Pyrolytic urban mining of waste printed circuit boards: an enviro-economic analysis.

E-waste, a global environmental concern resulting from supply chain inefficiency, also offers the opportunity to recover valuable materials, including general and rare earth metals. Waste printed circuit boards (WPCBs) are integral components of e-waste that contains substantial amounts of precious metals, making them a valuable waste category. Pyrolysis has emerged as a promising method for material recovery from WPCBs. Hence, pyrolytic urban mining of WPCBs offers an excellent avenue for resource recovery, redirecting valuable materials back into the supply chain. Under the current study, experimental investigation has been conducted to explore the recovery of materials from WPCBs through pyrolysis followed by process simulation, economic analysis, and life cycle assessment (LCA). An Aspen Plus simulation was conducted to model the pyrolysis of WPCBs and subsequent product recovery using a non-equilibrium kinetic model, which represents a unique approach in this study. Another distinct aspect is the comprehensive assessment of environmental and economic sustainability. The economic analysis has been carried out using Aspen economic analyzer whereas the LCA of WPCB pyrolysis has been conducted using the SimaPro software. The experimental investigation reveals yield of solid residues are about 75-84 wt.%, liquid yields of 6-13 wt.%, and gas yields of 4-21 wt.%, which is in well agreement with the Aspen Plus simulation results. The economic analysis for an e-waste pyrolysis plant with an annual feed rate of 2000 t reveals that the total capital cost of a pyrolysis plant is nearly $51.3 million, whereas the total equipment cost is nearly $2.7 million and the total operating cost is nearly $25.6 million. The desired rate of return is 20% per year and the payback period is 6 years with a profitability index of 1.25. From the LCA, the major impact categories are global warming, fossil resource scarcity, ozone formation in human health, ozone formation in terrestrial ecosystems, fine particulate matter formation, and water consumption. The findings of this study can serve as a guideline for e-waste recyclers, researchers, and decision-makers in establishing circular economy.

Comparative studies on biomass productivity and lipid content of a novel blue-green algae during autotrophic and heterotrophic growth.

Algae have long been acclaimed as the attractive renewable source for generating third-generation biofuels, particularly biodiesel. Under the present investigation, the trends of production of biomass and lipid during the autotrophic and heterotrophic growth of newly isolated blue-green algae, Leptolyngbya subtilis JUCHE1, were compared and correlated with the variation in C-sources. In the autotrophic and heterotrophic growth studies, CO2 and glycerol were respectively used as the inorganic and organic C-sources maintaining equivalence in the initial amount of carbon. Light was used as the source of energy in both cases. The concentration of CO2 in the feed gas stream was varied from 5 to 20% (% v/v). Equivalent quantity of carbon was supplied through glycerol during heterotrophic growth. Small-scale closed algal bioreactors were used for growing the algae at 37 °C and 2.5 kLux light illumination in batch mode for 0-4 days. Primarily, higher biomass production from glycerol compared with CO2 was observed. In case of photoautotrophic growth, the maximum values of biomass and lipid productivity, obtained at 15% CO2, were 0.1857 g/L/d and of 0.020 g/L/d respectively. The maximum biomass productivity of 0.2733 g/L/d was obtained for photoheterotrophic growth at a glycerol concentration equivalent to 15% CO2 (v/v). Under photoheterotrophic growth of Leptolyngbya subtilis JUCHE1, lipid productivity of 0.0702 g/L/d was obtained at glycerol concentration equivalent to 5% (v/v) CO2, which is 4.66-fold higher than that obtained under corresponding photoautotrophic condition. The "switch-over" from the autotrophy to the photoheterotrophy instigated the oleaginous anabolism and consequent lipid enrichment in L. subtilis JUCHE1, which can be extracted and converted to biodiesel.

Optimization of extraction process of inulin from Indian millets (jowar, bajra and ragi)-characterization and cost analysis.

Prebiotic biomolecule, namely, inulin was extracted from Indian millets, namely, jowar (Sorghum vulgare), bajra (Pennisetum glaucum) and ragi (Eleusine coracana). Through qualitative assessment using Fourier Transform Infrared spectroscopy, the presence of functional groups of inulin in the above mentioned Indian millets were verified. The values of degree of polymerization of inulin derived from jowar, bajra and ragi were determined to be 27, 39 and 23 respectively. A comparative analysis of growth of Lactobacillus casei was carried out in presence of both lactose and inulin extracted from three millets and the commercial one. It was observed that the bajra inulin and lactose combination exhibited the best bacterial growth. The prebiotic effectiveness of different varieties of inulin was calculated to be in the following order: bajra > jowar > ragi > commercial inulin. Therefore the results on bajra inulin were highlighted in this article. Inulin yield from bajra was optimized as a function of temperature, HCl concentration and heating period. The maximum inulin yield (0.4727 g/g bajra) was obtained at temperature 70 °C, HCl concentration of 0.8 M and heating period of 60 min. The prebiotic activity score of bajra inulin (= 3.2) was measured to be much higher than commercial inulin (= 1.0). Growth dynamics of Lactobacillus casei on lactose, bajra inulin and mixture of lactose and bajra inulin were found to be of Monod type, Haldane type and Multi-substrate-summative type respectively. The techno-economic analysis based on the production cost of inulin from raw bajra seeds suggested that it was much cheaper than commercial inulin.

Mixed consortia in bioprocesses: role of microbial interactions.

The utilization of mixed consortia or mixed culture has become a current research trend of applied microbiology, bioprocess engineering and biotechnology. The constituent microorganisms of such mixed cultures can jointly perform complex processes efficiently, yielding the desired product at an augmented rate, in comparison to monocultures. It is understandable that the interactions between the microbial partners in these mixed cultures are expected to have a significant impact on the combined performance of the microorganisms and the bioprocess as a whole. Prevalence of positive interactions (commensalism or mutualism) among microbial members of a mixed culture or consortia can significantly enhance the product outcome of the bioprocess, ensuring their industrial application and long-term stability. On the contrary, negative interaction (parasitism, predation or ammensalism) leads to elimination of microbial members from the consortia causing the destruction of community structure as well as disruption of cumulative performance. Therefore, a priori knowledge on the type of interaction between the microorganisms is also essential for the optimization of the performance of the designed consortia. This could only be achieved through the study of inter-microbial interaction prevailing in a mixed culture. In the present article, different bioprocess applications of mixed cultures, currently in practice along with types of positive microbial interactions involved, have been reviewed. Complexity of mixed cultures from the perspective of multiple types of intra-culture relationships has been explained in detail. Overall, the necessity for more in-depth research studies on "microbial interaction" in mixed culture bioprocesses has been stressed in the article.

Analysis of cell growth dynamics of Pediococcus acidilactici in the presence of inulin in an optimized microenvironment.

The present investigation deals with the optimization of cell growth rate of the candidate probiotic Pediococcus acidilactici in the presence of the specific prebiotic inulin. Three independent variables viz. concentration of inulin, concentration of glucose and pH have been selected for optimization study using response surface methodology. Theoretical analysis indicates that the maximum cell growth rate occurs at pH 7, 20 g/dm(3) concentration of inulin and 20 g/dm(3) concentration of glucose. Validation of these values has been done through a set of programmed experiments. Studies on cell dynamics in the presence of different concentrations of inulin have also been carried out to identify any limitation on the initial inulin concentration. Results clearly indicate that cell growth is enhanced with the increase in inulin concentration. However, there is a critical value of the prebiotic concentration (20 g/dm(3) inulin) beyond which the cell growth is inhibited. A summative type growth model has been proposed to explain the growth behaviour of P. acidilactici in the presence of the dual substrate, i.e. glucose and inulin. While growth on glucose follows Monod model, Haldane-type substrate-inhibited growth model holds good for growth on inulin. Intrinsic kinetic parameters for all the model equations have been determined experimentally.

In vitro antioxidant and hepatoprotective potential of Azolla microphylla phytochemically synthesized gold nanoparticles on acetaminophen - induced hepatocyte damage in Cyprinus carpio L.

The present study aims to evaluate the hepatoprotective and antioxidant effects of gold nanoparticles (GNaP) biosynthesized through the mediation of Azolla microphylla and A. microphylla extract on acetaminophen-induced hepatocyte damage in common carp fish (Cyprinus carpio L.). The gold nanoparticles (100, 150, 200 µg/ml) and A. microphylla extract powder (100, 200, 400 µg/ml) were added to the primary hepatocytes in different conditions: treatment I (before 12 mM acetaminophen), treatment II (after 12 mM acetaminophen), and treatment III (both before and after 12 mM acetaminophen), and incubated. Among these, control group treated with 12 mM acetaminophen produced significantly elevated levels (50-80%) of lactate dehydrogenase (LDH), catalase (CAT), glutamate oxalate transaminase (GOT), glutamate pyruvate transaminase (GPT), and malondialdehyde (MDA), and significantly decreased the levels (60-75%) of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Treatment with methanol extract of A. microphylla phytochemically biosynthesized gold nanoparticles (100, 150, 200 µg/ml) and A. microphylla methanol extract powder (100, 200, 400 µg/ml) significantly improved the viability of cells in a culture medium. It also significantly reduced the levels of LDH, CAT, GOT, GPT, and MDA, and significantly increased the levels of SOD and GSH-Px. In conclusion, gold nanoparticles biosynthesized through A. microphylla demonstrated effective hepatoprotective and antioxidant effects than methanol extract of A. microphylla.

De-mercurization of wastewater by Bacillus cereus (JUBT1): growth kinetics, biofilm reactor study and field emission scanning electron microscopic analysis.

Removal of mercuric ions by a mercury resistant bacteria, called Bacillus cereus (JUBT1), isolated from the sludge of a local chlor-alkali industry, has been investigated. Growth kinetics of the bacteria have been determined. A multiplicative, non-competitive relationship between sucrose and mercury ions has been observed with respect to bacterial growth. A combination of biofilm reactor, using attached growth of Bacillus cereus (JUBT1) on rice husk packing, and an activated carbon filter has been able to ensure the removal of mercury up to near-zero level. Energy dispersive spectrometry analysis of biofilm and the activated carbon has proved the transformation of Hg(2+) to Hg(0) and its confinement in the system.

Experimental studies and mathematical modeling of an up-flow biofilm reactor treating mustard oil rich wastewater.

Bioremediation of lipid-rich model wastewater was investigated in a packed bed biofilm reactor (anaerobic filter). A detailed study was conducted about the influence of fatty acid concentration on biomethanation of the high-fat liquid effluent of edible oil refineries. The biochemical methane potential (BMP) of the liquid waste was reported and maximum cumulative methane production at the exit of the reactor is estimated to be 785 ml CH(4) (STP)/(gVSS added). The effects of hydraulic retention time (HRT), organic loading rate (OLR) and bed porosity on the cold gas efficiency or energy efficiency of the bioconversion process were also investigated. Results revealed that the maximum cold gas efficiency of the process is 42% when the total organic load is 2.1 g COD/l at HRT of 3.33 days. Classical substrate uninhibited Monod model is used to generate the differential system equations which can predict the reactor behavior satisfactorily.

Experiments and three phase modelling of a biofilter for the removal of toluene and trichloroethylene.

Volatile organic compounds, namely, toluene, trichloroethylene, styrene, etc., disposed off by electronics and polymer industries, are very harmful. The treatment of VOC laden air through biochemical route is one of the potential options for reduction of their concentration in parts per million or parts per billion level. Under the present investigation, a 0.05-m diameter and 0.58-m high trickle bed biofilter has been studied for the removal of VOCs namely toluene and trichloroethylene from a simulated air-VOC mixture using pure strain of Pseudomonas putida (NCIM2650) in immobilized form. Inlet concentrations of VOCs have been varied in two ranges, the lower being 0.20-2.00 g/m(3) and higher being 10-20 g/m(3), respectively. The Monod type rate kinetics of removal of VOCs has been determined. A three-phase deterministic mathematical model has been developed taking the simultaneous reaction kinetics and interphase (gas to liquid to biofilm) mass transfer rate of VOCs into consideration. Experimentally determined kinetic parameters and mass transfer coefficients calculated using standard correlations have been used. Concentrations have been simulated for all the three phases. Simulated results based on the model have been compared with the experimental ones for both gas and liquid phases satisfactorily. The mathematical model validated through the successful comparison with experimental data may be utilized for the prediction of performance of biofilters undergoing removal of different VOCs in any further investigation and may be utilized for the scale-up of the system to industrial scale.