Life Cycle Assessment of Microalgae-Based Products for Carbon Dioxide Utilization in Thailand: Biofertilizer, Fish Feed, and Biodiesel

2.1 Goal and scope definition

This study aims to determine which of three microalgae-based products has the least environmental impact. The intended application is to draw comparative conclusions about the environmental impacts of various microalgae products produced from carbon dioxide captured using amine-based technology from a nearby power plant. The impact of transportation is not considered due to the proximity of the capture source. The microalgae products examined in this study—biodiesel, fish feed, and biofertilizer—were selected based on their potential commercial viability and relevance to current market demands. Results are aimed at informing potential stakeholders, including policymakers and industry leaders, about the feasibility and environmental implications of microalgae technology as a use for captured carbon dioxide. The technologies employed in this study, such as carbon capture, cultivation, harvesting, and product conversion processes, are limited to the best available options known at this time. The functional unit is one million tons of utilized captured carbon dioxide. This is measured as the amount of carbon injected into the photobioreactor.

However, as these technologies are likely to continue developing in the future, potential improvements are considered in this study, in addition to the current state of the art. Initially, the study uses Thailand’s 2020 energy mix as a baseline scenario. In Thailand’s 2020 energy mix (TH20), fossil fuels dominate, with natural gas providing 57% of electricity, coal 19%, and oil 5.8%. Renewable sources contribute modestly, with biofuels at 9.8%, solar PV 2.7%, and wind 1.6%, while hydro accounts for 3.7% and waste for 0.5% of the total generation. To extend the applicability of the results beyond Thailand and explore potential future energy landscapes, the analysis includes two additional energy scenarios: a balanced mix of 50% renewable energy and 50% grid energy (based on the 2020 mix), and a 100% renewable energy scenario. These scenarios were selected based on specific criteria: representation of current conditions (Thailand’s 2020 mix), exploration of a transitional state (50% renewable + 50% grid), and examination of a fully renewable future (100% renewable). Nine scenarios are created by combining each of the three microalgae products with these three energy scenarios. For clarity and brevity, abbreviations are used throughout the study: BF, BD, and FF represent biofertilizer, biodiesel, and fish feed respectively, while the energy scenarios are abbreviated as follows: 100% for 100% Renewable energy, 50% for 50% Renewable energy + 50% Thailand’s electricity mix in 2020, and TH20 for Thailand’s electricity mix in 2020. This approach allows for a comprehensive assessment of how varying levels of renewable energy integration could impact the environmental performance of different microalgae-based carbon capture and utilization technologies. This study has expanded its scope to include a cradle-to-grave analysis, covering carbon capture, microalgae cultivation, production, and use of the three products ( Figure 1). The emissions source was excluded from the system boundary since this study focuses on evaluating and comparing CO₂-based product production pathways, specifically assessing their suitability for carbon utilization in terms of environmental impact. Substitution was used for the displacement of conventional fossil-based diesel, conventional fish feed, and conventional mineral fertilizer. This allows for comparison based only on the function of utilizing captured carbon and not the individual functions of the three products. The data requirements for this study are the quantitative measures of emissions and resource use.

Figure 1. System boundary diagram for biofuels and bioproducts from microalgae.

2.2. Life cycle inventory

All data inputs were collected from secondary sources, including life cycle inventory databases and published literature (Table S1) (underlying data). Agri-footprint, Industry Data 2.0, and ecoinvent 3 databases served as the sources for background input data. These inputs include tubular photobioreactor construction, cleaning materials, and system inputs such as nitrogen and phosphorus fertilizers. Carbon capture data was obtained from (Rafiq et al., 2024a; Win et al., 2023), while cultivation and harvesting data were sourced from (Bradley et al., 2023; Grierson et al., 2013; Schade and Meier, 2020). Data for subsequent microalgae-based products (biodiesel, fish feed, and biofertilizer) were collected from (Bradley et al., 2023; Fenton et al., 2014; Grierson et al., 2013; Li et al., 2022; Smetana et al., 2017) and then adapted to the functional unit. Data for the substitution of traditional production of fish feed was sourced from literature as well (Pelletier and Tyedmers, 2010; Yacout et al., 2016).

2.2.1 Biodiesel production

Nannochloropsis sp. was selected for this study due to its advantageous characteristics for biodiesel production, particularly its high lipid and protein contents. The nutrient composition of this microalgae species varies significantly across literature, influenced by factors such as nutrient availability and environmental conditions. For this study, a protein content of 30% of dry matter was adopted, aligning with the consensus among several research findings (Molino et al., 2018; Paes et al., 2016). The lipid content of Nannochloropsis sp. exhibits considerable variability, ranging from 5% to 44% of dry matter under optimal growth conditions. Taking into account this variability, an average lipid content of 21% of dry matter was used for this study. Additionally, the eicosapentaenoic acid content, an important omega-3 fatty acid, averages around 4.2% of dry matter (Molino et al., 2018; Schade and Meier, 2020).

In this study, the microalgae are cultivated in borosilicate glass tubular photobioreactors, chosen for their high surface area-to-volume ratio and efficient light utilization [37]. Following cultivation, the biomass undergoes centrifugation for harvesting, followed by lipid extraction ( Figure 2). The extracted lipids are then converted to biodiesel through transesterification, yielding glycerol as a co-product (Fenton et al., 2014; Schade and Meier, 2020). Substitution was employed for multiple products and co-products throughout the process. The primary output, biodiesel, substitutes conventional diesel fuel on an energy-equivalent basis (37.5 MJ/kg for biodiesel compared to 43 MJ/kg for conventional diesel). Glycerol, a co-product generated at approximately 10% of the biodiesel mass, substitutes synthetic glycerol on a mass-equivalent basis (Rodrigues et al., 2017). The residual biomass remaining after lipid extraction was utilized for biomethane production through anaerobic digestion. Methane yield from Nannochloropsis sp. was approximately 0.35 L per gram of volatile solids, with volatile solids comprising 79% of the total solids in the raw biomass (Bohutskyi et al., 2014; Torres et al., 2023). The produced biomethane substitutes natural gas, providing a more sustainable alternative to this fossil fuel. The digestate left after biomethane production, rich in nutrients such as nitrogen, phosphorus, and potassium, was used as a biofertilizer. This nutrient-rich digestate further contributed an energy offset of 186.37 MJ/m³ when substituting conventional fertilizers (Fenton et al., 2014).

Figure 2. Illustration of the complete cradle-to-grave processes for biofuels and bioproducts production.

2.2.2 Fish feed and biofertilizer production

For production of both fish feed and biofertilizer, Chlorella vulgaris was assumed as the algal strain. In the case of biofertilizer, chlorella, spirulina, and other algae species have shown benefits to crop growth including increased root and shoot length (El Arroussi et al., 2018). Chlorella vulgaris has also been shown to increase organic matter in soil (Alvarenga et al., 2023). Chlorella vulgaris was selected as it was the strain used to support evidence that microalgae could replace traditional mineral fertilizer (Schreiber et al., 2018). In the case of fish feed cultivation, Chlorella vulgaris was selected as it has a suitable composition of proteins, carbohydrates, and lipids for animal feed. It was found to have less environmental impacts than A. platensis (Smetana et al., 2017). Chlorella vulgaris and A. platensis are the most widely recognized strains when studying food production (Smetana et al., 2017). Construction and operation of a tubular photobioreactor would not be affected by the algae strain being grown. Therefore, the process had identical inputs to that of the algae strain selected for biodiesel. The same approach was applied for harvesting and centrifugation. Centrifugation could be employed to separate the dry biomass from the water regardless of strain because it does not rely on specific strain properties.

Once cultivated and harvested, microalgae can be fractionated into a protein powder that can be used for a variety of animal feeds (Smetana et al., 2017). In this study, fish feed was chosen as the specific feed produced as microalgae are well suited for it. Microalgae has appropriate proportions of proteins, lipids, and carbohydrates for fish meal and already contains essential amino acids required in fish feed, eliminating the need to add them as a secondary step. Microalgae-derived fish feed can be used as a refrigerated paste or as a dry product created by either pelletizing or extruding (Nagappan et al., 2021). A dry product is in higher demand than refrigerated paste, and the extruder is the most common method for this process (Nagappan et al., 2021); therefore, this method was chosen for this study.

The fractionation process for Chlorella requires 0.7 kWh/kg of energy, yielding 0.85 kg of protein-rich powder and 0.15 kg of oil (Smetana et al., 2017). The extracted oil substitutes conventional vegetable oil on a mass basis. This substitution accounts for the environmental impacts avoided by not producing an equivalent amount of conventional vegetable oil (soybean oil). The protein powder, containing approximately 45−55% protein, is then mixed with water and subjected to an extrusion process to produce fish feed pellets (El-Naggar et al., 2020; Smetana et al., 2017). The extrusion process requires an additional 0.13 kWh of electricity per kilogram of feed material processed, according to scaled data from industrial feed production (Li et al., 2022). The resulting microalgae-based fish feed substitutes conventional fish food on a mass basis (Yacout et al., 2016), leveraging its high protein content and balanced nutrient profile to meet the dietary needs of farmed fish.

After centrifugation, microalgae are dehydrated for direct application as a biofertilizer. In order to dry the microalgae, both spray drying and lyophilization are available methods (González et al., 2020). For this study, spray drying was assumed as the drying method, and energy inputs were assumed as 4 GJ/tonne resulting in an 80 percent yield (Grierson et al., 2013). It was also assumed that microalgae are able to directly replace mineral fertilizer in the form of 15:15:15 NPK (nitrogen, phosphorus, potassium). Studies have shown that microalgae in a ratio of two percent algae to 98 percent soil met the requirements for use as a solid bio-based fertilizer. The microalgae applied as fertilizer demonstrated significant plant growth compared to ammonium sulfate when applied to both ryegrass and barley (González et al., 2020). Additionally, it has been demonstrated that in nutrient-deficient soils, algae resulted in comparable plant growth to plants treated with mineral fertilizer (Schreiber et al., 2018).

The fertilizers were compared based on the amount of nitrogen applied to the soil to credit traditional fertilizer production. They cannot be compared based on volume as microalgae-based fertilizer has a smaller amount of plant nutrients per kilogram. Inputs into microalgae fertilizer production indicated 41 kilograms of nitrogen per tonne of CO₂ utilized. The selected mineral fertilizer (NPK 15:15:15) is fifteen percent nitrogen. Therefore, to be equivalent to the 555 kg of dry biomass resulting from 1 tonne of carbon dioxide, the production of 273 kg of mineral fertilizer is displaced.

2.3 Life cycle impact assessment

The study utilized SimaPro 9.5, a specialized LCA software (PRé, 2023), along with the ReCiPe 2016 LCIA method (Huijbregts et al. 2016), to analyze the environmental performance of the three products. The analysis focused on five key impact categories, including a combined midpoint category for global warming (encompassing impacts on both human health and terrestrial ecosystems), along with three endpoint categories: human health (measured in disability-adjusted life years, DALY), ecosystem quality (represented as the Potentially Disappeared Fraction of species per area-year, species.yr), and resource scarcity (expressed in USD2013). These midpoint impact categories were chosen for their relevance in assessing the effectiveness of CCU technologies, which aim to capture and utilize CO₂, thereby potentially reducing global warming impacts. Including endpoint impact categories was essential for gaining a comprehensive understanding of the final environmental damage translating specific environmental pressures into broader areas of protection (Huijbregts et al. 2016).

2.4 Cradle-to-grave CO₂ emissions reduction

To assess the overall advantage of reducing carbon footprint in the optimal scenario, this study covers CO₂ emissions from various sources, including fossil fuel use and land-use changes, as well as emissions prevented in the production processes of the best-case scenarios. Fossil-based emissions are thoroughly assessed, covering the entire process from carbon capture to the production of algae-based products. This evaluation also accounts for the avoided emissions that result from replacing conventional fossil-based products with CO₂-utilizing alternatives. The approach employs a comparative evaluation of life cycle CO₂ emissions between traditional method and alternative CO₂-based pathways as shown in Figure 3. This comparison quantifies the net climate effect, highlighting the reduction in total CO₂ emissions achieved through the alternative production pathway.

Figure 3. CO₂ emissions comparison for traditional and CO₂-utilizing bioproducts manufacturing.

3.1 Contribution analysis

The contribution analysis of microalgae-based biodiesel production under worst-case scenario highlights that biodiesel production is the primary driver of environmental impacts across all categories. Substitution credits from conventional transport, natural gas, and glycerine significantly reduce the global warming impacts on human health and terrestrial ecosystems by approximately 21%, 3%, and 2%, respectively ( Figure 5). Additionally, glycerine credits reduce impacts in the ecosystem category by about 8%. In resource use, substitution credits from conventional transport and natural gas provide notable reductions of approximately 29% and 21%, respectively. While these credits offer significant reductions, they are insufficient to fully counter the high emissions from the current fossil-based electricity mix. This analysis underscores the need for cleaner energy solutions in biomass production processes to achieve more effective environmental improvements.

Figure 5. Comparative assessment of extremal scenarios in microalgal production systems.

Environmental impact analysis contrasting: (a) Midpoint impact evaluation for biodiesel production under suboptimal conditions utilizing the current grid electricity mix; (b) Associated endpoint impact indicators for the biodiesel worst-case scenario; (c) Midpoint impact categories for fish feed production under optimal conditions with 100% renewable energy integration; and (d) Corresponding endpoint impact metrics for the optimized fish feed scenario. This multi-panel analysis illustrates the spectrum of environmental implications across different production pathways and energy source configurations.

Conversely, fish feed production under best-case conditions with 100% renewable energy shows significant improvements in environmental performance. Biomass production achieves a 22% reduction in global warming impacts, further enhanced by substitution credits from conventional fish feed (36%) and vegetable oil replacement (41%). Although steam use causes a minor 7% increase, the overall impact on the environment still remains positive. While biomass production increases human health impacts by 25%, substantial credits from conventional feed (−57%) and vegetable oil (−43%) lead to net reductions. Ecosystem and resource impact categories exhibit similar positive trends, driven by effective substitutions. These findings align with previous studies that identify two major challenges in algae-based systems. The first is the intensive energy demand for processes like pumping, mixing, drying, and lipid extraction, especially when reliant on fossil fuels. The second challenge is nutrient management, particularly nitrogen and phosphorus usage, where inefficiencies can increase eutrophication and greenhouse gas emissions (Bradley et al., 2023; Fenton et al., 2014; Schade and Meier, 2020).

Despite these challenges, the present study also found that Chlorella vulgaris has the potential to replace high-material and energy-intensive aquaculture feeds. Its viability as an alternative feed is supported by its favorable nutritional profile: 45% protein, 20% fat, 20% carbohydrates, 10% minerals and vitamins, and 5% fiber (w/w, dry basis) (El-Naggar et al., 2020). Modelling the substitution of conventional feed with Chlorella vulgaris reveals even greater environmental benefits than previously anticipated. Table 2 compares microalgae-based feed (FF_TH20) with conventional aquaculture feed production. The results show significant reductions in global warming potential for both human health and terrestrial ecosystems. The substitution substantially reduces human health and ecosystem impacts, while resource impacts decrease only marginally. These findings demonstrate Chlorella vulgaris’ potential as a sustainable aquaculture feed alternative, though resource efficiency needs optimization. To make the process even more efficient, implementing emerging approaches like bioflocculation, spontaneous flocculation, and attached growth systems show promise for more efficient and economical harvesting, potentially reducing chemical use and improving harvested biomass concentration (Bilad et al., 2012; de Assis et al., 2019; de Assis et al., 2017; Eliseus et al., 2017). However, the drying step remains a challenge, with various options like solar, drum, spray, and freeze-drying each presenting trade-offs between energy use, cost, and product quality (Milledge and Heaven, 2013). These strategies, combined with ongoing research into energy-efficient and environmentally friendly methods, aim to optimize both energy use and nutrient management in algal biofuel production, addressing the key challenges identified in life cycle assessments and paving the way for more sustainable algae-based systems in the future. Overall, the potential for algae-based systems to contribute to environmental sustainability is significant, as evidenced by various studies showing substantial reductions in environmental impacts when transitioning to renewable energy sources. This highlights the importance of not only increasing the share of renewable energy in the grid mix but also improving the energy efficiency of production processes themselves. With continued advancements and a focus on overcoming key challenges, algae-based CCU and bio-product production hold promise for playing a pivotal role in mitigating climate change and promoting a more sustainable and resilient future, a vision that is thoroughly supported by the results and conclusions of the current study.

3.2 Application of top-performing scenarios

Microalgae CCU provides biomass-containing compounds useful for pharmaceuticals, food, and biofuels (Zhao and Su, 2020). However, realizing their full potential requires overcoming key challenges identified through life cycle assessments. The optimization of microalgae CCU systems depends on two critical factors—the refinement of system processes for greater efficiency and the careful integration of renewable energy sources, both of which are crucial for improving environmental performance, as examined below.

3.2.1 Impact of system efficiency and renewable energy

For carbon capture, Win et al. (2023) reported that capturing one tonne of CO₂ requires approximately 378 kWh of energy, highlighting the significant energy input needed for carbon capture systems. This energy requirement is closely tied to the efficiency of the CO₂ utilization process, which varies significantly across various studies, ranging from 40% to 93.7%, depending on specific conditions and technologies employed for microalgae cultivation (Ighalo et al., 2022). The results discussed in this study are based on a carbon utilization efficiency of 75%, which falls within the range reported in the literature. This relatively high efficiency suggests potentially lower energy requirements and environmental impacts compared to systems with lower efficiencies, as the energy needed per unit of CO₂ captured would be reduced.

Figure 6 illustrates the impact of CO₂ utilization efficiency and renewable energy integration on CO₂ emissions reduction in cultivation systems. The data reveal a clear trend: increasing CO₂ utilization efficiency from 60% to 90% and renewable energy integration from 50% to 100% significantly improve CO₂ reduction rates. Notably, with 100% renewable energy and 75% CO₂ utilization efficiency, the reduction rate nearly matches that of the scenario with 90% CO₂ utilization efficiency and 100% renewable energy. Importantly, in both the 75% and 100% renewable energy scenarios, all efficiency levels result in a net reduction of CO₂, highlighting the critical role of renewable energy in achieving positive environmental outcomes. While the combination of high efficiency at 90% and full renewable energy at 100% maximizes CO₂ reduction, the analysis indicates that balanced improvements in both parameters can yield substantial benefits without necessarily reaching the highest levels in each category. These relationships underscore the importance of optimizing both CO₂ utilization efficiency and renewable energy integration within carbon capture systems.

Figure 6. CO₂ emissions reduction during biomass production as influenced by utilization efficiency and renewable energy integration.

The analysis demonstrates a broad range of CO₂ reduction potential across the scenarios. At the lower end, with 60% efficiency and 50% renewable energy, the system results in net emissions of 343 kg CO₂ per tonne processed. In contrast, the most favorable scenario with 90% efficiency and 100% renewable energy achieves a reduction of 965 kg CO₂ per tonne CO₂ utilized, representing a significant enhancement in carbon utilization performance. Moreover, the energy intensity of CO₂ utilization could be further reduced by using flue gas directly instead of post-combustion CO₂ capture. However, direct use of flue gas can affect algae growth and lipid production due to contaminants, with impacts varying by species. Napan et al. (2015) found that at baseline heavy metal concentrations representative of coal-fired flue gas, there was a 12% increase in biomass production and 61% increase in lipid yield for Scenedesmus obliquus compared to the control. However, at higher heavy metal concentrations, both growth and lipid production were inhibited (Hess et al., 2017).

Similarly, Hess et al. (2017) observed that for Nannochloropsis salina, the addition of 14 inorganic contaminants at concentrations representative of coal-fired flue gas resulted in a 67% reduction in biomass productivity and a 32% decrease in lipid content compared to the control (Napan et al., 2015). Despite these challenges, using captured flue gas CO₂ is still more energy-efficient than virgin commercial CO₂ (Clarens et al., 2011). Overall, the CO₂ source significantly influences the energy requirements and sustainability of algae-based biofuel production. However, careful examination of flue gas composition and its suitability for specific algal strains is crucial for informed decision-making in algae-based biofuel production systems.

3.2.2 Benefits of carbon capture and utilization

In developing countries, where fossil fuels often dominate the energy landscape, coal and natural gas power plants continue to be significant sources of CO₂ emissions. However, these emissions can be repurposed through innovative carbon capture and utilization technologies, offering a pathway to more sustainable practices. One promising application is the cultivation of Chlorella vulgaris, a microalga species, to produce fish feed. Chlorella vulgaris has shown remarkable potential as an alternative to conventional, energy-intensive aquaculture feeds (Dineshbabu et al., 2019; Smetana et al., 2017). By utilizing CO₂ emissions from power plants, the production of this algae-based fish feed can significantly reduce the carbon footprint of both energy and aquaculture sectors. The process requires approximately 0.9 million tonnes of CO₂ annually to meet Thailand’s fish feed demand of 400,000 tonnes (Fachrudin, 2024), with each kilogram of algae-based feed produced potentially offsetting around 2.66 kilograms of CO₂ emissions (Table S1) (underlying data). This estimate accounts for direct emissions from algae cultivation and processing, indirect emissions from land transformation, CO₂ captured from power plants, and emissions avoided by replacing conventional feed production methods (Table S1) (underlying data). At a market price of USD 1,400 per tonne ( Indiamart, 2024), this industry could generate an annual revenue of USD 560 million. Simultaneously, it would avoid 1.1 million tonnes of CO₂ emissions per year compared to conventional feed production. This initiative could lead to employment opportunities in carbon capture and utilization industries, as well as in algae cultivation and associated fields, providing an economic boost to the region. Beyond its economic potential, fish feed derived from Chlorella vulgaris offers several environmental benefits. It can help reduce pressure on wild fish stocks traditionally used for fishmeal production (Sheikhzadeh et al., 2024), contributing to marine ecosystem conservation. Additionally, as a protein-rich and nutrient-dense feed, it can improve the efficiency and sustainability of aquaculture operations.

In addition to fish feed production, microalgae cultivation holds great promise for carbon capture and utilization, with applications extending to the production of biodiesel and biofertilizer. The biodiesel production process requires approximately 37.5 million tonnes of CO₂ annually to meet Thailand’s anticipated biodiesel demand of 4,015 million liters by 2037 as per government plans (Intamano et al., 2024). A market price of USD 1,000 per tonne (Data, 2024) would generate approximately USD 3.5 billion in revenue. Importantly, each kilogram of microalgae-based biodiesel avoids approximately 8.5 kg of CO₂ (see Table S1) (undelrying data) emissions compared to conventional fossil-based diesel, potentially reducing emissions by 30 million tonnes of CO₂ annually.

Moreover, the conversion of algal biomass into biofertilizer presents a promising market opportunity, requiring about 9 million tonnes of CO₂ annually to meet the biofertilizer demand of 5 million tonnes (Post, 2022). Assuming a market price of approximately USD 400 per tonne (Polene, 2024), this sector could generate substantial revenue of about USD 2 billion each year. Moreover, biofertilizer derived from microalgae offers significant environmental benefits, as each kilogram of this product can avoid approximately 1.2 kg of CO₂ emissions. This translates to a total reduction of around 6 million tonnes of CO₂ emissions annually, contributing to climate change mitigation efforts. In 2022, Thailand’s national CO₂ emissions reached approximately 270 million tonnes (Ritchie and Roser, 2022), with the power generation sector accounting for about 90 million tonnes (Statista, 2023), primarily from coal and natural gas. As part of its commitment to combating climate change, Thailand’s Nationally Determined Contribution (NDC) targets a 20-30% reduction in greenhouse gas emissions by 2030 (Sugsaisakon and Kittipongvises, 2024). The CO₂ utilization potential through these three microalgae-based products amounts to 47 million tonnes annually, representing 53% of the power sector’s emissions. These products could collectively offset 37 million tonnes of CO₂ per year, contributing approximately 14% towards Thailand’s total emissions reduction. By leveraging microalgae technology, Thailand could make significant strides in reducing its carbon footprint while fostering sustainable industrial practices.

However, scaling up the production of microalgae using power plant emissions faces several challenges. Substantial investments in infrastructure are required, including CO₂ capture facilities at power plants, large-scale algae cultivation systems, and processing plants for the final products (Hepburn et al., 2019). While the cultivation of algae using industrial CO₂ has been demonstrated on smaller scales, expanding to fully utilize emissions from large power plants necessitates further technological advancements and process optimizations. Market development presents another crucial consideration. Establishing and expanding markets for algae-based products may require efforts in consumer education, quality assurance, and potentially supportive policies to encourage adoption. A favorable regulatory environment, possibly including carbon pricing mechanisms or incentives for CCU technologies, would be instrumental in making these projects economically viable (Hepburn et al., 2019).

Developing efficient cultivation methods and selecting appropriate locations for production facilities will be key to addressing these concerns. Beyond these implementation challenges, the production of value-added products such as fish feed, biodiesel, and biofertilizer from microalgae using power plant emissions represents a promising approach to emissions reduction and sustainable development. As countries work towards cleaner energy futures, these technologies could serve as valuable transitional solutions, mitigating emissions from existing power infrastructure while supporting food security, energy independence, and agricultural sustainability. The potential for significant CO₂ reduction, coupled with economic benefits across multiple sectors, makes this an attractive option for countries seeking to balance development needs with climate change mitigation goals. By simultaneously addressing issues in aquaculture, transportation, and agriculture, microalgae-based CCU demonstrates a climate-friendly solution for multiple sectors in the economy. The versatility of these applications offers a pathway to create a circular economy, where waste CO₂ becomes a valuable resource for multiple industries.