Renewable and Sustainable Energy Reviews 50 (2015) 696–718
M.R. Avhad, J.M. Marchetti
Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Drøbakveien 31, Ås 1432, Norway
Article history:
Received 12 March 2015
Received in revised form
6 May 2015
Accepted 12 May 2015
Available online 31 May 2015 Biodiesel, which could be derived from plant oils and animal fats, is considered as a promising substitute for petroleum diesel fuel because of its advantages, such as renewability, biodegradability, less environmental toxicity, and superior combustion efficiency. The feedstock used for biodiesel production primarily include edible oils, non-edible oils, waste oils, and animal fats. Consistent scienti fic investigations are performed to locate innovative oil resources and minimize the utilization of expensive food-
a r t i c l e i n f o a b s t r a c t
Keywords:
Biodiesel
Alcoholysis reaction
Homogeneous catalyst
Heterogeneous catalyst grade oils for biodiesel production. The extensive research information is available on the determination of physico-chemical properties of different plant oils. This review will present a general information related to the existing varieties of oil feedstocks, their lipid content, and fatty acid composition.
This article further discusses different methods employed to enable the usage of plant oils as biofuel, such as its direct use, blending, thermal cracking, microemulsion, and alcoholysis process. Among the
possible methodologies for biodiesel production, alcoholysis process, in the presence or absence of a catalytic material, have been frequently employed. The benefits and limitations of using homogeneous, heterogeneous, enzyme catalysts, and supercritical method for the alcoholysis process are comprehensively discussed. In the current article, efforts have been made to review the recent inventions in homogeneous and heterogeneous catalytic materials utilized for biodiesel production. The present study shall provide a tool for the selection of an optimal catalyst for a large-scale biodiesel production.
& 2015 Elsevier Ltd. All rights reserved.
Contents
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697
2. Biodiesel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697
2.1. Different types of oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697
2.1.1. Edible plant oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 2.1.2. Non-edible plant oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698
2.1.3. Waste oils and animal fats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698
2.2. Use of straight plant oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698
2.3. Blending of plant oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701
3. Transformation of plant oils to biodiesel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701
3.1. Thermal cracking (pyrolysis). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701
3.2. Microemulsification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702
3.3. Alcoholysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702
4. Homogeneous catalysis for alcoholysis reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704
4.1. Homogeneous base-catalyzed alcoholysis reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704
4.2. Homogeneous acid-catalyzed alcoholysis reaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705
4.3. Homogeneous acid and base catalysts for the two-steps alcoholysis reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 706
5. Heterogeneous catalysts for alcoholysis reaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 707
5.1. Heterogeneous base-catalyzed alcoholysis reaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 707
5.2. Heterogeneous acid-catalyzed alcoholysis reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 709
M.R. Avhad, J.M. Marchetti / Renewable and Sustainable Energy Reviews 50 (2015) 696–718 697
5.3. Heterogeneous bi-functional catalysts or two-steps alcoholysis process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 712
6. Biocatalysts for alcoholysis reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 712 7. Supercritical method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713
8. Recent non-traditional development in catalysis and technology for biodiesel production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714 9. Summary and conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714 Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715
1. Introduction
Energy is a basic requirement for human existence. Due to a continuous growth in human population, the majority of the world total energy is utilized for the industrial applications, transportation, and for the power generation sector. According to the International Energy Outlook 2013 set by the U.S Energy Information Administration [1], the total energy consumed in 2010 was 5.5282 1020 J, which further is predicted to rise to 8.6510 1020 J by 2040. Accordingly, the total world energy consumption will grow by 56% between 2010 and 2040; this can be seen in Fig. 1.
Transportation is currently the second largest energy consuming sector and is increasing by an average of 1.1% per year [1]. In the current situation, the foremost amount of energy is supplied by the conventional fossil fuel resources, such as gasoline, liquefied petroleum gas, diesel fuel, and natural gas. However, the use of fossil fuels has several carcinogenic influences on the ecosystem, such as large greenhouse gas emissions, acid rain, and also global warming. In addition to serious environmental issues, dwindling reserves of crude oil, oscillating petroleum fuel prices, and the overconsumption of liquid fuels, especially for the transportation purposes, have made today's necessity to find an alternate “green” sources of energy which are sustainable, environmentally tolerable, economically competitive, and easily available. The numerous modes of renewable energy resources are anticipated to play a significant role in resolving the world's future power situation; therefore, over the past few years, researchers have driven their attention towards finding an appropriate replacement for fossil fuels. Renewable energy resources, such as solar energy, wind energy, hydro-energy, and biofuels (biodiesel, bioethanol, biogas, and biomass) have been considered as a potential alternative to reduce the entire dependency on the use of fossil fuels [2–4].
Amongst others, biodiesel is consistently gaining attention as a viable substitute for petroleum diesel in a near future due to its remarkable characteristics. Biodiesel production is persistently winning relevance and market due to its benefits, such as biodegradability, renewability, environmentally less toxicity, high combustion efficiency, high cetane number, high flash point, lower sulfur content,