Biorefinery Process Research Articles

Biorefinery superstructure optimization under carbon pricing policies using stochastic programming

The growing utilization of biomass feedstocks for climate change mitigation has led to increased research on biorefineries. Concurrently, environmental policies are evolving as crucial tools to address these global concerns. Cap-and-trade, carbon tax, and carbon cap policies have been established to reduce carbon dioxide emissions. In this work, a mathematical optimization model is developed to integrate biorefinery process design with carbon pricing policies and crediting mechanisms. A two-stage stochastic mixed integer linear programming model is proposed to account for emissions, feedstock supply, chemical demand, and pricing uncertainties. A bi-objective optimization framework is employed to consider economic and environmental metrics. The framework is a valuable tool for governments and businesses to determine pareto-optimal investment strategies under environmental policies. It is applicable for evaluating prospective chemical technologies with carbon pricing policies beyond biorefineries. The results indicate that carbon crediting mechanisms can minimize the financial penalty by up to 50% under a carbon tax policy. Implementing chemical demand constraints within a cap-and-trade policy reduces potential profits, especially when the carbon prices are high. The stochastic programming approach revealed that underestimating the expected carbon cap leads to lower expected profits. Despite the financial implications of these policies, profitable process designs are achievable.

Tobacco as a promising crop for low-carbon biorefinery

Energy crops play a vital role in meeting future energy and chemical demands while addressing climate change. However, the idealization of low-carbon workflows and careful consideration of cost-benefit equations are crucial for their more sustainable implementation. Here, we propose tobacco as a promising energy crop because of its exceptional water solubility, mainly attributed to a high proportion of water-soluble carbohydrates and nitrogen, less lignocellulose, and the presence of acids. We then designed a strategy that maximizes biomass conversion into bio-based products while minimizing energy and material inputs. By autoclaving tobacco leaves in water, we obtained a nutrient-rich medium capable of supporting the growth of microorganisms and the production of bioproducts without the need for extensive pretreatment, hydrolysis, or additional supplements. Additionally, cultivating tobacco on barren lands can generate sufficient biomass to produce approximately 573 billion gallons of ethanol per year. This approach also leads to a reduction of greenhouse gas emissions by approximately 76% compared to traditional corn stover during biorefinery processes. Therefore, our study presents a novel and direct strategy that could significantly contribute to the goal of reducing carbon emissions and global sustainable development compared to traditional methods.

Emulsion liquid membrane pertraction of soap from crude biodiesel using activated carbon and glycol based deep eutectic solvents

Soap removal from crude biodiesel is considered as one of the most challenging biorefinery processes. This study reports a new technique for soap removal incorporating activated carbon (AC) in an emulsion liquid membrane (ELM) system based on deep eutectic solvents (DES-AC-ELM). These DESs were prepared from two salts, namely tetramethylammonium chloride (TMAC) and choline chloride (ChCl), with different hydrogen bond donors (HBDs) such as ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG). COSMO-RS modelling was performed in the evaluation of the activity coefficients and capacity at infinite dilution of DESs. The COSMO-RS simulation shows that the DESs with TEG as the HBD are the most effective stripping agents for soap removal which is in accordance with the experimental results. In addition, the σ-profile and σ-potential were used to investigate the interactions between the soap molecules in each phase. The impact of various process parameters on the soap removal such as the salt: HBD ratio, DES:biodiesel ratio, span-20 concentration, mixing speed, extraction time and dosage of AC were evaluated. The proposed technique achieved a soap extraction efficiency of 99.1% (6.856 ppm) and 97.5% (18.773 ppm) for TMAC:TEG(DES3) and ChCl:TEG(DES6), respectively, with a salt: HBD molar ratio of 1:4, DES:biodiesel ratio of 1:1, 2 wt% surfactant concentration, 10 min extraction duration, 400 rpm mixing speed, 0.5 treatment ratio and 0.5 wt% AC dosage. The transport mechanism of soap conforms to a first-order mass transfer behaviour, with a kinetic rate constant of 0.64 min−1 and 0.43 min−1, for DES3 and DES6, respectively. This study illustrated a new cleaner and simple route for purification of crude biodiesel.

Utilization of banana peel waste for the production of bioethanol and other high-value-added compounds

Bananas (Musa sp.) are one of the most produced crops worldwide, surpassing 100 million tons per year, and considering that approximately 30 % of their weight consists of peels, the annual generation of these residues is significant. Banana residues are rich in nutrients; nowadays, they are all disposed of in landfills. As a novelty, this work showed that it could be used for other things, such as alcohol, D-Limonene, and citric acid production. This study characterized the biomass, optimized pretreatment, and enzymatic hydrolysis and evaluated the fermentation process using this biomass, using the central composite design (CCD) methodology. The planning variables included sulfuric acid (H2SO4) concentration, banana peel waste mass in the pretreatment stage, and commercial cellulase enzyme (Sigma-Aldrich) concentration in the enzymatic hydrolysis stage. The responses quantified were sugars, ethanol, and acids using high-performance liquid chromatography, and the D-Limonene content was determined on a gas chromatograph coupled to a mass spectrometer. The highest yield of total reducing sugars found after enzymatic hydrolysis was 11.88 g/L, while the ethanol yield was 1.37 g/L. In the recovery of D-Limonene, the obtained value was 0.56 mg/g. The values of fermentable sugars confirm banana peel waste as a potential biomass for biorefinery processes. Furthermore, the possibility of an integrated D-Limonene recovery is essential in obtaining bioproducts. In this sense, it can be concluded that utilizing these residues is promising in reducing environmental issues and valorizing food waste.

The Role of Lignin Molecular Weight on Activated Carbon Pore Structure.

Over the past decade, the production of biofuels from lignocellulosic biomass has steadily increased to offset the use of fuels from petroleum. To make biofuels cost-competitive, however, it is necessary to add value to the "ligno-" components (up to 30% by mass) of the biomass. The properties of lignin, in terms of molecular weight (MW), chemical functionality, and mineral impurities often vary from biomass source and biorefinery process, resulting in a challenging precursor for product development. Activated carbon (AC) is a feasible target for the lignin-rich byproduct streams because it can be made from nearly any biomass, and it has a market capacity large enough to use much of the lignin generated from the biorefineries. However, it is not known how the variability in the lignin affects the key properties of AC, because, until now, they could not be well controlled. In this work, various fractions of ultraclean (<0.6% ash) lignin are created with refined MW distributions using Aqueous Lignin Purification using Hot Agents (ALPHA) and used as precursors for AC. AC is synthesized via zinc chloride activation and characterized for pore structure and adsorption capacity. We show that AC surface area and the adsorption capacity increase when using lignin with increasing MW, and, furthermore, that reducing the mineral content of lignin can significantly enhance the AC properties. The surface area of the AC from the highest MW lignin can reach ~1830 m2/g (absorption capacity). Furthermore, single step activation carbonization using zinc chloride allows for minimal carbon burn off (<30%), capturing most of the lignin carbon compared to traditional burn off methods in biorefineries for heat generation.

Characterization of a novel cellobiose phosphorylase with broad optimal pH range from a tailings pond macrogenomic library

Glucose-1-phosphate, a crucial pharmaceutical intermediate, can be generated through the synergistic transformation of lignocellulose using cellulase and cellobiose phosphorylase (CBP), thus holding promise for a profitable biorefinery process. However, the reported optimal pH range of CBPs (6.0–7.5) does not align with that of cellulase (4.8), resulting in suboptimal efficiency in the one-pot conversion of cellulose to glucose-1-phosphate. In this study, we identified a novel cellobiose phosphorylase, CBP1942, comprising 811 amino acid residues (92.5 kDa), in tailing pond macrogenomes, exhibiting identity of 60% to 75% with reported CBPs. CBP1942 was efficiently expressed in E. coli BL21 and purified with His tagging. It maintains over 90% enzyme activity across pH 4–9. Compared to the benchmark CtCBP (GenBank ID: AAL67138.1), CBP1942 displays a 1.2-fold increase in specific enzyme activity at the optimal cellulase temperature (50 °C), indicating its superior suitability for cellulase compounding. CBP1942 exhibits Km and kcat values of 6.69 mM and 8.83 s−1, respectively, with a kcat/Km ratio 6.6 times higher than CtCBP, suggesting superior catalytic efficiency. Notably, CBP1942 shows remarkable thermal stability, retaining 94.67% enzyme activity after 3 h at 50 °C, while CtCBP retains only 78.33%. Additionally, CBP1942 complexed with cellulase enhances the conversion of corn stover, resulting in a 6.2-fold increase in glucose-1-phosphate yield compared to CtCBP. These findings indicate CBP1942’s potential as an industrial enzyme for corn stover conversion to glucose-1-phosphate.

One-Pot Electrosynthesis of Gamma-Butyrolactone (GBL) from Furoic Acid

The catalytic valorization of biomass to afford synthetically useful small molecules is essential for sustainable biorefinery processes. Herein, we present a mild cascaded electrochemical protocol for converting furoic acid (FA), a common biomass-derived feedstock, into a versatile platform chemical, gamma-butyrolactone (GBL). All involved species participate in the desired redox pathway with high selectivity: FA was electrochemically oxidized with 84.2% selectivity to 2(5H)-furanone (2-FO), the olefin of which was then hydrogenated to yield GBL with 98.5% selectivity. We identified that a certain temperature is an important factor in enabling the one-pot reaction as it promotes thermal desorption of the key intermediate. The reaction was scalable to gram-scale, producing high-purity GBL isolated through a simple solvent extraction from a 500-mL electrolysis scale reaction.

Biovalorizing felled oil palm trunk as a sole feedstock for lactic acid production through efficient simultaneous saccharification and fermentation

This study aimed to develop practical biorefinery process for bio-valorizing felled oil palm trunk (OPT) as a sole feedstock for lactic acid (LA) production. OPT was separated into oil palm sap (OPS), vascular bundle (OPT-VB), and parenchyma (OPT-PA) fractions. OPS containing high amounts of sugars (38.69 g/L) and nitrogen (0.63 g/L), could be used directly for LA production by Lactobacillus acidophilus and also as base medium for simultaneous saccharification and fermentation (SSF) of OTP-VB and OPT-PA. The repeated SSF efficiently utilized cellulosic OPT-VB and produced LA up to 50–71 g/L during five cycles. Due to high water-absorbing and swelling properties of OPT-PA, it could not be initially added at high loadings. It was then intermittently added through fed-batch SSF, which effectively produced LA of 72.85 ± 1.61 g/L. These strategies have shown the efficient biorefinery process for biovalorization of OPT and may also be applicable to other similar agricultural wastes.

Metal-organic framework-enabled biomass conversion technologies for microalgae bio-refinery in the food industry.

Biomass is a valuable renewable energy adapted as an alternative to traditional fossil fuels. Apart from fuels, biomass is synthesized into highly valuable products that are used in various forms including biofuels, biochemical, bioproducts, packing material, and find practice in pharmaceutical, cosmetics, and nutraceuticals industries. Particularly, microalgae a third-generation feedstock known for its rich carbon content possesses protein lipids and carbohydrates produces a variety of green products such as bioethanol, biohydrogen, biodiesel, and biomethane, and also fixes carbon emission to a certain amount in the atmosphere. However, microalgae conversion in the presence of a catalyst such as a metal-organic framework (MOF) yields high-quality valuable products. A MOF is a porous crystalline material where the structure and pore size can be controlled making it suitable for catalytic reactions and appropriate conversion paths. This review briefly explains the prevailing status of microalgae as a sustainable biomass and features its components for microalgae biorefinery into valuable products and its application in the food industry. MOF properties, characteristics and various MOF-based conversion technologies for biomass conversion with its application are elaborated. In addition, usage of value products produced from microalgae biorefinery in the food industry and its importance is elucidated. In addition, the challenges in integrating biorefinery processes with food industry operations and their solutions are also presented. © 2024 Society of Chemical Industry.

Adequately converting poplar sawdust’s carbohydrates to furfural and glucose by employing acid oxidation pretreatment and solid acid catalysis

The utilization of lignocellulosic biorefinery residue has always been a major obstacle hindering its industrialization. In this work, the acetic acid assisted hydrogen peroxide pretreatment (AHP) and enzymatic hydrolysis was employed to facilitate the efficient bioconversion of poplar sawdust (PS), while simultaneously utilizing the solid acid catalyst (SA) synthesized from enzymatically hydrolyzed PS (EPS) for furfural production from prehydrolysate. It demonstrated that enzymatic hydrolysis of PS achieved a glucose yield of 61.3 %, which can be attributed to the effective removal of xylan and lignin through AHP pretreatment. The structural characterization revealed that SA-EPS exhibited a higher pore density, more acidic sites, and an increased presence of acidic groups compared with SA prepared from PS. Ultimately, the utilization of SA-EPS significantly augmented furfural yield and selectivity to 54.3 % and 64.1 %, respectively. By successfully synthesizing SA using lignin-rich EPS, the value-added benefits and increased efficiency have been achieved in biorefinery processes.

SUSTAINABILITY OF BEACH CAST SEAWEED BIOMASS FOR BIOREFINARY PROCESS: SAMPLING STUDIES IN THE LITTORAL OF ALAGOAS/BRAZIL

Renewable feedstocks provide changes to more sustainable systems, where natural resources are preserved with their own perennial cycles. Macroalgae as substrate it is a natural resource of inexhaustible abundance in the ocean, growing three to four times more than terrestrial plants. Some countries discard this biomass in landfills as "unserviceable" generating an environmental liability in the management of solid waste. The objective of this work was to evaluate the sustainability of beach cast seaweed biomass for industrial processes. Sampling studies research in a period of two years were carried out in seven beaches of the coast of Maceió, Alagoas - Brazil. The methodology was selecting the statistical models Levene's test, One-way ANOVA, Tukey's, Student-Newman-Keul's test and the PAST program for the sampling studies. The samples were collected according to the zigzag sampling method, covering a deposition area of 135.000 m². The results obtained an estimate daily collection of 5.03 tons/ha of dry biomass in 26 species analysed; it means 35 times superior to Brazilian sugarcane biomass. Based on the results, it is observed that beach cast seaweed biomass has possibilities to industrial biorefinery processes.

Evaluation of an operating durian shell charcoal briquette manufacturing line and development of a biorefinery process for higher value products

In assessing the feasibility of carbonization for the treatment of durian shell, a large-scale (10 T) fuel briquette manufacturing line is evaluated, taking into consideration the actual processing time and the effect of the biomass high moisture content on overall efficiency. The fuel product exhibits a high higher heating value (HHV) (33.21 MJ/kg) but with a low production efficiency (10 %) and a high cost of production (0.55 USD/kg briquette). One alternate biorefinery process was proposed to turn durian shells into much higher value materials, including high-methoxyl pectin (DE > 90 %), high surface area activated carbon (>300 m2/g) and mineral-rich biochar, with higher recovery efficiency and selling prices, most notably pectin at 40 USD/kg. The results from this study are then used to provide recommendations for feasible treatment, not only for durian shells but also for a variety of different complex and highly recalcitrant biomass in pursuit of a more sustainable agricultural production.

Supercritical CO2 as effective wheat straw pretreatment for subsequent mild fractionation strategies

The efficient utilization of lignocellulosic biomass in biorefineries is pivotal for the transition to a carbon–neutral society, emphasizing the need for environmentally friendly fractionation techniques. While the extensive use of chemicals in biorefinery operations can yield favorable quantities of specific biomass components, adopting less chemically intense conditions is crucial for holistic methodologies that preserve the inherent potential of all biomass constituents. This study comprehensively investigates the use of supercritical carbon dioxide (sc-CO2) as a green pretreatment to improve subsequent mild fractionation on wheat straw. Sc-CO2 at 300 bars, 100 °C and 70% moisture was found to have minimal impact on the chemical composition and the lignin structure, while there were significant morphological changes as heightened surface area and reduced density. Apart from increasing enzymatic saccharification efficiency, the treatment notably enhanced subsequent mild delignification through alkaline and flow-through organosolv extractions. The combination of the pretreatments enhances the lignin solubilization yields from 49 to 79% for alkaline and 74 to 91% for organosolv extractions, while retaining a high β-O-4 conservation of 49 and 59 linkages per 100 aromatic units, respectively. Additionally, the combined use of sc-CO2 with mild dilute acid pretreatment improved xylose solubilization from 59 to 76 % and enzymatic saccharification from 53 to 90%, albeit with increased lignin condensation. In summary, this study demonstrates the potential of sc-CO2 pretreatment as a versatile tool for biomass valorization within the evolving bioeconomy, by combining enhanced extraction yields with minimal lignin structural impact. Our work thereby highlights the promise of the use of sc-CO2 to contribute to the overall economic potential of improved biorefinery processes.

Bicarbonate concentration influences carbon utilization rates and biochemical profiles of freshwater and marine microalgae.

Selecting the optimal microalgal strain for carbon capture and biomass production is crucial for ensuring the commercial viability of microalgae-based biorefinery processes. This study aimed to evaluate the impact of varying bicarbonate concentrations on the growth rates, inorganic carbon (IC) utilization, and biochemical composition of three freshwater and two marine microalgal species. Parachlorella kessleri, Vischeria cf. stellata, and Porphyridium purpureum achieved the highest carbon removal efficiency (>85%) and biomass production at 6gL-1 sodium bicarbonate (NaHCO3), while Phaeodactylum tricornutum showed optimal performance at 1gL-1 NaHCO3. The growth and carbon removal rate of Scenedesmus quadricauda increased with increasing NaHCO3 concentrations, although its highest carbon removal efficiency (∼70%) was lower than the other species. Varying NaHCO3 levels significantly impacted the biochemical composition of P. kessleri, S. quadricauda, and P. purpureum but did not affect the composition of the remaining species. The fatty acid profiles of the microalgae were dominated by C16 and C18 fatty acids, with P. purpureum and P. tricornutum yielding relatively high polyunsaturated fatty acid content ranging between 14% and 30%. Furthermore, bicarbonate concentration had a species-specific effect on the fatty acid and chlorophyll-a content. This study demonstrates the potential of bicarbonate as an effective IC source for microalgal cultivation, highlighting its ability to select microalgal species for various applications based on their carbon capture efficiency and biochemical composition.

ADVANCING SUSTAINABLE RESOURCE UTILISATION: A REVIEW OF AQUATIC BIOREFINERIES

This review explores the transformative potential of aquatic biorefineries in advancing sustainable resource utilisation. As global demands for renewable resources intensify, biorefineries have emerged as versatile solutions. Focusing on aquatic environments, this paper delves into diverse biomass resources, encompassing microorganisms, algae and aquatic plants. It navigates through key biorefinery processes, including hydrothermal liquefaction, algae cultivation and enzymatic conversion, illuminating their roles in sustainable biofuel and high-value chemical production. Thermochemical conversion processes, such as pyrolysis and gasification, offer additional pathways for bio-based product generation. The review critically assesses challenges in these processes, ranging from technical intricacies to regulatory considerations. Examining products derived from aquatic biorefineries (i.e. biofuels, chemicals and biomaterials) underscores their versatility. Looking ahead, the paper identifies technical challenges, regulatory landscapes and emerging technologies as focal points for future research. The review concludes by envisioning aquatic biorefineries as key players in sustainable resource management, advocating for research and technological innovation to propel this transformative field into the mainstream of the bio-based economy.

Evaluation of Antioxidant Activity of Residue from Bioethanol Production Using Seaweed Biomass.

This study explores the potential of producing bioethanol from seaweed biomass and reusing the residues as antioxidant compounds. Various types of seaweed, including red (Gelidium amansii, Gloiopeltis furcata, Pyropia tenera), brown (Saccharina japonica, Undaria pinnatifida, Ascophyllum nodosum), and green species (Ulva intestinalis, Ulva prolifera, Codium fragile), were pretreated with dilute acid and enzymes and subsequently processed to produce bioethanol with Saccharomyces cerevisiae BY4741. Ethanol production followed the utilization of sugars, resulting in the highest yields from red algae > brown algae > green algae due to their high carbohydrate content. The residual biomass was extracted with water, ethanol, or methanol to evaluate its antioxidant activity. Among the nine seaweeds, the A. nodosum bioethanol residue extract (BRE) showed the highest antioxidant activity regarding the 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity, ferric reducing antioxidant power (FRAP), and reactive oxygen species (ROS) inhibition of H2O2-treated RAW 264.7 cells. These by-products can be valorized, contributing to a more sustainable and economically viable biorefinery process. This dual approach not only enhances the utilization of marine resources but also supports the development of high-value bioproducts.

Experimental Study on Vapor–Liquid and Solid–Liquid Equilibria Data for the Regeneration of Biobased Solvents Guaiacol and 2,2,5,5-Tetramethyl Oxolane in Biorefinery Processes

Experimental Study on Vapor–Liquid and Solid–Liquid Equilibria Data for the Regeneration of Biobased Solvents Guaiacol and 2,2,5,5-Tetramethyl Oxolane in Biorefinery Processes

Revisiting the Electrocatalyst Role on Lignin Depolymerization

Replacing fossil resources as the primary source of carbon‐based chemicals by alternative feedstocks, while implementing more sustainable production routes, has become imperative for environmental and resource sustainability. In this context, lignin, often treated as a biomass waste, emerges as an appealing candidate, considering the principles of circular economy. For this pursuit, depolymerization methods offer potential strategies to harness lignin to produce valuable organic chemicals, while electrocatalysis processes stand out especially in the context of sustainability, as they can be powered by electricity from renewable sources. This minireview article explores the pivotal role of various electrocatalysts in lignin depolymerization, investigating both oxidative and reductive pathways. Emphasizing recent advancements, the review delves into the diverse nature of electrocatalysts and their influence on lignin valorization. Highlighting current trends, the discussion encompasses the catalytic mechanisms and selectivity of electrochemical processes employed for lignin breakdown. Additionally, some insights into emerging technologies are also offered, emphasizing the need for sustainable and efficient strategies. By providing an overview of the field, this minireview aims to guide future research endeavors toward innovative electrocatalytic approaches for lignin depolymerization, paving the way for sustainable biorefinery processes.

Engineering Bacillus licheniformis as industrial chassis for efficient bioproduction from starch

Starch is an attractive feedstock in biorefinery processes, while the low natural conversion rate of most microorganisms limits its applications. Herein, starch metabolic pathway was systematically investigated using Bacillus licheniformis DW2 as the host organism. Initially, the effects of overexpressing amylolytic enzymes on starch hydrolysis were evaluated. Subsequently, the transmembrane transport system and intracellular degradation module were modified to accelerate the uptake of hydrolysates and their further conversion to glucose-6-phosphate. The DW2-derived strains exhibited robust growth in starch medium, and productivity of bacitracin and subtilisin were improved by 38.5% and 32.6%, with an 32.3% and 22.9% increase of starch conversion rate, respectively. Lastly, the employment of engineering strategies enabled another B. licheniformis WX-02 to produce poly-γ-glutamic acid from starch with a 2.1-fold increase of starch conversion rate. This study not only provided excellent B. licheniformis chassis for sustainable bioproduction from starch, but shed light on researches of substrate utilization.

Simultaneous production of furfural, lignin and cellulose-rich residue from Eucalyptus urophylla × E. grandis by ChCl/1,2-propanediol/MIBK biphasic system pretreatment

A facile biphasic system composed of choline chloride (ChCl)-based deep eutectic solvent (DES) and methyl isobutyl ketone (MIBK) was developed to realize the furfural production, lignin separation and preparation of fermentable glucose from Eucalyptus in one-pot. Results showed that the ChCl/1,2-propanediol/MIBK system owned the best property to convert hemicelluloses into furfural. Under the optimal conditions (MRChCl:1,2-propanediol = 1:2, raw materials:DES:MIBK ratio = 1:4:8 g/g/mL, 0.075 mol/L AlCl3·6H2O, 140 °C, and 90 min), the furfural yield and glucose yield reached 65.0 and 92.2 %, respectively. Meanwhile, the lignin with low molecular weight (1250–1930 g/mol), low polydispersity (DM = 1.25–1.53) and high purity (only 0.08–2.59 % carbohydrate content) was regenerated from the biphasic system. With the increase of pretreatment temperature, the β-O-4, β-β and β-5 linkages in the regenerated lignin were gradually broken, and the content of phenolic hydroxyl groups increased, but the content of aliphatic hydroxyl groups decreased. This research provides a new strategy for the comprehensive utilization of lignocellulose in biorefinery process.