Steam Explosion Pretreatment Research Articles

Cellulosic sugars from biomass: Effect of acid presoaking on pretreatment efficiency and operating cost estimation for sugar production

A room temperature acid presoaking process with high mixing performance was developed to enhance the acid-catalyzed steam explosion pretreatment efficiency. The impact of the operational parameters of presoaking, such as presoaking time, acid concentration and acid solution recycling, on the acid-catalyzed pretreatment of rice straw, bagasse and wood chip was studied. Bench-scale investigations show that the maximum saccharification yields after acid-catalyzed steam explosion of rice straw, bagasse and wood chip were 90.8%, 81.1% and 80.3%, corresponding to 535, 536 and 537 kg sugar/ton of dry raw material, respectively. According to the results, the estimated operating costs of sugar production from high to low are 0.388, 0.378 and 0.314 US $/kg sugar for rice straw, sugarcane bagasse and wood chip, respectively. The results indicate that the recyclable and continuous pilot-scale presoaking system with reliable acid uptake control shows high potential for producing sugar from different lignocellulosic biomass.

Steam explosion pretreatment of rice straw to improve structural carbohydrates anaerobic digestibility for biomethanation.

Effectiveness of steam explosion (SE) pretreatment for deconstructing the complex structural carbohydrates (SC) and lignin recalcitrance properties of rice straw (RS) for conjunctive improvement of biofuel yield and waste valorization was evaluated. This work exhibited successful pretreatment of RS at a different pressure (1.2, 1.5, and 1.8MPa) and retention (3, 6, 9, and 12min) for enhancement of SC contribution to biomethane production. Regression analysis demonstrated that SE pretreatment efficiency improved at high-temperature and short-retention time for biodegradation of RS. Maximum cumulative methane yield (EMY) achieved 254.8mL/gvs at 1.2MPa (3min) of SE-treated RS with 62.7% of very significant improvement compared with untreated RS (156.6mL/gvs). Furthermore, solid fraction of xylose, arabinose, cellobiose, glucose, and acid-soluble lignin in SE-treated RS of 1.2MPa (3min) were biodegraded by 27.4%, 46.4%, 100%, 48.8%, and 14.1%, respectively, after anaerobic digestion. Therefore, SE pretreatment was an encouraging approach for enhancing SC conversion to biomethane and waste resource to circular economy.

Preparation and Properties of Jute Fiber Long-Chain Fatty Acid Esters in Supercritical Carbon Dioxide.

A two-step method involving continuous screw-extrusion steam explosion (CSESE) pretreatment and esterification in supercritical carbon dioxide (scCO2) is used to prepare long-chain fatty acid-modified jute fiber. The weight gain percentage (WG %) of CSESE-pretreated jute laurate (JL) was 110.7% when esterification was carried out in scCO2 at 14 MPa and 100 °C for 2 h. The corresponding WG % was 105.5% when esterification was instead carried out in pyridine at 100 °C for 2 h. Scanning electron microscopy and X-ray diffraction indicated that CSESE pretreatment enhanced the reactivity of jute fiber, with esterification in scCO2 simultaneously occurring on the fibers surface and internal walls. The glass transition temperature of esterified jute was approximately 119 °C, indicating that it could be hot processed over a wide temperature range. The esterified jute had an oil absorption ratio of 17.01 g/g, so it can be used as an oil absorption material.

Steam-exploded sugarcane bagasse as a potential beef cattle feedstock: effects of different pretreatment conditions1.

Sugarcane bagasse, a lignocellulosic biomass produced by sugar production, is rarely utilized directly due to economic concerns. However, pretreatment of this biomass could make it suitable as a feedstock for the beef cattle industry. Accordingly, this study investigated the effects of different steam explosion conditions on bagasse digestibility using in vitro fermentation techniques, scanning electron microscopy, and detailed chemical analyses. In vitro incubation of an untreated sample and samples pretreated at 6 different pressures ranging from 0.6 to 1.6 MPa at intervals of 0.2 MPa for 5 min was conducted out for 96 h. Results showed that increasing the pressure in the steam explosion pretreatment induced degradation of the hemicellulose and increased soluble sugar content, especially for arabinose (L; P < 0.01) and xylose contents (Q; P < 0.01). In vitro incubation showed that compared with untreated bagasse, gas production and degradation rate of the bagasse improved linearly (L; P < 0.01) after all treatments. The lag time disappeared with steam pressure above 1.0 MPa and the maximum gas production was obtained under pretreatment at 1.4 MPa for 5 min. Furthermore, pretreatment of bagasse by steam explosion enhanced (Q: P < 0.01) quadratically estimated energy values and OM digestibility. Thus, the current results demonstrate that sugarcane bagasse may be effectively used as a potential beef cattle feedstock after steam explosion pretreatment.

Nitrogen explosive decompression pre-treatment: An alternative to steam explosion

When using the novel N2 explosive decompression pre-treatment, its effect was investigated in relation to the biomass structure and chemical processes during the treatment process. The results that were gained from this testing were compared to those for the widely-used steam explosion pre-treatment method in order to be able to present the advantages in using each method. Both methods are economically and environmentally attractive since only the pressure and water or steam are used to break down the biomass structure.Two pre-treatment methods were used at different temperatures and samples from various process steps were analysed. The results were used to assess the pre-treatment effect and the chemical changes in the biomass and, finally, mass balances were compiled for the bioethanol process at different process steps.The results show that the highest glucose and ethanol yields were obtained by means of the steam explosion pre-treatment method at a temperature of 200 °C (24.29 g and 12.72 g for 100 g of biomass respectively), and at 175 °C (15.4 g and 9.0 g for 100 g of biomass respectively). At lower temperatures the nitrogen explosion treatment produced better yields.

Towards sustainable thermoplastic woody materials prepared from continuous steam explosion followed by oxidation-reduction

Converting plant fibers into thermoplastic materials are challenging in a sustainable society. Herein, continuous steam explosion pretreatment was used to improve the reactivity of plant fiber. Meanwhile, periodate oxidation and subsequent sodium borohydride reduction were used to plastify plant fiber. SEM and BET results showed that steam explosion pretreatment can gradually dissociate bundle structure of eucalyptus fiber and increase its specific surface area, which improve the reaction efficiency significantly. The FTIR and NMR indicated that the eucalyptus fiber had been successfully oxidized and reduced. XRD and TGA tests showed that the crystallinity and thermal stability of the modified fibers decreased with the increase of oxidation time. When the oxidation time is 8 h, the mechanical properties of the modified material are optimal, and the glass transition temperature is significantly reduced. These results suggest that this all-component plant fiber material is a possible alternative to petroleum-based materials.

Extraction and characterization of lignin from corncob residue after acid-catalyzed steam explosion pretreatment

Corncob residue after acid catalyzed steam explosion (CRSE) is rich in cellulose and lignin. However, the structure of the lignin present in the CRSE has not been studied in detail and this hinders its application. An enzymatic mild acidolysis lignin (EMAL) extraction is adopted to process the CRSE where the extraction conditions are modified to improve lignin recovery and purity. Extraction severity factor is calculated and correlations between it and lignin recovery, lignin purity and total phenolic groups are evaluated. The best extraction condition produces lignin with a purity of 99.0% and a yield of 57.3%. A comparative study between lignin samples extracted under the best condition from the CRSE and untreated corncob (CC) is conducted. The structures of extracted lignin samples are investigated by using 31P NMR, 2D-HSQC NMR, FTIR and GPC. Although SE pretreatment caused degradation of lignin, the abundance per 100 aromatic units of β-O-4′ linkages is 46.0, which is higher than most technical lignins. The molecular weight of CRSE EMAL is found to be higher than that of CC EMAL due to condensation reactions. Antioxidant property of CC EMAL and CRSE EMAL is measured and compared. The data shows that CRSE EMAL possesses better antioxidant activity (IC50 = 128 μg/mL) than CC EMAL (IC50 = 238 μg/mL), which makes CRSE EMAL an ideal additive for polymer composites.

Two-stage steam explosion pretreatment of softwood with 2-naphthol as carbocation scavenger

Background Lignocellulosic biomass is considered as a potential source for sustainable biofuels. In the conversion process, a pretreatment step is necessary in order to overcome the biomass recalcitrance and allow for sufficient fermentable sugar yields in enzymatic hydrolysis. Steam explosion is a well known pretreatment method working without additional chemicals and allowing for efficient particle size reduction. However, it is not effective for the pretreatment of softwood and the harsh conditions necessary to achieve a highly digestible cellulose fraction lead to the partial degradation of the hemicellulosic sugars. Previous studies showed that the autohydrolysis pretreatreatment of softwood can benefit from the addition of 2-naphthol. This carbocation scavenger prevents lignin repolymerisation leading to an enhanced glucose yield in the subsequent enzymatic hydrolysis.Results In order to prevent the degradation of the hemicellulose, we investigated in this study a two-stage 2-naphthol steam explosion pretreatment. In the first stage, spruce wood is pretreated at a severity which is optimal for the autocatalytic hydrolysis of the hemicellulose. The hydrolyzate containing the solubilized sugars is withdrawn from the reactor and the remaining solids are pretreated with different amounts of 2-naphthol in a second stage at a severity that allows for high glucose yields in enzymatic hydrolysis. The pretreated spruce was subjected to enzymatic hydrolysis and to simultaneous saccharification and fermentation (SSF). In the first stage, the maximal yield of hemicellulosic sugars was 47.5% at a pretreatment severity of log R_0 = 3.75 at 180 °C. In the second stage, a 2-naphthol dosage of 0.205 mol/mol lignin C9-unit increased the ethanol yield in SSF with a cellulose loading of 1% using the whole second stage pretreatment slurry by 17% from 73.6% for the control without 2-naphthol to 90.4%. At a higher solid loading corresponding to 5% w/w cellulose, the yields decreased due to higher concentrations of residual 2-naphthol in the biomass and the pretreatment liquor, but also due to higher concentrations of potential inhibitors like HMF, furfural and acetic acid. Experiments with washed solids, vacuum filtered solids and the whole slurry showed that residual 2-naphthol can inhibit the fermentation as a single inhibitor but also synergistically together with HMF, furfural and acetic acid.Conclusions This work shows that a two-stage pretreatment greatly enhances the recovery of hemicellulosic sugars from spruce wood. The presence of 2-naphthol in the second pretreatment stage can enhance the ethanol yield in SSF of steam explosion pretreated softwood at low cellulose concentrations of 1% w/w. However, with higher solid loadings of 5% w/w cellulose, the ethanol yields were in general lower due to the solid effect and a synergistic inhibition of HMF, furfural, acetic acid with residual 2-naphthol. The concentration of residual 2-naphthol tolerated by the yeast decreased with increasing concentrations of HMF, furfural, and acetic acid.

Application of steam explosion in oil extraction of camellia seed (Camellia oleifera Abel.) and evaluation of its physicochemical properties, fatty acid, and antioxidant activities.

This study evaluated the physicochemical properties of oils extracted from steam‐exploded camellia seed (Camellia oleifera Abel.). Steam pressure, resident time, fatty acid composition, total phenolics, tocopherol, squalene, and sterol contents, and volatile compounds were determined. 1H NMR and FTIR spectra were performed for the structure of camellia seed oil. This study has found the highest yield of oil was 86.56% and was obtained when steam explosion pretreatment was at 1.6 MPa 30 s. Oil extracted by steam explosion pretreatment exhibited favorable physicochemical properties and stronger antioxidant activities compared to untreated oil. The compositions of fatty acid were similar between treated and untreated camellia seed oil. According to the 1H NMR and FTIR analyses, the functional groups of the oils were not significantly affected by the steam explosion pretreatment. Furans such as 2‐pentyl‐furan, 2‐furanmethanol, and 3‐methyl‐furan were produced from stream‐exploded camellia seed. Scanning electron microscopy revealed that steam explosion pretreatment efficiently promoted the release of oil by destroying the cell structure of camellia seed. Therefore, steam explosion can be an effective method for the camellia seed oil extraction.

Enhanced enzymatic hydrolysis and methane production from rubber wood waste using steam explosion

Rubber wood waste (RW) requires due to its recalcitrance a pretreatment step before efficient biochemical conversion is possible. Non chemical steam explosion pretreatment was adopted to enhance enzymatic hydrolysis and anaerobic digestion with severity from 2.70 to 4.35. RW treated at severity 4.35 (214 °C for 10 min) gave the highest 83.9 L CH4/kgVS effectiveness in anaerobic digestibility together with 45.2% hydrolysability in terms of glucan conversion. The intense pretreatment decreased particle size and degraded most of the hemicellulose, resulting in increased specific surface and better access for enzymes to cellulose. Additionally, the energy yield of steam exploded RW was enhanced by combined enzymatic hydrolysis with anaerobic digestion, in comparison to enzymatic hydrolysis or anaerobic digestion alone. This allowed for an efficient steam explosion pretreatment with co-production of sugar and methane. This study provides a technical approach for efficient biofuel production from RW after steam explosion pretreatment. Valorization of lignin-rich residue generated from the integrated process may increase value of RW, but assessing this requires further study.

Analysis on the performance of hot water extraction and alkaline extraction for sodium hydroxide-assisted steam exploded empty fruit bunch at pilot scale

Empty fruit bunches (EFB) contribute the most to the biomass waste produced from palm oil industries. Biomass waste is made up of cellulose, hemicellulose, and lignin. By having high cellulose content, it has great potential for cellulose production. However, the cellulose extraction process has yet to be optimized. Therefore, the study on the operating conditions in extracting cellulose from EFB takes place by understanding the sodium hydroxide (NaOH) soaking process prior to steam explosion pre-treatment. The effects of retention time on the hot water extraction (HWE) treatment and NaOH concentration on the alkaline extraction (AE) treatment in term of the amount of dissolved sugar were observed. The chemical properties of original fibre and treated fibre were analysed by Fourier Transform Infrared (FTIR) Spectroscopy and the surface morphology were observed using scanning electron microscopy (SEM). In this study, it is found that the best condition for alkaline extraction was at 10% alkaline concentration and the FTIR spectroscopy shows that there a no changes on the chemical structure of the fibre. SEM also shows the changes on the surface morphology of the fibre. Showing that the sodium hydroxide assisted steam explosion pre-treatment does greatly influence the further process

Optimization of the Steam Explosion Pretreatment Effect on Total Flavonoids Content and Antioxidative Activity of Seabuckthom Pomace by Response Surface Methodology.

Steam explosion pretreatment was conducted on seabuckthom pomace. Response surface methodology was used to optimize the treatment conditions of steam explosion, including steam pressure, duration and particle size. After this, the content of total flavonoids and the antioxidant capacity of total flavonoids were investigated. Results showed that when the steam pressure was 2.0 MPa, duration was 88 s and a sieving mesh size was 60, the total flavonoids content in seabuckthorm reached a maximum of 24.74 ± 0.71 mg CAE/g, an increase of 246% compared with that without steam explosion treatment (7.14 ± 0.42 mg CAE/g). Also, DPPH and ·OH free radical scavenging ability showed significant improvement, with an IC50 decrease to 13.53 μg/mL and 4.32 μg/mL, respectively, far lower than that in original samples. Through the scanning electron microscope, the surface of seabuckthom pomace after steam explosion was crinkled, curly, and holey. Our study showed that the content of total flavonoids in seabuckthom pomace could be obviously promoted and the antioxidant capacity of total flavonoids also improved significantly, after applying steam explosion pretreatment to seabuckthom pomace, making this approach meaningful for the reuse of seabuckthom pomace resources.

Pretreatment of switchgrass by steam explosion in a semi-continuous pre-pilot reactor

Switchgrass (Panicum virgatum) is a perennial grass highly valued as an energy crop resource for the production of bioethanol due to its high carbohydrate content, fast growth, and ability to grow in lands that cannot support crop or food production. In the present study, this biomass was submitted to steam explosion pretreatment in a semi-continuous pre-pilot reactor with the aim of obtaining a pretreated solid with high digestibility for enzymatic hydrolysis. Different conditions of temperature (170–200 °C) and residence time (5–15 min), leading to different severity factors (2.76–4.12) were used for steam explosion pretreatment, which were combined through a 22 central composite design. The results revealed that both variables had great influence in the process, affecting both the biomass structure and the saccharification yield, as a consequence. However, in the range of values evaluated in this study, the effect of the temperature was more prominent than the effect of the residence time. The best saccharification yield (88.3%) was obtained when using the biomass pretreated at 200 °C for 10 min. Similar result was obtained using a commercial cellulose pulp as feedstock for enzymatic hydrolysis, confirming that the best conditions for switchgrass pretreatment in the pre-pilot scale were successfully established.

Production of phenols from pyrolysis of sugarcane bagasse lignin: Catalyst screening using thermogravimetric analysis – Thermal desorption – Gas chromatography – Mass spectroscopy

The structural nature of lignin renders it suitable as a renewable source of phenolic compounds. The production of phenols from pyrolysis of sugarcane lignins with impregnated catalysts was investigated by screening of twelve catalysts (Al2O3, CaO, Fe2O3, TiO2, ZnO, MgO, CuO, MoO3, NiO, Ni/Al2O3-SiO2, NaOH, and KOH) at 1 wt.% content. Sugarcane bagasse lignins were isolated after soda-pulping (SD), soda-anthraquinone-pulping (SAQ) and steam explosion pre-treatment followed by enzymatic hydrolysis (SEH). Pyrolysis was conducted using a thermogravimetric analyser (TGA), and captured volatiles were quantified by thermal desorption (TD) gas chromatography–mass spectroscopy (GC–MS). The TGA results showed that the degradation profiles and char yields were influenced by the presence of catalysts, through modifications in conversion mechanisms. The highest increases in the total yield of phenols were obtained with KOH for SD lignin (+25.7%), CaO for SAQ lignin (+59.7%), and Fe2O3 for SEH lignin (+43.0%). Due to the enhancement of depolymerisation at low temperature (<350 °C), the yields of syringol, guaiacol, and vinylguaiacol increased by 41%, 32%, and 43% for SD lignin, 121%, 93%, and 84% for SAQ lignin, and 72%, 77%, and 54% for SEH lignin respectively. These significant increases in the yields of phenols using 1 wt.% compared to ≥10 wt.% reported in literatures demonstrated the effectiveness of impregnation method.

Effects of one-step alkaline and two-step alkaline/dilute acid and alkaline/steam explosion pretreatments on the structure of isolated pine lignin

Biological valorization of biomass most often depends on the efficient reduction of plant cell wall recalcitrance and conversion of lignin – the most recalcitrant constituent – to fuels, chemicals and/or value-added substances. Lignin conversion to fuels and value-added chemicals requires a sound understanding of the structure of lignin before and after different pretreatments. In the current work, an effort has been made to compare the structural differences in isolated pine lignin after one- (alkaline) and two-step (alkaline/dilute acid and alkaline/steam explosion) pretreatments. Our results indicate removal of the low molecular weight fraction of lignin after an initial alkaline pretreatment. A subsequent dilute acid pretreatment resulted in the loss of lignin inter-unit linkages such as β-O-4’ aryl ethers. However, with a steam explosion pretreatment, lignin exhibited a competing condensation process leading to increased condensed lignin structures.

Effect of steam explosion on the structural modification of rice straw for enhanced biodegradation and biogas production

The goal of this study was to develop an operational steam explosion pretreatment for effective modification of rice straw chemical structure in order to improve its biodegradability and methane yield. The parameters of pressure (5 bar to 15 bar), moisture (0% to 70%), and time (1 min to 15 min) were studied in steam explosion pretreatment. The steam explosion efficiency was investigated according to the changes in crystallinity structure and chemical composition on rice straw, as well as the methane yield from straw. Steam explosion changed the structure linkages between the lignin and carbohydrate, which was indicated by a reduction in the peak intensities in the bonds from 1648 cm-1 to 1516 cm-1. After pretreatment, the crystallinity index of the rice straw in the 10 bar-10 min cycle with no moisture and 15 bar-10 min cycle with 70% moisture increased from 22.9% to 28.3% and 28.6%, respectively. Steam explosion efficiently decreased the lignin. The highest reduction in the amount of lignin was observed with the 10 bar-10 min cycle, which reached from 18.6% to 13.0%. The methane yield increased with the cycles 10 bar-10 min and 15 bar-15 min with 35% moisture, and 15 bar-10 min with 70% moisture by 113%, 104%, and 147% compared to that of the untreated straw, respectively. Moreover, the highest biodegradation percent of the rice straw was obtained in these cycles.

Steam Explosion of Beech Wood: Effect of the Particle Size on the Xylans Recovery

In this work, the effect of particle size and severity factors was investigated to find the optimum condition of steam explosion pretreatment on xylan recovery of beech wood. The beech wood particles with sizes of 0.16, 1, or 2 mm were steamed at 150–210 °C for 2.5–15 min before an explosive decompression. The results showed that the maximum xylan recovery was about 10% w/w wood with low concentrations of the inhibitors, which were obtained when the particle size is 1 mm and R0 = 3.65 (190 °C, 10 min). The smallest particle size may result in overcooking of biomass, leads to easily and high degradation of hemicelluloses sugars, whereas the largest particle sizes may result in incomplete autohydrolysis in biomass and lower extractability of hemicelluloses sugars. The obtained optimum condition for xylan recovery will improve the subsequent utilization (such as in food industry and other chemical products), prior to subsequent transformation of steam explosion pretreated wood (bioethanol and pellet).

Lignin-first biomass fractionation using a hybrid organosolv – Steam explosion pretreatment technology improves the saccharification and fermentability of spruce biomass

For a transition to a sustainable society, fuels, chemicals, and materials should be produced from renewable resources. Lignocellulosic biomass constitutes an abundant and renewable feedstock; however, its successful application in a biorefinery requires efficient fractionation into its components; cellulose, hemicellulose and lignin. Here, we demonstrate that a newly established hybrid organosolv – steam explosion pretreatment can effectively fractionate spruce biomass to yield pretreated solids with high cellulose (72% w/w) and low lignin (delignification up to 79.4% w/w) content. The cellulose-rich pretreated solids present high saccharification yields (up to 61% w/w) making them ideal for subsequent bioconversion processes. Moreover, under high-gravity conditions (22% w/w) we obtained an ethanol titer of 61.7 g/L, the highest so far reported for spruce biomass. Finally, the obtained high-purity lignin is suitable for various advanced applications. In conclusion, hybrid organosolv pretreatment could offer a closed-loop biorefinery while simultaneously adding value to all biomass components.

Equilibrium, kinetics and thermodynamics of Cu(II) biosorption on Chinese chestnut shell pretreated with steam explosion.

The shells of Chinese chestnuts (Castanea mollissima) are an agricultural residue. This work aimed to evaluate this feasibility of using steam explosion to modify this residue for Cu(II) biosorption from aqueous solutions. Equilibrium, kinetic and thermodynamic parameters were evaluated. The steam-explosion pretreatment increased the surface area of the chestnut shell and exposed more hydroxyl and carboxyl groups, which are binding sites for Cu(II). It changed the sorption from a spontaneous process driven by enthalpy to a nonspontaneous one driven by entropy. It increased the Cu(II) sorption capacity at higher temperatures while it decreased the capacity at lower ones. Compared with untreated chestnut shell, the steam-exploded shell is preferable for Cu(II) sorption at higher temperatures.

Techno‐economic assessment of carboxylic acids, furfural, and pellet production in a pine sawdust biorefinery

AbstractPine sawdust is an important lignocellulosic waste from the primary industrialization of wood, and its valorization using the biorefinery concept could add new value chains to the forest industry. Compared with large‐scale biorefineries, small‐scale ones involve lower capital and logistics costs, lower risk, and can increase the use of labor in rural areas. A scheme was proposed for the use of the hemicelluloses obtained from the spent liquor of a steam explosion pretreatment of pine sawdust. With the proposed scheme, levulinic acid (LA), formic acid (FA), acetic acid and furfural are obtained from the liquid fraction while pellets are produced from the solid fraction. This pine sawdust biorefinery allows about 747 kg of pellets, 57 kg of LA, 23 kg of FA, 18 kg of acetic acid, and 22 kg of furfural per 1000 kg of dry sawdust to be obtained. The energy used for LA production is one of the main production costs. When 95% of the residual solid is used to generate steam, there is an improvement in the internal rate of return (IRR). The heat integration allows a reduction of 10% in the steam consumption for LA, increasing the capacity for pellet production. The results obtained are therefore essential when seeking alternatives for pine sawdust biorefineries, focusing on the improvement of the production processes, satisfaction of energy requirements, and the reduction of the recovery costs. Three alternatives for the valorization of pine sawdust were analyzed and the best of them obtained an IRR of about 17%. © 2018 Society of Chemical Industry and John Wiley &amp; Sons, Ltd