Efficient dehydration and recovery of ionic liquid after lignocellulosic processing using pervaporation

`A critical review on current status and environmental sustainability of pre-treatment methods for bioethanol production from lignocellulose feedstocks

Lignocellulosic biomass resource has been widely used as a natural resource for the synthesis of biofuels and bio-based products through pre-treatment, saccharification and fermentation processes. In this review, we delve into the environmental implications of bioethanol production from the widely utilized lignocellulosic biomass resource. The focus of our study is the critical stage of pre-treatment in the synthesis process, which also includes saccharification and fermentation. By collecting scientific data from the available literature, we conducted a comprehensive life cycle analysis. Our findings revealed substantial differences in the environmental burdens associated with diverse pre-treatment methods used for lignocellulosic biomass. These results highlight the importance of selecting environmentally benign pre-treatment techniques to promote the sustainability of bioethanol production. Future research directions are suggested, emphasizing the optimization of pre-treatment processes to further mitigate their environmental impact.

Advances of Imidazolium Ionic Liquids for the Extraction of Phytochemicals from Plants

In this review, we present the research from 2013 to 2022 about the character of ionic liquids, the categories of phytochemicals, and the reasons for selecting imidazolium ionic liquids for phytochemical extraction. Then we introduce the structural formulae of the imidazolium ionic liquids commonly used in the extraction of phytochemicals, the methods used to prepare imidazolium ionic liquids, and a comprehensive introduction of how imidazolium ionic liquids are applied to extract phytochemicals from plants. Importantly, we discuss the strategies for studying the extraction mechanisms of imidazolium ionic liquids to extract phytochemicals, and the recovery methods regarding imidazolium ionic liquids and their recyclability are analyzed. Then the toxicity in imidazolium ionic liquids is pointed out. Finally, the challenges and prospects of extracting phytochemicals by imidazolium ionic liquids are summarized, and they are expected to provide some references for researchers.

Challenges in Using Ionic Liquids for Cellulosic Ethanol Production

The growing need to expand the use of renewable energy sources in a sustainable manner, providing greater energy supply security and reducing the environmental impacts associated with fossil fuels, finds in the agricultural by-product bioethanol an economically viable alternative with significant expansion potential. In this regard, a dramatic boost in the efficiency of processes already in place is required, reducing costs, industrial waste, and our carbon footprint. Biofuels are one of the most promising alternatives to massively produce energy sustainably in a short-term period. Lignocellulosic biomass (LCB) is highly recalcitrant, and an effective pretreatment strategy should also minimize carbohydrate degradation by diminishing enzyme inhibitors and other products that are toxic to fermenting microorganisms. Ionic liquids (ILs) have been playing an important role in achieving cleaner processes as a result of their excellent physicochemical properties and outstanding performance in the dissolution and fractionation of lignocellulose. This review provides an analysis of recent advances in the production process of biofuels from LCB using ILs as pretreatment and highlighting techniques for optimizing and reducing process costs that should help to develop robust LCB conversion processes.

Machine learning for surrogate process models of bioproduction pathways

Technoeconomic analysis and life-cycle assessment are critical to guiding and prioritizing bench-scale experiments and to evaluating economic and environmental performance of biofuel or biochemical production processes at scale. Traditionally, commercial process simulation tools have been used to develop detailed models for these purposes. However, developing and running such models can be costly and computationally intensive, which limits the degree to which they can be shared and reproduced in the broader research community. This study evaluates the potential of an automated machine learning approach to develop surrogate models based on conventional process simulation models. The analysis focuses on several high-value biofuels and bioproducts for which pathways of production from biomass feedstocks have been well-established. The results demonstrate that surrogate models can be an accurate and effective tool for approximating the cost, mass and energy balance outputs of more complex process simulations at a fraction of the computational expense.

Review of chemical pretreatment of lignocellulosic biomass using low-liquid and low-chemical catalysts for effective bioconversion

Chemical pretreatment of lignocellulosic biomass (LCB) is essential for effective biological conversion in subsequent steps to produce biofuels or biochemicals. For effective pretreatment, high lignin content and its recalcitrant nature of LCB are major factors influencing bioconversion, especially lignin is known to be effectively solubilized by alkaline, organic, and deep eutectic solvents, ionic liquids, while hemicellulose is effectively dissolved by various acid catalysts and organic solvents. Depending on the pretreatment method/catalyst used, different pretreatment process scheme should be applied with different amounts of catalyst and water inputs to achieve a satisfactory effect. In addition, the amount of processing water required in the following processes such as washing, catalyst recovery, and conditioning after pretreatment is critical factor for scale-up (commercialization). In this review, the amount of catalyst and/or water used, and the effect of pretreatment, properties of the products, and recovery of liquid are also discussed.

Industrial sludge valorization and decontamination via lipid extraction and heavy metals removal using low-cost protic ionic liquid

Sludge is a heterogenous organic-rich matter that comprise of highly valuable biopolymers along with various contaminants including heavy metals. Sludge valorization as a renewable resource and inexpensive feedstock is key for sludge realization in circular economy context. This study presents the use of low-cost protic ionic liquid (PIL) as an integrated process medium to decontaminate heavy metal contaminated industrial sludge while selectively extract the lipid content. The treatment process focused on the use of 1-methylimidazole chloride for its higher heavy metal extraction performance compared to other screened ionic liquids (ILs). The treatment was also able to selectively extract lipids from industrial sludge, leaving a protein/carbohydrate rich solid product. Process temperature was shown to have a key impact on the biopolymers' fractionation. Operating at temperatures above 120 °C resulted in higher recovery of proteins in the lipid-rich fraction, compromising the quality of the lipid stream. Variation of the PIL acid/base (a/b) ratio also had a significant impact on the deconstruction of the sludge biopolymers, with a/b ratio of 1 resulting in highest recovery of all biopolymers. Optimal water concentration as co-solvent was found at 30 wt%, with lipid recovery reaching 60% and heavy metals extraction ranging between 29 and 89%.

Recent Advances in Biomass Pretreatment Technologies for Biohydrogen Production

Hydrogen is an economical source of clean energy that has been utilized by industry for decades. In recent years, demand for hydrogen has risen significantly. Hydrogen sources include water electrolysis, hydrocarbon steam reforming, and fossil fuels, which emit hazardous greenhouse gases and therefore have a negative impact on global warming. The increasing worldwide population has created much pressure on natural fuels, with a growing gap between demand for renewable energy and its insufficient supply. As a result, the environment has suffered from alarming increases in pollution levels. Biohydrogen is a sustainable energy form and a preferable substitute for fossil fuel. Anaerobic fermentation, photo fermentation, microbial and enzymatic photolysis or combinations of such techniques are new approaches for producing biohydrogen. For cost-effective biohydrogen production, the substrate should be cheap and renewable. Substrates including algal biomass, agriculture residue, and wastewaters are readily available. Moreover, substrates rich in starch and cellulose such as plant stalks or agricultural waste, or food industry waste such as cheese whey are reported to support dark- and photo-fermentation. However, their direct utilization as a substrate is not recommended due to their complex nature. Therefore, they must be pretreated before use to release fermentable sugars. Various pretreatment technologies have been established and are still being developed. This article focuses on pretreatment techniques for biohydrogen production and discusses their efficiency and suitability, including hybrid-treatment technology.

Renewable biohydrogen production from lignocellulosic biomass using fermentation and integration of systems with other energy generation technologies

Biohydrogen is a clean and renewable source of energy. It can be produced by using technologies such as thermochemical, electrolysis, photoelectrochemical and biological, etc. Among these technologies, the biological method (dark fermentation) is considered more sustainable and ecofriendly. Dark fermentation involves anaerobic microbes which degrade carbohydrate rich substrate and produce hydrogen. Lignocellulosic biomass is an abundantly available raw material and can be utilized as an economic and renewable substrate for biohydrogen production. Although there are many hurdles, continuous advancements in lignocellulosic biomass pretreatment technology, microbial fermentation (mixed substrate and co-culture fermentation), the involvement of molecular biology techniques, and understanding of various factors (pH, T, addition of nanomaterials) effect on biohydrogen productivity and yield render this technology efficient and capable to meet future energy demands. Further integration of biohydrogen production technology with other products such as bio-alcohol, volatile fatty acids (VFAs), and methane have the potential to improve the efficiency and economics of the overall process. In this article, various methods used for lignocellulosic biomass pretreatment, technologies in trends to produce and improve biohydrogen production, a coproduction of other energy resources, and techno-economic analysis of biohydrogen production from lignocellulosic biomass are reviewed.

Response of Pseudomonas putida to Complex, Aromatic-Rich Fractions from Biomass

There is strong interest in the valorization of lignin to produce valuable products; however, its structural complexity has been a conversion bottleneck. Chemical pretreatment liberates lignin-derived soluble fractions that may be upgraded by bioconversion. Cholinium ionic liquid pretreatment of sorghum produced soluble, aromatic-rich fractions that were converted by Pseudomonas putida (P. putida), a promising host for aromatic bioconversion. Growth studies and mutational analysis demonstrated that P. putida growth on these fractions was dependent on aromatic monomers but unknown factors also contributed. Proteomic and metabolomic analyses indicated that these unknown factors were amino acids and residual ionic liquid; the oligomeric aromatic fraction derived from lignin was not converted. A cholinium catabolic pathway was identified, and the deletion of the pathway stopped the ability of P. putida to grow on cholinium ionic liquid. This work demonstrates that aromatic-rich fractions obtained through pretreatment contain multiple substrates; conversion strategies should account for this complexity.

Regenerated Hoof Keratin from 1-Ethyl-3-Methylimidazolium Acetate and Insights into Disulfide-Ionic Liquid Interactions from MD Simulation

Regeneration of the hoof keratin from ionic liquids was never successful in the past because the ionic liquids were not strong enough. However, this biomaterial starts to play a central role for the preparation of biofilms in the future. In the present study, hoof keratin was regenerated for the first time from an ionic liquid by experiment and characterized by FTIR spectroscopy, Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). As 1-Ethyl-3-methylimidazolium acetate is strong enough to dissolve hooves, which have a lot of disulfide bonds, a Molecular Dynamics (MD) simulation was performed with this ionic liquid and diphenyl disulfide. The MD simulation reveals that not only the cation as postulated after experiments were carried out, but also the anion is very important for the dissolution process. This complete picture was and is not accessible via experiments and is therefore valuable for future investigations. The anion always interacts with the disulfide bond, whereas the cation prefers in some situations a strong H-O interaction with the anion. If the cations and the anions are separated from each other so that the cation can not interact with the anion, both interact with the disulfide bond. The high solvation power of this solvent is shown by the fact that the cation interacts from the left and right side and the anion from above and below the disulfide bond.

Recent developments in pretreatment technologies on lignocellulosic biomass: Effect of key parameters, technological improvements, and challenges

Lignocellulosic biomass is an inexpensive renewable source that can be used to produce biofuels and bioproducts. The recalcitrance nature of biomass hampers polysaccharide accessibility for enzymes and microbes. Several pretreatment methods have been developed for the conversion of lignocellulosic biomass into value-added products. However, these pretreatment methods also produce a wide range of secondary compounds, which are inhibitory to enzymes and microorganisms. The selection of an effective and efficient pretreatment method discussed in the review and its process optimization can significantly reduce the production of inhibitory compounds and may lead to enhanced production of fermentable sugars and biochemicals. Moreover, evolutionary and genetic engineering approaches are being used for the improvement of microbial tolerance towards inhibitors. Advancements in pretreatment and detoxification technologies may help to increase the productivity of lignocellulose-based biorefinery. In this review, we discuss the recent advancements in lignocellulosic biomass pretreatment technologies and strategies for the removal of inhibitors.

Eco-efficient recovery of bio-based volatile C2-6 fatty acids

BACKGROUND

Volatile fatty acids (VFAs) are produced by fermentation of various bio-sources and human wastes at minimal cost; sometimes, even sources having a prepaid processing fee were used. However, low concentrations of VFAs in water have prevented their commercial production, even with modern separation technologies, due to the high operating costs. We have applied newly developed solvents, selected by chemical structure similarity, to the separation of five different VFAs.

RESULTS

Since most of the water was separated by extraction using hexyl acetate and nonyl acetate, the utilities necessary for solvent recovery and product purification were a fraction of those required by the existing VFAs' separation processes. The solvents separated almost all the water in the feed at the extraction stage, consuming no energy. The energy use in this study is only 34% of the lowest case use among various processes of either distillation-only or combined extraction-distillation.

CONCLUSIONS

The performance evaluation of the proposed VFAs separation process showed that product recovery was 99% and acid purity was 99.5% with eco-scores of 70% lower than those of the current processes.

Mild reaction conditions induce high sugar yields during the pretreatment of Agave tequilana bagasse with 1-ethyl-3-methylimidazolium acetate

Sequential 2^k factorial and central composite designs were used to optimize Agave tequilana bagasse (ATB) pretreatment by using 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). Reaction time, temperature and solids loading were the studied factors while sugar yield was the response variable. Results indicated that optimal conditions (119 °C, 142 min) using high solids loading (30%) were achieved at lower temperatures and reaction times than those previously reported in the literature. It was also revealed that solid recovery after pretreatment with [Emim][OAc] is a key factor. The increase in enzymatic digestibility of pretreated ATB was correlated to a decrease in crystallinity and lower lignin content as observed using microscopy techniques and weaken chemical bonds by Fourier transform infrared spectroscopy. Yields of glucose and xylose in the hydrolysate were 41.3, and 13.0 kg per 100 kg of untreated ATB, which are equivalent to glucan and xylan conversions of 75.9% and 82.9%, respectively.

Probabilistic Lifecycle Assessment of Butanol Production from Corn Stover Using Different Pretreatment Methods

The recalcitrant nature of lignocelluloses requires a pretreatment process before the fermentative butanol production. The commonly used pretreatment processes, such as steam explosion, sulfuric acid, ammonia fiber explosion, ionic liquid (IL), and biological, require different quantities and types of process chemicals, and produce different quality and quantity of fermentable sugars. This study determines life-cycle greenhouse gas emissions (GHG) these pretreatment methods by developing a system-level process model including corn stover feedstock supply system and the downstream butanol production process. This study further evaluates the uncertainty associated with energy use and GHG emissions for each stage of the entire butanol production chain and provide the future optimization opportunities. Probabilistic results of these analyses describe a distribution of GHG emissions with an average of 18.09-1056.12 gCO_2e/MJ and a 95% certainty to be less than 33.3-1888.3 gCO_2e /MJ. The highest GHG emissions of IL-pretreatment of 1056.12 gCO_2e/MJ reaches to 89.8 gCO_2e/MJ by switching IL-recovery from 80 to 99 wt %, which is the most influential parameter for IL-pretreatment. Additionally, credits from excess electricity, butanol yield, nitrogen replacement, and diesel fuel for transportation and harvesting were the most influential parameters. Based on the current state of technologies, apart from ionic liquid and biological pretreatments, other pretreatment processes have similar metrics of sustainability.

Structural changes in lignocellulosic biomass during activation with ionic liquids comprising 3-methylimidazolium cations and carboxylate anions

BACKGROUND

Lignocellulosic biomass requires either pretreatment and/or fractionation to recover its individual components for further use as intermediate building blocks for producing fuels, chemicals, and products. Numerous ionic liquids (ILs) have been investigated for biomass pretreatment or fractionation due to their ability to activate lignocellulosic biomass, thereby reducing biomass recalcitrance with minimal impact on its structural components. In this work, we studied and compared 1-allyl-3-methylimidazolium formate ([AMIM][HCOO]) to the commonly used 1-ethyl-3-methylimidazolium acetate ([EMIM][CH₃COO]) for its potential to activate hybrid poplar biomass and enable high cellulose and hemicellulose enzymatic conversion. Although [EMIM][CH₃COO] has been widely used for activation, [AMIM][HCOO] was recently identified to achieve higher biomass solubility, with an increase of 40% over [EMIM][CH₃COO].

RESULTS

Since IL activation is essentially an early stage of IL dissolution, we assessed the recalcitrance of [EMIM][CH₃COO] and [AMIM][HCOO]-activated biomass through a suite of analytical tools. More specifically, Fourier transform infrared spectroscopy and X-ray diffraction showed that activation using [AMIM][HCOO] does not deacetylate hybrid poplar as readily as [EMIM][CH₃COO] and preserves the crystallinity of the cellulose fraction, respectively. This was supported by scanning electron microscopy and enzymatic saccharification experiments in which [EMIM][CH₃COO]-activated biomass yielded almost twice the cellulose and hemicellulose conversion as compared to [AMIM][HCOO]-activated biomass.

CONCLUSION

We conclude that the IL [AMIM][HCOO] is better suited for biomass dissolution and direct product formation, whereas [EMIM][CH₃COO] remains the better IL for biomass activation and fractionation.

Recovery and purification of ionic liquids from solutions: a review

With low melting point, extremely low vapor pressure and non-flammability, ionic liquids have been attracting much attention from academic and industrial fields. Great efforts have been made to facilitate their applications in catalytic processes, extraction, desulfurization, gas separation, hydrogenation, electronic manufacturing, etc. To reduce the cost and environmental effects, different technologies have been proposed to recover the ionic liquids from different solutions after their application. This review is mainly focused on the recent advances of the recovery and purification of ionic liquids from solutions. Several methods for recovery of ionic liquids including distillation, extraction, adsorption, membrane separation, aqueous two-phase extraction, crystallization and external force field separation, are introduced and discussed systematically. Some industrial applications of ionic liquid recovery and purification methods are selected for discussion. Additionally, considerations on the combined design of different methods and process optimization have also been touched on to provide potential insights for future development of ionic liquid recovery and purification.