One-pot bio-derived ionic liquid conversion followed by hydrogenolysis reaction for biomass valorization: A promising approach affecting the morphology and quality of lignin of switchgrass and poplar

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.

Recent Advances in the Catalytic Conversion of Biomass to Furfural in Deep Eutectic Solvents

Lignocellulose is recognized as an ideal raw material for biorefinery as it may be converted into biofuels and value-added products through a series of chemical routes. Furfural, a bio-based platform chemical generated from lignocellulosic biomass, has been identified as a very versatile alternative to fossil fuels. Deep eutectic solvents (DES) are new “green” solvents, which have been employed as green and cheap alternatives to traditional organic solvents and ionic liquids (ILs), with the advantages of low cost, low toxicity, and biodegradability, and also have been proven to be effective media for the synthesis of biomass-derived chemicals. This review summarizes the recent advances in the conversion of carbohydrates to furfural in DES solvent systems, which mainly focus on the effect of adding different catalysts to the DES system, including metal halides, water, solid acid catalyst, and certain oxides, on the production of furfural. Moreover, the challenges and perspectives of DES-assisted furfural synthesis in biorefinery systems are also discussed in this review.

The application of green solvent in a biorefinery using lignocellulosic biomass as a feedstock

The high dependence on crude oil for energy utilization leads to a necessity of finding alternative sustainable resources. Solvents are often employed in valorizing the biomass into bioproducts and other value-added chemicals during treatment stages. Unfortunately, despite the effectiveness of conventional solvents, hindrances such as expensive solvents, unfavourable environmental ramifications, and complicated downstream separation systems often occur. Therefore, the scientific community has been actively investigating more cost-effective, environmentally friendly alternatives and possess the excellent dissolving capability for biomass processing. Generally, 'green' solvents are attractive due to their low toxicity, economic value, and biodegradability. Nonetheless, green solvents are not without disadvantages due to their complicated product recovery, recyclability, and high operational cost. This review summarizes and evaluates the recent contributions, including potential advantages, challenges, and drawbacks of green solvents, namely ionic liquids, deep eutectic solvents, water, biomass-derived solvents and carbon dioxide in transforming the lignocellulosic biomass into high-value products. Moreover, research opportunities for future developments and potential upscale implementation of green solvents are also critically discussed.

Aqueous choline amino acid deep eutectic solvents

We have investigated the structure and phase behavior of biocompatible, aqueous deep eutectic solvents by combining choline acetate, hydrogen aspartate, and aspartate amino acid salts with water as the sole molecular hydrogen bond donor. Using contrast-variation neutron diffraction, interpreted via computational modeling, we show how the interplay between anion structure and water content affects the hydrogen bond network structure in the liquid, which, in turn, influences the eutectic composition and temperature. These mixtures expand the current range choline amino acid ionic liquids under investigation for biomass processing applications to include higher melting point salts and also explain how the ionic liquids retain their desirable properties in aqueous solution.

Transforming lignocellulosic biomass into biofuels enabled by ionic liquid pretreatment

Processes that can convert lignocellulosic biomass into biofuels and chemicals are particularly attractive considering renewability and minimal environmental impact. Ionic liquids (ILs) have been used as novel solvents in the process development in that they can effectively deconstruct recalcitrant lignocellulosic biomass for high sugar yield and lignin recovery. From cellulose-dissolving ILs to choline-based and protic acidic ILs, extensive research in this field has been done, driven by the promising future of IL pretreatment. Meanwhile, shortcomings and technological hurdles are ascertained during research and developments. It is necessary to present a general overview of recent developments and challenges in this field. In this review paper, three aspects of advances in IL pretreatment are critically analyzed: biocompatible ILs, protic acidic ILs and combinatory pretreatments.

Advanced Bioethanol Production: From Novel Raw Materials to Integrated Biorefineries

The production of so-called advanced bioethanol offers several advantages compared to traditional bioethanol production processes in terms of sustainability criteria. This includes, for instance, the use of nonfood crops or residual biomass as raw material and a higher potential for reducing greenhouse gas emissions. The present review focuses on the recent progress related to the production of advanced bioethanol, (i) highlighting current results from using novel biomass sources such as the organic fraction of municipal solid waste and certain industrial residues (e.g., residues from the paper, food, and beverage industries); (ii) describing new developments in pretreatment technologies for the fractionation and conversion of lignocellulosic biomass, such as the bioextrusion process or the use of novel ionic liquids; (iii) listing the use of new enzyme catalysts and microbial strains during saccharification and fermentation processes. Furthermore, the most promising biorefinery approaches that will contribute to the cost-competitiveness of advanced bioethanol production processes are also discussed, focusing on innovative technologies and applications that can contribute to achieve a more sustainable and effective utilization of all biomass fractions. Special attention is given to integrated strategies such as lignocellulose-based biorefineries for the simultaneous production of bioethanol and other high added value bioproducts.

Ionic liquid based pretreatment of lignocellulosic biomass for enhanced bioconversion

Lignocellulosic biomass is the most plentiful renewable biomolecule and an alternative bioresource for the production of biofuels and biochemicals in biorefineries. But biomass recalcitrance is a bottleneck in their usage, thus necessitating their pretreatment for hydrolysis. Most pretreatment technologies, result in toxic by-products or have lower yield. Ionic liquids (ILs) have successfully advanced as 'greener and recyclable' alternatives to volatile organic solvents for lignocellulosic biomass dissolution. This review covers recent developments made in usage of IL-based techniques with focus on biomass breakdown mechanism, process parameter design, impact of cation and anion groups, and the advantageous impact of ILs on the subsequent processing of the fractionated biomass. Progress and barriers for large-scale commercial usage of ILs in emerging biorefineries were critically evaluated using the principles of economies of scale and green chemistry in an environmentally sustainable way.