Volume 13 Issue 2

There has been increasing concern regarding environmental problems arising from the widespread use of petroleum-based plastic materials for packaging. Many efforts have been made to develop sustainable and biodegradable packaging materials to replace plastic products. The current review summarizes recent research progress in developing cellulose packaging materials to replace plastics used for cushioning and barrier packaging functions based on pulp fibers, cellulose nanofibers, and regenerated cellulose films to benefit from their renewability, sustainability and biodegradability. The cushioning packaging materials include molded pulp products and bio-based foams. Advanced cellulose films and paper can be good barriers for oxygen and carbon dioxide gases, as well as for water vapor. Several cellulose fiber-based packaging products have been commercialized in areas that used to be occupied solely by plastic products.

Lyocell fiber has emerged as an important class of regenerated cellulose that is produced based on the N-methyl morpholine-N-oxide (NMMO) dissolution method, and it has unique properties compared to viscose fiber. The NMMO technology provides a simple, resource-conserving, and environmentally friendly method for producing regenerated cellulose fiber. In this paper, the manufacturing process, environmental impact, and product quality of lyocell fiber are reviewed and compared with those of the conventional viscose fiber.

Hygiene tissue paper properties are a function of fiber type, chemical additives, and machine technology. This review presents a comprehensive and systematic discussion about the effects of the type of fiber and machine technology on tissue properties. Advanced technologies, such as through-air drying, produce tissue with high bulk, softness, and absorbency. Conventional technologies, where wet pressing is used to partially dewater the paper web, produces tissue with higher density, lower absorbency, and softness. Different fiber types coming from various pulping and recycling processes are used for tissue manufacturing. Softwoods are mainly used as a source of reinforcement, while hardwoods provide softness and a velvet type surface feel. Non-wood biomass may have properties similar to hardwoods and/or softwoods, depending on the species. Mechanical pulps having stiffer fibers result in bulkier papers. Chemical pulps have flexible fibers resulting in better bonding ability and softness. Virgin fibers are more flexible and produce stronger and softer tissue. Recycled fibers are stiffer with lower bonding ability, yielding products that are weaker and less soft. Mild mechanical refining is used to improve limitations found in recycled fibers and to develop properties in virgin fibers. At the same time that refining increases strength, it also decreases bulk and water absorbency.

This paper reviews ways that biomass can be converted by thermal depolymerization to make synthetic gas, i.e. syngas. Biomass, being carbon neutral, is considered as a form of solar energy stored during the growing season by photosynthesis. An effective biomass is one with low moisture and ash content, high lignin content, high calorific value, and small particle size. Woody biomass with low ash content (<1%), nut shells with high lignin content (30 to 40%), and municipal solid waste with synthetic polymers are effective at creating value-added synthetic gases. An allothermal downdraft gasifier produces a low tar syngas (99.9% tar conversion) at 850 oC and provides a simple and low-cost process. Integrated gasification combined cycle (IGCC) improves thermodynamic efficiency. To avoid thermal loss, a hot gas filtration system uses trona sorption material for sulfur and halogen compounds. Secondary systems can use multiple cyclones followed by reactors employing calcined dolomite, olivine, and others for adsorption or reaction with residual sulfur, ammonia, metals, and halogens. Reforming of residual tar to syngas can take place within chambers with ceramic tubes doped with nano-nickel particles. Syngas can then be used in boilers, gas turbines for production of electricity or production of chemicals by Fischer-Tropsch conversion.

The production of wood-based polymer composites has gained increasing interest in recent years, especially regarding sustainability issues, aiming at the recovery, reuse, and up-cycling of by-products from natural resources exploitation, as well as plastics. Due to their reduced cost, low density, and availability, wood components (fibers, flour) are attractive fillers for thermoplastic polymer matrices used in multi-component systems. Performance of wood-based thermoplastic materials mainly depends on the type and strength of interactions at the polymer-wood interface. Different low polarity polymers (high/low density polyethylene, polypropylene, polyvinylchloride) can be successfully used as matrices in such formulations. Various methods may be applied in order to obtain specified performance attributes of wood-based composites. Addition of appropriate compatibilizing agents, chemical and/or physical modification of the filler in order to improve its compatibility towards the matrix, or a judicious combination of these approaches may be employed. This paper briefly reviews some recent literature data, as well as research results by the authors, aiming at a comparative assessment of the materials properties (structure, thermal, mechanical and water sorption behavior) in correlation with the nature and type of components, processing, recycling options, and environmental impact.