CO2 Biofixation Research Articles

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

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

Maximizing Energy Content and CO2 Bio-fixation Efficiency of an Indigenous Isolated Microalga Parachlorella kessleri HY-6 Through Nutrient Optimization and Water Recycling During Cultivation.

An alternative source of energy and materials with low negative environmental impacts is essential for a sustainable future. Microalgae is a promising candidate in this aspect. The focus of this study is to optimize the supply of nitrogen and carbon dioxide during the cultivation of locally isolated strain Parachlorella kessleri HY-6. This study focuses on optimizing nitrogen and CO2 supply based on total biomass and biomass per unit amount of nitrogen and CO2. Total biomass increased from 1.23 to 2.30 g/L with an increase in nitrogen concentration from 15.8 to 47.4 mg/L. However, biomass per unit amount of nitrogen supplied was higher at low nitrogen content. Biomass and CO2 fixation rate increased at higher CO2 concentrations in bubbling air, but CO2 fixation efficiency decreased drastically. Finally, the energy content of biomass increased with increases in both nitrogen and CO2 supply. This work thoroughly analyzed the biomass composition via ultimate, proximate, and biochemical analysis. Water is recycled three times for cultivation at three different nitrogen levels. Microalgae biomass increased during the second recycling and then decreased drastically during the third. Activated carbon helped remove the organics after the third recycling to improve the water recyclability. This study highlights the importance of selecting appropriate variables for optimization by considering net energy investment in terms of nutrients (as nitrogen) and CO2 fixation efficiency and effective water recycling.

Arthrospira sp. mediated bioremediation of gray water in ceramic membrane based photobioreactor: process optimization by response surface methodology

Direct discharge of raw domestic sewage enriched with nitrogenous and phosphorous compounds into the water bodies causes eutrophication and other environmental hazards with detrimental impacts on public and ecosystem health. The present study focuses on phycoremediation of gray water with Arthrospira sp. using an innovative hydrophobic ceramic membrane-based photobioreactor system integrated with CO2 biofixation and biodiesel production, aiming for green technology development. Surfactant and oil-rich gray water collected from the domestic kitchen was used wherein, chloride, sulfate, and surfactant concentrations were statistically optimized using response surface methodology (RSM), considering maximum microalgal growth rate as a response for the design. Ideal concentrations (mg/L) of working parameters were found to be 7.91 (sulfate), 880.49 (chloride), and 144.02 (surfactant), respectively to achieve optimum growth rate of 0.43 gdwt/L/day. Enhancement of growth rate of targeted microalgae by 150% with suitable CO2 (19.5%) supply and illumination in the photobioreactor affirms its efficient operation. Additionally, harvested microalgal biomass obtained from the process showed a biodiesel content of around 5.33% (dry weight). The microalgal treatment enabled about 96.82, 87.5, and 99.8% reductions in BOD, COD, and TOC, respectively, indicating the potential of the process in pollutant assimilation and recycling of such wastewater along with value-added product generation.

Modeling and multi-objective optimization of microalgae biomass production and CO2 biofixation using hybrid intelligence approaches

This study investigates the impacts of temperature, light-dark cycles (LD), and nitrogen-phosphorus ratios (NP) on Chlorella vulgaris microalgae biomass productivity (BP) and CO2 biofixation (RCO2). Three artificial intelligence (AI) modeling approaches - boosted regression tree (BRT), artificial neural networks (ANN), and support vector regression (SVR) were applied. Bayesian optimization algorithm (BOA) was combined with each AI approach to predict BP and RCO2. Real-life experimental data, according to Box-Behnken design (BBD) were employed to assess the models using relative error (RE), coefficient of determination (R2), mean absolute error (MAE), mean absolute relative error (MARE), root mean square error (RMSE), and fractional bias (FB). The performance of the ANN and SVR models are comparable. However, the SVR model performs much better than the BRT and ANN models. Regarding RCO2, the SVR model yields low errors (MAE of 0.0128, MARE of 0.4131, RMSE of 0.0189) with a high R2 of 0.911. The value of FB is close to zero (0.0088), suggesting the model is reliable. The SVR model shows a better prediction capability of RCO2 compared to BBD with a performance improvement of 17.16%. MARE of BBD for RCO2 is 0.7409, which is higher than that of SVR model. Finally, the crow search algorithm was combined with the SVR for multi-objective optimization to determine the global optimal conditions for maximizing BP and RCO2, respectively. The optimum conditions were calculated to be 40 °C, 1:1 of N/P, and 12/12 h/h of LD with BP and RCO2 of 0.0979 g L−1d−1 and 0.1408 g L−1d−1, respectively.

High carbohydrate polymer biosynthesis and CO2 biofixation by indigenous acidophilic Coccomyxa dispar under elevated conditions system

High carbohydrate polymer biosynthesis and CO2 biofixation by indigenous acidophilic Coccomyxa dispar under elevated conditions system

Kinetic Modeling of Co2 Bio-Fixation by Microalgae for the Optimization of Carbon Supply in Various Photobioreactor Technologies and Associations

Kinetic Modeling of Co2 Bio-Fixation by Microalgae for the Optimization of Carbon Supply in Various Photobioreactor Technologies and Associations

Valorization of corn steep liquor for efficient paramylon production using Euglena gracilis: The impact of precultivation and light-dark cycle

To achieve economic and efficient production of value-added materials from mixotrophic Euglena gracilis cultivation, utilizing a cost-effective substrate and optimizing the bioprocess factors are critical. In this study, the industrial byproduct corn steep liquor (CSL) was applied to the feasibility of its use and compared with a synthetic medium. The effects of precultivation trophic mode and light-dark (LD) cycle on cell growth, biomass, CO2 biofixation, and paramylon production were investigated. The use of CSL enhanced both cell growth and biomass production by 1.5-fold. Biomass production using CSL was the highest in the photoautotrophically precultivated culture (3.69 g/L), while the highest paramylon content was observed in the heterotrophically precultivated culture (42.0%). Efficient paramylon production using CSL was accomplished by heterotrophic precultivation and applying the LD8:16 conditions. The highest CO2 biofixation rate of E. gracilis was shown in the heterotrophically precultivated culture using CSL under LD16:8 (1.07 g/L/d). CO2 biofixation rates using CSL were 2.8–6.4 fold higher than those using the synthetic medium. The valorization of the CSL promoted not only the bioconversion of CO2 but also the production of value-added materials by E. gracilis.

Cultivation and Biorefinery of Microalgae (Chlorella sp.) for Producing Biofuels and Other Byproducts: A Review

Microalgae-based carbon dioxide (CO2) biofixation and biorefinery are the most efficient methods of biological CO2 reduction and reutilization. The diversification and high-value byproducts of microalgal biomass, known as microalgae-based biorefinery, are considered the most promising platforms for the sustainable development of energy and the environment, in addition to the improvement and integration of microalgal cultivation, scale-up, harvest, and extraction technologies. In this review, the factors influencing CO2 biofixation by microalgae, including microalgal strains, flue gas, wastewater, light, pH, temperature, and microalgae cultivation systems are summarized. Moreover, the biorefinery of Chlorella biomass for producing biofuels and its byproducts, such as fine chemicals, feed additives, and high-value products, are also discussed. The technical and economic assessments (TEAs) and life cycle assessments (LCAs) are introduced to evaluate the sustainability of microalgae CO2 fixation technology. This review provides detailed insights on the adjusted factors of microalgal cultivation to establish sustainable biological CO2 fixation technology, and the diversified applications of microalgal biomass in biorefinery. The economic and environmental sustainability, and the limitations and needs of microalgal CO2 fixation, are discussed. Finally, future research directions are provided for CO2 reduction by microalgae.

Enhancing microalgae production by installing concave walls in plate photobioreactors

In order to optimize light distribution for promoting biomass growth rate of Chlorella pyrenoidosa, concave walls were installed in plate photobioreactors (PBR) to generate rotational flow field of microalgal solution circulated from top inlets to bottom outlets. Flow vortices in four corners of concave-wall PBR resulted in decreased mixing time and increased mass transfer coefficient. The CO2 bio-fixation by C. pyrenoidosa increased by 27% and chlorophyll-a concentration enhanced by 18.5% in concave-wall PBR compared to those in control (flat-wall) PBR. The concave walls diverge light rays to enhance frontal light exposure and supply more light photons into interior regions of PBRs. The promotion in light distribution and vortex flow field with concave walls enhanced light and nutrients utilization by microalgal cells, leading to an increased biomass growth rate by 21%.

Advances in the synthesis and applications of nanomaterials to increase CO2 biofixation in microalgal cultivation

Advances in the synthesis and applications of nanomaterials to increase CO2 biofixation in microalgal cultivation

Microalgae as a solution of third world energy crisis for biofuels production from wastewater toward carbon neutrality: An updated review

The boost of the greenhouse gases (GHGs, largely carbon dioxide – CO2) emissions owing to anthropogenic activity is one of the biggest global threats. Bio-CO2 emission reduction has received more and more attention as an environmentally sustainable approach. Microalgae are very popular in this regard because of excellent speed of growth, low costs of production, and resistance to extreme environments. Besides, most microalgae can undergo photosynthesis, where the CO2 and solar energy can be converted into sugar, and subsequently become biomass, providing a renewable and promising biofuel strategy with a few outstanding benefits. This review focuses on presenting CO2 sequestration by microalgae towards wastewater treatment and biodiesel production. First, the CO2 fixation mechanism by microalgae viz., sequestration and assimilation of CO2 in green microalgae as well as cyanobacteria were introduced. Besides, factors affecting CO2 sequestration in microalgae, containing microalgae species and cultivation conditions, such as light condition, photobioreactor, configuration, pH, CO2 concentration, temperature, and medium composition, were then comprehensively discussed. Special attention was given to the production of biodiesel as third-generation biofuel from various wastewater (CO2 biofixation), including processing steps of biodiesel production by microalgae, biodiesel production from wastewater, and improved methods. Furthermore, current life cycle assessment (LCA) and techno-economic analysis (TEA) used in biodiesel production were discussed. Finally, the research challenges and specific prospects were considered. Taken together, this review provides useful and updated information to facilitate the development of microalgal “green chemistry” and “environmental sustainability”.

Bioresource potential of Tetradesmus obliquusUJEA_AD: critical evaluation of biosequestration rate, biochemical and fatty acid composition in BG11 media

AbstractBACKGROUNDMicroalgae biomass is regarded as one of the most promising renewable biomass energy resources with the potential as a sustainable biological climate change mitigation agent, raw material for commercially valuable products and fossil fuel replacement. In view of that, this study isolated, identified and evaluated the potential of an indigenous freshwater green microalga strain, Tetradesmus obliquus UJEA_AD, collected from Emmarentia Dam, Johannesburg, South Africa.RESULTSMorphological analysis and sequencing of the rbcL biomarker aided in identification of the isolate as T. obliquus. Tetradesmus obliquus UJEA_AD was further batch‐cultivated autotrophically in BG11 medium and examined for biomass accumulation, CO2 biofixation rate, biochemical composition and fatty acid production. The results showed a maximum biomass accumulation of 2.78 ± 0.019 g L−1 with biomass productivity of 0.153 ± 0.001 g L−1 day−1 and specific growth rate of 0.13 ± 0.004 day–1 as well as CO2 biofixation rate of 0.265 ± 0.002 gCO2 L−1 day−1. The biochemical data of the isolate revealed 27.17% ± 0.021% carbohydrate, 38.00% ± 0.15% protein and 31.2% ± 0.80% lipids; with primary fatty acids such as palmitic acid (34.26% ± 2.02%), linolenic acid (18.08 ± 5.29), trans‐13‐octadecenoic acid (12.32 ± 0.92) and phytol, 2‐methylbutanoate (12.31 ± 1.02).CONCLUSIONThese findings suggest that T. obliquus UJEA_AD is capable of producing bioproducts of economic value with an excellent CO2 bio‐mitigation potential when cultivated at optimum conditions in an autotrophic mode. Moreover, lipid extracted from T. obliquus UJEA_AD met the biodiesel quality standards of the USA and EU, making the isolate a promising commercial biodiesel feedstock. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Optimization of cultivation condition of newly isolated strain Chlorella sorokiniana pa.91 for CO2 bio-fixation and nutrients removal from wastewater: Impact of temperature and light intensity

Optimization of cultivation condition of newly isolated strain Chlorella sorokiniana pa.91 for CO2 bio-fixation and nutrients removal from wastewater: Impact of temperature and light intensity

Development a novel hexagonal airlift flat plate photobioreactor for the improvement of microalgae growth that simultaneously enhance CO2 bio-fixation and wastewater treatment

A novel hexagonal airlift flat plate (HAFP) photobioreactor was designed to improve microalgae growth rate and compared with traditional flat plate (TFP) photobioreactor. The computational fluid dynamics (CFD) simulation was used to determine hydrodynamic parameters and optimal aeration rate in the photobioreactors. Additionally, the capability of the HAFP photobioreactor to enhance microalgae based CO2 bio-fixation and wastewater treatment were investigated. The results of CFD simulation indicated that the HAFP photobioreactor could improve hydrodynamic parameters of turbulence kinetic energy (TKE), average fluid velocity, dead zone (DZ), and water shear stress (WSS) up to 78 %, 41 %, 44 % and 40 %, respectively, under optimal aeration rate of 0.6 vvm. The proposed HAFP photobioreactor showed a drastic improvement in microalgae growth (up to 61 %). The maximum CO2 removal of 53.8 % and bio-fixation of 0.85 g L−1 d−1 were achieved in the HAFP photobioreactor which were approximately 70 % more than that in the TFP photobioreactor. The results suggested that the HAFP photobioreactor could accelerate nutrients removal and achieve remarkably higher efficiencies of 91 %, 99 %, 97 % and 93 % of ammonia (NH3), nitrate (NO3−), phosphate (PO43−) and chemical oxygen demand (COD) within seven days of cultivation.

Analysis of the Emergent Climate Change Mitigation Technologies.

A climate change mitigation refers to efforts to reduce or prevent emission of greenhouse gases. Mitigation can mean using new technologies and renewable energies, making older equipment more energy efficient, or changing management practices or consumer behavior. The mitigation technologies are able to reduce or absorb the greenhouse gases (GHG) and, in particular, the CO2 present in the atmosphere. The CO2 is a persistent atmospheric gas. It seems increasingly likely that concentrations of CO2 and other greenhouse gases in the atmosphere will overshoot the 450 ppm CO2 target, widely seen as the upper limit of concentrations consistent with limiting the increase in global mean temperature from pre-industrial levels to around 2 °C. In order to stay well below to the 2 °C temperature thus compared to the pre-industrial level as required to the Paris Agreement it is necessary that in the future we will obtain a low (or better zero) emissions and it is also necessary that we will absorb a quantity of CO2 from the atmosphere, by 2070, equal to 10 Gt/y. In order to obtain this last point, so in order to absorb an amount of CO2 equal to about 10 Gt/y, it is necessary the implementation of the negative emission technologies. The negative emission technologies are technologies able to absorb the CO2 from the atmosphere. The aim of this work is to perform a detailed overview of the main mitigation technologies possibilities currently developed and, in particular, an analysis of an emergent negative emission technology: the microalgae massive cultivation for CO2 biofixation.

Biologically-mediated carbon capture and utilization by microalgae towards sustainable CO2 biofixation and biomass valorization – A review

The continuously rising emission of carbon dioxide (CO2) is a universal hazard which urgently requires collaborative action between policymakers and scientists. International treaties such as the Paris Agreement (with 196 signatories) reflect the importance of anthropogenic climate change as a truly global public concern. Towards the aim of climate recovery, the most broadly utilized CO2 reduction strategies, including carbon capture and storage (CCS); carbon capture, utilization, and storage (CCUS); and carbon capture and utilization (CCU) are reviewed herein. Of these methods, CCU shows the greatest potential by recycling captured CO2 and harnessing it as a resource to generate emissions-neutral or -negative value-added products (VAPs). Within CCU methodologies, biologically-mediated CCU (bio-CCU) by microalgae is a promising biotechnology to drastically reduce CO2 emissions. This review therefore details the mechanisms of photosynthesis to sequester CO2 and incorporate it into valuable biomolecules. Microalgal cells utilize CO2 as precursors of macromolecules, including lipids, proteins, carbohydrates, and pigments; all of which are discussed within the frame of industrial relevance and market value. The biofixation potential of microalgae is clearly demonstrated by the carbon content of the myriad VAPs they produce. Moreover, pathways towards decreasing carbon footprint (via carbon capture prior to emission to the atmosphere) and increasing carbon handprint (reducing carbon emissions by consuming CO2-neutral or -negative products) related to bio-CCU are presented herein. Finally, existing challenges and knowledge gaps are acknowledged and described, and future research needs are recommended.

The Microalga Chlorella vulgaris as a Natural Bioenergetic System for Effective CO2 Mitigation—New Perspectives against Global Warming

In the present contribution, the differentiation in the molecular structure and function of the photosynthetic apparatus of the unicellular green alga Chlorella vulgaris was studied at several light intensities (0–400 μmol m−2 s−1) and various CO2 concentrations (0.04–60% CO2), in completely autotrophic conditions. Asymmetries that occur by different light intensities and CO2 concentrations induce metabolic and functional changes. Using chlorophyll fluorescence induction techniques (OJIP test), we showed that Chlorella vulgaris tolerates extremely high CO2 levels and converts them photosynthetically into valuable products, including O2 and biomass rich in carbohydrates and lipids. Interestingly, the microalga Chlorella vulgaris under extremely high CO2 concentrations induces a new metabolic state intensifying its photosynthetic activity. This leads to a new functional symmetry. The results highlight a potent CO2 bio-fixation mechanism of Chlorella vulgaris that captures up to 288 L CO2 L PCV−1 day−1 under optimal conditions, therefore, this microalga can be used for direct biological CO2-reducing strategies and other green biotechnological applications. All of the above suggest that Chlorella vulgaris is one of the most prominent competitors for a closed algae-powered bioreactor that is able to consume huge amounts of CO2. Thus, it is a sustainable and natural bioenergetic system with perspectives in dealing with major environmental issues such as global warming. In addition, Chlorella vulgaris cultures could also be used as bioregeneration systems in extraterrestrial missions for continuous atmospheric recycling of the human settlements, paving the way for astrobiological applications.

Techno-economic analysis of microalgae related processes for CO2 bio-fixation

The current need to reduce greenhouse gas emissions is pushing the incorporation of technologies to achieve industrial decarbonisation in Europe. The present work develops a techno-economic tool that analyses different scenarios to assess microalgae production in some foreseeable situations, and determines the ones in which the contribution of CO2 biofixation would be relevant. The biomass production cost ranged between 0.41 and 13.06 €/kg. It was also possible to recover 0.03–0.1 €/kg CO2 depending on its temporal variation and the amount of biomass produced. This analysis aims to identify the technologies and operational conditions viable for the different applications. According to the scenarios considered, microalgae technology could be competitive if the emission rights market reaches expected costs of approximately 50 €/t CO2 in the near future (2030). Otherwise, microalgae related processes can be also reliable for different medium- and high-value applications, but only if adequate technologies and operational conditions are considered. The information here provided supports decision making processes for microalgae based processes.

Enhanced bioenergy recovery and nutrient removal from swine wastewater using an airlift-type photosynthetic microbial fuel cell

Swine wastewater (SW) was used herein as the substrate in an airlift-type photosynthetic microbial fuel cell (APMFC) for power generation, and also, after anode pre-treatment, as a medium for Chlorella vulgaris cultivation in the cathode compartment accompanied with CO2 biofixation. Compared to heterotrophic cultivation, APMFC under mixotrophic cultivation showed a better performance in biomass yield, lipid accumulation and power generation. The highest chemical oxygen demand (COD) removal (96.3%), total organic carbon (TOC) removal (95.1%), NH4+-N removal (99.1%), and total phosphorus (TP) removal (98.9%) were achieved using 2-fold diluted SW. In APMFC (SW of 2-fold dilution), the highest CO2 biofixation rate and lipid productivity reached 1149 mg L−1 d−1 and 164 mg L−1 d−1, respectively. Ammonium migration from the anodic compartment to the cathodic compartment gradually increased as the ammonium concentration increased in the anolyte. The energy balance analysis suggested that the highest net energy output reached 1.92 kWh m−3 in APMFC fed with 2-fold diluted SW, which showed a superiority in clean energy production. Microbial community analysis indicated that the electrogenic microorganisms were further enriched in the anodic biofilm, which could enhance the power generation. This study provided a promising way for simultaneous SW treatment, CO2 biofixation and bioenergy generation.

Enhanced Arthrospira platensis Biomass Production Combined with Anaerobic Cattle Wastewater Bioremediation.

Microalgae biomasses offer important benefits regarding macromolecules that serve as promising raw materials for sustainable production. In the present study, the microalgae Arthrospira platensis DHR 20 was cultivated in horizontal photobioreactors (HPBR), with and without temperature control, in batch mode (6 to 7 days), with anaerobically digested cattle wastewater (ACWW) as substrate. High dry biomass concentrations were observed (6.3–7.15 g L−1). Volumetric protein, carbohydrate, and lipid productivities were 0.299, 0.135, and 0.108 g L−1 day−1, respectively. Promising lipid productivities per area were estimated between 22.257 and 39.446 L ha−1 year−1. High CO2 bio-fixation rates were recorded (875.6–1051 mg L−1 day−1), indicating the relevant potential of the studied microalgae to mitigate atmospheric pollution. Carbon concentrations in biomass ranged between 41.8 and 43.6%. ACWW bioremediation was satisfactory, with BOD5 and COD removal efficiencies of 72.2–82.6% and 63.3–73.6%. Maximum values of 100, 95.5, 92.4, 80, 98, and 94% were achieved concerning the removal of NH4+, NO3−, Pt, SO42−, Zn, and Cu, respectively. Total and thermotolerant coliform removals reached 99–99.7% and 99.7–99.9%. This microalgae-mediated process is, thus, promising for ACWW bioremediation and valuation, producing a microalgae biomass rich in macromolecules that can be used to obtain friendly bio-based products and bioenergy.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12155-021-10258-4.