Prafulla D. Patil

Optimization of direct conversion of wet algae to biodiesel under supercritical methanol conditions.

This study demonstrated a one-step process for direct liquefaction and conversion of wet algal biomass containing about 90% of water to biodiesel under supercritical methanol conditions. This one-step process enables simultaneous extraction and transesterification of wet algal biomass. The process conditions are milder than those required for pyrolysis and prevent the formation of by-products. In the proposed process, fatty acid methyl esters (FAMEs) can be produced from polar phospholipids, free fatty acids, and triglycerides. A response surface methodology (RSM) was used to analyze the influence of the three process variables, namely, the wet algae to methanol (wt./vol.) ratio, the reaction temperature, and the reaction time, on the FAMEs conversion. Algal biodiesel samples were analyzed by ATR-FTIR and GC-MS. Based on the experimental analysis and RSM study, optimal conditions for this process are reported as: wet algae to methanol (wt./vol.) ratio of around 1:9, reaction temperature and time of about 255 °C, and 25 min respectively. This single-step process can potentially be an energy efficient and economical route for algal biodiesel production.

Optimization of microwave-assisted transesterification of dry algal biomass using response surface methodology

The effect of microwave irradiation on the simultaneous extraction and transesterification (in situ transesterification) of dry algal biomass to biodiesel was investigated. A high degree of oil/lipid extraction from dry algal biomass and an efficient conversion of the oils/lipids to biodiesel were demonstrated in a set of well-designed experimental runs. A response surface methodology (RSM) was used to analyze the influence of the process variables (dry algae to methanol (wt/vol) ratio, catalyst concentration, and reaction time) on the fatty acid methyl ester conversion. Based on the experimental results and RSM analysis, the optimal conditions for this process were determined as: dry algae to methanol (wt/vol) ratio of around 1:12, catalyst concentration about 2 wt.%, and reaction time of 4 min. The algal biodiesel samples were analyzed with GC-MS and thin layer chromatography (TLC) methods. Transmission electron microscopy (TEM) images of the algal biomass samples before and after the extraction/transesterification reaction are also presented.

Microwave energy potential for biodiesel production

Microwave energy based chemical synthesis has several merits and is important from both scientific and engineering standpoints. Microwaves have been applied in numerous inorganic and organic chemical syntheses; perhaps, from the time their ability to work as heat source was discovered. Recent laboratory scale microwave applications in biodiesel production proved the potential of the technology to achieve superior results over conventional techniques. Short reaction time, cleaner reaction products, and reduced separation-purification times are the key observations reported by many researchers. Energy utilization and specific energy requirements for microwave based biodiesel synthesis are reportedly better than conventional techniques. Microwaves can be very well utilized in feedstock preparation, extraction and transesterification stages of the biodiesel production process. Although microwave technology has advanced in other food, pharmaceutical and polymer chemistry related research and industry, it has yet to prove its potential in the biodiesel industry at large scale applications. This paper reviews principles and practices of microwave energy technology as applied in biodiesel feedstock preparation and processing. Analysis of laboratory scale studies, potential design and operation challenges for developing large scale biodiesel production systems are discussed in detail.

In situ ethyl ester production from wet algal biomass under microwave-mediated supercritical ethanol conditions

An in situ transesterification approach was demonstrated for converting lipid-rich wet algae (Nannochloropsis salina) into fatty acid ethyl esters (FAEE) under microwave-mediated supercritical ethanol conditions, while preserving the nutrients and other valuable components in the algae. This single-step process can simultaneously and effectively extract the lipids from wet algae and transesterify them into crude biodiesel. Experimental runs were designed to optimize the process parameters and to evaluate their effects on algal biodiesel yield. The algal biomass characterization and algal biodiesel analysis were carried out by using various analytical instruments such as FTIR, SEM-EDS, TLC, GC-MS and transmission electron microscopy (TEM). The thermogravimetric analysis (TGA) under nitrogen and oxygen environments was also performed to examine the thermal and oxidative stability of ethyl esters produced from wet algae. This simple in situ transesterification process using a green solvent and catalyst-free approach can be a potentially efficient route for algal biodiesel production.

Biodiesel production from low cost and renewable feedstock

Sustainable biodiesel production should: a) utilize low cost renewable feedstock; b) utilize energy-efficient, nonconventional heating and mixing techniques; c) increase net energy benefit of the process; and d) utilize renewable feedstock/energy sources where possible. In this paper, we discuss the merits of biodiesel production following these criteria supported by the experimental results obtained from the process optimization studies. Waste cooking oil, non-edible (low-cost) oils (Jatropha curcas and Camelina Sativa) and algae were used as feedstock for biodiesel process optimization. A comparison between conventional and non-conventional methods such as microwaves and ultrasound was reported. Finally, net energy scenarios for different biodiesel feedstock options and algae are presented.

Microwave-Enhanced In Situ Transesterification of Algal Biomass to Biodiesel

Microwave-enhanced in situ transesterification for algal biodiesel production can be considered as a green process and a preferred method as it increases reaction rates, reduces energy consumption and extractive-transesterification time, and produces a significant yield of product with less by-product formation. This process enables simultaneous extraction of lipids from algal biomass and efficiently transesterifies them into crude biodiesel. In this chapter, emphasis on the optimization of microwave-enhanced methods for algal biodiesel is presented with catalytic and non-catalytic approaches. The influence of process parameters on fatty acid methyl ester (FAME) yields under microwave “controlled power” and “controlled temperature” conditions is discussed. A response surface methodology (RSM) is applied to design the experiments and optimizes the process parameters. A novel integrated non-catalytic approach for direct conversion of algal biomass to fatty acid ethyl esters (FAEEs) under microwave-mediated supercritical ethanol (SCE) conditions is demonstrated. The reaction mechanism, experimental protocol, statistical analysis and experimental design, energy consumption of these presented processes are discussed in detail. This simple in situ microwave-enhanced transesterification process has the potential to provide an energy-efficient and cost effective route for sustainable algal biodiesel production.