• Energy Research
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Abstract Simultaneous production of 3-biofuels (hydrogen, ethanol and methane) as by-products of the biodegradation of petrochemical wastewater containing MEG via anaerobic packed bed baffled reactor (AnPBBR), was extensively investigated. A four-chambered reactor supported by polyurethane sheets, was operated at a constant hydraulic retention time (HRT) of 36 h and different organic loading rates (OLRs) of 0.67, 1, 2 and 4 gCOD/L/d. The maximum specific H 2 and CH 4 production rates of 438.07 ± 43.02 and 237.80 ± 21.67 ml/L/d were respectively achieved at OLR of 4 gCOD/L/d. The residual bio-ethanol significantly increased from 57.15 ± 2.31 to 240.19 ± 34.69 mg/L at increasing the OLR from 0.67 to 4 gCOD/L/d, respectively. The maximum MEG biodegradability of 98% was attained at the lowest OLR. Compartment-wise profiles revealed that the maximum H 2 and ethanol production were achieved at HRT of 9 h (1st compartment), while the CH 4 production was peaked at HRTs of 27 and 36 h (last two compartments). Kinetic studies using Stover–Kincannon and completely stirred tank reactor (CSTR) in series models were successfully applied to the AnPBBR overall and compartment-to-compartment performance, respectively. The economic evaluation strongly revealed the potentials of using AnPBBR for simultaneous treatment and bio-energy production from petrochemical wastewater as compared to the classical anaerobic baffled reactor (ABR). Microbial analysis using Illumina MiSeq sequencing showed a diversity of bacterial community in AnPBBR. Proteobacteria (36.62%), Firmicutes (20.85%) and Bacteroidetes (3.44%) were the most dominant phyla.

Abstract The impact of Ni nanoparticles (NPs) and Ni-graphene nanocomposite (Ni-Gr NC) on hydrogen production from industrial wastewater containing mono-ethylene glycol (MEG) via anaerobic digestion was investigated. Batch reactors were supplemented with different dosages of Ni NPs and Ni-Gr NC ranging from 0 to 100 mg/L. Maximum hydrogen yields (HYs) of 24.73 ± 1.12 and 41.28 ± 1.69 mL/gCOD initial were achieved at a dosage of 60 mg/L for Ni NPs and Ni-Gr NC, respectively. Substantial improvements of 23% and 105% in hydrogen production were registered at an optimum dosage of 60 mg/L for Ni NPs and Ni-Gr NC, respectively, compared with the control without nanomaterials addition. However, increasing the dosage of Ni NPs and Ni-Gr NC to 100 mg/L resulted in a significant decrease in HY to 20.80 ± 1.12 and 24.24 ± 1.13 mL/gCOD initial , respectively. A non-linear regression model revealed that the higher maximum hydrogen production (129% improvement) could be achieved at a dosage of 50 mg/L Ni-Gr NC and an initial pH of 5.0. Economic and environmental revenues due to bioenergy recovery from MEG-containing wastewater were also estimated.

In the present work, theoretical study of the performance evaluation of a continuous water flow inclined solar still desalination system is performed. Three models are studied for inclined solar still desalination system with and without water close loop. The effects of the water mass, water film thickness, water film velocity and air wind velocity on the performance of the three models are studied. The results show that the inclined solar still with a makeup water is superior in productivity (57.2% improvement) compared with a conventional basin-type solar still. Also, the application of inclined solar still with open water loop is recommended when combined with other still desalination system due to high water temperature output. The inclined solar still with a makeup (Model 3) gives the highest performance while Model 1 gives the lowest performance. Finally, the water film thickness, and velocity as well as wind velocity plays important roles in improving the still productivity and efficiency.

Fresh water is the most important source for life on the earth. In the Egyptian deserts and rural areas, there is a shortage of fresh water in spite of the presence of large sources of brackish water. Solar energy is abundant in these remote areas of Egypt, where the amount of sunshine hours is around 3500 h/year. This paper introduces a feasibility study of water desalination in these areas using photovoltaic energy as the primary source of energy. The availability of water resources and solar energy in these areas has been investigated. Also, a design of a PV powered small scale reverse osmosis water desalination system is studied and economically estimated. It is found that the cost of producing 1 m3 of fresh water using the small PV powered RO water desalination systems is 3.73$. This cost is based on using a small system that is operating during the daylight only. If the system size and the daily period of operation are increased, the price of producing fresh water will be decreased in these regions. Also, it is important to mention that using renewable energy sources in feeding different systems in these rural areas with their energy demands will maintain their environment clean and healthy for people.

Abstract As there is a larger need for drinking water, expensive methodologies are employed in order to get portable drinking water. This work aims at improving the yield of freshwater from a conventional solar still using the different low-cost energy storage material. Theoretical and experimental studies are carried out to analyze the performance of a single slope solar still. From this study, it is observed that the yield of freshwater from the solar still with spherical ball salt storage achieves the maximum yield of 3.7 kg/m2 as compared to a conventional single slope solar still with sponge and without any storage material as 2.7 and 2.2 kg/m2 respectively. The deviations between theoretical and experimental values for with spherical ball salt storage, with sponge and conventional solar still are found as 16.1%, 9.7% and 4.0% respectively. Payback period of the present solar still is found as 4.3 months as it is quicker than other conventional single slope solar still. Finally, single slope solar still with spherical ball heat storage gives low cost of water.

Abstract This study investigated the biogas (hydrogen and methane) production and microbial community dynamics in the anaerobic treatment of saline industrial effluents containing mono-ethylene glycol (MEG) as a major pollutant. An immobilized sludge anaerobic baffled reactor (ISABR) inoculated with salt-adapted mixed culture was developed as a lab-scale experiment, and effects of operational conditions (e.g., salinity, organic loading rates (OLRs), and temperature) on the system performance were examined. First, different OLRs of 0.64–2.34 gCOD/L/d, by increasing the initial MEG concentrations at a fixed hydraulic retention time (HRT) of 4.5 d, were examined from day 1 to 100 at lower salinity of 10 gNaCl/L and ambient temperature (25 ± 6 °C). Under such operational conditions, maximum methane yield (MY) of 165 mL CH4/gCODadd and hydrogen yield (HY) of 102 mL H2/gCODadd were achieved at the lowest OLR of 0.64 gCOD/L/d. Afterwards, impacts of higher salinities of 15–25 gNaCl/L were investigated from day 101 to 208 at a controlled mesophilic temperature of 35 °C and fixed OLR (0.64 gCOD/L/d). As a result, enhanced HY and MY (∼2-fold) at elevated salinities up to 25 gNaCl/L were obtained. Moreover, the compartment-wise water and gas analyses, for both experiments, revealed that hydrogen and methane peaked in former and latter compartments, respectively, and the peak location shifted depending on overall imposed OLR. The relative abundance of dominant salt-tolerant bacterial genus Desulfovibrio increased when OLR and operational temperature were increased, while dominant archaeal genera responded substantially when temperature was increased. Economic feasibility of ISABR for bioenergy recovery and treatment of MEG was evaluated by a cost-benefit analysis, suggesting that salinity level along with suitable operational temperature substantially affects the maximum net profit.

Abstract Lignin is the second-most abundant biopolymer on the Earth and it is hard to valorize without pretreatment due to its inherent heterogeneity and recalcitrance. Nowadays, it is necessary to develop effective innovative methods for lignin degradation and efficient utilization. In the present study, the lignolytic bacterium Mycobacterium smegmatis LZ-K2 was isolated from rotten wood. The isolate showed high lipid production and high efficiency of lignin degradation. The lipid production of LZ-K2 grown in corn straw medium with alkali pretreatment, acid pretreatment, and without chemical pretreatment were 0.083 g/L, 0.069 g/L, and 0.072 g/L, respectively. Fatty acids (C14-C24), especially palmitic acid (C16:0; 38.9%), were also accumulated in the untreated corn straw cultures. Results confirmed that the enzyme system and Fenton reaction are the major pathways for lignin depolymerization. In addition, the presence of a critical lignin-degrading enzymes, other than cellulase and hemicellulase, was revealed by the genome analysis. Moreover, the proteome of LZ-K2 showed enzymes, mainly glucose-methanol-choline (GMC) oxidoreductases, which are involved in the Fenton reaction and β-ketoadipate pathway. Unique enzymes of oleaginous microorganisms, such as acetyl CoA carboxylase, were also identified in LZ-K2. In conclusion, the present work provides a sustainable approach for efficient conversion of lignin into biodiesel with simultaneous biological pretreatment of lignocelluloses.

Abstract The present study aimed to evaluate the energy recovery through biodiesel and bioethanol production from Scenedesmus obliquus in a sequential route of lipid extraction followed by fermentation, with recycling of waste glycerol (WG) as a nutrient supplement into the culture. Low WG concentrations significantly enhanced the cellular dry weight over the control, recording the maximum significant value of 3.63 g L−1 using 2.5 g L−1 of WG (WG2.5). In addition, the maximum carbohydrate and lipid contents were recorded in WG2.5, which represented 16.4% and 21.7%, respectively, over the corresponding control, with simultaneous reduction in protein content. Moreover, total fatty acid methyl esters (FAMEs) recovery from biomass increased after WG2.5 supplementation, recording an increase of 24.6% over the control. Fermentation of lipid-free biomass increased the rate of bioethanol production, reaching its peak of 4.82 g L−1 at the 27th day. However, using of WG2.5 for microalgal growth and the residual lipid-free biomass for fermentation showed the highest bioethanol production peak of 5.58 g L−1 at day 27. Due to the accumulation of carbohydrates under WG, the biomass treated with WG2.5 showed increase in maximum bioethanol productivity up to 0.185 g L−1 h−1. However, sequential fermentation after lipid extraction enhanced the maximum bioethanol productivity by 32.3% and 15.1% over the whole cells from synthetic wastewater (WW) and lipid-free biomass from WW, respectively. The highest gross energy output of 21.4 GJ ton−1 dry microalgae was estimated from the integrated route where S. obliquus was grown in WG-enriched medium and sequential fermentation was applied for the residual biomass after lipid extraction, with the highest recorded energy conversion efficiency of 62.9%. These findings provide an innovative practical integrated approach for waste recycling and high conversion efficiency of microalgal biomass for liquid biofuel production.

Abstract In this paper, a novel integrated energy system driven by solar power is proposed. A concentrated solar trough system is utilized in integration with organic Rankine cycle, absorption cooling system, desalination unit and electrolyzer, for the purpose of polygeneration. The proposed system produces hydrogen, cooling, fresh water, and domestic hot water along with electric power production. The system is analyzed thermodynamically, and its overall performance is assessed through energy and exergy efficiencies. The effects of varying several operating parameters and conditions on the performance are investigated through parametric studies. The cost rate is estimated at different operating points. The overall thermoeconomic multi-objective optimization study shows two extremes of 39% and 21.7% as maximum and minimum overall exergy efficiencies, respectively, as achieved at cost rate of 309.56 $/h and 241.7 $/h, for each corresponding case, respectively.