Volume 11 Issue 3

Cellulose is the most abundant natural polymer on earth. As the market and the public demands more and more natural products, cellulose and its derivatives are becoming increasingly more attractive. The production of dissolving pulp, which is the main feedstock for cellulose-related products, has been growing over the past decade, while the technologies for manufacturing these pulps have also been advanced. In this literature review, the production and consumption of dissolving pulp are analyzed with a focus on the Chinese market. The manufacturing processes, including raw materials, pulping methods, pulp bleaching, and post-treatments are discussed.

Currently, xylooligosaccharides (XOs), which are a kind of nutraceutical that can be produced from lignocellulosic biomass, have an important place in the global market. In this critical review the raw materials and manufacturing methods of XOs are briefly considered. The results in some publications indicate that the pre-hydrolysis liquor (PHL) from dissolving pulp process is a potential source of XOs. However, it is very difficult to separate and further remove the lignin in PHL, which is detrimental to the separation and further purification of XOs. Based on these problems, a number of important aspects with respect to PHL, including industrial treatment technologies, composition, and lignin removal technologies, are described in this review. In addition, some XOs purification technologies in PHL are also introduced.

The European Union’s Renewable Energy Directive has led many electricity producers in Europe to use wood pellets in place of fossil fuels. North America has become one of the primary suppliers of wood pellets to Europe. This paper critically examines literature, economic models and data, as well as the supply chain and country risk factors, related to wood pellet production to anticipate where North and South American pellet mills should be built to meet Europe’s demand. Canada, the United States, and Brazil maintain the largest natural forest area, planted forest area, and industrial roundwood production; however, South American countries achieve faster plantation growth rates. The World Bank’s Logistic Procurement Index and IHS’s Country Risk Index were used to score and rank countries’ investment climates, based on their supply chain and risk factors. In this regard, the United States, Canada, and Chile performed best, in contrast to Venezuela, Bolivia, and Ecuador. When considering both wood supply and investment climates, the United States, Canada, and Chile were the most attractive countries to build a pellet mill, while countries, such as Argentina, Brazil, Colombia, Paraguay, and Peru present significant trade-offs between having significant wood resources and riskier investment climates.

The pulp and paper (P&P) industry worldwide has achieved substantial progress in treating both process water and wastewater, thus limiting the discharge of pollutants to receiving waters. This review covers a variety of wastewater treatment methods, which provide P&P companies with cost-effective ways to limit the release of biological or chemical oxygen demand, toxicity, solids, color, and other indicators of pollutant load. Conventional wastewater treatment systems, often comprising primary clarification followed by activated sludge processes, have been widely implemented in the P&P industry. Higher levels of pollutant removal can be achieved by supplementary treatments, which can include anaerobic biological stages, advanced oxidation processes, bioreactors, and membrane filtration technologies. Improvements in the performance of wastewater treatment operations often can be achieved by effective measurement technologies and by strategic addition of agents including coagulants, flocculants, filter aids, and optimized fungal or bacterial cultures. In addition, P&P mills can implement upstream process changes, including dissolved-air-flotation (DAF) systems, filtration save-alls, and kidney-like operations to purify process waters, thus reducing the load of pollutants and the volume of effluent being discharged to end-of-pipe wastewater treatment plants.

Extracellular polymeric substances (EPS) are one of the main components of biofilm, prompting biofilm to form a cohesive three-dimensional framework. Numerous methods are available to help characterize the properties and the structural, chemical and physical organizations of EPS during the biofilm formation process. This review highlights key techniques from different disciplines that have been successfully applied in-situ and non-destructively to describe the complex composition and distribution of EPS in biofilm, especially microscopic, spectroscopic, and the combination of multi-disciplinary methods that can provide new insights into the complex structure/function correlations in biofilms. Among them, confocal laser scanning microscopy (CLSM) is emphasized, and its principles, applications, advantages, and limitations are summarized. Multidisciplinary techniques have been developed and recommended to study EPS during the biofilm formation process, providing more in-depth insights into the composition and spatial distributions of EPS, so as to improve our understanding of the role EPS plays in biofilms ultimately.