Synthesis of biodiesel from vegetable oils wastewater sludge by in-situ subcritical methanol transesterification: Process evaluation and optimization (original) (raw)
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Biodiesel production from lipids of municipal sewage sludge by direct methanol transesterification
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2017
Municipal sewage sludge (MSS) is a biowaste formed during wastewater treatment and the sewage sludge can be obtained from industrial wastewater treatment system. The sewage sludge contains a variety of organic and inorganic compounds, mainly lipids, proteins, sugars, detergents, and phenols. The MSS contains a significant amount of lipid fraction characterized as oils, greases, fats, and long-chain fatty acids. The average yield of methyl esters from the MSS lipids is 24%. The total average of saturated fatty acids reaches as high as 55.0%. Palmitic acid (37.5%) was the major saturated fatty acid, followed by stearic acid (12.0%). Oleic acid (29.0%) was the major unsaturated fatty acid, followed by linoleic acid (6.2%). The optimum production of biodiesel is faced with huge challenges. The main challenges are collecting and drying the sludge, separating lipids, microbial processing, optimum production of biodiesel and product separation, soap formation, maintaining product quality, bioreactor design, economics of biodiesel production, and regulatory concerns. Wet MSS samples were used in the experiments. Drying cost is 41.5% of the total cost of biodiesel from the sludge. The increase in water content does not affect methyl ester (biodiesel) efficiency in supercritical methanol transesterification (SCMT). The increase in free fatty acid content does not affect methyl ester efficiency in SCMT.
Production of biodiesel from activated sludge
Lipids of microbial origin have gained much attention due to its wide applicability and high productivity. Widely studied microbial lipids are those coming from single cell oils such as microalgae, yeast and activated sludge. Many researches have focused on enhancing lipid accumulation as well as biomass productivity with hope to utilize the accumulated lipids as an alternative source for biodiesel production. Unfortunately these biological lipids have often been under utilized due to inefficient extraction technologies. In addition, in order to maximize lipid extraction toxic solvents such as chloroform are often employed. In this study subcritical water (SCW) was employed for the treatment of activated sludge samples from various sources to enhance their extractable intracellular lipids. Optimum temperature and time for SCW treatment of wet activated sludge was found to be 175 °C and 15 min, respectively. After SCW treatment, a 2 to 4 folds increase in the extractable neutral lipid was observed without the need of using toxic solvent such as chloroform and cyclohexane. An investigation on the possible mechanism on how SCW treatment was able to improve lipid extractability was also carried out in this study.
Experimental analysis of lipid extraction and biodiesel production from wastewater sludge
Fuel Processing Technology, 2011
The most promising renewable alternative fuel, biodiesel, is produced from various lipid sources. Primary and secondary sludge of municipal wastewater treatment facilities are potential sources of lipids. In this study, factorial experimental analyses were used to study the influence of different variables on the lipid extraction and biodiesel production from dried municipal primary and secondary sludge (Adelaide Pollution Control Plant, London, ON, Canada). The empirical models were developed for each factorial analysis. The temperature turned out to be the most significant variable for lipid extraction by using methanol and hexane as solvents. Extraction using methanol resulted in a maximum of 14.46 (wt/wt) % and 10.04 (wt/wt) % lipid (on the basis of dry sludge), from the primary and secondary sludge sources respectively. A maximum of 11.16 (wt/wt) % and 3.04 wt/wt% lipid (on the basis of dry sludge) were extracted from the primary and secondary sludge sources, respectively, using hexane as a solvent. The FAME (fatty acid methyl ester) yield of the H 2 SO 4 catalyzed esterification-transesterification of the hexane and methanol extracted lipids were 41.25 (wt/wt) % and 38.94(wt/wt) % (on the basis of lipid) for the primary sludge, and 26.89 (wt/wt) % and 30.28 (wt/wt) % (on the basis of lipid) for the secondary sludge. The use of natural zeolite as a dehydrating agent was increased the biodiesel yield by approximately 18 (wt/wt) % (on the basis of lipid). The effect of temperature and time was also investigated for biodiesel production from the lipid of wastewater sludge. The yield and quality of the FAME were determined by gas chromatography.
Journal of Food Process Engineering, 2019
Activated sludge is currently being investigated as a potential feedstock to produce biodiesel. Reports have shown that its lipid yield is usually low, compared to the commercially available feedstocks, such as soybean, sunflower, and rapeseed oils. The current work is geared toward investigating the potential of enhancing the total lipid yield (neutral and phospholipid) by the application of subcritical water. The results show that subcritical water treatment increased the total lipid yield by 145% at the optimum conditions 280 C, 40 min, 15 mL of water and biomass loading of 5%. The lipid classes identified were waxes, acylglycerol, sterol, free fatty acid, and phospholipids. The results of the fatty acid methyl esters analysis revealed palmitic acid as the predominant fatty acid. Practical applications The practical applications of the results are informed from the improved lipid yield obtained, suggesting that subcritical water treatment is essential if activated sludge were to be a viable feedstock for biodiesel, renewable diesel, and oleochemicals productions. This will serve as a sustainable activated sludge disposal strategy. 1 | INTRODUCTION Bioenergy such as biodiesel is currently being produced in the United States, Europe, Philippines, Malaysia, and Indonesia, using feedstocks such as soybean, rapeseed and sunflower, coconut, and palm oils, respectively, (Korbitz, 1999). These feedstocks contribute to between
2020
Fatty acid methyl ester (FAME) or biodiesel is a biofuel conventionally produced from edible oil and methanol, using an alkaline catalyst, through a transesterification reaction. As FAME is mostly produced from edible vegetable oils, crop soils are used for its production, increasing deforestation and producing a fuel more expensive than diesel. In addition, between 70 and 80% of the total FAME production costs correspond to the vegetable oils. Therefore, the use of waste lipids such as waste frying oils (WFO), waste fats and soapstock has been proposed as low-cost alternative to feedstock. Non-edible oils such as jatropha, pongamia and rubber seed oil are also economically attractive. In addition, microalgae, bacteria, yeast and fungi with 20% or higher lipid content are oleaginous microorganisms known as single cell oil and have been proposed as feedstock for FAME production. Alternative feedstocks are characterized by their elevated acid value due to the high level of free fatty acid (FFA) content, causing undesirable s a p o n i f i c a t i o n r e a c t i o n s w h e n a n a l k a l i n e c a t a l y s t i s u s e d i n t h e t r a n s e s t e r i f i c a t i o n reaction. The production of soap consumes the conventional catalyst, diminishing FAME production yield and simultaneously preventing the effective separation of the produced FAME from the glycerin phase. These problems could be solved using biological catalysts, such as lipases or whole cell catalysts, avoiding soap production since the FFAs are esterified to FAME. In addition, by-product glycerol can be easily recovered and the purification of FAME is simplified using biological catalysts. Lipase-catalyzed processes have been widely investigated for FAME production from alternatives raw material. Although interesting results have been reached up to date, the enzymatic catalysis has not become competitive compared to the conventional chemical process. The main reasons explaining this issue are the long reaction time (until 48 h), the loss of enzymatic activity due to methanol use in the reaction and the high operational costs because the lipases cannot be reused. The present chapter described an investigation to a get a feasible lipase-catalyzed process to FAME production from WFO, avoiding lipase inhibition. www.intechopen.com Enzyme Inhibition and Bioapplications 278 2. Lipase catalyzed process to FAME production from waste frying oil: Improving the yield In spite of that some investigations have been carried using WFO instead of edible oils in FAME production using lipases, there is not clear the effect in the process of replace the raw material. Using Rhizopus oryzae as the biocatalyst, FFA from a synthetic WFO were esterified to produce FAME with an improved reaction yield (Li et al., 2007). In addition, using Thermomyces lanuginosus lipases immobilized on a microporous polymer, 97% FAME content from edible sunflower oil was reached, while only 90.2% FAME content was obtained from WFO (Dizge et al., 2009). Watanabe et al. (2001) tested the immobilized the Candida antartica lipase immobilized on acrylic resin (Novozym 435) and obtained a 5.5% reduction in FAME conversion yield when using WFO compared to edible oil as the feedstock. They concluded that the oxidized fatty acid compounds in WFO may be responsible for this decrease. As the effects of using WFO instead of edible oil in lipase-catalyzed processes are not clear, the aim of this study was to elucidate the effect of WFO incorporation in feedstock mixed with rapeseed oil on FAME production yield using Novozym 435 as the catalyst by means of the response surface methodology (RSM). In addition, specific WFO and rapeseed oil chemical characteristics were investigated to identify the components that were responsible for these results. Finally, a preliminary study to establish the optimal time for methanol addition during the reaction was proposed. Both filtered WFO collected from restaurants and crude rapeseed oil from a local factory from Southern Chile were used as the feedstocks. Novozym 435 from Sigma-Aldrich was used as the catalyst. Methyl heptadecanoate, 1,2,3-butanetriol and 1,2,3-tricaprinoylglycerol were used as internal standards and were chromatographically pure. RSM was used to analyze and optimize the interaction effects of four variables on FAME production yield (Table 1): the WFO content in the feedstock mixture (% wt), the final methanol-to-oil ratio (mol/mol), temperature (°C) and Novozym 435 dosage (% wt based on oil weight). A central composite matrix with 5 levels was used and 30 runs were carried out in a random order. Each run was performed in triplicate. All reactions were incubated in flasks containing 1 mL of oil at 200 rpm. The volume of the flasks was selected to maintain perfect agitation of the samples when using both the highest dosage of catalyst and the lowest methanol-to-oil molar ratio. Under these conditions, different combinations of feedstock mixture, dosage of catalyst, methanol-to-oil molar ratio and temperature were used. Methanol was added in two steps to avoid lipase inhibition (Shimada et al., 2002). In the first step, one-third of the total molar ratio was added according to Table 1, while in the second step, the remaining two-thirds of the total molar ratio was added to generate the final methanol-to-oil molar ratio. To establish the reaction and second methanol addition times, a preliminary study was performed. This experiment was carried out for 48 h using the RSM central point, with 50% (wt) WFO in a mixed feedstock, a methanol/oil molar ratio of 3:1 and 9% (wt) Novozym 435 at 45°C and stirring 200 rpm. Samples were immediately stored at 4°C to stop the reaction. The upper layer was analyzed by gas chromatography for FAME quantification.
Biofuels, 2019
The search for a cheap and readily available feedstock for biodiesel production has driven researchers to investigate the potential use of activated sludge-derived lipid. Due to the low lipid yield of activated sludge, the utility of subcritical water (SCW) is being considered as a means of increasing the extractable lipids. In this work, operating parameters (temperature, time and biomass loading) identified in our previous work to influence lipid yield from activated sludge under SCW treatment were optimized, using face-centered central composite design (FCCCD). The results show that the maximum lipid yield obtained from the liquid and solid products, post SCW treatment, at the optimum conditions of temperature 80 C, extraction time 20 min and biomass loading 1%, was 41.0 (wt./wt.)%. This gives approximately 454 (wt./wt.)% increase from 7.4 (wt./wt.)% obtained by solvent extraction without SCW treatment. The results suggest that activated sludge is a potential feedstock for biodiesel production.
Comparison of Ex-Situ and In-Situ Transesterification for the Production of Microbial Biodiesel
Bulletin of Chemical Reaction Engineering & Catalysis, 2021
Microbial biodiesel is converted from microbial lipids via transesterification process. Most microbial biodiesel studies are focusing on the use of microalgal lipids as feedstock. Apart from using microalgae for lipid biosynthesis, lipids can also be extracted from other oleaginous microorganisms like fungi and yeast. However, there are gaps in the studies of lipid production from filamentous fungi, especially in-situ transesterification process. The aim of this project is to compare in-situ with the ex-situ transesterification of fungal biomass from Aspergillus oryzae. In exsitu transesterification, two methods of lipid extraction, the Soxhlet extraction and the Bligh and Dyer extraction, were performed. For in-situ transesterification, two methods using different catalysts were investigated. Basecatalyzed in-situ transesterification of fungal biomass resulted on the highest Fatty Acid Methyl Esters (FAME) yield. The base-catalyzed in-situ transesterification was further optimized via Central Composite Design (CCD) of Response Surface Methodology (RSM). The parameters investigated were the catalyst loading, methanol to biomass ratio and reaction time. The optimization showed that the highest FAME yield was at 25.1% (w/w) with 10 minutes reaction time, 5% catalyst and 360:1 of the ratio of the methanol to biomass. Based on Analysis of Variance (ANOVA), the model was found to be significant according to the value of "Prob >F" of 0.0028.
Biodiesel from activated sludge throughin situtransesterification
Journal of Chemical Technology & Biotechnology, 2010
BACKGROUND: The microbial biomass present in activated sludge contains lipidic compounds that can be used as biodiesel feedstock. In this study, the production of biodiesel from activated sludge from Tuscaloosa, AL was optimized based on the yield of fatty acid methyl esters (FAMEs). In situ transesterification was used with sulfuric acid as catalyst. A general factorial design of 4 × 6 × 5 for temperature, methanol to sludge ratio and catalyst concentration, respectively, was considered for optimization. RESULTS: Biodiesel yield can be adequately described by the quadratic response surface model with R 2 of 0.843 and statistically insignificant lack of fit (p = 0.152). Numerical optimization showed that an optimum biodiesel yield of 4.88% can be obtained at 55 • C, 25 methanol to sludge ratio and 4% volume sulfuric acid. The optimum experimental biodiesel yield was indeed obtained at that condition but with a value of 4.79 ± 0.02%. The highest error was 2.30% which indicates good agreement between the model and the experimental data. CONCLUSIONS: Acid-catalyzed polymerization of unsaturated fatty acids or their esters at temperature above 60 • C significantly decreased biodiesel yield. The fatty acid profile of the biodiesel produced indicates that activated sludge may be used as biodiesel feedstock.
Energy Conversion and Management, 2017
In light of the availability of low-cost methane (CH 4) derived from natural gas and biogas along with increasing concerns of the greenhouse gas emissions, the production of alternative liquid biofuels directly from CH 4 is a promising approach to capturing wasted energy. A novel biorefinery concept integrating biological conversion of CH 4 to microbial lipids together with lipid extraction and generation of hydrocarbon fuels is demonstrated in this study for the first time. An aerobic methanotrophic bacterium, Methylomicrobium buryatense capable of using CH 4 as the sole carbon source was selected on the basis of genetic tractability, cultivation robustness, and ability to accumulate phospholipids in membranes. A maximum fatty acid content of 10% of dry cell weight was obtained in batch cultures grown in a continuous gas sparging fermentation system. Although phospholipids are not typically considered as a good feedstock for upgrading to hydrocarbon fuels, we set out to demonstrate that using a combination of novel lipid extraction methodology with advanced catalyst design, we could prove the feasibility of this approach. Up to 95% of the total fatty acids from membrane-bound phospholipids were recovered by a two-stage pretreatment method followed by hexane extraction of the aqueous hydrolysate. The upgrading of extracted lipids was then demonstrated in a hydrodeoxygeation process using palladium on silica as a catalyst. Lipid conversion in excess of 99% was achieved, with a full selectivity to hydrocarbons. The final hydrocarbon mixture is dominated by 88% pentadecane (C 15 H 32) based on decarbonylation/decar boxylation and hydrogenation of C16 fatty acids, indicating that a biological gas-to-liquid fuel (Bio-GTL) process is technically feasible.
Biodiesel from activated sludge through in situ transesterification
Journal of Chemical Technology & Biotechnology, 2010
BACKGROUND: The microbial biomass present in activated sludge contains lipidic compounds that can be used as biodiesel feedstock. In this study, the production of biodiesel from activated sludge from Tuscaloosa, AL was optimized based on the yield of fatty acid methyl esters (FAMEs). In situ transesterification was used with sulfuric acid as catalyst. A general factorial design of 4 × 6 × 5 for temperature, methanol to sludge ratio and catalyst concentration, respectively, was considered for optimization.