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Bio-energy from lignocellulosic biomass is cleaner, sustainable, and one of the renewable energy sources that could help meet some of our energy demand. Unlike fossil fuels, it can be grown and used repeatedly and its use can replace the fossil fuels. In addition to this, these materials are easily available either in the form of agricultural waste or forest residues and are economically viable. The current study focuses on physico-chemical characterisation of three commonly available lignocellulosic biomasses of north-east India such as Castor (Ricinus communis), Jatropha (Jatropha curcas), and Miscanthus (Miscanthus sinensis) for second generation biofuels production. Ultimate analysis (CHNSO), thermogravimetric analysis, X-ray diffraction, Fourier transformation infrared (FTIR), and oxygen bomb calorimeter techniques were used to characterise the above mentioned three lignocellulose biomasses. It was found that the cellulose content of three biomasses varied from 40% to 44%, hemicellulose content from 8% to 14%, and lignin content varied from 21% to 30%. Chemical structure of lignocellulose is studied through FTIR. The crystallinity index of Castor and Jatropha is similar, i.e., ∼69%, where as crystallinity index of Miscanthus was 72%. Due to the presence of higher carbon and cellulose content along with less moisture (10%–12%), ash (5%–10%), sulphur (0.1%–0.8%), and extractives (12%–20%) make them a very good source for production of alcoholic fuels through a biochemical route.

The utilization of costly chemical fertilizers and large freshwater requirements make the microalgae cultivation process uneconomical and highly unsustainable. To address this challenge, the present study aimed to integrate cattle wastewater (CW) (alternate for fertilizers) with domestic sewage wastewater (DSW) (substitute for freshwater) to cultivate Chlorella thermophile. To maximize the biomass yield, in-depth nutrient consumption patterns in both batch and fed-batch cultivation conditions were analyzed. Out of the eight (1%-4.5%) different CW feed concentrations tested during the batch cultivation, 2.5% CW set gave the highest biomass yield (2.17 g L-1), which was almost double the yield obtained using Bold Basal Medium (1.24 g L-1) and DSW without any CW addition (1.22 g L-1). However, the biomass yield declined with CW> 2.5%, and the ammonium (NH4+) inhibitory effect was observed. To address the (NH4+) toxicity challenge and further enhance the biomass yield, fed-batch experiments were designed with an intermittent CW feeding based on nutrient (NH4+) consumption pattern. The fed-batch cultivation resulted in twofold increased biomass yield (4.52 g L-1) in comparison to the batch process. The nutrient consumption pattern inferred that the (NH4+) concentration greater than 600 mg L-1 during the logarithmic phase was inhibitory for Chlorella thermophila cells. On biomass characterization, a significant improvement in protein content with CW addition was observed. The FAME analysis of the derived lipid stated its competitive biofuel quality with up-gradation of C:16 and C:18 groups. Based on the obtained results, projection analysis for an integrated rural model demonstrated the technology's potential for sustainable water management with valuable resource recovery.

Sn doped and sulfate functionalized red mud produced excellent catalytic activity and stability owing to the synergistic interaction of Sn with components of red mud and enhanced acidic characteristics.

The present study deals with the large scale open system cultivation of the novel microalga: Scenedesmus obliquus SA1 (KC733762) previously isolated in our laboratory. SA1 strain was cultivated in open system at varying CO2 levels ranging from 0.03% to 35% (v/v) and subsequently the carbonic anhydrase activity (CA) and the biochemical properties were monitored. Maximum biomass concentration (1.39 ± 0.023 g L(-1)), CO2 fixation rate (97.65 ± 1.03 mg L(-1)d(-1)) and total CA activity (166.86 ± 3.30 E.U./mg chla) were obtained at 35% CO2. CA inhibitors: acetazolamide and ethoxyzolamide inhibited the external and internal enzyme activity in SA1. High CO2 levels were favorable for the accumulation of lipids and chlorophyll. The present results suggested that SA1 possessed high CO2 tolerance and high carbohydrate, lipid and chlorophyll content when cultivated in open system thus being suitable for CO2 mitigation in outdoor ponds and subsequent generation of value added products.

Abstract Conversion of wastes to energy and other value-added products is considered as a suitable method towards energy security. Wastes from various sources are becoming potential feedstocks for energy production through different techniques. The economy and sustainability of these processes demand the use of low-cost catalysts. Red mud (RM) is one of the most abundantly produced industrial wastes from aluminum industries. Such a huge production of RM, its alkaline nature and the presence of a small quantity of radioactive elements make it an environmental liability. Out of various utilization methods, RM as a catalyst for different chemical processes has been very successful. Presence of many valuable metals in RM, in particular, Fe makes it a suitable catalyst for energy production through processes such as pyrolysis, hydrotreating, transesterification and H2 production from biomass and other sources. This article critically reviews the advances in sustainable energy production through different processes mentioned above by RM based catalysts. Different characterization, activation and stability study of RM along with outcomes and mechanism of these processes are discussed. Furthermore, drawbacks associated with the low catalytic activity of RM and works that need to be carried out in the future for the improvement of its catalytic activity are discussed in detail.

The physicochemical characterization and kinetic evaluation of the thermal and co-pyrolysis of groundnut de-oiled cake (GDC) and PET plastic is examined in this present study. A bomb calorimeter, proximate/CHNS analysis, and a thermogravimetric analyzer were used to study the physicochemical characteristics of the biomass and plastic. By using a FTIR analysis, it was found that both samples had distinct functional groups. Iso-conversional models, such as Friedman’s, the Kissinger–Akhaira–Sunose, the Ozawa–Flynn–Wall, Starink’s, and the distributed activation energy models were employed in the calculation of the kinetic parameters. The physicochemical characterization provided valuable insights into the pyrolysis characteristics. The rate at which the feedstock was heated were 10, 20, and 30 °C min−1, and were used to study the thermal breakdown behavior of the GDC and PET by the TGA. The following temperatures are the active pyrolysis zones for the thermal pyrolysis and the co-pyrolysis: for the groundnut de-oiled cake, T = 150–650 °C; for the PET, T = 375–600 °C; and for the co-pyrolysis, T = 175–550 °C. For the thermal pyrolysis (for GDC, E = 127.49 kJ mol−1; PET, E = 201.45 kJ mol−1); and the co-pyrolysis (E = 175.86 kJ mol−1), Kissinger–Akhaira–Sunose revealed low activation energy.

Thermogravimetric analysis of three lignocellulosic biomass such as Miscanthus grass, Castor stem, and Jatropha stem under high purity nitrogen atmosphere were carried out over a temperature range of 25 °C–900 °C at three different heating rates of 10, 15, 20 °C min−1. The profiles generated from thermal decomposition process signified that except dehydration there were three main stages of degradation occurred associated with three main components (hemicellulose, cellulose, lignin). The temperature peaks at maximum weight loss rate obtained from Differential thermogravimetric thermograms changed with increasing heating rate. The activation energy and pre-exponential factor were calculated by applying two model-free methods and compared. The kinetic parameters obtained from Kissinger and Ozawa methods were in good agreement with the experimental results. The value of kinetic parameters explained the thermal stability of the biomass. The thermal analysis could not infer the composition and chemical structure of lignocellulosic biomass; hence FTIR spectroscopic analysis has been carried out.

In this study, two different unexploited indoor plants, Epipremnum aureum and Dracaena braunii were used to produce clean and sustainable bio-electricity in a plant microbial fuel cell (PMFC). Acid modified carbon fiber brush electrodes as well as bare electrodes were used in both the PMFCs. A bentonite based clay membrane was successfully integrated in the PMFCs. Maximum performance of E. aureum was 620 mV which was 188 mV higher potential than D. braunii. The bio-electricity generation using modified electrode was 154 mV higher than the bare carbon fiber, probably due to the effective bacterial attachment to the carbon fiber owing to hydrogen bonding. Maximum power output of 15.38 mW/m2 was obtained by E. aureum with an internal resistance of 200 Ω. Higher biomass yield was also obtained in case of E. aureum during 60 days of experiment, which may correlate with the higher bio-electricity generation than D. braunii.

The present study investigated the feasibility of domestic sewage wastewater (DSW) as an alternate to fresh-water microalgae growth media towards high-value bioenergy feedstock production. Eight native microalgal strains were screened from DSW and the effect of raw DSW (RDSW), and autoclaved DSW (ADSW) on growth and bioremediation potential were evaluated and compared with control BG11 medium. The study confirmed RDSW as a potential growth medium while Monoraphidium sp. KMC4 showed superior biomass (1.47 ± 0.08 g L-1) and lipid yield (436.01 ± 0.06 mg L-1). The corresponding values for bioremediation of ammonia, nitrate, phosphate, as well as COD remained within 88-100%. CHNS, biochemical, TGA, FTIR, FAME analysis of KMC4 confirmed it's potential as bioenergy feedstock. Additionally, a comprehensive characterization of lipid-extracted microalgae biomass (LEMB) was carried out which suggested that LEMB can be used as a growth promoter as well as feedstock for biogas, bioethanol, and bio-oil production.