Introduction Biofuel production from renewable resource has been extensively paid attention as a sustainable alternative for fossil fuel. As the feed of third-generation biofuels, MICROALGAE can produce variety of lipids, proteins, and carbohydrates in large quantities and in a relatively short time. Regarding the compatibility of these microorganisms with culture diffrent conditions and independence from the seasons of the year, the rapid growth rate, absorbing carbon dioxide and improving air quality, renewablity, non-competing with food supplies, the existence of large quantities of lipid and carbohydrate inside their cells, and abillity of biofuels production, MICROALGAE are known as one of the most suitable options for the biofuels production. Biofuel production from MICROALGAE consists of several stages, including cultivation, harvesting, drying, cell disruption, extraction (lipids or carbohydrates), and the production of biofuels. Conclusion In the present study, by reviewing each stage of the biofuels production from MICROALGAE, its importance and application for bioenergy production is discussed. Algal biofuel is not yet competitive with fossil fuels due to its high costs. Researchers are trying to produce economic algal biofuel by improving the growth of MICROALGAE and enriching their reserves of oil and carbohydrates, creating genetic changes, improving the design of photobioreactros, developing harvesting and drying methods, improving methods of extracting lipid and carbohydrate, and producing valuable products.

Preparation of MICROALGAE to produce biofuel involves three stages: cultivation, dewatering and oil extraction. Efficient dewatering of MICROALGAE is the main challenge in industrial scale. The high cost of MICROALGAE production is due to the lack of suitable method for harvesting. This paper aims to describe and compare the different MICROALGAE harvesting methods. As a matter of fact, these methods are divided into three categories which are described as chemical, mechanical and electrical methods. The chemical method consists of coagulation and flocculation steps but none of these steps are economical. Centrifuging is a common method for mechanical harvesting. Relatively this method has high efficiency but it is not cost beneficial because of high energy consumption. Among the electrical methods, electrocoagulation is a new method for MICROALGAE harvesting which offers higher efficiency and demands lower energy than other methods.

Biofuels are the up and coming alternative to exhaustible, inenvironmentally and unsafe fossil fuels. MICROALGAE as a source of biofuels have been widely studied for biodiesel/biogas/biohydrogen/biochar/bioelectricity production and has been gathering much contemplation right away. Increasing in energy demand and in greenhouse gas emission makes it important to develop alternative energy carriers that are renewable, clean and environmentally friendly. The use of arable land for biofuels in some cases has been associated with food insecurities and increased greenhouse gases caused by indirect land use change effects. MICROALGAE can grow on land not suitable for agriculture and would alleviate these concerns. The high lipid and mineral contents of MICROALGAE render it beneficial for the production of biofuels and value-added products. On the other hand, result in to the reducing pollution and protecting the environment, because as a result of generating electricity in fuel cells or mechanical force in blast engines, the only output is water vapor. This review focuses on the current scenario and future prospects of MICROALGAE aimed at biofuel production and the technologies available for converting the biomass produced into biofuel are analyzed. The goal of this work was to give a comprehensive review on biofuel production from MICROALGAE biomass.

In the present study, the optimization of im-mobilization structures along with Calothrix sp. and the determination of heavy metals absorption rate have been investigated. Polymers in combination with salts were performed in alginate in order to study the stability of formed structures in cross linking agents. Beads with stable structure in synthesized heavy metal solution inoculated and the adsorption percentage has been recorded. Results showed that the most stable beads were formed in 2 and 3% alginate along with CaCO3 application beside BaCl2 as solidified solution. Reduction of heavy metal in these structures had the most percentage and it was observed that if the incubation time of beads in solidified solution decreased, the percentage of heavy metal reduction would increase to 86%. Although alginate beads showed the highest absorption rate of heavy metal, the presence of Calothrix sp. in all treatments occasionally increased heavy metal absorption up to 15%.