• Energy Research
• 2016-2025close

This study investigates temperature and light impact on the ability of Micractinium pusillum microalgae to mitigate CO2 and produce bioenergy in semi-continuous mode. Microalgae were exposed to temperatures (15, 25, and 35 °C) and light intensities (50, 350, and 650 μmol m-2 s-1), including two temperature cycles, 25 °C had the maximum growth rate, with no significant difference at 35 °C and light intensities of 350 and 650 μmol m-2 s-1. 15 °C temperature and 50 μmol m-2 s-1 light intensity reduced growth. Increased light intensity accelerated growth, CO2 utilization with carbon and bioenergy accumulation. Microalgae demonstrate rapid primary metabolic adjustment and acclimation reactions in response to changes in light and temperature conditions. Temperature correlated positively with carbon and nitrogen fixation, CO2 fixation, and carbon accumulation in the biomass, whereas there was no correlation found between light. In the temperature regime experiment, higher light intensity boosted nutrient and CO2 utilization, carbon buildup, and biomass bioenergy.

Abstract In this work, catalytic upgrading was carried out to enhance the yield and quality of castor seed pyrolytic oil. The influence of catalytic vapour cracking of castor seed was performed over Kaolin, CaO and ZnO catalysts at various weight percentage of loading. This study confirmed that the yield varied with catalyst type and its amount of loading. The maximum pyrolysis yield of oil was obtained about 66.4 wt.%, 64.9 wt.% and 65.8 wt.% at 15 wt.% CaO and Kaolin and 10 wt.% ZnO respectively. The effect of catalyst on fuel properties were studied at that catalyst loading where the yield of pyrolytic liquid was higher. The fuel properties of castor seed thermal and catalytic pyrolytic oil were compared. The cracking of castor seed pyrolytic vapour over the bed of catalysts proved to enhance the fuel properties of pyrolytic oil for all catalysts. In comparison with ZnO, CaO and Kaolin found to have significant effect on enhancing the fuel properties in terms of viscosity, pH, calorific value and pour point. It was observed that in catalytic pyrolytic oil the number of acidic groups significantly reduced as they got converted to esters compared to thermal pyrolytic oil. The increase in the formation of nitriles and aromatics content in the catalytic pyrolytic oil was also noticed which were comparatively less in the thermal pyrolytic oil.

The process of combustion and pyrolysis of coal can be considered to be convoluted where numerous intermediates are expected to form during the course of the reaction.

Abstract Thermal pyrolysis of the Cassia siamea seed was carried out in a fixed bed reactor in the temperature range of 450 °C and 575 °C at a heating rate of 50 °C min−1. The reactor was maintained inert using nitrogen gas at a flow rate of 40 mL min−1. It was observed that the highest yield of pyrolytic liquid was 50.21% obtained at 550 °C which includes 39.86 wt% of organic liquid (oil) and 10.35 wt% of aqueous liquid. The fuel properties of pyrolytic oil confirmed that the oil was slightly basic with a pH of 8.75, having viscosity and calorific value of about 373 cSt and 30.18 MJ kg−1 respectively. The GC-MS based composition analysis quantified the occurrence of many valuable bio-chemicals such as heptadecanenitrile, 1,2-benzene dicarboxylic acid, butyl octyl ester, phenol, p-cresol as major compounds.

Developing an efficient photobioreactor (PBR) and reducing freshwater dependence are among the significant challenges for generating 3rd generation biomass feedstock. Addressing these, the present study focused on developing a modified airlift (MoAL) PBR. Its performance was further evaluated and compared with the traditional airlift PBR by cultivating microalgae in dark fermentation spent wash. Lower mixing time and higher interfacial mass transfer coefficient was observed in the MoAL PBR having a perforated draft tube. Experimentally, the MoAL exhibited the maximum biomass concentration of 3.18 g L-1, which was 30% higher than that of the conventional airlift PBR. The semi-continuous operation of the MoAL (with water recycling) achieved the maximum biomass productivity of 0.83 g L-1 d-1, two folds superior to that of batch culture. The comprehensive biomass characterization (proximate, ultimate, and thermochemical) further confirmed its potential for bioenergy application. Considering that, hydrothermal liquefaction of the biomass resulted in a maximum biocrude yield of 31% w/w with a higher heating value (HHV) of 36.6 MJ kg-1. In addition, the biocrude comprised 66.6% w/w lighter fraction (<343 °C), including 21.5% w/w of heavy naphtha, 20.5% w/w of kerosene, and 24.6% w/w of diesel. The results can help develop sustainable technology for simultaneous wastewater remediation and biocrude production.

Abstract Mango ( Mangifera indica ) is one of the popular fruits in India and many other tropical countries also. Mango seed weight is 30 − 45% of the total fruit weight which completely goes off as waste. In this study, Mango seed kernel (MSK) and Mango seed shell (MSS) were selected as a feed for pyrolysis for the production of bio-chemicals. Conventional pyrolysis of MSK and MSS was carried out in the range between 673 to 873 K temperatures at a heating rate of 25 K min −1 . The optimum temperature for maximum yield of pyrolytic liquid was 823 K and 848 K for MSK and MSS with the corresponding yield of pyrolytic liquid of about 32.37% and 52.57% respectively. The composition analysis of MSK and MSS pyrolytic liquid revealed the presence of various valuable chemicals. It was noticed that MSS pyrolytic liquid contains about 27.63% d -allose, which is a rare sugar, whereas MSK contains 13.27% of levoglucosan along with furfural, furan, alcohol, aldehyde, benzene and various alkanes.

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.

Abstract Microalgal biomass as bioenergy feedstock is gaining wide attention for biocrude production through hydrothermal liquefaction (HTL). However, the availability of feedstock in all seasons is a major challenge. Hence, to ensure a consistent supply of feedstock and transform waste to energy, the present study investigates co-HTL of domestic wastewater treatment derived microalgal biomass (Monoraphidium sp. KMC4) and domestic sewage sludge (DSS) as bioenergy feedstocks. The effects of temperature, feedstock ratio, and residence time were studied and optimised for maximum biocrude yield. The study showed that, co-HTL at optimum operating conditions of 325 °C, 75:25 wt% (KMC4:DSS), and 45 min produced 39.38 wt% biocrude yield at a conversion rate of 83.96 wt%. The optimum biocrude yield was 16% and 79% higher than the individual HTL of KMC4 and DSS respectively. The comprehensive characterizations of co-HTL biocrude showed 76.77%, 10.6%, 8.85%, 3.38% of C, H, N, O and 39.47 MJ Kg−1 of HHV with an energy recovery rate of 77.53%. Meanwhile, co-HTL enhanced the distillation profile of biocrude which had 10.13% of heavy naphtha, 23.92% of kerosene, and 27.09% of gas oil. The FTIR and GC–MS analysis confirmed that the co-HTL biocrude had superior hydrocarbons such as alcohols and esters with limited nitrogen and oxygen heterocyclic compounds. In addition, ICP-AES confirmed a significant decrease in transfer of mineral elements from the co-HTL feedstock to biocrude. This validates the sustainability of the co-HTL process to produce high energy density biocrude with the potential to substitute fossil fuels.