Fats and oils continue to be the main feedstock for alternative transport fuels, especially for FAME (biodiesel) production. Nevertheless, hydrotreated vegetable oils (HVO), which are mixtures of ...alkanes, are also established as a commercial fuel. This review describes recent developments in FAME and HVO production and utilization, including microbial oil use. However, the use of unmodified plant oil as fuel or their corresponding engine and emission tests are not discussed. Recent developed catalysts are described for FAME production, including heterogeneous catalysts, such as super acids, ion‐exchange resins, and other green catalysts produced from biomass. Bio‐catalytic approaches using soluble or immobilized enzymes are at the early commercialization stage. Since HVO production technology is based mainly on current mineral oil industry processing methods, the scientific literature is not as extensive as that of FAME production. The main reaction routes of HVO are a combination of hydrogenation, decarboxylation, decarbonylation, hydroisomerization, and cracking under high pressure and temperatures, using supported and unsupported heterogeneous metal catalysts. Recent reports have highlighted the potential use of non‐food oils, such as microalgae lipids, but industrial significant progress has not occurred, leading to some disillusionment with this approach. Therefore, a clear strategy should be developed for upstream and downstream processes with parallel evaluation of life cycle assessment (LCA). In addition, energy intensive steps of biomass drying and solvent extraction should be avoided by using intelligent technologies, such as in situ processing of wet biomass. Biodiesel and hydrotreated vegetable oils today are the most important alternative diesel fuels in the transport sector. They are produced from the same feedstock, namely oil and fat containing biomass. There has been a shift from food sources to waste material like used cooking oil and animal fat residues as well microbial oils. The latest developments in new feedstock sources, process technologies as well as life cycle assessment and future perspectives are discussed.
Microalgae are the primary producers of economically valuable polyunsaturated fatty acids (PUFAs) and can be used as a resource for biorefining. In this respect, these high-value products may support ...the economical viable energy recovery from microalgae. The extraction of PUFA-containing lipids from Nannochloropsis oculata, a marine species rich in eicosapentaenoic acid (EPA), was tested with a commercially available pressurized fluid extraction technique (PFE, traded as Accelerated Solvent Extraction (ASE®)) in our study. Solvents, which are suitable for an application in the food and pharmaceuticals industry, were used (n-hexane, n-hexane/propan-2-ol (2:1 vol.%), ethanol 96 vol.%) to test the quantitative effect of solvent polarity on the gravimetric extraction yield, total fatty acid and EPA yield. The highest extraction yield resulted from ethanol extraction (36 ± 4 mass%), compared to low yields from n-hexane extraction (6.1 ± 0.3 mass%). A maximum fatty acid yield of 16.7 ± 0.6 mass% was determined for the biomass extracted with the green solvent ethanol. The EPA yield of 3.7 ± 0.1 mass% with the use of ethanol indicates that EPA production from N. oculata is economically beneficial, referring to prognosis from literature. The remaining biomass may eventually be used for energy recovery and other applications within a biorefinery concept.
Gravimetric extraction yield, total fatty acid (Σ FA), total polyunsaturated fatty acid (PUFA) and total eicosapentaenoic acid (EPA) content based on microalgae lipid extract and biomass input (“yield”) in mass%. Data from Accelerated Solvent Extraction (ASE®) tests with n-hexane, a n-hexane/propan-2-ol mixture (2:1 vol.%) and ethanol (96 vol.%) at 60 °C and 10–12 MPa with 5 extraction cycles and 10 min static extraction time each. Freeze-dried and ground (1 mm) microalgae Nannochloropsis oculata was used for the tests. Display omitted
► Pressurized fluid extraction of PUFA-containing microalgal lipids (N. oculata). ► Solvents suit food industry. ► Best results in terms of PUFA-yields achieved with most polar solvent. ► Achieved EPA-yield is economically beneficial (according to literature data).
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► Pseudomonas chlororaphis was investigated for production of mcl-PHA latex under controlled conditions on bioreactor scale ► A surplus material, namely saturated biodiesel fraction ...from animal waste lipids, was used as the sole carbon source ► A detailed kinetic analysis of the bioprocess is provided ► Productivity of the mcl-PHA latex is competitive to other mcl-PHA producing organisms on expensive carbon sources.
A novel description of mcl-PHA biosynthesis by Ps. chlororaphis from tallow-based biodiesel as an inexpensive carbon feed stock is presented. Fermentation protocols, kinetic analysis, an efficient product recovery strategy, and product characterization are included. Maximum specific growth rates (μmax.) of 0.08 h−1, 0.10 h−1 and 0.13 h−1, respectively, were achieved in three different fermentation set-ups. Volumetric productivity for mcl-PHA amounted to 0.071g/L h, 0.094g/L h and 0.138g/L h, final intracellular PHA contents calculated from the sum of active biomass and PHA from 22.1 to 29.4wt.-%, respectively. GC-FID analysis showed that the obtained biopolyester predominantly consists of 3-hydroxyoctanoate and 3-hydroxydecanoate, and, to a minor extent, 3-hydroxydodecanoate, 3-hydroxynonanoate, 3-hydroxyhexanoate, and 3-hydroxyheptanoate monomers. The overall distribution of the monomers remained similar, regardless to working volumes, biodiesel concentrations and pre-treatment of the inoculum.
Based on the canonical correlation analysis, we derive series representations of the probability density function (PDF) and the cumulative distribution function (CDF) of the information density of ...arbitrary Gaussian random vectors as well as a general formula to calculate the central moments. Using the general results, we give closed-form expressions of the PDF and CDF and explicit formulas of the central moments for important special cases. Furthermore, we derive recurrence formulas and tight approximations of the general series representations, which allow efficient numerical calculations with an arbitrarily high accuracy as demonstrated with an implementation in Python publicly available on GitLab. Finally, we discuss the (in)validity of Gaussian approximations of the information density.
Oxidation stability of bodiesel is an important issue because FA derivatives are more sensitive to oxidative degradation than mineral fuel. Therefore, in the most recent European Specifications for ...biodiesel, a minimum value of 6 h for the induction period at 110°C, measured with a Rancimat instrument, is specified. To guarantee this value at the filling station, the use of additional antioxidants will be necessary. In this paper we show the influence of different synthetic and natural antioxidants on the oxidation stability, using the specified test method. Biodiesel produced from rapeseed oil, sunflower oil, used frying oil, and beef tallow, both undistilled and distilled, was investigated. The four synthetic antioxidants pyrogallol (PY), propylgallate (PG), TBHQ, and BHA produced the greatest enhancement of the induction period. These four compounds and the widely used BHT were selected for further studies at concentrations from 100 to 1000 mg/kg. The induction periods of methyl esters from rapeseed, oil, used frying oil, and tallow could be improved significantly with PY, PG, and TBHQ, whereas BHT was not very effective. A good correlation was found between the improvement of the oxidation stability and the FA composition.
The review highlights the correlation between removal of various eco-toxins by micro algae and the production of high-value products thereof. It appraises established and novel strategies for micro ...algal cultivation, downstream processing methods for product recovery, and recent progress in algal generation of the green energy carriers biogas and biohydrogen micro algae. The suitability of selected micro algal species for various final products, and the potential of different strains for abating environmental problems are discussed.
Due to the fact that low cell densities and moderate growth rates are known as the major obstacles towards a broad market penetration of micro algal products, the article shows how high cell densities and reasonable volumetric productivities can be obtained. Here, the article deals with the improvements of process design and nutrient supply regimes that are needed to achieve these goals.
As demonstrated by an integrated case study, mixotrophic cultivation results in increased biomass concentration in a first cultivation step for some micro algal strains like Nannochloropsis oculata. In a second step, the fresh active algal biomass accumulates desired products via CO2 fixation, e.g. from industrial effluent gases, as the sole carbon source. This can be realized by a novel, two-stage, continuously operated closed photo-bioreactor system. After cell harvest and optimized product recovery, the value-added conversion of residual algal biomass for generation of green energy carriers, e.g. in biogas plants, constitutes another focal point of the ongoing research.
Biodiesel (rapeseed oil methyl ester) was aged in a Rancimat device at a temperature of 110 °C and an air flow of 10 L/h. Time-resolved analyses applying gas chromatography–flame ionization ...detection, gas chromatography–mass spectrometry, and ion-exchange chromatography on the formation of aging products were performed. Formic and acetic acid, fatty acids with chain lengths from 5 to 18 carbon atoms, fatty acid methyl esters, and epoxides were quantified. After 12 h of aging, the concentrations of formic and acetic acid were 5600 ± 80 and 1360 ± 80 mg/kg, respectively. Fatty acid concentrations were in the range of <18–4200 mg/kg after 18 h of aging. Linoleic acid methyl ester and linolenic acid methyl ester (19 and 9.1 mass % of the non-aged fuel) were shown to be fully decomposed after 24 and 18 h of aging, respectively. After 51 h of aging, the concentration of oleic acid methyl ester (63 mass % of the non-aged fuel) decreased to 2.2 mass % and trans-epoxy stearic acid methyl ester and cis-epoxy stearic acid methyl ester reached concetrations of 5.9 and 0.7 mass %, respectively. The fuel composition shows only minor changes in early stages of aging, and a strong timely correlation of the formation of aging products with the end of the induction period of fuel was observed.
Over the years, the organosolv pulping process has proven to be a valuable pretreatment method for various lignocellulosic feedstocks. The objective of this study was to characterize and assess the ...potential applicability of the organosolv lignin fraction from European larch sawdust, as no research has been conducted in this field so far. Eight different samples were prepared from the European larch sawdust under varied reaction conditions and one milled wood lignin sample as reference. The reaction temperature and sulfuric acid loading were varied between 420 and 460 K and 0.00 and 1.10% (w/w on dry wood basis) H2SO4, respectively. The antiradical potential (via DPPH• method), chemical structure (via ATR-FTIR, 1H NMR, 31P NMR, and thioacidolysis), as well as the molecular weight distribution of the isolated lignins were analyzed and compared. Results from thioacidolysis show a direct correlation between the amount of β-ether bonds broken and pulping process severity. Similarly, both antiradical potential and phenolic hydroxyl group content exhibit a direct relationship to reaction temperature and catalyst loading. On the contrary, the content of aliphatic hydroxyl groups and the average molecular weights both decreased with increasing process severity. The high content of phenolic hydroxyl groups and antioxidative potential of the larch organosolv fractions, especially for the sample isolated at 460 K and 1.10% H2SO4 loading, indicate good applicability as antioxidants as well as feedstocks for further downstream valorization and require additional research in this area.
► Valuable mathematical models for PHA production by Cupriavidus necator on combined substrates. ► PHA production on waste substrates from biodiesel (FAME and glycerol). ► New low structured model ...for fed-batch fermentation on glucose with glycerol. ► New low structured model for fed-batch fermentation on FAME with valeric acid. ► In silico optimized feeding of C-sources and PHB/PHBV content by mathematical models.
Two low structured mathematical models for fed-batch production of polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate by Cupriavidus necator DSM 545 on renewable substrates (glycerol and fatty acid methyl esters-FAME) combined with glucose and valeric acid, were established. The models were used for development/optimization of feeding strategies of carbon and nitrogen sources concerning PHA content and polymer/copolymer composition. Glycerol/glucose fermentation featured a max. specific growth rate of 0.171h−1, a max. specific production rate of 0.038h−1 and a PHB content of 64.5%, whereas the FAME/valeric acid fermentation resulted in a max. specific growth rate of 0.046h−1, a max. specific production rate of 0.07h−1 and 63.6% PHBV content with 4.3% of 3-hydroxyvalerate (3HV) in PHBV. A strong inhibition of glycerol consumption by glucose was confirmed (inhibition constant ki,G=4.28×10−4gL−1). Applied concentration of FAME (10–12gL−1) positively influenced on PHBV synthesis. HV/PHBV ratio depends on applied VA concentration.
Environmental concerns are driving industry to develop viable alternative fuels from renewable resources. On the other hand, to reduce food surplus, the Agricultural Policy of the European Union (EU) ...obliges the European farmers to leave a percentage of the arable land as set-aside, where can be grown, as an exception, vegetables for nonfood purposes, i.e., energetic ones. Currently, fossil fuels are used in diesel engines and are essential in industrialized places. In addition, petroleum-based diesel increases environmental pollution. To solve these problems, transesterified vegetable oil that has been grown in set-aside lands can be considered to be a renewable energy resource. In this sense, this work describes the optimization of the parameters involved in the transesterification process of Brassica carinata oil. Gas chromatography was used to determine the fatty acid composition of Brassica carinata oil and its esters. Results revealed that the free fatty acid content is a notorious parameter to determine the viability of the vegetable oil transesterification process. In this sense, it was not possible to perform a basic transesterification using Brassica carinata oil with a high erucic acid content. The transesterification process of Brassica carinata without erucic acid required 1.4% KOH and 16% methanol, in the range of 20-45 C, after 30 min of stirring. Our results suggest that the greater the presence of KOH, the lesser the methanol requirements. However, this is valid only under certain limits. Also, if the presence of KOH or methanol is lower or higher than the optimal values, the reaction either does not fully occur or leads to soap production, respectively. Based on this field trial, biodiesel from Brassica carinata oil could be recommended as a diesel fuel candidate if long-term engine performance tests provide satisfactory results.
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