Abstract
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.
Highlights
Global population growth is increasing the demand for food, fiber, forage, and renewable biomass resources for energy, biofuels, and chemical products [1,2]
Environmental pollution leads to global warming, i.e., via the emission of greenhouse gases (GHGs), which consist of approximately 72% carbon dioxide (CO2 ), 19% methane (CH4 ), 6% nitrous oxide and 3% fluorinated gases
The light source for the autotrophic cultivation of Chlorella vulgaris was investigated, and the results showed that red light-emitting diode (LED) light (630–665 nm) resulted in small cells with active divisions, while blue light (430–465 nm) LED illumination led to a significant increase in cell size [100]
Summary
Global population growth is increasing the demand for food, fiber, forage, and renewable biomass resources for energy, biofuels, and chemical products [1,2]. 2 biofixation, involves absorbing and utilizing CO2 by phototions lead to global warming and climate change, which are believed to aggravate regional synthesis inand autotrophic organisms or plants. The produced microalgal biomass approximately 50% carbon by dry microalgal cells because of the estimated can be utilized toHproduce lipids (oil) and carbohydrates as a source of chemical precursors. The produced microalgal biomass canreducto obtain the wastewater treatment by chemical oxygen demand (COD). Be utilized to produce lipids (oil) and carbohydrates as a source of chemical precursors tion, and the resulting microalgal biomass, to be a good feedstock as biofuels, such and biofuels [25,26,27,28]. The maximum biomass production and lipid yield of obtain the wastewater treatment by chemical oxygen demand (COD) reducChlorella sp. Microalgae biological fixation techis beneficial reducing carbon but how toeconomic achieve economic and envibeneficial atnology reducing carbonat emissions, butemissions, how to achieve and environmental ronmental time—is a considerable sustainability—at thesustainability—at same time—isthe a same considerable challenge. challenge
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