Volume 14 Issue 2

Poplar (Populus tomentosa Carr.) solid wood was surface densified in the tangential direction, and the vertical density profile (VDP) and hardness of the treated and untreated samples were measured. The effects of the process parameters on the VDP and hardness were investigated. To explicitly describe the VDP of the surface densified wood, five indices (AD, ADx, PD, PDi, and DTh) were used. The compressing temperature and closing speed influenced the formation and shape of the VDP. A higher temperature yielded a greater PD and Pdi, and a faster closing speed yielded a higher PD, but smaller PDi and DTh. Increasing the compression ratio increased the AD, ADx, and maximum load, and the poplar wood was compressed in the overall thickness as the compression ratio exceeded a certain degree. The Janka hardness of the poplar wood was significantly improved after surface densification; a higher temperature resulting in a higher surface hardness was explained by the higher PD. The closing speed and compression ratio affected the hardness by impacting the VDP, specifically the PD and DTh indices. When the PD and DTh were greater the surface hardness was greater. By this study, a compressing temperature of 140 to 160 °C and the closing speed of 10 mm/min is recommended, and to prevent the deformation of unheated side of the wood samples and obtain a higher surface hardness, the compression ratio is restricted to 20%.

Increasing the profitability of lignin side-streams is a challenge in the scientific community. Lignin residue originates from black liquor and lignin cake, which are residues from pulp and bio-ethanol production. This paper presents a life cycle assessment study to investigate how pulp and bio-ethanol processes vary in their environmental performance when a fraction of lignin is removed and to identify the best alternative energy source. Fossil energy, natural gas, and cogeneration were evaluated as heat and power alternative sources. The results showed that lignin removal does not considerably affect the environmental performance of the baseline systems and does not generate a relevant risk of “burdens shifting.” Natural gas was the best alternative of power source in a bio-ethanol system, whereas cogeneration showed better compatibility with pulp mills. For the analyzed systems, the necessary allocation distributed the impact contributions between the main products (bio-ethanol/pulp) and the co-products (lignin-cake/black liquor), counterbalancing the impact increase due to the introduction of the new heat, electricity supply, and additional treatment aimed at lignin extraction. Finally, sensitivity analyses confirmed the low influence on the results of the substitution ratio.

The process of removing chromium(III) ions from aqueous solutions was investigated with respect to a phosphorus-containing product containing inositol hexaphosphoric acid derivatives obtained from rice bran-rice waste products of Far Eastern breeding varieties. The removal efficiency of chromium(III) ions by phosphorus-containing product depended on their initial concentration and reached 82%. Thus, environmentally friendly polyfunctional chelate materials from rice production wastes could be used to remove metal ions from aqueous solutions.

Preservation of wood structures against degradation represents an old, and however, a new challenge. Wood, as a natural hybrid composite material, represents a versatile and widely exploited renewable resource for indoor and outdoor applications. Its constitutive biopolymers are subjected to intense and progressive oxidative degradation processes under environmental conditions of exposure, affecting wood’s native durability and generating significant structural and color changes, along with progressive diminution of its resistance against biological agents. One effective way to prevent wood degradation is to apply coating protective layers by chemical modification of the surface. In this context, increasing interest for improving wood coatings behavior under exposure to outdoor applications, when these are able to prevent or limit to a large extent the deleterious effects of environmental factors upon their performance, justifies enhanced research efforts to provide new effective solutions for sustainable wood protection. Recent trends in this area include use of bio-based natural products – extractives, oils, waxes, resins, biopolymers, biological control agents – for which the main classification criterion is represented by the type of protection provided, considering the large available variety of such formulations. The present paper focuses on the most recent literature data with significant assessment of specific topics related to these issues.

Barrier materials have an important role in various packaging applications, especially considering the requirements associated with protection and shelf life. Most barrier materials used in today’s industry are either manufactured from oil resources or metals. Driven by the increase in environmental awareness, access to oil resources as well as legislation, new and environmentally benign alternatives are at the center stage of scientific and industrial interest. This article covers the use of wood-derived polymers and those produced from microorganisms, which display remarkable barrier properties. Wood-based products have received great attention for their air/oxygen resistance. As far as their properties, microorganism-derived biopolymers are comparable to conventional oil-based thermoplastics, but their cost may still be an issue. Both, wood and microorganism-derived biopolymers are challenged when moisture, grease and oxygen resistance are simultaneously required. Hence, multilayer structures and composites are needed to fulfill the most demanding requirements of packaging materials. Here we offer a review of these topics together with a discussion of their prospects.

Many types of lignocellulosic biomass show effective binding of toxic heavy metals from industrial and environmental effluents. Biosorption is an emerging option for conventional methods to remove heavy metals, some of them with even better efficiencies compared to conventional methods. Raw material for biosorption is typically low-cost and easily available, including agricultural waste or forest residues such as sawdust, bark, or needles. This review concentrates on the accumulation of heavy metals by lignocellulosic biosorbents. Thus far, biosorption has not been economically feasible on a large scale and needs further development for profitability. Industrial-scale wood-based biosorbent applications are especially still lacking. Moreover, due to legislative demands, there is an increasing need for accurate and reliable analytical methods for metal analysis of environmental and industrial effluents. In the future, biosorption processes are likely to become common, and the requirement for environmental monitoring will increase due to ever restricting regulations. This emphasizes not only the need for the development of feasible process solutions, but also a requirement for accurate analytical methods.

Global energy consumption is expected to grow by 56% between 2010 and 2040. Renewable energy is one of the fastest-growing energy resources, and biomass is a major feedstock for providing renewable energy. It constitutes up to 35% of the main energy consumption in developing countries. Densified solid biofuel with high density gets a lot of attention due to its uniform shape and low heating cost. When considering densified solid biofuels as a viable solution for energy production, its quality needs to be improved. Solid biofuel quality is a function of the chemical composition and physical properties of the raw materials. It is widely reported that the raw material chemical composition has a major effect on the final solid biofuel quality, as it influences the heating value, ash content, and mechanical durability. The moisture content influences the net heating value, combustion efficiency, and mechanical durability of solid biofuels. The bulk density influences the mechanical durability, thermal characteristics, as well as handling and storage costs of solid biofuels. This work reviewed the latest developments on the effects of the chemical composition, moisture content, and bulk density of raw materials on the thermal efficiency, emission, and mechanical durability of densified solid biofuels.