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A review on harvesting, oil extraction and biofuels production technologies from microalgae
Abstract
In the current scenario of depleting energy resources, increasing food insecurity and global warming, Jatropha has emerged as a promising energy crop for India. The aim of this study is to examine the life cycle energy balance for Jatropha biodiesel production and greenhouse gas emissions from post-energy use and end combustion of biodiesel, over a period of 5 years. It’s a case specific study for a small scale, high input Jatropha biodiesel system. Most of the existing studies have considered low input Jatropha biodiesel system and have used NEB (Net energy balance i.e. difference of energy output and energy input) and NER (Net energy ratio i.e. ratio of energy output to energy input) as indicators for estimating the viability of the systems. Although, many of them have shown these indicators to be positive, yet the values are very less. The results of this study, when compared with two previous studies of Jatropha, show that the values for these indicators can be increased to a much greater extent, if we use a high input Jatropha biodiesel system. Further, when compared to a study done on palm oil and Coconut oil, it was found even if the NEB and NER of biodiesel from Jatropha were lesser in comparison to those of Palm oil and Coconut oil, yet, when energy content of the co-products were also considered, Jatropha had the highest value for both the indicators in comparison to the rest two.
... 15 Kwangdinata has produced biodiesel from lipid, extraction result of Chaetoceros calcitrans dry biomass by ultrasonication method as cell pretreatment then transesterification reaction use base catalyst (KOH), it obtains a yield of lipid was 16.23% (w/w) from dry biomass and yield of biodiesel was 35.35% (w/v) from lipid total. 17 Ultrasonication is a physical method of cell disruption through ultrasonic waves (>20 kHz). In this method, during the ultrasonication process will be formed microbubbles then they collide randomly, that namely cavitation. ...
... 16 Ultrasonication method is able to improve the yield of lipids until 50-500% on both Nannochloropsis oculata and Chlorella Vulgaris. 17 The other cell disruption method has been done by Park, it was hydrothermal acid as cell pre-treatment before lipid extraction, which result in 337 mg/g cell from dry biomass. 17 Hydrothermal acid is a chemical method of cell disruption by using strong acid (such as HCl or H2SO4) to hydrolyze the cell wall at a high temperature (120 o C) to upgrade the ability of the cell wall lysis so that the components that are contained in microalgae cell (in this focus is lipid) could be extracted perfectly. ...
... 17 The other cell disruption method has been done by Park, it was hydrothermal acid as cell pre-treatment before lipid extraction, which result in 337 mg/g cell from dry biomass. 17 Hydrothermal acid is a chemical method of cell disruption by using strong acid (such as HCl or H2SO4) to hydrolyze the cell wall at a high temperature (120 o C) to upgrade the ability of the cell wall lysis so that the components that are contained in microalgae cell (in this focus is lipid) could be extracted perfectly. 16,17 The purpose of this study is to determine the FAME productivity from lipid Chaetoceros calcitrans that was created by the ex and in-situ methods accompanied by hydrothermal acid and ultrasonication treatments for the lipid extraction. ...
The manufacture of biodiesel from lipids can be carried out by ex and in-situ methods. The difference lies in the continuity of lipid extraction and its transesterification into biodiesel, either separately or simultaneously. The paper reported the FAME productivity from lipid Chaetoceros calcitrans that were created by both methods. The research was started by culturing Chaetoceros calcitrans in seawater media with the addition of trace elements, it produced a dry cell weight of 15 g/L on the fifth day of fermentation. The highest yield of lipid was 61.40% (w/w) obtained when the extraction was carried out from the biomass in a mixed solvent between n-hexane and 96% ethanol (1:1) assisted by a combination of hydrothermal acid and ultrasonication treatments. The transesterification of lipid that was carried out with methanol and 6% (v/v) H2SO4 catalyst for one hour at 60oC in an ex-situ process, produced FAME of 19.15% (w/w). Meanwhile, the in-situ method which joined the lipid repealing and transesterification steps simultaneously produced 21.59% (w/w) of biodiesel. The in-situ process exhibited higher FAME than the ex-situ. The main FAME component on the biodiesel of Chaetoceros calcitrans was methyl oleic (C17H33COOCH3, C18:1(Δ9 )). With insight into the cell’s pre-treatment and simultaneous process of the in-situ method, it is feasible to apply the techniques for biodiesel production in the future
... The efficiency of this technique depends on the microalgae species, for example, in Spirulina sp., cell rupture is easy since it does not have a rigid cell wall, while Chlorella sp. has a rigid cell wall [27]. Mechanical destruction can be carried out by various techniques, such as ultrasound, bead milling, microwaves, high pressure homogenization, pressing, among others [28,29]. The performance and energy consumption are different in all cell disruption treatment methods, and some of the techniques are only effective for certain species of microalgae. ...
... Another alternative is extraction with supercritical CO 2 , which has several advantages: the extraction efficiency is high; it allows processing at low temperatures; it is non-toxic, non-flammable, and the supercritical solvent can be easily removed [23]. However, supercritical extraction equipment is expensive and operating costs are also high, compared to extraction with organic solvents [28]. ...
... On the other hand, the method used for extraction must be fast, easily scalable, efficient, and must not damage the extracted lipids. Biomass drying consumes a lot of energy, therefore, applying a methodology to extract lipids from microalgae by wet means can reduce this energy consumption [28]. ...
Microalgae have a high capacity to capture CO2. Additionally, biomass contains lipids that can be used to produce biofuels, biolubricants, and other compounds of commercial interest. This study analyzed various scenarios for microalgae lipid production by simulation. These scenarios include cultivation in raceway ponds, primary harvest with three flocculants, secondary harvest with pressure filter (and drying if necessary), and three different technologies for the cell disruption step, which facilitates lipid extraction. The impact on energy consumption and production cost was analyzed. Both energy consumption and operating cost are higher in the scenarios that consider bead milling (8.79–8.88 kWh/kg and USD 41.06–41.41/kg), followed by those that consider high-pressure homogenization (HPH, 5.39–5.46 kWh/kg and USD 34.26–34.71/kg). For the scenarios that consider pressing, the energy consumption is 5.80–5.88 kWh/kg and the operating cost is USD 27.27–27.88/kg. The consumption of CO2 in scenarios that consider pressing have a greater capture (11.23 kg of CO2/kg of lipids). Meanwhile, scenarios that consider HPH are the lowest consumers of fresh water (5.3 m3 of water/kg of lipids). This study allowed us to develop a base of multiple comparative scenarios, evaluate different aspects involved in Chlorella vulgaris lipid production, and determine the impact of various technologies in the cell disruption stage.
... High fatty acids containing low-cost feedstock, i.e., waste oil, are also processed through this method. In the first stage, methyl esters are formed by converting fatty acids, while the base catalyst transforms leftover triglycerides into methyl esters (Pragya et al. 2013). ...
... Downstream processing is an energy-efficient approach that is widely used to separate microalgae from water. The sedimentation technique has the potential to successfully separate microalgae such as Spirulina, which settle due to their increased density and size (Pragya et al. 2013). Before the sedimentation procedure, flocculation and coagulation occur. ...
... This procedure typically requires flocculants and is followed by coagulation and flocculation (Singh et al. 2018). Electrolytic flotation, dissolved air flotation, and dispersed flotation are three major types of floatation based on bubble size (Pragya et al. 2013). Dispersed air, micro-flotation, foam floatation, vacuum gas, dissolved air, flocculation flotation, electro flotation, and ozone flotation are the methods used for flotation (Japar et al. 2017). ...
The world is experiencing an energy crisis and environmental issues due to the depletion of fossil fuels and the continuous
increase in carbon dioxide concentrations. Microalgal biofuels are produced using sunlight, water, and simple salt minerals.
Their high growth rate, photosynthesis, and carbon dioxide sequestration capacity make them one of the most important
biorefnery platforms. Furthermore, microalgae's ability to alter their metabolism in response to environmental stresses to
produce relatively high levels of high-value compounds makes them a promising alternative to fossil fuels. As a result, microalgae can signifcantly contribute to long-term solutions to critical global issues such as the energy crisis and climate change.
The environmental benefts of algal biofuel have been demonstrated by signifcant reductions in carbon dioxide, nitrogen
oxide, and sulfur oxide emissions. Microalgae-derived biomass has the potential to generate a wide range of commercially
important high-value compounds, novel materials, and feedstock for a variety of industries, including cosmetics, food, and
feed. This review evaluates the potential of using microalgal biomass to produce a variety of bioenergy carriers, including
biodiesel from stored lipids, alcohols from reserved carbohydrate fermentation, and hydrogen, syngas, methane, biochar and
bio-oils via anaerobic digestion, pyrolysis, and gasifcation. Furthermore, the potential use of microalgal biomass in carbon
sequestration routes as an atmospheric carbon removal approach is being evaluated. The cost of algal biofuel production is
primarily determined by culturing (77%), harvesting (12%), and lipid extraction (7.9%). As a result, the choice of microalgal species and cultivation mode (autotrophic, heterotrophic, and mixotrophic) are important factors in controlling biomass
and bioenergy production, as well as fuel properties. The simultaneous production of microalgal biomass in agricultural,
municipal, or industrial wastewater is a low-cost option that could signifcantly reduce economic and environmental costs
while also providing a valuable remediation service. Microalgae have also been proposed as a viable candidate for carbon
dioxide capture from the atmosphere or an industrial point source. Microalgae can sequester 1.3 kg of carbon dioxide to
produce 1 kg of biomass. Using potent microalgal strains in efcient design bioreactors for carbon dioxide sequestration
is thus a challenge. Microalgae can theoretically use up to 9% of light energy to capture and convert 513 tons of carbon
dioxide into 280 tons of dry biomass per hectare per year in open and closed cultures. Using an integrated microalgal biorefnery to recover high-value-added products could reduce waste and create efficient biomass processing into bioenergy. To
design an efcient atmospheric carbon removal system, algal biomass cultivation should be coupled with thermochemical
technologies, such as pyrolysis
... Harvesting consists of separating microalgae from its growing medium. Large-scale production of microalgae biomass and its ulterior extraction is the main challenge to develop cost-effective technologies for efficient harvesting and byproduct extraction [121]. In this sense, different harvesting technologies have been assessed to enhance the productivity of byproducts and, especially in this case, lipids content. ...
... Harvesting of microalgae can be divided into two step processes. The first consists in separating microalgae biomass from the culture broth (2-7% dw), the second step is the thickening to promote more concentrated biomass than in the first step [121]. All harvesting processes may include thickening, dewatering and drying. ...
... Table 3 summarizes the characteristics of the most common oil extraction methods from microalgae biomass. Residues generated after oil extraction are rich in different byproducts, such as carbohydrates and proteins, that may be used to make other different products as biogas or biohydrogen, food additives, pigments, fertilizers, etc. [121,133]. Considerations of microalgae oils as lubricants are provided in the next section. -Complex control of the procedure. ...
https://transferencia.tec.mx/2022/06/14/lubricantes-de-microalgas-una-alternativa-verde-para-la-industria/
Los lubricantes son materiales de gran importancia práctica ya que permiten reducir la fricción y el desgaste de superficies en movimiento. Desafortunadamente, la mayoría de los lubricantes utilizados en la actualidad son derivados del petróleo y su uso y desecho tienen un impacto ambiental significativo, ya que dañan el medio ambiente, tienen baja degradabilidad y propician daños a la salud.
Por ejemplo, un litro de grasa o aceite derivados del petróleo arrojado directamente al drenaje, lo cual infortunadamente es todavía una práctica común en nuestro país, contamina más de mil litros de agua y puede llegar a formar “tapones” que impiden el flujo de las aguas residuales y provocan daños en las tuberías e inundaciones.
En las últimas décadas se han investigado muchas alternativas para reemplazar los lubricantes derivados del petróleo. Las más prometedoras son aquellas que involucran el uso de aceites extraídos de semillas vegetales como la palma, el ricino, la jojoba y el girasol, entre otros, los cuales pueden biodegradarse tanto en cuerpos de agua como en la tierra. Gracias a estas investigaciones se ha determinado que inclusive estos aceites vegetales mezclados con algunos aditivos pueden ofrecer mejores propiedades lubricantes en comparación con aquellos derivados del petróleo.
Sin embargo, existe un problema grave de sustentabilidad cuando se recurre de manera masiva al uso de estos aceites vegetales para producir lubricantes, ya que en muchos casos estos forman parte de nuestra alimentación básica, creando una competencia entre las necesidades de consumo humano y las industriales, así como por tierras cultivables provocando una posible alza en los precios de dichas materias primas.
Afortunadamente, existe una nueva solución ecológica y sustentable a estos problemas, que consiste en la producción de lubricantes “bio” hechos a base de aceite de microalgas para diversas aplicaciones industriales. Las microalgas son microorganismos fotosintéticos que utilizan la luz del sol como fuente de energía y producen oxígeno de forma natural.
Estos microorganismos tienen la capacidad de crecer sin el uso de tierras cultivables en ambientes marinos y en agua dulce, así como en medios artificiales y aguas residuales, y generar diferentes tipos de biomoléculas de gran utilidad como proteínas, antioxidantes, complementos alimenticios, aceites, entre otros.
Las microalgas pueden ser producidas en diferentes tipos de fotobiorreactores, los cuales son dispositivos capaces de mantener un medio estable (temperatura, pH, baja concentración de O2) y proporcionar los nutrientes y luz necesarios para el crecimiento de algas. Los fotobiorreactores se dividen generalmente en abiertos y cerrados, y pueden operar tanto en interiores como en exteriores. En ambos casos, la agitación y el mezclado son necesarios para homogenizar el cultivo, distribuir los nutrientes y proporcionar las cantidades adecuadas de luz para llevar a cabo de proceso de fotosíntesis. Los fotobiorreactores cerrados usualmente se fabrican con tubos de vidrio o de plástico, los cuales permiten el control de la evaporación del agua y disminuyen los riesgos de contaminación. Ese tipo de reactores ocupan áreas reducidas y se utilizan principalmente para producción a pequeña escala. Sin embargo, los fotobiorreactores abiertos (Figura 1) ocupan extensiones mucho más grandes, pueden localizarse en lagos y estanques, y son usados para producción a gran escala. La desventaja los fotobiorreactores abiertos es su exposición al ambiente, lo que se traduce en pérdidas significativas de agua por evaporación y en riesgo de contaminación por otros microorganismos.
El proceso para la obtención de aceites de microalgas involucra la selección de una especie apropiada de microalga (por ejemplo “Chlorella sp.”), su cultivo en fotobiorreactores bajo condiciones controladas, la cosecha de la biomasa de las microalgas y, finalmente, la extracción y purificación del aceite. Posteriormente, el aceite extraído debe ser modificado mediante tratamientos particulares de conversión química y su formulación se realiza posteriormente empleando aditivos”, lo cual se realiza en función de la aplicación industrial deseada (Figura 2). Algunas de las aplicaciones más importantes para estos aceites en la industria son como lubricantes de motor y transmisión de engranes, como grasas para rodamientos, como fluidos de corte, como aceites para transformador o lubricantes de motosierras, así como fluidos para perforación, entre otras.
En esta investigación se lograron identificar los avances más recientes en el proceso de crecimiento y generación de aceites de microalgas, las especies más prometedoras para la producción de aceites con buenas propiedades lubricantes y los procesos de conversión química más adecuados para formular lubricantes para diversos usos industriales. Utilizando esta información se elaboró una guía de selección, modificación y producción de aceites de microalgas que permitirá desarrollar una nueva clase de biolubricantes biodegradables y sustentables que podrían reemplazar a los lubricantes derivados del petróleo a mediano plazo.
... Out of these 5 most cited publications, the publication by Miao and Wu [58] has been cited the most (22 times) by the selected group of 30 documents. This is followed by the publication by Chisti [57], Singh et al. [62], Pragya et al. [63], and Umdu et al. [64] cited 14, 13, 10, and 9 times respectively, by the selected group of 30 documents. This suggests that other high-quality papers in the field of algae for biodiesel closely follow these 5 publications. ...
... This suggests that other high-quality papers in the field of algae for biodiesel closely follow these 5 publications. As can be seen in Figure 7, there were 12 interconnected clusters, with the most cited papers in each cluster coming from Rawat et al. [60], Patil et al. [23], Ho et al. [65], Amin [66], Lee et al. [59], Nagle and Lemke [53], Pragya et al. [63], Vasudevan and Briggs [67], Lam and Lee [68], Scranton et al. [69], Chisti [57], and Miao and Wu [58]. 11 International Journal of Energy Research 3.8. ...
Algae are a desirable biodiesel feedstock because they take up little space, have a high algal-cell biomass per unit area, and can sustainably meet a large portion of the world’s future energy needs. Using several bibliometric indicators, this study assesses the research productivity of algae for biodiesel production. The dataset was retrieved from the Scopus database using an appropriate keyword search. The VOSviewer v1.6.18 and Biblioshiny in R -studio were then utilised for bibliometric analysis and network visualisation. The study found that, with the first article being published in 1990 and an annual scientific growth rate of 14.76%, research on algae for the generation of biodiesel is still in its early phases. Although the possibility of utilising algae to produce biodiesel was originally mentioned in 1990, it was only until 2006 that several researchers started to show an interest in the subject. 101 articles were published in 2015, which is the most ever. The most prolific countries in terms of publications, ongoing collaborations and cooperation, best publishing institutions, and prestigious journals, as well as the most productive researchers and the most highly referenced works in the field, have all been recognised and presented. Finally, a keyword co-occurrence analysis of the subject was presented and discussed to provide research insights into the field. The bibliometric indicators of the study are intended to aid researchers in finding potential research topics, high-quality scientific literature, and suitable journals for publishing research on algae for biodiesel production.
... For most algae the optimum pH is in the range of 6À8. However, during photosynthesis, the pH of the medium tends to increase (10À11) due to CO 2 fixation during light exposure (Hansen, 2002;Pragya et al., 2013a) and decrease in pH during the dark phase due to the respiratory processes. The CO 2 and pH are related by the chemical equilibrium of various chemical species (CO 2 , H 2 CO 3 , HCO 3 2 , and CO 3 À2 ) in the medium. ...
... In temperate and subtropical climates, microalgae grow at a time of year, while they grow around the year in tropical regions. Microalgae grown for lipids have an optimum temperature range of 15 CÀ40 C. Various authors have reported (Pragya et al., 2013a) that several oil-producing microalgal species grow best between 25 C and 30 C. However, the optimal temperature varies from species to species and the desired algal response. ...
Microalgae grow at a far faster rate than the terrestrial crops. Algal biomass cultures can be carried out on nonarable lands, utilizing nonpotable salty water and wastewater. They have a quick biomass development character and possess a very high oil content, thus have long been recognized as potentially viable candidates for biofuel production. Research and businesses alike are increasingly looking into the utilization of microalgal biomass as a source of alternative biodiesel biofuel feedstocks. To get the most of algal biomass, researchers are also looking at the possibility of producing biodiesel and biogas from microalgae simultaneously. To improve algal biofuel production, the factors impacting microalgal development, as well as the collection of feedstocks and the conversion process, are all examined in this chapter. Microalgal biofuels are also discussed in terms of their economic possibilities, problems, and potential futures.
... Microalgae are photosynthetic microorganisms capable of capturing sunlight and converting carbon dioxide into value-added products such as biofuels, dietary products and animal feed [1]. For biofuel production, microalgae are currently considered the most promising biomass due to their many advantages over terrestrial plants, such as rapid growth, high capacity to accumulate lipids under certain conditions and the possibility of growing them on non-arable land [2]. ...
... These methods however are generally associated with a low efficiency, high capital costs and important energy and/or chemicals consumptions. For example, centrifugation requires a high energy input (up to 8 kWh/m 3 of microalgae, [6]) which represents a huge cost for largescale processing, and may also damage cells due to the high shear forces, resulting in a significant loss of the products of interest [1]. Likewise permeable membranes used for filtration are easily clogged by small microalgae [7], which also leads to important processing costs and material costs. ...
Microalgae are a promising resource for biofuel production, although the lack of effective harvesting techniques limits their industrial use. In this context, flotation, and in particular dissolved air flotation (DAF), is an interesting separation technique that could drastically reduce harvesting costs and make biofuel-production systems more economically viable. But because of the repulsive interaction between cells and bubbles in water, the efficiency of this technique can be limited. To solve this problem, we propose here an original DAF process where bubbles are functionalized with a bio-sourced polymer able to specifically bind to the surface of cells, chitosan. In a first part, we modify chitosan by adding hydrophobic groups on its backbone to obtain an amphiphilic molecule, PO-chitosan, able to assemble at the surface of bubbles. Then, using a recently developed technique based on atomic force microscopy (AFM) combined with microfluidics, we probe the interactions between PO-chitosan coated bubbles and cells at the molecular scale; results show an enhanced adhesion of functionalized bubbles to cells (from 3.5 to 12.8 nN) that is pH-dependent. Separation efficiencies obtained in flotation experiments with functionalized bubbles are in line with AFM data, and a microalgae separation efficiency of approximately 60% could be reached in a single step. In addition, we also found that PO-chitosan could be used efficiently as a flocculant (nearly 100% of cells removed), and in this case AFM experiments revealed that the flocculation mechanism is based on hydrophobic interactions between cells and PO-chitosan. Altogether, this comprehensive study shows the interest of PO-chitosan to harvest cells in flotation or flocculation/flotation processes.
... Various types of catalytic transesterification, including acid, base, and enzyme, are commonly used according to the characteristics and targeted product. However, an in situ transesterification that combines lipid extraction and transesterification in a single-stage operation is gaining interest because of its promising biodiesel yield [47]. The main benefits of such an approach are its significantly lower cost, shorter reaction time, and close monitoring of potential pollution sources [48]. ...
... Alternatively, integration between open ponds and photobioreactors has been proposed to reduce the invasion of wild algal strains and ensure a cost-competitive operational environment [100]. . This method has been reported with an astonishing harvest efficiency of 85% to 95% [47]. Yet, a great dosage demand of aluminium sulfate is required to maintain the harvesting efficiency, which has the potential of contaminating the final product [102]. ...
An emerging renewable energy source from living organisms, microalgae are recognized for its remarkable energy content and continuously receiving interest with a great potential in increasing its shares in fuel market. The main challenge for stable biorefinery operation is cultivation, given that the growth of microalgae is highly dependent on climate conditions, especially ambient temperature, and solar exposure. Herein, an advanced forecasting algorithm predicts daily climate conditions a year ahead. The forecast is then used in a dynamic metaheuristic optimization framework to determine optimal microalgae biorefinery process pathways with promising total annual margins and greenhouse gas emissions. In return, the optimal solution is reported with a total annual margin of 815,716 US$/y and greenhouse gas emission of 1.1 × 10⁷ kg CO2-eqv/y. The most feasible microalgae species among the selection pool are identified in terms of kinetic growth, which is attributed to the climate behavior of the selected case-study region. A scheduling scheme is then identified for the optimal harvest period of cultivated microalgae. Next, uncertainty analysis for the selected process configuration is conducted using Monte Carlo simulation to investigate how variations in climate conditions will affect its overall performance. Additionally, the process is further enhanced by including renewable electricity sources which allow reducing 50% greenhouse gas emissions with the configuration of biomass energy (1.2%), solar power (0.1%), and wind energy (98.7%). In summary, this study provided a comprehensive guidelines on strategically deploying large scale microalgae biorefineries considering its long-term operational sustainability abiding the possible uncertainties within the system proposed.
... While first generation biofuels are produced from edible feedstock such as corn, soybeans, sugarcane and rapeseed, second generation biofuels have been prepared from waste and dedicated lignocellulosic feedstocks and finally, third in academic journals covering various aspects of algal biofuel. Most of these studies have focused on the merits of algal strains, cultivation methods, harvesting and extraction techniques, different conversion technologies, as well as life cycle assessment and policy implications (Adenle et al., 2013;Bahadar & Khan, 2013;Brennan & Owende, 2010;Harun et al., 2010;Montingelli et al., 2015;Piloto-Rodriguez et al., 2017;Pragya et al., 2013;Razzak et al., 2013;Sambusiti et al., 2015;Suali & Sarbatly, 2012;Suganya et al., 2016;Tian et al., 2014;Zeng et al., 2011;Zhu, 2015). Therefore, it is necessary to assess the overall development and trends of research related to algal biofuel. ...
... Algae was also used as feedstock for bioethanol production through fermentation (Pragya et al., 2013). The liquefaction and pyrolysis products of algae were mainly affected by the algae composition, temperature, pressure, residence time, and catalyst (Suali & Sarbatly, 2012). ...
The paper systematically presents a survey of the literature on algal biofuel by a bibliometric assessment. Based on 10,201 articles extracted from the Science Citation Index Expanded database during 1980–2019, a knowledge-generating system about algal biofuel has been established through analysis of publication performance, social networks, citations analysis and keywords analysis. Annual publication output in algal biofuel research has rapidly increased, particularly over the past decade. “Bioresource Technology” is the most outstanding journal when all analysis indices have been taken into account. The USA ranks 1st with 2,151 publications and has a high supremacy in international research collaborations. Through the analysis of keywords, the research trends of algae biofuel in algae selection, cultivation, harvesting, extraction, conversion and bioproducts are reviewed. The future of algal biofuel is quite promising, however, for its commercial production, several technical challenges like large-scale algal biomass production, cheap harvesting technology, etc. have to be met a-priori.
... Microalgae's photosynthetic uptake of CO 2 causes pH to rise during the day, while the species respiratory activity causes pH to fall at night (Johnson, 2009). An increase in CO 2 may lead to high biomass accumulation but causes a decrease in pH, which adversely affects the microalgae's physiology (Pragya et al., 2013). ...
The number of restaurants is increasing day by day in almost all the developing countries, causing the increase in the generation of restaurant wastewaters. Various activities (i.e., cleaning, washing, and cooking) going on in the restaurant kitchen lead to restaurant wastewater (RWW). RWW has high concentrations of chemical oxygen demand (COD), biochemical oxygen demand (BOD), nutrients such as potassium, phosphorus, and nitrogen, and solids. RWW also contains fats, oil, and grease (FOG) in alarmingly high concentration, which after congealing can constrict the sewer lines, leading to blockages, backups, and sanitatry sewer overflows (SSOs). The paper provides an insight to the details of RWW containing FOG collected from a gravity grease interceptor at a specific site in Malaysia, and its expected consequences and the sustainable management plan as prevention, control, and mitigation (PCM) approach. The results showed that the concentrations of pollutants are very high as compared to the discharge standards given by department of environment. Maximum values for COD, BOD and FOG in the restaurant wastewater samples were found to be 9948, 3170, and 1640 mg/l, respectively. FAME and FESEM analysis are done on the RWW containing FOG. In the FOG, palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1n9c), linoleic acid (C18:2n6c) are the dominant lipid acids with a maximum of 41, 8.4, 43.2, and 11.5%, respectively. FESEM analysis showed formation of whitish layers fprmed due to the deposition of calcium salts. Furthermore, a novel design of indoor hydromechanical grease interceptor (HGI) was proposed in the study based on the Malaysian conditions of restaurant. The HGI was designed for a maximum flow rate of 132 L per minute and a maximum FOG capacity of 60 kg.
... The outlooks expressed in this research are completely those of the researcher and may not in any state of affairs be regarded. 17 As shown in table 6 methods used to treat high fat to reduce methane inhibition.Some researchers differed in their views on the best ways to treat fatty biomass. Pre-treatment by the bases with ultrasonic have a positive effect on the stability of methane [116, 117 ,118]. ...
... Combustion of biofuels produces ominously less carbon, hence less damage to atmosphere and lower air pollution [61] . ...
Biofuels are fuels produced from biomass (plant or animal materials).
Although biofuels exist in solid, liquid and gaseous form, but it usually refers to
the liquid biofuels designed for usage as fuel for vehicles. It can be derived from
agricultural crops, food crops (sugarcane and palms) or special energy crops,
forestry, agricultural or even from fishery products and organic wastes in much
less time
... The benefit of algal microorganisms lies in their capacity for rapid growth, the high productivity of lipids (palmitic acid (C16:0), linoleic acid (C18:2) and y-linoleic acid (C18:3)), potential in bioremediation technology and various valuable by-products. The harvesting of microalgae is considered one of the key points in biofuel production, representing minimally 20-30% of the total production costs and limiting production on a commercial and industrial scale [12]. ...
... The benefit of algal microorganisms lies in their capacity for rapid growth, the high productivity of lipids (palmitic acid (C16:0), linoleic acid (C18:2) and y-linoleic acid (C18:3)), potential in bioremediation technology and various valuable by-products. The harvesting of microalgae is considered one of the key points in biofuel production, representing minimally 20-30% of the total production costs and limiting production on a commercial and industrial scale [12]. ...
... The previous study had shown that 1.83 kg of carbon dioxide is required to produce 1 kg of microalgae biomass [4,16]. Moreover, cost and pollution can be reduced as no pesticides and herbicides are required to grow the microalgae which further cuts down the input cost and keeps environmental pollution minimal [44]. Besides, microalgae biodiesel is also demonstrating similar properties to conventional diesel and able to meet the requirement established by the American Society for Testing and Materials (ASTM) [26,47]. ...
Chemical fertilizer is the most ubiquitous nutrient source used to cultivate microalgae. However, the bottlenecks associated to its vast usage such as high cost and environmental hazards are evident, whose solution is to include a search for alternative nutrient sources. Thus, nutrient-rich wastewater has been utilized in recent years for microalgae cultivation as it is widely available and able to minimize the usage of freshwater. However, it contains a large amount of heavy metal ions and microorganisms which in turn can inhibit the growth of microalgae cells. This scenario led to the development of compost derived from animal manure as a feasible and economic substitute for existing nutrient sources to grow microalgae. It constitutes a copious amount of nutrient elements, cheap, omnipresent, and environmental-friendly, which makes it as a sustainable option for the cultivation of microalgae in the commercial stage. Nevertheless, its full-scale application is limited by several challenges such as transparency problems, variability in nutrient content, selectivity over some microalgae species, and formation of other microorganisms during the composting process as well as nitrogen leakage into the atmosphere. To overcome these limitations, pre-treatment methods such as decolourization, dilution, and zeolite addition have been incorporated and discussed to increase the potential usage of animal manure for large-scale production of microalgae biomass.
... The benefit of algal microorganisms lies in their capacity for rapid growth, the high productivity of lipids (palmitic acid (C16:0), linoleic acid (C18:2) and y-linoleic acid (C18:3)), potential in bioremediation technology and various valuable by-products. The harvesting of microalgae is considered one of the key points in biofuel production, representing minimally 20-30% of the total production costs and limiting production on a commercial and industrial scale [12]. ...
The removal of microalgae represents a problematic part of the water decontamination process, in which most techniques are expensive and non-ecological. In the paper, we focus on the synergistic relationship between microscopic filamentous fungi and algal culture. In the process of decontamination of a model sample containing ammonium ions, efficient biocoagulation, resp. co-pelletization of dried algae Chlorella sp. and Aspergillus niger sensu stricto are shown. The microscopic filamentous fungus species A. niger was added to a culture of an algal suspension of Chlorella sp., where the adhesion of the algal cells to the fungi subsequently occurred due to the electrostatic effect of the interaction, while the flocculation activity was approximately 70 to 80%. The algal cells adhered to the surface of the A. niger pellets, making them easily removable from the solution. The ability of filamentous fungi to capture organisms represents a great potential for the biological isolation of microalgae (biocoagulation) from production solutions because microalgae are considered to be a promising renewable source of oil and fermentables for bioenergy. This form of algae removal, or its harvesting, also represents a great low-cost method for collecting algae not only as a way of removing unnecessary material but also for the purpose of producing biofuels. Algae are a robust bioabsorbent for absorbing lipids from the environment, which after treatment can be used as a component of biodiesel. Chemical analyses also presented potential ecological innovation in the area of biofuel production. Energy-efficient and eco-friendly harvesting techniques are crucial to improving the economic viability of algal biofuel production.
... Drawbacks of dissolved air flotation include the requirement of chemicals for floc formation and breakage of flocs by large bubbles as the size of the bubbles plays a fundamental role in the efficiency of the process. Moreover, dissolved air flotation is not an energy-efficient process (Wiley et al., 2009;Park et al., 2011;Pragya et al., 2013). Fuad et al. (2021) reported that dissolved air flotation is an efficient and cost-effective harvesting technique for Nannochloropsis sp. ...
The feasibility of microalgal biomass as one of the most promising and renewable sources for biofuels production is being studied extensively. Microalgal biomass can be cultivated under photoautotrophic, heterotrophic photoheterotrophic, and mixotrophic cultivation conditions. Photoautotrophic cultivation is the most common way of microalgal biomass production. Under mixotrophic cultivation, microalgae can utilize both organic carbon and CO2 simultaneously. Mixotrophic cultivation depicts higher biomass productivity as compared to photoautotrophic cultivation. It is evident from the literature that mixotrophic cultivation yields higher quantities of polyunsaturated fatty acids as compared to that photoautotrophic cultivation. In this context, for economical biomass production, the organic carbon of industrial wastewaters can be valorized for the mixotrophic cultivation of microalgae. Following the way, contaminants’ load of wastewaters is reduced while concomitantly producing highly productive microalgal biomass. This review will focus on different aspects covering the sustainable cultivation of different microalgal species in different types of wastewaters.
... The three primary products of biomass pyrolysis are char, everlasting gases, and vapours that condense to a dark brown viscous liquid at room temperature. Maximum liquid production occurs at temperatures ranging from 350oC to 500oC [46] . ...
CO2 emission is a burning issue in current time. Carbon dioxide (CO2) is the critical anthropogenic greenhouse gas due to its abundance and its ability to remain in the atmosphere for thousands of years [1]. It is well-known that CO2 emissions contribute to global warming and climate change, which can significantly cause severe impacts and consequences for humans and the environment. CO2 emissions act like a blanket in the air, trapping heat in the atmosphere, and warming up the Earth [2]. This layer prevents the Earth from cooling, and thus raises global temperatures. A typical passenger vehicle emits about 4.6 metric tons of carbon dioxide per year. This assumes the average gasoline vehicle on the road today has a fuel economy of about 22.0 miles per gallon and drives around 11,500 miles per year. Every gallon of gasoline burned creates about 8,887 grams of CO2. Biodiesel is a domestically produced, clean-burning, renewable substitute for petroleum diesel. Using biodiesel as a vehicle fuel increases energy security, improves air quality and the environment, and provides safety benefits. In this paper we will discuss about current carbon emission in china, overview of biomass and their past and present uses, production process of bio diesel from biomass, Limitation of using biodiesel and proposed solution to overcome these challenges.
... The first challenge is separating water from the biomass due to small algal cells of 2-10 μm in length and 2-8 μm in width [100]. The difficulty of developing simple and inexpensive procedures to convert lipids into biodiesel [65,115], which can represent 20-57% of the final biomass cost, is also a bottleneck [1,8]. The cultivation of microalgae is not efficient from the energy point of view and needs more synergies. ...
A review of the potential areas of algal biomass utilization has already been conducted. In addition to lowering the greenhouse effect and contributing to the decrease in the amounts of harmful substances in the air and water, attention has been paid to the possibility of utilizing algal biomass as a feedstock for the production of environmentally friendly products. The circular economy addresses the benefits to the environment, economy and society. The utilization of algal biomass benefits the environment by reducing greenhouse gases emissions as well as water and wastewater treatment, benefits the economy by producing biofuels, and benefits society by producing food, cosmetics, pharmaceuticals, fertilizers and feed for animals.
... For effective lipid extraction, the solvents should a) have high specificity for intracellular lipids, b) be insoluble in water, c) have more significant permeation potential through the cell matrix, d) have a low boiling point, e) be volatile, economical, and innocuous [146]. The solvent extraction method's rationale is the disruption of the hydrogen bond between polar lipids and hydrophobic interaction between non-polar or neutral lipids [147]. The solvent extraction efficiency is determined by the solvents employed and the proportions in which they are used. ...
Recent development in strategies to overcome the environmental adversities are focused mainly on lowering the carbon footprints and to decrease the global temperature rise. Bioprocesses based on microalgae are promising due to a large spectrum of possible products, like platform chemicals, proteins and higher value products that can directly impart a fall in the carbon emission. Another promising approach towards sustainability is the integrated bio refinery cultivation of microalgae for waste water treatment with simultaneous production of fuels (alcohol and biodiesel), high value chemicals (Astaxanthin, Lutein, polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFA)etc.), proteins etc, but the technology readiness level are rather low and therefore are not established. However, for sustainable, economical and feasible bioprocess strategies using microalgae intra and extracellular bio-components extraction and cell wall disruption techniques should be optimized whereas challenges like high energy consumption involving these stages in the process makes it futile. The efficiency of cell disruption techniques and product extraction varies within different microalgae and depends mainly on the growth conditions and cell wall composition. The current review describes the cell wall structure and its composition of green freshwater microalgae such as Botryococccus braunii, Scenedesmus obliquus, Desmodesmus sp., Chlamydomonas reinhardtii, Chlorella vulgaris, Haematococcus pluvialis and marine forms like Dunaliella salina and Nannocholoropsis gaditana. Further, it highlights the green cell lysis technologies to disrupt cell walls and the future perspectives and challenges of algae in integrated wastewater treatment, CO2 capture, and energy-efficient algal cell wall disruption for utilizing microalgae for fuel production is discussed.
... This continuous process produced extracted S. grandiflora bio-oil with solvent and the oil retrieved seed waste. In batch distillation process, the obtained mixture of bio-oil and solvent were heated (20-85 °C) to separate the bio-oil from the solvent as shown in Fig. 1 [13,14]. ...
Oil extraction from crushed Sesbania grandiflora seeds was done by solvent extraction technique using an improved Soxhlet extractor (SE). Three polar (Methanol, Acetone and Isopropanol), three non-polar solvents (hexane, Chloroform and toluene) were used for oil extraction. Characterization techniques like FT-IR, GC/MS were used to study the bio-oil and results were discussed. The extraction parameters like preference of solvents, aging of seeds and extraction time were analyzed to obtain the optimum yield of oil. Basic fuel properties such as saponification value, ash content, fire point, specific gravity, FFA, kinematic viscosity, carbon residue content, flash point and calorific value were determined to examine the bio-oil quality. At optimum condition of 82.6 °C and 3.5 h, with isopropanol as solvent a maximum oil yield of 39.17% was achieved. The physicochemical properties of S. grandiflora oil is compared with karanja oil (Pongamia pinnata). The presence of ester compound has been identified by conducting NMR study.Keywords
Esbania grandiflora
Soxhlet extractorGC/MSFTIRNMRPhysicochemical properties
... 26 O processamento do óleo da microalga é basicamente o mesmo empregado nos processos com os óleos vegetais e gorduras animais; porém, o isolamento do óleo é realizado, após secagem do precursor, via extração com solvente, visto que, nas microalgas, ao contrário do usual em outros precursores, a localização dos lipídios é intracelular. 87 O SAF obtido, denominado HC-HEFA-SPK, foi limitado a um máximo de 10% nas blendas com QAV convencional. Atualmente, o biocombustível é suprido regularmente para voos partindo do Aeroporto Internacional de Tóquio. ...
... As the name suggests, microfiltration is used for harvesting smaller algal cells ranging from 0.1 to 10 mm (Li et al., 2011), whereas macro-filtration is used for larger cell size, particularly to filter flocs (Mathimani and Mallick, 2018). A recovery of about 70%À89% of freshwater 163 8.5 Life cycle assessment of wastewater treatment by microalgae algae is obtained through tangential flow filtration (Pragya et al., 2013). Despite microalgal cells of very low densities can be harvested by this method, membrane filtration is not commonly applied in large-scale processes . ...
Life Cycle Assessment (LCA) is a widely used tool for estimation of environmental footprint of any products, technologies and services, throughout its whole lifecycle from cradle to grave. It is a standardized decision support system, for quantifying the different environmental impact categories and deciding upon the sustainability of each system employed. The use of LCA tools for wastewater treatment and their impact assessment is started very recently. In wastewater treatment the LCA tools compile and evaluate the inputs and the outputs, and consider their potential environmental impacts associated with the operation of the system for all types of wastewater treatment plants either for conventional or algal ponds, throughout its whole process chain. The LCA studies generally follow ISO standards (International Organization for Standardization) with baseline framework consisting of four phases’ viz. goal and scope determination, life cycle inventory analysis (LCI), life cycle impact assessment (LCIA) and interpretation of results. The inventory analysis accumulate the data or the database for analysis, using specific criteria or data quality matrices and the impact assessment is carried out with the help of different type of softwares viz. SimaPro®, Gabi®, OpenLCA®, Umberto® etc. The impact assessment transforms the mathematical data to environmental effect equivalent via the factor multiplication. The LCA studies has validated that the wastewater treatment with microalgae comparing to the conventional, can significantly reduced the negative environmental impacts, as well as the system has the advantage on low cost of operation, the possibility of recycling the nutrients in wastewater to high value products, reducing the emissions by absorption of CO2 present in the flue gases and the discharge of oxygenated effluent into the water body.
... Owing to the need to reduce greenhouse gas emissions and the ever-increasing energy demand, biofuels, such as bioethanol, as an alternative energy source, are attracting worldwide attention (Pragya et al. 2013;Rocha et al. 2014). Biofuel is a multiple objective sustainable resource that promises to substitute fossil fuels with energy from agricultural and forestry sources while providing a range of other benefits (Lovett et al. 2011). ...
Corn fiber, a by-product from the corn processing industry, mainly composed of residual starch, cellulose, and hemicelluloses, is a promising raw material for producing cellulosic ethanol and value-added products due to its abundant reserves and low costs of collection and transportation. Now, several technologies for the production of cellulosic ethanol from corn fiber have been reported, such as the D3MAX process, Cellerate™ process, etc., and part of the technologies have also been used in industrial production in the United States. The ethanol yields range from 64 to 91% of the theoretical maximum, depending on different production processes. Because of the multicomponent of corn fiber and the complex structures highly substituted by a variety of side chains in hemicelluloses of corn fiber, however, there are many challenges in cellulosic ethanol production from corn fiber, such as the low conversion of hemicelluloses to fermentable sugars in enzymatic hydrolysis, high production of inhibitors during pretreatment, etc. Some technologies, including an effective pretreatment process for minimizing inhibitors production and maximizing fermentable sugars recovery, production of enzyme preparations with suitable protein compositions, and the engineering of microorganisms capable of fermenting hexose and pentose in hydrolysates and inhibitors tolerance, etc., need to be further developed. The process integration of cellulosic ethanol and value-added products also needs to be developed to improve the economic benefits of the whole process. This review summarizes the status and progresses of cellulosic ethanol production and potential value-added products from corn fiber and presents some challenges in this field at present.
... Microalgal biomass contain high quantity of carbohydrate; thus, this could be a potential feedstock for bioethanol production (Dhandayuthapani et al., 2021). Their starch units can be converted into sugar moieties in the presence of enzymes or some mechanical equipment and then the conversion is effectively metabolized by the yeast (Saccharomyces cerevisiae/Zymomonas mobilis) (Pragya et al., 2013) which is subsequently purified from the system through distillation followed by dehydration. Bioethanol can be produced by means of dark/yeast fermentation. ...
Scientists are grabbing huge attention as well as consciousness on non–renewable energy sources for the global energy crises because of gradual increase in oil price, fast depletion or low availability of resources, and the release of more toxic–gases (CO2, SOx, NxO) during exhaustion, etc. Due to such hitches, the key need is to find alternative biofuels or feedstocks to replace fossil fuel energy demands worldwide. Currently, microalgae have become intrigued feedstock candidates (3rd generation source of biofuel) to replace nearly 50–60 % of fossil fuels due to high production of biomass and oil, mitigating CO2 and wastewater remediation. The present work demonstrated the current developments and future perspectives on large–scale algal cultivation strategies for the biorefinery economy. In addition, various advanced cultivation techniques adopted for enhanced biomass production and cost-effective methods for bioenergy production were detailly discussed.
... It is either solely used for lipid extraction or can be incorporated with mechanical/cell disruption processes as summarized in Table 6. Lipid recovery using the chemical cell disruption is attractive due to its low energy demand and convenience in terms of usage, storage, and transportation [206]. Different organic solvents such as methanol, hexane, chloroform, dichloromethane, and their mixtures have been commonly utilized for lipid extraction considering the polarity of lipid types [207]. ...
High lipid content and excellent CO 2 fixation capability of microalgae by photosynthesis have made microalgal biodiesel (BD) a promising carbon-neutral fuel. Nonetheless, the commercialization of BD has not yet been realized because of expensive and energy-intensive cultivation, pretreatment, and BD conversion processes in reference to 1 st generation BD production. To resolve the issues, this study comprehensively reviewed the current technical developments of microalgal BD production process and suggested promising future studies. Current microalgal BD production processes highly rely on the processes developed from 1 st generation BD process, namely base-catalyzed transesterifications. However, the base-catalyzed suffers from saponification reaction and low production yield due to high water and free fatty acid contents in microalgae. Vigorous pretreatments such as dewatering, drying, esterification of free fatty acid, and purification are required for high yield of microalgal BD production, making this process economically not attractive. As efforts to construct new transesterification platform, novel approaches tolerant to impurities such as thermally induced non-catalytic transesterifications were suggested. The thermally induced reactions allowed in situ conversion of microalgal lipid into BD (≥ 95 wt. % yield) within 1 min of reaction at ≥ 350 C. This process resists to presence of water and free fatty acids and does not require lipid extraction process. To make this process more promising, it was suggested lowering reaction temperature for thermally induced transesterifications. In addition, pilot study, in-depth life cycle assessment, and economic analysis were suggested to assess economic viability and environmental impacts.
... The lipid content is also considerably higher under certain growth regime, like nitrogen-deprived conditions, depending on species (Rodolfi et al., 2009). These characteristics make the conversion of algae into valuable products, such as biofuel, feasible (discussed in detail in Section 8), but these processes still require many steps to be commercially viable (Bošnjaković and Sinaga, 2020;Ogbonna and Nwoba, 2021;Pragya et al., 2013). The common cell structure of mi- croalgae (Beer et al., 2009;Pignolet et al., 2013;Zhang et al., 2019) is illustrated in Fig. 4. ...
Microalgae have been identified as one of the new feedstocks for renewable energy production. The conversion of microalgae into various valuable products has also been increasing in the last decade. Microalgae harvesting, one of the most important stages in microalgae production, has been studied and reviewed by many researchers. However, most harvesting methods still utilize chemicals during the process, which make harvested biomass not directly ready for food/feed production and pharmaceutical-related processes. Biocoagulants/bioflocculants are emerging compounds that can be used during the harvesting of microalgae because their existence does not introduce toxicity in the harvested biomass. Considering its potential to produce ready-to-use biomass, biocoagu-lants/bioflocculants have a bright future in microalgal biomass production processes. This review article highlights simultaneous wastewater treatment and microalgal biomass production as an emerging method in accommodating a circular economy paradigm. This paper juxtaposes the utilization of chemical-based coagulants/floc-culants and biocoagulants/bioflocculants in harvesting microalgae. Biodegradability, effectiveness, harvested biomass characteristics, and potential of medium reuse are emphasized in the discussion. The agglomeration mechanisms of microalgae during harvesting, recent advances in the microalgal biomass conversions, and future challenges related to the utilization of biocoagulants/bioflocculants are also described in detail. Microalgae harvesting by using biocoagulants/bioflocculants is a feasible and promising environmentally friendly technology for microalgal biomass production.
... In general, microalgae with tiny cells (less than 10 µm) are not appropriate for harvesting via the flotation technique. In such a case, the pre-coagulation is usually required to form aggregates with 10.0 nm or more to facilitate its recovery by flotation [103]. Relatively short operation times, lower initial equipment costs, easy operating procedures, low space requirements, and relatively high harvesting efficiency are the main advantages of the flotation process. ...
Biodiesel is considered a promising alternative to conventional fuels in response to increasing global energy demands, and it also contributes to reduced environmental emissions. Microalgae is a potential resource for qualitative biodiesel production due to its high specific growth rate, ability to accumulate significant quantities of intracellular lipids, potential to utilize wastewater as a cultivation medium and less cropland requirement compared to conventional oil crops. However, the commercialization of microalgae biodiesel largely depends on the energy and cost-efficiency of the microalgae cultivation system. Moreover, optimization of cultivation systems and strain improvement in microalgae are promising strategies to enhance the growth rate and lipid productivities. This review provides a comprehensive overview of the various microalgae cultivation systems, focusing on the recent developments, including the genetic engineering perspectives in improving microalgae growth and lipid productivity, techno-economic analysis, and real case studies for microalgal biodiesel production. The review paper also summarizes the microalgae harvesting and lipid extraction processes, transesterification methodologies, quality of microalgae biodiesel, and environmental concerns associated with the large-scale production of microalgae biodiesel.
... Benzene is a carcinogen and can lead to explosion hazard also. Hexane is less efficient than chloroform which is less toxic and has low affinity towards non lipid contaminants [9]. Bligh and Dyer's method is used for both dry and wet mode of oil extraction [10] where the ratio of chloroform/methanol is maintained around 2:1. ...
Unearthing new sustainable and economically viable sources for biofuel production which do not affect the environment is a dire need of the hour. Microalgae is one such promising source due to its high lipid content, productivity, and carbon neutrality. Identification of appropriate strain and process optimization decides the biomass productivity, nutrient value, and oil content which are the major factors for commercialization. In the present work, mass cultivation of halophilic Aphanothece halophytica in raceway ponds was optimized by using organic and inorganic nutrients by using design of experiments. Organic flocculant, neem plus was successfully adapted for harvesting the biomass and oil extraction was done with solvent methodology. A maximum lipid yield of 29.3% was obtained on wet basis, when the reaction temperature, reaction time, biomass-to-solvent ratio and mixing intensity were kept at 68 ºC, 190 min, 9:1, and 300 rpm respectively. Similarly, on dry basis, a lipid yield of 27.5% was reported when the reaction temperature, reaction time, biomass-to-solvent ratio and mixing intensity were maintained at 68 ºC, 190 min, 12:1, and 300 rpm respectively. GC–MS analysis of the lipid was done to appropriate the combination of fatty acid for enhancing the biofuel production.
... Although plant extraction of this essential oil is useful as a feed additive for large-scale production of aquaculture, essential oil extraction was performed from a different source of the plant. Pragya et al. (2013) reported that microalgaebased sources could represent an alternative and may be renewable in terms of essential oils, biofuels, and bioethanol. Afterward, a variety of essential oils were extracted from the branches of Thuja occidentalis L. and Abies Balsamea (L.) Mill: 80% of cedar leaf oil, 15% of extracted α-pinene and β-pinene in balsam fir oil, and 40% extraction of dietary essential oil collected from sweat orange (Citrus sinensis) and bitter lemon (citrus lemon) peel improved the performance of Nila tilapaia and yielded health benefits (Mohamed et al., 2021;Palariya et al., 2019). ...
Aquaculture is one of the most developing sectors worldwide, and it contributes to enhancing the global production. The application of natural feed additives is an external source of aquaculture production due to the ban on antibiotics as a growth promotor as well as their harmful effects on the host, and cost‐effectiveness. Even consumer concerns those antibiotics can cause the water quality and growth instead of growth promoters of natural feed additives to improve the aquaculture production. The role of feed additives is to control the pathogenic microbes, enhance their growth, immune stimulation, and ensure water quality. For these reasons, several types of dietary feed additives are used in the livestock sector, such as essential oil, essential fatty acid, probiotics, prebiotics, symbiotic, and exogenous enzymes, but here, the feed additives of probiotics' most relevant applications in the aquaculture field in terms of modes of action such as strengthening the immune response, competition of binding sites, production of antipathogenic substances, and growth performance competition for nutrition are described. These additives are considered to be useful for their specific medicinal properties and eco‐friendly metabolism in the digestive system. This review describes the role of various feed additives and their relevance to aquaculture production quality. Schematic diagram of natural feed additives in the aqua sector.
... Various inorganic or organic compounds containing polyvalent metal ions, such as Al +3 or Fe +3 , can be used as flocculants to improve the harvesting efficiency (Milledge and Heaven, 2013). However, the use of flocculants frequently faces the risk of biomass contamination by hazardous metals (Pragya et al., 2013;Prochazkova et al., 2015). This drawback can be eliminated to a certain degree by using biodegradable flocculants, such as chitosan, which can biologically degrade and does not present a risk to the microalgae biomass (Zhou et al., 2016). ...
Conventional flocculants, commonly used to improve harvesting efficiency, can contaminate the broth and cause microalgae not suitable for food or feed production. In the present study, Pleurotus ostreatus, an edible fungal strain, was developed to improve the harvesting efficiency of microalgae. The results show that Pleurotus os-treatus pellets cultured under 100 rpm agitation resulted in higher harvesting efficiency than pellets cultured under 0 rpm and 150 rpm agitation. Lower pH of the Chlorella sp. suspension resulted in higher harvesting efficiency. The maximum recovery efficiency reached 64.86% in 150 mins. The above process could be used to achieve low cost, flocculant-free harvesting of microalgae as feedstock for feed or food production.
This comprehensive book approaches sustainability from two directions, the reduction of pollution and the maintaining of existing resources, both of which are addressed in a thorough examination of the main chemical processes and their impact. Divided into five sections, each introduced by a leading expert in the field, the book takes the reader through the various types of chemical processes, demonstrating how we must find ways to lower the environmental cost (of both pollution and contributions to climate change) of producing chemicals. Each section consists of several chapters, presenting the latest facts and opinion on the methodologies being adopted by the chemical industry to provide a more sustainable future. A follow-up to Materials for a Sustainable Future (Royal Society of Chemistry 2012), this book will appeal to the same broad readership - industrialists and investors; policy makers in local and central governments; students, teachers, scientists and engineers working in the field; and finally editors, journalists and the general public who need information on the increasingly popular concepts of sustainable living.
Algler; güneş ışığı, su ve karbondioksiti biyokütleye dönüştürebilen hücre fabrikaları olarak bilinirler. Yaygın olarak büyüklüklerine göre sınıflandırılan algler (mikroalgler ve makroalgler), çok fazla çeşitlilik gösterebilen heterojen organizma gruplarıdır. Algler türe, yetiştiği bölge, mevsim, hasat şekli, depolama koşulları ve gıda işleme tekniklerine bağlı olarak değişiklik göstermek ile birlikte, yapılarında yüksek miktarda lipit (%20-80), protein (%39-71) ve diyet lifi içermektedir. Ayrıca sterol, vitamin, pigment, α-tokoferol, β-karoten, glutatyon, askorbik asit, flavonoidler, hidrokinonlar, fikosiyaninler, prolin, fenolik bileşikler, poliaminler ve özellikle çoklu doymamış yağ asitleri (ω-3 yağ asitleri) içerikleri nedeniyle iyi bir besin kaynağı olarak kabul edilmekte ve fonksiyonel gıda üretiminde kullanılmaktadır. Alglerin barındırdıkları bu değerli biyoaktif bileşenler sayesinde antioksidan, antimikrobiyal, antiinflamatuar ve antikarsinojen etkiye sahip oldukları düşünülmektedir. Uzun yıllardır insan diyetinin bir parçası olarak olan alglerin tüketiminin en fazla görüldüğü ülke Japonya’dır. Alg üretimi konusunda ise Çin ve Endonezya önderlik etmektedir. Algler, gıda olarak kullanımının yanı sıra, gıda takviyesi üretiminde, hayvan yemi olarak, kozmetik ve ilaç endüstrisinde, biyoenerji ve biyoyakıt üretimi sırasında hammadde olarak tercih edilmektedir. Algler azot sabitleyici biyogübreler olarak kullanımlarının yanı sıra, aynı zamanda sera gazı emisyonunun azaltılması ve biyolojik iyileştirme uygulamalarında kullanılmaktadır. Bu çalışmada alglerin bileşimi, özellikleri, sınıflandırılmaları, üretimi ve hasatı, ayrıca alg yağı hakkında bilgi verilmiştir. Çalışmanın amacı sürdürülebilir, alternatif, yenilikçi ve daha iyi değerlendirilme potansiyeli oldukça yüksek olan bir kaynağa dikkat çekmek, özellikle bir ω-3 kaynağı olarak alglerin tanıtılması ve alg kullanımı ile zenginleştirilmiş gıdaların takviye edici olarak insan diyetinde yer alması konusunda bilgi sunmaktır.
The multi-cellular and filamentous cyanobacterium Spirulina sp. has gained substantial predominance in the health sector, food industry, and aquaculture in contemporary times. It has a very high content of macro and micronutrients, essential amino acids, proteins, lipids, vitamins, minerals, and anti-oxidants. In recent years, Spirulina sp. has garnered enormous attention from research fraternity as well as industries as a flourishing source of nutraceutical and pharmaceuticals. It is considered a complete food supplement to combat against malnutrition deficiencies. In developing countries like India, malnutrition is a renowned social challenge that can be defeated by the supplement of Spirulina sp. products in the diet. The commercial cultivation of Spirulina sp. that can be converted into consumable forms (tablets/granules) can be an economic enterprise in India. Such agribusiness has been commenced by an agripreneur under Agri-Clinics and Agri-Business Centers (ACABC) scheme. The agripreneur was interviewed and informed that this agribusiness had a good turnover with low capital investment, and also providing employment opportunities to others.KeywordsCyanobacterium agri-businessSuper food
Spirulina
Agri-businessFood industry
Microalgae is a third-generation biomass source that can potentially be used as a raw material for bioethanol production. Microalgae is a viable alternative energy source to substitute or complement fossil fuels based on the disadvantages related to first- and second-generation biofuels. Bioethanol from microalgae sources does not compete with food needs. In addition, third-generation biomass can be grown in aquatic environments and has large-scale CO2 requirements. This review article compiles literature focusing on the production of microalgal bioethanol and summarises the advantages, disadvantages, main features and key aspects for each process. The production of bioethanol is achieved through pretreatment to break down the cell wall, which is followed by saccharification of carbohydrates and fermentation of suitable sugars. An effective pretreatment should be simple, have less chemical consumption, and have low energy demand so that production costs can be reduced. Producing bioethanol by fermentation can be performed in many ways, such as separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). The SSF process is more economical, because the combination of hydrolysis and fermentation reduces production costs. The results of the comparison of hydrolysis methods show that enzymatic hydrolysis can potentially be applied to the production of bioethanol because of its affordable economic cost and less negative impact on the environment. Economic reasons, such as the final yield of ethanol products using this method, are higher than other pretreatments. Moreover, this method requires low energy, lack of chemicals and mild environmental conditions.
Supply of energy and quality of water are the two major crunches humans are struggling with in the last decade. The global population at present demands healthy food items followed by efficient energy supply, potable drinking water, and an environment with reduced CO2 levels in order to ensure social and environmental safety. Treatment of the polluted water is one of the biggest challenges nowadays as the contaminated water bodies render water unsuitable for human consumption. In the developing countries, pollution of water by organic contaminants, heavy metals, sewage, and eutrophication is decreasing the human lifespan by increasing the risk of deadly diseases. Researchers all over the world are trying their best to convert the biowaste into bioenergy and one such approach is treatment of wastewater by microalgae in order to produce biofuels. Microalgae can thrive in diverse environments ranging from freshwater to polluted wastewaters. They are ecologically important as their structure and metabolic reactions are comparable to the higher plant species. They can utilize inorganic and organic matter from different types of wastewaters for biomass conversion that can be used to generate biofuel. Selection of microalgal species, wastewaters, and pretreatment methods are of prime importance in order to generate biofuel. This chapter focuses on the algal biofuel production from municipal wastewaters.
Technological improvements in dietary supplements and nutraceuticals have highlighted the significance of bioactive molecules in a healthy lifestyle. Eicosapentaenoic acid and Cervonic acid (DHA), omega-3 polyunsaturated fatty acids seem to be famed for their ability to prevent diverse physiological abnormalities. Selection of appropriate pretreatments and extraction techniques for extraction of lipids from robust microalgae cell wall are very important to retain their stability and bioactivity. Therefore, extraction techniques with optimized extraction parameters offer an excellent approach for obtaining quality oil with a high yield. Oils enriched in omega-3 are particularly imperiled to oxidation which ultimately affects customer acceptance. Bio active encapsulation could be one of the effective approaches to overcome this dilemma. This review paper aims to give insight into the cultivation methods, and downstream processes, various lipid extraction approaches, techniques for retaining oxidative stability, bioavailability and food applications based on extracted or encapsulated omega-3.
With growing concern about fossil fuel combustion and its environmental impact, a significant amount of research is being conducted to develop alternative renewable energy sources. Microalgae can be considered a feedstock for biofuel production in this regard due to their inherent advantages. This is because microalgae have a high organic carbon density and a rapid growth rate in non-arable lands, in addition to their ability to capture CO2 and treat wastewater. Additionally, microalgae contain a high concentration of oils and starches, making them an excellent source of high-quality biofuel. This article presents a critical review with a particular emphasis on the utilization of microalgae biomass for the production of high-quality biofuels. This review aims to provide an up-to-date overview of methods for converting algal biomass into a variety of biofuel products, including biodiesel, syngas, biogas, and bioethanol. The article highlights various aspects of biomass analysis, including a) dry weight, b) carbon content, c) lipid content, and productivity. Additionally, this review discusses novel technologies for lipid extraction and lipid analysis in the context of biodiesel production. This review focuses on the most advanced processes for the production of biofuels and biodiesel, reaction kinetics, homogeneous, heterogeneous, and enzymatic transesterification reactions.
Global population growth rate accelerating earth ecosystem disturbance and increasing resource scarcity, malnutrition and poverty. These events challenge socio-economic development of each country and obligate scientific communities to develop such novel approaches to overcome this burden, which not only provide a healthy diet but also engage people in setting up their own business. Therefore, microalgae Spirulina is the one of the emerging food source with rich protein content and other nutritional components in adequate amount with diverse health benefits. The small scale investments in microalgae biomass production, familiarizing nutraceutical values and convert in consumable forms is the interesting agribusiness with diversified profits and popularization. Spirulina production strategies can be conventional and low-cost effective technologies. These techniques also help in designing new innovative possibilities in modifications and enhancements in the existing agriculture products processing strategies for their better use in different industries. Although most of communities are aware about agribusiness strategies of Spirulina but still it is in one the demanding and upcoming bright sector. This article reveals the methods of mass production of Spirulina and their significant role in agriculture as well as industrial.
A novel gravity sedimentation - forward osmosis (G-FO) hybrid reactor was built up for separating and concentrating the biomass from the algal-rich water (microalgal dewatering). The extracellular organic matter (EOM) from Chlorella vulgaris (C. vulgaris) was divided into dissolved EOM (dEOM) and bound EOM (bEOM). Water flux, flux recovery rate and moisture content (MC) were investigated. Through sedimentation rate, zeta potential and hydrophilicity/hydrophobicity to analyze the experimental results. Scanning electronic microscopy (SEM) was used to observe the different morphologies of accumulated algae cells and EOM on the surface of the membrane. The results showed that cell + bEOM solution had the fastest sedimentation rate and fewest negative charge, so the pollutants accumulated more easily on the membrane surface, resulting in the highest flux decline. Its algal cake layer was the densest from the view of SEM. Cell + bEOM + dEOM solution had the lowest flux decline and the cake layer was the loosest. Cell + bEOM solution had the most severe irreversible fouling and the lowest flux recovery rate (FRR). The membrane fouling of cell solution was lower than that of cell + bEOM + dEOM solution, and the FRR of cell solution was almost 100%. According to the nonionic macro-porous resin fraction results of EOM, cell + bEOM + dEOM solution contained more hydrophilic components, resulting in the lowest MC. On the contrary, cell + bEOM solution showed the highest MC, which contained more hydrophobic components. Effects of bEOM and dEOM on microalgae dewatering performance of a novel gravity sedimentation - forward osmosis (G-FO) hybrid system were investigated, which provided a theoretical basis for large-scale application of FO technology for microalgae dewatering.
Coccomyxa subellipsoidea, a single-cell, eukaryotic green algae thriving in temperate climates, is capable of lipid accumulation in excess of 25 % (dry weight). At the front of agroeconomic challenges facing algae for the production of lipids in bioproduct development is how to effectively initiate lipid accumulation and harvesting with economically viable production costs. Co-culturing of the denitrifying bacteria Pseudomonas denitrificans with C. subellipsoidea increased total algal lipids levels, particularly neutral lipids when compared to C. subellipsoidea grown alone in BBM. Total lipid increased nearly two-fold to 16 % (dry weight); triacylglycerol (TAG) increased to 12.5 %. These findings suggest bacterial signaling induced lipid accumulation under nutrient rich condition coincident with increased biomass generation, especially in suboptimal condition using raw wastewater for co-cultures. These findings support a novel signaling mechanism originating from P. denitrificans that results in lipid accumulation in C. subellipsoidea and highlights an underexplored opportunity for an increased agroeconomic viability.
The method of collecting microalgae using fungal mycelium pellets has attracted widespread attention because of its high efficiency and simplicity. In this study, the interaction in FMSS was explored using Aspergillus fumigatus and Synechocystis sp. PCC6803. Under the conditions of 25-30 °C, pH of 5.0, 160 rpm, a light intensity of 1000 lx, light to darkness ratio of 6:18 h, and glucose concentration of 1.5 g/L, the FMSS had the highest biomass and recovery efficiency. SEM, TEM, and Zeta analysis showed that microalgae can be fixed on the surface of fungal mycelium pellets by the electrostatic attraction (amino, amide, phosphate, hydroxyl, and aldehyde groups) of EPS. The N cycling and CO2-O2 cycling promoted the synthesis of amino acids and provided a guarantee for gas exchange, and the intermediate metabolites (CO3²⁻ and HCO3⁻/H2CO3) satisfied the metabolic activities. The microalgae and fungi worked in coordination each other, which was the mutualistic symbiosis.
In this study, an iron–aluminum composite (IAC) coagulant was synthesized from bauxite residue, and its applicability was investigated by harvesting biomass of Chlorella vulgaris (C. vulgaris). Bauxite residue is not environmentally friendly due to its high alkalinity that could pose a risk for living organisms. In this study, the conversion of the bauxite residue into IAC coagulant was done, which delivered safe utilization of bauxite residue to reduce its deteriorating impact on the environment. The prepared IAC coagulant was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, and ICP-MS (inductively coupled plasma mass spectrometer). Concurrently, the applicability of the IAC was examined by harvesting the biomass of a freshwater microalgae: C. vulgaris from culture media. Several parameters (dosage, settling time, pH, biomass concentration, and age of culture) were also optimized to achieve the maximum efficiency of IAC coagulant. It was found that the 0.92 g biomass of C. vulgaris can be effectively removed from a liter of culture media by using 0.2 g of IAC in 120 min of contact time, leaving no residual metals (aluminum and iron) in aqueous media. This study showed that IAC coagulant is an efficient coagulant due to simple steps of synthesis, its high efficacy, low dose requirements, relatively short settling time, its integrity with cells, and generating no secondary pollutions.
Exopolymeric substances that are also known as extracellular polymeric substances, extracellular polysaccharides, exopolymers, and exopolysaccharides are produced by various microorganisms. They primarily include polysaccharides, lipids, nucleic acids, and proteins. Exopolymeric substances protect microorganisms from various environmental stresses. Exopolymeric substances have unique characteristics. Some of the functional properties of them include adhesion, aggregation, binding activity, energy and nutrient source, water retention, and sorption. One of the exopolymeric substances is fungal exopolymeric substances. The fungal exopolysaccharides are pullulan, scleroglucan, fungal β-glucans, botryosphaeran, and others. The fungal exopolymeric substances are valuable products because of their different application areas such as industries of medical, cosmetic, food, wastewater treatment and agriculture.
Microalgal biomass has garnered attention as a renewable and sustainable resource for producing biodiesel. The harvesting of microalgal biomass is a significant bottleneck being faced by the
industries as it is the crucial cost driver in the downstream processing of biomass. Bioharvesting
of microalgal biomass mediated by: microbial, animal, and plant-based polymeric flocculants has
gained a higher probability of utility in accumulation due to: its higher dewatering potential, less
toxicity, and ecofriendly properties. The present review summarizes the key challenges and the
technological advancements associated with various such harvesting techniques. The economic
and technical aspects of different microalgal harvesting techniques, particularly the cationic polymeric flocculant-based harvesting of microalgal biomass, are also discussed. Furthermore, interactions of flocculants with microalgal biomass and the effects of these interactions on metabolite
and lipid extractions are discussed to offer a promising solution for suitability in selecting the
most efficient and economical method of microalgal biomass harvesting for cost-effective biodiesel production.
Microalgae are unicellular organisms that have been used in wastewater treatment. A majority of wastewater contains nutrient components like phosphates and nitrates along with organic compounds that favour biofuel recovery. It has been reported that various methods of wastewater systems have been employed such as source-separated systems, activated carbon, hybrid systems and immobilized reactors and simultaneous resource recovery. In this review, we will critically examine the state-of-the-art algal biotechnology for wastewater treatment, especially concerning its potential for valorization. We will also discuss the recent advances in microalgae systems for wastewater treatment coupled with the bioproduction of value-added products.
The etiology of Crohn's disease, which is a chronic inflammatory condition that potentially involves any location of the alimentary tract from the mouth to the anus, is unknown. However, there is strong evidence that vascular damage could play a role in the pathogenesis of Crohn's disease. Crohn's disease is mediated by multifocal gastrointestinal infarctions, which occur at an early stage in the disease process. Persistent activation of coagulation in patients with Crohn's disease has been shown. In contrast, hemophilia is an inherited disorder of coagulation. The deficiencies of clotting factors usually involve occult or overt bleeding. The pathogenic mechanisms of Crohn's disease and hemophilia are incompatible. An association between Crohn's disease and hemophilia has not been reported in Korea. We managed 21- and 33-year-old men with Crohn's disease associated with hemophilia, who presented with hematochezia.
In this study, we present the activities of Al2O3 supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50°C. We found that pure CaO and MgO were not active and CaO/Al2O3 catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80wt.% CaO/Al2O3 catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30.
Effects of nitrogen source and concentration as well as lipid extraction method on the lipid yield of autotrophic Scenedesmus dimorphus and heterotrophic Chlorella protothecoides were studied. Three concentration levels of nitrate, urea and glycine/yeast extract as the nitrogen source were investigated. The highest lipid yield of S. dimorphus in the 17-d autotrophic culture was 0.40 g/L from the 1.8 g/L urea medium, and the maximum lipid yield of C. protothecoides in the nine-day heterotrophic culture was 5.89 g/L from the 2.4 g/L nitrate medium. Four different cell disruption methods— bead-beater, French press, sonication and wet milling— were studied for their effectiveness in solvent extraction of algal lipids from S. dimorphus and C. protothecoides. Wet milling followed by hexane extraction was most effective for S. dimorphus lipid extraction, whereas bead-beater disruption followed by hexane extraction was best for C. protothecoides.. Effect of nitrogen and extraction method on algae lipid yield. Int J Agric & Biol Eng, 2009; 2(1): 51－57.
Twelve salts were tested for their ability to coagulate microalgae cells in cultures of Chlorella minutissima. The final aim was to develop an easy and efficient approach for harvesting microalgae biomass in dense cultures. Aluminum,
ferric, and zinc salts coagulated C. minutissima cultures, while optimum concentration was 0.75 and 0.5gL−1 for sulfate and chloride salts, respectively. Aluminum salts were most efficient, but caused some cell lysis, which may render
this approach inappropriate in some cases. Ferric and zinc salts were ranked second and third, respectively, according to
their culture cell-coagulation efficiency. Ferric salts caused a change in the color of the cells, mainly at concentrations
higher than 1gL−1. Zinc salts were less harmful for the microalgal cells, but an additional problem was observed with cell aggregates adhering
to the walls of the glass test tubes. Selection of the appropriate coagulant is related to the purpose of the coagulation
process.
KeywordsAluminum salts-Ferric salts-Flocculation-Microalgae-Zinc salts
The high-energy input for harvesting biomass makes current commercial microalgal biodiesel production economically unfeasible. A novel harvesting method is presented as a cost and energy efficient alternative: the bio-flocculation by using one flocculating microalga to concentrate the non-flocculating microalga of interest. Three flocculating microalgae, tested for harvesting of microalgae from different habitats, improved the sedimentation rate of the accompanying microalga and increased the recovery of biomass. The advantages of this method are that no addition of chemical flocculants is required and that similar cultivation conditions can be used for the flocculating microalgae as for the microalgae of interest that accumulate lipids. This method is as easy and effective as chemical flocculation which is applied at industrial scale, however in contrast it is sustainable and cost-effective as no costs are involved for pre-treatment of the biomass for oil extraction and for pre-treatment of the medium before it can be re-used.
Biodiesel is considered a promising replacement to petroleum-derived diesel. Using oils extracted from agricultural crops competes with their use as food and cannot realistically satisfy the global demand of diesel-fuel requirements. On the other hand, microalgae, which have a much higher oil yield per hectare, compared to oil crops, appear to be a source that has the potential to completely replace fossil diesel.
Microalgae oil extraction is a major step in the overall biodiesel production process. Recently, supercritical carbon dioxide (SC-CO2) has been proposed to replace conventional solvent extraction techniques because it is nontoxic, nonhazardous, chemically stable, and inexpensive. It uses environmentally acceptable solvent, which can easily be separated from the products. In addition, the use of SC-CO2 as a reaction media has also been proposed to eliminate the inhibition limitations that encounter biodiesel production reaction using immobilized enzyme as a catalyst. Furthermore, using SC-CO2 allows easy separation of the product.
In this paper, conventional biodiesel production with first generation feedstock, using chemical catalysts and solvent-extraction, is compared to new technologies with an emphasis on using microalgae, immobilized lipase, and SC-CO2 as an extraction solvent and reaction media.
The three-dimen sional laser mapping technology with the unique advantage of high precision and high efficiency is widely used in many fields such as engineering construction, and three-dimensional measure and so on. First, the application of the mapping technology by vehicle-borne lidar and its development in foreign countries were introduced. Second, a method, which syncretized the three-dimensional laser scanning technology and the position and pose confirming technology was presented to achieve the road mapping. The main contents included working process, measuring principle, system compostion, key technique and resolving methods. And the detailed testing methods and the results based on an engineering sample were provided. Finally errors of the results were analyzed. Experimental results show that the mobile mapping technology by vehicle-borne lidar can obtain the three-dimensional information of targets, which is accurate enough to meet the demand of road mapping.
The purpose of this study was to explore efficient methods of harvesting the microalga Phaeodactylum tricornutum. Natural sedimentation experiments, performed at different light and temperature conditions, did not yield significant improvements in efficiency even after 1 week. When alkalinity-induced flocculation was performed, both the flocculation efficiency and the concentration factor dramatically improved at pH = 9.75 (0.5–0.7 units over the original pH of the culture) after 10 min settling time. Sedimentation rates are documented at pH ranging between pH 9.75 and 11.0. The results of the application of two conventional flocculants used in wastewater treatment, polyaluminium chloride and aluminium sulphate, are also presented. Chitosan was also used as a natural flocculating agent to improve possible contamination problems in the downstream process. pH was adjusted in order to determine optimum flocculation efficiency of chitosan in combination with a high concentration factor. Satisfactory results were found with chitosan at an adjusted pH of 9.9 using concentrations as low as 20 mg L−1, after testing a flocculant range of 5–200 mg L−1.
In the present study, the use of immobilization technology to cultivate microalgae in entrapped matrix gel beads was demonstrated. Since the gel beads are denser in water, the beads can be easily collected through simple filtration method and hence, simplifying the overall separation process. Various parameters were investigated to optimize the growth rate of immobilized microalgae and the optimum conditions were obtained as: alginate to microalgae volume ratio of 0.3, Ca2+ concentration of 2%, organic nutrients concentration of 50 mL (equivalent to 13.09 mg/L nitrate), initial culture pH of 4 and photoperiod of 24 h. Using this optimum culture condition, 0.50 mg biomass/bead was attained on the 10th day of cultivation. Apart from that, this study also attempted to co-immobilize nutrients into microalgae beads in order to minimize free cell culture (microalgae cells that are released into the culture medium due to rupturing of beads) and to reduce water consumption. Through this approach, it was found that microalgae biomass yield increased to 0.67 mg/bead within a shorter culturing time (5 days) with insignificant amount of free cell culture detected. Furthermore, lipid extracted from immobilized microalgae biomass has high potential for biodiesel production due to the similarity of fatty acid profile with other oil bearing crops.
In this study different methods were applied for lipids extraction from the dry biomass of Chlorella pyrenoidosa. The survey was carried under different conditions seeking comparative assessment of extraction methods. The method using chloroform:methanol (2:1 v/v) showed the highest lipid extraction followed by methanol, chloroform, ethanol, and hexane. Afterward, we also assessed the relative influence of the solvent extractor selectivity on the overall FAMEs (Fatty Acids Methyl Esters) yield. The application of the transesterification process on the several lipidic extracts was compared with direct transesterification process from dry biomass. In the extraction using chloroform:methanol system a larger amount of lipids was obtained but the conversion to FAMEs using transesterification process was the lowest from lipids. However, despite the amount of extracted lipids with methanol being smaller, its conversion to FAMEs was higher from lipids. In addition, the extraction with methanol followed by transesterification process also resulted in a higher FAMEs yield from biomass than direct transesterification process using methanol.
Microalgae are photosynthetic microorganisms that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and useful chemicals. Two algae samples (Cladophora fracta and Chlorella protothecoid) were studied for biofuel production. Microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels. Microalgae can be converted to biodiesel, bioethanol, bio-oil, biohydrogen and biomethane via thermochemical and biochemical methods. Industrial reactors for algal culture are open ponds, photobioreactors and closed systems. Algae can be grown almost anywhere, even on sewage or salt water, and does not require fertile land or food crops, and processing requires less energy than the algae provides. Microalgae have much faster growth-rates than terrestrial crops. the per unit area yield of oil from algae is estimated to be from 20,000 to 80,000liters per acre, per year; this is 7–31 times greater than the next best crop, palm oil. Algal oil can be used to make biodiesel for cars, trucks, and airplanes. The lipid and fatty acid contents of microalgae vary in accordance with culture conditions. The effect of temperature on the yield of hydrogen from two algae (C. fracta and C. protothecoid) by pyrolysis and steam gasification were investigated in this study. In each run, the main components of the gas phase were CO2, CO, H2, and CH4.The yields of hydrogen by pyrolysis and steam gasification processes of the samples increased with temperature. The yields of gaseous products from the samples of C. fracta and C. protothecoides increased from 8.2% to 39.2% and 9.5% to 40.6% by volume, respectively, while the final pyrolysis temperature was increased from 575 to 925K. The percent of hydrogen in gaseous products from the samples of C. fracta and C. protothecoides increased from 25.8% to 44.4% and 27.6% to 48.7% by volume, respectively, while the final pyrolysis temperature was increased from 650 to 925K. The percent of hydrogen in gaseous products from the samples of C. fracta and C. protothecoides increased from 26.3% to 54.7% and 28.1% to 57.6% by volume, respectively, while the final gasification temperature was increased from 825 to 1225K. In general, algae gaseous products are higher quality than gaseous products from mosses.
With rapid economic development, energy consumption in China has tripled in the past 20years, exceeding 2.8 billion tons of standard coal in 2008. The search for new green energy as substitutes for nonrenewable energy resources has become an urgent task. Biodiesel is one of the most important bioenergy sources. According to the Mid- and Long-term Development Plan for Renewable Energy in China, the consumption of biodiesel in China will reach 0.2 million tons in 2010 and 2.0million tons in 2020. However, large-scale production of biodiesel is restricted by the limited sources of raw materials. Microalgal oil is a prospective raw material for biodiesel production. Development of technology for the production and commercialization of biodiesel from microalgae has become a hot topic in the field of bioenergy and CO2 emission mitigation. Biodiesel from microalgae can be produced at laboratory-scale, but the cost is too high. Few studies on the commercialization of the technology of producing biodiesel from microalgae have been reported. In this review, recent progress on the research and development of biodiesel from microalgae that have resulted in scientific breakthroughs and innovation in engineering in China are introduced. The existing challenges are also discussed. Based on a detailed analysis, several novel strategies on commercial biodiesel production from microalgae are proposed.
The objective of this paper is to study marine macroalgae as an alternative raw material for the biodiesel production. The obtained results show that biodiesel production from oil extracted from marine algae is feasible by transesterification. Oil extraction can be carried out simultaneously with the transesterification. To investigate the optimum reaction conditions, the reaction was carried out at various methanol to oil molar ratios, catalyst concentrations and reaction temperatures. The process yields 1.6–11.5% depending on the reaction conditions. Moreover, the properties of macroalgae transesterification residue after transesterification were analyzed, concluding that it is a suitable material for fuel pellets manufacturing.
For the extraction of oil from microalgae, which are recognised as an important renewable source of bioactive lipids, supercritical CO2 is regarded with interest being safer than hexane and offering a negligible environmental impact, short extraction time and petroleum-free final product. A mathematical model, able to describe the kinetics of a supercritical fluid extraction (SFE) process, was applied to the recovery of oil from the cyanobacterium Spirulina (Arthrospira) platensis, characterised by a particularly high content in γ-linolenic acid (C18:3ω-6). In this paper, we examine the kinetics of the SFE and the effect of operating conditions on extraction yield and fatty acid composition of lipid extracts.
This article reviews biological production processes of hydrogen as a renewable and alternative energy source. Biological hydrogen produced from renewable sources (biomass, water, and organic wastes) either biologically or photo-biologically is called “biohydrogen.” The phenomenon of biological hydrogen production was observed one century ago. When the oil crisis broke out in 1970s, the technology started receiving attention, especially in hydrogen production by photosynthetic process. Biological hydrogen production is one of the alternative methods where processes can be operated at ambient temperatures and pressures, and are less energy intensive and more environmentally friendly. Biological production of hydrogen as a by-product of microorganism metabolism is an exciting new area of technology development that offers the potential production of usable hydrogen from a variety of renewable resources.
The applicability of ionic liquid-polar covalent molecule co-solvent systems to extract bio-oils from biomass is evaluated. In our approach the extracted lipids are auto-partitioned to a separate immiscible phase for ease of harvesting. We propose that the action of the polar covalent molecule is largely to disrupt the cell wall and to improve the efficiency at which the lipid is extracted from the biomass. As ionic liquid solutions are both amphiphilic and characterized by strong “self-associating” ionic bonding between the cations and anions, we propose that the action of the ionic liquid is to facilitate the transfer of the lipids to the surface interface where they auto partition into a self-associating and separate phase. The potential of the co-solvent system to co-extract protein is also noted.
Dewatering of microalgal culture is a major bottleneck towards the industrial-scale processing of microalgae for bio-diesel production. The dilute nature of harvested microalgal cultures poses a huge operation cost to dewater; thereby rendering microalgae-based fuels less economically attractive. This study explores the influence of microalgal growth phases and intercellular interactions during cultivation on dewatering efficiency of microalgae cultures. Experimental results show that microalgal cultures harvested during a low growth rate phase (LGRP) of 0.03 d−1 allowed a higher rate of settling than those harvested during a high growth rate phase (HGRP) of 0.11 d−1, even though the latter displayed a higher average differential biomass concentration of 0.2gL−1d−1. Zeta potential profile during the cultivation process showed a maximum electronegative value of −43.2±0.7mV during the HGRP which declined to stabilization at −34.5±0.4mV in the LGRP. The lower settling rate observed for HGRP microalgae is hence attributed to the high stability of the microalgal cells which electrostatically repel each other during this growth phase. Tangential flow filtration of 20L HGRP culture concentrated 23 times by consuming 0.51kWh/m3 of supernatant removed whilst 0.38kWh/m3 was consumed to concentrate 20L of LGRP by 48 times.
In the present study, the use of immobilization technology to cultivate microalgae in entrapped matrix gel beads was demonstrated. Since the gel beads are denser in water, the beads can be easily collected through simple filtration method and hence, simplifying the overall separation process. Various parameters were investigated to optimize the growth rate of immobilized microalgae and the optimum conditions were obtained as: alginate to microalgae volume ratio of 0.3, Ca2+ concentration of 2%, organic nutrients concentration of 50 mL (equivalent to 13.09 mg/L nitrate), initial culture pH of 4 and photoperiod of 24 h. Using this optimum culture condition, 0.50 mg biomass/bead was attained on the 10th day of cultivation. Apart from that, this study also attempted to co-immobilize nutrients into microalgae beads in order to minimize free cell culture (microalgae cells that are released into the culture medium due to rupturing of beads) and to reduce water consumption. Through this approach, it was found that microalgae biomass yield increased to 0.67 mg/bead within a shorter culturing time (5 days) with insignificant amount of free cell culture detected. Furthermore, lipid extracted from immobilized microalgae biomass has high potential for biodiesel production due to the similarity of fatty acid profile with other oil bearing crops.
Microalgae for carbon dioxide mitigation was applied to the production of acetic acid under hydrothermal conditions with H2O2 oxidant. Results showed that acetic acid was obtained with a good yield of 14.9% based on a carbon base at 300 °C for 80 s with 100% H2O2 supply. This result should be helpful to facilitate studies for developing a new green and sustainable process in order to produce acetic acid from microalgae, which are the fastest growing sunlight-driven cell factories. These results show that it is possible to develop a process for conversion of microalgae biomass into acetic acid.
Nannochloropsis sp., one kind of green microalgae cultivated autotrophically and axenically in laboratory, is used as raw material to produce biodiesel by one-step method in an amended reactor. The effects of several reaction parameters on transesterification over Mg–Zr solid base catalyst were investigated through both conventional method and one-step method. One-step method could give a higher yield of methyl ester than conventional two-step method, which demonstrates that the present one-step method is suitable for biodiesel production from the microalgae Nannochloropsis sp. Moreover, the present one-step method realizes the convenient in situ separation of catalyst from microalgae residue which can be easily used consequently, reducing the procedure units as well as the overall costs.
We converted the marine microalga Nannochloropsis sp. into a crude bio-oil product and a gaseous product via hydrothermal processing from 200 to 500 °C and a batch holding time of 60 min. A moderate temperature of 350 °C led to the highest bio-oil yield of 43 wt %. We estimate the heating value of the bio-oil to be about 39 MJ kg−1, which is comparable to that of a petroleum crude oil. The H/C and O/C ratios for the bio-oil decreased from 1.73 and 0.12, respectively, for the 200 °C product to 1.04 and 0.05, respectively, for the 500 °C product. Major bio-oil constituents include phenol and its alkylated derivatives, heterocyclic N-containing compounds, long-chain fatty acids, alkanes and alkenes, and derivatives of phytol and cholesterol. CO2 was always the most abundant gas product. H2 was the second most abundant gas at all temperatures other than 500 °C, where its yield was surpassed by that of CH4. The activation energies for gas formation suggest the presence of gas-forming reactions other than steam reforming. Nearly 80% of the carbon and up to 90% of the chemical energy originally present in the microalga can be recovered as either bio-oil or gas products.
Global threats of fuel shortages in the near future and climate change due to green-house gas emissions
are posing serious challenges and hence and it is imperative to explore means for sustainable ways of
averting the consequences. The dual application of microalgae for phycoremediation and biomass production
for sustainable biofuels production is a feasible option. The use of high rate algal ponds (HRAPs)
for nutrient removal has been in existence for some decades though the technology has not been fully
harnessed for wastewater treatment. Therefore this paper discusses current knowledge regarding wastewater
treatment using HRAPs and microalgal biomass production techniques using wastewater streams.
The biomass harvesting methods and lipid extraction protocols are discussed in detail. Finally the paper
discusses biodiesel production via transesterification of the lipids and other biofuels such as biomethane
and bioethanol which are described using the biorefinery approach.
Due to increasing oil prices and climate change concerns, biodiesel has gained attention as an alternative energy source. Biodiesel derived from microalgae is a potentially renewable and carbon–neutral alternative to petroleum fuels. One of the most important decisions in obtaining oil from microalgae is the choice of algal species to use. Eight microalgae from a total of 33 isolated cultures were selected based on their morphology and ease of cultivation. Five cultures were isolated from river and identified as strains of Scenedesmus obliquus YSR01, Nitzschia cf. pusilla YSR02, Chlorella ellipsoidea YSR03, S. obliquus YSR04, and S. obliquus YSR05, and three were isolated from wastewater and identified as S. obliquus YSW06, Micractinium pusillum YSW07, and Ourococcus multisporus YSW08, based on LSU rDNA (D1-D2) and ITS sequence analyses. S. obliquus YSR01 reached a growth rate of 1.68 ± 0.28 day−1 at 680nm and a biomass concentration of 1.57 ± 0.67 g dwt L−1, with a high lipid content of 58 ± 1.5%. Under similar environmental conditions, M. pusillum reached a growth rate of 2.3 ± 0.55 day−1 and a biomass concentration of 2.28 ± 0.16 g dwt L−1, with a relatively low lipid content of 24 ± 0.5% w/w. The fatty acid compositions of the studied species were mainly myristic, palmitic, palmitoleic, oleic, linoleic, g-linolenic, and linolenic acids. Our results suggest that S. obliquus YSR01 can be a possible candidate species for producing oils for biodiesel, based on its high lipid and oleic acid contents.
The conversion of lipid-extracted microalgal biomass residues (LMBRs) into hydrogen plays the dual role in renewable energy production and sustainable development of microalgal biodiesel industry. An anaerobic fermentation process to covert LMBRs into hydrogen was investigated in this work. Using batch experiments, the effects of pretreatment of inoculum (by acid, base, heat, and chloroform, respectively), initial pH (5.0–7.0), inoculum concentrations at 0.59–2.94 g VSS/l (volatile suspended solids, VSS) and substrate concentrations at 4.5–45 g VS/l (volatile solids, VS) were investigated, respectively. The results showed that the most effective hydrogen production was obtained from fermentation of LMBRs with a concentration of 36 g VS/l at the initial pH 6.0–6.5 using the heat-treated anaerobic digested sludge as inoculum. Acetate, propionate and butyrate were the main fermentation byproducts in the conversion of LMBRs into hydrogen.
a b s t r a c t Carbon-neutral renewable liquid biofuels are needed to displace petroleum-derived transport fuels in the near future – which contribute to global warming and are of a limited availability. A promising alterna-tive is conveyed by microalgae, the oil content of which may exceed 80% (w/w DW) – as compared with 5% of the best agricultural oil crops. However, current implementation of microalga-based systems has been economically constrained by their still poor volumetric efficiencies – which lead to excessively high costs, as compared with petrofuel prices. Technological improvements of such processes are thus critical – and this will require a multiple approach, both on the biocatalyst and bioreactor levels. Several bottlenecks indeed exist at present that preclude the full industrial exploitation of microalgal cells: the number of species that have been subjected to successful genetic transformation is scarce, which hampers a global understanding (and thus a rational design) of novel blue-biotechnological processes; the mechanisms that control regulation of gene expression are not fully elucidated, as required before effective biopro-cesses based on microalgae can be scaled-up; and new molecular biology tools are needed to standardize genetic modifications in microalgae – including efficient nuclear transformation, availability of promoter or selectable marker genes, and stable expression of transgenes. On the other hand, a number of pending technological issues are also present: the relatively low microalga intrinsic lipid productivity; the max-imum cell concentration attainable; the efficiency of harvest and sequential recovery of bulk lipids; and the possibility of by-product upgrade. This review briefly covers the state of the art regarding mic-roalgae toward production of biofuels, both from the point of view of the microalgal cell itself and of the supporting bioreactor; and discusses, in a critical manner, current limitations and promising perspectives in this field.
In the current scenario of depleting energy resources, increasing food insecurity and global warming, Jatropha has emerged as a promising energy crop for India. The aim of this study is to examine the life cycle energy balance for Jatropha biodiesel production and greenhouse gas emissions from post-energy use and end combustion of biodiesel, over a period of 5 years. It’s a case specific study for a small scale, high input Jatropha biodiesel system. Most of the existing studies have considered low input Jatropha biodiesel system and have used NEB (Net energy balance i.e. difference of energy output and energy input) and NER (Net energy ratio i.e. ratio of energy output to energy input) as indicators for estimating the viability of the systems. Although, many of them have shown these indicators to be positive, yet the values are very less. The results of this study, when compared with two previous studies of Jatropha, show that the values for these indicators can be increased to a much greater extent, if we use a high input Jatropha biodiesel system. Further, when compared to a study done on palm oil and Coconut oil, it was found even if the NEB and NER of biodiesel from Jatropha were lesser in comparison to those of Palm oil and Coconut oil, yet, when energy content of the co-products were also considered, Jatropha had the highest value for both the indicators in comparison to the rest two.
Marine microalgae are recognised as an important renewable source of bioactive lipids with a high proportion of polyunsaturated fatty acids (PUFA), which have been shown to be effective in preventing or treating several diseases. For the extraction of oil from microalgae, supercritical CO2 (ScCO2) is regarded with interest, being safer than hexane and offering a negligible environmental impact, a short extraction time and a high-quality final product. Whilst some experimental papers are available on the supercritical fluid extraction (SFE) of oil from microalgae, only limited information exists on the kinetics of the process. In such a contest, a mathematical model able to describe the kinetics of the SFE was applied to the recovery with ScCO2 of lipids from Nannochloropsis sp., a marine microalga commonly used in aquaculture and characterised by a lipid fraction with a high PUFA content. The aim of this paper was to examine the effect of operating conditions on the kinetics of the SFE, on process yields and on the fatty acid composition of lipid extracts.
Microalgae are a diverse group of organisms with significant potential for industrial applications: as feedstock in aquaculture as well as in the production of valuable bioproducts such as lipids, carotenoids and enzymes. Lately, developments in molecular biology have improved production yields of algae bioproducts, thus increasing their industrial relevance. Additionally, variations in bioprocessing factors (i.e. temperature, pH, light, carbon source, salinity, nutrients, etc.) have been used to enhance both biomass and specific bioproducts' productivities. Particularly, microalgae have increasingly gained research interest as a source of specialty lipids such as arachidonic, eicosapentaenoic and docosahexaenoic acids, which are often reported in literature to provide several health benefits. Moreover, there has been a recent resurgence in interest in microalgae as an oil producer for biofuel applications. Significant advances have also been made in upstream processing to generate cellular biomass and oil. However, extracting and purifying oil from algae continues to prove a significant challenge in producing both microalgae bioproducts and biofuel, as microbial oil extraction is relatively energy-intensive and costly. Thus, developing inexpensive and robust oil extraction and purification processes is a major challenge facing both the microalgae to bioproduct, and biofuel industries. This paper presents an overview, based on the last 10 years, of advances made in technologies for extracting and purifying microalgae oil. We compared solvent extraction technologies with extraction alternatives such as mechanical milling and pressing, enzymatic and supercritical fluid extraction. We also reviewed recent advances based on molecular engineering of microbes to aid oil extraction. Downstream processing for the potential commercial production of microalgae oil not only must consider economic costs, but should also consider minimizing environmental impacts in order to attain sustainable production processes.
This review explains the potential use of the so-called “green coal” for biofuel production. A comparison between microalgae and other crops is given, and their advantages are highlighted. The production of biofuels from microalgae biomass is described, such as the use of algae extracts (e.g. biodiesel from oil, bioethanol from starch), processing the whole biomass (e.g. biogas from anaerobic digestion, supercritical fluid, bio-oil by pyrolysis, syngas by gasification, biohydrogen, jet fuel), as well as the direct production (e.g. alcohols, alkanes). Microalgal biomass production systems are also mentioned, including production rates and production/processing costs. Algae cultivation strategy and the main culture parameters are point out as well as biomass harvesting technologies and cell disruption. The CO2 sequestration is emphasised due to it’s undoubted interest in cleaning our earth. Life cycle analysis is also discussed. The algal biorefinery strategy, which can integrate several different conversion technologies to produce biofuel is highlighted for a cost-effective and environmentally sustainable production of biofuels. The author explains some of the challenges that need to be overcome to ensure the viability of biofuel production from microalgae. This includes the author’s own research, the use of microorganism fuel cells, genetic modification of microalgae, the use of alternative energies for biomass production, dewatering, drying and processing. The conclusion of the manuscript is the author’s view on the potential of microalgae to produce biofuels; the drawbacks and what should be done in terms of research to solve them; which technologies seem to be more viable to produce energy from algae; and which improvements in terms of microalgae, systems, and technologies should take place to enable the algae to fuels concept a reality.
Fossil fuel resources are decreasing daily. Biodiesel fuels are attracting increasing attention worldwide as blending components or direct replacements for diesel fuel in vehicle engines. Biodiesel fuel typically comprises lower alkyl fatty acid (chain length C14–C22), esters of short-chain alcohols, primarily, methanol or ethanol. Various methods have been reported for the production of biodiesel from vegetable oil, such as direct use and blending, microemulsification, pyrolysis, and transesterification. Among these, transesterification is an attractive and widely accepted technique. The purpose of the transesterification process is to lower the viscosity of the oil. The most important variables affecting methyl ester yield during the tra