Abstract
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.
Highlights
The Earth’s average surface temperature has increased about 1.1 ◦ C since the late nineteenth century due to increased carbon dioxide (CO2 ) emissions into the atmosphere, largely by the anthropogenic activities
Statistics show that combustion of fossil fuels for generation of power contributes about one-third of total CO2 emissions [2], resulting in an increase in CO2 concentration in the atmosphere from 280 ppm to 400 ppm by volume, the highest CO2 level ever recorded over the last century, leading to global climate change and consequent biological extinctions [3]
The pre-treatment using biological aerated filter (BAF) coupled with nitrobacteria rapidly nitrified the ammonia nitrogen in digestate and improved the light transmittance, indicating that the ammonia nitrogen is almost completely converted into nitrate nitrogen, resulting in elimination of ammonia inhibition for C. pyrenoidosa
Summary
The Earth’s average surface temperature has increased about 1.1 ◦ C since the late nineteenth century due to increased carbon dioxide (CO2 ) emissions into the atmosphere, largely by the anthropogenic activities. Statistics show that combustion of fossil fuels for generation of power contributes about one-third of total CO2 emissions [2], resulting in an increase in CO2 concentration in the atmosphere from 280 ppm to 400 ppm by volume, the highest CO2 level ever recorded over the last century, leading to global climate change and consequent biological extinctions [3]. Adoption of post-treatment process such as carbon-capture and storage (CCS) technology. In this regard, much research and new technologies have highlighted CO2 management via capture, storage and sequestration. CCS technology can be managed by a number of physical methods such as using membranes, different adsorbents, and cryogenic separation; geological sequestration in depleted gas and oil reservoirs; oceanographic sequestration in deep aquifers; chemical reaction-based approaches at high temperatures, including thermo-chemical, photo-chemical, bio-photochemical, electro-chemical, electrophotochemical, radio-chemical, and biochemical conversion methods; and CO2 fixation by biological methods. The importance of microalgae in CO2 sequestration, development of viable technology for their cultivation and integration with wastewater treatment facilities, factors influencing their cultivation and CO2 uptake, and prospects and challenges associated with technology development are discussed
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