Volume 38, Issue 4

Trace elements have a significant effect on biochemical reactions and therefore the presence of optimum levels of trace elements is essential for bioreactor performances. In this study, the effects of five trace elements on biomethane production have been investigated. Experimental studies have been carried out with multiple batch reactors at 15 day HRT and mesophilic temperatures. The optimum concentrations for each of the trace elements Fe, Cu, Ni, Co and Mg were found as 5, 0.5, 0.5, 0.5 and 100 mg/L, respectively. Among tested trace elements, Cu was the one which provided the highest biomethane production. Cu addition was resulted in a 46 % increase in biomethane production followed by Co with 24 %. The biomethane production rate for these two trace elements was 191.70 and 110.77 ml CH 4 /g COD, respectively. Optimum levels for Ni, Fe and Mg increased biomethane production rate by approximately 14.3, 10 and 17 % compared to control groups, respectively. Because the exact amount of trace element requirement for each industry/reactor is different, specific case studies should be performed for each application. These results could be used as initial trace element concentrations for further continuous studies.

Water-dispersible paper is useful for packaging applications as it disintegrates into its fibers after usage, and also is a fully biodegradable material. Here, we first introduce a laboratory testing method for the disintegration performance of different paper grades under low agitation in water. Then a quantitative analysis on the technological and physical mechanisms responsible for dispersibility of paper is performed. We identify lignin content, degree of refining and addition of starch as relevant factors reducing paper dispersibility. Addition of a debonding agent, a non-ionic surfactant, was not found to be effective here. We found a strong correlation of both, wet- and dry tensile strength to dispersibility. From all water absorption related paper properties only ultrasonic liquid penetration measurements were correlated to paper dispersibility. Principal component analysis revealed that paper strength and water penetration speed are not governed by different latent variables but instead are all strongly associated with the first principal component. This suggests that the same mechanisms are responsible for reduction of water penetration speed and wet/dry strength. Hence we suggest to decouple network strength and water penetration, e.g. by identifying suitable additives imparting bonding strength without reducing the access of water which is required to break the fiber–fiber bonds.

Sustainable coatings exhibit potential in enhancing oil resistance of packaging paper. Alkyl ketone dimer (AKD) was used to esterify sodium alginate (SA) to prepare water and oil resistant agent SAD. As SAD was coated on paper, it reduced the surface energy and blocked the fiber pores of paper, thus improving the barrier performance of paper. The oil resistance grade can reach grade 6 at coating amount of 2.13 ± 0.26 g/m 2 , which is qualified for food packaging. The coated paper also showed good barrier to hot castor oil. Resistance to organic solvent and water were also enhanced with initial water contact angle (WCA) increased to 69.2°. Compared with base paper, SAD coated paper had better mechanical properties and more importantly, coated paper can be effectively recycled to achieve green recycling.

Formaldehyde-free adhesives are gaining attention due to their compatibility with green production methods. Decorative base paper (DBP) is known for its physical strength and printability and has a high ability for absorbing aldehyde-free adhesives for impregnation. In this paper, DBP was prepared with TiO 2 and SiO 2 combined with polyvinyl alcohol (PVA), where the amount of TiO 2 was reduced in the pulp process. The prepared DBP was impregnated by aldehyde-free adhesive and hot-pressed on wood-based panels. The results showed that upon SiO 2 coating, the surface smoothness of base paper increased by 132.3 %, whereas the tensile strength increased by 33.6 %. Furthermore, the colour density of cyan, magenta, yellow and black colours increased by 75.4 %, 99.2 %, 51.9 % and 90.5 %, respectively. The surface properties like surface bonding strength and wear resistance of the covered wood-based panels were found to satisfy the standard requirements, which indicates the products can be used for furniture products.

This article describes the study of the effects of carbon nanoparticles on fibrous cellulosic webs. The handsheets were coated with coating colours containing graphene oxide (GO), carbon nanotube (CNT) and super conductive black carbon (SCBC) nanoparticles at different concentrations. The Raman method was used to assess the quality of the carbon materials and the changes in the band gap of the nanoparticles deposited on the handsheets. The influence of the type and content of the nanoparticles on the structural, mechanical, chemical and electrical properties of the composites was investigated and discussed. It was found that the range of failure modes and fracture surfaces seen in the SEM image is due to the influence of the different carbon materials as the main source of coating colour. The experimental percolation threshold curve and the total surface electrical resistivity of the samples were investigated. The SCBC coated samples exhibited low percolation threshold and comparatively high electrical conductivity at a certain maximum concentration. Each composite exhibited a pronounced stress distribution along the surface layer and the nanoparticle distribution was uniform. The surface resistance of the coated handsheets declined by about 14.103 times with the addition of only 1.0 wt% SCBC compared to the control sample. The composites coated with GO and SCBC nanoparticles at a concentration of 1.0 wt% had the highest tensile strength values.

Routinely, the mills perform programmed maintenance shutdowns (PMS) that can affect the characteristics of the effluents and the performance of the effluent treatment plant (ETP). A careful planning of the PMS, along with the use of industrial process sectorial spill control and the use of the emergency spill lagoon have considerably minimized these effects. The Suzano pulp mill located in Aracruz (Brazil) has three production lines and carry out, on average, PMS of each production line separately, every 15 months of operation. The purpose of the study was to evaluate the effects of the PMS on the effluent characteristics and performance of the ETP compared to the periods of normal operation. The results showed that during the PMS, the physicochemical characteristics of the raw and treated effluents were like those found during normal operation. The lower organic loads found in the effluents during the PMS periods were associated with the decrease of the flow rates and the increase of the hydraulic retention time of the ETP, causing a better performance of COD, BOD, TSS and AOX removal. A proper planning of the PMS improved the performance of the ETP and the treated effluent quality remained similar to those during the normal operating period.

An initial carbon emission calculation formula for the pulp molding industry was first proposed in accordance with the calculation guidelines provided by the Intergovernmental Panel on Climate Change (IPCC). The formula was primarily developed by utilizing the greenhouse gas accounting methods used in the pulp and paper industry and the life cycle assessment (LCA) theory. Carbon dioxide emissions coming into being during the production processes of dry-press and wet-press pulp molding were calculated individually, alongside the carbon emission factors throughout the lifecycle of the products. This study also delivers a comparative analysis of pulp molding products and similar cushion packaging materials. Moreover, the findings reveal that during the production phase, particularly in the formative stages of pulp molding, substantial carbon dioxide emissions would be produced, with dry-press pulp molding products exhibiting markedly higher carbon emission factors than their wet-press counterparts. The primary objective of achieving low-carbon transformation for the pulp molding industry was to reduce the carbon emissions caused by the forming process, primarily by improving the forming process and enhancing energy efficiency or utilizing clean energy.

The industrial sector is increasingly interested in the production of yarns based on renewable, efficient, innovative, and ecological resources. Among these precursors, cellulose nanofibrils (NFC) have gained attention due to their interesting characteristics for the development of new products. However, their dimensions pose challenges in their use. Therefore, this study aimed to analyze the influence of NFC concentrations and dimensions on the quality of bicomponent yarns. The bicomponent yarns were produced using a coaxial needle and the dry–wet-spinning method. The outer layer was made of guar gum (3 % w/v) and the inner layer of NFC bleached at two different degrees of refining (NFC A and NFC B). Yarn production involved varying concentrations of NFC (4.5 %, 3.5 % and 2.5 % w/v) NFC, which were characterized by real density analyses, tensile strength, water absorption, thermogravimetry, and scanning electron microscopy. Guar gum showed more hydrophilic characteristics, and its delay in hardening caused a less circular section and flaps on the side of the yarn. NFC B exhibited the smallest average diameter, and higher concentrations resulted in yarns with greater mechanical strength, more circular cross-sections, and fewer microstructural defects.

This work describes an emulsification-solvent-evaporation method for the preparation of liquid-filled capsules made from cellulose acetate. Two different emulsification techniques were applied: bulk emulsification by high-shear mixing, and droplet generation using microfluidics. The bulk emulsification method resulted in the formation of oil-in-water emulsions composed of an organic mixture of isooctane and cellulose acetate in methyl acetate, and an aqueous phase of high-molecular-weight polyvinyl alcohol (PVA). Upon the solvent evaporation, the emulsion droplets evolved into isooctane-filled cellulose acetate capsules. In contrast, microfluidics led to the formation of monodisperse droplets composed of the aqueous PVA solution dispersed in the organic phase. Upon the solvent evaporation, the emulsion droplets evolved into water-filled cellulose acetate capsules. Owing to the thermoplastic properties of the cellulose acetate, the capsules formed with the bulk mixing demonstrated a significant expansion when exposed to an increased temperature. Such expanded capsules hold great promise as building blocks in lightweight materials.

Separator plays a key role in the safety and performances of lithium-ion batteries with the needs of good thermal stability and wettability. Compared with the commercial separator mainly made by polyolefins in organic solvents, the electrospinning of lignin/polyvinyl alcohol in an aqueous solution has been investigated as a green and economically viable method to produce high-performance separators without any other chemical additives. Lignin/polyvinyl alcohol (mass ratio: 3:7) nanofiber separators outperform commercial polypropylene separators in terms of porosity (71 %), liquid absorption (373 %), and outstanding thermal stability at 200 °C. Additionally, Li-ion battery cells that were constructed using different separators were assessed to demonstrate favorable electrochemical performance. The results showed that fabricated Li-ion battery with Lignin/polyvinyl alcohol (mass ratio: 3:7) nanofiber separators possesses a superior capacitance of 154.1 mA h g −1 at 0.5 C, and maintained outstanding cycle stability after 50 times of charging and discharging process at 0.5 C with the capacitance retention rate up to 98.7 %. The facile and sustainable synthesis strategy of lignin-based separator materials for Li-ion batteries developed in this work provides new perspectives for related research, especially based on environmentally friendly aqueous systems.

The depolymerisation of softwood kraft lignin was investigated, under hydrothermal conditions at 290 °C and 250 bar, with guaiacol in the reactor feed to evaluate its impact on the formation of char and on the molecular weights of the products. The effect of residence time was investigated in the time span 1–12 min. Lignin is depolymerised during the process and guaiacol is both formed and consumed during the reaction, with clearly noticeable changes as early as in the first minute of reaction. Although the addition of guaiacol in the reactor feed causes a reduction in the weight average molecular weight of the products, the yield of char increases. Longer residence times result in repolymerisation of the reaction products as well as a further increase in the yield of monoaromatic components and char.

Lignin, as a widely distributed, renewable and environmentally friendly source of carbon, could been utilized for carbon nanofibers to not only maximize the usage of resources, but also expand the energy-related opportunities. In this research, flexible lignin-based carbon nanofibers are prepared by electrospinning lignin nanofibers in a new green aqueous solution of lignin and polyvinyl alcohol (PVA), which is then characterized by physical and chemical characterizations. The results reveal that optimal carbonization temperature of 800 °C shows great improvements on the structural properties of lignin-based carbon nanofibers, which can be applied as binder-free electric double layer capacitor (EDLC) electrodes with good flexibility. The 2032 type button battery has a superior electrochemical performance with a large specific capacitance of 217.2 F g −1 at a 0.2 A g −1 current density, and remarkable cyclic stability of 94.9 % capacitance retention even after 10,000 charge and discharge cycles, due to the abundance of mesoporous volume and large microporous surface area of lignin-based carbon nanofiber electrodes carbonized in 800 °C.