Microalgae For Biodiesel Production Research Articles

Evaluation of fuel properties for possible biodiesel output based on the fatty acid composition of oleaginous plants and microalgae

In the past decade, there has been a significant rise in sustainable biomass based biofuel production to address energy needs while mitigating environmental impacts. Traditionally, bioethanol was used for biofuel production, but concerns over food security and environmental preservation have led to growing interest in alternative sources such as neutral lipids from vegetable oil and microalgae for biodiesel production. This research paper evaluates the potential of various oleaginous plants and microalgae as feedstocks for biodiesel production, with a focus on their fatty acid composition and its impact on biodiesel properties. The study examines the fatty acid profiles of 43 different plant and microalgae species and employs various equations to estimate key physical properties of biodiesel. Additionally, the communication compares these properties to International Biodiesel Standards (EN 14214 and ASTM D6751–08) to assess the suitability of the derived biodiesel for commercial use. It is impossible to describe a single composition that is optimal in terms of all essential fuel properties due to the opposing effects of some structural features of the Fatty Acid Methyl Esters (FAME). However, biodiesel should contain relatively low concentrations of both long chain saturated and polyunsaturated FAME to ensure adequate efficiency in terms of low temperature operability and oxidative stability. The results reveal significant variations in properties amongst different feedstocks, highlighting the importance of feedstock selection in biodiesel production. The study also establishes correlations between various fuel properties, providing valuable insights in to optimizing biodiesel production processes, which will be of great use to researchers, engineers, and stakeholders involved in biodiesel production.

Bio-Nanoparticles Mediated Transesterification of Algal Biomass for Biodiesel Production

Immense use of fossil fuels leads to various environmental issues, including greenhouse gas emissions, reduced oil reserves, increased energy costs, global climate changes, etc. These challenges can be tackled by using alternative renewable fuels such as biodiesel. Many studies reported that biodiesel production from microalgae biomass is an environment-friendly and energy-efficient approach, with significantly improved fuel quality in terms of density, calorific value and viscosity. Biodiesel is produced using the transesterification process and the most sustainable method is utilizing enzymes for transesterification. Lipase is an enzyme with excellent catalytic activity, specificity, enantio-selectivity, compatibility and stability and hence it is applied in microalgae biodiesel production. But, difficulty in enzymatic recovery, high enzyme cost and minimal reaction rate are some of its drawbacks that have to be addressed. In this aspect, the nanotechnological approach of lipase immobilization in producing microalgae biodiesel is a promising way to increase production yield and it is due to the adsorption efficiency, economic benefit, recyclability, crystallinity, durability, stability, environmental friendliness and catalytic performance of the bio-nanoparticles used. Through increasing post-harvest biomass yield, absorption of CO2 and photosynthesis in the photobioreactor, the use of nanoparticle immobilized lipase during the generation of biodiesel from microalgae has the potential to also remove feedstock availability constraints. This review article discusses the production of microalgae biodiesel, and effect of nanoparticles and immobilized lipase nanoparticles on biodiesel production. The advantages of using lipase nanoparticles and the challenges in introducing the immobilized lipase on nanoparticles in large-scale microalgae biodiesel production are also discussed. Reducing the water and land use, energy and nutrient footprints of integrated algae-based operations must be the main goal of larger-scale experiments as well as ongoing research and development in order to expedite the adoption of microalgae-based biodiesel production. Also, the cost-effectiveness and large-scale availability of nanoparticles and the impact of lipase nanoparticles on engine performance should be analyzed for commercialization of microalgae biodiesel.

Responses of microalgae under different physiological phases to struvite as a buffering nutrient source for biomass and lipid production

Microalgae cultivation for biodiesel production is promising, but the high demand for nutrients, such as nitrogen and phosphorus, remains a limiting factor. This study investigated effects of struvite, a low-cost nutrient source, on microalgae production under different physiological phases. Changes in element concentrations were determined to characterize the controllable nutrient release properties of struvite. Results showed that nutrient elements could be effectively supplemented by struvite. However, responses of microalgae under different growth stages to struvite varied obviously, achieving the highest biomass (0.53 g/L) and the lowest (0.32 g/L). Moreover, the microalgal lipid production was obviously increased by adding struvite during the growth phase, providing the first evidence that struvite could serve as an alternative buffering nutrient source to culture microalgae. The integration of microalgae cultivation with struvite as a buffering nutrient source provides a novel strategy for high ammonia nitrogen wastewater treatment with microalgae for biodiesel production.

The dilemma and potential development of biodiesel in China - In view of production capacity and policy

China has issued a series of biodiesel-related policies to alleviate energy shortage anxiety and reduce carbon emissions. However, no other provinces or cities in China widely utilize biodiesel except Shanghai. This article firstly conducted a comprehensive estimation of the potential botanical biodiesel capacity in China. Then, we examined why biodiesel advancement in China was stagnated by comparing biodiesel-related policies in pioneer countries such as Malaysia and Indonesia. We found the highest mix ratio will be ∼13 % if all potential botanical oils are added to petrochemical diesel and an addition of 3 % blending ratio can be achieved if waste cooking oils are effectively utilized. We concluded that despite the encouragement from policies, insufficient materials and lack of downstream consumptions may be the major reasons for the sluggish development of biodiesel in China. If microalgae biodiesel production technology is overcome in the future, China can compulsorily mix biodiesel on a large scale. This paper provided a comprehensive review of biodiesel-related policies in Malaysia, Indonesia and China, and figured out the key problems that hinder the promotion of biodiesel, helping to understand the dilemma and drive the potential development of biodiesel in China.

Evaluation of the relationship of wastewater treatment and biodiesel production by microalgae cultivated in the photobioreactor

Microalgae has a great preponderance of fast growth rate and high oil contents. Mixed wastewater and industrial waste gas are utilized in this study as the microalgae's growing medium and resource of inorganic carbon. A combined study of waste usage and biomass energy development is conducted based on closed photobioreactor cultivation. With a focus on the cost of microalgal biodiesel, the financial benefits of waste treatment, the CO2 absorption effect, and biodiesel yield, an assessment of the production process is conducted for different algae species under different energy supply situations. The experimental results indicate that Model algal species 3 (M3) are better adapted for the production of biodiesel with the situation of wind power. It has the algae generates 6800 L of algal liquid, 32.3 kg of microalgae, 42.27 kg of CO2 emission reduction, and 12.47 kg of biodiesel in the single production cycle. The production of microalgae biodiesel based on photobioreactors can produce negative carbon emissions in the setting of a wind energy supply, and the total yearly biodiesel production in the same proliferation scale is at least 112.89 times that of open culture ponds. It has realized the sufficient coupling between waste utilization and biomass energy development through the development of microalgae biodiesel based on photobioreactor culture. It reduces the cost of biodiesel development and maintains high economic efficiency of waste disposal while producing negative carbon emissions. New theoretical guidance is provided by the target's advancement of renewable energy, carbon sequestration, and emission reduction, which has substantial effects on reducing pollution and enhancing significant ecological and environmental effects.

Thallium-mediated NO signaling induced lipid accumulation in microalgae and its role in heavy metal bioremediation

Thallium (Tl+) is a trace metal with extreme toxicity and is highly soluble in water, posing a great risk to ecological and human safety. This work aimed to investigate the role played by Tl+ in regulating lipid accumulation in microalgae and the removal efficiency of Tl+. The effect of Tl+ on the cell growth, lipid production and Tl+ removal efficiency of Parachlorella kessleri R-3 was studied. Low concentrations of Tl+ had no significant effect on the biomass of microalgae. When the Tl+ concentration exceeded 5 μg L−1, the biomass of microalgae showed significant decrease. The highest lipid content of 63.65% and lipid productivity of 334.55 mg L−1 d−1 were obtained in microalgae treated with 10 and 5 μg L−1 Tl+, respectively. Microalgae can efficiently remove Tl+ and the Tl+ removal efficiency can reach 100% at Tl+ concentrations of 0–25 μg L−1. The maximum nitric oxide (NO) level of 470.48 fluorescence intensity (1 × 106 cells)−1 and glutathione (GSH) content of 343.51 nmol g−1 (fresh alga) were obtained under 5 μg L−1 Tl+ stress conditions. Furthermore, the exogenous donor sodium nitroprusside (SNP) supplemented with NO was induced in microalgae to obtain a high lipid content (59.99%), lipid productivity (397.99 mg L−1 d−1) and GSH content (430.22 nmol g−1 (fresh alga)). The corresponding analysis results indicated that NO could participate in the signal transduction pathway through modulation of reactive oxygen species (ROS) signaling to activate the antioxidant system by increasing the GSH content to eliminate oxidative damage induced by Tl+ stress. In addition, NO regulation of ROS signaling may enhance transcription factors associated with lipid synthesis, which stimulates the expression of genes related to lipid synthesis, leading to increased lipid biosynthesis in microalgae. Moreover, it was found that the change in Tl+ had little effect on the fatty acid components and biodiesel properties. This study showed that Tl+ stress can promote lipid accumulation in microalgae for biodiesel production and simultaneously effectively remove Tl+, which provided evidence that NO was involved in signal transduction and antioxidant defense, and improved the understanding of the interrelation between NO and ROS to regulate lipid accumulation in microalgae.

Life cycle assessment of microalgae-derived biodiesel

PurposeMicroalgae-derived biofuels are considered a low-carbon alternative to fossil fuels. Nevertheless, as with all biofuels, there is still uncertainty around their sustainability. Most life cycle assessments (LCA) of microalgae biofuels so far used lab-based, scaled-up lab experimental data or data from the scientific literature. This article, provides evidence and analysis, undertaking an LCA using real-world data from an industrial facility that uses a combination of photobioreactor and fermenter systems.MethodsThe current well-to-wheel LCA study aimed to compare the environmental impacts of microalgae biodiesel production—under different energy regimes—and with petroleum-derived diesel. The functional unit was considered as “combustion of 1 MJ (Lower Heating Value) of algal biodiesel in an internal combustion engine (as B100)”. This LCA study considers the environmental and energy impacts from the construction of the facility, as well as those impacts from the operation of the facility. The foreground LCI data was collected from a real-world one-hectare microalgae production pilot facility. ReCiPe, IPCC AR5 (GWP100 and GWP20) and Global Temperature Potential (GTP) were implemented to assess the life cycle environmental impacts.Results and discussionThe assessment shows that when infrastructure is included, microalgae-derived biofuels are not yet favourable over petroleum-derived fuels on GWP100, and this becomes worse over shorter timescales. In terms of climate change (GWP100), whilst 1 MJ (LHV) of fossil-derived diesel would emit 8.84 × 10−2 kg CO2eq, 1 MJ of microalgae-derived biodiesel from a solar photovoltaic powered facility would emit 1.48 × 10−1 kg CO2eq. To be equal to petroleum-derived diesel in terms of GWP100, or perform better, productivity of the microalgae production system needs to be improved as the most effective solution. The results also showed that electricity and infrastructure were major sources of environmental impacts, as well as the yeast used within the fermenter. Moreover, it takes 0.99 MJ of direct energy per 1 MJ of microalgae biofuel produced, similar to the fossil fuel industry for 1 MJ of diesel.ConclusionsUsing infrastructure and operational models, the study shows that the facility does not compare well with petroleum-derived diesel unless productivity can be increased. Productivity improvements, be it through improvements to microalgae strains or improved photobioreactor designs, should be a priority to ensure microalgae become a sustainable fuel feedstock. Electricity use should be reduced as well, again, through improved cultivation system designs. In terms of the current system, the high impacts of yeast should be addressed, either through co-locating yeast production or through ensuring specific sources with lower impacts. Extracting lipids will effectively waste some high-value products, whilst the waste can be expected to be a mixture of unextracted lipids, polysaccharides or fibre, some proteins and minerals. It is also shown that harmonisations of the assessments are needed for future studies and real-world operation facilities to conclusively decide if microalgae should be used as fuel or if they would be better used for other products, such as feed or high-value products.

Optimization of cavitation-assisted biodiesel production and fuel properties from Neochloris oleoabundans microalgae oil using genetic algorithm and response surface methodology

Biodiesel is a promising alternative fuel for diesel engines that provides energy security and significant environmental benefits. But its commercialization is restricted due to the cost and quality as compared to diesel fuel. To address the above, Neochloris oleoabundans microalgae oil, a non-edible, cost-effective, and underutilized third-generation feedstock, is used to produce superior biodiesel by the transesterification reaction using a hydrodynamic cavitation (HC) approach. In this research work, the transesterification model for microalgae biodiesel production is optimized through genetic algorithm (GA) and response surface methodology (RSM) using MATLAB R2020a and Design Expert 8.0.7.1, respectively. Four process input variables (operating pressure (0.5–2.5 bar), catalyst concentration (0.5–1.5 wt.%), reaction time (5–25 minutes), and molar ratio (3:1 to 7:1)) and a five-level L30 array were developed to construct a statistical model. Biodiesel yield and major properties like density, kinematic viscosity, calorific value, and flash point are the model responses. The optimum conditions for microalgae biodiesel production were operating pressure of 2.43 bar, KOH catalyst concentrations of 1.22 wt. %, reaction time of 15.54 minutes, molar ratio of 5.61:1 and at 60°C fixed reaction temperature. The optimum value of response, such as biodiesel yield, was 99.80%, the density was 0.882 g/cc, the kinematic viscosity was 4.06 cst, the calorific value was 41.72 MJ/kg, and the flash point was 146.64 °C. RSM and GA predicted results were validated experimentally. The reaction time for biodiesel produced by HC in the same settings as the conventional method was reduced by 85%. Due to its faster processing time, the HC approach is preferred to the conventional method.

Modeling of microalgal biodiesel production integrated to a sugarcane ethanol plant: Energy and exergy efficiencies and environmental impacts due to trade-offs in the usage of bagasse in the Brazilian context

The Brazilian sugarcane mills already provide significant amounts of renewable products (ethanol and bioelectricity) through self-sufficient bagasse cogeneration. Gaseous outputs of the sector can provide streams rich in biogenic carbon dioxide (CO2), suitable for the autotrophic cultivation of microalgae and aim, hereinafter, their conversion into biodiesel. This work modeled the integration of an ethanol plant with a cogeneration system, covering the enzymatic hydrolysis of bagasse and the production of microalgae biodiesel. A standard ethanol plant yielding 96 L ethanol/t cane may produce an additional 7.5–30 L microalgae biodiesel/t cane but at the expense of its energy self-sufficiency; the biorefinery must recur to fossil resources unless other biomass (besides bagasse) and coproducts by the plant's neighborhood can be exploited. The process simulation is conducted in nine cases derived from a central composite design with two factors – the fraction of bagasse destined for the hydrolysis system (x1) and the fraction of ethanol sent to produce anhydrous ethanol (x2) – and three levels for each factor (0, 50, 100%). Energy ratios between representative outputs and inputs – Net energy ratio (NER) and Fossil energy ratio (FER) –, direct CO2 emission, and exergy efficiencies were calculated as representative responses to evaluate the plant's technical and environmental efficiencies. Statistical tools (t-Student test, ANOVA, and R2) showed that the constructed models were robust and that the responses varied significantly with x1, while x2 produced mild or negligible effects. The highest achievable NER and FER were 0.83 and 2.09, respectively. The whole system resulted in a FER equal to 1 when bagasse usage is split in half between the hydrolysis and cogeneration systems. This result guarantees that the energy related to the useful products is higher than the requirements of fossil energy inputs, within an acceptable range. The optimum CO2 emission and exergy efficiency were found when 6–8% of the bagasse is hydrolyzed, which is also a range covering attractive energy ratios. The proposed integration benefits the sector, but resorting to renewable sources to supply energy deficits, developing the technological exploitation over wasted coproducts, and studying heat and mass integration of processes are highly recommended to enhance the global-system performance.

Photothermal technique-enabled ambient production of microalgae biodiesel: Mechanism and life cycle assessment

Thermocatalytic (trans)esterification of oils/lipids to produce biodiesel is generally energy-consuming, reversible, and controlled by the equilibrium law. Herein, a light-induced photothermal process was illustrated to be highly efficient for biodiesel production (96.8 % yield) from microalgae lipids at room temperature enabled by a biomass-based SO3H-functionalized graphene-like heterogeneous catalyst (S-NGL-600), as optimized by response surface methodology. Infrared thermal imaging indicated that interfacial solar heating led to forming a local photothermal catalytic system, reaching 72.2 °C in 2 min. The local light heating was conducive to evaporation and removal of water from acid sites, resulting in local excess of microalgae lipids to facilitate the forward reaction. Notably, the photothermal catalyst was highly recyclable and exhibited a significantly higher conversion rate of microalgae lipids than industrially used catalyst H2SO4. Life cycle assessment suggested energy-saving advantage (0.87 MJ/MJ) and environmental protection (-89.42 CO2eq/MJ) of the photothermal-driven protocol for microalgae biodiesel production.

Flexibility concept in design of advanced multi-energy carrier systems driven by biogas fuel for sustainable development

In this paper, a new and comprehensive multigeneration system is developed exploiting biogas fuel. The system is examined from the perspective of energy, exergy, exergoeconomic, exergoenvironment, and safety for supplying the energy demands of large buildings such as modern hospitals located near industrial places. Multi-objective optimization is applied along with a new concept of flexibility in the system considering these five indicators. The Brayton cycle and closed Brayton cycle for power generation, dual-loop organic Rankine cycle and ejector refrigeration for power and cooling production, multi-effect distillation unit for freshwater production, carbon dioxide absorption unit by microalgae for biodiesel production, water heaters for domestic heating production, and PEM electrolyzer for hydrogen production are integrated into the devised system. From the environmental point of view, using biogas fuel and absorption of carbon dioxide leads to the best environmental efficiency in the proposed system. Moreover, the safety facet is analyzed to lower the level of damage and risk in the system. Based on the results of the optimization, the net output power, air conditioning refrigeration, freezing, and heating are reckoned at 1864, 286.6, 75.89, and 398.9 kW, and the production of freshwater, hydrogen, biodiesel, and glycerol is predicted to be 2.111, 0.00038, 0.0088, and 0.00091 kg/s, respectively. Also, the system performance ratio, unit cost of product, exergy efficiency, environmental effect of product, and overall system risk are equal to 1.828, 40.58 $/GJ, 31.11%, 6232 mPts/GJ, and 1656 $/year.

A review on biodiesel production from microalgae: Influencing parameters and recent advanced technologies.

Microalgae are the important part of carbon cycle in the nature, and they could utilize the carbon resource in water and soil efficiently. The abilities of microalgae to mitigate CO2 emission and produce oil with a high productivity have been proven. Hence, this third-generation biodiesel should be popularized. This review firstly introduce the basic characteristics and application fields of microalgae. Then, the influencing parameters and recent advanced technologies for the microalgae biodiesel production have been discussed. In influencing parameters for biodiesel production section, the factors of microalgae cultivation, lipid accumulation, microalgae harvesting, and lipid extraction have been summarized. In recent advanced technologies for biodiesel production section, the microalgae cultivation systems, lipid induction technologies, microalgae harvesting technologies, and lipid extraction technologies have been reviewed. This review aims to provide useful information to help future development of efficient and commercially viable technology for microalgae-based biodiesel production.

The effect of salinity stress on the growth and lipid accumulation of Scenedesmus quadricauda FACHB-1297 under xylose mixotrophic cultivation

In the commercial production of microalgae biodiesel, high culture cost and low lipid production yields are two major limitations. Finding cheap carbon sources and ways to promote lipid accumulation can achieve low-cost cultivation and efficient lipid production. The impact of NaCl on the growth and lipid accumulation in Scenedesmus quadricauda FACHB-1297 under xylose mixotrophic cultivation was explored in this study. The results showed that when NaCl concentration were 0.88–5.85 g/L, the biomass concentration and lipid content were 2.15–2.68 and 1.19–1.80 times higher than those in BG11 medium, respectively. Under the optimal NaCl concentration of 2.63 g/L, the highest lipid content (39.33%) was achieved, with the biomass concentration of 0.72 g/L, the total nitrogen removal efficiency of 39.00%, and the total phosphorus removal efficiency of nearly 100.00%, except for a higher total sugar content of 19.26% and total protein content of 5.38%. In short, these results indicated that 2.63 g/L NaCl treatment was an efficient way to promote the lipid accumulation of S. quadricauda FACHB-1297 using xylose in papermaking waste liquid to produce biofuel.

A comprehensive review on microalgal biomass production and processing for biodiesel production

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.

Investigating a novel role of LARP along the algal TOR pathway

Over the last few decades, global warming has become an increasingly desperate rallying cry for the need to find and optimize efficient renewable energy sources.1 Microalgae are considered apromising source of energy because they contain a high concentration of lipids, but due to inefficiencies in their lipid production, microalgae cannot produce enough biofuel to replace current fuel needs.2Chlamydomonas reinhardtiiis a unicellular green alga that is a great candidate for manipulation and an excellent model organism used to better understand algal metabolic pathways and improve biofuels. Our previous research has shown that inhibiting the target of rapamycin (TOR) kinase of C. reinhardtii with AZD8055 causes the growth of the cell cultures to stagnate, the photosynthetic efficiency to decrease, as well as a direct link between oxidative signaling and the upregulation of TAGs.3 Additionally, our work has indicated that La‐related protein 1 (LARP1) is a TOR target and involved in propagating the intracellular response following inhibition. In mammalian systems, LARP1 interacts directly with mTOR and regulates protein synthesis by binding and stabilizing mRNA before recruiting polysomes to initiate translation. LARP1 is essential in mammalian systems, and deficiencies lead to inhibited growth, defects, and increased apoptosis. However, LARP1 deficiency in C. reinhardtii does not cause the same phenotype, indicating a distinct uncharacterized role in phototrophic organisms.This study seeks to understand this role by using a LARP1 knockout mutant to compare the physiological changes following inhibition with the parent strain. Both strains were assessed for biochemical composition, cell size, and photosynthetic electron fluxes. Together, these data support LARP1 as a regulator of protein degradation along the TOR pathway. The differential delineation of metabolic processes in LARP1 knockouts provides a framework for further TOR pathway characterization in phototrophic eukaryotes.Literature References1 IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.2 Sharma, Kalpesh K., Holger Schuhmann, and Peer M. Schenk.. High Lipid Induction in Microalgae for Biodiesel Production. 2012. Energies. 5:1532‐1553.3 Ford, M. M., Smythers, A. L., McConnell, E. W., Lowery, S. C., Kolling, D. R. J., & Hicks, L. M. (2019). Inhibition of TOR in Chlamydomonas reinhardtii leads to rapid cysteine oxidation reflecting sustained physiological changes. Cells, 8(10), 1171.

Carbon-induced effective lipid accumulation and self-flocculation for biofuel production of Tetradesmus obliquus FACHB-12

Utilizing rich organic matter in wastewater for microalgae cultivation is an attractive strategy to solve the high-cost issue in microalgae biodiesel production. In this study, common carbon sources in wastewater were used as nutrients to explore their effects on biomass accumulation and lipid production of Tetradesmus obliquus FACHB-12. The highest carbon fixation (1.2 g C·L−1) and biomass accumulation (1.99 g L−1) was achieved using glucose as the only carbon source for the microalgae cultivation in the designed system. In comparison, the high flocculation efficiency (89.63%) with the addition of glycerol achieved the recovery of lipids and starch at 0.36 g L−1 and 0.023 g L−1, respectively. In addition, results revealed that microalgae cells cultured with glycerol had the highest extracellular polymers fluorescence intensity of 2.84*104 R.U.·g−1. This study provides insights of common carbon sources in wastewater for culturing microalgae, which leads to the potential reduction in microalgae cultivation cost and primary dewatering cost in practice.

Reduction of the environmental impacts of the hydropower plant by microalgae cultivation and biodiesel production

Hydropower plants supply their energy needs for electricity generation from rivers or water canals, so these power plants cannot be used for sustainable electricity generation, and the best time to use these power plants is during peak power consumption. These power plants are less polluting in terms of environment than other power plants, but they also have negative environmental effects, such as freshwater eutrophication and water salinity or microalgae. This study focused its attention on microalgae extraction as an environmentally friendly method to reduce water salinity and how they can be used for biodiesel production as an auxiliary fuel to enhance the energy production by hydropower plants. The information of the sample hydroelectric power plant (Gotvand Dam) that was required for the processing and simulation process is stated. The step-by-step simulation is reviewed and the results and optimizations are described. The highest separation of microalgae for 1 min electrolysis with distance of 1 cm between the two electrodes is 90%, which reduces the salt content of the water in which the microalgae is grown by 13%. The maximum separation of salt from water is 19.5%, which is reduced to 9.5% in the centrifuge method. Water salinity reduction to microalgae extraction ratio is 14.45%. The optimal combination of diesel and biodiesel is 80%–20%. As can be seen from the results it is recommended to use microalgae for reducing negative environmental impacts in addition to increasing the power generation capacities of hydropower plants. Also more specific studies on terms of the culture of the microalgae and its individual cultivation methods for hydropower plants beneficial programs should be taken into account and be used by policy makers in the future.

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.

Comparison of heterotrophic and mixotrophic Chlorella pyrenoidosa cultivation for the growth and lipid accumulation through acetic acid as a carbon source

In order to overcome the bottleneck of the high cost of microalgae biodiesel production, biomass and lipid accumulation of microalga Chlorella pyrenoidosa feeding on the low-cost carbon source, acetic acid (AcA), were investigated. The results showed that C. pyrenoidosa had the ability of mixotrophy and heterotrophy, which could tolerate 50 g/L of AcA in the heterotrophy with the biomass concentration of 137.89 ± 2.03 mg/L. Under heterotrophic condition, the biomass productivity at logarithmic stage was positively correlated with the AcA dosage, and the maximum biomass productivity of 187.26 ± 3.61 mg/L/d was obtained at 10 g/L of AcA. Four AcA concentrations (6, 10, 20 and 30 g/L) were set to evaluate the effects of AcA on the growth and lipid accumulation of C. pyrenoidosa under heterotrophic and mixotrophic conditions. Heterotrophic mode at 10 g/L of AcA was demonstrated to be the most potential condition with the maximum biomass productivity of 134.91 ± 5.74 mg/L/d and the highest lipid productivity of 42.04 ± 0.21 mg/L/d, and the lipid production (44.03 ± 2.84 mg/L) was 15-fold higher than the control of BG-11 medium. In addition, C. pyrenoidosa achieved the highest nutrient removal efficiency (30.0% and 85.9% for total nitrogen and phosphorus, respectively) and the highest AcA assimilation efficiency (74.1%). This study highlighted a promising win-win method of AcA recycling and microalgae-based biodiesel production.

Isolation of a high-ammonium-tolerant Monoraphidium sp. and evaluation of its potential for biodiesel production

The economic challenges of microalgae biodiesel production, including the energy burden and water shortage, can be addressed simultaneously by using wastewater as a nitrogen source. However, as a major form of nitrogen, ammonium is toxic to most microalgae strains, which limits the use of ammonium-containing wastewater. High-ammonium-tolerant algal strains remain to be explored. In this study, a microalgal strain named HDMA-01, which was isolated from Lake Dongfeng in China, was selected using a high ammonium medium. Phylogenetic analysis suggested that HDMA-01 belongs to the genus Monoraphidium (Selenastraceae, Sphaeropleales), and both 18S ribosomal DNA and ITS sequences of HDMA-01 appeared to be new molecular records of the Monoraphidium species. HDMA-01 can multiply vigorously using acetic acid and ammonium in TAP medium, reaching a density of 2 ×107 mL−1 within 7 days. HDMA-01 showed strong tolerance for ammonium. At a high ammonium concentration of 14 mM, HDMA-01 achieved maximum biomass and lipid productivity of 78.9 mg L−1 day−1 and 13.8 mg L−1 day−1, which is the highest among other Monoraphidium strains under similar cultivation conditions. Together with its ideal fatty acid profile, HDMA-01 has great potential for development as a promising strain used in biodiesel feedstock and high-ammonium tolerance biotechnology.