Biosequestration of atmospheric CO2 and flue gas-containing CO2 by microalgae

The role of microbiome in carbon sequestration and environment security during wastewater treatment

Wastewater treatment is an essential aspect of the earth's sustainable future. However, different wastewater treatment methods are responsible for carbon discharge into the environment, raising environmental risks. Hence, such wastewater treatment methods are required that can minimize carbon release without compromising the treatment quality. Microbiome-based carbon sequestration is a potential method for achieving this goal. Limited studies have been carried out to investigate how microbes can capture and utilize CO₂. This review summarizes the approaches including microbial electrolytic carbon capture, microbial electrosynthesis, microbial fuel cell, microalgae cultivation, and constructed wetlands that employ microbes to capture and utilize CO₂. Electroactive Bacteria (EAB) convert carbon dioxide to carbonates and bicarbonates in subsequent steps after organic matter decomposition. Similarly, microbial electrosynthesis (MES) not only helps capture carbon but also produces secondary products (production of polyhydroxyalkanoates by Gram-negative rod Aeromonas hydrophila bacteria) of commercial importance during wastewater treatment. In addition to this, microbial carbon capture cells (MCCs) have been now utilized for energy generation and carbon sequestration at the same time during wastewater treatment. Moreover, microalgae cultivation has also been found to capture CO₂ at a rapid pace while releasing O₂ as a consequence of photosynthesis. Hence, microbe-based wastewater treatment has quite a potential due to two-fold benefits like carbon sequestration and by-product formation.

A newly isolated microalga Chlamydomonas sp. YC to efficiently remove ammonium nitrogen of rare earth elements wastewater

The aim of this study was to establish a practical approach to remove ammonium nitrogen of rare earth elements (REEs) wastewater by an indigenous photoautotrophic microalga. Firstly, a new microalgal strain was successfully isolated from REEs wastewater and identified as Chlamydomonas sp. (named Chlamydomonas sp. YC). The obtained results showed that microalga could completely remove the NH₄⁺-N of 10% REEs wastewater after 10 days of cultivation; however, the highest NH₄⁺-N removal rate was attained by microalga to treat undiluted REEs wastewater. Then, three cultivation modes including batch, semi-continuous and continuous cultivation methods were developed to evaluate the ability of NH₄⁺-N removal rate by this microalga to treat diluted (10%) and undiluted REEs wastewater. It was found that, Chlamydomonas sp. YC exhibited superior performance towards NH₄⁺-N removal rates (32.75-61.05 mg/(L·d)) by semi-continuous and continuous processes for the treatments of 10% and undiluted REEs wastewater in comparison to the results (19.50-30.38 mg/(L·d) by batch process. Interestingly, under the same treatment conditions, among the three cultivation modes, microalga exhibited the highest removal rates of NH₄⁺-N in undiluted REEs wastewater by semi-continuous (61.05 mg/(L·d)) and continuous (57.10 mg/(L·d) processes. In term of the biochemical analysis, microalgal biomass obtained from the wastewater treatment had 35.40-44.40% carbohydrate and 4.97-6.03% lipid, which could be potential ingredients for sustainable biofuels production. And the highest carbohydrate and lipid productivities attained by Chlamydomonas sp. YC in the continuous mode were 226.36 mg/(L·d) and 32.98 mg/(L·d), respectively. Taken together, the established processes mediated with Chlamydomonas sp. YC via continuous cultivation was the great promising approaches to efficiently remove NH₄⁺-N of REEs wastewater and produce valuable biomass for sustainable and renewable biofuels in a simultaneous manner.

Physiological and transcription level responses of microalgae Auxenochlorella protothecoides to cold and heat induced oxidative stress

Temperature is a crucial factor affecting microalgae CO₂ capture and utilization. However, an in-depth understanding of how microalgae respond to temperature stress is still unclear. In particular, the regulation mechanism under opposite temperature (heat and cold) stress had not yet been reported. In this study, the physicochemical properties and transcription level of related genes of microalgae Auxenochlorella protothecoides UTEX 2341 under heat and cold stress were investigated. Heat stress (Hs) caused a drastic increase of reactive oxygen species (ROS) in UTEX 2341. As key elements responded to Hs, superoxide dismutase (SOD) enzyme increased by 150%, 70%, and 30% in activity, and nitric oxide (NO) grew by 409.6%, 212.5%, and 990.4% in content compared with the control at 48 h, 96 h, 168 h. Under cold stress (Cs), ROS increased in the early stage and decreased in the later stage. As key factors responded to Cs, proline (Pro) increased respectively by 285%, 383%, and 81% in content, and heat shock transcriptional factor HSFA1d increased respectively by 161%, 71%, and 204% in transcript level compared with the control at 48 h, 96 h, 168 h. Furthermore, the transcript level of antioxidant enzymes or antioxidant coding genes was consistent with the changing trend of enzymes activity or antioxidant content. Notably, both glutathione (GSH) and heat shock protein 97 (hsp 97) were up-regulated in response to Hs and Cs. In conclusion, GSH and hsp 97 were the core elements of UTEX 2341 in response to both Hs and Cs. SOD and NO were the key elements that responded to Hs, while proline and HSFA1d were the key elements that responded to Cs. This study provided a basis for the understanding of the response mechanism of microalgae under temperature stress and the improvement of the microalgae tolerance to temperature stress.

Cyanobacteria as a Promising Alternative for Sustainable Environment: Synthesis of Biofuel and Biodegradable Plastics

With the aim to alleviate the increasing plastic burden and carbon footprint on Earth, the role of certain microbes that are capable of capturing and sequestering excess carbon dioxide (CO2) generated by various anthropogenic means was studied. Cyanobacteria, which are photosynthetic prokaryotes, are promising alternative for carbon sequestration as well as biofuel and bioplastic production because of their minimal growth requirements, higher efficiency of photosynthesis and growth rates, presence of considerable amounts of lipids in thylakoid membranes, and cosmopolitan nature. These microbes could prove beneficial to future generations in achieving sustainable environmental goals. Their role in the production of polyhydroxyalkanoates (PHAs) as a source of intracellular energy and carbon sink is being utilized for bioplastic production. PHAs have emerged as well-suited alternatives for conventional plastics and are a parallel competitor to petrochemical-based plastics. Although a lot of studies have been conducted where plants and crops are used as sources of energy and bioplastics, cyanobacteria have been reported to have a more efficient photosynthetic process strongly responsible for increased production with limited land input along with an acceptable cost. The biodiesel production from cyanobacteria is an unconventional choice for a sustainable future as it curtails toxic sulfur release and checks the addition of aromatic hydrocarbons having efficient oxygen content, with promising combustion potential, thus making them a better choice. Here, we aim at reporting the application of cyanobacteria for biofuel production and their competent biotechnological potential, along with achievements and constraints in its pathway toward commercial benefits. This review article also highlights the role of various cyanobacterial species that are a source of green and clean energy along with their high potential in the production of biodegradable plastics.

Sustainable Microalgae and Cyanobacteria Biotechnology

Marine organisms are a valuable source of new compounds, many of which have remarkable biotechnological properties, such as microalgae and cyanobacteria, which have attracted special attention to develop new industrial production routes. These organisms are a source of many biologically active molecules in nature, including antioxidants, immunostimulants, antivirals, antibiotics, hemagglutinates, polyunsaturated fatty acids, peptides, proteins, biofuels, and pigments. The use of several technologies to improve biomass production, in the first step, industrial processes schemes have been addressed with different accomplishments. It is critical to consider all steps involved in producing a bioactive valuable compound, such as species and strain selection, nutrient supply required to support productivity, type of photobioreactor, downstream processes, namely extraction, recovery, and purification. In general, two product production schemes can be mentioned; one for large amounts of product, such as biodiesel or any other biofuel and the biomass for feeding purposes; the other for when the product will be used in the human health domain, such as antivirals, antibiotics, antioxidants, etc. Several applications for microalgae have been documented. In general, the usefulness of an application for each species of microalgae is determined by growth and product production. Furthermore, the use of OMICS technologies enabled the development of a new design for human therapeutic recombinant proteins, including strain selection based on previous proteomic profiles, gene cloning, and the development of expression networks. Microalgal expression systems have an advantage over traditional microbial, plant, and mammalian expression systems for new and sustainable microalga applications, for responsible production and consumption.

Emerging Trends in Sustainable CO2 -Management Materials

With the rising level of atmospheric CO₂ worsening climate change, a promising global movement toward carbon neutrality is forming. Sustainable CO₂ management based on carbon capture and utilization (CCU) has garnered considerable interest due to its critical role in resolving emission-control and energy-supply challenges. Here, a comprehensive review is presented that summarizes the state-of-the-art progress in developing promising materials for sustainable CO₂ management in terms of not only capture, catalytic conversion (thermochemistry, electrochemistry, photochemistry, and possible combinations), and direct utilization, but also emerging integrated capture and in situ conversion as well as artificial-intelligence-driven smart material study. In particular, insights that span multiple scopes of material research are offered, ranging from mechanistic comprehension of reactions, rational design and precise manipulation of key materials (e.g., carbon nanomaterials, metal-organic frameworks, covalent organic frameworks, zeolites, ionic liquids), to industrial implementation. This review concludes with a summary and new perspectives, especially from multiple aspects of society, which summarizes major difficulties and future potential for implementing advanced materials and technologies in sustainable CO₂ management. This work may serve as a guideline and road map for developing CCU material systems, benefiting both scientists and engineers working in this growing and potentially game-changing area.

Technoeconomic Evaluation of Microalgae Oil Production: Effect of Cell Disruption Method

Microalgae have a high capacity to capture CO2. Additionally, biomass contains lipids that can be used to produce biofuels, biolubricants, and other compounds of commercial interest. This study analyzed various scenarios for microalgae lipid production by simulation. These scenarios include cultivation in raceway ponds, primary harvest with three flocculants, secondary harvest with pressure filter (and drying if necessary), and three different technologies for the cell disruption step, which facilitates lipid extraction. The impact on energy consumption and production cost was analyzed. Both energy consumption and operating cost are higher in the scenarios that consider bead milling (8.79–8.88 kWh/kg and USD 41.06–41.41/kg), followed by those that consider high-pressure homogenization (HPH, 5.39–5.46 kWh/kg and USD 34.26–34.71/kg). For the scenarios that consider pressing, the energy consumption is 5.80–5.88 kWh/kg and the operating cost is USD 27.27–27.88/kg. The consumption of CO2 in scenarios that consider pressing have a greater capture (11.23 kg of CO2/kg of lipids). Meanwhile, scenarios that consider HPH are the lowest consumers of fresh water (5.3 m3 of water/kg of lipids). This study allowed us to develop a base of multiple comparative scenarios, evaluate different aspects involved in Chlorella vulgaris lipid production, and determine the impact of various technologies in the cell disruption stage.

Biofixation of Air Emissions and Biomass Valorization-Evaluation of Microalgal Biotechnology

This research appraised the simultaneous biofixation, that is not quite common in scientific literature, of carbon dioxide (CO₂) and nitric oxides (NO_x) by microalgae species Chlorella vulgaris, Haematococcus pluvialis, and Scenedesmus subspicatus. The experimental design was established by five treatments with gas concentrations between control-0.04% of CO₂, 5 to 15% of CO₂, and 30 to 100 ppm of NOx. Parameters such as pH, growth, productivity, lipids, protein, carbon/ nitrogen ratio, and astaxanthin were evaluated. For all species, the maximal growth and productivity were achieved with 5% of CO₂ and 30 ppm of NO_x. Regarding protein content, for all the three species, better results were obtained at higher concentrations of CO₂ and NOx. These results prove the microalgae capacity for CO₂ and NO_x biofixation and reuse of biomass as a source of high value-added products, such as lipids, proteins, and astaxanthin. These findings support the indication of these species for flue gas treatment process and use in biorefineries systems.

Evaluation of protein production in rice seedlings under dark conditions

Although plants have several advantages for foreign protein production, cultivation of transgenic plants in artificial plant growth facilities involves the use of a great amount of electricity for lightning and air conditioning, reducing cost-effectiveness. Protein production in plants grown in darkness can overcome this problem, but the amount of protein produced in the dark is unknown. In this study, the total amount of soluble protein produced in rice seedlings germinated and grown in light or darkness were examined at several time points after germination and under different temperature, nutritional, and seedling density conditions. Our results indicate that rice seedlings grown in darkness produce a comparable amount of total soluble protein to those grown in light. Furthermore, we found that the best conditions for protein production in dark-grown rice seedlings are large seeds germinated and grown for 10-12 days at 28 °C supplemented with Murashige and Skoog medium and 30 g/l sucrose in dense planting. Therefore, our results suggest that foreign proteins can be produced in rice seedlings in the dark, with a reduced electricity use and an increase in cost-effectiveness.

Emerging biological wastewater treatment using microalgal-bacterial granules: A review

Aiming at deepening the understanding of the formation and evolution of emerging microalgal-bacterial granule (MBG)-based wastewater treatment systems, the recent advances regarding the formation processes, transfer phenomena, innovative bioreactors development and wastewater treatment performance of MBG-based systems are comprehensively reviewed in this work. Particularly, the successful establishments of MBG-based systems with various inocula are summarized. Besides, as the indispensable factors for biochemical reactions in MBGs, the light and substrates (organic matters, inorganic nutrients, etc) need to undergo complicated and multi-scale transfer processes before being assimilated by microorganisms within MBGs. Therefore, the involved transfer phenomena and mechanisms in MBG-based bioreactors are critically discussed. Subsequently, some recent advances of MBG-based bioreactors, the application of MBG-based systems in treating various synthetic and real wastewater, and the future development directions are discussed. In short, this review helps in promoting the development of MBG-based systems by presenting current research status and future perspectives.

Application of Liquid Waste from Biogas Production for Microalgae Chlorella sp. Cultivation

Microalgae biomass is a viable feedstock for a wide range of industries. Recently, there has also been interest in the ability of microalgae biomass applications for biofuel production. In the meantime, the cultivation of microalgae biomass requires high energy costs, and the application of microalgae for technical purposes is still problematic. A significant part of the cost of biomass arises from the nutrients used for cultivation. Chemical compounds included in the microalgae cultivation media can be replaced by suitable wastes containing nitrogen, phosphorus, and other elements. This could reduce the microalgae biomass cultivation price and allow cheaper biomass to be used for biofuel production. The aim of this work was to comprehensively investigate and optimize the growth process of microalgae using liquid waste (liquid waste after biogas production from sewage sludge and distillers’ grain) as a source of nitrogen and phosphorus, and technical glycerol as a carbon source. It was found that higher levels of waste in the cultivation media were found to inhibit the accumulation of microalgal biomass, with the optimum level corresponding to a nitrogen concentration of 0.08 g/L. The influence of technical glycerol from biodiesel production on the yield of microalgal biomass was investigated, and it was found that the addition of 6% glycerol allows an increase in the concentration of microalgal biomass in the cultivation media, from 18.1 to 20.6%.

Emerging microalgae-based technologies in biorefinery and risk assessment issues: Bioeconomy for sustainable development

Industrial wastewater treatment is of paramount importance considering the safety of the aquatic ecosystem and its associated health risk to humankind inhabiting near the water bodies. Microalgae-based technologies for remediation of environmental pollutants present avenues for bioenergy applications and production of value-added biochemicals having pharmaceutical, nutraceutical, antioxidants, carbohydrate, phenolics, long-chain multi-faceted fatty acids, enzymes, and proteins which are considered healthy supplements for human health. Such a wide range of products put up a good case for the biorefinery concept. Microalgae play a pivotal role in degrading complex pollutants, such as organic and inorganic contaminants thereby efficiently removing them from the environment. In addition, microalgal species, such as Botryococcus braunii, Tetraselmis suecica, Phaeodactylum tricornutum, Neochloris oleoabundans, Chlorella vulgaris, Arthrospira, Chlorella, and Tetraselmis sp., etc., are also reported for generation of value-added products. This review presents a holistic view of microalgae based biorefinery starting from cultivation and harvesting of microalgae, the potential for remediation of environmental pollutants, bioenergy application, and production of value-added biomolecules. Further, it summarizes the current understanding of microalgae-based technologies and discusses the risks involved, potential for bioeconomy, and outlines future research directions.

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".

Distinctive correlations between cell concentration and cell size to microalgae biomass under increasing carbon dioxide

Carbon capture and storage (CCS) via microalgae cultivations is getting renewed interest as climate change mitigation effort, owing to its excellent photosynthetic and CO₂ fixation capability. Microalgae growth is monitored based on their biomass, cell concentrations and cell sizes. The key parametric relationships on microalgae growth under CO₂ are absent in previous studies and this inadequacy hampers the design and scale-up of microalgae-based CCS. In this study, three representative microalgae species, Chlorella, Nostoc and Chlamydomonas, were investigated for establishing key correlations of cell concentrations and sizes towards their biomass fluctuations under CO₂ influences of 0% to 20% volume ratios (v/v). This revealed that Chlorella and Chlamydomonas cell concentrations significantly contributed towards increasing biomass concentration under CO₂ elevations. Chlorella and Nostoc cell sizes were enhanced at 20% (v/v). These findings provided new perspectives on growth responses under increasing CO₂ treatment, opening new avenues on CCS schemes engineering designs and biochemical production.

Enhanced removal efficiency of sulfamethoxazole by acclimated microalgae: Tolerant mechanism, and transformation products and pathways

This study utilized sulfamethoxazole (SMX) acclimatization to enhance the tolerance and biodegradation capacity of Chlorella vulgaris. Compared to wild C. vulgaris, the growth inhibition and oxidative damage induced by SMX evidently decreased in acclimated C. vulgaris, and meanwhile photosynthetic and antioxidant activities were significantly promoted. The physiological analyses with the aid of principal component analysis revealed the increase of catalase and glutathione reductase activities was the critical tolerant mechanism of acclimated C. vulgaris. As the consequence, the acclimated C. vulgaris exhibited enhanced efficiency and (pseudo-first-order) kinetic rate for removal of SMX. The distribution analysis of residual SMX demonstrated the biodegradation was the major removal mechanism of SMX by C. vulgaris, while bioadsorption and bioaccumulation made pimping contributions. During the degradation process of SMX, nine transformation products (TPs) were identified. Based on the identified TPs, a possible transformation pathway was proposed.

Microalgal Biorefinery Concepts’ Developments for Biofuel and Bioproducts: Current Perspective and Bottlenecks

Microalgae have received much interest as a biofuel feedstock. However, the economic feasibility of biofuel production from microalgae does not satisfy capital investors. Apart from the biofuels, it is necessary to produce high-value co-products from microalgae fraction to satisfy the economic aspects of microalgae biorefinery. In addition, microalgae-based wastewater treatment is considered as an alternative for the conventional wastewater treatment in terms of energy consumption, which is suitable for microalgae biorefinery approaches. The energy consumption of a microalgae wastewater treatment system (0.2 kW/h/m³) was reduced 10 times when compared to the conventional wastewater treatment system (to 2 kW/h/m³). Microalgae are rich in various biomolecules such as carbohydrates, proteins, lipids, pigments, vitamins, and antioxidants; all these valuable products can be utilized by nutritional, pharmaceutical, and cosmetic industries. There are several bottlenecks associated with microalgae biorefinery. Hence, it is essential to promote the sustainability of microalgal biorefinery with innovative ideas to produce biofuel with high-value products. This review attempted to bring out the trends and promising solutions to realize microalgal production of multiple products at an industrial scale. New perspectives and current challenges are discussed for the development of algal biorefinery concepts.

Improved high-throughput screening technique to rapidly isolate Chlamydomonas transformants expressing recombinant proteins

Abstract

The single-celled eukaryotic green alga Chlamydomonas reinhardtii has long been a model system for developing genetic tools for algae, and is also considered a potential platform for the production of high-value recombinant proteins. Identifying transformants with high levels of recombinant protein expression has been a challenge in this organism, as random integration of transgenes into the nuclear genome leads to low frequency of cell lines with high gene expression. Here, we describe the design of an optimized vector for the expression of recombinant proteins in Chlamydomonas, that when transformed and screened using a dual antibiotic selection, followed by screening using fluorescence activated cell sorting (FACS), permits rapid identification and isolation of microalgal transformants with high expression of a recombinant protein. This process greatly reduces the time required for the screening process, and can produce large populations of recombinant algae transformants with between 60 and 100% of cells producing the recombinant protein of interest, in as little as 3 weeks, that can then be used for whole population sequencing or individual clone analysis. Utilizing this new vector and high-throughput screening (HTS) process resulted in an order of magnitude improvement over existing methods, which normally produced under 1% of algae transformants expressing the protein of interest. This process can be applied to other algal strains and recombinant proteins to enhance screening efficiency, thereby speeding up the discovery and development of algal-derived recombinant protein products.

Key points

• A protein expression vector using double-antibiotic resistance genes was designed

• Double antibiotic selection causes fewer colonies with more positive for phenotype

• Coupling the new vector with FACS improves microalgal screening efficiency > 60%

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-11790-9.

A novel flat-panel photobioreactor for simultaneous production of lutein and carbon sequestration by Chlorella sorokiniana TH01

Carbon dioxide is the major cause of global warming. However, it is a carbon source for phototrophic production of chemicals from microalgae. In this work, a novel flat-panel photobioreactor (FPP) was used for maximization of biomass and lutein production and CO₂ fixation by a lutein-rich C. sorokiniana TH01. CO₂ concentration, light intensity and aeration rate were optimized as 5%, 150 µmol/m²/s and 1 L/min, respectively. The highest biomass productivity, lutein productivity and CO₂ fixation efficiency were measured for indoor single and sequential FPPs were 284 - 469 mg/L/d, 2.57 - 4.57 mg/L/d, and 63 - 100%, respectively. In a climatic condition of 25.5 - 33 °C and 86 - 600 µmol/m²/s, C. sorokiniana TH01 achieved lutein productivity and CO₂ fixation efficiency of 2.1 - 3.03 mg/L/d and 56 - 81%, respectively, while the comparable biomass productivity of 284 - 419 mg/L/d was maintained. This pioneered FPP system was efficiently demonstrated for production of algal lutein from CO₂.

Oriented conversion of agricultural bio-waste to value-added products - A schematic review towards key nutrient circulation

Agriculture bio-waste is one of the largest sectors for nutrient circulation and resource recovery. This review intends to summarize the possible scheme through coupling chemical conversion of crop straws to biochar and biological conversion of livestock waste to value-added products thus reaching key nutrient circulation. Chemical conversion of crop straws to biochar was reviewed through summarizing the preparation methods and functional modification of biochar. Then, high-solid two-phase anaerobic conversion of agriculture bio-waste to value-added products and improved performance of bio-conversion through byproduct gases reuse and biochar supplementation were reviewed. Finally, high quality compost production through amendment of biochar and residual digestate was proposed with analysis of reduced nitrogen emission and carbon balance. The biological mechanism of synergistic regulation of carbon and nitrogen loss during bio-conversion with biochar was also reviewed. This will provide a model for synergistic conversion of agricultural wastes to value added products pursuing key nutrient circulation.

Production of microalgae with high lipid content and their potential as sources of nutraceuticals

In the current global scenario, the world is under a serious dilemma due to the increasing human population, industrialization, and urbanization. The ever-increasing need for fuels and increasing nutritional problems have made a serious concern on the demand for nutrients and renewable and eco-friendly fuel sources. Currently, the use of fossil fuels is creating ecological and economic problems. Microalgae have been considered as a promising candidate for high-value metabolites and alternative renewable energy sources. Microalgae offer several advantages such as rapid growth rate, efficient land utilization, carbon dioxide sequestration, ability to cultivate in wastewater, and most importantly, they do not participate in the food crop versus energy crop dilemma or debate. An efficient microalgal biorefinery system for the production of lipids and subsequent byproduct for nutraceutical applications could well satisfy the need. But, the current microalgal cultivation systems for the production of lipids and nutraceuticals do not offer techno-economic feasibility together with energy and environmental sustainability. This review article has its main focus on the production of lipids and nutraceuticals from microalgae, covering the current strategies used for lipid production and the major high-value metabolites from microalgae and their nutraceutical importance. This review also provides insights on the future strategies for enhanced microalgal lipid production and subsequent utilization of microalgal biomass.

GRAPHICAL ABSTRACT

Integrated Approach for Carbon Sequestration and Wastewater Treatment Using Algal–Bacterial Consortia: Opportunities and Challenges

Increasing concentrations of carbon dioxide (CO2), one of the important greenhouse gases, due to combustion of fossil fuels, particularly burning coal, have become the major cause for global warming. As a consequence, many research programs on CO2 management (capture, storage, and sequestration) are being highlighted. Biological sequestration of CO2 by algae is gaining importance, as it makes use of the photosynthetic capability of these aquatic species to efficiently capture CO2 emitted from various industries and converting it into algal biomass as well as a wide range of metabolites such as polysaccharides, amino acids, fatty acids, pigments, and vitamins. In addition, their ability to thrive in rugged conditions such as seawater, contaminated lakes, and even in certain industrial wastewaters containing high organic and inorganic nutrients loads, has attracted the attention of researchers to integrate carbon capture and wastewater treatment. Algae offer a simple solution to tertiary treatments due to their nutrient removal efficiency, particularly inorganic nitrogen and phosphorus uptake. The algal–bacterial energy nexus is an important strategy capable of removing pollutants from wastewater in a synergistic manner. This review article highlights the mechanism involved in biological fixation of CO2 by microalgae, their cultivation systems, factors influencing algal cultivation in wastewater and CO2 uptake, the effect of co-cultivation of algae and bacteria in wastewater treatment systems, and challenges and opportunities.

Hydrothermal systems to obtain high value-added compounds from macroalgae for bioeconomy and biorefineries

The search of sustainable and environmentally friendly alternatives to obtain compounds for different industrial sectors has grown exponentially. Following the principles of biorefinery and circular bioeconomy, processes in which the use of natural resources such as macroalgae biomass is prioritized are required. This review focuses on a description of the relevance, application and engineering platforms of hydrothermal systems and the operational conditions depending on the target as an innovative technology and bio-based solution for macroalgae fractionation in order to recover profitable products for industries and investors. In this sense, hydrothermal treatments represent a promising alternative for obtaining different high value-added compounds from this biomass; since, the different variations in terms of operating conditions, gives great versatility to this technology compared to other types of processing, allowing it to be adapted depending on the objective, whether it is working under sub/super critical conditions, thus expanding its field of application.

Algal-based system for removal of emerging pollutants from wastewater: A review

The bioremediation of emerging pollutants in wastewater via algal biotechnology has been emerging as a cost-effective and low-energy input technological solution. However, the algal bioremediation technology is still not fully developed at a commercial level. The development of different technologies and new strategies to cater specific needs have been studied. The existence of multiple emerging pollutants and the selection of microalgal species is a major concern. The rate of algal bioremediation is influenced by various factors, including accidental contaminations and operational conditions in the pilot-scale studies. Algal-bioremediation can be combined with existing treatment technologies for efficient removal of emerging pollutants from wastewater. This review mainly focuses on algal-bioremediation systems for wastewater treatment and pollutant removal, the impact of emerging pollutants in the environment, selection of potential microalgal species, mechanisms involved, and challenges in removing emerging pollutants using algal-bioremediation systems.

Performance intensification of CO2 absorption and microalgae conversion (CAMC) hybrid system via low temperature plasma (LTP) treatment

CO₂ absorption and microalgae conversion (CAMC) hybrid system is a promising alternative for simultaneous carbon capture and utilization. It can not only overcome the challenge of high energy consumption solvent thermal regeneration in chemical CO₂ absorption, but also enhance the carbon conversion efficiency in biological conversion process. However, the discordance between CO₂ absorption and bio-conversion rate has become the key to limiting the development of CAMC system. Therefore, in this study, low temperature plasma (LTP) mutation breeding technology was used to training Chlorella strains by combining undirected mutagenesis and directional screening. Then, the mutagenic microalgae were cultivated and evaluated in CAMC system. It was found that compared with original Chlorella L166, the OD₆₈₀ of mutant strain L166-M₃ in CAMC system increased 7.8%, and the maximum specific growth rate improved 27.5%. The carbon sequestration rate of wild Chlorella L166 increased from 82.9% to 93.7% after mutation treatment, the activity of RubisCO, and the content of NADPH produced by photoreaction increased 37.2% and 17.2%. In addition, lipid production of L166-M₃ increased to 6.89 mg/L, which was 15.4% higher than original Chlorella L166. It could be observed that LTP mutation breeding could be used as a potential method for training algae species and improve the overall performance of CAMC system.

Microalgae potential in the capture of CO2 emission

In a perspective projected to reduce the atmospheric concentration of greenhouse gases, in which carbon dioxide is the master, the use of microalgae is an effective and decisive response. The review describes the bio circularity of the process of abatement of carbon dioxide through biofixation in algal biomass, highlighting the potential of its reuse in the production of high value-added products.

Role of Microalgae in Global CO2 Sequestration: Physiological Mechanism, Recent Development, Challenges, and Future Prospective

The rising concentration of global atmospheric carbon dioxide (CO2) has severely affected our planet’s homeostasis. Efforts are being made worldwide to curb carbon dioxide emissions, but there is still no strategy or technology available to date that is widely accepted. Two basic strategies are employed for reducing CO2 emissions, viz. (i) a decrease in fossil fuel use, and increased use of renewable energy sources; and (ii) carbon sequestration by various biological, chemical, or physical methods. This review has explored microalgae’s role in carbon sequestration, the physiological apparatus, with special emphasis on the carbon concentration mechanism (CCM). A CCM is a specialized mechanism of microalgae. In this process, a sub-cellular organelle known as pyrenoid, containing a high concentration of Ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), helps in the fixation of CO2. One type of carbon concentration mechanism in Chlamydomonas reinhardtii and the association of pyrenoid tubules with thylakoids membrane is represented through a typical graphical model. Various environmental factors influencing carbon sequestration in microalgae and associated techno-economic challenges are analyzed critically.

Resource recovery through bioremediation of wastewaters and waste carbon by microalgae: a circular bioeconomy approach

Microalgal biomass-based biofuels are a promising alternative to fossil fuels. Microalgal biofuels' major obstacles are the water and carbon sources for their cultivation and biomass harvest from the liquid medium. To date, an economically viable process is not available for algal based biofuels. The circular bioeconomy is an attractive concept for reuse, reduce, and recycle resources. The recovery of nutrients from waste and effluents by microalgae could significantly impact the escalating demands of energy and nutraceutical source to the growing population. Wastewaters from different sources are enriched with nutrients and carbon, and these resources can be recovered and utilized for the circular bioeconomy approach. However, the utilization of wastewaters and waste seems to be an essential strategy for mass cultivation of microalgae to minimizing freshwater consumption, carbon, nutrients cost, nitrogen, phosphorus removal, and other pollutants loads from wastewater and generating sustainable biomass for value addition for either biofuels or other chemicals. Hence, the amalgamation of wastewater treatment with the mass cultivation of microalgae improved the conventional treatment process and environmental impacts. This review provides complete information on the latest progress and developments of microalgae as potential biocatalyst for the remediation of wastewaters and waste carbon to recover resources through biomass with metabolites for various industrial applications and large-scale cultivation in wastewaters, and future perspectives are discussed.

Carbon Farming: Prospects and Challenges

Carbon farming is a capable strategy for more sustainable production of food and other related products. It seeks to produce a diverse array of natural farming methods and marketable products simultaneously. According to the food and agriculture organization (FAO), agriculture, forestry, and other land-use practices account for 24% of global greenhouse gas (GHG) emissions and total global livestock emissions of 7.1 gigatons of CO2-equivalent per year, representing 14.5% of total anthropogenic GHG emissions. For example, an agroforestry system that deliberately integrates trees and crops with livestock in agricultural production could potentially increase carbon sequestration and decrease GHG emissions from terrestrial ecosystems, thus helping to mitigate global climatic change. Also, agroforestry is capable of generating huge amounts of bio-mass and is believed to be particularly suitable for replenishing soil organic carbon (SOC). SOC is a crucial indicator for soil fertility since the change in SOC can explain whether the land use pattern degrades or improves soil fertility. Moreover, SOC found in soil in the form of soil organic matter (SOM) helps to improve soil health either directly or indirectly. Thus, efforts should be made to convince farmers to increase their resource-use efficiency and soil conserving ability to get maximum benefits from agriculture. Therefore, this review aimed at clarification about carbon farming, modifications in carbon cycle and carbon sequestration during agricultural development, and benefits of agroforestry.

Role of intertidal microbial communities in carbon dioxide sequestration and pollutant removal: A review

Intertidal microbial communities occur as biofilms or microphytobenthos (MPB) which are sediment-attached assemblages of bacteria, protozoa, fungi, algae, diatoms embedded in extracellular polymeric substances. Despite their global occurrence, they have not been reviewed in light of their structural and functional characteristics. This paper reviews the importance of such microbial communities and their importance in carbon dioxide sequestration as well as pollutant bioremediation. Global annual benthic microalgal productivity was 500 million tons of carbon, 50% of which contributed towards the autochthonous carbon fixation in the estuaries. Primary production by MPB was 27-234 gCm^-2y^-1 in the estuaries of Asia, Europe and the United States. Mechanisms of heavy metal removal remain to be tested in intertidal communities. Cyanobacteria facilitate hydrocarbon degradation in intertidal biofilms and microbial mats by supporting the associated sulfate-reducing bacteria and aerobic heterotrophs. Physiological cooperation between the microorganisms in intertidal communities imparts enhanced ability to utilize polycyclic aromatic hydrocarbon pollutants by these microorganisms than mono-species communities. Future research may be focused on biochemical characteristics of intertidal mats and biofilms, pollutant-microbial interactions and ecosystem influences.

Microalgal growth, nitrogen uptake and storage, and dissolved oxygen production in a polyculture based-open pond fed with municipal wastewater in northern Sweden

Microalgal-based wastewater treatment and CO₂ sequestration from flue gases with subsequent biomass production represent a low-cost, eco-friendly, and effective procedure of removing nutrients and other pollutants from wastewater and assists in the decrease of greenhouse gas emissions. Thus, it supports a circular economy model. This is based on the ability of microalgae to utilise inorganic nutrients, mainly nitrogen and phosphorous, as well as organic and inorganic carbon, for their growth, and simultaneously reduce these substances in the water. However, the production of microalgae biomass under outdoor cultivation is dependent on several abiotic and biotic factors, which impact its profitability and sustainability. Thus, this study's goal was to evaluate the factors affecting the production of microalgae biomass on pilot-scale open raceway ponds under Northern Sweden's summer conditions with the help of a mathematical model. For this purpose, a microalgae consortium and a monoculture of Chlorella vulgaris were used to inoculate outdoor open raceway ponds. In line with the literature, higher biomass concentrations and nutrient removals were observed in ponds inoculated with the microalgae consortium. Our model, based on Droop's concept of macronutrient quotas inside the cell, corresponded well to the experimental data and, thus, can successfully be applied to predict biomass production, nitrogen uptake and storage, and dissolved oxygen production in microalgae consortia.

Dielectric Characterization and Multistage Separation of Various Cells via Dielectrophoresis in a Bipolar Electrode Arrayed Device

Isolation of microalgal cells is as an indispensable part of producing biofuels for energy security and detecting toxic contaminants for marine routine monitoring. Microalgae live together with various microalgae naturally, and abundant samples need to be tackled in practical applications. Therefore, effective separation technologies need to be developed urgently to achieve high-throughput separation of various microalgae. Herein, we develop a reliable device to characterize the dielectric response of microalgae and sequentially separate various microalgae utilizing dielectrophoretic force in a bipolar electrode (BPE) arrayed device. First, by investigating the array width extension (AWE) effect on the electric- and flow-field distributions, we explore consequences of incidental electrohydrodynamic mechanisms and axial flow rate on the separation. Second, based on device performance on sample characterizations, we demonstrate this technology by separating microparticles in three- and five-channel devices. Third, we discriminate dead and live cells to explore its capability using the cell viability test and illustrate the AWE influence on the separation. Fourth, we characterize dielectric responses of different microalgae and separate C. vulgaris and Oocystis sp. Finally, we extended BPEs in length and developed an arrayed device for sequential separation of various microalgae, and this platform is successfully engineered in high-throughput isolation of C. vulgaris from complex samples. This technology presents good potential in addressing depleting fossil fuel and burgeoning environmental concerns due to its performance in the separation of microalgal strains from complex samples.

Towards sustainable agriculture with carbon sequestration, and greenhouse gas mitigation using algal biochar

With the increase in the world's population, demand for food and other products is continuously rising. This has put a lot of pressure on the agricultural sector. To fulfill these demands, the utilization of chemical fertilizers and pesticides has also increased. Consequently, to overcome the adverse effects of agrochemicals on our environment and health, there has been a shift towards organic fertilizers or other substitutes, which are ecofriendly and help to maintain a sustainable environment. Microalgae have a very high potential of carbon dioxide (CO₂) capturing and thus, help in mitigating the greenhouse effect. It is the most productive biological system for generating biomass. The high growth rate and higher photosynthetic efficiency of the algal species compared to the terrestrial plants make them a wonderful alternative towards a sustainable environment. Moreover, they could be cultivated in photobioreactors or open ponds, which in turn reduce the demand for arable land. Biochar derived from algae is high in nutrients and exhibits the property of ion exchange. Therefore, it can be utilized for sustainable agriculture by partial substituting the chemical fertilizers that degrade the fertility of the soil in the long run. This review provides a detailed insight on the properties of algal biochar as a potential fertilizer for sustainable agriculture. Application of algal biochar in bio-refinery and its economic aspects, challenges faced and future perspective are also discusses in this study.

Recent Advances in Carbon Dioxide Conversion: A Circular Bioeconomy Perspective

Managing the concentration of atmospheric CO2 requires a multifaceted engineering strategy, which remains a highly challenging task. Reducing atmospheric CO2 (CO2R) by converting it to value-added chemicals in a carbon neutral footprint manner must be the ultimate goal. The latest progress in CO2R through either abiotic (artificial catalysts) or biotic (natural enzymes) processes is reviewed herein. Abiotic CO2R can be conducted in the aqueous phase that usually leads to the formation of a mixture of CO, formic acid, and hydrogen. By contrast, a wide spectrum of hydrocarbon species is often observed by abiotic CO2R in the gaseous phase. On the other hand, biotic CO2R is often conducted in the aqueous phase and a wide spectrum of value-added chemicals are obtained. Key to the success of the abiotic process is understanding the surface chemistry of catalysts, which significantly governs the reactivity and selectivity of CO2R. However, in biotic CO2R, operation conditions and reactor design are crucial to reaching a neutral carbon footprint. Future research needs to look toward neutral or even negative carbon footprint CO2R processes. Having a deep insight into the scientific and technological aspect of both abiotic and biotic CO2R would advance in designing efficient catalysts and microalgae farming systems. Integrating the abiotic and biotic CO2R such as microbial fuel cells further diversifies the spectrum of CO2R.

Facile synthesis and characterization of microporous-structured activated carbon from agro waste materials and its application for CO2 capture

Biomass-derived activated carbon was prepared from the agro waste materials, (wild sugarcane (WS) and saw dust (SD)) by chemical activation using phosphoric acid. The crystallinity, morphology, functional groups of the synthesized activated carbon were investigated. The effects of contact time (10-60 min), mass of adsorbent (0.05-0.2 g) and concentrations of CO2 (1 × 10-4 to 10 × 10-4 M) were analysed and the optimum adsorption conditions were found. Freundlich, Langmuir, Temkin, Dubinin-Radushkevich and Sips isotherm were used to analyse the adsorption data. The adsorption process was fitted with the Freundlich model. Adsorption capacity of agro waste-based sorbent was 5.225 × 10-3 mol/g. Thermodynamic parameters, such as ΔH0, ΔG0, ΔS0 , were calculated and it was found that the present system was a spontaneous process. From the kinetic studies, it was inferred that the Pseudo-second-order kinetics describes the kinetics of CO2 on AC-WSSD with an equilibrium point attained at 50 minutes with a high R2 value of 0.9602. The Brunauer Emmett Teller (BET) surface area of 1220 m2/g and an iodine value of 1360 m2/g were better indications for adsorption process. The interaction between CO2 and functional groups on the surface of the activated carbon was confirmed by FTIR. Desorption studies were carried out for three cycles with an efficiency of 93.2%.

Greenhouse gases emission control in WWTS via potential operational strategies: A critical review

Greenhouse gases (GHGs; particularly, CO₂, CH₄, and N₂O) emission from wastewater treatment systems (WWTS) is one of the inevitable concerns for sustainable development. This indicator is directly linked with the carbon footprint and potential impacts of WWTS on climate change. In this view, various modeling, design, and operational tools have been introduced to mitigate the WWTS associated GHGs, at regional and global scales. In this study, authors have critically reviewed the selected potential operational control strategies for GHGs emission, particularly emitted from the operational stages of biological WWTS. The investigated operational control strategies and/or treatment configurations included intermittent aeration, varying dissolved oxygen, enhanced sludge retention time, coupled aerobic-anoxic nitrous decomposition operation, and microalgae integrated treatment process. Based on this analysis and considering the trade-off between treatment performance of WWTS and GHGs control, an integrated framework is also proposed for existing and upcoming WWTS. The findings of this study and proposed framework will play an instrumental role in mitigating the GHGs at various operational stages of WWTS. Future research works in this direction can lead to a better understanding of investigated operational GHGs emission control strategies in WWTS.

Production of Microalgal Biomass in Photobioreactors as Feedstock for Bioenergy and Other Uses: A Techno-Economic Study of Harvesting Stage

The cultivation of microalgae has become a viable option to mitigate increase in CO2 in the atmosphere generated by industrial activities since they can capture CO2 as a carbon source for growth. Besides, they produce significant amounts of oils, carbohydrates, proteins, and other compounds of economic interest. There are several investigations related to the process, however, there is still no optimal scenario, since may depend on the final use of the biomass. The objective of this work was to develop a techno-economic evaluation of various technologies in harvesting and drying stages. The techno-economic estimation of these technologies provides a variety of production scenarios. Photobioreactors were used considering 1 ha as a cultivation area and a biomass production of 22.66 g/m2/day and a CO2 capture of 148.4 tons/ha/year was estimated. The production scenarios considered in this study have high energy demand and high operating costs (12.09–12.51 kWh/kg and US $210.05–214.59/kg). These results are mainly a consequence of the use of tubular photobioreactors as a biomass culture system. However, the use of photobioreactors in the production of microalgal biomass allows it to be obtained in optimal conditions for its use in the food or pharmaceutical industry.

Capture and Reuse of Carbon Dioxide (CO2) for a Plastics Circular Economy: A Review

Plastic production has been increasing at enormous rates. Particularly, the socioenvironmental problems resulting from the linear economy model have been widely discussed, especially regarding plastic pieces intended for single use and disposed improperly in the environment. Nonetheless, greenhouse gas emissions caused by inappropriate disposal or recycling and by the many production stages have not been discussed thoroughly. Regarding the manufacturing processes, carbon dioxide is produced mainly through heating of process streams and intrinsic chemical transformations, explaining why first-generation petrochemical industries are among the top five most greenhouse gas (GHG)-polluting businesses. Consequently, the plastics market must pursue full integration with the circular economy approach, promoting the simultaneous recycling of plastic wastes and sequestration and reuse of CO2 through carbon capture and utilization (CCU) strategies, which can be employed for the manufacture of olefins (among other process streams) and reduction of fossil-fuel demands and environmental impacts. Considering the previous remarks, the present manuscript’s purpose is to provide a review regarding CO2 emissions, capture, and utilization in the plastics industry. A detailed bibliometric review of both the scientific and the patent literature available is presented, including the description of key players and critical discussions and suggestions about the main technologies. As shown throughout the text, the number of documents has grown steadily, illustrating the increasing importance of CCU strategies in the field of plastics manufacture.

Algae utilization and its role in the development of green cities

With the rapid urbanisation happening around the world followed by the massive demand for clean energy resources, green cities play a pivotal role in building a sustainable future for the people. The continuing depletion of natural resources has led to the development of renewable energy with algae as the promising source. The high growth rate of microalgae and their strong bio-fixation ability to convert CO₂ into O₂ have been gaining attention globally and intensive research has been conducted regarding the microalgae benefits. The focus on potential of microalgae in contributing to the development of green cities is rising. The advantage of microalgae is their ability to gather energy from sunlight and carbon dioxide, followed by transforming the nutrients into biomass and oxygen. This leads to the creation of green cities through algae cultivation as waste and renewable materials can be put to good use. The challenges that arise when using algae and the future prospect in terms of SDGs and economy will also be covered in this review. The future of green cities can be enhanced with the adaptation of algae as the source of renewable plants to create a better outlook of an algae green city.

Microalgae Cultivation in Palm Oil Mill Effluent (POME) Treatment and Biofuel Production

Palm oil mill effluent (POME) is the wastewater produced during the palm oil sterilization process, which contains substantial amounts of nutrients and phosphorous that are harmful to the environment. High BOD and COD of POME are as high as 100,000 mg/L, which endanger the environment. Effective pre-treatment of POME is required before disposal. As microalgae have the ability of biosorption on nutrients and phosphorous to perform photosynthesis, they can be utilized as a sustainable POME treatment operation, which contributes to effective biofuel production. Microalgae species C. pyrenoidosa has shown to achieve 68% lipid production along with 71% nutrient reduction in POME. In this study, a brief discussion about the impacts of POME that will affect the environment is presented. Additionally, the potential of microalgae in treating POME is evaluated along with its benefits. Furthermore, the condition of microalgae growth in the POME is also assessed to study the suitable condition for microalgae to be cultivated in. Moreover, experimental studies on characteristics and performance of microalgae are being evaluated for their feasibility. One of the profitable applications of POME treatment using microalgae is biofuel production, which will be discussed in this review. However, with the advantages brought from cultivating microalgae in POME, there are also some concerns, as microalgae will cause pollution if they are not handled well, as discussed in the last section of this paper.

Investigating algae for CO2 capture and accumulation and simultaneous production of biomass for biodiesel production

Carbon capture and sequestration technologies are used to reduce carbon emissions. Membranes, solvents, and adsorbents are the three major methods of CO₂ capture. One of the promising methods is the use of algae to absorb CO₂ from flue gases and convert it into biomass. Algae have great potential as renewable fuel sources and CO₂ capture using photosynthesis for carbon fixation has also attracted much attention. This paper presents an extensive and in-depth report on the utilization of algae for carbon capture and accumulation. This is done in conjunction with cultivating the algae for the production of biomass for biodiesel production. Different systems are investigated for algae cultivation as well as carbon capture to effectively mitigate carbon emissions. The performance and productivity of these biosystems depend on various conditions including algae type, light sources, nutrients, pH, temperature, and mass transfer. Macroalgae and microalgae species were explored to determine their suitability for carbon capture and sequestration, along with the production of biodiesel. The steps for producing biodiesel were comprehensively reviewed, which are harvesting, dehydrating, oil extraction, oil refining, and transesterification. This technology combines active carbon capture with the potential of biodiesel production.

Current developments and challenges of green technologies for the valorization of liquid, solid, and gaseous wastes from sugarcane ethanol production

The sugarcane industry is one of the largest in the world and processes huge volumes of biomass, especially for ethanol and sugar production. These processes also generate several environmentally harmful solid, liquid, and gaseous wastes. Part of these wastes is reused, but with low-added value technologies, while a large unused fraction continues to impact the environment. In this review, the classic waste reuse routes are outlined, and promising green and circular technologies that can positively impact this sector are discussed. To remain competitive and reduce its environmental impact, the sugarcane industry must embrace technologies for bagasse fractionation and pyrolysis, microalgae cultivation for both CO₂ recovery and vinasse treatment, CO₂ chemical fixation, energy generation through the anaerobic digestion of vinasse, and genetically improved fermentation yeast strains. Considering the technological maturity, the anaerobic digestion of vinasse emerges as an important solution in the short term. However, the greatest environmental opportunity is to use the pure CO₂ from fermentation. The other opportunities still require continued research to reach technological maturity. Intensifying the processes, the exploration of driving-change technologies, and the integration of wastes through biorefinery processes can lead to a more sustainable sugarcane processing industry.