Feasibility of Utilizing Wastewaters for Large-Scale Microalgal Cultivation and Biofuel Productions Using Hydrothermal Liquefaction Technique: A Comprehensive Review

Abstract

The two major bottlenecks faced during microalgal biofuel production are, (a) higher medium cost for algal cultivation, and (b) cost-intensive and time consuming oil extraction techniques. In an effort to address these issues in the large scale set-ups, this comprehensive review article has been systematically designed and drafted to critically analyze the recent scientific reports that demonstrate the feasibility of microalgae cultivation using wastewaters in outdoor raceway ponds in the first part of the manuscript. The second part describes the possibility of bio-crude oil production directly from wet algal biomass, bypassing the energy intensive and time consuming processes like dewatering, drying and solvents utilization for biodiesel production. It is already known that microalgal drying can alone account for ∼30% of the total production costs of algal biomass to biodiesel. Therefore, this article focuses on bio-crude oil production using the hydrothermal liquefaction (HTL) process that converts the wet microalgal biomass directly to bio-crude in a rapid time period. The main product of the process, i.e., bio-crude oil comprises of C16-C20 hydrocarbons with a reported yield of 50–65 (wt%). Besides elucidating the unique advantages of the HTL technique for the large scale biomass processing, this review article also highlights the major challenges of HTL process such as update, and purification of HTL derived bio-crude oil with special emphasis on deoxygenation, and denitrogenation problems. This state of art review article is a pragmatic analysis of several published reports related to algal crude-oil production using HTL technique and a guide towards a new approach through collaboration of industrial wastewater bioremediation with rapid one-step bio-crude oil production from chlorophycean microalgae.

Integrated Waste Biorefineries: Achieving Sustainable Development Goals, 2nd edition

“…Biomass-based biorefineries have recently been considered as a potential strategy to mitigate environmental pollution and climate change by ensuring sustainable waste management (Venkata Hao et al, 2021;Wahab et al, 2022). Bio-based energy production is one sustainable alternative (Amulya et al, 2020;Kokkinos et al, 2021;Kopperi et al, 2021), accounting for 9-10% of the global energy supply (Bagchi et al, 2021). Using nature-inspired processes to design an efficient biorefinery system to produce environmentally-friendly biofuels and chemicals can help to build sustainable bio-refineries and carbon-neutral bioeconomies (Katakojwala and Venkata Mohan, 2021).…”

Optimization of the glycerol production fromDunaliella tertiolectaandDunaliellaisolates

“…Compared to terrestrial plants, microalgae grow up to ten times faster [32, 33] and photosynthesize about ten times as efficiently as plants do, owing to their energy efficient photosynthetic apparatus [34, 35]. Moreover, it is feasible to cultivate microalgae on wasteland using saline or waste water [36, 37] with the result that they do not compete with agricultural food production. These advantages make microalgae a suitable biotechnological tool to efficiently fix CO 2 and convert it into sustainable high-value products [38, 39].…”

A Low-Cost Fertilizer Medium Supplemented with Urea for the Lutein Production of Chlorella sp. and the Ability of the Lutein to Protect Cells against Blue Light Irradiation

“…Circular bioeconomy of microalgae-based CO 2 biofixation and biorefinery can be analyzed through technical-economic assessment (TEA) and life-cycle assessment (LCA) [4][5][6]. However, one of the bottlenecks faced by microalgae-based CO 2 biofixation technology is the high cost of microalgal culture medium; the components in the culture medium are among the key factors that greatly affect the growth of microalgae and the production of various components [7,8]. Nutrient requirements in large-scale production can comprise up to 50% of the total cost of biomass production, and high-cost media limit the development of back-end products such as biofuels [9][10][11].…”