Emofuel to Save Earth - IJGHC

IJGHC, June 2013 – August 2013; Vol.2, No.3; 692-702. 

International Journal of Green and 

Herbal Chemistry 

An International Peer Review E-3 Journal of Sciences 

Available online at www.ijghc.com 

Green Chemistry 

E-ISSN: 2278-3229 

Research Article 

CODEN (USA): IJGHAY 

Emofuel to Save Earth 

J.S. Waghmare, Asma D. Fakir, Sadanand S. Kadam 

Oils, Oleochemicals and Surfactant technology, Institute 

of chemical technology, Mumbai, Maharashtra, India. 

Received: 6 June 2013; Revised: 16 August 2012; Accepted: 24 August 2013 

Abstract: Diesel engines are widely used as the driving power for both in-lands as well as 

marine transportation vehicles. It is because of Diesel engines has rigid structure, low 

breakdown rate, high thermal efficiency and high fuel economy. Because of these 

advantages of diesel engines, it is expected that diesel engines will be widely used in the 

upcoming future. However, nitrogen oxide and particulate matter these are the pollutants, 

which are emitted from diesel, and they are harmful to the health of living beings and 

environment. Therefore, diesel has been recognized as the major air pollution source in 

metropolitan areas. Because of this problem occurs by using diesel as engine fuel thus 

attracted much research interest. In the recent several years, the technology of application of 

emulsion fuels to many boilers, furnaces and diesel engines has attracted much attention 

from the point of view of the energy saving and of the prevention of atmospheric pollution. 

It is, mainly due to the recent high cost of crude oil. Emulsion fuel is a blend of existing fuel 

oil (heavy oil, light oil, kerosene etc) mixed with about 10-30% water. It is a new type of 

fuel used in internal combustion chambers such as engines; boilers etc and can reduce fuel 

consumption and emissions like NOx, PM and smoke by improving fuel efficiency. Many 

studies on emulsion fuels reveal that they have various benefits, including improvement in 

combustion efficiency and a reduction in particulate matter (PM) and nitrogen oxide (NOx) 

emissions. This review article provides information of emulsion, emulsion types, stability 

problems and emulsion fuel mechanism. 

Keywords: microemulsions, nanoemulsions, Lipophilic, micronization. 

692 IJGHC; June – August 2013, Vol.2, No.3, 692-702.

Emofuel... 

J.S. Waghmare et al. 

INTRODUCTION 

In the recent several years, as same as in over about thirty years ago, the technology of application of 

emulsion fuels to many boilers, furnaces and diesel engines has attracted much attention from the 

point of view of the energy saving and of the prevention of atmospheric pollution caused by the 

exhaust from many combustion facilities. It is, mainly, due to the recent high cost of crude oil and to 

the prevalence of the national consensus of the protection of environment. 

Will emulsion fuels save the Earth Emulsion fuel technology remains immature and falls short of 

providing a definitive solution to the question. Despite the great advances in the scientific and 

technological research of the technology, many different questions remain unsolved. Emulsion fuels 

refer to the emulsified mixture of petroleum-based fossil fuels, including gasoline, light oil, heavy oil, 

kerosene and waste oil, and water. A mechanism is assumed to work in emulsion fuels, which 

improves the combustion efficiency of the emulsified fossil fuel by virtue of the emulsified water. To 

provide this mechanism, various production devices have been proposed, although there has been no 

single technology developed to a satisfactory level. More recently, an innovative emulsion fuel 

production technology has been available that solves several problems inherent to this kind of fuel. 

Emulsion fuel is a blend of existing fuel oil (heavy oil, light oil, kerosene etc) mixed with about 10- 

30% water. It is a new type of fuel used in internal combustion chambers such as engines; boilers etc 

and can reduce fuel consumption and emissions like NOx, PM and smoke by improving fuel 

efficiency. 

It was first used in the US more than 40 years ago and many different types have been tested in Japan 

as well. Although it was commercialized as a new type of fuel about 10 years ago in the US and 

Europe with government support such as tax incentives and subsidies, currently its use has not been 

fully established yet. 

EMULSION 

An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or 

unbendable). Emulsions are part of a more general class of two-phase systems of matter called 

colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion 

should be used when both the dispersed and the continuous phase are liquids. In an emulsion, one 

liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions 

include vinaigrettes, milk, mayonnaise, and some cutting fluids for metal working. The photosensitive 

side of photographic film is also an example of a colloid. The word "emulsion" comes from the Latin 

word for "to milk", as milk is (among other things) an emulsion of milk fat and water. 

Two liquids can form different types of emulsions. As an example, oil and water can form, firstly, an 

oil-in-water emulsion, where the oil is the dispersed phase, and water is the dispersion medium. 

Secondly, they can form a water-in-oil emulsion, where water is the dispersed phase and oil is the 

external phase. Multiple emulsions are also possible, including a "water-in-oil-in-water" emulsion and 

an "oil-in-water-in-oil" emulsion. 

Appearance and Properties: Emulsions contain both a dispersed and a continuous phase, with the 

boundary between the phases called the "interface". Emulsions tend to have a cloudy appearance 

because the many phase interfaces scatter light as it passes through the emulsion. Emulsions appear 

white when all light is scattered equally. If the emulsion is dilute enough, higher-frequency and lowwavelength 

light will be scattered more, and the emulsion will appear bluer - this is called the 

"Tyndall effect". If the emulsion is concentrated enough, the color will be distorted toward 




comparatively longer wavelengths, and will appear more yellow. This phenomenon is easily 

observable when comparing skimmed milk, which contains little fat, to cream, which contains a much 

higher concentration of milk fat. 

Two special classes of emulsions - microemulsions and nanoemulsions, with droplet sizes below 

100 nm - appear translucent. This property is due to the fact that light waves are scattered by the 

droplets only if their sizes exceed about one-quarter of the wavelength of the incident light. Since the 

visible spectrum of light is composed of wavelengths between 390 and 750 nanometres (nm), if the 

droplet sizes in the emulsion are below about 100 nm, the light can penetrate through the emulsion 

without being scattered. 

Due to their similarity in appearance, translucent nanoemulsions and microemulsions are frequently 

confused. Unlike translucent nanoemulsions, which require specialized equipment to be produced, 

microemulsions are spontaneously formed by “solubilising” oil molecules with a mixture of 

surfactants, co-surfactants, and co-solvents. The required surfactant concentration in a microemulsion 

is, however, several times higher than that in a translucent nanoemulsion, and significantly exceeds 

the concentration of the dispersed phase. Because of many undesirable side effects caused by 

surfactants, their presence is disadvantageous or prohibitive in many applications. In addition, the 

stability of a microemulsion is often easily compromised by dilution, by heating, or by changing pH 

levels. 

Common emulsions are inherently unstable and, thus, do not tend to form spontaneously. Energy 

input - through shaking, stirring, homogenizing, or exposure to power ultrasound - is needed to form 

an emulsion. Over time, emulsions tend to revert to the stable state of the phases comprising the 

emulsion. An example of this is seen in the separation of the oil and vinegar components of 

vinaigrette, an unstable emulsion that will quickly separate unless shaken almost continuously. There 

are important exceptions to this rule - microemulsions are thermodynamically stable, while 

translucent nanoemulsions are kinetically stable. 

Whether an emulsion of oil and water turns into a "water-in-oil" emulsion or an "oil-in-water" 

emulsion depends on the volume fraction of both phases and the type of emulsifier (surfactant) (see 

Emulsifier, below) present. In general, the Bancroft rule applies. Emulsifiers and emulsifying particles 

tend to promote dispersion of the phase in which they do not dissolve very well. For example, proteins 

dissolve better in water than in oil, and so tend to form oil-in-water emulsions (that is, they promote 

the dispersion of oil droplets throughout a continuous phase of water). 

Instability: Emulsion stability refers to the ability of an emulsion to resist change in its properties 

over time 5 . There are three types of instability in emulsions: flocculation, creaming, and coalescence. 

Flocculation describes the process by which the dispersed phase comes out of suspension in the form 

of flakes. Coalescence is another form of instability - small droplets bump into each other within the 

media volume and continuously combine to form progressively larger droplets. Emulsions can also 

undergo creaming, where one of the substances migrates to the top (or the bottom, depending on the 

relative densities of the two phases) of the emulsion under the influence of buoyancy, or under the 

influence of the centripetal force induced when a centrifuge is used. 

"Surface active substances" (or "surfactants") can increase the kinetic stability of emulsions so that the 

emulsion does not change significantly with time. A "non-ionic" surfactant solution can become selfcontained 

under the force of its own surface tension, remaining in the shape of its previous container 

for some time after the container is removed. 




TYPES OF EMULSION 

There are mainly four types of emulsions. They are as follows: 

1. Simple Emulsion 

2. Multiple Emulsion 

3. Micro Emulsion 

4. Nanoemulsion 

Simple emulsion also known as a Macro emulsion. Simple emulsions are oil in water 

(O/W type). Multiple emulsions are composed of 3 phases: an inner and outer phase separated by a 

dispersed phase. Three phase emulsions are denoted as O/W/O (oil in water oil) and W/O/W (water in 

oil in water).Emulsion fuels can be either a microemulsion or macroemulsion. The essential 

differences between the two are stability (microemulsions are thermodynamically stable systems, 

whereas macroemulsions are kinetically stabilized) and particle size distribution (microemulsions are 

formed spontaneously and have dimensions of 10 to 200 nm, whereas macroemulsions are formed by 

a shearing process and have dimensions of 100 nm to over 1 micrometer). Microemulsions are 

isotropic whereas macroemulsions are prone to settling (or creaming) and changes in particle size 

over time. Both use surfactants (also called emulsifiers) and can be either water-in-oil (invert 

emulsions), or oil-in-water (regular emulsions) or bicontinuous (also called multiple or complex 

emulsions). Nanoemulsions 1 have uniform and extremely small droplet sizes, typically in the range of 

20–200 nm. In addition, highKinetic stability, low viscosity and optical transparency make them very 

attractive systems for many industrial applications. 

Emulsifying Agents: Emulsions are stabilized by adding an emulsifier or emulsifying agents. These 

agents have both a hydrophilic and a lipophilic part in their chemical structure. All emulsifying agents 

concentrate at and are adsorbed onto the oil: water interface to provide a protective barrier around the 

dispersed droplets. In addition to this protective barrier, emulsifiers stabilize the emulsion by reducing 

the interfacial tension of the system. Some agents enhance stability by imparting a charge on the 

droplet surface thus reducing the physical contact between the droplets and decreasing the potential 

for coalescence. Some commonly used emulsifying agents include tragacanth, sodium lauryl sulfate, 

sodium dioctyl sulfosuccinate, and polymers known as the Spans® and Tweens®. 

Emulsifying agents can be classified according to: 1) chemical structure; or 2) mechanism of action. 

Classes according to chemical structure are synthetic, natural, finely dispersed solids, and auxiliary 

agents. Classes according to mechanism of action are monomolecular, multimolecular, and solid 

particle films. Regardless of their classification, all emulsifying agents must be chemically stable in 

the system, inert and chemically non-reactive with other emulsion components, and nontoxic and 

nonirritant. They should also be reasonably odourless and not cost prohibitive. 

EMULSION FUEL MECHANISMS 

When emulsion fuel is injected into an engine or combustion chamber as a liquid, it is exposed to a 

high temperature. Water, which has a lower boiling point, will then vaporize and expand by 1700 

times in volume, thereby dispersing the surrounding liquid oil. Due to the micronization of the oil, the 

contact surface area with oxygen (air) increases which improves the combustion efficiency and fuel 

consumption. As a result of the more complete combustion, PM and smoke are also reduced greatly 

which leads to a reduction in emission gases. 



MECHANISM 

Micro Due to difference in boiling points, water expand or 

explosion explodes first (vol approx. 1700times). Subsequently the 

particles of oil are particulated and forced bending with 

the air occurs, thereby enabling efficient and complete 

combustion. 


EFFECT 

Reduction in fuel 

consumption 

Reduction in CO 2 

Cooling 

Ordinarily, NO x is generated when the air is exposed to Reduction in NO x. 

high temperatures. Water vapor dilutes the reactive and 

air is cooled, thereby reducing the NO x. 

Increased 

Fuel Spray 

Momentum 

Water-Gas 

Reaction 

The overall mass increase by adding water which has a 

higher density, thereby increasing the momentum and 

improving the mixture with the air. 

The fuel contacts the air, and the non-reacted carbon 

reacts with water, thereby supplementing imperfect 

combustion. 

C+H 2 O=CO+H 2 -131Kj 

CO+1/2O 2 =CO +283Kj 


consumption 



consumption 


Reduction in NO x. 

In addition, due to the latent heat capacity of water, the internal cylinder temperature of the engine is 

lowered. This suppresses the oxidation of nitrogen in the air and causes the generation of NOx to 

drop. In the combustion chamber, the carbon reacts with the oxygen in the water in what is known as 

a water-gas reaction which reduces substantially the amount of air required from the outside. 

Consequently, there is no cooling in the internal chamber which improves the heat efficiency. 

In theory, emulsion fuel is therefore effective in reducing emission gases and fuel consumption. As a 

result, many researchers including some large companies have been developing emulsion fuels for the 

last 40 years. 

ENVIRONMENTAL PROPERTIES 

Emulsion technology is not new - and it works 1 . It better atomizes fuel through the vaporization of 

water, allowing for a cooler and more complete combustion. In diesel or biodiesel-based emulsions, 

sub-micron water particles are entrained in the petroleum through a high-shear blending process that 

employs an additive to molecularly bond the water and petroleum together in a stable emulsion. 

Emulsions are the only fuel technology that simultaneously reduces both NO x and particulate matter 

(PM) emissions. 

Thermal NO x is reduced because of the quenching effect of water and PM is reduced by the kinetic 

changes in combustion. 




Fig.1: Emulsions as a Mechanism for Emission Reduction 

It is the water content and stability of emulsified fuels that produce their unique combustion 

characteristics. For example, when a base fuel is sprayed into the combustion chamber (whether it is a 

diesel engine, a steam boiler or a furnace), it is atomized into droplets varying in size from 20 to 100 

microns. Because only the surface of each fuel droplet exposed to air can burn, larger liquid fuel 

droplets do not burn completely, leaving unburned carbon to collect on the surfaces of a combustion 

chamber or escape as particulate matter in exhaust gases. This reduces overall thermal efficiency and 

increases harmful emissions. 

Fig.2: Base fuel combustion 

Fig. 2 (a): primary atomization of base fuel combustion 




Fig.2 (b): high temperature base fuel combustion 

Fig.2(c): incomplete combustion of base fuel combustion 

Fig.2 (d): particulates of base fuel combustion 




Unlike base fuels, when emulsified fuel droplets are sprayed into the combustion chamber, they are 

atomized a second time as a result of the violent transformation of their water content into steam. This 

transformation of water into steam shatters the petroleum surrounding that water into much smaller 

droplets (refer following figure). 

Fig.3 (a): primary atomization of emulsified fuel 

Fig.3 (b): secondary atomization of emulsified fuel combustion 

Fig.3(c): complete combustion of emulsified fuel combustion 




Fig.3 (d): reduced emission of emulsified fuel combustion 

Fig.3: Emulsified fuel combustion 

Smaller droplets have a much greater surface area, significantly improving the efficiency of 

combustion. This unique combustion characteristic of emulsified fuels is commonly referred to as 

“secondary atomization”. A secondary effect of water transforming into steam is that peak 

combustion temperatures are reduced, resulting in the formation of significantly fewer smog-forming 

NO x emissions. The changes in combustion kinetics also significantly reduce PM emissions that result 

from incomplete combustion. 

Role of Water in Combustion: Many studies on emulsion fuels reveal that they have various 

benefits, including improvement in combustion efficiency and a reduction in particulate matter (PM) 

and nitrogen oxide (NOx) emissions. Indeed, water particles vaporize and are explosively spread 

when emulsion fuels are ignited in an internal combustion engine and a boiler. The oil particles 

surrounding the water particles are also scattered and become finer with smaller particle sizes. Oil 

particles have more contact area with oxygen, and as a result, incomplete combustion is suppressed 

and combustion efficiency is improved. 

As a consequence, PM emissions are also reduced. In addition, nitrogen oxide (NOx) emissions are 

suppressed because the combustion temperature is relatively lower due to the heat from the 

evaporation of the vaporized water. An experiment on light oil emulsion fuel in a burner for boilers 

revealed that an increase in water composition (0 to 35%) improved the combustion efficiency (0% to 

15%) (Fig. 1). Another combustion experiment found that light oil emulsion fuel with water content 

of 25% reduced NOx emissions and PM by 60% and 90%, respectively, when burned in a diesel 

engine. 

Thus, water in the emulsion fuels is shown to improve combustion efficiency and contribute to 

emission reduction. It should be noted that carbon dioxide and PM emissions are complementary to 

each other; the carbon content of the fuel is equivalent to the combined carbon content of COx and 

PM emitted after it is burned. Therefore, if less CO2 (or CO) is emitted, more PM is discharged and 

vice versa. Therefore, when water reduces incomplete combustion and improves combustion 

efficiency, less PM and more COx are discharged. In other words, improved combustion efficiency 

boosts COx emissions, which is apparently a contradictory outcome. It is difficult to collectively 

estimate combustion efficiency and emissions of PM and NOx for the same type of emulsion fuels, 

since these parameters depend on the specific specifications of the engines or boilers used, 

combustion situations involved, and emulsifiers added. 




Fig.4: combustion of emulsion fuel for a boiler experiment 

BENEFITS OF EMULSION FUELS 

Carbon dioxide emission has been of vital concern globally because its reduction is critical to 

preventing global warming and saving humanity from the looming catastrophe. The “enemy” of this 

objective is our practices of fossil fuel consumption for sustaining our energy-intensive human lives. 

The data for 2007 show that fossil fuel consumption accounts for 82% of total energy consumption 

with the portions of coal and natural gas at 27% and 21%, respectively, while the rest includes nuclear 

energy (6%), biomass and waste (10%), and hydraulic power generation (2%). (Source: OECD/IEA; 

World Energy Outlook, 2009 Edition) The contribution of alternative energy technologies, such as 

photovoltaic and wind power generation, apparently remains slight, accounting for less than 1% of 

total consumption. Therefore, the portion of petroleum, or fossil fuel minus coal and natural gas, is 

34% of the total energy consumption globally. Fossil fuels, the overwhelming 82 percent portion of 

energy, are widely burned for energy conversion in manufacturing, processing and power plants, 

vehicles including automobiles, vessels including tankers and fishing boats, and garbage incinerators 

around the world. 

To more familiar examples, greater consumption of oil products for greenhouse, fisheries, and 

residential heating have placed very serious financial problems on farmers, fisherman, and the public. 

Thus, the impact of energy consumption ranges from industrial base structures to leading industries. 

Clearly, more efficient use of fossil fuels is one of the most urgent challenges for humanity in order to 

conserve energy resources, prevent global warming, revivify industry, and increase productivity 

relative to cost. Emulsion fuel technology is considered one of the most promising solutions to the 

conservation of fossil fuels. To date, many different attempts have been made to put the technology 

into commercial use, although they have failed to yield reliable and reproducible performance. 

REFERENCES 

1. R.Bertola, K. Li, Boulouchos, “Influence of Water-in-Diesel Emulsions and EGR on Combustion 

and Exhaust Emissions of Heavy Duty DI-Diesel Engines equipped with Common-Rail Injector 

System”. SAE 2003-01-3146. 




2. T.G. Mason, J.N. Wilking , K. Meleson, C.B. Chang , S.M. Graves, "Nanoemulsions: formation, 

structure, and physical properties", Journal of Physics: Condensed Matter, 2006, 18(41): R635- 

R666. 

3. T.S. Leong, T.J. Wooster, S.E. Kentish, M. Ashok kumar, "Minimising oil droplet size using 

ultrasonic emulsification", Ultrason Sonochem. 2009, 16(6):721-7. 

4. Handbook of Nanostructure Materials and Nanotechnology; H.S. Nalwa, ., Ed.; Academic Press: 

New York, NY, USA, 2000; Volume 5, pp. 501-575.J.W Park,., K.Y Huh,. And J.H Lee,., 

“Reduction of NOx, Smoke and Brake Specific Fuel Consumption with Optimal Injection Timing 

and Emulsion Ratio of Water-Emulsified Diesel”, Proc. Instn. Mech. Engrs., 2001, part D: 83-93. 

5. C.Y. Lin, and , K.H Wang., “The Fuel Properties of Three-Phase Emulsions as an Alternative Fuel 

for Diesel Engines”, Fuel, 2003, 82, 1367-1375. 

6. L.Piaseczny, and R. Zadrag,, “Water Fuel Emulsions Properties for Naval Diesel Engines”, 

Proceeding of Polish Conference on Gas Engines, Czestochowa, June, Poland, 2006. 

7. K. Adiga, and D. Shah, on the vaporization behavior of water-in-oil microemulsions. Combust. 

1990, Flame 80:412–415. 

8. Wang, and C. Law. Microexplosion of droplets under high pressure. Combust. 1985, Flame 59:53– 

62. 

9. R.E. Hall,: The Effect of Water/Residual Oil Emulsions on Air Pollutant Emissions and Efficiency 

of Commercial Boilers, Journal of Engineering for Power, Transactions of ASME October 1976, 

pp. 425-433. 

10. J.C. Birchley and N. Riley. Transient Evaporation and Combustion of a Composite Water-Oil 

Droplet, Combustion and Flame, 1977, 29, 145-165. 

11. M. Tsue, et al.: Statistical Analysis on Onset of Microexplosion for an Emulsion Droplet, Proc. 

Combust. Inst., 1996, 26, 1629-1635. 

*Corresponding Author: Dr. J.S. Waghmare; Oils, Oleochemicals and 

Surfactant technology,Institute of chemical technology, Mumbai, Maharashtra, 

India.

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