Microalgae For Biofuel Production Research Articles

Suitable site analysis for microalgae biofuel production as a source of renewable energy

The global demand for renewable energy sources has been increasing. Microalgae is considered one of the best energy sources among renewable options, as it efficiently produces biofuel on a large scale. Pakistan has advantageous conditions for cultivating microalgae as a biofuel source, including abundant sunlight, favorable climate conditions, ample land and water resources. This research aims to identify suitable sites in Karachi for microalgae cultivation using geographic information systems. The potential sites were classified into four categories: highly suitable, moderately suitable, less suitable, and unfavorable. The study shows that Karachi provides an environment conducive to large-scale microalgae cultivation, which could help to alleviate energy shortages. Moreover, identifying viable cultivation locations can attract domestic and international interest, leading to future developments in the field.

Comprehensive assessment of microalgal-based treatment processes for dairy wastewater.

The dairy industry is becoming one of the biggest sectors within the global food industry, and these industries use almost 34% of the water. The amount of water used is governed by the production process and the technologies employed in the plants. Consequently, the dairy industries generate almost 0.2-10L of wastewater per liter of processed milk, which must be treated before being discharged into water bodies. The cultivation of microalgae in a mixotrophic regime using dairy wastewater enhances biomass growth, productivity, and the accumulation of value-added product. The generated biomass can be converted into biofuels, thus limiting the dependence on petroleum-based crude oil. To fulfill the algal biorefinery model, it is important to utilize every waste stream in a cascade loop. Additionally, the harvested water generated from algal biomass production can be recycled for further microalgal growth. Economic and sustainable wastewater management, along with proper reclamation of nutrients from dairy wastewater, is a promising approach to mitigate the problem of water scarcity. A bibliometric study revealing limited work on dairy wastewater treatment using microalgae for biofuel production. And, limited work is reported on the pretreatment of dairy wastewater via physicochemical methods before microalgal-based treatment. There are still significant gaps remains in large-scale cultivation processes. It is also crucial to discover robust strains that are highly compatible with the specific concentration of contaminants, as this will lead to increased yields and productivity for the targeted bio-product. Finally, research on reutilization of culture media in photobioreactor is necessary to augument the productivity of the entire process. Therefore, the incorporation of the microalgal biorefinery with the wastewater treatment concept has great potential for promoting ecological sustainability.

Microalgae biofuels: illuminating the path to a sustainable future amidst challenges and opportunities.

The development of microalgal biofuels is of significant importance in advancing the energy transition, alleviating food pressure, preserving the natural environment, and addressing climate change. Numerous countries and regions across the globe have conducted extensive research and strategic planning on microalgal bioenergy, investing significant funds and manpower into this field. However, the microalgae biofuel industry has faced a downturn due to the constraints of high costs. In the past decade, with the development of new strains, technologies, and equipment, the feasibility of large-scale production of microalgae biofuel should be re-evaluated. Here, we have gathered research results from the past decade regarding microalgae biofuel production, providing insights into the opportunities and challenges faced by this industry from the perspectives of microalgae selection, modification, and cultivation. In this review, we suggest that highly adaptable microalgae are the preferred choice for large-scale biofuel production, especially strains that can utilize high concentrations of inorganic carbon sources and possess stress resistance. The use of omics technologies and genetic editing has greatly enhanced lipid accumulation in microalgae. However, the associated risks have constrained the feasibility of large-scale outdoor cultivation. Therefore, the relatively controllable cultivation method of photobioreactors (PBRs) has made it the mainstream approach for microalgae biofuel production. Moreover, adjusting the performance and parameters of PBRs can also enhance lipid accumulation in microalgae. In the future, given the relentless escalation in demand for sustainable energy sources, microalgae biofuels should be deemed a pivotal constituent of national energy planning, particularly in the case of China. The advancement of synthetic biology helps reduce the risks associated with genetically modified (GM) microalgae and enhances the economic viability of their biofuel production.

Increasing lipid production in Chlamydomonas reinhardtii through genetic introduction for the overexpression of glyceraldehyde-3-phosphate dehydrogenase.

Microalgae, valued for their sustainability and CO2 fixation capabilities, are emerging as promising sources of biofuels and high-value compounds. This study aimed to boost lipid production in C. reinhardtii by overexpressing chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key enzyme in the Calvin cycle and glycolysis, under the control of a nitrogen-inducible NIT1 promoter, to positively impact overall carbon metabolism. The standout transformant, PNG#7, exhibited significantly increased lipid production under nitrogen starvation, with biomass rising by 44% and 76% on days 4 and 16, respectively. Fatty acid methyl ester (FAME) content in PNG#7 surged by 2.4-fold and 2.1-fold, notably surpassing the wild type (WT) in lipid productivity by 3.4 and 3.7 times on days 4 and 16, respectively. Transcriptome analysis revealed a tenfold increase in transgenic GAPDH expression and significant upregulation of genes involved in fatty acid and triacylglycerol synthesis, especially the gene encoding acyl-carrier protein gene (ACP, Cre13. g577100. t1.2). In contrast, genes related to cellulose synthesis were downregulated. Single Nucleotide Polymorphism (SNP)/Indel analysis indicated substantial DNA modifications, which likely contributed to the observed extensive transcriptomic and phenotypic changes. These findings suggest that overexpressing chloroplast GAPDH, coupled with genetic modifications, effectively enhances lipid synthesis in C. reinhardtii. This study not only underscores the potential of chloroplast GAPDH overexpression in microalgal lipid synthesis but also highlights the expansive potential of metabolic engineering in microalgae for biofuel production.

Simultaneous production of bio-crude bio-oil via hydrothermal liquefaction and carotenoids via supercritical extraction from Nannochloropsis oceanica and recycling effluent to establish circular processes

Commercial production of microalgae biofuel is not economically feasible since it cannot compete with the price of fossil fuels. Algal biofuel could be cost-effective if high-value co-products are produced from microalgal biomass before it is converted into biofuel. Thus, this research aims to demonstrate a circular biorefinery process of producing bio-crude bio-oil as well as high-value products like carotenoids from a marine microalga Nannochloropsis oceanica. The microalga was cultivated in raceway ponds over the years with the highest biomass productivity of 30–40 g m−2 day−1 recorded in October and November of 2021, but it reduced in extremely high summer temperatures and low temperatures in winter of Delhi NCR, India. The annual average biomass productivity of 19.13 g m−2 day−1 was recorded, which is equivalent to 69825 kg ha−1 year−1. The algal biomass was processed for high-value carotenoids using a green process, i.e. supercritical carbon dioxide extraction. Carotenoid yield of 252 μg/g of biomass was obtained after optimizing temperature and pressure in the supercritical extraction process. The spent biomass after carotenoid extraction was used to produce bio-crude bio-oil using hydrothermal liquefaction. There was no significant difference between bio-crude oil yield and properties after carotenoid extraction and direct biomass use. A bioeconomic methodology for closing the circular loop involving recycling the effluent generated during hydrothermal liquefaction to re-cultivate the microalgae is demonstrated. This study highlights the potential of green technology, circular bioeconomy, and biorefinery practices in developing sustainable and environmentally friendly solutions for the chemical and energy sectors.

High efficiency lipid production, biochar yield and chlorophyll a content of Chlorella sp. microalgae exposed on sea water and TiO2 nanoparticles

This study explores the challenges facing microalgae biofuel production, specifically low lipid content and difficulties with algal cell harvesting. The purpose of the research is to investigate the effect of seawater content and nanoparticle concentration on freshwater microalgae growth and biofuel production. The principal results of the study show that increasing the proportion of seawater and nanoparticles enhances the lipid content and cell diameter of microalgae, while excessive concentrations of nanoparticles and low seawater content lead to reduced microalgae growth. Furthermore, an optimal cell diameter was identified at a nanoparticle concentration of 150 mg/L. The study also reveals that increasing seawater content can decrease zeta potential and increase chlorophyll a content due to the concentration of dissolved organic matter. Increasing the seawater content from 0% to 25% decreased zeta potential by 1% owing to the instability and aggregation of the cells. Chlorophyll a for the 0% seawater was 0.55 which is increased to 1.32 only due to the increase in the seawater content. This significant increase is due to the concentration of dissolved organic matter in seawater. Additionally, the presence of seawater positively affects microalgae metabolic activity and biochar yield. The findings of this study offer valuable insights into the potential for optimizing microalgae biofuel production. The use of seawater and nanoparticles has shown promise in enhancing microalgae growth and biofuel yield, and the results of this study underscore the scientific value of exploring the role of seawater and nanoparticles in microalgae biofuel production. Further research in this area has the potential to significantly contribute to the development of sustainable energy solutions.

Sustainability evaluation of green microalgae biofuel production and reducing the engine emissions in a common rail direct engine

The goal of this study is to find a way to run a diesel engine entirely on spirulina microalgae (SMA) and base fuel (BF) in a dual fuel mode. This study looks at the effects of keeping the injection settings and compression ratio fixed on the performance and burning of a diesel engine that has been changed to run on SMA-BF. The test is done with three different engine loads of low, medium, high and two different mixes of SMA20BF80 and SMA40BF60 at 18.5 compression ratio (CR) and 1500 rpm. The Diesel-RK model has looked at how well the engine works, how much fuel it uses, how long it takes to start, how much smoke it makes, and how much nitrogen oxides (NOx) it makes. The results show that the fuel sample (SMA20BF80) makes the engine work 0.35% less efficiently and uses 6.5% more fuel than the BF. At its peak, the SMA20BF80 blend has a heat release rate of 73.7 J/°CA and a cylinder pressure of 92.5 bar. Also, compared to BF, the SMA20BF80 mixture gives off less NOx and smoke at high load by 11.2% and 5%, respectively. But the SMA20BF80 mixture releases almost 2% more carbon dioxide than the BF mixture. NOx emissions go up as the load goes up.

Bioprocessing of Waste for Renewable Chemicals and Fuels to Promote Bioeconomy

The world’s rising energy needs, and the depletion of fossil resources demand a shift from fossil-based feedstocks to organic waste to develop a competitive, resource-efficient, and low-carbon sustainable economy in the long run. It is well known that the production of fuels and chemicals via chemical routes is advantageous because it is a well-established technology with low production costs. However, the use of toxic/environmentally harmful and expensive catalysts generates toxic intermediates, making the process unsustainable. Alternatively, utilization of renewable resources for bioprocessing with a multi-product approach that aligns novel integration improves resource utilization and contributes to the “green economy”. The present review discusses organic waste bioprocessing through the anaerobic fermentation (AF) process to produce biohydrogen (H2), biomethane (CH4), volatile fatty acids (VFAs) and medium chain fatty acids (MCFA). Furthermore, the roles of photosynthetic bacteria and microalgae for biofuel production are discussed. In addition, a roadmap to create a fermentative biorefinery approach in the framework of an AF-integrated bioprocessing format is deliberated, along with limitations and future scope. This novel bioprocessing approach significantly contributes to promoting the circular bioeconomy by launching complete carbon turnover practices in accordance with sustainable development goals.

Machine learning for algal biofuels: a critical review and perspective for the future

Machine learning applications in microalgae biofuel production are reviewed; the current states and major trends in research as well as the challenges to overcome are identified.

A Review on Microalgae Biofuel Production and use in CI Engine Applications

Alternative fuel technology of third-generation biofuels in place of conventional fossil fuels is currently being witnessed at a global level. Due to its sustainability and environmental friendliness, in recent years more importance is being given to biodiesel in CI engine applications. Recent trends show that microalgae are promoted as a bio-fuel due to their inherent advantages of abundant availability of oil sources and faster growth rate with ease of cultivation. Particular species of algae such as Chlorella, Botryococcus braunii, and Scenedesmus obliquus are conventionally favored for biodiesel production as they have a prominent amount of lipids content. This review outlines the current state of experimental investigations on the use of different algae biodiesel blends with diesel for CI engines. Amongst the different algae-based biodiesel, the dual Calophyllum Inophyllum methyl ester blend (CIME20) with DEE demonstrated the maximum brake thermal efficiency (BTE) and better brake-specific fuel consumption (BSFC) of CI engines. In terms of emissions, the CO, UBHC, and smoke levels are significantly lower for algae blends in contrast to neat diesel.

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.

Effect of sulfur limitation strategies on glucose-based carbohydrate production from Chlorella sorokiniana

Sulfur (S) limitation is an effective strategy for improving carbohydrate accumulation in microalgae for biofuel production. This study illustrates three S-limitation methods in detail, namely, S-free, S-deprivation and S-starvation, while providing an investigation into their effects on the growth, biomass and glucose-based carbohydrate accumulation of Chlorella sorokiniana UTEX1230. The S-free method significantly increased the carbohydrate content in C. sorokiniana biomass up to 60.5%, with a productivity of 0.24 g L−1d−1. The S-starvation method balanced the carbohydrate content and biomass yield, resulting in the highest carbohydrate yield of 0.34 g L−1. Meanwhile, the S-deprivation method had no advantages in terms of carbohydrate yield and productivity, highlighted by the relatively lower carbohydrate content in the biomass. Carbohydrates were hydrolysed to glucose using dilute sulfuric acid, and the efficiency was positively correlated with the combined severity of the treatment. The results suggest the potential of S-limitation methods in the production of glucose from microalgae; however, the associated efficiency is dependent on the specific treatment method used.

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.

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.

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 %.

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.

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.

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.