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[Display omitted] • Comparison of different physical and enzymatic OFMSW pre-treatments. • Study of the pre-treatment effects on both the AD products: biogas and digestate. • Evaluation of the most energetically sustainable AD configurations. • Analyses of digestate quality in terms of nutrient content for the application as fertilizer. • UPP2 and cavitation are the best enzymatic and physical pre-treatments, respectively. This study optimized the anaerobic digestion (AD) of separated collected organic fractions of municipal solid waste (OFMSW) to produce energy and digestate as biofertilizer. Due to OFMSW's partial recalcitrance to degradation, enzymatic (UPP2, MCPS, USC4, USE2, A. niger) and physical (mechanical blending, heating, hydrodynamic cavitation) pre-treatments were tested. Experimental and modeling approaches were used to compare AD performance regarding energy sustainability and digestate quality. Digestate was separated into solid and liquid fractions, and then chemically and physically characterized by investigating the nutrient release mechanisms. Principal Component Analysis was applied, equally weighing energy and digestate productions. Unlike previous studies focusing only on biogas, this study evaluated the effects of pre-treatments on both biogas and digestate production, viewing AD as a biorefinery process for urban waste valorization. Results showed that all pre-treatments were energetically sustainable, but enzymatic pre-treatments yielded digestates richer in nutrients (increase of 80% N, 200% P and 150% K as compared to OFMSW) and with greater organic matter degradation compared to physical pre-treatments. The liquid fraction of digestate from enzymatic pre-treatments had higher nutrient concentrations, while those from physical pre-treatments had more balanced nutrient content, making them more suitable for fertigation. [ABSTRACT FROM AUTHOR]

The paper is focused on steel surface processing to ensure an improved adhesion of applied powder layer. Mechanical pre-treatment, chemical pre-treatment and their combination were used to compare their results with each other and to find out the pre-treatment that affected the final outcome the most. The final score was determined by the grid method. The outcome displayed a huge mutual dependency between the result and a kind of various surface treatments. The method with no pre-treatment was by far the worst, followed by the mechanical pre-treatment only, followed by the chemical pre-treatment only, and finally by their combination. The time of blasting affects the final outcome. Through the grid method, coating thickness, and aesthetic test it was confirmed that an optimal blasting time of 5 min provides the best outcome.

Cattle manure usually contains a proportion of carbohydrates in the form of organic residues from incompletely digested feed and farm husbandry practices. These are not usually available for biogas production due to the long fermentation time. This paper investigates the optimal application of alkali, NaOH and KOH and mechanical pre-treatments to improve the degradation of the lignocellulosic content and the potential biogas yields from a local farm in Bavaria, Germany. Parameters such as temperature, pH, soluble chemical oxygen demand, organic acids, dry matter and volatile solids were analysed for this purpose. Alkali pre-treatments in 0.2, 0.1 and 0.05 M NaOH concentrations were tested in single mode and combined with shredding in batch experiments. The maximum increment of the soluble chemical oxygen demand during the pre-treatments took place during the first 50 h of experimentation, and it showed an improvement of 10,060.0 ± 8% mg/L s COD after the application of 0.2 M NaOH compared to the untreated substrate, which had an initial value of 2145.0 ± 8% mg/L s COD. Pre-treatments with 0.1 and 0.05 M NaOH concentrations showed similar s COD increments, with an additional 6860.0 ± 8% mg/L s COD and 8505.0 ± 8% mg/L s COD, respectively. The pH values varied strongly after the addition of the pre-treatment chemicals, with a continuous pH of 12 by 0.2 M NaOH during the 7 days of pre-treatment. Batch biogas experiments were done by applying 0.05 M NaOH and 0.05 M KOH pre-treatments in single mode and combined with shredding. The chemically pre-treated substrates showed a faster biogas production with an advantage of 18 days in comparison to the untreated cattle manure by a biogas yield of 350.0 NL/kg VS. All experiments were done under mesophilic conditions. [ABSTRACT FROM AUTHOR]

This work investigates the effects of PFI mill refining and especially, its contribution to the defibrillation of cellulose fibers, as the mechanical pretreatment step in the production of cellulose nanofibrils (CNFs). Hardwood and softwood kraft pulps were refined at varying PFI mill revolutions and further processed using an ultrafine-friction grinder at predefined low specific energy conditions to produce aqueous CNF suspensions. The degree of fibrillation of the CNFs was assessed by studying the properties of the suspensions and anisotropic foams prepared by ice templating. The differences in aspect ratios of the hardwood and softwood CNFs refined at different PFI mill revolutions resulted in anisotropic foams of distinct porous structures and mechanical performance. The lower the CNF aspect ratio, the weaker the anisotropic foams. Softwood CNF foams demonstrated higher mechanical performance than hardwood foams, mainly due to the inherent differences in structure and morphology between these two fiber types. The presence of hemicelluloses in the CNF suspensions, however, also explained the observed differences in compressive behavior, by their action on the fibril-fibril interactions in the foam cell walls. This study thus sheds light on the role of PFI mill refining as a mechanical pretreatment for CNF production. Low PFI mill revolutions were preferred for optimal fibrillation of both hardwood and softwood fibers prior to the high-shear mechanical treatment. Conversely, a too intense pre-refining resulted in CNF materials with poor performance, due to a sharp decrease in the fiber aspect ratio that inhibited the formation of a percolating network and fibril-fibril interactions. [ABSTRACT FROM AUTHOR]

The extraction of intracellular constituents from recalcitrant microalgae strains stands as a significant challenge and a crucial bottleneck in microalgae processing. This study presents a novel enzymatic approach coupling mechanical lysis through sand milling without commercial glass or zirconium beads, with subsequent snailase treatment, resulting in improved cell wall breakdown and increased release of valuable constituents. The selected microalga was Chlorella sp. L06, renowned for its sturdy cell wall structure. Initial experiments involving sand milling unveiled substantial release of proteins (1.19 mg/mL) and chlorophyll (1.80 of absorbance at 680 nm), underscoring effective cell disruption. Remarkably, the application of snailase after sand milling produced noteworthy outcomes, fostering enhanced cell wall degradation and liberating a spectrum of constituents, encompassing soluble reducing sugars (1.13 mg/mL), proteins (2.28 mg/mL), and chlorophyll (2.83 of absorbance at 680 nm). The process was optimized by applying the Box-Behnken design, which revealed distinct operational parameters that significantly improved the release of soluble sugars and proteins by 46 % and 12.7 %, respectively. Moreover, the presence of snailase also showcased a protective antioxidant effect on chlorophyll during the hydrolysis, shedding light on its multifaceted role in the hydrolysis process. This study introduces an advantageous strategy for efficiently valorizing microalgae biomass using the synergistic potential of mechanical lysis and enzymatic treatment. Furthermore, the developed method contributes achieving promising, sustainable microalgae-based biorefineries. [Display omitted] • Beadmilling with sand releases proteins and pigments. • Snailase enhances the extraction of soluble sugars. • Optimization amplifies the release of soluble sugars and proteins. • Snailase enhances the preservation of chlorophyll. [ABSTRACT FROM AUTHOR]

This study proposed an evaluation of enrichment processes of obsolete Printed Circuit Boards (PCBs), by means of gravity and electrostatic separation, aiming at the recovery of metals. PCBs are the most important component in electronic devices, having high concentrations of metals and offering a secondary source of raw materials. Its recycling promotes the reduction in the environmental impacts associated with its production, use, and disposal. The recovery method studied started with the dismantling of the PCB, followed by a comminution and granulometric classification. Subsequent magnetic, gravity, and electrostatic separations were performed. After the separations, a macroscopic visual evaluation and chemical analysis were carried out, determining the metal content in the concentrate products. The results obtained from gravity separation showed a product with metallic concentrations of 89% and 76% for particle sizes of 0.3–0.6 mm and 0.6–1.18 mm, respectively. In electrostatic separation, the product obtained was 88% for the lower particle size (1.18 mm.

• The efficiency of two mechanical pre-treatment systems for biowaste were compared. • Up to 99% of the plastics input could be removed. • Small plastic and inert particles were still found in the pre-treated biowaste. • Unpacking machine showed better impurities removal efficiency than piston press. The treatment of source-separated biowaste is still a challenge due to its high proportion of impurities. Biowaste bins are intended exclusively for the collection of biodegradable matter, such as food, kitchen and garden waste. However, plastics, metals, glass and textiles are also found in biowaste bins. If not properly removed, these impurities cause problems to the treatment facility and depreciate the quality of the final product, when the biowaste is converted to compost. There is ongoing discussion whether the existing treatment systems are able to remove impurities, especially plastics, from biowaste thoroughly enough to ensure that the produced compost complies with state regulations. In this work, two wet mechanical pre-treatment systems were tested for their efficiency to remove impurities. The first system consisted of a screw mill, a star screen, and a food unpacking machine (process I). The second system consisted of a shredder, followed by a piston press with 12 mm pore size (process II). Both processes produced a dry output, which contained the concentrated impurities, and a wet output, which could be used as substrate for anaerobic digestion. Results showed that, although 99% of the incoming plastics were efficiently removed in process I, the impurities concentration was still too high to meet the legal standards of plastics concentration in the final product, according to the German Federal Compost Quality Association (Bundesgütegemeinschaft Kompost e.V.). The removal efficiency of glass particles was low for both processes: at least 80% of the incoming particles were transferred to the wet output. [ABSTRACT FROM AUTHOR]

Due to the increasing demand for glass fibre-reinforced epoxy resin composites (GFRC), huge amounts of GFRC waste are produced annually in different sizes and shapes, which may affect its thermal and chemical decomposition using pyrolysis technology. In this context, this research aims to study the effect of mechanical pre-treatment on the pyrolysis behaviour of GFRC and its pyrolysis kinetic. The experiments were started with the fabrication of GFRC panels using the vacuum-assisted resin transfer method followed by crushing the prepared panels using ball milling, thus preparing the milled GFRC with uniform shape and size. The elemental, proximate, and morphology properties of the panels and milled GFRC were studied. The thermal and chemical decomposition of the milled GFRC was studied using thermogravimetric coupled with Fourier-transform infrared spectroscopy (TG-FTIR) at different heating rates. Meanwhile, the volatile products were examined using TG coupled with gas chromatography–mass spectrometry (GC-MS). The TG-FTIR and TG-GC-MS experiments were performed separately. Linear (Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Friedman) and nonlinear (Vyazovkin and Cai) isoconversional methods were used to determine the pyrolysis kinetic of the milled GFRC based on thermogravimetry and differential thermal gravimetry (TG/DTG). In addition, the TG/DTG data of the milled GFRC were fitting using the distributed activation energy model and the independent parallel reactions kinetic model. The TG results showed that GFRC can decompose in three stages, and the main decomposition is located in the range 256–500 °C. On the other hand, aromatic benzene and a C-H bond were the major functional groups in the released volatile components in FTIR spectra, while phenol (27%), phenol,4-(1-methylethyl) (40%), and p-isopropenylphenol (34%) were the major compounds in GC-MS analysis. Whereas, the kinetic results showed that both isoconversional methods can be used to determine activation energies, which were estimated 165 KJ/mol (KAS), 193 KJ/mol (FWO), 180 KJ/mol (Friedman), 177 KJ/mol (Vyazovkin), and 174 KJ/mol (Cai).

Enhanced biogas production from anaerobic co-digestion of pig slurry and horse manure with mechanical pre-treatment. In this study, co-digestion of horse manure and pig slurry was investigated in a continuously stirred tank reactor, with a mechanical pre-treatment. Experiments were conducted at 37°C, with hydraulic retention times of 23 days and increasing shares of horse manure, corresponding to different horse manure to pig slurry ratios (HM:PS) equal to 0:100, 10:90, 13:87 and 20:80, in terms of percentage of inlet volatile solids (%VS inlet). The results show that the best synergetic effect between the microbial consortia of pig slurry and the high Carbon to Nitrogen ratio (C/N) of horse manure is obtained for the mixture of 20:80%VS inlet, yielding the highest specific methane production (SMP = 142.6 L kgTCOD−1) and the highest soluble chemical oxygen demand (SCOD) reduction (68.5%), due to the high volatile dissolved solids content and soluble chemical oxygen demand to total chemical oxygen demand ratio (SCOD/TCOD). Thus, co-digestion of horse manure and pig slurry is shown to be a promising approach for biogas production and as a waste treatment solution. Furthermore, the analysis provides a methodology for the pre-treatment of these substrates and to investigate into the best combination for improved biogas production. [ABSTRACT FROM AUTHOR]

Abstract Cladophora sp. and Ulva intestinalis are green macroalgae abundantly available in the Baltic Sea. Their low degradability could hamper the fully exploitation as resource for energy recovery through anaerobic digestion. For this reason, a co-digestion with lignocellulosic biomass represents a viable solution. This study aims to assess the potential effectiveness of the use of seaweed from Latvian nearshore co-digested with lignocellulosic biomass both in terms of increased BMP and kinetic constant of biodegradability. Specifically, biomethane potentials (BMP) in batch tests of 100 ml were assessed co-digesting Cladophora sp. and Ulva intestinalis from the Gulf of Riga with wheat straw and straw pellet from Brescia Region (Italy). The BMP tests were performed to evaluate the synergetic effect of co-digestion through a synergy index. A mechanical pre-treatment was also executed and its final effect assessed on the mono- and co-digestion experimental trials. The co-digestion ratio (seaweed/lignocellulosic biomass) used based on the volatile solids content was 1:1. The used ratio substrate-to-inoculum was 1:3 on total solid base. The inoculum use was sewage sludge was collected waste water treatment plant in the Riga district. Two different rounds of experiments with duration of 30 days were performed in order to have a more consistent analysis of results. Results for mono-digestion show the lowest BMP for Ulva intestinalis (277.7 ± 8.6 mL CH 4 /g VS) and the highest for the Cladophora sp. 523.3 ± 23.24 mL CH 4 /g VS. The straw pellet and wheat straw present values in a range of 395.6 ± 25.07 mL CH 4 /g VS and 470.4 ± 7.40 respectively. The effect of the co-digestion results in a slight increase of the synergy index (i.e. from 1.9% to 4.7%) but not for all the co-digestion trials. The higher effect was detected for co-digesting of finely treated straw pellet and Ulva intestinalis. The kinetic degradation constant improvements are evident for all the tested trials with the most evident effect for finely treated Ulva intestinalis in the mono-digestion conditions (i.e. 53.8%). The experiments show that the co-digestion with seaweeds and lignocellulosic can be beneficial. [ABSTRACT FROM AUTHOR]

The recycling of Waste Electrical and Electronic Equipment (WEEE) has attracted a notable amount of interest during the last few decades due to the high metal concentrations and substantial increase in the growth rate of WEEE. In addition, higher recovery and recycling rates required by the European Union demand more comprehensive treatment of WEEE. However, complex product design and the presence of harmful substances together with low concentrations of special metals present challenges for processing. This study examines the effect of mechanical treatment of mobile phones on metal concentrations in the printed circuit assembly (PCA) fraction compared to manual dismantling. The designed mechanical treatment process including crushing, sieving, magnetic-, eddy current- and sensor-based separation was able to separate plastics, ferrous metals, PCA and stainless steel for further treatment. The process separated PCA with an efficiency of 85%. However, the quality of the separated PCAs was poor compared with “pure” manually dismantled PCAs. The primary crushing of mobile phones destroys PCAs thus resulting in the loss of especially precious metals used in the connector coatings and in the surface-mounted components. As a result, the theoretical value of the produced PCA fraction is only half compared to using manual dismantling. However, high labour costs in western countries and low capacity may hinder the feasibility of hand dismantling. [ABSTRACT FROM AUTHOR]

A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90 °C/120 min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses. [ABSTRACT FROM AUTHOR]

Recent studies have reported improved biogas and methane yield from marine biomass when the particle size is mechanically reduced and the specific surface area available to enzymes is increased prior to anaerobic incubation. Although the advantage of reducing the particle size has been identified, an ideal particle size that would offer greater yield with a positive energy balance has not been identified for such substrate to date. As particle size reduction by mechanical means is often highly demanding in energy, this paper attempts to fill this gap for macroalgal biomass by identifying the particle size distribution allowing the highest biogas and methane yields obtained in a previous work. The study estimated that when about 80% of the particles are sized below 1.6 mm 2 , a biogas and methane yield improvement of up to 52% and 53% respectively can be achieved. The results are discussed in relation to the biogas yield, related methane content and potential inhibitory phenomena occurred during the fermentation. [ABSTRACT FROM AUTHOR]

This study proposed an evaluation of enrichment processes of obsolete Printed Circuit Boards (PCBs), by means of gravity and electrostatic separation, aiming at the recovery of metals. PCBs are the most important component in electronic devices, having high concentrations of metals and offering a secondary source of raw materials. Its recycling promotes the reduction in the environmental impacts associated with its production, use, and disposal. The recovery method studied started with the dismantling of the PCB, followed by a comminution and granulometric classification. Subsequent magnetic, gravity, and electrostatic separations were performed. After the separations, a macroscopic visual evaluation and chemical analysis were carried out, determining the metal content in the concentrate products. The results obtained from gravity separation showed a product with metallic concentrations of 89% and 76% for particle sizes of 0.3–0.6 mm and 0.6–1.18 mm, respectively. In electrostatic separation, the product obtained was 88% for the lower particle size (<0.3 mm) and 62% for particles sizes >1.18 mm. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies on substrates for biogas production have shown that different types of pre-treatments make the material more accessible for microbial degradation by breaking down the complex structure of the organic material, thereby increasing their potential for gas production. In this paper, two different mechanical pre-treatment apparatus, i.e. a Grubben deflaker (Gd) and a Krima disperser (Kd), were tested in a full scale setup to evaluate their effects on ley crop silage. The treatments were investigated with regard to their effects on particle size, methane potential, capacity and energy balance. The results after 115days of incubation in a batch assay show that methane production increased by 59% and 43% respectively after grinding with Gd and Kd. In both treatments, 90% of the ley crop was ground to particles of less than 2mm and more than 50% of the sample was reduced to particles smaller than 0.125mm. The energy balance was positive for Gd and around the break-even point for Kd. Analysis of the setup showed that Kd had almost twice the capacity of the Gd. If installed in the co-digestion biogas plant Växtkraft in Västerås, Sweden, the Gd and Kd could increase annual biogas yields by 790MWh and 585MWh respectively. [Copyright &y& Elsevier]

Abstract: In this paper the recycling of nickel metal hydride (NiMH), lithium ion (Li-ion) and primary lithium batteries was examined. Three mechanical routes of treatment were developed for each type recovering mainly three fractions: ferrous metals, non-ferrous metals and electrodic powders. The above mentioned types of spent batteries were also treated together by a unique mechanical route, obtaining in this way a powder enriched in cobalt, nickel and manganese which can be further extractable by chemical leaching. Experimental tests of solvent extraction were performed on synthetic leach liquors simulating a feed mixture of spent devices with weight composition 40% NiMH, 40% primary lithium, and 20% Li-ion (as determined by manual sorting of 3 tons of end of life batteries collected in Northern Italy). Under these conditions nickel and cobalt can be easily separated by using Cyanex 272 (stoichiometric ratio Cyanex/Co = 4, pH 5–6), but in presence of manganese Cyanex 272 loses its selectivity towards cobalt. Thus manganese must be preliminarily removed by using D2EHPA (stoichiometric ratio D2EHPA/Mn = 2, pH 4). Mechanical treatments and hydrometallurgical section to recover metals from electrodic powder are unavoidable operations in order to recover at least 50% of batteries as weight according to European Guideline 2006/66/EC. [Copyright &y& Elsevier]

Abstract: In order to ensure a stable and reliable operation of municipal MBR plants, an enhanced mechanical pre-treatment of the raw wastewater is essential. Removal of hair, fibrous material and other contraries which can lead to operational problems at the membrane modules is of particular importance. As the number of full scale applications is continuously increasing, now appropriate investigations can be carried out to determine the removal efficiency of different units (screens, sieves) or different combination of units (multi staged system). First results of such investigations on two German MBR plants were already presented [F.-B. Frechen, W. Schier and M. Wett, Water Practice & Technology, Vol. 1, No. 3, IWA Publishing, 2006, doi: 10.2166/WPT.2006057.]. In 2006, DESEE executed further investigations on another three wwtps in The Netherlands, UK and Germany. This paper summarizes the results, thus updates the information available, discusses the present findings and gives an outlook on future developments. [Copyright &y& Elsevier]

Abstract: Since the mid nineties the MBR technology has been introduced into municipal wastewater treatment in Europe. First wwtps went in operation performing a conventional mechanical treatment without any advanced mechanical pre-treatment unit. After a short operation period braids were hanging between the membranes and hence module sludging was observed. Thus, mechanical pre-treatment was upgraded introducing sieves primarily to reduce hairs and fibrous substances. Today, however, knowledge is still relatively poor concerning effectiveness and treatment efficiency of a large number of aggregates that had been brought to market, varying in gap size, gap geometry and others. This paper describes the fundamentals of sieving, gives an overview of mechanical pre-treatment on municipal MBR plants and finally presents the results of investigations quantifying and comparing the removal efficiency of different types of sieves. [Copyright &y& Elsevier]

Due to the increasing demand for glass fibre-reinforced epoxy resin composites (GFRC), huge amounts of GFRC waste are produced annually in different sizes and shapes, which may affect its thermal and chemical decomposition using pyrolysis technology. In this context, this research aims to study the effect of mechanical pre-treatment on the pyrolysis behaviour of GFRC and its pyrolysis kinetic. The experiments were started with the fabrication of GFRC panels using the vacuum-assisted resin transfer method followed by crushing the prepared panels using ball milling, thus preparing the milled GFRC with uniform shape and size. The elemental, proximate, and morphology properties of the panels and milled GFRC were studied. The thermal and chemical decomposition of the milled GFRC was studied using thermogravimetric coupled with Fourier-transform infrared spectroscopy (TG-FTIR) at different heating rates. Meanwhile, the volatile products were examined using TG coupled with gas chromatography–mass spectrometry (GC-MS). The TG-FTIR and TG-GC-MS experiments were performed separately. Linear (Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Friedman) and nonlinear (Vyazovkin and Cai) isoconversional methods were used to determine the pyrolysis kinetic of the milled GFRC based on thermogravimetry and differential thermal gravimetry (TG/DTG). In addition, the TG/DTG data of the milled GFRC were fitting using the distributed activation energy model and the independent parallel reactions kinetic model. The TG results showed that GFRC can decompose in three stages, and the main decomposition is located in the range 256–500 °C. On the other hand, aromatic benzene and a C-H bond were the major functional groups in the released volatile components in FTIR spectra, while phenol (27%), phenol,4-(1-methylethyl) (40%), and p-isopropenylphenol (34%) were the major compounds in GC-MS analysis. Whereas, the kinetic results showed that both isoconversional methods can be used to determine activation energies, which were estimated 165 KJ/mol (KAS), 193 KJ/mol (FWO), 180 KJ/mol (Friedman), 177 KJ/mol (Vyazovkin), and 174 KJ/mol (Cai). [ABSTRACT FROM AUTHOR]