproate was produced from SCFAs and ethanol previously accumulated. • A CO 2 -enriched atmosphere improved the caproate production up to 6 g/L. This study describes a two-stage process for the valorization of organic wastes and CO 2 /H 2 off-gas for the production of short-chain fatty acids (SCFAs) and ethanol, as precursors for n -caproate formation. Three complex organic wastes with previously identified acetogenic members were used to inoculate batch reactors: 1) fibers and 2) leachates from a bagasse fermentation process, and 3) an anaerobic granular sludge from a reactor treating brewery effluents. In the first stage, the reactors loaded with a CO 2 /H 2 [25:75, v/v] gas mixture produced SCFAs at similar concentrations between 4,274 and 5,381 mg/L. In this stage, fiber reactors had the highest H 2 consumption. In the second stage, reactors consumed all available H 2 and accumulated solvents as well as low concentrations of n -caproate. In particular, sludge reactors produced 3,528 mg/L of solvents with more than 50% ethanol content, and leachate reactors produced 617 mg/L of n -caproate. By the end of the second stage, in a CO 2 -enriched atmosphere, leachate reactors produced 6,157 mg/L of n -caproate at the expenses of the SCFAs and solvents. Fiber and leachate microbiotas shared autotrophic members and SCFA-elongating bacteria while sludge microbiota differed in composition. This study demonstrated that the use of CO 2 /H 2 off-gas shifted the composition of SCFAs to a mixture with ethanol which promoted its condensation into n -caproate. A CO 2 -enriched atmosphere improved significantly the final production of n -caproate. The results of this study can be used to integrate the n -caproate production, and possibly other medium-chain fatty acids, with biorefinery schemes in which SCFAs and CO 2 /H 2 off-gases are produced.

An optimization framework to identify key management strategies for improving biorefinery performance: a case study of winter barley production

AbstractThe selection of locations and practices for energy crops requires the economics to be planned and the carbon intensity of the fuel to be assessed. This study develops a framework for selecting near‐optimal cropland sites to minimize the cost to produce a targeted quantity of an energy crop, considering soil properties, fertilizer management, and spatio‐temporal trends in crop yield and soil emissions. DayCent, a biogeochemical model, simulates site‐level crop yield, and soil emissions. As a case study, this framework is applied to a 2.08 × 108 L year−1 capacity barley‐to‐ethanol biorefinery that selects cultivation sites from winter fallow cropland in the mid‐Atlantic region of the USA. The framework implements carbon crediting as per California's Low Carbon Fuel Standard. Our analysis finds the biorefinery's strategy on co‐products significantly influences its life‐cycle carbon intensity ranging between 0.74 gCO2e MJ−1 for all co‐product use and 59 gCO2e MJ−1 for no co‐product use. Coastal counties in Delaware show low soil emission and high yield, but higher transportation distances increase the carbon intensity of these distant croplands. When co‐products are used, the least intensive fertilizer management with fertilizer applications in spring is identified as the cost‐optimized choice for the biorefinery. It is also the option economically favored by growers, suggesting that detailed monitoring of these practices might not be needed to assure the adoption of low‐emission cultivation practices. However, the framework might demonstrate different results for other biofuel‐crop scenarios or different locations. The framework presented can assess the performance of a biorefinery prospectively and improve investors’ confidence in the biofuel industry. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Sequential bioethanol and methane production from municipal solid waste: An integrated biorefinery strategy towards cost-effectiveness

The organic fraction of municipal waste (OFMW), source-sorted (SS-OFMW) and non-sorted (NS-OFMW), was used as raw material for the sequential production of bioethanol and biogas. Non-isothermal and simultaneous saccharification and fermentation (NSSF) resulted in maximum ethanol concentrations of 51 g/L and 26 g/L for SS-OFMW and NS-OFMW samples, showing overall process yields of up to 80 % and 59 %, respectively, even without subjecting substrate to hydrothermal pretreatment. Subsequently, the solid residues resulting from the fermentation were further subjected to anaerobic digestion (AD), showing a methanogenic potential of 384 ± 6 mL CH4/g of volatile solids (VSin) and 322 ± 3 mL CH4/g VSin, respectively. These methane yields were similar or even higher to those obtained when using non-fermented OFMW substrates (SS-OFMW: 380 ± 18 mL CH4/g VSin and NS-OFMW: 239 ± 4 mL CH4/g VSin), highlighting NSSF as a beneficial step to enhance methane yields during AD. Overall, bioconversion of OFMW would benefit from coupling bioethanol and biogas production since the biogas produced might be further employed as bioenergy source to compensate operational costs.

Reductive catalytic fractionation of lignin in birch sawdust to monophenolic compounds with high selectivity

Reductive catalytic fractionation (RCF) has emerged as a novel biorefinery strategy for the efficient fractionation and utilization of lignocellulosic biomass. Herein, hydrogenolysis of lignin in birch sawdust in the presence of noble metal based catalysts (Ru/C, Pd/C, Pt/C) were investigated. The total yield of monophenolic compounds was 41.4 wt% (TOF, 5.28 h−1) and the selectivity towards 4-propyl guaiacol and 4-propyl syringol reached 82.8 % with 5 % Ru/C under optimized conditions. The cleavage of β-O-4 and α-O-4 (cyclic) aryl ether linkages in the trimers and tetramers resulted in the formation of lignin-derived dimers, which were quantified by the derivatization method. The high surface area of catalysts with the highly dispersed and small sized metallic particles contributed to the degradation of higher molecular weight oligomers. The catalysts could promote the cleavage of COC ether bonds and hydrogenation of unsaturated side-chain CC bonds to obtain propyl-substituted monophenolic compounds with high selectivity.

Formosolv Pretreatment to Fractionate Paulownia Wood Following a Biorefinery Approach: Isolation and Characterization of the Lignin Fraction

Paulownia is a rapid-growth tree with a high biomass production rate per year and low demand of water, which make it very suitable for intercropping systems, as it protects the crops from adverse climatic conditions, benefiting the harvest yields. Moreover, these characteristics make Paulownia a suitable raw material able to be fractionated in an integrated biorefinery scheme to obtain multiple products using a cascade conversion approach. Different delignification pretreatments of biomass have been purposed as a first stage of a lignocellulosic biorefinery. In this study, the formosolv delignification of Paulownia wood was investigated using a second order face-centered factorial design to assess the effects of the independent variables (concentrations of formic and hydrochloric acids and reaction time) on the fractionation of Paulownia wood. The maximum delignification achieved in this study (78.5%) was obtained under following conditions: 60 min, and 95% and 0.05% formic and hydrochloric acid, respectively. In addition, the remained solid phases were analyzed to determine their cellulose content and cooking liquors were also chemically analyzed and characterized. Finally, the recovered lignin by precipitation from formosolv liquor and the pristine lignin (milled wood lignin) in Paulownia wood were characterized and compared by the following techniques FTIR, NMR, high-performance size-exclusion chromatography (HPSEC) and TGA. This complete characterization allowed verifying the capacity of the formosolv process to act on the lignin, causing changes in its structure, which included both phenomena of depolymerization and condensation.

An environment-economic analysis of hydrogen production using advanced biorefineries and its comparison with conventional technologies

This paper shows how novel high-performance thermophilic consortia employed in the dark fermentation stage of a biorefinery can lead to a competitive commercial-scale hydrogen production using lignocellulosic biomass as feedstock. The biorefinery design alternatives under study also include either diluted acid or hydrothermal pretreatment, and the option of either selling the biogas produced in the wastewater treatment stage or using it for electricity cogeneration. A bi-dimensional (i.e., environmental-economic) sustainability analysis was carried out comparing these four design alternatives against two conventional schemes (coal gasification and natural gas reforming). Results showed that, under a regulatory framework that considers environmental and economic issues on the same basis, the low total production costs of conventional schemes are not enough to compensate, in monetary terms, their severe environmental impacts (mainly water usage and pollution) when compared with the biorefining options. Moreover, most of the proposed biorefinery schemes ranked higher than conventional options. In particular, the design with acid pretreatment and biogas sale was the most sustainable option with a positive global sustainability indicator (0.007 USD/MJout).