Microalgae Biofuel Research Articles

Techno‐Economic Assessment of a Microalgae Biorefinery

AbstractA preliminary techno‐economic assessment of a microalgae biorefinery plant is reported, with pulsed electric field treatment (PEF) hydrothermal liquefaction as core technology. The results indicate that standalone production of microalgae biofuel would lead to an annual loss of 2.615 M€. PEF treatment could improve this scenario by bringing the microalgae biofuel to a competitive level (0.78 € kg−1). Assuming that microalgae biofuel would be sold at the price of crude oil (0.44 € kg−1), the minimum price of the amino‐acid based product should be 7.56 € L−1 for positive capital returns.

Emerging Technologies for Enhancing Microalgae Biofuel Production: Recent Progress, Barriers, and Limitations

The world has heavily relied on fossil fuels for decades to supply energy demands. However, the usage of fossil fuels has been strongly correlated with impactful problems, which lead to global warming. Moreover, the excessive use of fossil fuels has led to their rapid depletion. Hence, exploring other renewable and sustainable alternatives to fossil fuels is imperative. One of the most sustainable fossil fuel alternatives is biofuel. Microalgae-based biofuels are receiving the attention of researchers due to their numerous advantages compared with those obtained from other types of feedstocks. Hence, it is essential to explore the recent technologies for biofuel produced from microalgae species and define the possible challenges that might be faced during this process. Therefore, this work presents the recent advancements in biofuel production from microalgae, focusing on emerging technologies such as those using nanomaterials and genetic engineering. This review focuses on the impact of nanoparticles on the harvesting efficiency of various microalgae species and the influence of nanoparticles on biofuel production. The genetic screening performed by genome-scale mutant libraries and their high-throughput screening may assist in developing effective strategies for enhancing microalgal strains and oil production through the modification of enzymes. Furthermore, the barriers that limit the production of biofuels from microalgae are introduced. Even though microalgae-based biofuels are perceived to engage with low negative impacts on the environment, this review paper touches on several environmental issues associated with the cultivation and harvesting of microalgae species. Moreover, the economic and technical feasibility limits the production of microalgae-based biofuels.

Microalgae Biomass and Lipids as Feedstock for Biofuels: Sustainable Biotechnology Strategies

Microalgae exhibit remarkable potential as a feedstock for biofuel production compared with other sources, owing to their high areal productivity, low environmental effect, and negligible influence on food security. However, the primary obstacle to the commercialization of algae-based biofuels is the high economic cost due to the low-yield lipid content in the microalgae biomass. Maximizing biomass and lipid production is crucial to improve the economic viability of microalgae for biofuels. Identifying appropriate algal strains, particularly from indigenous environments, and developing those ‘platform strains’ using mutagenesis and genetic-engineering techniques is preferable. The provided discussion of conventional methods to increase microalgae’s biomass and lipid productivity mostly entailed adjusting environmental (such as temperature, light, and salinity) and nutritional (such as nitrogen and phosphorus) parameters. This review illustrated a comprehensive overview of biotechnological approaches and the recent strategies to enhance the lipid productivity of microalgae. The research also emphasized the need to streamline engineering strategies with the aid of recent advancements in DNA-manipulation techniques to hinder the existing biological intricacies in lipogenesis. This review also discussed the current economic and commercialization of this algal biorefinery along with the drawbacks.

Bioethanol production from microalgae biomass at high-solids loadings

Industrial adoption of microalgae biofuel technology has always been hindered by its economic viability. To increase the feasibility of bioethanol production from microalgae, fermentation was applied to Chlorella vulgaris FSP-E biomass at high-solids loading conditions. First, Chlorella vulgaris FSP-E was cultivated to produce microalgae biomass with high carbohydrate content. Next, different ethanol-producing microorganisms were screened. Saccharomyces cerevisiae FAY-1 showed no inhibition when fermenting high initial glucose concentrations and was selected for the fermentation experiments at high-solids loadings. Optimization of acid hydrolysis at high biomass loading was also performed. The fermentation of microalgal biomass hydrolysate produced a final ethanol concentration and yield higher than most reported literature using microalgae feedstock. In addition, the kinetics of bioethanol fermentation of microalgae hydrolysate under high-solids loading were evaluated. These results showed the potential of fermenting microalgae biomass at high-solids loading in improving the viability of microalgae bioethanol production.

Development of a Model for the Implementation of the Circular Economy in Desert Coastal Regions

Food production is the main challenge for developing arid regions due to the restricted access to fresh water. This study combines the environmental know-how of two coastal desert regions on the American continent with similar geographical characteristics to propose a general model for a circular economy in stressed environmental conditions. The Atacama Desert, located in Chile, is the driest place on Earth. Due to the lack of rainfall in decades, the possibility of growing food is almost impossible. The Desert of Sonora, in the northwest of Mexico, is known for its extreme aridity and temperatures over 50 °C in summer. Both deserts have continuously growing cities ranging from 400,000 to 900,000 inhabitants, where access to and management of freshwater represents an issue. A circular economy model was developed. Critical parameters for this model considered: the utilisation of solar energy for water desalination and energy production, integrated with hydroponic farming and water dosing with hydrogels for food production; microalgae for biofuels; seaweed for biochemicals; anaerobic digestion for organic waste management and nutrient recovery from wastewater sludge treatment. Regional policies and governance are needed to incentivise the adoption of circular economy models.

Screening of the heterotrophic microalgae strain for the reclamation of acid producing wastewater

For the sustainable development of the environment, to reduce the high cost and low productivity of microalgae biofuel, nine microalgae strains were screened to study the growh and nutrient removal properties under heterotrophic culture by using the waste carbon source of volatile fatty acids (VFAs). Chlorella sorokiniana (C.sorokiniana) was selected as the best strain with the highest biomass concentration of 0.77 g L−1, specific growth rate of 0.25 d−1, biomass productivity of 91.43 mg L−1 d−1, total nitrogen removal efficiency of 95.96% and total phosphorus removal efficiency of 93.42%. To study the utilization potential of acid-producing wastewater by heterotrophic microalgae, actual acid-producing wastewater was recycled three times for the utilization of C.sorokiniana. After the three utilization cultivation, the removal rates of COD, total nitrogen, ammonia nitrogen, and total phosphorus were 74.44%, 88.05%, 79.08%, and 82.69%, respectively. The total utilization rates of acetic acid, propionic acid, and butyric acid were 58.99%, 70.54%, and 81.52%, respectively. In addition, the highest lipid content of 39.15% and protein content of 42.43% achieved at the third cultivation. After the first cultivation, the composition and diversity of the microbial community structure changed dramatically, with Protebacteria, Bacteroidota, Hydrogenophaga, and Algoriphagus becoming enriched. These results showed a promising way of coupling wastewater treatment with biomass production for long-term sustainability of microalgae lipid production.

Sustainable integration of biofuel generation and domestic wastewater treatment by <em>chlorella vulgaris</em>

The production of microalgae biofuels has become promising because it is a renewable, non-polluting and non-competitive source such as food growing areas. This work has the objective of using the effluents generated by the Lorena Engineering School - EEL / USP as a growth medium for microalgae of the Chlorella vulgaris species, aiming at lipid production and treatment of effluents. The laps were completed in photobioreactor with effluent from the collection on alternate days. C. vulgaris showed good adaptation to the effluent, reaching a cell density of 1.92x107 cells.mL-1 and a dry biomass concentration of 1.74 g.L-1. The lipid content per gram of biomass was 0.095 to 0.164 mg.g-1. Concomitantly, between 54% and 78.74% of nitrate was dismissed and the chemical oxygen demand (COD) fell between 17.73% and 36.13%. With the results of statistical analysis (ANOVA and Tukey's test). Although lipid has been lower, the success of the microalga Chlorella vulgaris in this sense must have been similar to that of the same.

Life cycle evaluation of microalgae based biorefinery supply network: A sustainable multi-criteria approach

Due to enjoying such features as ability to produce high volumes of oil and reducing and eliminating environment carbon dioxide, microalgae is a promising solution for producing biofuels. In order to help the commercialization of this emerging industry, the present study offers a sustainable mixed integer linear programming model (MILP) for designing and planning microalgae biofuel production and distribution network. As objective functions, this model considers minimizing the total cost of the network and maximizing greenhouse gas emission saving simultaneously. In order to design microalgae biofuel sustainable production and distribution network, a two-stage approach is developed. In order to reduce computational complexity, at first place, data envelopment analysis approach (DEA) and Combinative Distance-Based Assessment (CODAS) approach as well as best worst method (BWM) are developed respectively for determining the location of suitable candidates for establishing microalgae production facilities and constructing biorefinery based on economic, social and environmental criteria. In the second stage, the environmental effects of microalgae biofuel supply chain network are measured using one of the newest and most effective methods that is based upon environmental life cycle assessment as well as OpenLCA software and then followed by formulizing a bi-objective linear programming model. For solving the offered model, augmented epsilon constraint method is used. Finally, a realistic case study conducted at national level concerning microalgae biofuel supply chain. The results indicate that based on the offered model by replacing fossil fuels with biofuel we can achieve greenhouse gases emission saving by 99 %.

Microalgal biofuels: Pathways towards a positive energy balance

Current microalgae biofuel production pathways are still far from being energetically self-sufficient. Simulations scenarios (1 t·y−1 of biomass) under a purely energetic perspective, have revealed some bottlenecks mainly in the cultivation and metabolite recovery processes. Technologies such as intensified photobioreactors such as AlgoFilm©, infrared light filtering units, photovoltaic panels, solvent-free metabolite recovery processes, and high biomass concentration treatments at⩾145 kg·m−3 are suggested and discussed to also have a major contribution on the net energy ratio of the process. An energy-driven biorefinery approach has been proposed to increase the energy output by obtaining bioethanol and biodiesel liquid fuels, but also photovoltaic energy during the same production process. The latter may also compensate for the large amounts of energy consumed in typical operations of the wet-pathway processes like harvesting-concentration, cell disruption, or solvent recycling processes. This perspective increased the final volume of liquid biofuels up to 57%. It was found a maximum net energy ratio of 1.9 for a double biofuel process, and 8.5 if photovoltaic energy is also considered.

Selection of Tropical Microalgae Species for Mass Production Based on Lipid and Fatty Acid Profiles

Numerous recent studies have identified microalgae biofuel as one of the major renewable energy sources for sustainable development due to their high biomass productivity, high lipid content, and availability of locally adapted strains in various geographical locations. There have been minimal studies on the fatty acid composition of lipid production on local microalgae species in Sabah, Malaysia. Thus, screening for local microalgae species capable of producing biodiesel can aid in the selection of suitable species. This study aimed to isolate and identify promising local microalga as biodiesel feedstock for mass cultivation. Eight microalgae species,Acutodesmus obliquus,Chaetoceros muelleri,Isochrysis galbana,Ankistrodesmus falcatus,Chlamydomonas monadina,Chlorella emersonii,Nannochloropsis oculata, andTetraselmis chuii,were successfully isolated and identified from Kota Kinabalu, Sabah. The isolated microalgae were characterized based on the lipid/biomass productivity, lipid content and fatty acid profiles. These isolates had biomass productivity of 0.11–0.78 g/L/day, lipid content of 11.69–39.00% dry weight, and lipid productivity of 21.11–252.64 mg/L/day. According to GC-MS analyses, four isolates produced more than 80% of C14–C18fatty acids, which wereA. falcatus(95%),C. emersonii(93%),A. obliquus(91%), andC. muelleri(81%). Despite its low biomass productivity,C. muelleriwas chosen as the best biodiesel species candidate because of its moderately high lipid productivity (42.90 mg/L/day), highest lipid content (39% dry weight), high level of MUFAs and C14–C18FAs (81.47%), with the highest oleic acid proportion (28.38%), all of which are desirable characteristics for producing high-quality biodiesel.

Valorization of fish bone waste as novel bioflocculant for rapid microalgae harvesting: Experimental evaluation and modelling using back propagation artificial neural network

Harvesting of microalgae biomass is identified as one of the bottlenecks in microalgae biofuel industry due to expensive and energy-intensive dewatering technologies. Alternatively, flocculation process using bioflocculants have given much attention in recent years as green substitutes over chemical flocculants. In this study, bioflocculant was extracted from waste fish bone using mild acid to harvest the freshwater microalgae, Chlorella vulgaris. The optimum flocculation occurred at pH of 9.8 and 50 °C using fish bone bioflocculant which led to flocculation efficiency of 97.65%. To predict complex processes such as microalgae flocculation, artificial neural network (ANN) was employed. Bayesian regularization model with a topology of 2-10-1 showed high correlation coefficients, R2 of more than 0.98, which indicated that the model was significant and robust in identification of the optimum conditions. Characterizations of fish bone bioflocculant and biofloc confirmed the involvement of potassium and other cations as well as carbohydrate and protein substances to flocculate C. vulgaris cells, employing sweeping and charge neutralization as key mechanisms. This finding proposed a valuable reference for practical and rapid harvesting of microalgae using low-cost bioflocculant and the ANN algorithm can be applied in microalgae processing industries for making crucial assessments regarding the process operating conditions.

High-efficiency biofuel production by mixing seawater and domestic sewage to culture freshwater microalgae

Although microalgae biofuel has many advantages, its production is faced with difficulties regarding algal cell harvesting and low lipid content. In this experiment, mixtures of seawater and domestic sewage were prepared for the cultivation of freshwater microalgae. The results showed that the proportion of seawater had an important effect on the precipitation and biofuel production of the microalgae. The increasing proportion of seawater in the mixed wastewater improved the sedimentation performance and lipid content of microalgae, but the growth of microalgae was greatly inhibited under 80% seawater stress. Therefore, the highest algal lipid productivity of 10.74 mg L-1 d-1 was achieved in the wastewater containing 60% seawater, which was 2.15-fold higher than that of the control. Furthermore, the fatty acid saturation and the C16-C18 fatty acid proportion of the microalgae cultured in wastewater containing 60% seawater were relatively ideal, which was beneficial for improving the quality of biodiesel. Therefore, wastewater containing 60% seawater was the most favourable for the cultivation of biofuel-producing microalgae. The mechanism by which seawater improved the precipitation performance of freshwater microalgae was also investigated. The addition of seawater to the sewage increased the cell diameter of the microalgae, reduced the zeta potential of microalgal colloids, and promoted the synthesis of extracellular polymeric substances by the microalgal cells. Thus, the precipitation performance of the microalgae cells was effectively improved. The pigment contents and antioxidant enzyme activities of the microalgae were also determined, and it was found that the glutathione peroxidase activity of microalgae increased under certain seawater stress, indicating that glutathione peroxidase played an indispensable role in the removal of reactive oxygen species produced by seawater stress.

Kinetics and Characterization of Microalgae Biofuel by Microwave-assisted Pyrolysis Using Activated Carbon

The reaction kinetics and the effect of power on microwave-assisted pyrolysis (MAP) in converting microalgae to biofuel were investigated to determine the decomposition mechanism and then characterize the best product. The resulting product consisted of three phases, namely liquid phase (bio-oil), solid residue (char), and uncondensable gas products. The results showed that the optimal increase in microwave power obtained was 20.57% with a 600-watt microwave power condition, a reaction time of 20 minutes, a microwave absorber to microalgae ratio of 1:6, and a heating rate of 25.96 K/min (600 watts). The reaction kinetics evaluated in the best condition showed a second-order reaction with activition energy (Ea) and pre-exponential factor (A) at 35.5971 kJ/moles and 2,606.75/minute, respectively. The characteristics of the biofuel product obtained were 1.01 gr/mL density, viscosity 10.97 cP, and pH 9.30. In addition, based on GC-MS analysis, the bio-oil contained aliphatic, aromatic, phenol, FAME, and polycyclic aromatic hydrocarbon (PAH) organic compounds. These results indicate that MAP has the potential to be developed as an alternative production process for biofuels.

Lipid extraction from microalgae using pure caprolactam-based ionic liquids and with organic co-solvent

Background The main process limitation of microalgae biofuel technology is lack of cost-effective and efficient lipid extraction methods. Thus, the aim of this study was to investigate the effectiveness and efficiency of six caprolactam-based ionic liquids (CPILs) namely, Caprolactamium chloride, Caprolactamium methyl sulphonate, Caprolactamium trifluoromethane sulfonate, Caprolactamium acetate, Caprolactamium hydrogen sulphate and Caprolactamium trifluoromethane-acetate—for extraction of lipids from wet and dry Spirulina platensis microalgae biomass. Of these, the first three are novel CPILs. Methods The caprolactam-based ionic liquids (CPILs) were formed by a combination of caprolactam with different organic and inorganic Brønsted acids, and used for lipid extraction from wet and dry S. platensis microalgae biomass. Extraction of microalgae was performed in a reflux at 95 °C for 2 h using pure CPILs and mixtures of CPIL with methanol (as co-solvent) in a ratio of 1:1 (w/w). The microalgae biomass was mixed with the ILs/ methanol in a ratio of 1:19 (w/w) under magnetic stirring. Results The yield by control experiment from dry and wet biomass was found to be 9.5% and 4.1%, respectively. A lipid recovery of 10% from dry biomass was recorded with both caprolactamium acetate (CPAA) and caprolactamium trifluoroacetate (CPTFA), followed by caprolactamium chloride (CPHA, 9.3 ± 0.1%). When the CPILs were mixed with methanol, observable lipids’ yield enhancement of 14% and 8% (CPAA), 13% and 5% (CPTFA), and 11% and 6% (CPHA) were recorded from dry and wet biomass, respectively. The fatty acid composition showed that C16 and C18 were dominant, and this is comparable to results obtained from the traditional solvent (methanol-hexane) extraction method. The lower level of pigments in the lipids extracted with CPHA and CPTFA is one of the advantages of using CPILs because they lower the cost of biodiesel production by reducing the purification steps. Conclusion In conclusion, the three CPILs, CPAA, CPHA and CPTFA can be considered as promising green solvents in terms of energy and cost saving in the lipid extraction and thus biodiesel production process.

Biofuel recovery from microalgae biomass grown in dairy wastewater treated with activated sludge: The next step in sustainable production

Microalgae biofuel could be the next step in avoiding the excessive use of fossil fuels and reducing negative impacts on the environment. In the present study, two species of microalgae (Scenedesmus obliquus and Chlorella vulgaris) were used for biomass production, grown in dairy wastewater treated by activated sludge systems. The photobioreactors were operated in batch and in continuous mode. The dry biomass produced was in the range of 2.30 to 3.10 g L−1. The highest volumetric yields for lipids and carbohydrates were 0.068 and 0.114 g L−1 day−1. Maximum CO2 biofixation (750 mg L−1 day−1) was obtained in continuous mode. The maximum values for lipids (21%) and carbohydrates (39%) were recorded in the batch process with species Scenedesmus obliquus. In all of the experiments, the Linolenic acid concentration (C18:3) was greater than 12%, achieving satisfactory oxidative stability and good quality. Projected biofuel production could vary between 4,863,708 kg and 9,246,456 kg year−1 if all the dairy wastewater produced in Brazil were used for this purpose. Two hectares would be needed to produce 24,99 × 109 L year−1 of microalgae bioethanol, a far lower value than used in cultivating sugar cane. If all dairy wastewater generated annually in Brazil were used to produce microalgae biomass, it would be possible to obtain approximately 30,609 to 53,647 barrels of biodiesel per year. These data show that only by using dairy wastewater would biofuels be produced to replace 17% to 40% of the fossil fuels currently used in Brazil.

On the Theoretical Prediction of Microalgae Growth for Parallel Flow

The established microalgae growth models are semi-empirical or considerable fitting coefficients exist currently. Therefore, the ability of the model prediction is reduced by the numerous fitting coefficients. Furthermore, the predicted results of the established models are dependent on the size of the photobioreactor (PBR), light intensity, flow and concentration field. The growth mechanism of microalgae has not clearly understood in PBR cultivation. It is difficult to predict the microalgae growth by theoretical methods, owing to the aforementioned factors. We developed an exploratory bridging microalgae growth model to predict the microalgae growth rate in PBRs by using the nondimensional method which is effectively in fluid dynamics and heat transfer. The analytical solution of the growth rate was obtained for the parallel flow. The nondimensional growth rate expressed as function of Reynolds number and Schmidt number, which can be used for arbitrary parallel flow due to the solution was expressed as nondimensional quantities. The theoretically predicted growth rate is compared with the experimentally measured microalgae growth rate on the order of magnitude. The nondimensional method successfully applied to the microalgae growth problem for the first time. The general nondimensional solution can unify the numerous experimental data for different laboratory conditions, and give a direction for the disorder of the microalgae growth problem. The nondimensional solution may be useful to explain the growth mechanism of microalgae and design large-scale PBRs for microalgae biofuel production. The significance of the work is to give a theoretical foundation and methodology of biological theory of microalgae growth.

The potential of seaweed for carbon capture

Abstract Macroalgae (seaweeds) are drawing interest as potential tools for climate mitigation within a burgeoning blue carbon agenda. With the high rates of net primary productivity, they are one of the main carbon sinks in the global ocean, both as biomass standing stock and as vectors of carbon export through detritus pathways. When coupled with their intrinsic ecological value, their contribution to coastal economies, and their current and future scope for aquaculture production, it is perhaps unsurprising that macroalgae have become a focus for nature-based carbon sequestration. However, the research community must guard against the hyperbole that is beginning to permeate the conversation, such as that which beset the microalgae biofuel movement. Macroalgae undoubtedly have a role to play in combating carbon pollution, and perhaps before significant investment is committed to ramping up macroalgae aquaculture, a more pragmatic view of its contribution to natural capital is justified. This article takes an objective look at the capacity for macroalgae to fill a global carbon sequestration niche, both as managed natural carbon pools and as deployable carbon capture assets.

Vibration, acoustic and emission characteristics of the chlorella vulgaris microalgae oil in compression ignition engine to mitigate environmental pollution

The petroleum fuel demand with high price and its exhaustion imposes a pressure to find an alternative. The fossil fuel shortage has been deteriorating over the past few years, because of the rapid increase in population. Many attempts have been made to increase the quality of biofuel with additives. In this paper, two types of nanoparticles such as carbon nanotubes (CNT) and alumina (Al2O3) in chlorella microalgae biofuel were analyzed by experimental method. The added CNT and alumina act as a catalyst that induces complete combustion with retarded emissions. In addition to above, the noise and vibration qualities are also measured. A series of test conducted using single cylinders, four stroke, naturally aspirated compression ignition diesel engine was run by using pure diesel and also different fuel blends ‘such as B10CNT50A50 Chlorella (Microalgae Biodiesel 10% + Diesel 90% + CNT 50 ppm), B20CNT50A50 (Microalgae Biodiesel 20% + Diesel 80% + CNT 50 ppm + Al2O3 50 ppm) and B30CNT50A50 (Microalgae Biodiesel 30% + Diesel 70% + CNT 50 ppm + Al2O3 50 ppm). At a constant load condition, all experimental tests were conducted at four different speeds such as 1500 rpm, 2000 rpm, 2500 rpm and 3000 rpm. The reference fuel of diesel B0 results was compared with blended fuel. From the results, it has been found that the nano additives of CNT and alumina reduced the greenhouse gas emissions of CO compared to plain diesel. Only considering the blended fuel, as the percentage of biofuel increases, the emission of nitric oxide and carbon dioxide is decreased with significant reduction in the amount of noise and vibration and also the combustion and performance qualities were also improved. The highest benefit in terms of all factors was achieved in the fuel blend of B30A50CNT50 amongst the other blends.

Sustainability evaluation of microalgae biodiesel production process integrated with nutrient close-loop pathway based on emergy analysis method

To make comprehensive assessment on sustainability of microalgae biofuel production process integrated with nutrient close-loop pathways, Emergy Analysis methodology was adopted based on case studies: microalgae biodiesel production integrated with Nutrient Recycling Pathway in Case A and microalgae biodiesel production integrated with Protein Production as By-Product Pathway in Case B. Emergy results show that microalgae biodiesel system integrated with Nutrient Recycling Pathway is more sustainable, and factor analysis shows that water source with higher unit emergy value and electricity with lower one are more favorable to improve sustainability performance of the integrated process. Besides, different generations of biofuel are also assessed by Emergy Analysis method, and the third-generation biodiesel shows the most sustainable potentials than the previous.

Life cycle and techno-economic assessment of source-separated wastewater-integrated microalgae biofuel production plant: A nutrient organization approach

Microalgae cultivating in wastewater enabling nutrient uptake for biomass and biofuel generation is regarded as a promising pathway to increase sustainability of microalgae biofuel production process. A source-separated nutrient organization approach for the process of wastewater-based microalgae biofuel is proposed in this study. Comparative life cycle assessment (LCA) method and Techno-economic analysis (TEA) approach are employed to assess sustainability and economic performance of the proposed nutrient approach. Two scenarios are used to validate our study. Scenario 1 is based on the source-separated nutrient delivery approach with microalgae integrated wastewater in tertiary treatment. Scenario 2 is based on non-separated-point nutrient delivery policy and microalgae integrated with secondary wastewater treatment. The results show that the source-separated nutrient approach is effective for reducing the environmental impacts and increasing commercial potential of microalgae biofuel.