Hybrid Pretreatment Research Articles

Enzymatic pretreatment of steam-exploded birch wood for increased biogas production and lignin degradation

Lignocellulose is readily available biomass for biogas production; however, due to its rigid structure, it requires pretreatment to obtain a maximum energy extraction. In this study, steam explosion (SE) (220 °C and 10 minute retention time) has been employed to increase the biogas production potential from birch wood. Although the biogas production increased by over two times after SE, the SE of birch wood negatively affects the structure of C5/C6 sugars and doubled the concentration of non-degradable lignin in all the samples. In this work, SE birch wood has been further pretreated by novel lignin-degrading enzymes cocktail to convert lignin into degradable sugars and increase the biogas production rate. The proposed hybrid pretreatment could increase the biogas production by up to 25% (from 450.5 mL/g VS to 566 mL/g VS), and reduced the lignin concentration by up to 48%.

Methods of pretreatment and their impacts on anaerobic codigestion of multifeedstocks: A review.

Anaerobic codigestion (AnCoD) has attracted attention owing to its advantages over conventional anaerobic digestion, and attempts are still going on to develop methods for improving the efficiency of this technology. Mostly, addition of cosubstrates without applying a proper pretreatment cannot adequately enhance the performance of the digestion. However, there is a lack of a comprehensive study on different pretreatment methods specific to the wide range of cosubstrates. This review aimed to (i) categorize pretreatment techniques that have been developed for improving AnCoD, (ii) present the results of the studies on the effect of pretreatment on improving AnCoD, and (iii) provide a comparison between pretreatment methods and their application for different types of cosubstrates. The findings primarily validated the influence of pretreatment to enhance the process by increasing biodegradability, improved hydrolysis, reduced hydraulic retention time (HRT), and improved methane production. The five main categories of pretreatment employed in codigestion included the following: mechanical, thermal, chemical, biological, and hybrid pretreatment. Among them, mechanical and biological pretreatment have the most and least application in codigestion, respectively. Greater efforts are required on the application of biological pretreatment and cost-benefit analysis of different pretreatment options on the variety of the cosubstrates. PRACTITIONER POINTS: Pretreatment can significantly enhance biomethane production in anaerobic digestion Anaerobic codigestion along with pretreatment can further enhance the conventional anaerobic digestion of single feedstock Mechanical and biological methods have been the most and least practiced pretreatment options Selection of applicable pretreatment option to enhance methane production is subject to the type of cosubstrates in the system There is a research gap in evaluating the application of biological pretreatment for various types of cosubstrates.

Innovative hybrid strategy for efficient production of high-quality freeze-dried instant noodles: Combination of laser with leavening agent

The present study was carried out to improve the drying efficiency and quality of freeze-dried instant noodles by a novel hybrid pretreatment method that combines laser puncturing along with use of a leavening agent mixture. The influence of several variants of this combined treatment on drying time, energy consumption, rehydration behavior and pasting properties of dried noodles as well as the quality parameters of soaked noodles were examined. Results demonstrate that the intervention of laser puncturing treatment and the addition of leavening agent mixture are all positive on reducing drying time and energy consumption of noodles, but the drying enhancement effect of puncturing treatment is better. Combining laser puncturing treatment with leavening agent mixture can further reduce drying time of noodles by up to 34.15% and energy consumption by up to 33.17%. Although all single treatment methods can improve the quality of products including soaking time, rehydration rate and hardness, the effect is unsatisfactory. Hybrid strategies are found to have a synergistic effect on the production of high-quality freeze-dried instant noodles and according to the sensory evaluation results, the optimum conditions are as follows: 0.1 mm perforation diameter, 10 mm spacing between perforations, 2 mm depth and 3% leavening agent mixture (on flour basis). Industrial relevanceDifficult rehydration of products and high energy consumption of the production process are the key issues that limit the industrial production of freeze-dried instant noodles. Laser puncturing treatment and adding a leavening agent mixture can increase the contact area between freeze-dried noodles and water and enrich the internal porous structure of freeze-dried noodles, respectively, which promotes the mass production of high-quality freeze-dried instant noodles.

Enhancing biogas production of anaerobic co-digestion of industrial waste and municipal sewage sludge with mechanical, chemical, thermal, and hybrid pretreatment

This study presents the effect of mechanical, chemical, thermal, and hybrid pretreatment on anaerobic digestion of fruit-juice industrial waste (FW) co-digested with municipal sewage sludge (MSS). The pretreatment of the substrates with ultrasonication, microwave, weak alkali-acid caused an increase in cumulative biogas production of approximately 20.9, 14.9, 8.1, and 5.2%, respectively. Beside this, thermal and strong acid-alkali pretreatment reduced biogas production. The highest cumulative biogas and methane yield was increased with hybrid pretreatment which contains ultrasonication (US) and alkali (AL) pretreatment by 36% and 49%, respectively. Also, compared to untreated mixture, the soluble COD, carbohydrate, and protein removal efficiencies were increased from 42.6% to 65.6%, 65.1% to 86.6%, and 17.3% to 62.4%, respectively for US-AL pretreatment. The kinetic parameters of cumulative biogas production for the selected reactors were further estimated with Monod, Cone, and Transference Function models.

Production of Fermentable Sugars from Cassava Stem using Hybrid Pretreatment Technology

One of the crucial steps in the enzymatic hydrolysis of biomass is pretreatment. We investigated the applicability of a hybrid pretreatment method, This involved acid treatment followed by alkali before the production of fermentable sugars from cassava stem. The substrate was initially treated with acid (1% oxalic acid at 100 °C for 2 h), followed by treatment with a 10% NaOH–urea mixture (by mixing 5 g each of NaOH and urea in 100 mL of water) at 100 °C for 1 h. A cellulose recovery of 98.55% was obtained with the acid-alkali pretreatment method.

Effect of Interface Pretreatment of Al Alloy on Bonding Strength of the Laser Joined Al/CFRTP Butt Joint.

In the present research, the carbon fiber reinforced thermoplastic (CFRTP) was laser joined with the Al alloy whose joining interface was pretreated by laser micro-texturing, anodizing, and hybrid of laser micro-texturing and anodizing. The surface morphology of the pretreated Al joining interface and bonding strength of the corresponding Al/CFRTP butt joint were investigated. The results show that the laser micro-texturing has fabricated the micro-pit or micro-furrow in the Al joining interface. With the increasing of laser scanning times, the size of the micro-pit or micro-furrow decreases, when the laser scanning distance is constant. The bonding strength of the Al/CFRTP butt joint with Al joining interface pretreated by micro-texturing fluctuates with the increasing of laser scanning distance and times, reaching the maximum value of 20 MPa at laser scanning distance of 0.1 mm and 1 time. The anodizing pretreatment has formed the Al2O3 oxide layer on the Al joining interface. The Al/CFRTP butt joint with Al joining interface pretreated by anodizing obtains the maximum bonding strength of 11 MPa at anodizing time of 10 min. The hybrid pretreatment of micro-texturing and subsequent anodizing fabricates the regular grid structure with smooth micro-furrow and micro-pit, while the hybrid pretreatment of anodizing and subsequent micro-texturing fabricates the Al joining interface with explosive micro-pit and micro-furrow. The bonding strength of the Al/CFRTP butt joint with hybrid-pretreated Al joining interface is relative better than that of the Al/CFRTP butt joint with anodizing-pretreated Al joining interface but almost lower than that of the Al/CFRTP butt joint with micro-texturing pretreated Al joining interface. Such results should be attributed to the surface morphology of the Al joining interface.

Wheat straw pre-treatments using eco-friendly strategies for enhancing the tensile properties of bio-based polylactic acid composites

Individual and hybrid pre-treatments, including hot water, steam and microwave were used on wheat straw to mitigate the surface quality deficiencies for an intimate interfacial bond between substrate and Polylactic Acid matrix. Microstructural analysis showed the expansion of cells due to the pre-treatments which in turn promotes mechanical entanglement between wheat straw and PLA, thus, improving the tensile properties of bio-based composites. The tensile strength, elongation at break, elastic modulus, and toughness increased by 166 %, 18 %, 68 %, and 285 %, respectively, for hot water followed by steam pre-treated wheat straw bio-based composites compared to untreated.

Optimization of keratin protein extraction from waste chicken feathers using hybrid pre-treatment techniques

This study modeled and optimized the operational conditions for the extraction of keratin from waste chicken feathers via alkaline hydrolysis method. Response Surface methodology using Box-Behnken design was used to investigate the effect of time, temperature and the concentration of both sodium hydroxide and sodium bisulphite as an extraction solvent on the keratin hydrolysate and protein yield. The coefficients of determination (R2) of 0.77 and 0.74 were obtained for keratin hydrolysate and protein yield models, respectively demonstrating the fitness of the models to navigate the optimization space. The optimum parameters were temperature (87 °C), time (111 min), sodium hydroxide (1.78%) and sodium bisulphite (0.5%). The yields of keratin hydrolysate and protein after validation were 68.3% and 65.2% respectively. Protein analysis via the CHNS analyser showed the elemental composition of 13.85% N, 47.25% C, 6.90% H and 2.8% S. The molecular weight of the extracted keratin ranged between 10-15 kDa and 3–10 kDa. Ultimate analysis by FTIR and NMR confirmed the presence of amide, carboxylic groups and alkyl side chains of amino acids. The results of this study proved that chicken feathers, typically disposed of by the poultry slaughterhouses, would be able to serve as a great sustainable source of keratin protein for the manufacture of value-added products like bio-adhesives.

Corrosion-resistant organic-inorganic hybrid pretreatments obtained by UV-initiated process suitable for primer-less coating systems

A photo-initiated sol-gel process has been developed to deposit organic-inorganic hybrid (OIH) thin films on metal substrates for corrosion protection. Wet films of non-aqueous compositions containing specially designed organo-silane precursors and photo-latent catalysts –photo-acid generator (PAG) or photo-base generators (PBG)-, were exposed to ultraviolet (UV) radiation under ambient moisture environment leading to OIH films by sol-gel reactions. Synthesis and curing of organo-silanes were characterized using instrumental and gravimetrical techniques. Moreover, the corrosion resistance performance of OIH films based on two families of organo-silane precursors cured by PAG and PBG were compared with those obtained by the conventional aqueous sol-gel process. The effects of precursor and photocatalyst type, UV light intensity, cure conditions, and film thickness on anti-corrosion performance of OIH coatings were studied using various qualitative and quantitative techniques such as DC polarization, electrochemical impedance spectroscopy (EIS), and accelerated salt spray test. Results revealed that selected OIH pretreated samples showed corrosion current density as low as 1.2 nA/cm2, which is superior compared to conventional hexavalent chromium-based Cr (VI) pretreatments. The study demonstrates the feasibility of this sustainable photo-initiated sol-gel process for many applications, such as primer-less coating systems.

Anaerobic co-digestion of activated sludge and fruit and vegetable waste: Evaluation of mixing ratio and impact of hybrid (microwave and hydrogen peroxide) sludge pre- treatment on two-stage digester stability and biogas yield

Co-digestion of mixed waste activated sludge (MWAS) and fruit and vegetable waste (FVW) was studied in a two-stage (thermophilic followed by mesophilic) semi-continuous anaerobic digestion to evaluate anaerobic digester performance and stability. A mixing ratio of 75 % MWAS and 25 % FVW showed a 1.6-fold increase in overall methane yield and achieved 0.38 volatile fatty acids to alkaline buffer capacity ratio (FOS/TAC) compared to mixture of 50 % MWAS and 50 % FVW. Application of hybrid (MW-H2O2) pretreatment in the former mixing ratio increased sludge solubilization by 33 % and consequently enhanced overall methane yield by 2.17-fold. The treated digester showed increased process stability with a FOS/TAC ratio of 0.26 as a consequence of buffer capacity offered by released biopolymers during pre-treatment. The generation of superoxide radicals during anaerobic digestion was studied and found to negatively correlate with sludge bioactivity. Two-stage digestion also minimizes the issue of high acidification due to co-digestion involving FVW.

Modified eucalyptus bark as a sorbent for simultaneous removal of COD, oil, and Cr(III) from industrial wastewater

This study has investigated the efficiency of eucalyptus bark (EB) to remove COD, oil, and Cr(III) from raw petroleum refinery effluent. Experimental works were conducted to assess the performance of raw and modified EB using chemical impregnation, carbonization, and hybrid pre-treatment. Then modified EB by hybrid H3PO4/carbonization that showed the best performance was further examined under different operating conditions: namely contact time, solution pH, temperature, and sorbent dosage. In general, removal efficiencies of COD, oil, and Cr(III) increased with the increase in contact time and sorbent dosage while acidic pH was favourable for achieving higher removal efficiency for targeted pollutants. The maximum removal efficiencies of COD, oil, and Cr(III) were 80, 91, and 61%, respectively. Meanwhile, the optimum operating conditions were found at contact time 100 min, sorbent dosage 10 g/L, pH 3, and temperature 25 °C. FTIR and SEM were also applied to characterize the sorbent. The Freundlich adsorption isotherm model shows a better correlation coefficient among the other isotherm models including Langmuir and Dubinin-Radushkevich with the R2 value of 0.9758. The adsorption kinetic examined using different kinetic models including pseudo-first order, pseudo-second order, intra-particle diffusion, liquid film diffusion, and double exponential follows intra-particle diffusion model.

Optimisation and Modelling of Anaerobic Digestion of Whiskey Distillery/Brewery Wastes after Combined Chemical and Mechanical Pre-Treatment

Whiskey distillery waste streams consisting of pot ale (liquid residue) and spent grain (solid residue) are high strength organic wastes and suitable feedstock for anaerobic digestion (AD) from both economic and environmental stand points. Anaerobic digestion of pot ale and pot ale/spent grain mixtures (with mixing ratios of 1:1, 1:3, and 1:5 by wet weight) was performed after implementation of a novel hybrid pre-treatment (combined chemical and mechanical) in order to modify lignocellulosic structure and ultimately enhance digestion yield. Lignin, hemicellulose, and cellulose fractions were determined before and after chemical pre-treatment. Effects of different inoculum rates (10–30–50% on wet basis) and beating times (0–7.5–15 min) on anaerobic digestion of pot ale alone and of pot ale/spent grain mixtures were investigated in lab scale batch mode with a major focus of optimising biogas yield by using response surface methodology (RSM) in Design Expert Software. The highest biogas yields of 629 ± 8.5 mL/g vs. (51.3% CH4) and 360 ± 10 mL/g vs. (55.0 ± 0.4) with anaerobic digestion of pot ale alone and spent grain mix after 1M NaOH and 7.5 min beating pre-treatments with 50% inoculum ratio respectively. The optimum digestion conditions to maximise the biogas quality and quantity were predicted as 10 and 13 min beating times and 32 and 38 °C digestion temperatures for anaerobic digestion of pot ale alone and spent grain mix respectively.

Effect of hybrid (microwave-H2O2) feed sludge pretreatment on single and two-stage anaerobic digestion efficiency of real mixed sewage sludge

The impacts of hybrid microwave-oxidative (MW-H2O2) feed sludge pretreatment on performance efficiency of conventional single-stage and a novel two-stage semi-continuous anaerobic digestion of mixed waste activated sludge were studied to enhance biogas production and digestate quality. Untreated two-stage anaerobic digestion (thermophilic followed by mesophilic) achieved 76.4 ml/gTCOD methane yield compared to 40.4 ml/gTCOD achieved through conventional mesophilic anaerobic digestion, with an increase in methane percentage. Application of hybrid (MW-H2O2) sludge pretreatment in the two-stage digestion enhanced initial sludge hydrolysis/solubilisation and consequently achieved 143.4 ml/gTCOD methane yield. Also, the highest methane percentage of 71 % was achieved during peak methanogenesis stage in this process. The synergetic effects of hybrid pretreatment were also confirmed by the higher release of extracellular polymeric substances. Oxidative stress exerted by the pretreatment resulted in the accumulation of superoxide radicals in the initial thermophilic phase; followed by increased sludge activity and biomethanation in the later phase of two-stage digestion. Hybrid feed sludge pretreatment in the two-stage system achieved a 73 % volatile solids reduction and more than 90 % reduction of faecal coliform. The various kinetic model parameters were determined by the application of the modified Gompertz model. These results illustrate that a novel semi-continuous two-stage anaerobic digester with hybrid feed sludge pretreatment improved sludge hydrolysis, sludge solubilisation, biogas production, sludge stabilization and reduces sludge retention time, and also achieves “class-A” biosolids by significant pathogen destruction.

Technoeconomic Assessment of Hybrid Organosolv–Steam Explosion Pretreatment of Woody Biomass

This study investigates technoeconomic performance of standalone biorefinery concepts that utilize hybrid organic solvent and steam explosion pretreatment technique. The assessments were made based on a mathematical process model developed in UniSim Design software using inhouse experimental data. The work was motivated by successful experimental applications of the hybrid pretreatment technique on lignocellulosic feedstocks that demonstrated high fractionation efficiency into a cellulose-rich, a hemicellulose-rich and lignin streams. For the biorefinery concepts studied here, the targeted final products were ethanol, organosolv lignin and hemicellulose syrup. Minimum ethanol selling price (MESP) and Internal rate of return (IRR) were evaluated as economic indicators of the investigated biorefinery concepts. Depending on the configuration, and allocating all costs to ethanol, MESP in the range 0.53–0.95 €/L were required for the biorefinery concepts to break even. Under the assumed ethanol reference price of 0.55 €/L, the corresponding IRR were found to be in the range −1.75–10.7%. Hemicellulose degradation and high steam demand identified as major sources of inefficiencies for the process and economic performance, respectively. Sensitivity of MESP and IRR towards the most influential technical, economic and market parameters performed.

Deoiled algal biomass derived renewable sugars for bioethanol and biopolymer production in biorefinery framework

The present study is designed to evaluate the potential of deoiled algal biomass (DAB) residue as an alternative resource for the production of bioethanol and biopolymers in a biorefinery approach. Hybrid pretreatment method resulted in higher sugar solubilization (0.590 g/g DAB) than the corresponding individual physicochemical (0.481 g/g DAB) and enzymatic methods (0.484 g/g DAB). Subsequent utilization of sugars from hybrid pretreatment for bioethanol using Saccharomyces cerevisiaeresulted in maximum bioethanol production at pH 5.5 (0.145 ± 0.008 g/g DAB) followed by pH 5.0 (0.122 ± 0.004 g/g DAB) and pH 6.0 (0.102 ± 0.002 g/g DAB). The experiments for biopolymer (PHB: polyhydroxybutyrate) production resulted in 0.43 ± 0.20 g PHB/g DCW. Extracted polymer on NMR and FT-IR analysis showed the presence of PHB. Exploration of DAB as an alternative renewable resource for multiple biobased products supports sustainability and also enables entirety use of DAB by addressing the DAB-residue allied disposal issues.

Polyacrylic acid/Ca nanoparticles hybrid hydrosol: Synthesis, characterization and application in pretreatment layer

Pretreatment layers have attracted much attention due to their irreplaceable role in paint system. However, the commonly used pretreatment layers face with one common problem, which the environmental friendliness and excellent properties can not be simultaneous realization. This work reported one facile method to synthesize one stable polyacrylic acid/Ca nanoparticles hybrid hydrosol through the electrostatic interaction between polyacrylic acid and Ca2+. Ulteriorly, the fabricated stable hydrosol was utilized as one environmentally friendly pretreatment layer material to fabricate new generation pretreatment layer on cold-roll steel surface through immersion method. The electrochemical and microstructure results indicated that the polyacrylic acid/Ca hybrid hydrosol based pretreatment layer exhibited better anti-corrosion performance and higher root mean square roughness value than polyacrylic acid layer. Meanwhile, neutral salt spray test results reflected that the polyacrylic acid/Ca hybrid pretreatment layer based coating system exhibited better service performance than the no pretreatment or polyacrylic acid layer based coating system. Because of the environmental friendliness, good anti-corrosion performance and higher root mean square roughness value, the polyacrylic acid/Ca nanoparticles hybrid hydrosol based pretreatment layer are expected to act as substitutes for chromate and phosphate conversion layers and will find widespread application in metal surface pretreatment field.

Improvement of the thermophilic anaerobic digestion and hygienisation of waste activated sludge by synergistic pretreatment

Hybrid disintegration of waste activated sludge (WAS) before the thermophilic anaerobic stabilization of WAS contributes to the intensification of organic compounds decomposition and increases the effectiveness of the anaerobic stabilization process compared to the fermentation of raw WAS. This article investigates the influence of a chemical–thermal pretreatment procedure with the use of NaOH and freezing by the dry ice on WAS. We found that the hybrid pretreatment of WAS causes higher concentration of released organics in the liquid phase (represented here as a change in soluble chemical oxygen demand – SCOD value) in comparison to these disintegration techniques used separately. The use of disintegrated WAS (WASD) as an additional material in the digester chambers impacts (varying on its proportion added), the generation of biogas and its yield. The recorded amount of the produced biogas and biogas yield after 21 days of fermentation increased by 26.6% and 2.7%, respectively (in comparison to blank sample). In addition, it was observed that the hybrid process before anaerobic stabilization contributes to a higher hygienisation of the digested sludge.

Hybrid dilute sulfuric acid and aqueous ammonia pretreatment for improving butanol production from corn stover with reduced wastewater generation

An efficient hybrid pretreatment method was developed for butanol production from corn stover using dilute sulfuric acid (DA) and aqueous ammonia (AA). With the optimized AA concentration, treatment temperature and time of 10% AA, 80 °C and 24 h, the hybrid pretreatment could effectively dissolve hemicellulose and lignin with solid recovery rate of 37.45% and lignin reduction rate of 86.77% compared to those of 57.75% and 45.84% from single DA pretreatment. By washing 1 time after each step treatment, sugar yield and butanol production were increased to 401.76 mg/g-CS and 10.89 g/L from 346.04 mg/g-CS and 9.33 g/L obtained without washing. Compared with conventional single DA and AA pretreatment methods, wastewater generation was reduced to 0.83 L/g-butanol from 2.11 and 3.46 L/g-butanol, indicating this hybrid pretreatment could be an effective approach for improving butanol production from lignocellulosic feedstocks.

Assessment of Excess Sludge Ultrasonic, Mechanical and Hybrid Pretreatment in Relation to the Energy Parameters

Anaerobic digestion is the most common stabilization process at large sewage treatment plants. To improve its effects, a sludge pre-conditioning process called disintegration is recommended. The aim of the presented study was to compare the direct effects of various types of mechanical disintegration, performed for the same excess sludge, in relation to the energy parameters and effectiveness of the process. Four different disintegration methods were used: mechanical disintegration in semi-technical and laboratory scale homogenizing mixers, ultrasonic disintegration (US) and combined (hybrid) process. The disintegration was performed for volumetric energy EV = 4.67–100 kWh m−3, the results were evaluated based on dispersion (kdCOD, kdCST), lysis (kdSCOD), acidification (kdVFA) and nutrient release (kdTN, kdTP) disintegration indicators. The statistical analysis of the results indicates the influence of disintegrator type (mixer/US/hybrid), scale (laboratory/semi-technical) and energy input on the direct results of disintegration. Hybrid disintegration delivered better direct results than two pre-treatment processes used separately. The efficiency of the hybrid process defined as the increase of the indicator (disintegration products—∆FCOD, ∆SCOD) per unit of energy was considerably higher than for a single stage disintegration process.

Effect of MBR-H2O2/UV Hybrid pre-treatment on nanofiltration performance for the treatment of petroleum refinery wastewater

Abstract This study aimed to investigate the performance of direct (UV) and hydrogen peroxide-assisted (UV/H2O2) photolysis applied to MBR permeate as a pre-treatment for nanofiltration systems treating petroleum refinery wastewater. The MBR permeate was subjected to UV and UV/H2O2 (C:H2O2 1:1, 1:2 and 1:3) in order to reduce the membrane fouling potential of nanofiltration in the polishment stage. The process that promoted the lower fouling potential was chosen as pre-treatment for nanofiltration process. The results showed that MBR permeate COD removal efficiency of 80% is enough for membrane fouling mitigation and that C:H2O2 ratio of 1:3 with retention time of 60 min is the best technical and economic condition for that. The H2O2/UV showed potential for the mitigation of flux decline due to membrane fouling, improvement in membrane cleanability, which consequently prolongs the NF membrane lifespan. The total operational cost (OpEx) for the H2O2/UV was estimated to be 0.231 US$/m3 and the integration of H2O2/UV to NF process represents savings of 20% of CapEx and 20% of OpEx. Finally, the MBR-H2O2/UV - NF process produces high quality water that can be reused in the refinery process, such as in cooling systems.