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Abstract Sugarcane is a major crop cultivated globally and the residue left over after the crop harvest and extraction of juice is a good biomass source that can be used for the production of several useful chemicals. The sugarcane bagasse is an excellent substrate for the production of various biochemicals and enzymes through fermentation. Now major interest is focused on the utilization of these residue for biofuel production. The sugarcane crop residue is rich in cellulose and hemicellulose, hence it can be used for the production of bioethanol and other liquid transportation fuels. The present review gives a detailed account of the availability of sugarcane residue and various commercially important products that can be produced from this residue. It also provides recent developments in R&D on the bioconversion of sugarcane crop residue for value added products.

Abstract A vapour absorption refrigeration system (VARS) in which a transfer tank replaces the conventional solution pump is analysed. Six fluid pairs with R22 as the refrigerant and different absorbents: DMA; DMF; DMETEG; DMETrEG; DMEDEG; and NMP are considered. Variations in COP, circulation ratio, percent mass of generated vapour utilised for transfer-tank operation, and minimum generator temperature are compared over a wide range of operating conditions. In general, R22-DMA, R22-DMF, and R22-DMETrEG are preferable for a transfer-tank operated VARS. At high generator temperatures or low condenser temperatures, R22-DMA gives the best overall performance. When the temperatures of the evaporator, absorber, and condenser are high, one may prefer R22-DMF as the working fluid.

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.

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 Fuel crisis because of dramatic increase in vehicular population and environmental concerns have renewed interest of scientific community to look for alternative fuels of bio-origin such as vegetable oils. Vegetable oils can be produced from forests, vegetable oil crops, and oil bearing biomass materials. Non-edible vegetable oils such as linseed oil, mahua oil, rice bran oil, etc. are potentially effective diesel substitute. Vegetable oils have high-energy content. This study was carried out to investigate the performance and emission characteristics of linseed oil, mahua oil, rice bran oil and linseed oil methyl ester (LOME), in a stationary single cylinder, four-stroke diesel engine and compare it with mineral diesel. The linseed oil, mahua oil, rice bran oil and LOME were blended with diesel in different proportions. Baseline data for diesel fuel was collected. Engine tests were performed using all these blends of linseed, mahua, rice bran, and LOME. Straight vegetable oils posed operational and durability problems when subjected to long-term usage in CI engine. These problems are attributed to high viscosity, low volatility and polyunsaturated character of vegetable oils. However, these problems were not observed for LOME blends. Hence, process of transesterification is found to be an effective method of reducing vegetable oil viscosity and eliminating operational and durability problems. Economic analysis was also done in this study and it is found that use of vegetable oil and its derivative as diesel fuel substitutes has almost similar cost as that of mineral diesel.

Abstract Microalgae farming has gained interest because of the heavy processing requirement of non-renewable fuel sources and increased vegetable oil prices that prevent them from being used for biodiesel production. Chlorella varibilis MK039712.1, a freshwater microalga with 24.0 ± 0.6% w/w lipid was isolated from Valparai, Coimbatore district, Tamil Nadu, India, that was dried, lysed to extract it for biodiesel production. The present study aims to produce biodiesel from the Chlorella variabilis MK039712.1 algal oil by optimizing the transesterification conditions by varying catalyst concentration, methanol to oil molar ratio, time, temperature using Response Surface Methodology. At 8:1 methanol to algal oil molar ratio, 0.3 wt % of catalyst, 65 °C reaction temperature and 120 min reaction time, a maximum of 96% biodiesel yield was obtained. The variations in chemical structure of the transesterified algal oil was analyzed using Fourier Transform Infra-Red Spectroscopy, 1H Nuclear Magnetic Resonance and 13C Nuclear Magnetic Resonance. The fuel properties were also determined and found comparable with the ASTM standards.

Abstract Environmental concerns regarding the use of potentially harmful chemicals and fossil fuels stimulate research efforts on the multifunctional hybrid nanocomposites produced from biowastes via simple environmentally friendly processes. Such nanomaterials could help to combat the escalating environmental issues related to environmental remediation and energy storage, as a step to the renewable energy technology of the future. This work discusses the synthesis of novel nickel-based reduced graphene oxide (rGO) nanostructured composites with superior energy storage and photocatalytic properties. Using a facile hydrothermal method, rGO nanoflakes were synthesized from the negative value coconut coir biowaste and then decorated with functional NiO and NiFe2O4 nanoparticles to produce hierarchical functional nanocomposites. Benefiting from the synergies arising from the concomitant use of NiFe2O4 nanoparticles and rGO nanoflakes, the resultant nanocomposites yielded excellent specific capacitance of 599.9 F/g at current density of 1 Ag-1 and retention rate of 86.5% even after 2000 cycles. Moreover, the composite exhibited excellent efficiency of visible light driven photocatalytic degradation of 96.5%. Thus, our material is essentially multifunctional and importantly, it demonstrates quite pronounced electrochemical and photocatalytic activities when produced in a simple, single technological route. These findings confirm that the developed multifunctional nanostructured composite is a strong candidate material for energy and environmental remediation applications.

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.