Abstract
Over the last decades, microalgal biomass has gained a significant role in the development of different high-end (nutraceuticals, colorants, food supplements, and pharmaceuticals) and low-end products (biodiesel, bioethanol, and biogas) due to its rapid growth and high carbon-fixing efficiency. Therefore, microalgae are considered a useful and sustainable resource to attain energy security while reducing our current reliance on fossil fuels. From the technologies available for obtaining biofuels using microalgae biomass, thermochemical processes (pyrolysis, Hydrothermal Liquefaction (HTL), gasification) have proven to be processed with higher viability, because they use all biomass. However, due to the complex structure of the biomass (lipids, carbohydrates, and proteins), the obtained biofuels from direct thermochemical conversion have large amounts of heteroatoms (oxygen, nitrogen, and sulfur). As a solution, catalyst-based processes have emerged as a sustainable solution for the increase in biocrude production. This paper’s objective is to present a comprehensive review of recent developments on the catalyst-mediated conversion of algal biomass. Special attention will be given to operating conditions, strains evaluated, and challenges for the optimal yield of algal-based biofuels through pyrolysis and HTL.
Highlights
Fossil fuels have been a critical commodity for the economic and social development of the modern world
The biomass is decomposed under oxygen/air deficient conditions to produce Bio-oil, Biochar, and syngas, which primarily consists of carbon monoxide (CO) and carbon dioxide (CO2 ) [12], the quantity and quality of the final product depends upon the process, reaction temperature, heating rate, and oxygen supply [13]
Other zeolite-based catalysts such as H-ZSM-5 and Ce/H-ZSM-5 have been reported for the conversion of C. pyrenoidosa biomass [171], and their results highlight the efficiency of zeolite-based catalysts, due to a raise in the yield of bio-oil from 32% to
Summary
Fossil fuels have been a critical commodity for the economic and social development of the modern world. The algal biomass produced under specific conditions can be transformed into energy by applying thermochemical and biochemical methods Biofuel such as Bio-oil, biochar, synthesis gas (syngas), and heat are obtained through thermochemical conversion. Biogas is the main product of AD and is considered one of the most promising biofuels that can address rising concerns about fossil fuels [11] Another alternative is the application of catalytic-based processes such as Hydrothermal. The biomass is decomposed under oxygen/air deficient conditions to produce Bio-oil, Biochar (specially on HTL and pyrolysis process), and syngas (especially on gasification process), which primarily consists of carbon monoxide (CO) and carbon dioxide (CO2 ) [12], the quantity and quality of the final product depends upon the process, reaction temperature, heating rate, and oxygen supply [13]. Special attention will be given to operating conditions, strains evaluated, and challenges for the optimal yield of algal-based biofuels through pyrolysis and HTL
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