Research on nanocellulose has significantly increased over the past few decades, owing to the various attractive characteristics of this material, such as renewability, widespread availability, low density, excellent mechanical properties, economic value, biocompatibility, and biodegradability. Nanocellulose categorized into two main types, namely cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). In this review, we present the recent advances made in the production of CNFs and CNCs. In addition to the conventional mechanical and chemical treatments used to prepare CNFs and CNCs, respectively, other promising techniques as well as pretreatment processes have been also proposed in recent times, in an effort to design an economically efficient and eco-friendly production route for nanocellulose. Further, while the hydrophilic nature of nanocellulose limits its use in polymeric matrices and in some industrial applications, the large number of hydroxyl groups on the surface of nanocellulose provides a suitable platform for various kinds of modification treatments. The various chemical and physical surface treatment procedures reported for nanocellulose have been reviewed in this paper. Finally, in this review, we summarize the life cycle assessment studies conducted so far on nanocellulose, which quantify the environmental impact of nanocellulose products. The current paper is a comprehensive review of the recent literature on nanostructured cellulose.

Advances in cellulose nanomaterials

Rechargeable Li-ion battery applications in consumer products are fastly growing, resulting in increasing resources demand: it is for example estimated that battery applications account for nearly 25% of the worldwide cobalt demand in 2007. It is obvious that recycling of batteries may help saving natural resources. However, it is not straightforward to quantify to what extent rechargeable battery recycling saves natural resources, given their complex composition, and the complex international production chain. In this paper, a detailed analysis of a lithium mixed metal oxide battery recycling scenario, where cobalt and nickel are recovered and re-introduced into the battery production chain, is compared with a virgin production scenario. Based on detailed data acquisition from processes spread worldwide, a resource saving analysis is made. The savings are quantified in terms of exergy and cumulative exergy extracted from the natural environment. It turns out that the recycling scenario result in a 51.3% natural resource savings, not only because of decreased mineral ore dependency but also because of reduced fossil resource (45.3% reduction) and nuclear energy demand (57.2%).

Recycling rechargeable lithium ion batteries: Critical analysis of natural resource savings

Metal–organic frameworks meet scalable and sustainable synthesis

Although the processing of coal is an ancient problem and has been practiced for centuries, the constraints posed on today's coal conversion processes are unprecedented, and utmost innovations are required for finding the solution to the problem.With a strong demand for an affordable energy supply which is compounded by the urgent need for a CO2 emission control, the clean and efficient utilization of coal presents both a challenge and an opportunity to the current global R&D efforts in this area. This paper provides a historical perspective on the utilization of coal as an energy source as well as describing the progress and challenges and the future prospect of clean coal conversion processes. It provides background on the historical utilization of coal as an energy source, along with particular emphasis on the constraints in current coal conversion technologies. It addresses the energy conversion efficiencies for current coal combustion and gasification processes and for the membrane and looping based novel processes which are currently under development at various stages of testing. The control technologies for pollutants including CO2 in flue gas or syngas are also discussed. The coal conversion process efficiencies under a CO2 constrained environment are illustrated based on data and ASPEN Plus® simulations. The challenges for future R&D efforts in novel coal conversion process development are also presented.

Clean coal conversion processes – progress and challenges

Modelling pollution-generating technologies in performance benchmarking: Recent developments, limits and future prospects in the nonparametric framework

New technologies, either renewables-based or not, are confronted with both economic and technical constraints. Their development takes advantage of considering the basic laws of economics and thermodynamics. With respect to the latter, the exergy concept pops up. Although its fundamentals, that is, the Second Law of Thermodynamics, were already established in the 1800s, it is only in the last years that the exergy concept has gained a more widespread interest in process analysis, typically employed to identify inefficiencies. However, exergy analysis today is implemented far beyond technical analysis; it is also employed in environmental, (thermo)economic, and even sustainability analysis of industrial systems. Because natural ecosystems are also subjected to the basic laws of thermodynamics, it is another subject of exergy analysis. After an introduction on the concept itself, this review focuses on the potential and limitations of the exergy concept in (1) ecosystem analysis, utilized to describe maximu...

Exergy: Its Potential and Limitations in Environmental Science and Technology

Summary
Life cycle impact of emissions, energy requirements, and exergetic losses are calculated for a novel process for producing titanium dioxide nanoparticles from an ilmenite feedstock. The Altairnano hydrochloride process analyzed is tailored for the production of nanoscale particles, unlike established commercial processes. The life cycle energy requirements for the production of these particles is compared with that of traditional building materials on a per unit mass basis. The environmental impact assessment and energy analysis results both emphasize the use of nonrenewable fossil fuels in the upstream life cycle. Exergy analysis shows fuel losses to be secondary to material losses, particularly in the mining of ilmenite ore. These analyses are based on the same inventory data. The main contributions of this work are to provide life cycle inventory of a nanomanufacturing process and reveal potential insights from exergy analysis that are not available from other methods.

Life Cycle of Titanium Dioxide Nanoparticle Production

Although many regard it as the most important step of life cycle assessment, improvement analysis is given relatively little attention in the literature. Most available improvement approaches are h...

Appreciating the Role of Thermodynamics in LCA Improvement Analysis via an Application to Titanium Dioxide Nanoparticles

Towards sustainability of engineered processes: Designing self-reliant networks of technological–ecological systems

The methods of energy, exergy, and life cycle analysis are applied to a new nano-manufacturing process producing 40 nm titanium dioxide particles. The use of identical boundaries for each analysis allows for direct comparison of the results from each method. It was found that the thermodynamic methods identify spray hydrolysis as a significant sink in the process and life cycle analysis shows it to be the largest source of greenhouse gas emissions. Despite this agreement, there are some discrepancies between methods, and exergy analysis appears to give additional information that energy analysis overlooks. Of course the optimal method for a given application depends on the intended goals of the analysis.

Geoffrey F. Grubb

Papers

Exergy: Its Potential and Limitations in Environmental Science and Technology

Life Cycle of Titanium Dioxide Nanoparticle Production

Appreciating the Role of Thermodynamics in LCA Improvement Analysis via an Application to Titanium Dioxide Nanoparticles

Towards sustainability of engineered processes: Designing self-reliant networks of technological–ecological systems

Energetic and environmental evaluation of titanium dioxide nanoparticles