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Agave bagasse (AG) is used as potential bioenergy feedstock due to its high biomass productivity, even in semiarid lands. In particular, Ionic liquid (IL) pretreatment using aprotic ILs (AILs) has been greatly reduce AG recalcitrance towards downstream processing by lowering lignin content and achieving high sugar yields. However, AILs low biocompatibility towards enzymes and bacteria combined with the high initial cost has limited further development of this technology. We have evaluated the pretreatment of AG with a biocompatible low-cost protic IL (PIL), 2-hydroxyethylammonium acetate ([2-HEA][OAc]), in a wash-free one-pot (OP) ethanol conversion process. Where PIL pretreatment was followed by enzymatic saccharification, then ethanol fermentation in a single vessel. The pretreatment conditions were optimized using a central composite design to enable high sugar conversion at low PIL content. Under optimized pretreatment conditions (160 °C, 60% IL loading and 1.5 h), a yield of 132 kg of ethanol per Ton of untreated biomass was obtained using high solids loading (30 % solids loading) under a PIL-OP scheme. High lignin removal (>50 %), low cellulose crystallinity, and high glucan conversion (>85%) were achieved with PIL-pretreated AG comparable to yields obtained in an AIL-AG pretreated sample using 1-ethyl-3-methyl-imidazolium acetate ([C2C1Im][OAc]). These results using [2-HEA][OAc] demonstrate the potential of AG as a bioenergy feedstock with improved total ethanol yields paving the way towards a more feasible IL-based biorefinery.

We present an implementation of the interacting quantum atom (IQA) energy decomposition scheme using the complete active space second-order perturbation theory (CASPT2). This combination yields a real-space interpretation tool with a proper account of the static and dynamic correlation that is particularly relevant for the description of processes in electronic excited states. The IQA/CASPT2 approach allows determination of the energy redistribution that takes place along a photophysical/photochemical deactivation path in terms of self- and interatomic contributions. The applicability of the method is illustrated by the description of representative processes spanning different bonding regimes: noble gas excimer and exciplex formation, the reaction of ozone with a chlorine atom, and the photodissociations of formaldehyde and cyclobutane. These examples show the versatility of using CASPT2 with the significant information provided by the IQA partition to describe chemical processes with a large multiconfigurational character.

In recent years, bioderived ionic liquids have gained attention as a new promising approach for lignocellulosic biomass pretreatment. In this work, Agave tequilana bagasse (ATB), an attractive bioenergy feedstock in Mexico, was pretreated with a bioderived ionic liquid (cholinium lysinate) for the first time. Optimization of the pretreatment conditions, in-depth biomass characterization and methane generation via anaerobic digestion are the main contributions of this work. The results indicated optimized pretreatment conditions of 124 °C, 205 min and 20% solids loading by applying a central composite design. The optimized pretreated ATB was able to produce an elevated sugar yield of 51.4 g total sugars per g ATB due to their high delignification (45.4%) and changes in their chemical linkages although an increase in cellulose crystallinity was found (0.51 untreated vs. 0.62 pretreated). Finally, the mass balance showed that 38.2 kg glucose and 13.1 kg xylose were converted into 12.5 kg of methane per 100 kg of untreated ATB, representing 86% of the theoretical methane yield and evidencing the potential of this biorefinery scheme.

Lignin has long been considered as an abundant and renewable feedstock to produce biofuels and value-added products. However, its commercialization has been reduced mainly to heat and power generation after its recovery from two of the most used delignification technologies in paper industry, the Kraft and sulfite processes. This chapter reviews the fundamentals and advances in lignin extraction methods, its processing to produce valuable fuels, carbon fiber, plastics, copolymers, and platform chemicals. Since the better understanding of the structure and interactions of lignin in biomass allows efficient downstream processing, the description of its structural compounds and its characterization methods, including nuclear magnetic resonance spectroscopy, are also reviewed. Topics such as the biorefinery lignin valorization, techno-economic analysis, and life cycle assessment are reviewed to evidence the hotspots. This chapter ends with the final opinions on the advances and work-to-do on lignin valorization to improve its manufacturing and competition against petroleum-derived applications.

A pilot-scale continuous tubular reactor (PCTR) was employed for the isothermal pretreatment of agave bagasse (AG), corn stover (CS), sugarcane bagasse (SC), and wheat straw (WS) with three residence times. The objective was to evaluate the impact of this technology on enzymatic saccharification at low solid loadings (4% w/v) and on sequential saccharification and glucose fermentation (SSF) at high solid loading (20% w/v) for bioethanol production. Deformation in cellulose and hemicellulose linkages and xylan removal of up to 60% were achieved after pretreatment. The shortest residence time tested (20 min) resulted in the highest glucan to glucose conversion in the low solid loading (4% w/v) enzymatic saccharification step for AG (83.3%), WS (82.8%), CS (76.1%) and SC (51.8%). Final ethanol concentrations after SSF from PCTR-pretreated biomass were in the range of 38 to 42 g L−1 (11.0–11.3 kg of ethanol per 100 kg of untreated biomass). Additionally, PCTR performance in terms of xylan removal and sugar release were compared with those from a batch lab-scale autohydrolysis reactor (BLR) under the same process conditions. BLR removed higher xylan amounts than those achieved in the PCTR. However, higher sugar concentrations were obtained with PCTR for SC (13.2 g L−1 vs. 10.5 g L−1) and WS (21.7 g L−1 vs. 18.8 g L−1), whilst differences were not significant (p < 0.05) with BLR for AG (16.0 g L−1 vs. 16.3 g L−1) and CS (18.7 g L−1 vs. 18.4 g L−1).

Agave has recently shown its potential as a bioenergy feedstock with promising features such as higher biomass productivity than leading bioenergy feedstock while at the same time being drought-resistant with low water requirements and high sugar to ethanol conversion using ionic liquid (IL) pretreatment. IL pretreatment was studied to develop the first direct side-by-side comparative recalcitrance assessment of the agro-industrial residues from five Agave species [Agave americana (AME), A. angustifolia (ANG), A. fourcroydes (FOU), A. salmiana (SAL), and A. tequilana (TEQ)] using compositional analysis, X-ray diffraction, and the lignin syringyl/guaiacyl subunit ratio (S/G) by pyrolysis molecular beam mass spectrometry (PyMBMS). Prominent calcium oxalate peaks were found only in unpretreated AME, SAL, and TEQ. The S/G ratios of all five unpretreated Agave species were between 1.27 and 1.57 while the IL-pretreated samples were from 1.39 to 1.72. The highest overall sugar production was obtained with IL-pretreated FOU with 492 mg glucose/g biomass and 157 mg xylose/g biomass at 120 °C and 3 h using 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]). An estimated theoretical ethanol yield from the studied agro-industrial residues from the five Agave species was in the range of 1060 to 5800 L ethanol/ha/year. These comparison results demonstrate the potential of the Agave spp. as a suitable biofuel feedstock which can be employed within a biorefinery scheme.

In recent years, Agave has shown its potential as a bioenergy feedstock with a higher land productivity (up to 42 ton/ha year) than traditional feedstocks. Other features are its adaptation mechanism to high temperatures and its resistance to drought. The agronomics of Agave in Mexico are discussed, including total land planted, inputs required, and the harvesting and transport costs. Heating values, mineral concentration, and carbohydrate and lignin content show the potential of the Agave species to compete with current bioenergy crops. Currently, the pre-treatment of Agave is the most widely studied stage in biofuels and value-added products, which include technologies capable of reducing its recalcitrance while removing xylan and/or lignin and reducing cellulose crystallinity, among other effects, to increase the overall yield in saccharification and fermentation, which will be discussed as well. In addition to spirits and fibers from industrial interests, different liquid (ethanol and n-butanol) and gaseous (methane and hydrogen) biofuels, including certain value-added products (enzymes, lactic acid, and succinic acid), can be obtained from Agave in high yields. The main objective of this review is to address the recent advances in the utilization of Agave as a bioenergy feedstock for biofuels and value-added products within a sustainable biorefinery scheme. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd

Biorefineries are considered as an integrative thinking that focuses on the possibility of obtaining as many added-value products as technically and economically feasible. However, in practice most biorefineries comprise only enzymatic or chemical pretreatment followed by biofuel generation. The drop in oil prices may menace the development of this young industry, as has happened before in history. This has become a fundamental reason for which the biofuel industry should not consider only biofuels production, but enzyme and non-fuel based chemicals as well. Hence, this work aims at overviewing the most important enzymes involved in biotechnological processes and to describe their role in biorefineries. Bioethanol, biogas and biodiesel biorefineries are overviewed, along with the integrated and industrial types. Finally separation and purification processes in biorefineries are discussed. © 2016 Society of Chemical Industry

Occurrence of calcium oxalate (CaC2O4 – CaOX) crystals has been observed in more than 215 plant families. However, very little is known about the effects of calcium oxalate on biomass pretreatment and saccharification. Agave bagasse (AGB) was used as a model material due to its natural high levels of CaOX. To understand the physicochemical changes in function of biomass pretreatment, both raw AGB and CaOX-extracted agave bagasse (EAB) were subjected to ionic liquid (IL) with 1-Butyl-3-methylimidazolium chloride [C4C1Im][Cl] and alkaline hydrogen peroxide (AHP) pretreatments. Physicochemical changes were monitored by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and wet chemistry methods. Results show that free CaOX crystals affected negatively (by ca 39%) the saccharification of AHP-pretreated EAB compared to AGB. On the other hand, IL pretreatment achieved higher sugar yield (7.8 g dm−3) and lower crystallinity (14%) with EAB than for AHP (5.4 g dm−3 and 29%, respectively).

A comparative analysis of the response of agave bagasse (AGB) to pretreatment by ammonia fiber expansion (AFEX™), autohydrolysis (AH) and ionic liquid (IL) was performed using 2D nuclear magnetic resonance (NMR) spectroscopy, wet chemistry, enzymatic saccharification and mass balances. It has been found that AFEX pretreatment preserved all carbohydrates in the biomass, whereas AH removed 62.4% of xylan and IL extracted 25% of lignin into wash streams. Syringyl and guaiacyl lignin ratio of untreated AGB was 4.3, whereas for the pretreated biomass the ratios were 4.2, 5.0 and 4.7 for AFEX, AH and IL, respectively. Using NMR spectra, the intensity of β-aryl ether units in aliphatic, anomeric, and aromatic regions decreased in all three pretreated samples when compared to untreated biomass. Yields of glucose plus xylose in the major hydrolysate stream were 42.5, 39.7 and 26.9kg per 100kg of untreated AGB for AFEX, IL and AH, respectively.

Sequential 2k 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.

Previous studies of agave bagasse (AGB-byproduct of tequila industry) presented unidentified crystalline peaks that are not typical from common biofuel feedstocks (e.g. sugarcane bagasse, switchgrass or corn stover) making it an important issue to be addressed for future biorefinery applications. Ionic liquid (IL) pretreatment of AGB was performed using 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) at 120, 140 and 160 °C for 3 h and a mass fraction of 3% in order to identify these peaks. Pretreated samples were analyzed by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electronic microscopy (FE-SEM), thermal analysis (TGA-DSC) and wet chemistry methods. Previous unidentified XRD peaks on AGB at 2θ = 15°, 24.5° and 30.5°, were found to correspond to calcium oxalate (CaC2O4) in a monohydrated form. IL pretreatment with [C2mim][OAc] was observed to remove CaC2O4 and decrease cellulose crystallinity. At 140 °C, IL pretreatment significantly enhances enzymatic kinetics and leads to ∼8 times increase in sugar yield (6.66 kg m−3) when compared to the untreated samples (960 g m−3). These results indicate that IL pretreatment can effectively process lignocellulosic biomass with high levels of CaC2O4.

Background Pretreatment is necessary to reduce biomass recalcitrance and enhance the efficiency of enzymatic saccharification for biofuel production. Ionic liquid (IL) pretreatment has gained a significant interest as a pretreatment process that can reduce cellulose crystallinity and remove lignin, key factors that govern enzyme accessibility. There are several challenges that need to be addressed for IL pretreatment to become viable for commercialization, including IL cost and recyclability. In addition, it is unclear whether ILs can maintain process performance when utilizing low-cost, low-quality biomass feedstocks such as the paper fraction of municipal solid waste (MSW), which are readily available in high quantities. One approach to potentially reduce IL cost is to use a blend of ILs at different concentrations in aqueous mixtures. Herein, we describe 14 IL-water systems with mixtures of 1-ethyl-3-ethylimidazolium acetate ([C2C1Im][OAc]), 1-butyl-3-ethylimidazolium acetate ([C4C1Im][OAc]), and water that were used to pretreat MSW blended with agave bagasse (AGB). The detailed analysis of IL recycling in terms of sugar yields of pretreated biomass and IL stability was examined. Results Both biomass types (AGB and MSW) were efficiently disrupted by IL pretreatment. The pretreatment efficiency of [C2C1Im][OAc] and [C4C1Im][OAc] decreased when mixed with water above 40%. The AGB/MSW (1:1) blend demonstrated a glucan conversion of 94.1 and 83.0% using IL systems with ~10 and ~40% water content, respectively. Chemical structures of fresh ILs and recycle ILs presented strong similarities observed by FTIR and 1H-NMR spectroscopy. The glucan and xylan hydrolysis yields obtained from recycled IL exhibited a slight decrease in pretreatment efficiency (less than 10% in terms of hydrolysis yields compared to that of fresh IL), and a decrease in cellulose crystallinity was observed. Conclusions Our results demonstrated that mixing ILs such as [C2C1Im][OAc] and [C4C1Im][OAc] and blending the paper fraction of MSW with agricultural residues, such as AGB, may contribute to lower the production costs while maintaining high sugar yields. Recycled IL-water mixtures provided comparable results to that of fresh ILs. Both of these results offer the potential of reducing the production costs of sugars and biofuels at biorefineries as compared to more conventional IL conversion technologies.Graphical abstractSchematic of ionic liquid (IL) pretreatment of agave bagasse (AB) and paper-rich fraction of municipal solid waste (MSW) Electronic supplementary material The online version of this article (doi:10.1186/s13068-017-0758-4) contains supplementary material, which is available to authorized users.

Lignocellulose represents a sustainable source of carbon for transformation into biofuels. Effective biomass to sugar conversion strategies are needed to lower processing cost without degradation of polysaccharides. Since ionic liquids (ILs) are excellent solvents for pretreatment/dissolution of biomass, IL pretreatment was carried out on agave bagasse (AGB-byproduct of tequila industry) and digestibility and sugar yield was compared with that obtained with switchgrass (SWG). The IL pretreatment was conducted using ([C2mim][OAc]) at 120 and 160 °C for 3h and 15% biomass loading. While pretreatment using [C2mim][OAc] was very effective in improving the digestibility of both feedstocks, IL pretreatment at 160 °C resulted in higher delignification for AGB (45.5%) than for SWG (38.4%) when compared to 120 °C (AGB-16.6%, SWG-8.2%), formation of a highly amorphous cellulose structure and a significant enhancement of enzyme kinetics. These results highlight the potential of AGB as a biofuel feedstock that can produce high sugar yields with IL pretreatment.

In this work, experimental vapor–liquid equilibrium (T, p, xi, yi) data for the ternary carbon dioxide–ethanol–nonane and carbon dioxide–ethanol–decane systems are reported in the temperature range of 313–373 K from low pressures to the nearest of the corresponding critical pressure. Measurements were performed in an apparatus based on the static-analytic method with an on-line ROLSI sampler-injector device. Vapor–liquid equilibrium (VLE) data for both ternary systems are predicted using the Peng–Robinson equation of state coupled to the Wong–Sandler, one parameter van der Waals and two parameters van der Waals mixing rules. Binary interaction parameters are obtained from the VLE data of binary mixtures reported in the literature.

Agave bagasse (AGB) has gained recognition as a drought-tolerant biofuel feedstock with high productivity in semiarid regions. A comparative analysis of ionic liquid (IL) and organosolv (OV) pretreatment technologies in AGB was performed using a sequential enzymatic saccharification and fermentation (SESF) strategy with cellulolytic enzymes and the ethanologenic Escherichia coli strain MS04. After pretreatment, 86% of xylan and 45% of lignin were removed from OV-AGB, whereas IL-AGB reduced lignin content by 28% and xylan by 50% when compared to the untreated biomass. High glucan (>90%) and xylan (>83%) conversion was obtained with both pretreated samples. During the fermentation stage (48h), 12.1 and 12.7kg of ethanol were produced per 100kg of untreated AGB for IL and OV, respectively. These comparative analyses showed the advantages of SESF using IL and OV in a biorefinery configuration where a better understanding of AGB recalcitrance is key for future applications.

Utilization of lignocellulosic materials for the production of value-added chemicals or biofuels generally requires a pretreatment process to overcome the recalcitrance of the plant biomass for further enzymatic hydrolysis and fermentation stages. Two of the most employed pretreatment processes are the ones that used dilute acid (DA) and alkaline (AL) catalyst providing specific effects on the physicochemical structure of the biomass, such as high xylan and lignin removal for DA and AL, respectively. Another important effect that need to be studied is the use of a high solids pretreatment (≥15%) since offers many advantaged over lower solids loadings, including increased sugar and ethanol concentrations (in combination with a high solids saccharification), which will be reflected in lower capital costs; however, this data is currently limited. In this study, several variables, such as catalyst loading, retention time, and solids loading, were studied using response surface methodology (RSM) based on a factorial central composite design of DA and AL pretreatment on agave bagasse using a range of solids from 3 to 30% (w/w) to obtain optimal process conditions for each pretreatment. Subsequently enzymatic hydrolysis was performed using Novozymes Cellic CTec2 and HTec2 presented as total reducing sugar (TRS) yield. Pretreated biomass was characterized by wet-chemistry techniques and selected samples were analyzed by calorimetric techniques, and scanning electron/confocal fluorescent microscopy. RSM was also used to optimize the pretreatment conditions for maximum TRS yield. The optimum conditions were determined for AL pretreatment: 1.87% NaOH concentration, 50.3 min and 13.1% solids loading, whereas DA pretreatment: 2.1% acid concentration, 33.8 min and 8.5% solids loading.

Although ethanol can be produced from a wide range of biomass materials, biomass, from the tropical region, like mango (skin or bagasse) is a crop residue readily available today as a non-conventional crop for the saccharification process that has had little attention. It has the benefits to be found in large quantities and in an industrial level is completely separated into its components with a free access for acid or enzymatic hydrolysis. These agro-industrial waste as well as other materials like sugarcane bagasse and pine wood are abundant enough, and in virtue of their high carbohydrate content hold tremendous potential for large-scale bioethanol production. The objective of this work is to develop a comparative analysis using dilute acid hydrolysis process between mango (skin and bagasse), sugarcane bagasse, and pine wood. The biomass was subjected to pretreatments like alkaline hydrolysis using calcium sulfate and sodium hydroxide, water immersion, and water autoclaved at 121 °C. Experimental results showed that the maximum percentages of sugar recovery were for sugarcane bagasse—56.62%, pine wood—82.36%, mango skin—97.37%, and mango bagasse—202.91%. From the tested biomass materials, only mango bagasse has a considerable fraction of already digestible sugar that does not undergo a pretreatment + hydrolysis process.