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The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing the oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil on biodiesel led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol.

Abstract A novel approach to the intensification of renewable and sustainable production of photoautotrophic ethanol from microalgae was investigated using periodic ultrasonication. The effect of utilizing ultrasonic pulsing during ethanol production using a metabolically engineered ethanol producing cyanobacterium Synechocystis PCC6803 strain NAV001 was analysed with an ultrasonic frequency of 20 kHz. Ultrasonic treatment resulted in enhancement of ethanol yields. The ethanol yield was found to be higher when ultrasonic pulsing was initiated during the exponential phase of growth. The optimum ultrasonic conditions for enhanced yield of ethanol within this model system was found to be 30 °C, 15% of power input (97.5 W) and 10 min pulse time. The cytotoxic effect of ultrasonic pulsation was investigated by analysing the survival percentage and auto-fluorescence of the cyanobacterium via imaging by confocal laser scanning microscopy. The overall effect of ultrasonic dose on ethanol production and growth rate of microalgae was analysed by using Haldane inhibition kinetics.

Abstract The use of ozone-depleting CFCs and the escalating energy cost in the conventional vapour compression refrigeration systems make the solar-assisted vapour absorption machines more attractive. Aqua-ammonia vapour absorption systems, essential for solar cold storage application, necessitate the use of a rectification column. The paper presents a steady-state simulation model of a rectification column based on mass, material and energy balances. The model predicts the temperatures, the mass flow rates and the states of the liquid dripping and the vapour rising from each of the plates. The quantitative effect of varying different parameters on the column performance is presented. The simulation model can eventually be used to optimize the rectification column. This can in turn help augment the COP of the entire refrigeration system.

Abstract Lignocellulosic biomass is considered to be a potential raw material for production of renewable fuels like bioethanol and biodiesel. Cellulose and hemicelluloses constitute major portion of the lignocellulosic biomass. Cellulose can be converted to glucose by hydrolysis and subsequently to ethanol by fermentation. The hemicellulosic portion mostly contains pentose sugars which cannot be utilized by many microorganisms for ethanol production. Acid pretreatment results in separation of a pentose-rich fraction which can be utilized for the production of various high value chemicals. The present study evaluates the utilization of pentose sugars as co-substrate, along with biodiesel industry-generated crude glycerol, for the production of 1,3-propanediol (1,3-PDO). Bioconversion of these low value byproducts into a high value chemical would be an economically advantageous strategy in terms of waste disposal for biorefineries. In this study, the production of 1,3-propanediol from the acid pretreated liquor obtained from rice straw was evaluated using Klebsiella pneumonia. Different carbon sources like pure hexose and pentose sugars, mixed pentose sugar containing acid pretreated liquor (APL) from rice straw and different concentrations of pentose sugars and acid pretreated liquor were evaluated. There is 65% increase in titers from 9.55 g/L to 15.75 g/L using APL as co-substrate. With addition of 0.5% (v/v) APL, 1,3-propanediol production reached 20.88 g/L with 0.69 g/g yield and 0.87 g/L/h productivity. The study comprehensively explains the behavior of Klebsiella pneumoniae strain utilizing pentose rich APL and crude glycerol which enroute to an integrated biorefinery approach.

Abstract Major challenges in cultivation, harvesting, CO2 capture and downstream processing of microalgae biomass have to be confronted for successful commercial deployment. This study explored a sustainable process train to mass-produce a native marine algal strain, Nannochloropsis salina, for biocrude production and CO2 capture. The microalga was cultivated in a 3-m2 raceway pond with manual agitation, 10-m2 raceway ponds with and without CO2 supplementation and a 120-m2 pond with CO2 supplementation using carbonation column reactor (CCR). During the above experiments, the areal productivities obtained ranged from 7.5 to 34.4 g m−2 d−1 and the lipid content was between 29 and 80%. This study also demonstrated a novel 10 KLPD (kilolitres per day) capacity electropreciflocculation (ePF) reactor (∼0.56–0.78 KWh/KL) and filter press for biomass harvesting with 98.24% efficiency. The CO2 capture of N. Salina estimated was in the range of 45.38–208.12 tons ha−1 y−1, and the average was 95.39 tons ha−1 y−1. The cost estimated based on the 120-m2 pond trials was $3.46/kg of dry algal biomass. Thus the findings provide immense scope for future research on large-scale cultivation of Nannochloropsis salina for biofuel production and carbon capture applications.

Abstract Hydrokinetic turbine (HKT) generates electricity from the kinetic energy of flowing water and is suitable for energizing remote communities living in the proximity of rivers or canals. In this paper, a procedure for sizing components of a standalone hybrid energy system involving hydrokinetic turbine, photovoltaic and battery storage system is explained. Appropriate choices of optimum number and size of HKT modules, PV array capacity and minimum storage requirement are essential for the success of HKT-PV-battery system. The hydrokinetic turbine is modelled as a Savonius turbine and the performance parameters are established using ANSYS. Determination of the system design space is explained with an illustrative example, based on a time series simulation of the entire system. The sizing curve of the hybrid system is generated by plotting the PV array rating vs storage capacity diagram for a specified number of HKT modules. A parametric study of hydrokinetic turbine is conducted to generate a set of sizing curves and the best system configuration is identified.

Abstract Development of solid mixed oxide catalyst from waste biomass is a scarcely studied area. Thus, present protocol aims to prepare an environmentally friendly, efficient, renewable and recyclable heterogeneous base catalyst from Carica papaya stem. The chemical and structural properties of the catalyst were examined by Fourier-transform infrared spectroscopy (FTIR), X-ray diffractograms (XRD), Scanning electron microscopy (SEM), Energy Dispersive X-ray spectrometry (EDX), Transmission Electron Microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis. The CO2-TPD and Hammett indicator test was conducted to determine the basicity of the prepared catalyst. The study revealed the presence of alkali and alkaline earth metals that provide the basic sites to facilitate transesterification reaction for biodiesel production and formation of benzylidenemalononitrile (BMN). The conversion of the waste cooking oil (WO) and Scenedesmus obliquus (SO) lipid to biodiesel was confirmed by the NMR and Gas chromatography Mass Spectroscopy (GC-MS) technique. Biodiesel conversions of 95.23% and 93.33% were achieved using 2 wt % catalyst loading under optimized reaction conditions for WO and SO respectively. Reusing the catalyst showed a slight drop in activity after 6 repeated uses. The reported catalyst has shown its potential as an alternative and cheaper green solid catalyst for biodiesel production and Knoevenagel reaction.

Abstract An indirect forced convection and desiccant integrated solar dryer is designed and fabricated to investigate its performance under the hot and humid climatic conditions of Chennai, India. The system consists of a flat plate solar air collector, drying chamber and a desiccant unit. The desiccant unit is designed to hold 75 kg of CaCl2-based solid desiccant consisting of 60% bentonite, 10% calcium chloride, 20% vermiculite and 10% cement. Drying experiments have been performed for green peas at different air flow rate. The equilibrium moisture content Me is reached in 14 h at an air flow rate of 0.03 kg/m2 s. The system pickup efficiency, specific moisture extraction rate, dimensionless mass loss, mass shrinkage ratio and drying rate are discussed in this paper.