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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 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 Aquatic biomass is promising due to its high productivity in less nutrient environment. Gasification is one of the frontier technologies to convert biomass into energy, mainly to produce electricity. Recent development in electrochemical technologies allows the utilization of electricity to upgrade waste CO2 into chemical products. In the present study, the performance of integrated gasification and electrolyzer is evaluated. The gasification converts biomass into syngas and electricity, while the electrolyzer convert CO2 from the gasification residue into chemicals such as CO and methanol by utilizing the electric power from the gasification. The variation of the gasifying agent flow rate (O2 equivalence ratio between 0.36 and 1.00) provides the variation of syngas composition (H2: 28–65%; CO: 25–43%) and heating value (12–30 MJ/kg). The production of CO or methanol is significantly influenced by O2 equivalence ratio and fraction of syngas into power generator. The highest exergy loss is found to be in the cooling system. The net CO2 emission of the proposed configuration is negative (−0.09 to −0.17 kg CO2/GJ at O2 equivalence ratio of 0.36) by considering the CO2 consumption of the biomass feed. Therefore, this system is promising for further investigation as the future renewable technology for energy conversion.

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.

The Himalaya has a rich ancient tradition for tapping hydro-energy from the hill streams and rivers through the device of gharats (watermills). The present contribution encompasses the study on the energy consumption pattern of hill communities living in buffer zone of the Nanda Devi Biosphere Reserve, a world heritage site located in Garhwal Himalayas, India, The current status of gharats, the factors responsible for the neglect of this renewable energy device, initiatives taken for upgrading for their revival have been highlighted. Field and policy level opportunities and constraints associated with promotion of such hydro-energy in the study area by upgrading of traditional watermills are analysed and suitable options for removing impediments are suggested.

Abstract With the rising population and affluence, the management of significantly increased quantity of municipal solid waste is reaching a critical level in almost all regions of the world. The organic fraction of municipal solid waste (OFMSW) has been recognised as a major contributor to climate change, human health risk and ecosystem imbalance. Anaerobic digestion of OFMSW is a reliable and attractive option to convert the complex organic materials into a clean and renewable source of energy. This manuscript begins by providing an overview of physical, chemical and compositional characteristics of OFMSW followed by the presentation of optimum environmental and operational conditions for anaerobic digestion performance, and discussions on the various pretreatment and other in-situ strategies to improve process performance. Future research should focus on reactor improvement, process optimisation and a rigorous life cycle assessment for deploying the pretreatment technology successfully at a commercial scale.

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.