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To meet the CO 2 emission reduction targets, carbon dioxide capture and utilization (CCU) comes as an evolve technology. CCU concept is turning into a feedstock and technologies have been developed for transformation of CO 2 into useful organic products. At industrial scale, utilization of CO 2 as raw material is not much significant as compare to its abundance. Mechanisms in nature have evolved for carbon concentration, fixation and utilization. Assimilation and subsequent conversion of CO 2 into complex molecules are performed by the photosynthetic and chemolithotrophic organisms. In the last three decades, substantial research is carry out to discover chemical and biological conversion of CO 2 in various synthetic and biological materials, such as carboxylic acids, esters, lactones, polymer biodiesel, bio-plastics, bio-alcohols, exopolysaccharides. This review presents an over view of catalytic transformation of CO 2 into biofuels and biomaterials by chemical and biological methods. [ABSTRACT FROM AUTHOR]

In the current study, the feasibility of utilizing municipal secondary wastewater sludge for Polyhydroxyalkanoate (PHA) extraction was improved by optimization of various parameters (temperature, duration and concentration of sludge solids). Optimized process parameters resulted in PHA recovery of 0.605 g, significantly higher than un-optimized conditions. The characterization of PHA was carried out by GC–MS, FT-IR and NMR ( 1 H and 13 C) spectroscopy. The PHA profile was found to be dominated by mcl PHA (58%) along with other diverse PHA. The results of the present study show rich diversity of PHA extracted from a raw material which is readily available at minimal cost. In conclusion, exploring the potential of wastes for production of bioplastics not only reduces the cost of bioplastic production, but also provides a sustainable means for waste management. [ABSTRACT FROM AUTHOR]

Due to industrialization and urbanization, as humans continue to rely on fossil fuels, carbon dioxide (CO 2 ) will inevitably be generated and result in an increase of Global Warming Gases (GWGs). However, their prospect is misted up because of the environmental and economic intimidation posed by probable climate shift, generally called it as the “green house effect”. Among all GWGs, the major contributor in greenhouse effect is CO 2 . Mitigation strategies that include capture and storage of CO 2 by biological means may reduce the impact of CO 2 emissions on environment. The biological CO 2 sequestration has significant advantage, since increasing atmospheric CO 2 level supports productivity and overall storage capacity of the natural system. This paper reviews CO 2 sequestration mechanism in bacteria and their pathways for production of value added products such as, biodiesel, bioplastics, extracellular polymeric substance (EPS), biosurfactants and other related biomaterials. [ABSTRACT FROM AUTHOR]

Proteomics and metabolomics analysis has become a powerful tool for characterization of microbial ability for fixation of Carbon dioxide. Bacterial community of palaeoproterozoic metasediments was enriched in the shake flask culture in the presence of NaHCO 3 . One of the isolate showed resistance to NaHCO 3 (100 mM) and was identified as Serratia sp. ISTD04 by 16S rRNA sequence analysis. Carbon dioxide fixing ability of the bacterium was established by carbonic anhydrase enzyme assay along with proteomic analysis by LC–MS/MS. In proteomic analysis 96 proteins were identified out of these 6 protein involved in carbon dioxide fixation, 11 in fatty acid metabolism, indicating the carbon dioxide fixing potency of bacterium along with production of biofuel. GC–MS analysis revealed that hydrocarbons and FAMEs produced by bacteria within the range of C 13 –C 24 and C 11 –C 19 respectively. Presence of 59% saturated and 41% unsaturated organic compounds, make it a better fuel composition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of novel CAB@BOFe for safe drinking water production perspective. • Maximum adsorption capacity of CAB@BOFe was 62.5 µg g−1 for As(V) in 120 min. • Homogenous As(V) sorption onto CAB@BOFe followed pseudo–second–order model. • Trivial reduction (∼3.6 %) in As(V) sorption efficiency after 5 regeneration cycles. • Significant removal (52.1%) of As(V) from multi contaminants mixture with CAB@BOFe. Arsenic (As) can geogenically and anthropogenically contaminate the potable water resources and undoubtedly reduces its availability for human consumption. To circumvent this predicament, present study focuses on the development of a novel biosorbent by impregnating calcium cross-linked polyuronate (alginate) beads (CABs) with bilayer–oleic coated magnetite nanoparticles (CAB@BOFe) for As(V) removal. Initially, the system parameters (i.e., adsorbents dose (0.1– 3.0 g L–1), pH (4.0–13), reaction times (0–180 min) and sorbate concentrations (10–150 µg L–1)) were optimized to establish adsorbent at the lab-scale. CAB@BOFe had higher monolayer (ad)sorption capacity (∼62.5 µg g−1, 120 min) than CABs (∼17.9 µg g−1, 180 min). Electrostatic/Ion-dipole interactions and surface-complexation mechanisms mediated As(V) sorption onto CAB@BOFe mainly obeyed Langmuir isotherm (R2 ∼ 0.9) and well described by intraparticle diffusion process. Furthermore, it demonstrated an excellent arsenate removal performance from the single/multiple anionic contaminants simulated water samples which supported its prospective field applicability. [ABSTRACT FROM AUTHOR]

In the present study, feasibility of biodiesel production from freeze dried sewage sludge was studied and its yield was enhanced by optimization of the in situ transesterification conditions (temperature, catalyst and concentration of sludge solids). Optimized conditions (45 °C, 5% catalyst and 0.16 g/mL sludge solids) resulted in a 20.76 ± 0.04% biodiesel yield. The purity of biodiesel was ascertained by GC–MS, FT-IR and NMR ( 1 H and 13 C) spectroscopy. The biodiesel profile obtained revealed the predominance of methyl esters of fatty acids such as oleic, palmitic, myristic, stearic, lauric, palmitoleic and linoleic acids indicating potential use of sludge as a biodiesel feedstock. [ABSTRACT FROM AUTHOR]

The present work involved screening of a previously reported carbon concentrating oleaginous bacterial strain Serratia sp. ISTD04 for production of PHA and optimization of process parameters for enhanced PHA and biomass generation. The selected bacterial strain was screened for PHA production based on Nile red staining followed by visualization under fluorescence microscope. Spectrofluorometric measurement of Nile red fluorescence of the bacterial culture was also done. Confirmatory analysis of PHA accumulation by GC–MS revealed the presence of 3-hydroxyvalerate. Detection of characteristic peaks in the FT-IR spectrum further confirmed the production of PHA by the bacterium. Response Surface Methodology was used for optimization of pH and carbon sources’ concentrations for higher PHA production. There was almost a 2 fold increase in the production of PHA following optimization as compared to un-optimized condition. The study thus establishes the production of PHA by Serratia sp. ISTD04. [ABSTRACT FROM AUTHOR]

• Negative contaminant removal (NR) i.e. higher concentrations in effluent is globally prevalent. • No treatment systems avoid negative removal for pharmaceutical personal care products. • Conventional WWTPs illustrated the highest NR for Carbamazepine, and Carbadox. • Globally, NR efficiencies for emerging contaminants varied between −0.2 to 1174%. • Separation processes, conjugation–deconjugation, biotransformation, and leaching lead to NR. Emerging contaminants (ECs) are not completely removed by wastewater treatment owing to their capabilities of making complexes, toxic derivatives, byproduct formation, and dynamic partitioning. Negative contaminant removal i.e., higher concentrations (up to 5731%) of these ECs in the effluent with respect to the influent sampled on the same occasions, is globally prevalent in almost all types of treatment systems. Conventional WWTPs showed the highest negative removal (NR) for Carbamazepine, and Carbadox. Conjugation–deconjugation, types of WWTPs, transformations, leaching, operational parameters, sampling schemes, and nature of substance governs the NR efficiencies. Among the various categories of micropollutants, pesticides and beta-blockers are reported to exhibit the maximum percentage of NR, posing threat to human and the environment. With > 200% of NR for beta-blockers, low blood-pressure related symptoms may likely to get more prevalent in the near future. Study red-flags this phenomenon of negative removal that needs urgent attention. [ABSTRACT FROM AUTHOR]

Highlights: [•] Acidogenesis and solventogenesis in C. acetobutylicum are not mutually exclusive. [•] Solventogenesis is not limited to the stationary growth phase. [•] Two negative feedback loops control acidogenesis. [ABSTRACT FROM AUTHOR]

• Microalgal engineering to enhance proficiency as biofuel resource. • Comprehensive account on algomics for enhanced lipid production. • Shifts in metabolic flux could alter the algal physiology and lipid generation. • Intervention of genetic and metabolic switches boost algae-based biofuel production. Conventional fuel resources are overburden with speedy global energy demand which ensued the urgent need of alternate energy resources. Biofuel generation efficiency of microalgae is notable due to their comparatively rapid biomass production rate and high oil content. But, the employment of microalgae as biofuel resource is in infancy due to low productivity and high production cost. The issues can be addressed by employing engineered microalgal strains that would be able to efficiently generate enhanced levels of biomass with augmented lipid and/or carbohydrate content for proficient biofuel production. Genetic alterations and metabolic engineering of microalgal species might be helpful in developing high stress-tolerant strains with improved properties for biofuel generation. Various omics approaches appeared significant to upgrade the microalgal lipid production. Intervention of genetic and metabolic engineering approaches would facilitate the development of microalgae as a competent biofuel resource and inflate the economic commercialization of biofuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Anaerobic digestion (AD) is a greener approach applied for biogas production. • Production and up-gradation of biogas rely upon feedstock types and AD processes. • The application of additives improves the performance of anaerobic digestion. • Techno-economic and life cycle assessment are important for AD operation. The expanding interest towards biogas generation from biowaste via complex anaerobic digestion (AD) opened new avenues in the improvement of biogas production processes and their up-gradation. The adsorption/removal of impurities particularly hydrogen sulfide (H 2 S) and carbon dioxide (CO 2) from the biogas stream will significantly improve the efficiency of biogas for its further use as a renewable energy fuel. The production and up-gradation of biogas rely upon the types of feedstocks, AD condition, microbial diversity, purification methods along with the application of various additives. In that context, this review aims to emphasize the current state of the art in the field of biogas production via AD using diverse bio-waste. Further, this review will critically explore the biogas up-gradation technologies adopted so far and their pros and cons. Finally, techno-economic and environmental impact assessment of the biogas production process will be underlined to make the process cost-effective and environmentally sustainable. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chemoenzymatic COS generation employing ionic liquids and T. lanuginosus chitinase. • IL pretreated chitin appeared amorphous and could facilitate enzyme accessibility. • Optimization led to 1.5 and 1.3 fold enhanced (GlcNAc) 2 and (GlcNAc) 3 production. • 0.1 g of both (GlcNAc) 2 and (GlcNAc) 3 was purified from 1 g TBP pretreated chitin. • Proficient bio-catalytic valorization of coastal residuals to chito-bioactives. The aim of this work was to study a two-step chemoenzymatic method for production of short chain chitooligosaccharides. Chitin was chemically pretreated using sulphuric acid, sodium hydroxide and two different ionic liquids, 1-Ethyl-3-methylimidazolium bromide and Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate under mild processing conditions. Pretreated chitin was further hydrolyzed employing purified chitinase from Thermomyces lanuginosus ITCC 8895. Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate treated chitin appeared amorphous and resulted in generation of 1.10 ± 0.89 mg ml−1 of (GlcNAc) 2 and 1.07 ± 0.92 mg ml−1 of (GlcNAc) 3. Further derivation of optimum conditions through two-factor-9 run experiments resulted in to 1.5 and 1.3 fold increments in (GlcNAc) 2 and (GlcNAc) 3 production, respectively. 0.1 g of both (GlcNAc) 2 and (GlcNAc) 3 has been purified from the Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate pretreated chitin (1 g) employing cation exchange chromatography. The present study will lay the foundation for development of a green sustainable solution for cost effective upcycling of coastal residual resources to chito-bioactives. [ABSTRACT FROM AUTHOR]

• Lignin is a profuse macromolecule and potential feedstock for production of fuels and chemicals. • Several thermochemical strategies have been adopted for valorization of lignin. • Bacteria conversion is considered as an environmentally friendly approach. • Biovalorization of lignin is highly favored by genus Pseudomonas with significant relevance to industrial biotechnology. The most prominent aromatic feedstock on Earth is lignin, however, lignin valorization is still an underrated subject. The principal preparatory strategies for lignin valorization are fragmentation and depolymerization which help in the production of fuels and chemicals. Owing to lignin's structural heterogeneity, these strategies result in product generation which requires tedious separation and purification to extract target products. The bacterial genus Pseudomonas has been dominant for its lignin valorization potency, owing to a robust enzymatic machinery that is used to funnel variable lignin derivatives into certain target products such as polyhydroxyalkanotes (PHAs) and cis, cis -muconic acid (MA). In this review, the potential of genus Pseudomonas in lignin valorization is critically reviewed along with the advanced genetic techniques and tools to ease the use of lignin/lignin-model compounds for the synthesis of bioproducts. This review also highlights the research gaps in lignin biovalorization and discuss the challenges and possibilities for future research. [ABSTRACT FROM AUTHOR]

• Principles, mechanisms, and fundamentals for biochar ball milling are reviewed. • Ball milling is an emerging technology for the production of engineered biochar. • Ball-milled biochar shows good performance in environmental and energy applications. • Functionalization and sustainability assessment are prospects for future studies. Mechanochemical synthesis of nano-biochar by ball-milling technology is gaining attention for the sake of its low-cost and eco-friendly nature. Ball milling as a non-/less-solvent technology can propel environmental sustainability and waste valorization into engineered biochar for advanced applications. Scalable production of biochar nanomaterials with superior properties (e.g., 400–500 m2 g−1 surface area and 0.5–1000 nm pore sizes) enables diverse applications in the field of energy and environment. This review critically evaluates the synthesis, characterization, and application of ball-milled biochar nanomaterials based on the latest findings. Limitations such as feedstock selection, process optimization, product homogeneity and reusability, environmental risks, and sustainability assessment remain challenging for further studies. This work highlights the recent advances on mechanochemical biochar technology and offer insights into opportunities and future prospects related to sustainable and facile synthesis of biochar-based novel materials for achieving sustainable development goals. [ABSTRACT FROM AUTHOR]

• Integrated remediation of PTSWW employing microalgae and biogas generation. • Microalgal species were cultivated in different concentrations of PTSWW. • Microalgal species showed up to 88% reduction in nutrient load of PTSWW. • Biogas yield of 26–925 ml g−1 VS has been observed. In the present work Chlorella pyrenoidosa , Scenedesmus abundans and Anabaena ambigua have been evaluated for their biomass, phycoremediation efficiency and biomethane production potential by cultivating them in the primary treated sewage waste water (PTSWW) under controlled conditions. By the end of 25-day experiment, up to 52–88% reduction was observed in the nutrient concentration from the 3:1 ratio of PTSWW. Co-digestion of microalgal biomass (dry) with cow dung was performed to estimate biomethane potential. Biogas yield of 618–925 ml g−1 VS with 48–65% of methane content was obtained employing the microalgal species cultivated in PTSWW. Microalgae appeared notably competent at nutrient sequestration from PTSWW with significant microalgal biomass productivity for biogas production. Energy balance studies revealed the feasibility of coupling the remediation with energy generation. High photosynthetic rate and biomass generation ability along with nutrient confiscation supports employment of microalgae as a potential next generation biofuel source with waste management. [ABSTRACT FROM AUTHOR]

The present investigation deals with the utilization of biochar derived from the pyrolysis of microalgae Scenedesmus dimorphus as an adsorbent for the removal of cobalt (II) ion (Co) from aqueous solution. A series of experiments were conducted in a batch system to evaluate the performance of the biochar for Co removal. The effect of contact time on adsorption of Co (II) onto surface of the biochar was investigated. The equilibrium sorption data were analyzed by using Langmuir, Freundlich, Temkin, Harkins-Jura and Dubinin-Radushkevich (D-R) isotherms and were found to be adequate in describing the Co adsorption onto the biochar. Equilibrium data were well fitted for Freundlich, Temkin and D-R isotherms. The kinetic study of Co (II) adsorption on microalgae biochar were described by applying pseudo-first-order and pseudo-second-order rate equations. The surface of adsorbent before and after the removal of Co (II) was characterized by using SEM, EDX and XRD analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sustainable bioenergy production is possible via plant microbial fuel cell (PMFC) • Payback time of PMFC could be reduced by improvisation. • Optimization of different additives can increase power efficiency via PMFC. • Usage of low-cost electrode material can reduce the overall production cost of PMFC. Microbial fuel cells (MFCs) are considered as greener technologies for generation of bioenergy and simultaneously treatment of wastewater. However, the major drawback of these technologies was, rapid utilization of substrate by the microbes to generate power. This drawback is solved to a great extent by plant microbial fuel cell (PMFC) technology. Therefore, this review critically explored the challenges associated with PMFC technology and approaches to be employed for making it commercially feasible, started with brief introduction of MFCs, and PMFCs. This review also covered various factors like light intensity, carbon dioxide concentration in air, type of plant used, microbial flora in rhizosphere and also electrode material used which influence the efficiency of PMFC. Finally, this review comprehensively revealed the possibility of future intervention, such as application of biochar and preferable plants species which improve the performance of PMFC along with their opportunities challenges and prospects. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sawdust and plastic waste are used to prepare biochars for CFX and SMX removal. • Sawdust biochar (SB) showed higher antibiotics removal compared to the hybrid one. • SB reported >95% and >99% removal efficiency for CFX and SMX, respectively. • Adsorption processes followed the PSO (R2=>0.8) kinetic model. • Adsorption occurred via H-bonding, electrostatic and π–π EDA interactions. We produced carbon-negative biochar from the pyrolysis of sawdust biomass alone (SB) and from the co-pyrolysis of sawdust and plastic waste (SPB). The co-pyrolysis approach in this study was driven by several hypothetical factors, such as increased porosity, surface chemistry, stability, as well as waste management. We applied pyrolyzed and co-pyrolyzed biochars for the removal of ciprofloxacin (CFX) and sulfamethoxazole (SMX). Due to its more alkaline and amorphous nature, SB showed better removal efficiencies compared to SPB. The maximum removals of CFX and SMX with SB were observed as ∼95% and >95%, respectively whereas with SPB were 58.8%, and 34.9%, respectively. The primary mechanisms involved in the adsorption process were H-bonding, electrostatic and π–π electron donor–acceptor interactions. Homogenously and heterogeneously driven adsorption of both antibiotics followed the pseudo-second-order kinetic model, implying electron sharing/transfer (chemisorption) mediated adsorption. The work is highly pertinent in the context of emerging concerns related to drivers that promote antimicrobial resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • TGA at three heating rates is performed to access the kinetics of treated sunnhemp. • KAS, FWO, Friedman and Starink methods used to find activation energy of pyrolysis. • Pre exponential factor (A) is calculated using DAEM method. • Linear relationship between E a and ln A is established with R2 = 0.95. • Standard deviation calculated to validate the activation energy values. Sun hemp fibers are natural fibers obtained from plants grown in India and nearby countries. It is lignocellulosic biomass having the complex structure of hemicelluloses, cellulose and lignin. Chemical treatment of natural fibers is in practice to enhance the properties being used as reinforcement. Alkaline-treated fiber was sampled and thermal stability along with kinetic parameters was assessed with thermo gravimetric data at heating rates 10, 20 and 30 °C/min using four model-free methods Kissinger–Akahira–Sunose (KAS), Flynn-Wall-Ozawa (FWO), Friedman (FM), Starink (STAR) along with Distributed activation energy model (DAEM) to calculate pre-exponential factor. The calculated activation energy E a by these model-free methods were in the range of 93.3–104.8 kJ/mol and pre-exponential factor (A) was observed between the range 46.6 x103–90.5 x106/min by the DAEM method. The standard deviation (σ) calculated from average activation energy using all four methods was 4.5 kJ/mol, which showed the consistency in the methods employed to determine the activation energy of sun hemp. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crop residues are renewable biomass for biochar production. • Effects of biochar on anaerobic digestion (AD) efficiency are reviewed. • The role and mechanism of biochar in anaerobic digestion system are scrutinized. • Limits and prospects for biochar application in the real world are highlighted. • AD is found to be cost-effective to convert organic waste into renewable energy. Anaerobic digestion (AD) is a viable and cost-effective method for converting organic waste into usable renewable energy. The efficiency of organic waste digestion, nonetheless, is limited due to inhibition and instability. Accordingly, biochar is an effective method for improving the efficiency of AD by adsorbing inhibitors, promoting biogas generation and methane concentration, maintaining process stability, colonizing microorganisms selectively, and mitigating the inhibition of volatile fatty acids and ammonia. This paper reviews the features of crop waste-derived biochar and its application in AD systems. Four critical roles of biochar in AD systems were identified: maintaining pH stability, promoting hydrolysis, enhancing the direct interspecies electron transfer pathway, and supporting microbial development. This work also highlights that the interaction between biochar dose, amount of organic component in the substrate, and inoculum-to-substrate ratio should be the focus of future research before deploying commercial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Real-world possible applications of biochar for environmental sustainability are reviewed. • Benefits of biochar is linked with ways of attaining sustainable development goals. • Preparation methods and source materials determine the carbon content of biochar. • Carbon sequestration and contaminant adsorption abilities of biochar needs further exploration. • Biochar has enormous potential to contribute toward waste, energy and pollution management. Biochar has sparked a lot of interest in recent years for various applications such as contaminant removal, carbon sequestration and soil amendment. However, laboratory scale studies dominates over the real-world applications. In this study, we first enumerated on the various ongoing uses of biochar along with adsorption mechanism; and then identified the most suitable source, and efficient method for biochar production; and finally proposed real-world practical applications of biochar as an additive to control diffuse micropollutant pollution along the highways and railway tracks; as well as the pollution through agricultural runoff. We demonstrated that directly or indirectly, biochar can definitely help to achieve all the 17 Sustainable Development Goals. The study on the practical use of biochar is an emerging area, because a lot of research needs are there to realise the full-potential of biochar with ways of attaining sustainable development goals towards waste, energy and pollution management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microwave demands high electrical energy thus it is energy intensive process. • Integration of CAMBI THP with CHP system would result in energy self-sufficiency. • Mechanical process can achieve energy self-sufficiency at high solids concentration. • Pretreatment <100 ℃ shows positive energy balance over the pretreatment at ≥100 ℃. • LCA shows that microwave process has highest global warming potential. Energy sustainability is one of the critical parameters to be studied for the successful application of pretreatment processes. This study critically analyzes the energy efficiency of different energy-demanding sludge pretreatment techniques. Conventional thermal pretreatment of sludge (∼5% total solids, TS) produced 244 mL CH 4 /gTS, which could result in a positive energy balance of 2.6 kJ/kg TS. However, microwave pretreatment could generate only 178 mL CH 4 /gTS with a negative energy balance of −15.62 kJ/kg TS. In CAMBI process, the heat requirements can be compensated using exhaust gases and hot water from combined heat and power, and electricity requirements are managed by the use of cogeneration. The study concluded that <100 ℃ pretreatment effectively enhances the efficiency of anaerobic digestion and shows positive energy balance over microwave and ultrasonication. Moreover, microwave pretreatment has the highest global warming potential than thermal and ultrasonic pretreatments. [ABSTRACT FROM AUTHOR]