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Biodiesel production had received a considerable attention as a green, non-toxic and renewable alternative to petroleum diesel. To avoid using vegetable oils, which are expensive and compete with food, as feedstock, waste oils have been proposed. However, these waste materials contain a large amount of free fatty acids that complicates the production process. In this work, biodiesel production using an alternative feedstock; namely oils from date-pits, has been investigated. These oils have the same favorable features of straight oils, and at the same time are considered waste, since they are extracted from a waste material. The yield of oils extracted using n-hexane in a Soxhlet apparatus was compared to that of oils extracted using methanol-chloroform solvent mixture. The extracted oils were then converted to biodiesel via transesterification with methanol in presence of Novozym&#174435 or Eversa&#174Transform. The highest oils extraction yield of 11.7%, per dry weight sample, was obtained using Soxhlet extraction apparatus compared to 8.9% using methanol-chloroform mixture. The highest biodiesel production yield was 30% of the oil used, achieved after 6 hours using Novozym&#174435 at 40°C, 5:1 methanol to oil molar ratio and 10wt% enzyme loading. By using a chemical alkaline catalyst, NaOH, at the same conditions, the yield was 27%.

Microalgae are considered a promising source of oil for biodiesel production. This work reports an estimation method of oil content inside living microalgal cells by visualization and image processing techniques. This approach was used to analyze the time course of oil accumulation patterns in Nile Red-stained microalgal cells of Scenedesmus sp. cultivated in nitrogen-deficient medium used to induce oil accumulation in microalgal cells. Nile Red staining is a widely used technique for studying oil content of microalgal cells. The intracellular oil content was estimated by mathematically evaluating the oil volume inside the stained cell. This novel visualization approach has the potential to be used in ex vivo studies of oil content at the level of single microalgal cells. This method can also be applied to other types of oil-producing microorganisms because of its accuracy, precision, and reduction in the time and effort required for optimization.

Biodiesel produced from oil-rich feedstocks is known as a green replacement for conventional petroleum diesel. Transesterification is the common method used for biodiesel production. The enzymatic biodiesel production, using lipases, has recently been receiving extensive attention, due to its advantages over conventional alkali catalyzed process. The lipases can work at mild operating conditions, thus requiring less energy, with the ability to catalyze both triglycerides and free fatty acids (FFAs) from different oil sources, requiring fewer post-production steps. Among the process challenges that face this process is the inhibition of the lipase with excessive use of alcohols, resulting in a decrease in biodiesel yield. The use of organic solvents, as a reaction medium, becomes essential in this case. However, most organic solvents are toxic and volatile with harmful impacts on the environmental. In addition, with the use of volatile organic solvents, an additional unit is required to separate them from the products, for the purification of the product and recycling of the solvent. In this paper, the prospect of using alternative solvents, specifically supercritical carbon dioxide (SC-CO2) and ionic liquids (ILs), in enzymatic biodiesel production is presented. The properties of these alternative solvents, their advantages over organic solvents, factors affecting lipases activity and stability in these solvents, and the challenges facing process commercialization are discussed. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Steam reforming of commercially available LPG using Ru/Al2O3 and Ni/Al2O3 catalysts has been studied at temperatures between 573 and 773 K. Ru/Al2O3 catalyst showed higher rates of reaction and lower activation energies of the three main components of LPG, compared with Ni/Al2O3. However, Ni/Al2O3 catalyst showed a better H2:CH4 selectivity. The activation energy of n-butane was the lowest over Ru/Al2O3, whereas over Ni/Al2O3, propane had the lowest activation energy. The activation energy of i-butane was always the highest over both catalysts, which suggests that both catalysts performed better with unbranched molecules. A slight increase in activation energy was observed, when each component of the LPG mixture was studied separately as a pure gas, compared with being mixed in LPG. At a constant temperature of 773 K, hydrogen production yield and H2:CH4 selectivity were determined using Ru/Al2O3 at different steam:carbon (S:C) ratios and LPG flow rates. It was found that the yield and selectivity increas...

Crude proteins and pigments were extracted from different microalgae strains, both marine and freshwater. The effectiveness of enzymatic pre‐treatment prior to protein extraction was evaluated and compared to conventional techniques, including ultrasonication and high‐pressure water extraction. Enzymatic pre‐treatment was chosen as it could be carried out at mild shear conditions and does not subject the proteins to high temperatures, as with the ultrasonication approach. Using enzymatic pre‐treatment, the extracted proteins yields of all tested microalgae strains were approximately 0.7 mg per mg of dry cell weight. These values were comparable to those achieved using a commercial lytic kit. Ultrasonication was not very effective for proteins extraction from Chlorella sp., and the extracted proteins yields did not exceed 0.4 mg per mg of dry cell weight. For other strains, similar yields were achieved by both treatment methods. The time‐course effect of enzymatic incubation on the proteins extraction efficiency was more evident using laccase compared to lysozyme, which suggested that the former enzyme has a slower rate of cell disruption. The crude extracted proteins were fractionated using an ion exchange resin and were analyzed by the electrophoresis technique. They were further tested for their antioxidant activity, the highest of which was about 60% from Nannochloropsis sp. The total phenolic contents in the selected strains were also determined, with Chlorella sp. showing the highest content reaching 17 mg/g. Lysozyme was also found to enhance the extraction of pigments, with Chlorella sp. showing the highest pigments contents of 16.02, 4.59 and 5.22 mg/g of chlorophyll a, chlorophyll b and total carotenoids, respectively.

The ability of three freshwater microalgae strains, namely Chlorella sp. , Pseudochlorococcum sp . and Chlamydomonas sp. to grow in water containing different concentrations of phenol has been tested. The effectiveness of the selected strains to utilize the phenol as a carbon source and reduce its concentration has also been assessed. The phenol removal efficiency and cells growth rates were evaluated at different initial phenol concentrations, in the range of 100-450 ppm. It was found that growing, under a reduced illumination condition, increased the inhibition onset concentration, enhanced the phenol removal and allowed the strains to tolerate higher phenol concentrations reaching 450 ppm. In the tested range of the phenol concentrations, Chlamydomonas sp . has shown to have the highest specific growth rate of 0.59 day -1 , whereas Pseudochlorococcum sp showed the highest phenol removal rate of 166 ppm day -1 . Three kinetics models that incorporate substrate inhibition were tested to describe the growth, which show almost identical fittings.

The growing demand for dates, as food, has enhanced its production and increased the total amount of date pits waste. Subcritical water extraction (SCWE) can be used to effectively extract valuable products from date pits. This study was to extract phenolic compounds, total flavonoid content, antioxidants, and dietary fibres from the date seeds using SCWE. The effects of process variables such as feed mixture concentration (x), extraction temperature (T), and extraction time (t) on the yields of total phenolic content (TPC), total flavonoid content (TFC), antioxidants, and dietary fibres were investigated for process optimisation using desirability approach. The results showed that extraction temperature could significantly increase TPC, TFC, and dietary fibres extraction yields, but has less effect on the antioxidant extraction. The feed mixture concentration has shown a significant effect on antioxidant extraction but was insignificant on TPC, TFC, and dietary fibres extractions. The desirability approach of process optimisation validated the feasibility of using SCWE for valuable products extraction from date pits.

The seeds of a local date palm cultivar from the United Arab Emirates, Allig, were characterized in this study. Soxhlet, Folch, and CO2 supercritical extraction were employed to obtain oil from Allig date seed (DS) powder composed of 0.1–0.3 mm particles, yielding oil extraction yield percentages of 10.2%, 9.5%, and 9.8%, respectively. The main fatty acid in the extracted oil was saturated stearic acid, comprising 47.9% of the total fatty acid content. After oil extraction, the total metal content in the DSs dropped from 3.2% to 2.8%, suggesting that some metals were extracted with the oil. On the other hand, the average heating value of the DSs increased from 28.55 ± 1.84 to 29.63 ± 1.28 MJ/kg after oil extraction. The average percentages of dehydration moisture, devitalization protein and carbohydrates, devitalization lipids, and solid decomposition in the DSs before oil extraction were 1–2%, 50–55%, 10–15%, and 30–35%, respectively, whereas those for the DSs after oil extraction were 20–25%, 35–30%, 0%, and 35–40%, respectively. As expected, the lipid content dropped after oil extraction. The heat of combustion and extracted oil results indicate that palm DSs, with their relatively high energy densities, have potential as a source of energy, among other notable organic products.

Green building regulations in the United Arab Emirates are required to obtain building permits so that future construction projects can create a sustainable living environment. Emirates such as Abu Dhabi, Dubai, and Sharjah have specific green building regulations, whereas other emirates follow Abu Dhabi&rsquo, s regulatory criteria. Previous work fails to present a techno-economic cross-code analysis for various green building regulations in the UAE by evaluating energy and water performance. A case study using an existing high-rise green office building was formulated using the Integrated Environmental Solution: Virtual Environment (IES-VE) platform and the U.S. Leadership in Energy and Environmental Design (U.S. LEED) water consumption evaluation tool to study its energy and water performance, respectively. The archived results were used to devise an economic study based on the discounted cash flow technique. The principal findings of this research allowed us to determine a cross-code analysis and propose cost-effective trade-offs. These will aid the consultants and contractors in choosing appropriate green building regulations in the UAE by highlighting the potential of each parameter within green building regulations in terms of energy, water, and economic performance.

A thermo-responsive switchable solvent (TSS), which switched hydrophobicity by the change in temperature, was successfully used for simultaneous cell disruption, oil extraction-reaction, and biodiesel separation from wet microalgae. Catalyzed by immobilized lipase, the entire process was carried out in a single pot using the same solvent without drying the microalgae. Besides being easier to operate, the biodiesel yield using the TSS was 21% higher than that achieved using CO2-triggered switchable solvent under the same conditions and solvent switching program. To optimize the process, a parametric study was performed to evaluate the effects of cell disruption and extraction/reaction durations and methanol amount on the biodiesel production yield. The results were used to develop a statistical model to predict the biodiesel yield under different conditions. The model was validated by repeating the reaction as defined by the model and a yield of 75.11 ± 1.03% was observed. Moreover, we observed that the immobilized enzyme retained its activity till two rounds of reaction, and future optimization may improve the reusability further. In conclusion, our results showed that the successful use of a TSS lipids extraction-reaction from wet biomass can significantly simplify the biodiesel production from wet microalgae.

The kinetics of adsorption of ethyl mercaptan, found in commercially available LPG, on different adsorbents, namely Zeolite, ZnO and house made date pits activated carbon (DP-AC) have been studied. The bed capacity was determined using two adsorbents weights, namely 0.2 and 0.3 g, at different LPG flow rates in the range of 35 to 90 ml min-1. It was found that the capacity of DP-AC and Zeolite did not change with the flow rate due to their much larger micropore volumes and smaller average pores sizes, compared to ZnO. The capacity of DP-AC did not even change with the amount of adsorbate used. Two kinetics models, namely Adam's-Bohart and Yoon-Nelson, were used to fit the experimental data and compared to the first order model. The first order and Adam's-Bohart models did not present the experimental data fairly well, and only the Yoon-Nelson model was able to mimic the sigmoidal trend of the breakthrough curves. The goodness of the fitting of the Yoon-Nelson model was also reflected on the values of the coefficient of determination R2, which was much closer to 1.0 compared to that of the other model. The developed models can be used in designing and scaling-up of fixed-bed adsorption columns.

The optimum conditions for lipids productivity and CO2 fixation of two freshwater strains, namely Chlorella sp. and Pseudochlorococcum sp. and a marine strain; namely Nannochlorpsis sp. have been determined in this work. The species were grown autotrophically under aeration with different CO2 concentrations, ranging from 0.04 to 2% (v/v). The growth was tested in nitrogen sufficient and deficient media at different salinities (0.49–680 mM) and temperatures of 27 and 31 °C. The optimum CO2 enrichment was found to be 1% (v/v) in both media. Nitrogen starvation resulted in an increase in lipid contents, but at lower growth rate, which resulted in a lower overall lipid productivity. The experimental data were used to determine the kinetic parameters of Haldane model. The Chlorella sp. grew well at salinity levels of up to 460 mM. The highest CO2 biofixation rate was observed when Chlorella sp. was grown at 27 °C in seawater (230 mM NaCl). Lipids were extracted from harvested marine strain, Nannochlorpsis sp., and enzymatically transesterified to produce biodiesel in supercritical CO2 (SC–CO2) medium. It was found that the conversion of biodiesel produced from microalgae lipids was 35% higher than that achieved using lamb fat in a similar system.

The adsorption of sulfur compounds, in commercially available LPG, has been studied using different adsorbents, namely Zeolite, ZnO and house made date pits activated carbon (DP-AC). It was found that the three adsorbents are capable of effectively removing sulfur compounds at different feed sulfur concentrations. The effects of height to diameter aspect ratio of the adsorption column, flow rate of LPG and input sulfur concentrations have been studied. A first order kinetics model has been used to describe the adsorption, and the kinetics constant was found to increase by increasing the flow rate of LPG and decrease by increasing the amount of adsorbent used. The developed model described the system fairly well, and can be used in designing and scaling-up of fixed-bed adsorption columns.

The United Arab Emirates (UAE) has more than 40 million palm trees producing approximately 15 kg of waste fronds per tree. These fronds contain a large portion of polysaccharides, which can be hydrolyzed to simple fermentable sugars. Seaweed consists of macroalgae containing high portions of polysaccharides, which are also abundantly found on the coasts of UAE. The effectiveness of lignin to degrade enzymes for the pretreatment of biomass from palm trees fronds and indigenous seaweed (prior to enzymatic hydrolysis) has been investigated and compared to conventional chemical treatment. By treating with laccase, up to 9 and 24 % additional lignin was removed from palm fronds and seaweed, respectively. The performance of laccase was enhanced by using an ionic liquid, and a sugar yield of 12.6 % was achieved after treatment with laccase for only 1 hour. The proposed approach provides a promising simplification to the overall bioethanol production from biomass waste available globally in abundance, and in the UAE in particular.

The economic and environmental impacts of a commercial biodiesel production process using supercritical CO2 in lipid extraction and enzymatic transesterification from freeze-dried Nannochloropsis gaditana were assessed. The results were compared with those of compressed natural gas (CNG), which is employed as a transportation fuel in the United Arab Emirates (UAE). The total operation time considered in the techno-economic and environmental impact assessments was 16 years. To produce 1000 ton/y of biodiesel, the manufacturing costs and revenue were estimated to be $21,843,000/y and $27,940,000/y, respectively. The net present value of the profit, payback period, discounted payback period, and internal rate of return were estimated to be $8.31 million, 9 years, 13 years, and 10.5%, respectively. An economic assessment indicated that producing biodiesel using the supercritical CO2 approach is profitable. Although the economics of CNG appeared more attractive, owing to the lower selling price and better consumption economy, the environmental impact of biodiesel production through supercritical CO2 was 8 times smaller than that of CNG production. Reusing the produced biodiesel as an energy source in the production process and choosing a location close to the material source and capital items could further improve the economics and environmental impacts of the process.

Mathematical modeling of supercritical extraction of lipids from Scenedesmus sp. microalgae is presented in this study. Broken and intact cells (BIC) model, proposed by Sovova in 1994, was used to predict the extraction curves. The effects of extraction pressure, temperature and fluid flowrate on predicted model parameters and extraction rates were assessed. The results indicates that BIC model represents well the experimental data, and the mass transfer coefficients in the fluid and solid phases changed in ranges of 6.7–30.9 × 10−6 m s−1 and 2.08–13.2 × 10−10 m s−1, respectively. The fluid phase coefficient increased with increasing the flowrate and temperature, but was not affected by the pressure, whereas the solid phase showed a significant decrease with the increase in pressure. According to the external mass transfer coefficient, mass transfer correlations were developed to relate Sherwood number to Reynolds, Schmidt, and Grashof numbers. It was found that when Schmidt exponent was fixed at 1/3 (model 1), the model did not fit the experimental data well, whereas when the power was adjusted and considered as a fitting parameter the coefficients of determination increased significantly exceeding 90%. The natural convection effect was found to be insignificant compared to the forced convection. The validity of the developed correlations with coefficients determined from experimental data collected from a small scale extraction cell was confirmed by predicting the overall extraction curve (OEC's) of a larger scale extraction cell.

Enzymatic biodiesel production in supercritical CO 2 (SC-CO 2 ) has recently received an increasing attention, as an alternative to the conventional chemical processes. In this study, enzymatic production of biodiesel from microalgal lipids was investigated in batch and integrated extraction-reaction systems. In the batch system, the effect of enzyme loading (15–50 wt%), temperature (35–55 °C) and methanol to lipid molar ratios (3–15:1) were studied, and response surface methodology was employed to optimize selected factors effect. The optimum transesterification yield of 80% was obtained at 47 °C, 200 bar, 35% enzyme loading, and 9:1 molar ratio after 4 h reaction in the batch system. The experimental results were also used to determine the kinetics parameters of the Ping-Pong Bi Bi model, with methanol inhibition, suggested to describe the reaction. In the continuous integrated extraction-reaction system, the effect of methanol to lipids molar ratio was investigated, and enzyme operational stability and reusability were tested. Bed regeneration by tert -butanol washing was also assessed. The optimum methanol to lipid ratio was found to be 10:1. At this ratio, the enzyme was able to attain 78% of its original activity when reused for 6 continuous cycles, and the bed was successfully reused by washing with tert -butanol.

Plasma gasification can be a viable technology for converting municipal solid waste (MSW) into value for the circular economy. However, in its current state, plasma gasification is mostly limited to lab or pilot scales as there are various challenges associated with it; there exist knowledge gaps which need attention and research for its successful future commercialisation. The present study critically reviewed the current status of plasma gasification for waste-to-value processing. Various traditional techniques for MSW disposal and processing available in the literature were discussed and were compared with plasma gasification in terms of cost, service life, energy comparison, and environmental impact comparison. After the review, knowledge gaps were identified, challenges associated with the plasma gasification technology were discussed, and a possible roadmap for the successful future commercialisation of plasma gasification for waste-to-value processing was suggested. Furthermore, various strategies to cope with challenges associated with plasma gasification were discussed. The successful commercialisation of plasma gasification can be achieved by reducing its costs by generating revenue or value in the form of synthesis gas or fuels from MSW, energy can be saved or reused using insulation, process integration, and process intensification, the technology and community readiness levels can be improved with better communication between relevant stakeholders and adding extra layers of safety, and process understanding can be improved by conducting extensive fundamental studies, as well as plasma gasification technology being standardised by establishing standards and standards organisations.

In this study, a novel three-step process was developed and evaluated for the treatment of highly contaminated refinery wastewater. The process consisted of an electrocoagulation cell (EC), a spouted bed bioreactor (SBBR) with Pseudonymous putida immobilized in polyvinyl alcohol gel, and an adsorption column packed with granular activated carbon produced from agricultural waste, specifically date pits. The units were evaluated individually and as combinations with different arrangements at different operating conditions to treat refinery wastewater with varying levels of contaminants. The EC unit was found to be effective as a pretreatment step to reduce the large concentrations of COD and suspended solid and reduce the load on the bioreactor and the adsorption column. At optimum conditions and unit arrangement, the process was able to reduce the concentration of COD, phenol and cresols by 97%, 100% and 100%, respectively. The process was found to be highly competitive in comparison with other combined systems used in the treatment of industrial wastewater and can handle highly contaminated refinery or industrial wastewater with relatively wide range of operating conditions.

Supercritical carbon dioxide (SC-CO 2 ) extraction of lipid from Scenedesmus sp. for biodiesel production was investigated and compared to conventional extraction methods. The effect of biomass pre-treatment prior to extraction and extracting conditions, namely pressure in the range of 200–500 bar, temperatures in the range of 35–65 °C and CO 2 flow rate in the range of 1.38–4.02 g min −1 , on SC-CO 2 extraction yield and quality of lipid were investigated. Three levels full factorial design of experiments and response surface methodology was used to model the system. A second order polynomial model was developed and used to predict the optimum conditions. Scaling up to a laboratory larger scale was also tested. The results indicated that SC-CO 2 extraction was superior to other extraction techniques, but exhibited significant variations in yield with changes in operating parameters. In the developed model, it was found that the linear and quadratic terms of the temperature, as well as the interaction with pressure had a significant effect on lipid yield; whereas, their effect on lipid quality was insignificant. The best operating conditions, in the tested range, were 53 °C, 500 bar and 1.9 g min −1 , in which lipid extraction yield of 7.41% (dry weight basis) was obtained. Negligible differences were observed when the fatty acid composition of SC-CO 2 extracted lipid was compared to that extracted by the conventional methods. At the optimum conditions, SC-CO 2 extraction was successfully scaled-up by eight-folds and the extracted lipid yield dropped by 16%.

Cellulose hydrolysis is an important step in the production of bioethanol from lignocellulose. Using enzymes, as a biocatalyst, is expected to have a lower utility cost compared to the conventional acidic hydrolysis because it is carried out at milder conditions and does not require subsequent treatment step. The major obstacle to the practical realization of the potentials of enzymatic hydrolysis is the high cost of the enzymes and the slow reaction rate due to the inhibition of the enzyme by the products. In this work, a membrane bioreactor was simulated to tackle these two obstacles and enhance the reaction rate. It was found that for a 5000 kg h−1 lignocellulosic feed, to achieve 50% hydrolysis conversion, a 125 m3 membrane bioreactor containing 923 kg m−3 cellulase need to be used. The amount of the enzyme that escapes from the system and needs replacement was estimated at 92 kg h−1. The membrane reactor model was further tested using the competitive product inhibition model for the hydrolysis of totally amorphous Carboxymethylcellulose (CMC). It was shown that the reactor volume required to achieve a conversion of 50% was significantly less than that required for the lignocelluloses, even at a lower membrane mass transfer coefficient.

The performance of an adsorption column packed with granular activated carbon was evaluated for the removal of phenols from refinery wastewater. The effects of phenol feed concentration (80–182 mg/l), feed flow rate (5–20 ml/min), and activated carbon packing mass (5–15 g) on the breakthrough characteristics of the adsorption system were determined. The continuous adsorption process was simulated using batch data and the parameters for a new empirical model were determined. Different dynamic models such as Adams–Bohart, Wolborsko, Thomas, and Yoon-Nelson models were also fitted to the experimental data for the sake of comparison. The empirical, Yoon–Nelson and Thomas models showed a high degree of fitting at different operation conditions, with the empirical model giving the best fit based on the Akaike information criterion (AIC). At an initial phenol concentration of 175 mg/l, packing mass of 10 g, a flow rate of 10 ml/min and a temperature of 25 °C, the SSE of the new empirical and Thomas models were identical (248.35) and very close to that of the Yoon–Nelson model (259.49). The values were significantly lower than that of the Adams–Bohart model, which was determined to be 19,358.48. The superiority of the new empirical model and the Thomas model was also confirmed from the values of the R 2 and AIC, which were 0.99 and 38.3, respectively, compared to 0.92 and 86.2 for Adams–Bohart model.

A three-step pilot plant was designed, fabricated and tested for the treatment of highly contaminated petroleum refinery wastewater. The three-step process consisted of an electrocoagulation (EC) unit, a biological treatment in a spouted bed bioreactor (SBBR) using immobilized Pseudomonas putida in PVA particles, and an adsorption process using granular activated carbon in a packed column. The pilot plant was operated for a period of ten months at a flow rate of 1m3/h, with continuous runs lasting up to 12h. Different arrangements of the three units were tested to determine the most effective sequence. Placing the EC unit as the pretreatment step resulted in the best performance, since it reduced the COD and suspended solids, and consequently enhanced the performance of the succeeding biodegradation and adsorption units. At the optimum conditions and unit arrangement, the pilot plant was able to reduce the COD by 96% and the concentrations of phenol and cresols by nearly 100%. Japan Cooperation Centre, Petroleum (JCCP)

High quality transformer oil is required to increase the reliability and the life time of the transformer. This oil carries information about the operating condition of the transformer. Therefore, the transformer oil properties should be monitored in order to give early warnings and maintain the transformers efficiency. When the oil quality is decreased, it should be either changed or regenerated. Transformer oil regeneration was carried out using adsorption on Activated Carbon (AC) produced from waste date-pits. After adsorption, drop in density, viscosity, neutralization index and metallic contents were observed, whereas adsorption resulted in an increase in interfacial tension. The properties of the regenerated oil after adsorption was found to approach the acceptable standards, which clearly demonstrate the potential of using locally made AC from waste date-pits as an adsorption agent for transformer oil regeneration.

Phenol-degrading bacterial strains have been extracted from oil-sludge samples collected from a local refinery. A selective medium was used to isolate the active strain capable of utilizing phenol as a sole carbon source, which was identified as Ralstonia pickettii. The growth kinetics of mixed and isolated R. pickettii suspensions were investigated using different initial concentrations of phenol in the range of 25 to 200 g m−3 at 35°C and pH of 8.5. The results were compared to those of a commercially available mixed bacterial suspension, which was either acclimatized to 100 g m−3 phenol concentration, extracted from PVA particles that were subjected to real petroleum refinery wastewater containing phenol, or an isolated active strain grown on a selective medium that was identified as Pseudomonas putida. The effect of substrate inhibition was observed using all bacterial suspensions, and the growth results were used to determine the parameters of a suitable kinetic model. It was found that the phenol bi...

Waste animal fat is considered a promising cheap alternative feedstock for biodiesel production that does not compete with food stock. In addition, using waste animal fat as a feedstock is considered a waste management process. In this work, an integrated process for a continuous fat extraction from lamb meat followed by enzymatic production of biodiesel in supercritical CO2 has been developed and tested. The system simultaneously produces two valuable products, namely biodiesel and healthy low-fat lean lamb meat (HLFLM). For the enzymatic process to be feasible, lipase is preferred to be used in immobilized form, which allows easy reuse. The continuous system was operated at 200 bar and a SC-CO2 flow of 0.5 ml min−1, with extraction and transesterification temperatures of 45 °C and 50 °C, respectively. The effects of methanol:fat (M:F) molar ratio and enzyme stability were investigated. It was found that with fresh enzyme, a M:F molar ratio of 10:1 gave the highest biodiesel production rate of 0.37 mg min−1 g-enzyme−1 compared to only 0.09 mg min−1 g-enzyme−1 using a M:F molar ratio of 5:1. However, when a M:F molar ratio of 10:1 was used, the activity of the enzyme in the third meat replacement cycle drastically dropped to 18% of its original value, compared to 79% using a M:F molar ratio of 5:1.

In this work, a proposed pilot plant has been designed to produce 1 ton h−1 biodiesel (BD) from waste/used vegetable oil using enzymatic approach. Complete material and energy balances were carried out using Excel spreadsheets, and detailed equipment sizing were determined. Immobilized lipase (Novozyme 435) is used as a catalyst in a packed bed bioreactor. The effluent of the reactor is passed though a Liquid–liquid extractor to separate the BD from other components. This is followed by a flash dram and a vacuum distillation column for further purification of the product. In addition, an economic feasibility of this process was assessed. The amount of feed streams of waste oil, methanol and tert-butanol required were found to be 1138, 130 and 7.6 kg h−1, respectively. The main units in the proposed plant were designed and the economic feasibility of the process was assessed. It was found that the total capital investment required is about US$ 620,000, which will be paid back within four years of operation.

Pseudomonas putida, immobilized in polyvinyl alcohol (PVA) particles, has been successfully utilized for the bioremoval of phenol from simulated wastewater, using two immobilization techniques and two types of bioreactors. The biodegradation efficiency of P. putida immobilized within the PVA gel before the cross-linking stage of the polymer (T1) was compared to that of the same bacteria immobilized by soaking blank PVA particles in bacterial suspension (T2), a procedure that avoids subjecting the bacteria to sub-freezing temperature during the cross-linking stage. The effects of nutrient deprivation and exposure to high phenol concentrations on the activity of P. putida were also evaluated. The experimental results indicated that the immobilized bacteria remained active for a period of 72 h, even without the addition of nutrients. Subsequently the activity gradually decreased, but the bacteria easily regained their original activity with the addition of nutrients. Sudden exposure to high phenol concentrations resulted in immediate decline in the biodegradation activity, but the bacteria adapted to the new concentrations and regained their activity within 24 h. The biodegradation experiments were carried out in two types of bioreactors namely, bubble column and spouted bed bioreactor (SBBR). Both reactor configurations and both immobilization techniques proved to be effective in the biodegradation of phenol.

The feasibility of enzymatic production of biodiesel from waste animal fats using supercritical fluid technology for the extraction and reaction has been investigated. The operating conditions that resulted in the optimum extraction and biodiesel production yields were identified. The effects of extraction temperature, pressure and supercritical CO2 (SC-CO2) flow rate were investigated in the ranges of 35–55 °C, 300–500 bar and of 3–5 ml min−1, respectively, and optimized using response surface methodology (RSM). In addition, the effects of reaction temperature, methanol:fat molar ratio and enzyme loading on biodiesel production yield were investigated in the ranges of 35–60 °C, 3:1–6:1 and 10–50%, respectively. The optimum conditions for supercritical fluid extraction (SFE) were determined to be 45 °C, 500 bar and 3 ml min−1; at which, 87.4% of total fat content was extracted from freeze dried meat. The statistical analysis however, showed that pressure has negligible effect on the extraction yield, which is extremely important, as it allows saving energy by using lower pressure. On the other hand, biodiesel yield of 40% was obtained using extracted fat as feedstock in SC-CO2 medium at 50 °C, 200 bar, 4:1 methanol:fat molar ratio and 30% loading of lipase enzyme, after 24 h of reaction. The experimental results were used to fit a suitable reaction kinetic model using non-linear regression analysis to estimate the model parameters.

Experiments were carried out to evaluate the batch adsorption of phenol from petroleum refinery wastewater on a locally prepared date-pit activated carbon (DP-AC). Adsorption equilibrium and kinetics data were determined for the uptake of phenol from real refinery wastewater and from synthetically prepared aqueous phenol solution. The data were fitted to several adsorption isotherm and kinetics models. Sips as well as Langmuir models gave the best fit for equilibrium isotherms, whereas the kinetics data were best fitted by the pseudo-second order model. The enthalpy of adsorption showed an exothermic nature of the adsorption process. Several chemical and thermal techniques were tested for the regeneration of saturated activated carbon; using ethanol was found to be the most effective with more than 86% regeneration efficiency after four regeneration cycles.

Experiments were carried out to evaluate the continuous biodegradation of phenol using Pseudomonas putida, immobilized in polyvinyl alcohol (PVA) gel matrices in a specially designed spouted bed bioreactor (SBBR) at different conditions. The plexiglas reactor had a total volume of 1.1 l and was equipped with a surrounding jacket for temperature control. The mean residence time in the SBBR was determined experimentally by tracking the concentration of a tracer compound in a continuous effluent stream. The effects of initial phenol concentration, air flow rate, liquid flow rate and PVA particle size, on the rate of phenol biodegradation, were investigated. It was found that the rate of continuous biodegradation increased with increasing the initial phenol concentration and decreased with increasing the liquid flow rate. Mass transfer and hence the accessibility of the biomass to phenol was enhanced by decreasing the PVA particle size and increasing the air flow rate, which had a positive effect on the rate of biodegradation.

Bacterial biotreatment has gained a lot of attention in recent years as an alternative method for the removal of phenol from wastewater. Under aerobic conditions, Pseudomonas putida utilize phenol as a source of carbon and energy. In this work, P. putida was immobilized in Polyvinyl Alcohol (PVA) gel particles and used in a spouted bed bioreactor to remove phenol from wastewater. The effects of initial phenol concentration and air flow rate on the rate of aerobic phenol removal were investigated. The experimental results were used to develop a dynamic model to describe the utilization of phenol for the bacterial growth in spouted bed bioreactor.

Batch electrocoagulation experiments were carried out to evaluate the removal of sulfate and COD from petroleum refinery wastewater using three types of electrodes: aluminum, stainless steel, and iron. The effects of current density, electrode arrangement, electrolysis time, initial pH, and temperature were investigated for two wastewater samples with different concentrations of COD and sulfate. The experimental results indicated that the utilization of aluminum, as anode and cathode, was by far the most efficient arrangement in the reduction of both the contaminants. The treatment process was found to be largely affected by the current density and the initial composition of the wastewater. Although electrocoagulation was found to be most effective at 25 degrees C and a pH of 8, the influence of these two parameters on the removal rate was not significant. The results demonstrated the technical feasibility of electrocoagulation as a possible and reliable technique for the pretreatment of heavily contaminated petroleum refinery wastewater.

The effectiveness of lipase immobilized on ceramic beads, in the production of biodiesel from simulated waste cooking oil in organic solvent system, was compared to that of free lipase. Experimental determination of the effect of concentrations of methanol on the rate of the enzymatic transesterification was experimentally determined. In addition, the effectiveness of lipases from bacterial and yeast sources for biodiesel production from simulated waste cooking oil was compared. A kinetic model was developed to describe the system, taking into consideration the mass transfer resistances of the reactants. Inhibition effects by both substrates on the interfacial reaction were also considered. The experimental results were used to determine the kinetic parameters of the proposed model and to determine the effect of mass transfer. On the other hand, it was shown that biodieasel can be produced in considerable amounts, with yield reaching 40%, in absence of organic solvent using immobilized lipase from P. cepacia on ceramic beads.

This paper presents the development and application of a simple, yet reasonably accurate, method for predicting gas well performance. The proposed approach is based on predicting average reservoir pressure at different time intervals from stabilized surface production-history data using an iterative mode of calculations. The calculated (P r /z) values are then plotted versus cumulative gas production (G p ) and the straight line which best fits the data points can then be reasonably projected into any future stage of depletion to predict the remaining reserves. The present technique is suitable whenever the loss of cash flow due to shut-in production and/or the use of special sensing down-hole equipment become prohibitive, particularly when H 2 S and CO 2 are present in the produced gas mixture. Dry gas wells, wet gas wells, and condensate gas wells can be treated with the proposed technique. All calculations are performed with Excel spread sheet solver and flow diagrams of these calculations are included in this paper.

The applications of lipase immobilized on ceramic beads and entrapped in sol-gel matrix, in the production of bio-diesel from waste cooking oil, are compared to that of free lipase. Experimental determination of the effect of molar equivalent of methanol, to moles of ester bond in the triglyceride, on the rate of the enzymatic trans-esterification was experimentally determined. It was found that for the same weight of lipase used, the production of bio-diesel was much higher using lipase immobilized on ceramic beads in comparison to that using lipase entrapped in sol-gel and in free form. Substrates inhibition effect was observed in all cases, which agrees with previous results found in literature. The optimum methanol:oil molar ratio was found to be 0.87 for immobilized lipase from yeast source, C. antartica and 1.00 for free lipase from the same yeast source and immobilized lipase from bacterial source, P. cepacia. On the other hand, it was shown that biodieasel can be produced in considerable amounts, with yield reaching 40%, in absence of organic solvent using immobilized lipase, from P. cepacia, on ceramic beads. The results of this study can be used to determine the kinetics parameters of mathematical models which describe the system.

Lipase catalysed reactions take place at the interface between the aqueous phase containing the enzyme and the oil phase. The reaction starts with the adsorption of the enzyme at the oil-water interface. In a mechanically agitated reactor, the total free interfacial area is limited and hence, there would be a critical enzyme concentration at which the interfacial area is saturated with the adsorbed enzyme. In this paper, an unsteady-state dynamic model is developed from Ping Pong Bi Bi mechanism, modified to take into consideration the effect of available interfacial area. The model is validated against experimental results from the hydrolysis of palm oil using lipase from Candida rugusa in a mechanically agitated batch bioreactor. It is shown that the model presented the experimental data better than previous models found in literature. The fraction of the enzyme, available in the aqueous phase, which is contributing in the coverage of oil-water interface in a stirred batch bioreactor, is determined at different agitation speeds. This fraction is found to increase as agitation speed increases, which is assumed to be a result of the increase in desorption to adsorption ratio of the enzyme at the interface with agitation. � 2007 Elsevier B.V. All rights reserved.