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Microalgae have been evaluated as promising resource for biodiesel production, but algal biofuel production is not yet commercially viable, which reflects the high energy costs linked with cultivation, harvesting, and dewatering of algae. As crude oil processing declines, microalgae biorefineries are being considered for producing bioactives such as enzymes, proteins, omega-3 oils, pigments, recombinant products, and vitamins, to offset the costs of biofuel production. We believe that producing algal bioactives through advanced manufacturing pathways, encompassing a biorefinery approach, would be effective, profitable, and economical.

A number of technological challenges need to be overcome if algae are to be utilized for commercial fuel production. Current economic assessment is largely based on laboratory scale up or commercial systems geared to the production of high value products, since no industrial scale plant exits that are dedicated to algal biofuel. For macroalgae (‘seaweeds’), the most promising processes are anaerobic digestion for biomethane production and fermentation for bioethanol, the latter with levels exceeding those from sugar cane. Currently, both processes could be enhanced by increasing the rate of degradation of the complex polysaccharide cell walls to generate fermentable sugars using specifically tailored hydrolytic enzymes. For microalgal biofuel production, open raceway ponds are more cost-effective than photobioreactors, with CO2 and harvesting/dewatering costs estimated to be ~50% and up to 15% of total costs, respectively. These costs need to be reduced by an order of magnitude if algal biodiesel is to compete with petroleum. Improved economics could be achieved by using a low-cost water supply supplemented with high glucose and nutrients from food grade industrial wastewater and using more efficient flocculation methods and CO2 from power plants. Solar radiation of not −1 favours production sites 30° north or south of the equator and should use marginal land with flat topography near oceans. Possible geographical sites are discussed. In terms of biomass conversion, advances in wet technologies such as hydrothermal liquefaction, anaerobic digestion, and transesterification for algal biodiesel are presented and how these can be integrated into a biorefinery are discussed.

The use of wastewater-grown microalgae has the potential to reduce the cost of algae-derived biofuels while simultaneously advancing nutrient recovery at water resource recovery facilities (WRRFs). However, a significant barrier has been the low yield and high protein content of phototrophic biomass. Here, we examine the use of solids residence time (SRT) as a selective pressure in driving biochemical composition, yield, biofuel production, and WRRF nutrient management cost. We cultivated mixed phototrophic communities in controlled, laboratory-scale photobioreactors on the local WRRF secondary effluent to link SRT with biochemical composition and techno-economic analysis to yield insights into biomass composition and downstream processing effects on minimum fuel selling price. SRT significantly impacted biochemical composition, with total and dynamic carbohydrates the highest at low SRT (total carbohydrates being 0.60 and 0.32 mg-carbohydrate·mg-protein-1 at SRT 5 and 15 days, respectively). However, there were distinct differences between extant, steady-state performance and intrinsic potential, and longer SRT communities were able to accumulate significant fractions (51% on an ash-free dry weight basis, AFDW %) of carbohydrate reserves under nutrient starvation. Overall, hydrothermal liquefaction (HTL) was found to be more suitable than lipid extraction for hydrotreating (LEH) and combined algal processing (CAP) for conversion of biomass to fuels, but LEH and CAP became more competitive when intrinsic carbon storage potential was realized. The results suggest that the use of algae for nutrient recovery could reduce the nutrient management cost at WRRFs through revenue from algal biofuels, with HTL resulting in a net revenue.

Algal biofuel research aims to make a renewable, carbon–neutral biofuel by using oil-producing microalgae. The freshwater microalga Botryococcus braunii has received much attention due to its ability to accumulate large amounts of petroleum-like hydrocarbons but suffers from slow growth. We performed a large-scale screening of fast-growing strains with 180 strains isolated from 22 ponds located in a wide geographic range from the tropics to cool-temperate. A fast-growing strain, Showa, which recorded the highest productivities of algal hydrocarbons to date, was used as a benchmark. The initial screening was performed by monitoring optical densities in glass tubes and identified 9 wild strains with faster or equivalent growth rates to Showa. The biomass-based assessments showed that biomass and hydrocarbon productivities of these strains were 12–37% and 11–88% higher than that of Showa, respectively. One strain, OIT-678 established a new record of the fastest growth rate in the race B strains with a doubling time of 1.2 days. The OIT-678 had 36% higher biomass productivity, 34% higher hydrocarbon productivity, and 20% higher biomass density than Showa at the same cultivation conditions, suggesting the potential of the new strain to break the record for the highest productivities of hydrocarbons.

Algal-based biofuels offer distinct advantages over other types of biofuels currently available within the fuel industry. However, one important disadvantage is that over their entire life cycle, they consume significant amounts of energy through cultivation, pretreatment, and production. Under pretreatment, drying is an energy-intensive yet highly critical process in standardizing the production of algal biofuel products. The current study proposes the use of artificial intelligence (AI) methods in optimizing the efficiency of a vacuum drying process. Previously, vacuum drying was modeled using least-squares regression methods, which captured the general linear or non-linear trend of the samples, but secured poor accuracy for individual sample points. In addition, these methods are unsuitable for online parameter optimization. Three AI-based models were developed to model the vacuum drying process, specifically an artificial neural network (ANN), a support vector machine (SVM), and an extreme gradient boosting machine (XGB). Based on error values, the ANN (RMSE = 0.0437) and XGB (RMSE = 0.0308) outperformed polynomial regression, and all models obtained meaningful lower values than multivariate linear regression (MLR). There is a notable difference in the ability of XGB to approximate individual sample points, particularly at high and low tail-ends of the dataset. Overall, the AI methods exhibited higher accuracy in estimating the drying characteristics for the chosen strain of algae. The current study may be extended to optimization by relating the control parameters to energy consumption, and automation based on the mathematical model.

The demand for energy is growing tremendously due to the modernization in every aspect of life, hence in order to meet the demands without any lag in the growth and development of the world, an alternative source of energy needs to be found. The best alternative would be biofuels which are extracted from organic compounds. Out of many different organic sources available, algae are one among them, which can be used to extract biofuel. Algae are aquatic organisms which are found in all types of water bodies. Also, algae are plentily available and can be easily cultivated, to be considered as one of the potential raw material for production of biodiesel in large scale. In this present research, an experimental setup was fabricated to produce the algae oil. The algae species used for this investigation was Spirogyra sp. Solvent extraction method was used to produce algae oil. The Soxhlet apparatus was used to carry out the solvent extraction process. The solvent type used for the present study was n-hexane, which is an organic non-polar solvent suitable for extracting lipid content from the biomass. From the experiment, it was found that the oil extraction from 100% dried algae and finer size of algae resulted in higher percentage of oil extraction. For algae of mass 50 g, the oil yielded was around 83% for solid to solvent ratio of 1:5, particle size of 0.322 μm, and reaction time was of 3 h. Also, the oil extracted from the algae is characterized to identify its suitability for using it as an alternative fuel in the IC engines. The characterization revealed that, the physiochemical properties were in permissible range in comparison with the standard diesel.

Considered as a promising source of sustainable energy, biofuel produced from algae holds many advantages. However, to truly understand the production process and assess the potential for further o...

This study conducts a comparative evaluation the effect of using palm kernel oil (PKO), pure petroleum diesel and their blends (B5, B10, B20, B30, B40, and B100), on the performance of a four-cylinder CI diesel engine (David Brown 990: 58hp; 2WD), at Farm Power and Machinery Test laboratory Centre (FPMTLC), Department of Agricultural and Bioresources Engineering, University of Nigeria, Nsukka. The objective of the study was to determine the fuel consumption rates, energy expended, brake specific fuel consumption, and brake thermal efficiency, under varying operating speeds (700 – 1900rpm) at constant torque. Each fuel test was conducted using the Heenan-Froude hydraulic dynamometer engine-test-bed; pure petroleum diesel (B0) was used to generate the baseline data. Variables calculated were analyzed, then compared with each other to determine the differences in the engine performance and also to determine the optimum test fuel. The results obtained show that B10 had the overall optimum energy output, fuel consumption rates, and brake specific fuel consumption of 5431.809J, 3.42E-07 m3/s, and 0.16569l/KWh, respectively at the highest engine speed of 1900. B10 had an excellent brake thermal efficiency of 60.6% but was not better than B100, which showed a higher value of 66.95%. From the analysis, B10 is the optimum test fuel and can be used as an alternative fuel in David Brown 990 (58hp; 2WD) or similar CI diesel engines without any engine modification, even though B100 showed potential as an alternative to fossil diesel. Biofuel production grows through integrated aquaculture and algae production; the algae oil will serve as a raw material for biofuel production Keywords: Blends, Biodiesel, Brake Specific Consumption, Diesel Engine, Fuel Consumption rate, Thermal Efficiency.

Current research talks about the extraction of green crude from algae using fast pyrolysis, comparison of properties of biofuel derived from various feedstocks, analysis of biofuels using multi-cri...

The economic feasibility of growing Nannochloropsis sp. at the commercial scale was evaluated for the production of biodiesel and co-products. A local isolate of Nannochoropsis was grown in (6) 200-L raceway ponds at Alexandria University wherein cultures reached maximum cell concentrations ~ 4–6 × 107 cells/mL (0.63–0.88 g/L dry weight) and a peak biomass productivity of 0.09 g/L/day during mid- to late-log growth. Areal productivity was estimated at 17.65 g/m2/day when ponds were operated on a semi-batch schedule, harvesting 50% every 2 days and recycling 60% of the media. Areal productivity was estimated around 10.3 g/m2/day for batch schedules. Late-log cultures harvested from all ponds yielded 10 kg of wet algal paste, which was reduced to 1.05 kg of dried algal powder. The biomass was composed of valuable co-products approx. 14.0% carbohydrate, 37.3% protein, 0.01% chlorophyll-a, and 0.02% carotenoids (w/w). Total lipid made up 38% of the biomass (w/w); 34% of the biomass was determined to be neutral lipid which are transesterified to biodiesel and 4% are polar lipid. Fatty acids from glycerolipids were quantified by gas chromatography-flame-ionization detector (GC-FID) as fatty acid methyl esters (FAMEs) revealing carbon-chain lengths from C6 to C22. A preliminary economic evaluation was conducted to determine the feasibility of constructing commercial-scale algae biodiesel production facilities in Egypt. The return on investment (ROI) of the current economic feasibility study for biofuel production alone was 22% after considering the market prices of the biodiesel, cake, and glycerol by-products. Based on this assessment, additional high-value products are needed to improve the ROI. Noting that the valuable co-products are considered as added cost in the biomass left after biodiesel production.

In this study, a novel two-step integrated process is proposed to facilitate the microalgae biofuel production as well as fresh cheese whey wastewater (FCWW) treatment simultaneously. The pre- and post-treatment of high-strength FCWW were performed by means of coagulation and algal cultivation, respectively. The pre-treatment of FCWW for maximum removal of chemical oxygen demand (COD), turbidity (TUR) and total solids (TS) as responses was obtained by statistical optimization of coagulation parameters. The maximum removal of COD, TUR and TS at the optimum level of variables was obtained as 68.09%, 47.80% and 73.63%, respectively. The pre-treated FCWW was further treated by Chlorella pyrenoidosa and observed a significant reduction in the above-mentioned responses (87–94%). The maximum algal biomass yield and lipid productivity were observed as 2.44 g L−1 and 77.41 mg L−1 day−1, respectively. Based on promising results of FCWW treatment and its use as a third-generation biodiesel feedstock, a cost-benefit analysis of the developed process was assessed for microalgal oil production. The total profit earned by the integrated process model was $9.59 million year−1. Accordingly, the estimated production cost of algal oil (TAG) from the developed system was estimated to be $79.03 per barrel.

As a result of city, industrial and agricultural activities, a large amount of wastewater is generated every year. The wastewater generated must be treated. When the nitrogen concentration in wastewater reaches more than 1.9 mg/L, favorable environmental conditions are provided for the microalgae to multiply. In the presence of microalgae in wastewater treatment technologies, treatment has gained importance in recent years and has become a more environmentally-friendly alternative in treatment. Research on the availability of biomass as a source of raw materials in the production of alternative energy sources is increasingly important. In this paper, Chlorella variabilis microalgae growth, lipid productivity and nutrient removal in wastewater media were investigated. Before the inoculation of microalgae, wastewater was centrifuged at 4000 rpm to remove the solid particles and was diluted with tap water in different ratios (0-40%). Wastewaters were inoculated with Chlorella variabilis in 250 mL open flasks in a 200 rpm shaking incubator for a month at 27 °C. After incubation maximum cell concentration (Xmax=1.03 gdw/L), growth rate (µmax=4.0 x10-3 h-1), and doubling time (173 h) of the microalgae were reached in 40% diluted medium. Fat content (21%) and lipid productivity (6x10-3 g/L.d) were determined concurrently for 20% diluted media. It was determined that microalgae lipids were rich in oleic (C18:1, 38%) and linolenic acid (C18:3, 35%). The efficiency of COD (Chemical oxygen demand) and total phosphor removal in the presence of microalgae had been almost 60% and 77% respectively. According to the experimental results, the treatment of wastewater in the presence of microalgae is promising for future applications., Şehir, sanayi ve tarım faaliyetleri sonucunda her yıl büyük miktarlarda atık su üretilmektedir. Üretilen atık sular arıtılmalıdır. Atık suda varolan azot derişimi 1,9 mg/L değerinin üzerine çıktığında, mikroalglerin çoğalması için uygun çevresel koşullar sağlanır. Atıksu arıtma teknolojilerinde mikroalg varlığında arıtma, son yıllarda önem kazanmış ve arıtımda daha çevre dostu bir alternatif haline gelmiştir. Alternatif enerji kaynaklarının üretiminde hammadde kaynağı olarak biyokütlenin bulunabilirliği üzerine araştırmalar giderek önem kazanmaktadır. Bu çalışmada, atık su ortamlarında Chlorella variabilis mikroalg büyümesi, lipit üretkenliği ve nütrient giderimi araştırılmıştır. Mikroalglerin aşılanmasından önce atık su, katı parçacıkların uzaklaştırılması amacıyla 4000 rpm koşulunda santrifüjlenmiş ve farklı oranlarda (%0-40) musluk suyu ile seyreltilmiştir. Farklı oranlarda seyreltilmiş olan atıksular, 250 mL hacimli ağzı açık olan şişeler içinde Chlorella variabilis mikroalgi ile aşılanmış, 27 °C sıcaklık ve 200 rpm çalkalama hızına sahip olan inkübatörde, bir ay süre boyunca inkübe edilmiştir. İnkübasyon sonucunda maksimum mikroalg derişimi (Xmax = 1.03 gdw/L), hücre büyüme miktarı (µmax = 4.0 x10-3 h-1) ve mikroalglerin ikiye katlanma süresine (173 saat) % 40 oranında musluk suyu ile seyreltilmiş olan atık su ortamında ulaşılmıştır. Mikroalgal biyokütleden elde edilen lipid yağ içeriği (% 21) ve lipit üretkenliği (6x10-3 g/L.d), % 20 oranında seyreltilmiş atık su ortamı için eşzamanlı olarak belirlenmiştir. Mikroalg lipidlerinin oleik asit (C18:1, % 38) ve linolenik asit (C18:3, % 35) bakımından zengin olduğu tesbit edilmiştir. Mikroalglerin varlığında Kimyasal Oksijen İhtiyacı (KOİ) ve toplam fosfor giderimi etkinliği sırasıyla, yaklaşık olarak % 60 ve % 77 değerinde olmuştur. Deney sonuçlarına göre, atık suyun mikroalglerin varlığında arıtımı gelecekteki uygulamalar için umut vericidir.

This study describes a new algal biofuel process that integrates sugarcane biorefinery wastewater treatment by nutrient removal with algae into bioethanol. The process is free of common industrial problems, including algal contamination, nutrients and fresh water usage, carbohydrate extraction, liquefaction, and saccharification. Cultivation and fermentation were conducted in one step by turning the light-air on and off, respectively. Three series of experiments with Chlamydomonas reinhardtii CC-1093 cultivation and fermentation were performed in anaerobically digested vinasse. Control experiments were a reference to compare the influence of chloride and ammonium-sulfate stress conditions on ethanol yield. Experimental results showed: (1) algal biomass can be successfully cultured within biorefinery wastewater (1129 mg·L−1·day−1); (2) relatively high bioremediation was achieved (26.1%–83.5%); (3) obtained ethanol yield was (maximum 68.3% of the theoretical yield) in one process step; and (4) the chloride stress condition influences on algae to synthesize extracellular polysaccharides as add-in product (120 mg/L).

Due to rapid rise in world population and increasing demands in energy sector, the fossils fuels reserves are drastically and continuously depleting, globally. The reckless use of fossils fuels contributes to greenhouse gases, air pollution, and global warming, which culminate in ecological imbalance and health hazards. Therefore, alternate sources of renewable energy are required to meet the future demands of global energy sector. Microalgae being photoautotrophic organisms have the attributes of rapid biomass production and carbohydrates, proteins, and lipids/oil production. They can be one of the best resources, not only for biodiesel production, but also hydrogen and methane gas, bio oil, heat, and electricity generation. Hence, biodiesel production from algal biomass is lucrative for the scientific community because it is nonpolluting, biodegradable, nontoxic, noncorrosive, and sulfur-free. The algal biofuel production shall not only revolutionize the environmental pollution regulation but also be useful in economic and social upliftment of producers.

For sustainability assessment of algal biodiesel production, life cycle analysis (LCA) offers a quantitative measure. In this chapter, various literature available on LCA studies of algae biodiesel production are evaluated, depicting that some comprehensive studies compiling various techniques. LCA outputs are dependent on various inputs such as the algae species, bioreactor type, and biochemical reaction conditions. Nevertheless, the paucity in the systematic framework for LCA in the biofuel production process also affected the LCA outputs. In addition, the system boundaries, temporal units, choice of allocation, land utilization, and biogenic carbon source have to be redefined; along with the other unconsidered variables (till now) such as infrastructure construction, systematic maintenance, transportation, waste management, and process intensification, and the overall cost involved should also be included in the LCA method. This chapter covers an inclusive and critical overview of the LCA and techno-economic and policy analyses for the complete algal biodiesel procedure that can assist in future-related studies.

The term “algae” has become synonymous with the term “biofuel” for quite some time now. Although that may be the case, recently algal research in wastewater treatment (WWT) has gained even more traction owing to microalgae's inherent capability of using wastewater components as nutrients. And in the process of remediation, viable biomass is produced, which can be selectively processed to obtain biofuel and other products. Coupling WWT with algal biofuel production and other downstream products serves as a biorefinery approach, which effectively brings down the cost of production and makes algal biofuel a viable option. Algal WWT is still not in a very mature stage; however, many different approaches and technologies have been researched all over the world for the same. These primarily target treatment efficiency, algal biomass productivity and quality, energy and cost efficiency, and how well the system can be incorporated in a biorefinery. This chapter describes the basic principles of algal WWT and the different technologies that have been applied. Considering environmental and economical sustainability, and looking through an artificial intelligence perspective to WWT, this chapter aims to cover novel avenues in algal biotechnology. It also delves into brave and innovative concepts that have been used in incorporating algae with WWT.

Microalgae offer a great potential to contribute significantly as renewable fuels and documented as a promising platform for algae-based bio refineries. They provide solutions to mitigate the environmental concerns posed by conventional fuel sources; however, the production of microalgal biofuels in large scale production system encounters few technical challenges. High quantity of nutrients requirements and water cost constrain the scaling up microalgal biomass to large scale commercial production. Crop protection against biomass losses due to grazers or pathogens is another stumbling block in microalgal field cultivation. With our existing technologies, unless coupled with high-value or mid-value products, algal biofuel cannot reach the economic target. Many microalgal industries that started targeting biofuel in the last decade had now adopted parallel business plans focusing on algae by-products application as cosmetic supplements, nutraceuticals, oils, natural color, and animal feed. This review provides the current status and proposes a framework for key supply demand, challenges for cost-effective and sustainable use of water and nutrient. Emphasis is placed on the future industrial market status of value added by products of microalgal biomass. The cost factor for biorefinery process development needs to be addressed before its potential to be exploited for various value-added products with algal biofuel.

Microalgae have great potential as an energy and feed resource. Here we evaluate the water use associated with freshwater algae cultivation and find it is possible to scale U.S. algae biofuel production to 20.8 billion liters of renewable diesel annually without significant water-stress impact. Among potential sites, water-stress is significantly more variable than algae productivity across location and season. Thus, it is possible to reduce water-stress impact, quantified as water scarcity footprint, through the choice of algae site location. We test three site-selection criteria based on (1) biomass productivity, (2) water-use efficiency, and (3) water-stress impact and find that adding water-stress constraints to productivity-based ranking of suitable sites reduces water-stress impact by 97% and water consumption by half, compared with biomass-productivity ranking alone, with little productivity impact (

The biodiesel as a substitute to fossil fuel is able to reduce the dependence on petroleum products as well as increase the engine performance. These biofuel produced from the different sources and also it is directly used for the engine it will not fully burn and it produces increased exhaust emission level. In this research, 20% of neochloris oleoabundans algae oil (B20) blended with neat diesel fuel along with cerium oxide (CeO2) nanoparticle was used in the dosage of 25 ppm, 50 ppm, 75 ppm and 100 ppm. The experimental outcomes obtained indicated that the brake thermal efficiency had been improved and also the exhaust engine emission was decreased. And also the brake specific fuel consumption had been decreased. This research was performed in a single cylinder air cooled engine connected with electrical dynamometer without having engine alteration and also the injection pressure and timings are maintained at the original standard suitable for the engine. The energy of cerium oxide blend with the biodiesel increased the performance of the diesel engines.

The biodiesel as a replacement source to fossil fuel is able to minimize the dependence on petroleum products as well as control the pollution issues. These biofuel produced from the different sources and also it is directly used for the engine it will not fully burn and it produces increased exhaust emission level. In this research, 20% of neochloris oleoabundans algae oil (B20) blended with neat diesel fuel along with cerium oxide (CeO2) nanoparticle was used in the dosage of 25 ppm, 50 ppm, 75 ppm and 100 ppm. This research was performed in a single cylinder air cooled engine connected with electrical dynamometer without having engine alteration and also the injection pressure and timings are maintained at the original standard suitable for the engine. The energy of cerium oxide blend with the biodiesel increased the combustion properties in the engine, and results in decreased carbon deposits in the cylinder wall.

Carbon dioxide (CO2), being an important greenhouse gas (GHG) significantly present in Earth's atmosphere, has been increasing because of several anthropogenic activities leading to global warming. Globally, various efforts have been made to confront climate change, and various CO2 capture and storage methods have been designed. This review aims at describing detailed studies about algae and the methods used by algae to capture and sequester carbon from the atmospheric environment. Algae exist in varied terrestrial and aqueous habitats. Under certain conditions, microalgae are potential accumulators of lipids, which act as a biofuel. Algal biofuel production promotes carbon sequestration and future energy production. This review explicates the opportunities and challenges for biological systems in CO2 sequestration by algae. In addition, the CO2 fixation by algae is explored and leading biochemical channels and enzymes involved in it are studied.

World at giving is stood around the twin problems of fossil oil product intake and normal degradation. The purpose of this research is actually to examine the behaviour of C. racemosa algae oil biodiesel within a diesel engine. Biodiesel is an unparalleled earth-friendly source meant to extend the worth to fossil fuels, and also the durability and cleanliness of diesel-powered engines. C. racemosa algae may be used to make biodiesel, only because of high oil content. The transesterification of the oil produces biodiesel. The abundant benefits of biodiesel tend to get over by few disadvantages like the increase in the nitrogen oxide, its incompatibility at cold temperature conditions, and also the regular periods of engine parts replacement. Generally, there is additional scope for the improvement in fuel properties and also to overcome the disadvantages by the addition of nanoparticles as fuel additives. In the current study, the Bi2O3 nano additives inside algae oil-based methyl ester blend as well as its diesel blends are examined the performance and emission characteristics at various loads.

In the midst of a global food crisis, the late 2000s saw tensions between rising food prices and demands for biofuels coalesce into a “food versus fuel” debate. In response to ensuing public outcries, governmental agencies, and researchers across the globe began mobilizing around alternative biofuel feedstock. Among these materials, algae emerged as the most “hopeful” sustainable alternative in producing biofuels. This article examines algal biofuel production systems designed offshore and integrated with wastewater treatment and carbon dioxide absorption processes to revitalize faith in biofuels in the blue economy. It discusses what makes algal biofuels sustainable by examining the ways practitioners talk about and design these integrated systems. Against the common refrain that algae’s photosynthetic and reproductive capacity makes these systems sustainable, this article underlines that there is nothing natural, innate, about algae to add to sustainable blue economies. Rather, algae become naturalized as biofuel source and bioremediation technologies through technoscientific discourses and interventions, which embed and reproduce anthropocentric approach to sustainability that centers on the ideology of growth. By drawing particular attention to the ways that integrated algal biofuel production systems depend on the constant generation of industrial waste, this article problematizes anthropocentric sustainability imaginaries and claims for imagining sustainability otherwise through the lens of blue degrowth to create a radical socio-ecological change.

Increasing concern towards climate change and water conservation has attracted wide attention of researchers to explore the biological carbon fixation and wastewater treatment by using microalgae. Algal biomass can be harvested in an integrated system provided with carbon dioxide from power plants and wastewater released from industrial and domestic sector. In this way simultaneous potential of microalgae can be utilized for simultaneous fixation of CO2 and wastewater treatment. This article present a critical review focusing on challenges in algal biomass production technologies and how to achieve algal biofuel production in an integrated system of CO2 fixation and wastewater treatment by suitable microalgal species. In view of these objectives, this article provides a comprehensive narration about the following: (a) perspectives of carbon uptake by algal biomass; (b) industrial emissions as a CO2 supplement for algal cultivation; (c) water foot print for algal cultivation; and (d) genomics for improvement of algal biofuel production. This review found that technical feasibility, economic viability, and resource sustainability are the key steps for algal biofuel production that can be achieved through flue gas and wastewater nexus in algal cultivation. It also provides salient features of algae-nutrient-wastewater-flue gas dynamics to measure the influences of flue gas and wastewater on algal biomass productivity.

The concerns of fossil fuel depletion and environmental issues have increased general interest in studies on the development of sustainable biofuel. In the biofuel production process, the extraction technique is a key technology with respect to energy consumption and product value. In this review, recent advances related to the extraction process in biofuel production are discussed. The major extraction methods were classified as conventional solvent extraction (CSE), physical-supported solvent extraction (PSSE), supercritical fluid extraction (SFE), and novel extractions. We address each of these classified extraction methods in turn both in relation to the feedstock utilized in the different biofuel generation methods and to the targeted biofuels. Our objective is to provide a concise, timely, and comprehensive review on various extraction methods applied/studied regarding biofuel production, their principles and advantages/limitations, and recent case studies. In particular, the classified extraction methods in the production of third-generation algal biofuel were intensively evaluated. Consequently, the concept of free from drying and cell disruption (FDC) routes was advanced herein as it may possess the potential to reduce the requirement for input energy during the production of algae biofuels.

This study presents a life cycle greenhouse gas and energy assessment for two algal biofuel production pathways: biodiesel produced through lipid extraction (LE) and renewable diesel produced through hydrothermal liquefaction (HTL). The two production pathways generate different co-products, which are handled through allocation in life cycle assessment-based analyses. The method and assumptions used for co-product allocation affect the performance of the analyzed fuels, and are thus examined through scenario analysis; five co-product allocation strategies are tested for the LE pathway and six are tested for the HTL pathway. After allocation, the carbon intensity of renewable diesel varies from 36 to 54 gCO2e/MJ, and the primary energy consumption of renewable diesel varies from 0.7 to 1.2 MJ/MJ; while the carbon intensity of biodiesel ranges, remarkably, from −59 to 125 gCO2e/MJ, and the primary energy consumption of biodiesel ranges from 0.1 to 1.7 MJ/MJ. The optimal algal oil production pathway is determined by comparing open-loop and closed-loop systems, considering not only the estimated net environmental impacts, but also the confidence or uncertainty of those outcomes.

BACKGROUND: The combination of wastewater treatment and algal biofuel production has received increasing attention in recent years owing to its many advantages. In order to clarify the influence of different organic pollutants such as carbohydrates, volatile fatty acids (VFAs) and proteins in domestic wastewater on the cultivation of Chlorella vulgaris, three simulated domestic sewages containing glucose, sodium acetate (NaAc) and protein respectively were prepared in this study to culture C. vulgaris in mixotrophic way. RESULTS: The biomass productivities of C. vulgaris cultured in wastewaters containing glucose and NaAc were 63.5 and 55.2 mg L⁻¹ day⁻¹ respectively, which were 2.61‐ and 2.27‐fold larger than that achieved in photoautotrophic condition. Owing to the higher biomass productivity, better performance of nutrient removal was also achieved in wastewater containing glucose or NaAc. Different from glucose and NaAc, protein in the wastewater had no significant effect on C. vulgaris growth and nutrient removal. Chlorella vulgaris cultured in NaAc and glucose wastewaters achieved the highest lipid (17.35 mg L⁻¹ day⁻¹) and carbohydrate (18.75 mg L⁻¹ day⁻¹) productivities respectively, indicating that wastewater containing these two organic substances has certain advantages in microalgal liquid biofuel production. CONCLUSIONS: Organic matters in wastewater have important effects on microalgae growth and the chemical composition of algal cells. Carbohydrates and VFAs in wastewater can significantly promote the growth of C. vulgaris and promote the accumulation of lipid by microalgae. © 2019 Society of Chemical Industry

The purpose of this work was to investigate the viability of a microalgae catalytic pyrolysis/hydrotreating plant to kerosene, diesel and gasoline using Aspen Plus. A series of 2000 dry tonne per day scenarios were simulated with the final goal of determine the price in USD per litre of the drop-in fuels produced and the economic feasibility of the technique at a large-scale. Different scenarios (mechanical, solar and thermal drying), microalgae (Nannochloropsis and Isochrysis) and catalysts (Li-LSX zeolite, Ni-Ce/Al2O3, Ni-Ce/ZrO2). For this work, a systematic design approach by Douglas was considered and the whole process was actualised with the Marshall and Swift Cost Index of 2016. The lowest minimum fuel selling price (1.418 $/L) was found for Isochrysis and Li-LSX-zeolite. Finally, the sensitivity analysis showed that the bio-oil yield was the most influent factor, leading to a variation of the fuel price between 1.158 $/L to 1.751 $/L assuming a 20% of variation. The techno-economic assessment and sensitivity analysis indicated that Isochrysis and Li-LSX-zeolites are promising for the production of drop-in fuels, but further research is required to further reduce the price of the feedstock production and drying to be competitive with lignocellulosic materials.

Blazing of fossil energy resources generally changes the global climate. Speeding up of global temperate nowadays is an important aspect. Emission of greenhouse gases mainly from blazing of fossil energy resources is one of the most important sources. So, to carry the significant energy and to reduce air pollution, biofuels might be a substitute energy sources. The unnecessary utilization of fossil energy resources or fuels results deficient in the storage in underground earth then people naturally have to depend on biofuels. Consequently increasing demand for the manufacture of biofuels will put a huge burden on agriculture and food prices. Biofuels generally attributed as liquid fuels which are made from the biomass. This consists of mostly wood, vegetable oils, forestry products, agricultural crops, agricultural residues or municipal garbage, residues of domestic animal wastes and aquatic plants. In this review, we summarized the different types of biofuels including biodiesel and their comparative study, production and uses from an ecological perspective. © 2019 Chemical Publishing Co.. All rights reserved.

Algae species like Schizochytrium sp. are resilient photosynthetic factories that produce large quantities of fatty acids that can be converted to biodiesel. These lipids must be extracted from the raw biomass before they can be used as biofuel feedstocks or other bioproducts such as hydrogen. In this paper, hydrogen production by steam reforming of schizochytrium algae oil are studied. The effects of continuous microwave and intermittent microwave, freezing and thawing times of different mass fractions, time of alkali heat and other factors on the ratio of cell disruption and ultrasonic-assisted ethanol extraction are considered. The results show that the highest lipid yield can reach by ultrasonic-assisted ethanol extraction from the schizochytrium algae which are pretreated by alkali heat method. The hydrogen production from steam reforming of the lipids, which are extracted by ethanol with ultrasonic-assisted from algae after alkali thermal pretreated is proposed.

Fourth generation biofuel (FGB) uses genetically modified (GM) algae to enhance biofuel production. Although GM algae biofuel is a well-known alternative to fossil fuels, the potential environmental and health-related risks are still of great concern. An evaluation of these concerns and accordingly devising appropriate mitigation strategies to deal with them are important to a successful commercialized production of FGB. While extensive research has been carried out on genetic modification and other technologies that aim to increase the productivity of algae strains, only a handful of them deal with the legislative limitations imposed on exploiting and processing GM algae. This paper examines this legislation and the mitigation strategies to meet potential risks associated with the exploitation and processing of FGB. Open-pond system is an economic solution for large-scale cultivation of microalgae; however, the concern regarding the health and environmental risk of cultivating GM algae and the associated stringent regulations is considered as the main barrier of FGB production. Disposal of the residue is another important issue that should be considered in FGB production. The byproducts obtained from energy extraction step and residual water from the harvesting process may contain plasmid or chromosomal DNA that may cause the risk of lateral gene transfer. Hence an appropriate mitigation practices should be used for replacement of the hazardous water residue and by-products with more environmentally friendly alternatives. The results obtained from several field testing projects for open-environment exploitation of GM algae show that under the various conditions used, there was no apparent proof to support possible horizontal gene transfer in release of GM algae.

The aim of this work was to study algal floway (AFW) to treat urban wastewater and to evaluate biomass productivity, lipid contents and biodiesel production. The results indicated the seasonal average algae productivity of 34.83 g dry weight m2 d−1 with a nutrient removal rate of 2.52 g m2 d−1N and 1.25 g m2 d−1P while the lipid content ranged between 14 and 22% of dry cell weight with the highest lipid productivity of 9.29 g m−2 d−1 during summer. Biodiesel quality was superior during summer with high centane number and cold filter plugging point values. High eicosapentaenoic acid content was found during winter growth cycles. AFW algae community was dominated by pennate diatoms during all growing seasons. This study is one of its kinds in Indian wastewaters and it provides fundamental information for further optimization and use of AFW to treat domestic wastewater and to produce algae biofuel feedstock.

Biofuels are the promising alternative to exhaustible, environmentally unsafe fossil fuels. Algal biomass is attractive raw for biofuel production. Its cultivation does not compete for cropland with agricultural growing of food crop for biofuel and does not require complex treatment methods in comparison with lignocellulose-enriched biomass. Many microalgae are mixotrophs, so they can be used as energy source and as sewage purifier simultaneously. One of the main steps for algal biofuel fabrication is the cultivation of biomass. Photobioreactors and open-air systems are used for this purpose. The formers allow the careful cultivation control, but the latter ones are cheaper and simpler. Biomass conversion processes may be divided to the thermochemical, chemical, biochemical methods and direct combustion. For biodiesel production, triglyceride-enriched biomass undergoes transetherification. For bioalcohol production, biomass is subjected to fermentation. There are three methods of biohydrogen production in the microalgal cells: direct biophotolysis, indirect biophotolysis, fermentation.

Algal biofuel is considered as an alternative to fossil fuels. Due to the structure simplicity and genetic tractability of many microalgae, they are also gradually recognized as an ideal factory for the production of various metabolites of high commercial values. In this mini-review, we attempt to summarize recent development on metabolic engineering of microalgae to explore their metabolic versatility for the production of hydrogen, carbohydrates, terpenes, fatty acids, alcohols, aliphatic alkanes and alkenes. In addition, we also present key challenges facing algal engineering, and propose a few strategies that could leverage the advancement in systems biology and genomics. We foresee a bright future for microalgae studies to advance both research and technology development.

As an effort to develop affordable and sustainable energy sources, algae-derived biofuels have attracted considerable interest. As use of individual conversion processes targeting a subset of bioch...

The use of fossil fuels for energy demands is insufficient for escalating demands as they are limited in nature and are not environment friendly. Various microbial sources are under scanner for clean energy production out of which algae comes as a promising one. Production of biohydrogen from algae has brought a lot of hopes in the energy production sector. Algae are powerhouse of renewable chemicals including biofuel precursors. Biohydrogen is one of such biofuel precursors; it proves to be a clean and sustainable fuel and can be produced in industries. Currently however, it cannot stand up to the present energy demands of the world due to certain obstacles, such as cost effectiveness, storage and transportation of hydrogen. One of the main hurdles in algal biofuel technology is the rigid nature of algal cell wall. To get around this, pretreatment of algal biomass is imperative to overcome productivity issues, so as not to compromise biofuel yield. Improving the biofuel production at every step can make a huge difference in outcomes and thus comes up as a promising tool. Therefore, in the present state of art review, various methods of algal biomass pretreatment, different enzymes involved in hydrogen production, various factors influencing hydrogen production from algae and genetic engineering avenues have been discussed in brief.

Carbon dioxide gas is the key element of the carbon cycle and a major source for photosynthesis, but for the past 150 years, the atmospheric CO2 has been increased drastically from 250 to 418 ppm due to the extreme utilization of fossil fuels. This accelerated release of CO2 acts as a major source for climatic change due to the greenhouse gas effect resulting in global warming and melting of polar ice caps, alteration in biogeochemical cycles, altered rainfall, ocean acidification, eutrophication of lakes, imbalance in the ecological communities and extinction of some species, effects on soil fertility, changes in the metabolism and at the molecular level. Reduce, reuse and recycle strategy can be applied to control elevated CO2 levels by preventing deforestation, using renewable energy as an alternative for fossil fuels and reusing the atmospheric CO2. Carbon capture and storage (CCS), Carbon capture and utilization (CCU) are the two technologies adapted to capture the atmospheric CO2, utilize it, and focus on permanent storage in the geological sites. Captured CO2 is used to produce many value added products such as polymers, biofuels, reactants etc. Plants and microorganisms act as a natural CO2 filter. Several biomolecules such as carbohydrates, proteins, and lipids are produced due to the biological carbon fixation process using photosynthesis. Six different photosynthetic pathways and some non-photosynthetic pathways to fix atmospheric CO2 have been reported in diverse species of plants and microbes such as bacteria, fungi, yeast, algae etc. Algae are the most potent microbe in CO2 utilization and biological carbon fixation compared to other microbes and used widely on a large industrial scale for biofuel production. Algal biofuel production using captured CO2 is the best productive method to recycle and reduce atmospheric CO2.

This chapter introduces a brief description of the microalgal cell, its presence, its constituents with the benefits of each, the applied technologies of biofuel production and biorefineries through a scope of the physical possibilities in Egypt. Microalgal biomass contains sufficient amounts of carbohydrates and oil for biofuel production especially biodiesel. The technical conversion options for biomass into biofuel can be categorized into three basic methods: chemical, thermochemical, and biochemical conversion. The desired product and the form of energy are the main factors that influence the choice of a specific conversion. Production of algal valuable products such as algal bioactive compounds and algal biofuel products will be presented briefly in this chapter. As a conclusion, the production of the biofuel conforming to ASTM specifications can be achieved by the selection of a techno-economically feasible technology. The feasibility can be performed using microalgal oil after the extraction of valuable products previous to use the remaining oil for biofuel production.

The exhaustion of limited fossil fuel resources and the overwhelming emissions of toxic gases from these fuels cause extensive damage to the environment. The world is focusing at replacing fossil fuels with clean energy production. Biofuels are eco-friendly and renewable energy and hence have received the attention of researchers around the globe as an alternate source of energy. Annually, the production of biofuels increases by 5% and is estimated to reach 50 million m3 of biofuel by 2025. The downsides of the first and second generations of biofuels resulted in the creation of a third generation of biofuel from algal sources. The major advantages of using algae as feedstock include low cost and the utilization of a high level of CO2 in the atmosphere, which make algae a good choice for biofuel production. Nanomaterials support and enhance biomass growth and improve harvesting efficiency in a short time.

The rising need for energy due to the increase in the population and its desire for higher living standards has emerged as one of the major problems for scientists. In the past few years, the diversification of bioenergy sources isn’t able to come up to the commercialization step; this has emerged as an important energy issue. The researches based on third-generation bioenergy production from algal biomass have emerged as the most potential resource among all the resources that minimize the drawbacks of the first- and second-generation bioenergy. Algal biomass is considered for the economic production of bioenergy like bioethanol, biodiesel, biohydrogen, biogas, and other co-products. This potential of algae is due to its high growth rate, CO2 utilization, less greenhouse gas (GHG) emission, and ability to store a high amount of carbohydrates and lipids. In this chapter, we will study the importance of algal biomass in terms of improved bioenergy production. This chapter discusses different recent development and findings for high algae cultivation with enhanced cell content especially lipids, various harvesting techniques, oil extraction methods, and algal oil to bioenergy conversion techniques.

Microalgae are increasingly used in the production of various industrial chemicals. Lipids from major microalgae crops are similar to lipids obtained from oilseed plants and can be converted into biodiesel, moreover, microalgae are more advantageous than plants in oil production in many ways. Therefore, oil and biodiesel production technology from microalgae is a current and interesting research topic. The effect of salinity in the nutrient medium on the growth and lipid productivity of marine microalgae Dunaliella tertiolecta was investigated. The usability of Marmara Seawater (MSW) as a growth medium and its suita-bility for microalgae were also investigated. The highest cell concentration (1.53gdw / L), growth rate (μmax = 0.006h-1) and oil productivity (12.8 (g / L. Day) (10-3)) in nutrient medium (5g) were obtained. On the other hand, the cetane number was calculated according to the dominant arachidic acid (C20:0), it was determined as 74.9 and the average molecular weight of the oil was calculated as 849.1 g / mol. Ac-cording to the experimental results, it is predicted that microalgae lipids will be widely used as an alterna-tive to vegetable oils soon as raw materials.

Fossil fuels are used for the generation of electrical power, as well as liquid fuels. There are a variety of renewable or low atmospheric pollution technologies that can generate electrical power, including solar, wind, hydroelectric, geothermal, and nuclear. However, renewable technologies to supplement or replace liquid fossil fuels are still in their early developmental stages. The International Energy Agency expects that biofuels will contribute 6% of total fuel use by 2030, but could expand significantly if undeveloped petroleum fields are not accessed or if substantial new fields are not identified. The use of liquid fossil fuel as an energy source has long been considered unsustainable and most importantly the liquid fossil fuel will be diminished by the middle of this century. In addition, the fossil fuel is directly related to environmental degradation and greenhouse emission. Biofuel produced from plants, animals, or algae products can offer an alternative to reduce our dependency on fossil fuel and assist to maintain healthy global environment. Microalgae are becoming popular candidate for biofuel production due to their high lipid contents, ease of cultivation, and rapid growth rate. Fatty acid methyl esters (FAME) are used as alternative diesel fuel originating from renewable sources. The attention is focused on the materials that do not compete with food and feed production. Algae have a significant potential as an alternative biodiesel feedstock. In comparison to other crops, they have the advantage in very fast reproduction cycles, enhanced resistance to high UV radiation doses, and higher effectiveness of energy conversion to biomass due to low demands on other metabolic functions. Moreover, they fix atmospheric CO2 very efficiently. Microalgae have benefit over other sources of biofuel as it fixes atmospheric CO2 very efficiently and also fulfill liquid fuel demand for present as well as future generation.

Massive utilization of the fossil fuels has caused the unwanted release of many harmful pollutants to the environment. The consequent increment of the environmental pollutions has raised many environmental issues to the escalating populations. The impressing issue can be minimized by adopting alternative renewable biofuel resources. However, the bioprocessing of biofuels production such as biodiesel, bioethanol, biobutanol, biohydrogen, and biogas needs to be efficient and improved.

Algae offer an appealing source for creating inexhaustible and feasible biofuels to diesel engine. Researchers evaluated the performance of algae and microalgae biodiesel in various types of diesel engine and reported that engine characteristics of algae biodiesel (B20 blend) are closer to baseline (diesel) fuel but NOX emission is increased for algae and microalgae biodiesel blend in diesel engine. With the purpose to reduce the NOX emission, addition of ignition promoting additive with B20 blend is viable solution without engine modification. In this study, B20 (80% of diesel and 20% algae biodiesel on volume basis) is blended with 5% of di-ethyl ether (DEE), 2-ethylhexyl nitrate (2-EHN) and di-tertiary butyl peroxide (DTBP), namely B20 + 5% DEE, B20 + 5% 2-EHN and B20 + 5% DTBP, respectively, and the impact of the ignition improvers on the engine performance and emission characteristics of biodiesel-fueled diesel engine was examined for the fuel blends. The outcomes demonstrated that the addition of DEE, 2-EHN and DTBP in biodiesel enhanced the performance and emission characteristics of DICI engine and this study concluded that the DTBP can be utilized as promising ignition enhancer for diesel–algae biodiesel blend to compare with DEE and 2-EHN.

Algae is a promising feedstock for biofuels. Because scaling up the production of algae-based biofuels consumes a significant amount of water, it is important to consider the impact it has on water stress. This study evaluates the potential for algae-derived biofuel production in the United States (US) and considers regional water stress. We used the Biomass Assessment Tool (BAT) to identify potential sites in the US that meet land, biomass productivity, and CO2 co-locating criteria. We quantify the water stress impacts of algal biofuel production in terms of water scarcity footprint using water consumption from BAT, and the water stress indicator from Available Water Remaining for the US (AWARE-US) system. We assess long-term (20 billion gal per year [BGY]) and near-term (5 BGY by 2030) renewable diesel (RD) production targets. To select suitable algae sites, we consider biomass yield and water use with and without water stress constraints. We found that ranking sites based on biomass yield results in a high water stress impact (24.5 × 103 US equivalent BGY [BGYe]) for the long-term RD target. If we instead rank sites on water use efficiency, water consumption decreases on average by 62%, with an average reduction in biomass yield of 25%. To reconcile tradeoffs between biomass yield and water stress impacts, water stress indicator (AWARE-US) that represents relative water availability by region can be applied while considering biomass yield. This strategy removes sites located in water-stressed areas and keeps high-productivity sites. For the long-term RD target, this reduces water stress impacts by 55% (13.8 BGYe) without lowering yield or 97% (24.2 BGYe) with moderately lower (4%) yield, compared to the sites ranked by biomass yield alone. The results demonstrate that incorporating water stress into energy-scale algae biofuel production planning is key to achieving synergies between biofuel yield and fresh water stress impacts.

There are many challenges and technical barriers to implementation of a viable commercial process to produce algae-based biofuels. Biofuels made from algae must typically go through a complicated series of unit processes for algae cultivation, harvesting, dewatering, oil extraction, conversion, and other logistical steps. The National Alliance for Advanced Biofuels and Bioproducts (NAABB) was developed to produce new technologies to be implemented by the algal biofuel industry in an effort to improve the process economics and environmental benefits associated with algae fuels. This LCA study investigated the environmental impacts associated with four harvesting and two extraction technologies developed by NAABB researchers. Gate-to-gate LCA results show that all novel technologies appear to have the potential to provide at least modest decreases in greenhouse gas (GHG) emissions compared to current default algae process technologies. 14 scenarios of different combinations of harvesting and extraction unit operations were further evaluated in the context of the full life cycle for producing algae-based renewable diesel. Results indicate that selection of a particular technology for a unit operation can have consequences that affect other stages of the full biofuels life cycle, both upstream and downstream from the unit operation in question. Considering material and energy inputs, operation efficiency, impacts on on-site recycled energy, and co-products credits, acoustic harvesting followed by acoustic oil extraction give the best performance on the overall lifecycle, which reduce the GHG emissions by roughly 45% compared to the base case. LCA modeling also demonstrates that co-products produced at various points of the value chain, for use within or outside the algae biofuels system boundary, considerably affect the LCA results beyond harvesting and extraction unit processes.