Microalgae dewatering is a major obstruction to industrial-scale processing of microalgae for biofuel prodn. The dil. nature of harvested microalgal cultures creates a huge operational cost during dewatering, thereby, rendering algae-based fuels less economically attractive. Currently there is no superior method of dewatering microalgae. A technique that may result in a greater algal biomass may have drawbacks such as a high capital cost or high energy consumption. The choice of which harvesting technique to apply will depend on the species of microalgae and the final product desired. Algal properties such as a large cell size and the capability of the microalgae to autoflocculate can simplify the dewatering process. This article reviews and addresses the various technologies currently used for dewatering microalgal cultures along with a comparative study of the performances of the different technologies.

Dewatering of microalgal cultures : a major bottleneck to algae-based fuels

A review on feedstocks, production processes, and yield for different generations of biodiesel

The over-exploitation of non-renewable resources leads to the depletion of energy reserves, as well as a rise in the price of petroleum-based fuels. Thus, there is a need to find suitable and sustainable substitutes for conventional fuels. The main features required for an alternative fuel are availability and renewability, or lower dependence on restricted resources accompanied with no or lower pollution. Due to their eco-friendly and non-toxic nature, biodiesel has been attracting increasing interest. Biodiesel production can be accomplished using various raw materials, catalysts, and technologies. In recent years, nanocatalyst technology has been widely used for biodiesel production due to its numerous advantages, such as large surface area, reusability and high activity of the nanocatalyst. This review provides an overview of biodiesel production with a description of various kinds of feedstock used, their advantages and disadvantages. Further, it offers a detailed description of different classes of biodiesel, including a characterization, assessment of qualities and limitations, and quality analysis of each type. Various methodologies used for biodiesel production are also elucidated, focusing on the potential of nanocatalyst processes. The aspect of nanocatalyst regeneration and reuse is also considered. This review delivers a comprehensive overview of biodiesel synthesis by discussing recent trends and challenges in this field, which will further the development of economically sustainable biodiesel production.

Recent advancement in biodiesel production methodologies using various feedstock: A review

Metal nanoparticles have received great attention from researchers across the world because of a plethora of applications in agriculture and the biomedical field as antioxidants and antimicrobial compounds. Over the past few years, green nanotechnology has emerged as a significant approach for the synthesis and fabrication of metal nanoparticles. This green route employs various reducing and stabilizing agents from biological resources for the synthesis of nanoparticles. The present article aims to review the progress made in recent years on nanoparticle biosynthesis by microbes. These microbial resources include bacteria, fungi, yeast, algae and viruses. This review mainly focuses on the biosynthesis of the most commonly studied metal and metal salt nanoparticles such as silver, gold, platinum, palladium, copper, cadmium, titanium oxide, zinc oxide and cadmium sulphide. These nanoparticles can be used in pharmaceutical products as antimicrobial and anti-biofilm agents, targeted delivery of anticancer drugs, water electrolysis, waste water treatment, biosensors, biocatalysis, crop protection against pathogens, degradation of dyes etc. This review will discuss in detail various microbial modes of nanoparticles synthesis and the mechanism of their synthesis by various bioreducing agents such as enzymes, peptides, proteins, electron shuttle quinones and exopolysaccharides. A thorough understanding of the molecular mechanism of biosynthesis is the need of the hour to develop a technology for large scale production of bio-mediated nanoparticles. The present review also discusses the advantages of various microbial approaches in nanoparticles synthesis and lacuna involved in such processes. This review also highlights the recent milestones achieved on large scale production and future perspectives of nanoparticles.

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A review on the biosynthesis of metal and metal salt nanoparticles by microbes

In recent decades, the concern over depletion of the world׳s petroleum reserves and environmental pollution has increased the demand to develop a renewable and environmental friendly fuel. Biodiesel, which mainly consists of Fatty Acid Methyl Esters (FAME) is one of the best substitutes for diesel fuel. Currently, vegetable oils, edible or non-edible, are the main resources of biodiesel. This review aims at providing comprehensive information and analyzes on biodiesel produced from edible and non-edible vegetable oils, their composition and specifications. Accordingly, the Fatty Acid (FA) profiles of 28 edible vegetable oils and 40 non-edible vegetable oils were collected. Their main specifications including sulfur content, density, viscosity, flash point, cloud point, pour point, cold filter plugging point, cetane number, iodine number, heating value, acid value and carbon residual before and after transesterification (vegetable oil and biodiesel, respectively) were analyzed in detail. Many researchers have developed prediction models to quantify biodiesel specifications to optimize its manufacturing and obtain biodiesel with the best specifications. Three factors that are especially influential are the fatty acids profiles, the degree of unsaturation within the FA structures and molecular weight. Accordingly, many models have been constructed on these features. There are also models that quantify the relationship between the biodiesel specifications and its thermodynamic properties or other specifications. Accordingly, the second part of this work was conducted on the existing prediction models. All the models were discussed along with their deviation in prediction.

A comprehensive review on properties of edible and non-edible vegetable oil-based biodiesel: Composition, specifications and prediction models

Biodiesel offers to be one of the renewable fuel that is in great demand due to hike in price and exploitation of various conventional resources. Biodiesel has gained wide attention as it emits less carbon monoxide and other pollutants. Biodiesel is known as mono-alkyl esters of long fatty acid, produced by transesterification in the presence of triglycerides and alcohol. The choice of catalyst and feedstock are the most important criteria for effective production of biodiesel. Catalyst and raw material selection play a significant role in the cost of biodiesel production. The heterogeneous catalyst offers a wide option for the catalytic selection because of its high selectivity and reusability characteristics. Recent advances in the field of catalytic technology for biodiesel production using nanosized catalyst is because of high stability over the repeated use. Nanocatalyst solves various bottleneck problem associated in the production of biodiesel. The present review is focused on various technologies and challenges linked to the production process, including some important aspects of feedstock selection. Thus the present review is maily focused on various catalytic technology used for biodiesel production using different production methods and potential feedstocks.

Gurunathan Baskar

Papers

Trends in catalytic production of biodiesel from various feedstocks

Biodiesel production from castor oil using heterogeneous Ni doped ZnO nanocatalyst.

Production of biodiesel from castor oil using iron (II) doped zinc oxide nanocatalyst

Optimization and kinetics of biodiesel production from Mahua oil using manganese doped zinc oxide nanocatalyst

Immobilization of cellulase onto MnO2 nanoparticles for bioethanol production by enhanced hydrolysis of agricultural waste