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• Thermal pretreatment had negative/no effect on larval performance. • Mechanical pretreatment increased bioconversion rate for both substrates. • Bioconversion rate of grass clippings improved by 23–44%. • Mechanical pretreatment affected physical properties and microbial respiration. Black soldier fly larvae (BSFL , Hermetia illucens (L.)) are recognized for efficient biowaste reduction while yielding valuable proteins and fats for animals. However, lignocellulosic fibers in biowastes are difficult to digest by biowaste and larval digestive tract microorganisms as well as the larvae themselves. This study investigated two biowaste physical pretreatments (thermal, mechanical) for improving BSFL processing of fibrous biowastes. Cow manure, spent grain, and grass clippings were thermally pretreated at 90 °C for three durations (0.5, 1 and 4 h). Contrary to expectations, thermal pretreatment resulted in either no improvement or decreased larval performance on all substrates, regardless of treatment duration. In contrast, mechanical pretreatment of spent grain and grass clippings, involving milling with three screen sizes (0.5, 1 and 2 mm) showed promising results. Specifically, bioconversion rates on 0.5 mm-milled spent grain and grass clippings increased by 0–53 % and 25–44 % dry mass, respectively compared to untreated. Additionally, larval protein conversion increased by 41 % and 23 % on spent grain and grass clippings, respectively. However, mechanical pretreatment did not affect fiber degradation by larval conversion, as hemicellulose decreased by 25 % and 75 % for spent grain and grass clippings, respectively, regardless of particle size. Particle size reduction influenced substrate microbial respiration (CO 2 mg/min), with 0.5-mm milled grass clippings exhibiting higher respiration compared to untreated, although this effect was not observed for spent grain. This study highlights mechanical pretreatment's potential in enhancing BSFL bioconversion of fibrous biowastes and the importance of understanding substrate physical properties influencing substrate microorganisms and BSFL. [ABSTRACT FROM AUTHOR]

Semi-crystalline natural polymers are involved in many technological processes. Biopolymers having identical chemical compositions can differ in reactivity in heterogeneous transformations depending on their crystal structure (polymorphic modification). This paper compares the crystal structure recrystallization processes occurring in natural polysaccharides (cellulose, chitin, and starch) in the individual form and as a component of native biomass. Aqueous treatment of pre-amorphized semi-crystalline biopolymers was shown to result in swelling, thus alleviating the kinetic restrictions imposed on the restoration of crystalline regions and phase transition to the thermodynamically more stable polymorphic modification. During recrystallization, cellulose I in the individual form and within plant-based biomass undergoes a transition to the more stable cellulose II. A similar situation was demonstrated for α- and β-chitin, which recrystallize only into the α-polymorphic modification in the case of both individual polymers and native materials. Recrystallization of A-, B-, and C-type starch, both in the individual form and within plant-based flour, during aqueous treatment, results in a phase transition, predominantly to the B-type starch. The recrystallization process depends on the temperature of aqueous treatment; longer treatment duration has almost no effect on the recrystallization degree of polymers, both in the individual form and within native materials. [ABSTRACT FROM AUTHOR]

Currently, the recovery of resources from urban wastewater (WW) represents a priority. On this topic, the potential recovery of cellulose for its subsequent reuse in different sectors is gaining interest. In this work, a large-size conventional wastewater treatment plant (WWTP) was selected as a case study. A preliminary mechanical treatment was used, with the aim of separating, quantifying, and characterizing cellulose in WW. The results suggest that the per-capita production of dry primary cellulosic sludge (D-PCS) is equal to 1.46 ± 0.13 kgD-PCS PE−1 y−1, with an average calorific value of 21.04 MJ kg−1DM. Cellulosic fibres have an average length of >100 µm and a thickness of 2–5 µm. The D-PCS was subsequently treated via medium-temperature pyrolysis; a total of 29.5% of the initial D-PCS was converted into pyrolyzed primary cellulosic sludge (P-PCS) and only 26% into pyrolytic gas. More than 44.5% of the dried cellulose can be converted into pyrolytic oil. Moreover, three different scenarios of recovery have been considered, and the impact of cellulose separation in terms of COD fluxes entering the WWTP and potential energy recovery has been studied. The results suggested that, in this case study, the potential separation of the primary cellulosic sludge from the influent water flux would have no significant impact on COD load entering the biological treatments and biogas production in the anaerobic digestion of the secondary sludge. [ABSTRACT FROM AUTHOR]

The influence of a mechanical or a thermal pretreatment of a linear (L-PP) and a long-chain branched polypropylene (LCB-PP) in the molten state was studied. The molar mass distributions and the branching structure were determined by high-temperature gel permeation chromatography HT-GPC coupled with laser-light scattering. The samples were extruded through long or short capillaries of various geometries corresponding to a predominant shear or elongational deformation. As a rheological probe, the extrudate swell at low stresses was measured for the differently pretreated samples. For the L-PP, neither molecular nor rheological changes were observed. However, the extrudate swell of the LCB-PP was found to decrease with increasing volume throughput. It was more strongly affected by shear in the capillary than by molecule stretching in the entry region. The smaller extrudate swell was accompanied by a decrease of the high molar mass tail of the LCB-PP, which could be the reason for the decay of swell, in principle. However, a comparable degradation of the high molar mass tail was obtained by a pure thermal treatment that was shown to leave the extrudate swell unchanged. This result and the unaffected branching structures found by high-temperature gel permeation chromatography (HT-GPC) support the hypothesis of a change of the branching topography by the mechanical pretreatment. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of mechanical treatment through twin-screw extrusion for the enhancement of biomethane production. Four lignocellulosic biomasses (i.e., sweetcorn by-products, whole triticale, corn stover and wheat straw) were evaluated, and two different shear stress screw profiles were tested. Chemical composition, particle size reduction, tapped density and cellulose crystallinity were assessed to show the effect of extrusion pretreatment on substrate physico-chemical properties and their biochemical methane production (BMP) capacities. Both mechanical pretreatments allowed an increase in the proportion of particles with a diameter size less than 1 mm (from 3.7% to 72.7%). The most restrictive profile also allowed a significant solubilization of water soluble coumpounds, from 5.5% to 13%. This high-shear extrusion also revealed a reduction in cellulose crystallinity for corn stover (i.e., 8.6% reduction). Sweetcorn by-products revealed the highest BMP values (338–345 NmL/gVS), followed by corn stover (264–286 NmL/gVS), wheat straw (247–270 NmL/gVS) and whole triticale (233–247 NmL/gVS). However, no statistical improvement in maximal BMP production was provided by twin-screw extrusion. Nevertheless, BMP kinetic analysis proved that both extrusion pretreatments were able to increase the specific rate constant (from 13% to 56% for soft extrusion and from 66% to 107% for the high-shear one).

Currently, the recovery of resources from urban wastewater (WW) represents a priority. On this topic, the potential recovery of cellulose for its subsequent reuse in different sectors is gaining interest. In this work, a large-size conventional wastewater treatment plant (WWTP) was selected as a case study. A preliminary mechanical treatment was used, with the aim of separating, quantifying, and characterizing cellulose in WW. The results suggest that the per-capita production of dry primary cellulosic sludge (D-PCS) is equal to 1.46 ± 0.13 kgD-PCS PE−1 y−1, with an average calorific value of 21.04 MJ kg−1DM. Cellulosic fibres have an average length of >100 µm and a thickness of 2–5 µm. The D-PCS was subsequently treated via medium-temperature pyrolysis; a total of 29.5% of the initial D-PCS was converted into pyrolyzed primary cellulosic sludge (P-PCS) and only 26% into pyrolytic gas. More than 44.5% of the dried cellulose can be converted into pyrolytic oil. Moreover, three different scenarios of recovery have been considered, and the impact of cellulose separation in terms of COD fluxes entering the WWTP and potential energy recovery has been studied. The results suggested that, in this case study, the potential separation of the primary cellulosic sludge from the influent water flux would have no significant impact on COD load entering the biological treatments and biogas production in the anaerobic digestion of the secondary sludge.

• HTC environmental performance is mainly connected with its energy balance. • Lower dilution ratio and higher temperature provide better environmental indicators. • It is recommended to co-combust all the produced hydrochar in lignite power plant. • Burdens for process water treatment do not significantly offset the benefits of HTC. • HTC performs better than the conventional under-sieve fraction treatments. The under-sieve fraction (USF), obtained as one of the output streams from the mechanical pretreatment of mixed municipal solid waste, is usually aerobically biologically stabilized before being landfilled. For its characteristics (i.e., moisture and organic content), the USF can be alternatively processed by hydrothermal carbonization (HTC), producing hydrochar to be used for energy production. Based on previous results obtained from laboratory HTC tests of the USF, this work is aimed at evaluating the sustainability of the proposed process from an environmental point of view by applying the Life Cycle Assessment. Various combinations of process parameters (temperature, time, and dry solid-to-water ratios) and two different utilization pathways for hydrochar (the whole amount produced in external lignite power plants or part of it used internally) are compared. The results indicate that environmental performances are mainly connected with process energy consumption: in general, the cases operating at the lowest dilution ratio and the highest temperature provide improved environmental indicators. Co-combusting all the produced hydrochar in external power plants provides better environmental performances than feeding a portion of it to the HTC itself: the avoided effects by displacing lignite are higher than the additional burdens from natural gas use. Then, alternative process water treatments are compared, showing that the burdens added by the process water treatments do not offset the benefits generated by the main HTC process for the major part of the considered environmental indicators. Finally, the proposed process indicates better environmental performances when compared to the conventional method of treating the USF, based on aerobic biostabilization and landfilling. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of mechanical treatment through twin-screw extrusion for the enhancement of biomethane production. Four lignocellulosic biomasses (i.e., sweetcorn by-products, whole triticale, corn stover and wheat straw) were evaluated, and two different shear stress screw profiles were tested. Chemical composition, particle size reduction, tapped density and cellulose crystallinity were assessed to show the effect of extrusion pretreatment on substrate physico-chemical properties and their biochemical methane production (BMP) capacities. Both mechanical pretreatments allowed an increase in the proportion of particles with a diameter size less than 1 mm (from 3.7% to 72.7%). The most restrictive profile also allowed a significant solubilization of water soluble coumpounds, from 5.5% to 13%. This high-shear extrusion also revealed a reduction in cellulose crystallinity for corn stover (i.e., 8.6% reduction). Sweetcorn by-products revealed the highest BMP values (338–345 NmL/gVS), followed by corn stover (264–286 NmL/gVS), wheat straw (247–270 NmL/gVS) and whole triticale (233–247 NmL/gVS). However, no statistical improvement in maximal BMP production was provided by twin-screw extrusion. Nevertheless, BMP kinetic analysis proved that both extrusion pretreatments were able to increase the specific rate constant (from 13% to 56% for soft extrusion and from 66% to 107% for the high-shear one). [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are natural polyesters which biodegrade in soils and oceans but have more than double the cost of comparable oil-based polymers. PHA downstreaming from its biomass represents 50% of its overall cost. Here, in an attempt to assist downstreaming, mastication of wet biomasses is tested as a new mechanical continuous biomass pretreatment with potential for industrial upscaling. Downstreaming conditions where both product recovery and purity are low due to the large amount of treated wet biomass (50% water) were targeted with the following process: extraction of 20 g in 100 mL solvent at 30 °C for 2 h, followed by 4.8 h digestion of 20 g in 0.3 M NaOH. Under the studied conditions, NaOH digestion was more effective than solvent extraction in recovering larger PHA amounts, but with less purity. A nearly 50% loss of PHA was seen during digestion after mastication. PHAs downstreamed by digestion with large amounts of impurities started to degrade at lower temperatures, but their melt elasticity was thermally stable at 170 °C. As such, these materials are attractive as fully PHA-compatible processing aids, reinforcing fillers or viscosity modifiers. On the other hand, wet biomass mastication before solvent extraction improves PHA purity and thermal stability as well as the melt rheology, which recovers the viscoelasticity measured with a PHA extracted from a dried biomass. [ABSTRACT FROM AUTHOR]

Cellulose nanofibers (CNF) and microfibrillated cellulose (MFC) are biodegradable micro and nanomaterials derived from plant cellulose. The properties of CNF, influenced by fibril length, impact the strength of cellulose-based nanomaterials. This study uses enzymatic milling to explore pretreatments, enzymatic optimization, and CNF/MFC production. The study found that hammer milling and lamination are effective pretreatments for preserving fibers. The optimal enzymatic mixture contained 75 % cellulase and 25 % xylanase, yielding 68.7 % and 2.86 %/h productivity, respectively. The addition of the LPMO enzyme increased the yield by 10–13 %, depending on its concentration. Enzymatic milling was introduced as an innovative approach to CNF production, reducing hydrolysis time and creating milder processing conditions. The combined process of ball milling and enzymatic hydrolysis on pre-ground pulp in the hammer mill achieved a maximum CNF yield of 45.83 % and productivity of 13.10 %/h. X-ray diffraction showed that the lamination-pre-treated pulp had a high crystallinity index of 84.34 %. Scanning electron microscopy revealed fibers with diameters ranging from 52 nm to 296 nm. These findings support the search for sustainable and eco-friendly alternatives to non-renewable resources, enabling sustainable CNF production at room temperature with reduced processing time. [Display omitted] • Enzymatic milling process is implemented for production of cellulose nanofibrils. • Optimal enzyme cocktail mixture was determined using a statistical design. • The study looked at how LPMO affects the enzyme cocktail that breaks down biomass. [ABSTRACT FROM AUTHOR]

To develop novel food-grade Pickering emulsion stabilizers, insoluble rice bran protein-polysaccharide-phenol natural complex (IRBPPP) was prepared into Pickering emulsion stabilizers after different mechanical pretreatments (shear, high-pressure homogenization, ultrasonic, and combined mechanical pretreatment). With the increase in mechanical pretreatment types, the covalent binding of proteins and polysaccharides in IRBPPP gradually enhanced, the breakage efficiency of IRBPPP gradually increased (IRBPPP particle size decreased from 220.54 to 67.89 μm, the specific surface area of IRBPPP particle increased from 993.47 to 2033.86 cm−1/g), and the microstructure of IRBPPP gradually showed an orderly network structure, which enhanced the IRBPPP dispersion stability and the Pickering emulsion stability. Pickering emulsion stability was highly correlated (P < 0.01) with the breakage efficiency of IRBPPP particles. Overall, the combined mechanical pretreatment improved the stability of the IRBPPP-stabilized Pickering emulsion. The study added value to rice bran products and offered a new way to create stable food-grade Pickering emulsions for functional foods using natural protein-polysaccharide-phenol complex particles. [Display omitted] • Mechanical pretreatment promoted covalent interaction of protein and polysaccharide. • Mechanical pretreatment induced structure breakage of the natural complex. • Mechanical pretreatment allowed natural complex to form orderly network structure. • Endogenous phenol content determined the surface wettability of natural complex. • Mechanical pretreatment improved the Pickering emulsion stability of natural complex. [ABSTRACT FROM AUTHOR]

Jatropha curcas is a promising tropical and subtropical plant species for biodiesel production that can reduce the competition between food and energy production. Jatropha seed processing for oil extraction usually generates considerable amount of Jatropha curcas fruit shell (JCFS), which can be considered as a potential substrate for biogas production rather than being discarded as solid waste. However, the higher lignocellulosic constituents in JCFS potentially affect the biological degradation process. Thus, applying suitable pretreatment techniques in advance of anaerobic digestion could enhance the biodegradability and methane yield of JCFS. In this study, the effect of mechanical, steam explosion (SE), and alkaline pretreatments on the chemical composition and methane yield of JCFS was examined at various process conditions. As compared with the untreated sample, grinding the JCFS into a particle size of less than 1 mm increased the methane yield by 74.23%, while at the optimum SE pretreatment process (160 °C, 5 min), the methane yield was increased by 54.75%. The alkaline pretreatment was relatively less effective over the other pretreatments; 44.05% methane yield increment was achieved after soaking the JCFS with 7.32% NaOH at 36 °C for 54 h. The effect of SE on compositional change depends on the severity factor in which severe pretreatment conditions were adequate for solubilizing the hemicellulose but resulted in higher pseudo-lignin and lower methane yields. In conclusion, all pretreatments processes have significantly increased the methane yield of JCFS as compared to the untreated JCFS; however, mechanical pretreatment was more effective than SE and alkaline pretreatments. [ABSTRACT FROM AUTHOR]

Cotton stalks (CS) are lignocellulosic agricultural by-products, a potential source for biogas production, but pretreatment must be considered since hydrolysis is the rate-limiting stage for lignocellulosic biomass substrates. This study investigates the feasibility of mechanical pretreatment of CS to enhance methane production. Batch anaerobic digestion of CS samples with particle sizes ranging from 0.5 to 65 mm was carried out in 1 L eudiometer batch digesters for 48 days at 37°C. Results showed that methane yield was inversely proportional to particle size, and the quality of biogas was good (54.0–55.2% CH4). Significant increases in methane yield were observed with 20.3% and 26% for samples with a particle size of 3 mm and 0.5 mm, respectively, compared to untreated CS. The coefficient of anaerobic energy turnover was relatively low (20.2–25.5%). Reduction of the CS particle size to 3 mm or less is recommended to achieve effective methane conversion and decrease the retention time in an anaerobic digester from 31 to about 25 days. However, to offset the high energy demand required for grinding, further research should be conducted in combining size reduction with chemical and physicochemical pretreatment.

Three successive mechanical pretreatments were applied at lab-scale in order to mimic the main functions of industrial mechanical pretreatments used for feedstock preparation in anaerobic digestion: particle size reduction (shredding), homogenization (mixing) and fiber alteration (blending). In parallel, full-scale mechanical devices have been investigated (two hammer mills and one chain mill). A physical and biochemical characterization was undertaken before and after each pretreatment. The results at lab-scale revealed that shredding reduced the size of coarse particles, smoothly increased solubilisation but did not affect much the methane yield. Mixing further improved the solubilisation and the water retention capacity of the investigated products. The most important effect was the improvement of the methane production rate rather than the methane yield. The results on full-scale pretreatments revealed that they behave as a combination of each function. Principal component analysis enabled to assign each full-scale device according to its effect on the investigated parameters. [ABSTRACT FROM AUTHOR]

This study aimed at energy reduction during pulping of L. leucocephala by passing the wood chips through an impressafiner followed by xylanase pretreatment. An impressafiner compressed the chips and converted them into spongy materials. Wood chips of L. leucocephala with or without de-structuring and de-structured wood chips followed by enzymatic treatment were subjected to Kraft pulping at different temperatures varying from 135 to 170 °C and active alkali varying from 12 to 20% (as Na2O) to observe effect on screened pulp yield and kappa number. The de-structured wood chips followed by enzymatic treatment produced a pulp yield of 48.2% and kappa number 18.6. L. leucocephala without de-structuring produced a pulp yield of 50.1% and kappa number 23.7. When the pulp was subjected to oxygen delignification to reduce kappa number in the vicinity of 18.6, pulp showed shrinkage by 6.64% compared to Kraft pulp of de-structured wood chips followed by enzymatic treatment. Kraft pulp produced from de-structured wood chips of L. leucocephala followed by enzymatic treatment showed net saving of US$ 163.15 per digester over Kraft pulp produced without de-structuring of wood chips of L. leucocephala. Moreover, the pulp obtained by de-structuring followed by enzymatic treatment showed improvement in pulp brightness and physical strength properties including tensile, tear, and burst index significantly compared to pulp obtained without de-structuring. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are natural polyesters which biodegrade in soils and oceans but have more than double the cost of comparable oil-based polymers. PHA downstreaming from its biomass represents 50% of its overall cost. Here, in an attempt to assist downstreaming, mastication of wet biomasses is tested as a new mechanical continuous biomass pretreatment with potential for industrial upscaling. Downstreaming conditions where both product recovery and purity are low due to the large amount of treated wet biomass (50% water) were targeted with the following process: extraction of 20 g in 100 mL solvent at 30 °C for 2 h, followed by 4.8 h digestion of 20 g in 0.3 M NaOH. Under the studied conditions, NaOH digestion was more effective than solvent extraction in recovering larger PHA amounts, but with less purity. A nearly 50% loss of PHA was seen during digestion after mastication. PHAs downstreamed by digestion with large amounts of impurities started to degrade at lower temperatures, but their melt elasticity was thermally stable at 170 °C. As such, these materials are attractive as fully PHA-compatible processing aids, reinforcing fillers or viscosity modifiers. On the other hand, wet biomass mastication before solvent extraction improves PHA purity and thermal stability as well as the melt rheology, which recovers the viscoelasticity measured with a PHA extracted from a dried biomass.

This study aimed at energy reduction during pulping of L. leucocephala by passing the wood chips through an impressafiner followed by xylanase pretreatment. An impressafiner compressed the chips and converted them into spongy materials. Wood chips of L. leucocephala with or without de-structuring and de-structured wood chips followed by enzymatic treatment were subjected to Kraft pulping at different temperatures varying from 135 to 170 °C and active alkali varying from 12 to 20% (as Na2O) to observe effect on screened pulp yield and kappa number. The de-structured wood chips followed by enzymatic treatment produced a pulp yield of 48.2% and kappa number 18.6. L. leucocephala without de-structuring produced a pulp yield of 50.1% and kappa number 23.7. When the pulp was subjected to oxygen delignification to reduce kappa number in the vicinity of 18.6, pulp showed shrinkage by 6.64% compared to Kraft pulp of de-structured wood chips followed by enzymatic treatment. Kraft pulp produced from de-structured wood chips of L. leucocephala followed by enzymatic treatment showed net saving of US$ 163.15 per digester over Kraft pulp produced without de-structuring of wood chips of L. leucocephala. Moreover, the pulp obtained by de-structuring followed by enzymatic treatment showed improvement in pulp brightness and physical strength properties including tensile, tear, and burst index significantly compared to pulp obtained without de-structuring. [ABSTRACT FROM AUTHOR]

In this work, the performance of a fed-batch high solids enzymatic hydrolysis of plantain pseudostem was studied at different particle sizes. The plantain pseudostem was pretreated with an alkaline hydrogen peroxide medium. Two set of experiments were carried out in a stirred tank bioreactor at substrate concentrations of 10% and 15% w/v, combined each one with particle sizes #20–40, #40–60, and # > 100, in 1 L of reaction volume. Particle sizes of #20–40 and #40–60 allowed around 99% of holocellulose conversion with a substrate concentration of 10% w/v, and 91% with 15% w/v; meanwhile enzymatic hydrolysis at particle size of mesh # > 100 yielded 70% and 73%, with a substrate concentration of 10% and 15% w/v, respectively. The conditions recommended for enzymatic hydrolysis at high solids of 15% w/v through fed-batch operation are particle size #20–40 and 6 h of reaction, achieving 91% of holocellulose conversion and 82 g/L of reducing sugars. [ABSTRACT FROM AUTHOR]

It has been known for some time that mechanical pretreatments of melts of long-chain branched polymers can increase the melt index and reduce the extrudate swell. This effect is not due to changes of the molar mass, its distribution, or the degree of branching because it may be reversed by long-term annealing or dissolution of the polymeric material and subsequent precipitation. Furthermore, molecular analysis shows a molecular structure unaltered by the treatment. The effect has not been completely understood up to now, and it is still an open question as to whether it is restricted to long-chain branched polymers, which have been preferably studied. This paper gives an overview of results from the literature and presents comparable measurements on a well characterized long-chain branched and a linear polypropylene. A wide range of linear and nonlinear rheological properties were studied, and it became obvious that long-chain branching is a strong structural precondition for the pronounced pretreatment effect occurring in processing. Based on this result, models from the literature are discussed, and it is found that chain alignment may qualitatively explain the rheological measurements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Shape characterizations of typical agricultural biomass are investigated. • Thermal conversion property of biomass combustion are studied. • An innovatively two-tube reactor is designed. • N1s spectra of the biomass and semicoke are investigated. • NO emission mechanism during biomass combustion is analyzed. The impact of mechanical pretreatment of corn straw (CS), pea straw (PS), and wheat straw (WS), on shape characterization and NO emissions during combustion were investigated in this research. Particle size ranges were obtained and characterized their shape factors using Image J correction. The thermal properties and NO emissions of the different-sized particles were investigated by TG-MS and fixed-bed reactor. Compared with CS and PS, WS is more likely to break into smaller particles due to its moderate strength. Amine-N completely disappeared after pyrolysis, whereas pyrrolic-N and pyridinic-N were the main N functionalities in char-N. During the volatile burning stage, the maximum peak of NO concentration was 270, 354 and 311 ppm for CS, PS and WS, respectively. NO was detected at a steady level during the semicoke combustion stage, and the duration increased with particle size. The NO concentration decreased sharply in a short duration during the fixed carbon combustion stage. [ABSTRACT FROM AUTHOR]

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The aim of this work was to study the feasibility of using orange tree pruning to obtain lignocellulose nanofibers (LCNFs) and their application in paperboard recycling process. The orange tree pruning was treated with an environmentally friendly process (13% NaOH on dry matter, at liquid/solid ratio of 8, 170 °C and 40 min). The cellulosic pulp obtained was used for the isolation of LCNFs by means of two different pretreatments, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated (TO-LCNFs) and mechanical refining (Mec-LCNFs), followed by high-pressure homogenization treatment. The reinforcement effect produced by the LCNF addition on paperboard recycled fiber was compared with other conventional industrial techniques such as chemical addition and mechanical beating. It was shown that TEMPO-mediated oxidation produces a greater delamination in fiber during its nanofibrillation, obtaining smaller width nanofibers with greater specific surface. The LCNF addition, especially TO-LCNFs, presents reinforcement effects comparable to those achieved by mechanical beating for the different mechanical properties, with the advantage of not modifying the fiber physically and increasing the numbers of recycling cycles. The economic analysis of both treatments shows that despite the Mec-LCNF cost is slightly higher, it is presented as an alternative to mechanical beating for use in paperboard recycling process. [ABSTRACT FROM AUTHOR]

Liquid hot water extraction followed by mechanical extrusion is a promising chemical-free pretreatment for cellulosic ethanol production from rigid hardwood. To alleviate the heavy dependence on chemical input of chemical pretreatments and make a better use of current idle thermo-mechanical pretreatment plant for mechanical pulp, a sequential chemical-free pretreatment approach, i.e., liquid hot water extraction followed by mechanical extrusion was investigated in this work. Its ability to fractionate hemicellulose while facilitating cellulose hydrolysis of rigid eucalyptus and aspen hardwood was assessed. The structural changes of lignin during liquid hot water extraction were elucidated using spectrum analysis. Cellulose accessibility to hydrolytic enzymes, cellulose hydrolysis yields and fermentation potential were also assessed. Results showed that the mild liquid hot water extraction recovered 54.0% and 38.1% of xylan hemicellulose from eucalyptus and aspen hardwood respectively, while causing limited lignin condensation reactions. Extending liquid hot water extraction time from 45 to 90 min significantly facilitated the subsequent mechanical deconstruction of both wood substrates without compromising their overall carbohydrate recovery. A maximum cellulose hydrolysis yield of 79.6% and nearly 100% (10 w/v solids loading, enzyme dosage, 20 mg g−1 cellulose) was observed on eucalyptus and aspen substrate respectively, which were feasible for further fermentation process. This work showed liquid hot water extraction followed by mechanical extrusion was a feasible pretreatment strategy for bioethanol production even the starting wood chip substrate was highly rigid. [ABSTRACT FROM AUTHOR]

Flow diagram of mechanical pretreatment and anaerobic digestion of Hybrid pennisetum. • Effects of particle size reductions on digestion of Hybrid pennistum was studied. • Changes were observed in chemical composition and CH 4 yield of different particles. • The highest methane yield 291.9 ± 4.7 mL/g VS was obtained in a size below 0.380 mm. • Excessive size reduction didn't improve CH 4 yield but enhanced the AD efficiency. This study investigated the effect of particle size on the performance of anaerobic digestion of Hybrid Pennisetum. Hybrid Pennisetum was ground and sieved to provide different particle sizes between 0.180 and 1.000 mm. Characterization of the different particle sizes suggested that the composition of ground Hybrid Pennisetum altered-carbohydrate content decreased and lignin content increased with a decrease in particle size. The highest specific methane yield was 291.9 ± 4.7 mL CH 4 ·g−1 VS at a particle size of 0.250–0.380 mm and this value plateaued as the particle size was reduced to below 0.250 mm. Excessive size reduction did not improve the methane yield but did result in a reduction of digestion time by 28.6–35.7%. The net energy output from the process was calculated at 300 kWh/t VS. Therefore, grinding was proved to enhance the anaerobic fermentation efficiency and energy output of Hybrid Pennisetum. [ABSTRACT FROM AUTHOR]

The mechanical pretreatments intensities on characteristics of cellulose nanocrystals (CNC) prior to acid hydrolysis was evaluated. The cellulose was submitted to mechanical pretreatment as: magnetic stirring (CNC st), blending (CNC bl) or grinding by 20 (CNC 20x) and 40 (CNC 40x) passages in a super mass colloid mill. Then, all samples were submitted to H 2 SO 4 hydrolysis and the CNC were evaluated by total mass yield (TMY%), rheological behavior, size distribution for width/length (WD), crystallinity index (CI%), OSO 3 − substitution degree (SD) and zeta potential (ζ). After hydrolysis samples exhibited the same SD (190 ± 5 mMol·kg−1), ζ (−55 ± 3 mV) and CI% (65 ± 2), differing only in TMY% and WD. The CNC st showed TMY% of 85%, WD of 8 ± 5 nm and 100–800 nm, with presence of cellulose nanofibers (CNF), suggesting incomplete hydrolysis. The CNC bl and CNC 20x revealed TMY% of 65 ± 1, but differed in WD of 8 ± 5 nm and 300 ± 200 nm and 8 ± 5 nm and 200 ± 170 nm, respectively. The results showed that the grinding mechanical pretreatment is mandatory for CNF isolation, but not for CNC. Stability profile after the hydrolytic procedure, CI%, morphology and similar character generated CNC with adequate features and good yield, by simple mechanical stirring or blending, reducing the production's cost and allowing industrial-scale production. [ABSTRACT FROM AUTHOR]

At present, "mechanochemistry" is synonymous with "grinding," according to the views of a significant number of scientists and technologists. Often, one comes across the opinion that "the less the particle size, the better." The cases of considering chemical reactions occurring during pretreatment, as well as considering changes in the ultrastructure of cell walls are extremely rare. Also, the wrong choice of the type of mechanical impact and the equipment used in most cases leads to excessive consumption of electrical energy and reduce economic efficiency. The review presents the currently available published data on mechanically activated processes for the pretreatment of plant materials and shows that when using mechanical treatment, it is necessary to look more closely at the phenomena occurring, rather than reducing everything to the production of fine and ultrafine powders. As a result of mechanical action, active surface radicals can form, hydrothermal chemical processes can occur, and mechanocomposites can form. The role of interphase processes, changes in surface chemistry, related dimensional effects, and the disordering of the crystal structure and amorphization should be taken into account. In addition, the physicochemical insights in mechanical pretreatment make it possible to more efficiently use the energy delivered to the material, and, consequently, increase the economic efficiency of the activation process. Image for Graphical Table of Contents: At the present time, "mechanochemistry" is synonymous with "grinding" according with views of significant part of scientists and technologists. Often one has to come across the opinion that "the less the particle size, the better." The cases of considering chemical reactions occurring during pretreatment, as well as considering changes in the ultrastructure of cell walls are extremely rare. The absence of a general theory describing the mechanochemical processing of plant raw materials makes it difficult to create cost‐effective technologies. The authors present modern published data on mechanically activated processes that take into account the generation of a new surface, chemical processes and the formation of composites occurring during mechanochemical action and subsequent relaxation. Their work is considered the role of interphase processes, changes in surface, the disordering of the crystal and ultrastructure of plant materials in mechanical pretreatment. [ABSTRACT FROM AUTHOR]

The commonly used hydrazine reduction method for the synthesis of Ni nanoparticles was integrated with the mechanochemical treatment of the nickel hydroxide precursors to modify the structural and catalytic attributes of the as-prepared metallic nickel materials. The precursors and the nanoparticles were studied by X-ray diffractometry, infrared spectroscopy, and dynamic light scattering as well as scanning electron microscopy. The changes in catalytic activities were followed in the Suzuki–Miyaura cross-coupling reaction between iodobenzene and phenylboronic acid and correlated with structural changes resulting from mechanochemical pretreatment. [ABSTRACT FROM AUTHOR]

Nowadays, many commercial kits allow the polymerase chain reaction (PCR) detection of Cryptosporidium deoxyribonucleic acid (DNA) in stool samples, the efficiency of which relies on the extraction method used. Mechanical pretreatment of the stools using grinding beads has been reported to greatly improve this extraction step. However, optimization of this key step remains to be carried out. Indeed, many parameters could influence the pretreatment performances, among which the modulation of the speed and duration of the grinding step, in addition to the physicochemical features of the grinding beads, have never been evaluated to date. In this study, eleven commercial mechanical pretreatment matrixes (Lysis matrix tubes®, MP Biomedical, Irvine, CA, USA) composed of beads with different sizes, shapes, and molecular compositions, were evaluated for their performances in improving Cryptosporidium parvum oocyst DNA extraction before amplification by using our routinely used real-time PCR method. As expected, the eleven commercial mechanical pretreatment matrixes showed varying performances depending on the composition, size, and shape. All in all, the best performances were obtained when using the Lysing matrix, including ceramic beads with a median size (diameter of 1.4 mm).

Cellulose nanofibrils, as a bionanomaterial with many promising properties, have great potential in composite applications. Herein, well-dispersed and uniform-sized cellulose nanofibrils (CNF) was successfully obtained from commercial bleached softwood kraft pulp, with yields of 79.15% via enzyme-assisted hydrolysis and a subsequent homogenization process. Field emission scanning electron microscope (FE-SEM) confirmed the fiber morphology. Water retention value (WRV) was increased from 107.32% of original pulp to 1383.92% of the resulting CNFs, while crystallinity had no significant changes. Fourier transform infrared (FTIR) spectroscopy indicated the addition of enzyme resulted in the removal of hemicelluloses and lignin. CNFs subjected to enzymatic treatment and homogenization had less entangled network, larger aspect ratio and higher transmittance than those from pure mechanical treatment. They exhibited well-dispersed in aqueous solution and uniform-sized in morphology. These advantages revealed enzyme-assisted process had a remarkable effect on the production of CNFs and made CNFs attractive for nanotechnology and nanomaterial.

In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.

This study quantifies the cost of cellulosic sugar production using a fully-mechanical pretreatment process and fuel pellets as a co-product. The pretreatment reduces softwood forest harvest residuals to micron-sized amorphous particles. Energy consumption is minimized using a three-stage milling process. A techno-economic analysis was completed for a milling facility with saccharification and wood pellet manufacture. For the base case, concentrated sugar syrup can be produced for $0.496/kg of sugar. Sensitivity analyses were used to determine cost controlling variables, optimize the sugar cost and found that siting for this technology needs to strongly consider electricity cost and to a lesser extent local feedstock availability. If the sugar produced in this process is used to generate biofuel and is qualified for RIN credits through a life-cycle analysis, the effective cost could be reduced by $0.04–$0.06/kg of sugar. An additional $0.067/kg savings is possible if the biofuel facility is located adjacent or on-site; the finished sugar syrup would not have to be concentrated for transportation. An optimized scenario, including the RIN credit, dilute sugar syrup, and favorable energy costs and consumption, could reduce the cost to $0.34/kg sugar compared to $0.496/kg for the base case.

Cellulose nanofibrils (CNFs) can prepare flexible nanomaterials with its large aspect ratio. Due to the supramolecular, cellulose fibers are difficultly dissociated to CNFs. In order to destroy this supramolecular structure and prepare high dispersible CNFs, the mechanical and chemical treatments are required. This study examined the effects of mechanical pretreatment and TEMPO-oxidation on the properties of CNFs preparing from bleached softwood kraft pulp. The total yield of TEMPO-oxidized cellulose nanofibrils (TOCNFs) reached 85 %. The morphology, carboxyl group content, crystallinity, surface charge, self-assembling properties, and optical transmittance of the corresponding TOCNFs suspension were investigated. The transmittance of TOCNFs suspension was 95.1 % at 600 nm wavelength and its corresponding ζ- potential was -61.3 mV, indicated that the strong electrostatic repulsion between TOCNFs was the most significant factor on the highly transparent TOCNFs suspension in water. Furthermore, the mostly negative charged TOCNFs obtained by freeze drying assembled into the finest and most uniform networked structure. Such highly transparent, functionalized, selfassembled cellulose nanofibrils are favorable in transparent films, flexible displays and electrochemistry materials. [ABSTRACT FROM AUTHOR]

Lignocellulosic substrates are associated with limited biodegradability due to the structural complexity. For that reason, a pretreatment step is mandatory for efficient biomass transformation which will lead to increased bioenergy output. The aim of the present study was to assess the efficiency of two pretreatment machines to enhance the methane yield of meadow grass. Specifically, the application of shearing forces with a rotated plastic sweeping brush against a steel roller significantly increased biomass biodegradability by 20% under relatively gentle operation conditions (600 rpm). The more intense operation (1200 rpm) was not associated with higher methane yield enhancement. Regarding an alternative machine, in which the brush was replaced with a coarse steel roller resulted in a more distinct effect (+27%) despite the lower rotating speed (∼400 rpm). Moreover, the association of the substrate’s individual chemical components and the practical methane yield was assessed, establishing single and multiple linear regression models. However, the estimation accuracy was rather low with either single (regressor: lignin, R 2 : 0.50) or multiple linear regression analyses (regressors: arabinan-lignin-protein, R 2 : 0.61). Results showed that poorly lignified plant tissue containing relatively high fractions of protein and arabinan is more susceptible to anaerobic digestion. [ABSTRACT FROM AUTHOR]

Thermo-chemical pretreatments of biomass typically result in environmental impacts from water use and emission. The degradation byproducts in the resulting sugars can be inhibitory to the activities of enzymes and yeasts. The results of this study showed that combining existing commercial comminution technology can reduce total energy consumption with improved saccharification yield while eliminating chemical use. Impact mill was found to be the most efficient milling for size reduction of forest residual chips from ca. 2 mm to a specific value below 100 µm. The further micronization effectively disrupted the recalcitrance of the woody biomass and produced the highly saccharifiable substrates for downstream processing. In addition, extrusion can be integrated into a clean cellulosic sugar process for further fibrillation in place of the conventional mixing processing. The highest energy efficiency was observed on the impact-milled samples with 0.515 kg sugars kWh −1 . [ABSTRACT FROM AUTHOR]

In order to increase the methane yield from biomass, this paper investigates the mechanical pretreatment effect of a Hollander beater on the anaerobic digestion process of Pelvetia canaliculata macroalgae using a response surface methodology (RSM). Higher values on methane yield were obtained at lower F/I ratios, with an increase up to 2.5-fold at an F/I value of 0.3. A multi-objective optimization study was carried out with the aim of maximizing the methane yield while minimizing the pretreatment time. An optimum methane yield of 283 ml/gVS was obtained for 50 min pretreatment time and a ratio F/I of 0.3, which represents an increase of 45% compared to non-pretreated algae. [ABSTRACT FROM AUTHOR]

During anaerobic digestion of municipal solid waste, organic matter is converted to methane, carbon dioxide, and other organic and inorganic compounds through a complex cooperation among different microbial groups with different metabolic activities. Here, culture-dependent and independent approaches provided evidence for examining the relationship between bacterial and archaeal communities and methane production in a pilot-scale anaerobic digestion. The abundance of aerobic and anaerobic functional groups of C and N cycles, such as cellulolytic, pectinolytic, amylolytic and proteolytic bacteria, was high at the beginning of the experiment and was drastically decreased after anaerobic digestion. In contrast, the ammonifiers increased in the biogas producing reactors in a higher pH environment. The methanogenic archaeal genera recovered were Methanobrevibacter , Methanobacterium , Methanoculleus and Methanocorpusculum , thus indicating that methane was formed primarily by the hydrogenotrophic pathway in the reactors. Moreover, the mechanical pretreatment effects, as well as the effect of pelleted manure as inoculum, were considered. The highest methane production was detected in the biodigesters with minced organic waste, thus indicating that pre-treatment of a heterogeneous starting matrix was essential for improving biogas production and stabilizing the process. [ABSTRACT FROM AUTHOR]

Impact of planetary ball milling on pre-milled wood fiber was studied to improve efficiency of energy consumption for bioconversion using post-harvest forest residuals. Crystalline cellulose decreased from 40.73% to 11.70% by ball milling. Crystallinity index of ball milled wood samples had a negative correlation with glucose yield (r = −0.97, p  < .01), xylose/mannose (r = −0.96, p  < .01), and a positive correlation with median particle size (r = 0.77, p  < .01). Range of glucose yield and xylose/mannose yield for ball milled samples was found to be 24.45–59.67% and from 11.92% to 23.82%, respectively. Morphological changes of the lignocellulosic biomass were observed; the compact fiber bundles of the forest residuals were cleaved to smaller particles with lower aspect ratio with increasing intensity of ball milling. The required energy ranged from 0.50 to 2.15 kWh/kg for 7–30 min of milling respectively. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the efficiency of a mechano-enzymatic deconstruction of two macroalgae species for sugars and bioethanol production, by using a new enzymatic cocktail (Haliatase) and two types of milling modes (vibro-ball: VBM and centrifugal milling: CM). By increasing the enzymatic concentration from 3.4 to 30 g/L, the total sugars released after 72 h of hydrolysis increased (from 6.7 to 13.1 g/100 g TS and from 7.95 to 10.8 g/100 g TS for the green algae U. lactuca and the red algae G. sesquipedale, respectively). Conversely, total sugars released from G. sesquipedale increased (up to 126% and 129% after VBM and CM, respectively). The best bioethanol yield (6 geth/100 g TS) was reached after 72 h of fermentation of U. lactuca and no increase was obtained after centrifugal milling. The latter led to an enhancement of the ethanol yield of G. sesquipedale (from 2 to 4 g/100 g TS). [ABSTRACT FROM AUTHOR]

We determined the potential of three mechanical pulverizers—a continuous ball mill (CBM), an air classifier mill (ACM), and a high-speed mill (HSM)—in the continuous pretreatment of corn stover. The mean diameters of the pulverized biomasses were not significantly different in the three cases, and the glucose yields from the CBM-, ACM-, and HSM-pulverized samples were 29%, 49%, and 44%, respectively. The energy requirements and process capacities for the ACM and HSM were similar. We conclude that the ACM and HSM could be used in the continuous pretreatment of corn stover and would be useful in biofuel production.

The hierarchical structure of wood cell walls resulting from complex arrangement and distribution of the heterogeneous components is considered to impact significant impediment to enzymatic hydrolysis of cellulose for biofuels. In this work, micronized wood with significant cell wall ultrastructural deconstruction were effectively produced from ring and puck milling within 12 min. In a subsequent enzymatic hydrolysis, micronized wood resulted in increase of cellulose hydrolysability by 4–14 folds over that of starting material. The underlying mechanism towards facilitating enzymatic hydrolysis was studied through delineating the ultrastructural changes and alternation of cellulose chemistry in micronized wood cell wall using SEM, TEM, CLSM, GPC, XRD, HPLC and Simon’s staining techniques. Electronic microscopy revealed distinct stages of wood cell wall deconstruction that was coincident with particle size reduction, including cell fracture and delamination, cell wall disintegration, and amorphization of cell wall fragments. Simons’ staining results also indicated increasing substrate accessibility and porosity of micronized wood, likely due to the ultrastructure alternation of cell walls. GPC and XRD revealed significant decrease of cellulose degree of polymerization (DP) and crystallinity. The correlation of these factors with cellulose hydrolysability was studied and further arranged in order through principal component analysis. The major positive factors affecting hydrolysability were surface accessibility and porosity, while cellulose crystallinity and DP were the major negative factors accompanied by particle size. The established weighed order of factors behind hydrolysability provides insights of lowering cell wall structural recalcitrance by mechanical manner. [ABSTRACT FROM AUTHOR]