A comprehensive review on cultivation and harvesting of microalgae for biodiesel production: Environmental pollution control and future directions.

Algae as potential feedstock for the production of biofuels and value-added products: Opportunities and challenges

Derivation of biofuel from microalgae biomass has been widely researched in the past few decades. Microalgae is capable of producing 58,700  litres oil per hectare that can generate 121,104  litres biodiesel per hectare, which seemingly a promising transition over conventional fossil fuels. Nevertheless, economic sustainability of commercial scale production of microalgae biomass is still in shadows of doubt, especially the cultivation and harvesting process. Apparently, the microalgae cultivation system has evolved from traditional open pond to various modern photobioreactor (PBR) designs. However, with regards to tubular and flat panel PBRs as the most ubiquitous systems for biofuel production at commercial level, extensive discussion on reactor configurations and design betterment was presented in this review, along with precise technical comparison on cost and energy requirements for the cultivation systems. This review intended to serve as guideline for long term adoption of these well-established cultivation technologies in biofuel plants given the numerous economic benefits. Besides that, in attempt to lower the harvesting cost, potential use of various waste biomass as bioflocculants to recover microalgae biomass was introduced in this review. This article also deliberates direction on potential policy interventions to produce microalgae biofuel in a more sustainable and cost-effective manners in near future.

Insights into the microalgae cultivation technology and harvesting process for biofuel production: A review

Microalgae have emerged as a renewable and sustainable candidate for bioenergy production coupled with pollutant removal from wastewater. However, costly biomass harvesting, insufficient biomass productivity, and energy-intensive extraction methods are major bottlenecks restricting their large-scale development. To break through such limitations, researchers have focused on the technologies towards consolidating microalgal-bacterial consortia, which exhibit numerous advantages related to economy, energy, and environment, due to the cooperative interactions between microalgae and bacteria. This paper recapitulates the most recent work on microalgal-bacterial interaction mechanisms, and describes the diverse biotechnological applications of microalgal-bacterial consortia. Based on this review, the interaction mechanisms cover substrate exchange, cell-to-cell signaling, and horizontal gene transfer. Nutrient availability, growth phase, and cultivation conditions are major factors affecting their interactions. In terms of wastewater treatment, attached microalgal-bacterial consortia are economically feasible and technically superior compared to suspended microalgal-bacterial consortia. Appropriate carrier, bioreactor type, operation mode, operational factor, and further perspectives for engineering attached microalgal-bacterial consortia are critically assessed. Bacteria play an important role in promoting microalgal growth, enhancing bio-flocculation and facilitating cell wall disruption, and thus expanding the application potential of microalgal biofuel production. The current state of other promising biotechnological applications of microalgal-bacterial consortia (particularly mitigation of CO2 emissions, microalgal bloom control, and electricity generation) and the appropriate strategies to enhance their practical applications are discussed. The major challenges to scale up microalgal-bacterial consortia and corresponding recommendations for further research are also addressed.

Microalgal-bacterial consortia: From interspecies interactions to biotechnological applications

Biologically-mediated carbon capture and utilization by microalgae towards sustainable CO2 biofixation and biomass valorization – A review

The concern regarding alternate sources of energy is mounting day-by-day due to the effect of pollution that is damaging the environment. Algae are a diverse group of aquatic organisms have an efficiency and ability in mitigating carbon dioxide emissions and produce oil with a high productivity which has a lot of potential applications in producing biofuel, otherwise known as the third-generation biofuel. These third generation biofuels are the best alternative to the present situation since they have the perspective to eliminate most of the ecological problems created by the use of conventional fossil fuels. These organisms are responsible for closely 50% of the photosynthesis process taking place on the planet and are distributed predominantly in many of the aquatic systems. The huge interest in utilizing these organisms as a potential source of energy lies in converting the primary as well as secondary metabolites into useful products. Algae are considered to be the most prominent resource for the upcoming generations as the most suitable and sustainable feedstock. The key process limitations in microalgal biofuel production are inexpensive and effective harvesting of biomass and extraction of lipids. The major objective of this article is to provide a comprehensive review on various methods of both biomass harvesting and lipid extraction from microalgae available, so far, besides to discuss their advantages and disadvantages. This article also deals with various conditions that are favourable for lipid accumulation as well as the yield from different species.

Tirumala Vasu Aradhyula

Papers

Production of biofuels from microalgae - A review on cultivation, harvesting, lipid extraction, and numerous applications of microalgae