Sustainable management of tea wastes: resource recovery and conversion techniques

As the demand for tea (Camellia sinensis) has grown across the world, the amount of biomass waste that has been produced during the harvesting process has also increased. Tea consumption was estimated at about 6.3 million tonnes in 2020 and is anticipated to reach 7.4 million tonnes by 2025. The generation of tea waste (TW) after use has also increased concurrently with rising tea consumption. TW includes clipped stems, wasted tea leaves, and buds. Many TW-derived products have proven benefits in various applications, including energy generation, energy storage, wastewater treatment, and pharmaceuticals. TW is widely used in environmental and energy-related applications. Energy recovery from low- and medium-calorific value fuels may be accomplished in a highly efficient manner using pyrolysis, anaerobic digestion, and gasification. TW-made biochar and activated carbon are also promising adsorbents for use in environmental applications. Another area where TW shows promise is in the synthesis of phytochemicals. This review offers an overview of the conversion procedures for TW into value-added products. Further, the improvements in their applications for energy generation, energy storage, removal of different contaminants, and extraction of phytochemicals have been reviewed. A comprehensive assessment of the sustainable use of TWs as environmentally acceptable renewable resources is compiled in this review.

Microwave-assisted quick synthesis of microcrystalline cellulose from black tea waste (Camellia sinensis) and characterization

Tea wastes generated in the industries during tea production processes show excellent potential to be used as a renewable, abundant, and cheap source for the extraction of microcrystalline cellulose. In the current work, MCC was isolated from black tea waste through microwave heating instead of using conventional heating and avoiding the traditional acid hydrolysis method. Microwave increased the reaction speed significantly and resulted in very quick delignification and bleaching of black tea waste to isolate MCC in white powdered form. FTIR, XRD, FESEM, and TGA analysis were then carried out to investigate the chemical functionality, crystallinity, morphology, and thermal properties, respectively, of the synthesized tea waste MCC. The characterization results demonstrated that cellulose with a short rough fibrous structure having an average particle size of around 23 μm was extracted. The results of FTIR and XRD demonstrated unequivocally that all amorphous non-cellulosic compounds had been eliminated. The microwave-extracted black tea waste MCC showed 89.77 % crystallinity and good thermal properties, indicating that it could be a promising filler material for preparing polymer composites. Therefore, microwave-assisted delignification and bleaching can be used as a suitable, energy-efficient, time-saving and low-cost method for extracting MCC from the black tea waste produced in tea factories.

A review on global perspectives of sustainable development in bioenergy generation

Over the last few decades, the globe has much relied on fossil fuels; however, environmental concerns forced the World to look at biofuel as an alternative for stable economic development. Biofuel also facilitates national energy security maintenance and reduces environmental complications. The present study is focused on an in-depth analysis of bioenergy policy measures undertaken by various federal agencies of different countries in order to shed light on the bottlenecks that impede biofuel's growth as a sustainable and alternative fuel. An in-depth assessment of feedstock utilization, blending targets, and policy assistance schemes have been thoroughly reviewed. In addition, the potential of commercial firms for the production of bioenergy is highlighted in order to grasp the current bioenergy market scenario better. Finally, the article is concluded with the viewpoints of the authors to address the standing issues of global bioenergy generation.

Technological advancement in the synthesis and applications of lignin-based nanoparticles derived from agro-industrial waste residues: A review

Over the years, lignin has drawn a great deal of interest for their potential use as bio-polymers due to the presence of high amount of phenolic compounds, non-polluting feature and cost-competitiveness as compared to synthetic polymers. However, in order to fast-track their development, different attempts are made towards the usage of lignin in nano form since it exhibits some unique properties in nanoscale range. The present review article provides a detail analysis on the recent advancement in the synthesis and applications of lignin nanoparticles (LNPs) derived from agro-industrial waste residues. In view of that, an in-depth morphological analysis was reviewed to assess the structural influence on the characteristics of LNPs. Further, application of LNPs is explored in different fields including bio-medical engineering, pharmaceuticals, skin-care products and food industries. Finally, the paper is concluded discussing various challenges associated with the synthesis, modification and development with an aspiration of futuristic developments. The readers of this review article will be highly benefitted after acquiring a comprehensive knowledge on LNPs and its different synthesis processes along with various applications.

MOFs for the treatment of arsenic, fluoride and iron contaminated drinking water: A review

Over the last few decades, the global pollution of surface and groundwater poses a serious threat not only to human beings but also towards aquatic lives due to the presence of emerging contaminants. Among the others, the presence of arsenic, fluoride, and iron are considered as the most common toxic pollutants in water bodies. The emergence of metal organic frameworks (MOFs) with high porosity and surface area is represented as significant inclusion into the era of entrapping contaminants present in drinking water. In the present review article, an in-depth insight is provided on the recent developments in the removal of arsenic, fluoride, and iron from drinking water using MOFs. Various aspects related to the synthesis, latest technologies adopted for the modifications in the synthesis process and advanced applications of MOFs for the removal of such contaminants are explicitly discussed. A detailed insight was provided to understand the mechanism of various interactions of MOFs with arsenic and fluoride. With respect to arsenic, fluoride, and iron removal the ultrastructural morphology of MOFs is assessed based on different molecular arrangements. Further, commercial aspects of various MOFs are presented in order to highlight the process feasibility. Finally, various perspectives and challenges involved in process scale up are comprehensively narrated with an aspiration of futuristic developments. The paper will be beneficial to the readers for acquiring a piece of in-depth knowledge on MOFs and its various synthesis approaches along with remarkable achievements for the removal of arsenic, fluoride, and iron from contaminated drinking water.