Steam Explosion Pretreatment Research Articles

Isolating cellulose nanofibers from steam-explosion pretreated corncobs using mild mechanochemical treatments

Cellulose nanofibers (CNFs) with an average diameter 8 nm were isolated from corncobs using a stepwise method that included steam-explosion pretreatment, alkaline treatment, sodium hypochlorite bleaching, high-speed blending, and ultrasonic treatment. This mechanochemical method used only two chemical reagents in low concentrations to remove non-cellulosic components. The removal of non-cellulosic components was confirmed by Fourier-transform infrared spectroscopy. X-ray diffraction revealed an increase in crystallinity during steam explosion and subsequent mechanochemical treatments. Pretreatment by steam explosion caused the partial hydrolysis of hemicellulose and loosened the structure of raw materials, which facilitated the subsequent chemical processes. The thermal stability and morphology of samples at different stages were also investigated. Steam explosion increased the thermal stability of hemicellulose and cellulose components, as it removed a fraction of hemicellulose. High-speed blending reduced the entanglement of cellulosic fibers and created uniform size. Ultrasonic treatment was used in the final step of nanoscale fibrillation. The method used in this study is environmentally friendly and has the potential to be applied at industrial scale.

Investigation of different pretreatment methods of Mediterranean-type ecosystem agricultural residues: characterisation of pretreatment products, high-solids enzymatic hydrolysis and bioethanol production

ABSTRACTAgricultural and agro-industrial lignocellulosic residues represent an important renewable resource for the production of fuels and chemicals towards a bio-based economy. Olive pruning, vineyard pruning and almond shells are important residues from agricultural activities in Mediterranean-type ecosystems. In the current work, bioethanol production from the above three types of agro-residues was studied, focusing on the effect of different pretreatment methods on enzymatic saccharrification efficiency of cellulose and production of second-generation bioethanol. Dilute acid, hydrothermal and steam explosion pretreatments were compared in order to remove hemicellulose and facilitate the subsequent enzymatic hydrolysis of the hemicellulose-deficient biomass to glucose. Enzymatic hydrolysis was performed in a free-fall mixing reactor enabling high solids loading of 23% w/w. This allowed hydrolysis of up to 67% of available cellulose in almond shells and close to 50% in olive pruning samples, and facilitated high ethanol production in the subsequent fermentation step; the highest ethanol concentrations achieved were 47.8 g/L for almond shells after steam explosion and 42 g/L for hydrothermally pretreated olive pruning residue.

Optimization of Ultrasonic Assisted Saccharification of Sweet Lime Peel for Bioethanol Production Using Box–Behnken Method

In this study, ultrasonication was investigated for hydrolysis of sweet lime peel instead of utilizing it as a pretreatment process. Ultrasonication is one of the upcoming hydrolysis techniques that can offer high reducing sugar yield in shorter times and temperature with reduced acid consumption. Optimization studies of the hydrolysis process parameters were carried out to maximize the reducing sugar yield using the Box–Behnken method. From Box–Behnken design, 46 experiments were conducted and the effect of sulfuric acid concentration, peel concentration, sonication time, temperature and amplitude of ultrasound on reducing sugar yield were investigated. Fermentation of the hydrolysate was performed using baker’s yeast and the effect of time and pH on ethanol production was studied. Maximum ethanol yield by fermentation was observed as 64%. Scanning electron micrographs revealed that the regular and compact surface of raw biomass was altered into an irregular and scattered surface as a result of pretreatment and hydrolysis, which showed the prospective feasibility of sulfuric acid assisted steam explosion pretreatment and ultrasound assisted acid hydrolysis. From the experimental study, it was observed that ultrasonication can be explored for hydrolysis of pretreated lignocellulosic biomass to obtain high reducing sugar yield for bioethanol production.

High Concentration Ethanol Production from Mixed Softwood Sawdust Waste

Steam explosion pretreatment with high steam pressures, i.e. 35–55 atm, was conducted for the effective conversion of mixed softwood sawdust waste into ethanol. The results show the steam explosion with high steam pressures can significantly enhance the glucose yield after enzymatic saccharification and ethanol yield after alcohol fermentation. The effects of steam pressure on physical and chemical characteristics of steam-exploded sawdust were also clarified. Avoiding the effect of inhibitory materials produced by steam explosion with high pressures on enzymatic saccharification and alcohol fermentation, water and methanol extractions were attempted. The residue after water and methanol extractions of steam-exploded sawdust at a steam pressure 45 atm for a steaming time of 5 min was the most effective for the enzymatic saccharification followed by alcohol fermentation, and obtained a highest glucose yield, i.e. 81%. Simultaneous saccharification and fermentation using a high concentration of the residue resulted in an increased ethanol concentration and provided an ethanol production, i.e. 46.0 and 66.7 g/L, and a volumetric productivity of ethanol, i.e. 0.64 and 0.92 g/L h, from 200 to 300 g/L residue, respectively.

Steam explosion pretreatment improved the biomethanization of coffee husks

This study evaluated the potential of energy generation using a combined heat and power co-generation system (CHP) from biogas produced during the anaerobic digestion of coffee husks (CH) pretreated with steam explosion. Pretreatment conditions assessed were time (1, 5, 15 and 60min) and temperature (120, 180 and 210°C). Polysaccharides solubilisation and biogas production were not correlated. While pretreatment with severities higher than 4 resulted in a highest solubilisation of cellulose, hemicelluloses and lignin; however, furans concentration in those cases hindered biomass biodegradation. Considering a CHP, all pretreatment conditions were worthwhile when compared to non-pretreated CH. The best condition was 120°C for 60min, in which a 2.37 severity showed the highest methane yield (144.96NmLCH4gCOD−1) and electricity production (0.59kWhkgCH−1). However, even better results could be achieved using 120°C for only 5min, which would lead to a larger amount of CH daily processed.

Fungal chitosan production using xylose rich of corn stover prehydrolysate by Rhizopus oryzae

ABSTRACTXylose rich of lignocellulosic prehydrolysate could be used for fungal chitosan production effectively by Rhizopus oryzae. When 15 g/L xylose was used as carbon source for R. oryzae AS 3.819 fermentation, almost all of the xylose was consumed for cell growth (4.33 g/L of biomass) and the chitosan extraction yield was 0.11 g/g biomass. Corn stover prehydrolysate by dilute acid-assisted steam explosion pretreatment that contained 30 g/L xylose and 10 g/L glucose was fermented by R. oryzae AS 3.819 for 72 h, the biomass and the chitosan extraction yield were 10.96 g/L and 0.09 g/g biomass. The degree of deacetylation of the fungal chitosan derived from corn stover prehydrolysate (91.27%) was higher than that of the commercial chitosan extracted from natural shellfish exoskeleton (87.25%), and the viscosity of the fungal chitosan derived from corn stover prehydrolysate (2.67 mPa⋅s) had a large decrease compared to the commercial chitosan (22.25 mPa⋅s). The functional groups and thermostability of the fungal chitosan were proofed by Infrared (IR) spectra and Derivative thermogravimetric (DTG), respectively.

Fractionation of Lignocellulosic Residues Coupling Steam Explosion and Organosolv Treatments Using Green Solvent γ-Valerolactone

A two-step fractionation of lignocellulosic residues of Phragmites australis in its main components (cellulose-pulp, soluble hemicellulose sugars, and lignin) is described, based on the biomass-derived solvent γ-valerolactone (GVL). The solvent used is an excellent substitute for traditional organic solvents as it is not toxic, it is renewable, and it can be recycled after the extraction process. Prior the GVL-organosolv extraction process, a steam explosion pretreatment was performed in order to break up the tight lignocellulosic structure and partially depolymerise hemicellulose into soluble sugars, making lignin easier to be solubilised. Three common extraction techniques were compared: soxhlet, closed vessel microwave-assisted, and open vessel on a hotplate stirrer. The two-step approach resulted in a cellulose-rich solid, water-soluble hemicellulose sugars and lignin-rich GVL liquor which was further purified for lignin isolation. The two best resulting pulps presented a high cellulose content (75.47% and 78.68%) starting from 38.13% and a content of lignin down to 11.96% and 13.09% starting from 23.02%. Almost all hemicellulose was removed with a final content of 0.72% and 2.20% starting from 20.5%.

Seeing biomass recalcitrance through fluorescence

Lignocellulosic biomass is the only renewable carbon resource available in sufficient amount on Earth to go beyond the fossil-based carbon economy. Its transformation requires controlled breakdown of polymers into a set of molecules to make fuels, chemicals and materials. But biomass is a network of various inter-connected polymers which are very difficult to deconstruct optimally. In particular, saccharification potential of lignocellulosic biomass depends on several complex chemical and physical factors. For the first time, an easily measurable fluorescence properties of steam-exploded biomass samples from miscanthus, poplar and wheat straw was shown to be directly correlated to their saccharification potential. Fluorescence can thus be advantageously used as a predictive method of biomass saccharification. The loss in fluorescence occurring after the steam explosion pretreatment and increasing with pretreatment severity does not originate from the loss in lignin content, but rather from a decrease of the lignin β-aryl-ether linkage content. Fluorescence lifetime analysis demonstrates that monolignols making lignin become highly conjugated after steam explosion pretreatment. These results reveal that lignin chemical composition is a more important feature to consider than its content to understand and to predict biomass saccharification.

Corn stover for biogas production: Effect of steam explosion pretreatment on the gas yields and on the biodegradation kinetics of the primary structural compounds

This study evaluated the effect of steam explosion on the chemical composition and biomethane potential of corn stover using temperatures ranging between 140 and 220°C and pretreatment times ranging between 2 and 15min. Biodegradation kinetics during the anaerobic digestion of untreated and corn stover, pretreated at two different intensities, 140°C for 5min and 180°C for 5min, were studied in tandem. Results showed that pretreatment at 160°C for 2min improved the methane yield by 22%. Harsher pretreatment conditions led to lower hemicellulose contents and methane yields, as well as higher lignin contents, which may be due to the formation of pseudo-lignin. The biodegradation kinetics trial demonstrated that steam explosion enhances the degradation of structural carbohydrates and acid insoluble lignin.

Optimization of bioethanol production from steam exploded hornbeam wood ( Ostrya carpinifolia ) by enzymatic hydrolysis

Abstract In this paper, the second generation pathway for bioethanol from hornbeam residues was investigated, in order to define the optimum operative conditions of steam explosion pretreatment and subsequently enzymatic hydrolysis maximizing the glucose amount for fermentation process. The whole experimental procedure was designed and analyzed by Response Surface Methodology, a statistic multivariate model that allows to investigate the effect of different parameters on a process and define the optimum values of these variables to optimize the response. The glucose yield from enzymatic hydrolysis was maximize as function of three variables: the severity factor of pretreatment (log R0), the total solids (TS%) of the enzymatic hydrolysis and enzyme loading (EL%) in the enzymatic hydrolysis stage. The Design of Experiment (DoE), based on central composite model, was characterized by 17 tests, varying the variables at five levels, log R0 (3.92, 4.08, 4.31, 4.54, 4.7), TS% (5, 7, 10, 13, 15), EL% (5, 7, 10, 13, 15). The optimization allows to define the best operative condition that is log R0 = 3.97, TS% = 6, EL% = 15 which leads to an overall fermentable sugars yield of 67.8% respect to the initial sugars content in the raw material that corresponds to a theoretical amount of producible ethanol of 251 L/ton dry raw material.

Evaluation of lignins from side-streams generated in an olive tree pruning-based biorefinery: Bioethanol production and alkaline pulping

In modern lignocellulosic-based biorefineries, carbohydrates can be transformed into biofuels and pulp and paper, whereas lignin is burned to obtain energy. However, a part of lignin could be converted into value-added products including bio-based aromatic chemicals, as well as building blocks for materials. Then, a good knowledge of lignin is necessary to define its valorisation procedure. This study characterized different lignins from side-streams produced from olive tree pruning bioethanol production (lignins collected from steam explosion pretreatment with water or phosphoric acid as catalysts, followed by simultaneous saccharification and fermentation process) and alkaline pulping (lignins recovered from kraft and soda-AQ black liquors). Together with the chemical composition, the structure of lignins was investigated by FTIR, 13C NMR, and 2D NMR. Bioethanol lignins had clearly distinct characteristics compared to pulping lignins; a certain number of side-chain linkages (mostly alkyl–aryl ether and resinol) accompanied with lower phenolic hydroxyls content. Bioethanol lignins also showed a significant amount of carbohydrates, mainly glucose and protein impurities. By contrast, pulping lignins revealed xylose together with a dramatical reduction of side-chains (some resinol linkages survive) and thereby higher phenol content, indicating rather severe lignin degradation during alkaline pulping processes. All lignins showed a predominance of syringyl units.

Effect of Steam Explosion Pretreatment Catalysed by Organic Acid and Alkali on Chemical and Structural Properties and Enzymatic Hydrolysis of Sugarcane Bagasse

This study researched the steam explosion effect catalysed by citric acid and sodium hydroxide on the chemical and structural properties of sugarcane bagasse and on the enzymatic hydrolysis process. Chemical and structural characterisation of raw and pretreated biomass was performed by reference methodologies for lignocellulosic materials, FTIR, XRD, TGA and SEM. Enzymatic hydrolysis was performed with a final volume of 20 mL consisting 3% sugarcane bagasse (dry weight), sodium citrate buffer 50 mM (pH = 5.0) and 1 g enzyme/100 g cellulose of Cellic® Cetec 3 enzyme complex. The total reducing sugars were determined by a 3,5-dinitrosalicilic acid method. In explosion pretreatment catalysed by citric acid, a biomass was obtained with a lesser amount of hemicelluloses (16.16%), a higher initial degradation temperature and formation of cracks in fibre cell wall. Pretreated bagasse by NaOH steam explosion showed complete destructuring of fibre, lignin removal of 65% and hemicellulosic fraction preservation. Sugarcane bagasse obtained after NaOH steam explosion showed the highest production of reducing sugars (9.07 g L−1), which can be attributed to greater exposure of carbohydrate fraction promoted by lignin removal, since these parameters showed a strong negative correlation (r = −0.99, p < 0.05).

High Mechanical Performance Boards Made from Fibers of Arundo donax without Added Adhesives

Arundo donax is a cane species with high growing productivity, and it is becoming an important source of biomass. The main objective of this study was to obtain fibreboards with high mechanical performance from A. donax without any added adhesive. Boards made without adhesive are free from formaldehyde emissions and consume no fossil resources. The characteristics of the obtained boards depended on the original material, steam explosion pre-treatments, and forming conditions (pressure, temperature, and pressing time). Production parameters were optimized. The effect of forming pressure on the physical and mechanical properties density, elastic modulus (MOE), modulus of rupture (MOR), tensile strength perpendicular to the faces (IB), thickness swelling, and water absorption of the obtained boards was studied. The European Norms (EN) methodologies were used to test the board specifications. Density, MOE, and MOR were modelled by a double reciprocal function. TS and WA were modelled with a reciprocal function in X. The boards obtained met and sometimes exceeded the requirements of these standards for the most demanding structural use.

Effect of steam explosion pre-treatment on molecular structure of sweet potato starch

Purpose: To examine the effect of steam-explosion (SE) strength on the molecular structure of sweet potato starch.Methods: Sweet potato starch was pre-treated using SE method. The effects of SE pressure and pressure-holding time on the molecular structure of the sweet potato starch were investigated by gel chromatography (GPC), infrared spectroscopy, and grading analysis.Results: The molecular weight (MW) of the starch pre-treated by SE technology decreased with increasing explosion pressure and pressure-holding time; however, the individual MW of amylopectin and amylose declined from 439,834 and 6578 to 238,603 and 4845, respectively. Furthermore, the peak area ratio (obtained by GPC) of amylopectin decreased from 84.39 to 65.16 % while that of amylose increased from 15.61 to 34.84 %. No new absorption peaks were found in the infrared spectra of sweet potato starch following SE pre-treatment. Crystallization index and median diameter of sweet potato starch increased from 1.661 to 1.959 and from 13.73 μm to 76.36 μm, respectively, with rising pressure and pressure-holding time, following SE pre-treatment.Conclusion: SE pre-treatment effectively degrades the degree of polymerisation of molecular chains in sweet potato starch and enhances the degree of crystallinity thereof. SE method is an approach for the production of sweet potato starch with high-level anti-digestion characteristics.Keywords: Sweet potato starch, Steam-explosion, Molecular weight, Degree of crystallinity, Particle diameter

Saccharification Performances of Miscanthus at the Pilot and Miniaturized Assay Scales: Genotype and Year Variabilities According to the Biomass Composition.

HIGHLIGHTS Biomass production and cell wall composition are differentially impacted by harvesting year and genotypes, influencing then cellulose conversion in miniaturized assay.Using a high-throughput miniaturized and semi-automated method for performing the pretreatment and saccharification steps at laboratory scale allows for the assessment of these factors on the biomass potential for producing bioethanol before moving to the industrial scale.The large genetic diversity of the perennial grass miscanthus makes it suitable for producing cellulosic ethanol in biorefineries. The saccharification potential and year variability of five genotypes belonging to Miscanthus × giganteus and Miscanthus sinensis were explored using a miniaturized and semi-automated method, allowing the application of a hot water treatment followed by an enzymatic hydrolysis. The studied genotypes highlighted distinct cellulose conversion yields due to their distinct cell wall compositions. An inter-year comparison revealed significant variations in the biomass productivity and cell wall compositions. Compared to the recalcitrant genotypes, more digestible genotypes contained higher amounts of hemicellulosic carbohydrates and lower amounts of cellulose and lignin. In contrast to hemicellulosic carbohydrates, the relationships analysis between the biomass traits and cellulose conversion clearly showed the same negative effect of cellulose and lignin on cellulose digestion. The miniaturized and semi-automated method we developed was usable at the laboratory scale and was reliable for mimicking the saccharification at the pilot scale using a steam explosion pretreatment and enzymatic hydrolysis. Therefore, this miniaturized method will allow the reliable screening of many genotypes for saccharification potential. These findings provide valuable information and tools for breeders to create genotypes combining high yield, suitable biomass composition, and high saccharification yields.

Pilot-scale steam explosion pretreatment with 2-naphthol to overcome high softwood recalcitrance

BackgroundSteam explosion pretreatment has been examined in many studies for enhancing the enzymatic digestibility of lignocellulosic biomass and is currently the most common pretreatment method in commercial biorefineries. It is however not effective for overcoming the extremely high recalcitrance of softwood to biochemical conversion. Recent fundamental research in small-scale liquid hot water pretreatment has shown, though, that the addition of a carbocation scavenger like 2-naphthol can prevent lignin repolymerization and thus enhance the enzymatic digestibility of softwood cellulose. This work studies the technical application potential of this approach in a larger steam explosion pilot plant for surmounting softwood recalcitrance.ResultsThe addition of 35.36 g 2-naphthol to the steam explosion pretreatment of 1.5 kg spruce wood chips allowed to considerably enhance the enzymatic cellulose digestibility. Different ways of adding the solid 2-naphthol to steam pretreatment were tested. Mixing with the biomass before pretreatment could enhance digestibility by up to 55% compared to control experiments. Impregnation of the biomass with 2-naphthol was yet more effective. Acetone and ethanol were tested to dissolve 2-naphthol and impregnate the biomass. The solvents were then removed again by evaporation before the pretreatment. The impregnation allowed to enhance digestibility by up to 179 and 192%, respectively. A comparison to prevalent acid-catalyzed steam explosion pretreatments for softwood revealed that the scavenger approach allows for obtaining exceptionally high yields in enzymatic hydrolysis. The biomass impregnation with 2-naphthol even renders a complete enzymatic cellulose conversion possible, which is remarkable for a softwood pretreatment not removing lignin. Steam pretreatment experiments without explosive decompression revealed that the enhancing effects of the explosion and the scavenger complement each other well. The explosion enhances the accessibility of the cellulose while the use of the scavenger reduces particularly the deactivation of enzymes.ConclusionsThis is the first study to show that a carbocation scavenger in steam pretreatment can enhance the enzymatic digestibility of lignocellulosic biomass. The approach opens up a novel possibility for overcoming the high softwood recalcitrance in a process that does not require an acid catalyst or the removal of lignin from the biomass.

Producing bioethanol from pretreated-wood dust by simultaneous saccharification and co-fermentation process

Abstract The aim of this study was to utilize a new and highly effective bioreactor system, i.e., simultaneous saccharification and fermentation (SSCF), for bioethanol production by the cocultivation of Trichoderma reesei, Aspergillus niger, and Zymomonas mobilis by using a direct conversion process of pretreated-wood dust medium. Wood dust has been effectively used to obtain reducing sugars (glucose, xylose, and other byproducts) through the use of either a supercritical fluid extraction (SFE) or steam explosion (SE) pretreatment step. In addition, experimental results showed that polyurethane as a porous carrier could enhance total saccharification enzyme activity at an inoculum proportion of 1/1 of T. reesei, and A. niger and at a total inoculum concentration of 6.5 × 106 spores/ml. Furthermore, the concentration of alginate beads (3%) and immobilized proportion of Z. mobilis to alginate beads (1:4) were also examined. In accordance with previous reports, bioethanol production was carried out in a SSCF bioreactor by the cocultivation of T. reesei and A. niger in the polyurethane carrier and Z. mobilis immobilized in alginate beads using pretreated-wood dust medium. Experimental results revealed that, after 24 h of cultivation, the yield of bioethanol produced using pretreated-wood dust medium (1%) were 0.069 g/g and 0.049 g/g, for SFE and SE, respectively. Meanwhile, the sugar conversion rate reached 20.72% and 24.39% for SFE and SE, respectively. Thus, the results of this study show that pretreated-wood dust medium has significant potential for use in bioethanol production.

A Sequential Steam Explosion and Reactive Extrusion Pretreatment for Lignocellulosic Biomass Conversion within a Fermentation-Based Biorefinery Perspective

The present work evaluates a two-step pretreatment process based on steam explosion and extrusion technologies for the optimal fractionation of lignocellulosic biomass. Two-step pretreatment of barley straw resulted in overall glucan, hemicellulose and lignin recovery yields of 84%, 91% and 87%, respectively. Precipitation of the collected lignin-rich liquid fraction yielded a solid residue with high lignin content, offering possibilities for subsequent applications. Moreover, hydrolysability tests showed almost complete saccharification of the pretreated solid residue, which when combined with the low concentration of the generated inhibitory compounds, is representative of a good pretreatment approach. Scheffersomyces stipitis was capable of fermenting all of the glucose and xylose from the non-diluted hemicellulose fraction, resulting in an ethanol concentration of 17.5 g/L with 0.34 g/g yields. Similarly, Saccharomyces cerevisiae produced about 4% (v/v) ethanol concentration with 0.40 g/g yields, during simultaneous saccharification and fermentation (SSF) of the two-step pretreated solid residue at 10% (w/w) consistency. These results increased the overall conversion yields from a one-step steam explosion pretreatment by 1.4-fold, showing the effectiveness of including an extrusion step to enhance overall biomass fractionation and carbohydrates conversion via microbial fermentation processes.

An innovative way for the delignification of Phragmites australis residues by steam explosion and γ‐valerolactone microwave assisted extraction

This work aimed at optimizing the conditions for lignin removal in Phragmites australis processing residues from the manufacturing of local handicrafts. The delignification consisted of a double step treatment. The first step was represented by steam explosion (SE) pretreatment for the deconstruction of the lignocellulosic matrix and solubilization of the hemicelluloses to enhance the subsequent lignin extraction. The second step consisted in the organosolv extraction of lignin from the steam‐pretreated P. australis by microwave assisted extraction (MAE) using green solvent γ‐valerolactone. The optimization was carried out using design of experiments and response surface methodology generating a central composite design. The investigated factors were the severity factor (log R0) for the SE pretreatment and time and temperature for the MAE treatment. The processes led to a cellulose‐rich pulp with a delignification of 75%. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 736–741, 2017

Optimal conditions of acid‐catalysed steam explosion pretreatment of banana lignocellulosic biomass for fermentable sugar production

AbstractBACKGROUNDBanana is one of the most cultivated fruit crops around the world. After its harvest, it generates large amounts of agricultural wastes. The objective of this study was to optimise the operational conditions of steam explosion pretreatment of the two main banana lignocellulosic residues, rachis and pseudostem, in order to achieve high overall sugar yields.RESULTSA response surface statistical model (22 + star points with triplicate at central point) was used for the optimisation, considering the enzymatic hydrolysis yield and the overall yield of glucose and xylose as main criteria. The optimal conditions of steam explosion pretreatment for pseudostem were established at 177 °C, 5 min and 2.2% H2SO4 (v/v), presenting a high overall glucose yield of 91.0%. For rachis, the optimal conditions were 198 °C, 5 min and 1.5% H2SO4 (v/v) with an overall glucose yield of 87.1%.CONCLUSIONOptimal conditions for steam explosion pretreatment of agricultural banana wastes were determined. An acid‐catalysed pretreatment was needed due to the low presence of acetyl groups in both feedstocks. After rachis pretreatment, extractives, soluble ashes and hemicellulose were solubilised causing an enrichment of cellulose in the insoluble fraction. However, due to the high amount of starch in pseudostem, a significant amount of glucose was recovered in the liquid fraction. © 2017 Society of Chemical Industry