Review Articles

This article reviews publications with the goal of understanding the role of hydrophobic copolymers added to size-press starch as a means to make paper products more resistant to penetration by aqueous fluids. The underlying technology is considered, including background related to starch, size-press equipment, and various hydrophobic copolymers and latex products that have been evaluated. The resulting hydrophobization of the paper has been reported to depend not only on the dosage of the hydrophobic additive, but also on its molecular mass and ionic form. The mechanism appears to rely on an ability of starch to serve as a temporary host for hydrophobic compounds in aqueous solution. It has been proposed that hydrophobic copolymers added with size press starch tend to migrate to the air interface during drying of the starch film, thus allowing the low-energy functional groups, such as styrene or alkyl chains, to face outwards. Further research is needed to address various mechanistic questions. There may be opportunities to further raise the performance of this type of technology as practiced within paper production factories.

Global municipal solid waste (MSW) generation will increase to 2.2 billion tons per year by 2025 as per the World Bank projection. Improper waste management often leads to environmental degradation (i.e. water, air and soil pollution), transmission of diseases, and the release of greenhouse gases emissions, which contributes to climate change. To combat these problems, several countries are following the waste to energy (WtE) approach, which significantly reduces the volume of waste and generates renewable energy. Thus, the present study focuses on the municipal solid waste generation, composition, and waste to energy conversion technologies. Thermal conversion processes including incineration, pyrolysis, and gasification for heat, bio-oil, and syngas generation are already well established and are being employed in several countries. Currently, researchers are trying to improve the efficiency of biochemical methods such as anaerobic digestion, microbial fermentation, and microbial fuel cells for biogas, biohydrogen, and bioelectricity generation from MSW. This review explains the recent focus on microbial fermentation and microbial fuel cells for biofuels and bioelectricity production. Development of these technologies can lead to suitable eco-friendly approaches for the future. WtE technologies are important components of circular economy that will assist to achieve the demand of clean energy in future.

Cellulose is among the most promising renewable and biodegradable materials that can help meet the challenge of replacing synthetic fibers currently used in disposable N95 respirators and medical face masks. Cellulose also offers key functionalities that can be valued in filtration applications using approaches such as nanofiltration, membrane technologies, and composite structures, either through the use of nanocellulose or the design of functional composite filters. This paper presents a review of the structures and compositions of N95 respirators and medical face masks, their properties, and regulatory standards. It also reviews the use of cellulose and nanocellulose materials for mask manufacturing, along with other (nano)materials and composites that can add antimicrobial functionality to the material. A discussion of the most recent technologies providing antimicrobial properties to protective masks (by the introduction of natural bioactive compounds, metal-containing materials, metal-organic frameworks, inorganic salts, synthetic polymers, and carbon-based 2D nanomaterials) is presented. This review demonstrates that cellulose can be a solution for producing biodegradable masks from local resources in response to the high demand due to the COVID-19 pandemic and for producing antimicrobial filters to provide greater protection to the wearer and the environment, reducing cross-contamination risks during use and handling, and environmental concerns regarding disposal after use.

Biodegradable textiles made from cellulose, the most abundant biopolymer, have gained attention from researchers, due to the ease with which cellulose can be chemically modified to introduce multifunctional groups, and because of its renewable and biodegradable nature. One of the most attractive features required for civilian and military applications of textiles is flame-retardancy. This review focuses on various methods employed for the fabrication of cellulose-based flame-retardant cotton textiles along with their developed flame-retardant properties over the last few years. The most common method is to merge N, S, P, and Si-based polymeric, non-polymeric, polymeric/non-polymeric hybrids, inorganic, and organic/inorganic hybrids with cellulose to fabricate flame-retardant cotton textiles. In these studies, cellulose was chemically bonded with the flame-retardants or in some cases, cotton textiles were coated by flame-retardants. The flame-retardant properties of the cotton textiles were investigated and determined by various methods, including the limiting oxygen index (LOI), the vertical flame test, thermal gravimetric analysis (TGA), and by cone calorimetry. This review demonstrates the potential of cellulose-based flame-retardant textiles for various applications.

Despite the extraordinary properties of nanocellulose (NC), as confirmed through two decades of exhaustive research, addressing an array of potential applications, the NC market is still far from reaching its full potential. Among the main causes is the lack of process-adapted measuring tools capable of characterizing NC, at acceptable speed and reliability, to meet the industrial demands in a cost-effective way. Therefore, reliable characterization methodologies of NC and new standards are of paramount importance in ensuring reproducible research results and quality control specifications for present and future NC products and applications. Furthermore, the successful industrial use of NC products depends on critical parameters that are still being identified and studied. This review paper aims to identify some of the current drawbacks and limitations in NC characterization that hinder their commercial deployment. Moreover, important challenges related to characterization and new opportunities for future research in this field are addressed.

Bio-based ethylene produced by bioethanol dehydration is an environmentally friendly substitute for oil-based ethylene. It is a low-pollution raw material that can be used to produce high-value bio-based materials. Currently, some industrial plants use first-generation (1G) bioethanol to produce bio-ethylene. However, second-generation (2G) bioethanol is not currently used to produce bio-ethylene because the manufacturing processes are not optimized. The conversion of lignocellulosic biomass to bio-ethylene involves pretreatment, enzymatic hydrolysis of carbohydrates, the fermentation of sugars to ethanol, ethanol recovery by distillation, and ethanol dehydration to ethylene. This work presents a review of second-generation (2G) bio-ethylene production, analyzing the stages of the process, possible derivatives, uses, and applications. This review also contains technical, economic, and environmental considerations in the possible installation of a biorefinery in the northeast region of Argentina (NEA).

Native cellulose is mainly found in phytomass, such as trees and other plants. It has a regular hierarchical nanoarchitecture, in which the extended macromolecular chains are aligned and closely packed in parallel to form the crystalline nanofibrils of cell walls. In the context of material utilization, nanocellulose is a collective term for nano-ordered assemblies of cellulose chains. In recent times, it has been produced in large quantities from woody bioresources. In addition, nanocellulose has some fascinating physicochemical properties, such as high strength, light weight, transparency, birefringence, and low thermal expansion. These properties have enabled broad functional design of nanocellulose-based materials; but most of them are facing serious competition from various products that already exist. However, nanocellulose is not just a green alternative to existing materials. Rather, it is expected to make a profound difference in terms of pioneering novel functions. The present review focuses on the unexpected features of nanocellulose materials, triggered by details of the inherent nanoarchitecture of native cellulose.

The agricultural industry is one of the main economic contributors in developing countries, especially in tropical regions. Extensive land clearing has led to severe erosion within the watersheds, which increases the vulnerability of water catchments to natural disasters, such as floods. Cellulosic fibers, such as jute, sisal, kenaf, hemp, and coir, are gaining increasing worldwide attention for their potential application in controlling soil erosion, principally due to their remarkable biodegradable and physical properties. Nonetheless, the research on biocomposites in controlling soil erosion is limited compared to the natural fibers. This is perhaps due to poor availability and high cost of biodegradable polymers compared to natural fibers, which are abundant and inexpensive. Poor adhesive interactions between the matrix and natural fibers due to the hydrophilic characteristic of the fibers is another major drawback that limits the development of biocomposites for controlling soil erosion.

Due to the combined pressures of energy shortage and environmental degradation, bio-liquid fuels have been widely studied as a green, environmentally friendly, renewable petroleum alternative. This article summarizes the various technologies of three generations of biomass feedstocks (especially the second-generation, biomass lignin, and the third-generation, algae raw materials) used to convert liquid fuels (bioethanol, biodiesel, and bio-jet fuel) and analyzes their advantages and disadvantages. In addition, this article details the latest research progress in biomass liquid fuel production, summarizes the list of raw materials, products and conversion processes, and provides personal opinions on its future development. The aim is to provide a theoretical basis and reference for the optimization of existing technology and future research and development of biomass liquid fuels.

Barrier films that are used on packages play an important role, especially in the protection of food products. Research is being carried out at an accelerating pace to replace petroleum-based plastic films, which do not biodegrade and are difficult to recycle. This review article considers publications related to the use of polyelectrolyte complexes (PECs) in barrier films as a strategy to decrease the permeation of oxygen and other substances into and out from packages. Research progress has been achieved in using combinations of positively and negatively charged polymers, sometimes together with platy mineral particles, as a way to restrict diffusion through packaging materials. In principle, the ionic bonds within PECs contribute to a relatively high cohesive energy density within such a barrier film, which can resist diffusion of various gases and greasy substances. Resistance to water vapor, as well as aqueous substances, represent important challenges for barrier concepts that depend on ionic bond contributions. Factors affecting barrier performance of PEC-based films are discussed in light of research findings.