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Biogas is acknowledged as one of the foremost bioenergy to address the current environmental and energy challenges being faced by the world. Commonly, biogas is used for applications like cooking, lighting, heat and power production. To widen the scope of biogas application, like transportation, natural gas grid injection and substrate for the production of chemicals and fuel cells, mainly CO 2 , H 2 S and other impurities need to be removed by various upgrading technologies. It is an important process to produce biomethane with above 90% methane. There are various physico-chemical (adsorption, absorption, cryogenic and membrane separations) and biological (in situ and ex situ) processes for biogas upgradation, and each process is site and case specific. The aim of the present paper is to thoroughly evaluate the existing and emerging biogas upgrading technologies. Analysis of each technology with respect to basis of operations, energy requirement, methane purity and recovery and cost economics has been carried out. A thorough analysis has been done on the major hurdles and the research gaps in this sector. For a wider and successful implementation of the biogas upgradation technology, the trends in research and development (R&D) such as development of efficient biogas upgrading technologies, adsorbents, reduction in cost and methane loss have been thoroughly evaluated.

Advancements in chemical, medical, cosmetic, and plastic producing industries have improved agricultural yields, health and human life in general. As a negative consequence, a plethora of chemicals are intentionally and unintentionally released to terrestrial and aquatic environments with sometimes devastating effects for entire ecosystems. One mitigation strategy to counteract this pollution is bioremediation. Bioremediation is an umbrella term for biologically mediated processes during which an undesired compound is transformed, degraded, sequestered and/or entirely removed from the ecosystem. Organisms across all domains of life may mediate bioremediation; yet, fungi are particularly promising candidates. They possess metabolic capabilities to break down complex molecules which make fungi the ultimate degraders of recalcitrant organic matter in nature. Bioremediation by fungi, also termed mycoremediation, has been more frequently investigated in terrestrial than aquatic ecosystems, although fungi also thrive in lacustrine and marine environments. Here, we focus on mycoremediation of emerging pollutants in aquatic environments. In this context, we draw parallels between terrestrial and aquatic fungal taxa, and their role in mycoremediation. We discuss the ability of fungi to break-down (i) pesticides, (ii) pharmaceuticals and personal care products, (iii) plastics, both conventional types and (iv) bioplastics, and fungal role, (v) mitigation of heavy metal pollution. Furthermore, we (vi) discuss possible mycoremediation strategies in applied settings and highlight novel enzyme based mycoremediation strategies.

Lignocellulosic biomass is the most abundant renewable energy resource on earth that can be utilized for biofuel production. However, its utilization in biofuel production is limited due to its complex structure and recalcitrant nature. The anaerobic biomass degradation can be improved by recruiting suitable microbes with efficient enzyme system and utilizing termite gut microorganisms represents a prospective way to do so. This review provides an overview of termites and their types along with their associated symbionts, their distribution and enzyme production throughout the gut segments for efficient lignocellulosic biomass degradation. Furthermore, application of omics to elucidate the role and relationship of individual host termite, isolated symbiont, host-microbes interaction and microbe-microbe interaction, their physiology, and biochemistry has been thoroughly discussed. In addition, the potential of termite gut microbiota and future perspective for biomethanation of lignocellulosic biomass has been highlighted. With the further advancement in omics technology, a lot more information will be unfolded and further improve our understanding of one of the most efficient natural lignocellulosic biomass utilization systems. Improved understanding of termite and its associated symbionts can result in important technological breakthroughs that will further establish the potential of termite gut microbiota for biomethanation of lignocellulosic biomass.Graphic abstract

Pines play a significant role in forest biodiversity globally and generate huge forest litter. Dry pine needles due to low ignition temperature and high frictional force with the ground catch fire quickly. Annual forest fires in the northern states of India greatly impact the Indian economy besides causing huge loss to biodiversity, livelihood, and environment. Pine needles are also considered unfit for fodder consumption due to presence of tannins. Although the presence of softwood lignin in pine needles makes it difficult to degrade easily, the presence of holocellulose (68.5%) containing 45–51% cellulose makes this biomass a potential substrate to be used in pulp-making industries for low-grade paper sheets. The good fiber length of pine needles (1.3–1.4 mm) with a diameter of 30–32 μm, maybe considered important property for paper making. The use of pine needles in the pharmaceutical and food industries are due to the presence of secondary metabolites (α-pinene, β-pinene, caryophyllene etc.). The various other potential applications of pine needles are for producing bio-ethanol (yield, 3.98%; purity, 94%), biogas (yield, 23.1 L kg −1 ), smokeless briquettes (calorific value, 18.77 MJ kg −1 ), biochar (calorific value, 25.6 MJ kg −1 ), bio-composites (tensile strength, 21–60 MPa), and bio-pesticides. This paper comprehensively reviews the current applications of pine needles along with its future prospective applications that can have the dual advantage of providing employment opportunities to the people along with environmental protection.

In the present study, landfill leachate of three landfill sites of Delhi, India, was toxico-chemically analyzed for human risk assessment. Raw leachate samples were collected from the municipal solid waste (MSW) landfills of Delhi lacking liner systems. Samples were characterized with relatively low concentrations of heavy metals while the organic component exceeded the upper permissible limit by up to 158 times. Qualitative analysis showed the presence of numerous xenobiotics belonging to the group of halogenated aliphatic and aromatic compounds, polycyclic aromatic hydrocarbons (PAHs), phthalate esters, and other emerging contaminants. Quantitative analysis of PAHs showed that the benzo(a)pyrene-toxic equivalence quotient (BaP-TEQ) ranged from 41.22 to 285.557 ng L −1 . The human risk assessment methodology employed to evaluate the potential adverse effects of PAHs showed that the cancer risk level was lower than the designated acceptable risk of 10 −6 . However, significant cytotoxic and genotoxic effects of leachates on HepG2 cell line was observed with MTT EC 50 value ranging from 11.58 to 20.44 % and statistically significant DNA damage. Thus, although the leachates contained low concentrations of PAHs with proven carcinogenic potential, but the mixture of contaminants present in leachates are toxic enough to cause synergistic or additive cytotoxicity and genotoxicity and affect human health.

Biomimicking ruminant digestion strategies (RDSs) into anaerobic digestion (AD) enables efficient bioconversion of lignocellulosic biomass. Understanding RDSs is essential to translate their features into designing and developing bioprocesses and bioreactors. Here, we discuss insights into recently developed bioinspired bioprocesses, bioreactors, and future AD systems based on RDSs.

The bark extract of Mimusops elengi is rich in different types of plant secondary metabolites such as flavonoids, tannins, triterpenoids and saponins. The present study shows the usefulness of the bark extract of Mimusops elengi for the green synthesis of gold nanoparticles in water at room temperature under very mild conditions. The synthesis of the gold nanoparticles was complete within a few minutes without any extra stabilizing or capping agents and the polyphenols present in the bark extract acted as both reducing as well as stabilizing agents. The synthesized colloidal gold nanoparticles were characterized by HRTEM, surface plasmon resonance spectroscopy and X-ray diffraction studies. The synthesized gold nanoparticles have been used as an efficient catalyst for the reduction of 3-nitrophenol and 4-nitrophenol to their corresponding aminophenols in water at room temperature.

Purpose of Review Annually, huge amounts of microplastics (MPs) are added to farmlands through sewage sludge (SS)/biosolid applications as a fertilizer. Most research emphasizes the enormity of the problem and demonstrates the fate, impacts, and toxicity of MPs during SS treatment processes and land applications. None has addressed the management strategies. To address the gaps, the current review evaluates the performance analysis of conventional and advanced sludge treatment methods in eliminating MPs from sludge. Recent Findings The review uncovers that the occurrence and characteristics of MPs in SS are highly governed by factors such as population density, speed and level of urbanization, citizens’ daily habits, and treatment units in wastewater treatment plants (WWTPs). Furthermore, conventional sludge treatment processes are ineffective in eliminating MPs from SS and are accountable for the increased small-sized MPs or micro(nano)plastics (MNPs) along with altered surface morphology facilitating more co-contaminant adsorption. Simultaneously, MPs can influence the operation of these treatment processes depending on their size, type, shape, and concentration. The review reveals that research to develop advanced technology to remove MPs efficiently from SS is still at a nascent stage. Summary This review provides a comprehensive analysis of MPs in the SS, by corroborating state-of-the-knowledge, on different aspects, including the global occurrence of MPs in WWTP sludge, impacts of different conventional sludge treatment processes on MPs and vice versa, and efficiency of advanced sludge treatment and upcycling technologies to eliminate MPs, which will facilitate the development of mitigation measures from the systematic and holistic level. Graphical Abstract

Antimony (Sb) has been classified as a high-priority contaminant in the environment. Sb contamination resulting from the use of antimony-containing compounds in industry necessitates the development of efficient methods to remove it from water and wastewater. Adsorption is a highly efficient and reliable method for pollutants removal owing to its availability, recyclability, and low cost. Recently, carbonaceous materials and their applications for the removal of Sb from the aqueous matrices have received special attention worldwide. Herein, this review systematically summarizes the occurrence and exposure of Sb in the environment and on human health, respectively. Different carbon-based adsorbents have been classified for the adsorptive removal of Sb and their adsorption characteristics have been delineated. Recent development in the adsorption performance of the adsorbent materials for improving the Sb removal from the aqueous medium has been outlined. Further, to develop an understanding of the effect of different parameters like pH, competitive ions, and dissolved ions for Sb adsorption and subsequent removal have been discussed. A retrospective analysis of literature was conducted to present the adsorption behavior and underlying mechanisms involved in the removal of Sb using various adsorbents. Moreover, this study has identified emerging research gaps and emphasized the need for developing modified/engineered carbonaceous adsorbents to enhance Sb adsorption from various aqueous matrices.

The textile industry is a growing sector worldwide and has immense opportunity in terms of providing employment and boosting a nation’s economy. However, there exist severe environmental risks associated with textile effluents that impact the surrounding ecosystem. This review offers an approach for sustainable water management using phycoremediation to treat dye-laden wastewater and recover bio-based pigments from the residual biomass. Microalgae such as Chlorella, Scenedesmus, Phormidium, and macroalgae like Sargassum, Enteromorpha, and Codium has been extensively used in several phycoremediation-based studies, and their residual biomass could be a potent source for extraction of bio-based pigments. This review also recommends studies involving the algal-bacterial consortia approach for treating dye-laden wastewater as an alternative to conventional, biobased methods. The outcome of this study will provide policymakers and researchers with new insight to manage water and wastewater resources sustainably. Furthermore, this review also enhances our understanding of nature-based decontamination approaches for treating dye-laden wastewater through algal-based technologies.