The depletion of fossil fuels and the search for novel sustainable energy sources are challenges faced by countries throughout the world over the past few decades. Microalgae have received considerable interest as new oil sources for biofuel production. However, the enhancement of the lipid content in microalgae strains without decreasing the growth rate is a prerequisite for improving the economic viability of microalgae-derived biofuel production. The implementation of an appropriate cultivation strategy can increase both lipid accumulation and biomass production. One of the most-often suggested strategies is the cultivation of microalgae through two-stage cultivation strategy (TSCS). This paper aims to recapitulate the findings of recent studies and achievements in improving the lipid productivity and economic feasibility of TSCS. This article starts by highlighting different types of TSCS based on various stimuli. Afterwards, the most noteworthy culture parameters, including growth stage and initial cell density, are addressed. The existing experimental results show that lipid productivity can be enhanced by optimizing stress factor(s) and engineering processes. Moreover, it is reported that the modification or elimination of the pre-harvesting phase (which can be done by upgrading technical aspects and/or via stress induction strategies) can promote the economic feasibility of TSCSs.<

Two-stage cultivation strategy for simultaneous increases in growth rate and lipid content of microalgae: A review

The fossil fuel issues due to toxic carbon dioxide emissions and climate change have a direct link with the particulate matter that has caused severe threat to the environment. The bio-based products such as biodiesel and bio-compressed natural gas (Bio-CNG) can be less expensive and adaptable. Biofuels are increasingly being used in transportation, heat, and power development requiring the need for renewable sources of energy. This review highlights the use of dreck organic matters from aquatic environment and soil supplies for renewable energy production for human requirements, sustaining a clean and healthy environment. Dreck can be harnessed to manufacture bioenergy that would help to mitigate greenhouse gases and preserve the environment. Methane, hydrogen, ethanol, bioelectricity, algal diesel, and butanol, or other forms of fuels provide a renewable supply of bioenergy, which can be created by the biological systems. The waste-to-energy methodologies (thermal plus biochemical) for energy production via agro-residues are covered. The key focus of this study is the recent advances in the area of 'synchronous waste mitigation with energy development' techniques. This review addresses the significance of organic substances for the production of clean and renewable energy, including alternate solutions for non-renewable fuels. The needs for appropriate and renewable alternatives for fossil fuels are discussed.

Recent advances and viability in biofuel production

Algal biodiesel production with engineered biochar as a heterogeneous solid acid catalyst.

The increasing world population generates huge amounts of wastewater as well as large energy demand. Additionally, fossil fuel’s combustion for energy production causes the emission of greenhouse gases (GHG) and other pollutants. Therefore, there is a strong need to find alternative green approaches for wastewater treatment and energy production. Microalgae biorefineries could represent an effective strategy to mitigate the above problems. Microalgae biorefineries are a sustainable alternative to conventional wastewater treatment processes, as they potentially allow wastewater to be treated at lower costs and with lower energy consumption. Furthermore, they provide an effective means to recover valuable compounds for biofuel production or other applications. This review focuses on the current scenario and future prospects of microalgae biorefineries aimed at combining wastewater treatment with biofuel production. First, the different microalgal cultivation systems are examined, and their main characteristics and limitations are discussed. Then, the technologies available for converting the biomass produced during wastewater treatment into biofuel are critically analyzed. Finally, current challenges and research directions for biofuel production and wastewater treatment through this approach are outlined.

https://www.mdpi.com/1996-1073/14/8/2282/pdf

Integrated Approach for Wastewater Treatment and Biofuel Production in Microalgae Biorefineries

A conceptual review on microalgae biorefinery through thermochemical and biological pathways: Bio-circular approach on carbon capture and wastewater treatment

Anwesha Acharya

Papers

Bioprocess engineering principles of microalgal cultivation for sustainable biofuel production