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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 03, March 2019, pp. 576-584. Article ID: IJMET_10_03_059
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
ENGINE TECHNOLOGY AND RESEARCH
TRENDS OF ADVANCED BIOFUEL AS
ALTERNATIVE FUEL FOR TRANSPORTATION
VEHICLES
Byungmo Yang and Haengmuk Cho
Division of Mechanical and Automotive Engineering, Kongju National University,
Chungnam, Cheonan, Republic of Korea.
*Corresponding author
ABSTRACT
The reckless use of fossil fuels causes a lot of problems such as depletion of fossil
fuels, rising oil prices, air pollution, and fine dust. 27% of the world's major energy
sources are used for transportation, and most of the transportation fuels are used as
fossil fuels. Biofuels, which are attracting attention as a clean alternative energy
source, are most actively applied to transportation fuels because of their environment-
friendly characteristics, but they have problems in fuel production cost and engine
technology development. In order to solve these problems, research trends in domestic
and overseas researches and engine dedicated to biofuels are described. In addition,
the development of technologies that can reduce fuel production costs and the
establishment and operation of policies for more stable fuel supply are required more
flexibly to cope with sudden environmental changes.
Key words: Advanced biofuel, Engine technology, Emission characteristic, Engine
performance
Cite this Article Sutrisno, Setyawan Bekti Wibowo, Sigit Iswahyudi and Tri Agung
Rohmat, Vortex Dynamic Investigation of Wing Slotted Gap of Saab Jas Gripen C-
Like Fighter, International Journal of Mechanical Engineering and Technology, 10(3),
2019, pp. 576-584.
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1. INTRODUCTION
Thoughtless use of fossil fuel is causing numerous problems such as depletion of fossil fuel,
oil price rise and air pollution. In particular, 27 % of major energy source is globally used for
transportation and fossil fuel is mostly used as transportation fuel [1,2]. The exhaust gas
emitted from fossil fuel is the key pollutant of green-house gas that causes global warming,
and the exhaust gas resulting from combustion of such fossil fuel generates substances
harmful to human health. For NOx and PM which are major exhaust gases, the emission
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standard has been strengthened in phases from EURO 1 (enforced in 1993) to EURO 6
(enforces in 2014).
EURO 6 is the highest level exhaust gas control among the EURO controls enforced
previously, and the controls on NOx and PM have been strengthened to 80 % and 60 % of the
immediately preceding EURO 5 control respectively. New policies that support diffusion of
environment-friendly alternative fuels have been announced by many countries in the world
to overcome the limit of fossil fuel while solving problems of global warming and
environmental pollution. Biofuel that receives attention as a clean alternative energy source is
most actively used as a transportation fuel due to its environment-friendly characteristic.
Biofuel can replace fossil fuel without causing a major change in the existing supply base and
can also substantially reduce emission of environmental pollutants. Moreover, the high oil
price continuing recently makes the countries that want to bail out of dependence on the
petroleum from the Middle East enforce a policy of expanding supply of and support for
biofuel. Also, as the concentration of ultrafine dust in Korea caused by automobile exhaust
gas is at a very serious level, the Government has enforced the Polluting Vehicle Operation
Control System on old diesel vehicles pursuant to „Emergency Measures to Reduce Fine
Dust‟, and it is scheduled to be gradually expanded to other areas. According to the „First
Annual Report on Global Air announced by „HEI (Health Effect Institute)‟, a US private
environmental health organization, the mean annual ultrafine dust concentration in Korea on
which population weight is reflected has increased from 26 (1 microgram per of
air) in 1990 to 29 in 2015(Fig. 1).
Following the promotion of the policies at home and abroad that make use of new
renewable energy mandatory, use of bioenergy of which the percentage is the highest next to
waste energy (67.7 % in 2012) among the total new renewable energy supply is planned to
gradually increase. In this study, we intend to introduce the trends of studies carried out at
home and abroad to solve such issues and the technologies related to the engines that
exclusively use biofuel.
Figure 1 Average annual population – weighted PM2.5 concentrations in 2015
2. ADVANCED BIOFUEL R&D TREAND
2.1. Utilization of nonedible raw materials
From a raw material point of view, as all the existing biofuels use grain as the raw material,
all the biofuels made from nonedible bio-mass fall under the next generation biofuels.
Representative examples of such nonedible biomass include lignocellulose and marine algae.
The process of manufacturing biofuels from nonedible raw materials can be divided into
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biological technology and thermo-chemical technology. As shown in Fig. 2, when sugar is
extracted from biomass, it can be converted into a fuel by microbes. Bio-oil or synthetic gas
can be manufactured by pyrolyzing lignocellulosic materials in an oxygen poor condition, and
such an intermediate can be also converted into a biofuel through the conversion process
using a chemical catalyst.
Figure 2 Synthetic method of biodiesel from triglyceride.
2.2. Utilization of marine algae as raw materials
As the perception that not only the limited land but also the sea have to be utilized to cope
with the demand for bioenergy which will rapidly increase in the future proliferates, studies
attempting to mass produce marine biomass to utilize it for production of biofuel are also
actively carried out. Differently from lignocellulose which is an actually existing biomass
resource, in the case of marine bio-mass, uncertainty about resource acquisition is found to be
an obstacle. In the case of microalgae being particularly reviewed as promising species among
marine biomass, though there are autotrophic culture for which the energy source is sunlight
and heterotrophic culture for which the energy source is organic carbon, as stable supply of
organic carbon may be difficult in the case of a mass production process, studies on
development of autotrophic culture technology have been more invigorated. However, as the
utilization efficiency of sunlight which is the main energy source rapidly drops when the
volume of the reactor increases, no mass production technology has yet developed.
Besides, in the case of microalgae, as much energy is consumed for harvest of biomass
with the existing technology because the cell density of the culture medium is very low
showing a value not higher than 2g/l, the technologies of harvesting and enriching microalgae
more efficiently are required to be developed. As not only a light source, CO2 and water but
also different nutritive salts such as nitrogen, phosphorous, etc. are required for growth of
microalgae, such nutritive salts should be added to the culture medium when culturing
microalgae. As the nutritive salts added at this time have a direct effect on the production unit
price of bio-diesel, the unit price of culturing microalgae can be lowered if low-priced
nutritive salts are added.
For such a reason, studies on reducing the unit price of culturing microalgae by using
wastewater containing nutritive salts are actively carried out. If wastewater is utilized as a
nutrition source, the effects of reducing the unit price of culturing microalgae and of removing
pollutants can be expected. But, as the chemical composition of the wastewater changes every
day, there is a difficulty in using it as a microalgae culture medium. As biodiesel raw
materials in diverse forms show differences in their chemical compositions, etc., to actually
utilize them as a fuel, the composition and characteristics of each raw material are required to
be studied.
The first problem of the next generation biofuel is stable supply of raw material. Though
the production of the biofuel for transportation has steeply increased since 2005 when climatic
change became a serious issue in earnest, the increasing trend of biofuel production stopped
after 2010 as the price of the grain used as the raw material jumped. However, as mentioned
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earlier, because supply of biofuel 9 times that currently supplied is required to solve the
climatic change problem, a raw material supply plan for this is required to be established.
Second, as the fuel properties of bio-ethanol and bio-diesel which are currently used as
biofuels for transportation are not good, the maximum mixing rate is 10 % and 7 %
respectively. But, as the biofuel mixing rate should be in-creased to minimum 27 % to realize
450 scenario, new biofuels with superior fuel properties are required to be developed. Third,
though the objective of supplying biofuel is reduction of CO2 in the transportation sector, as
the CO2 reduction effect of the biofuel currently supplied is found to be not high in LCA (Life
Cycle Analysis), supply of biofuel with a higher CO2 reduction effect is important. EU and
USA are planning to strength the minimum CO2 reduction rate of biofuel supplied after 2014
and 2018 to 35 % and 50 % respectively to increase the CO2 reduction effect of biofuel
supply.
2.3. Improvement of biofuel properties
Mixed use of bioethanol and bio-diesel which are the biofuels currently supplied is permitted
only at a very limited concentration due to the difference in the material properties from those
of the petroleum-based fuel. Bioethanol and biodiesel are permitted to be mixed at the
concentration of maximum 10 % and 7 % respectively. For high content mixing of biofuel,
improvement of bio-fuel properties is important. The key in such improvement of material
properties is deoxydation, removal of oxygen contained in biofuel. The processes reviewed
for deoxydation include hydrogenation carried out with hydrogen added and decarboxylation
carried out without adding hydrogen. Though the hydro deoxygenation has an advantage that
yield can be increased, it has a problem that hydrogen should be supplied from outside and,
though the decarboxylation does not require an outside hydrogen supply source, it has a
problem that the yield of biofuel decreases due to loss of carbon. Accordingly, if no large
quantity hydrogen supply source is available, the deoxydation technology by decarboxylation
is required to be applied. As to biofuel with improved material properties, only Hydro treating
Bio-Diesel (HBD) has been commercialized [1].
Bioethanol not only has a higher oxygen content than that of gasoline but also its material
properties are very different as it is a low molecular weight compound. Accordingly, the
interest in butanol of which the molecular weight is bigger is picking up. Though the material
properties of bio-butanol is superior not only because its oxygen content is lower than that of
ethanol but also because its molecular weight is bigger, as it is highly toxic to microbes, the
maximum concentration that can be manufactured through a fermentation process is very low
showing a value of about 2 %, which is about 1/6 that of ethanol [5]. Accordingly, as the
enriched energy cost of bio-butanol is so high that there are difficulties in commercializing it.
To solve such a problem, along with development of the strain with reinforced resistance to
butanol, a study on development of a low energy consumption type butanol refinement
technology is being carried out. Recently, studies on conversion of biomass to long chain
hydrocarbon utilizing a chemical catalyst or biological catalyst is being carried out to develop
biofuel of which the properties are closer to those of the petroleum-based fuel.
2.4. Carbon Dioxide Reduction Efficiency
Besides the problem that the biofuels currently supplied is made from grain, many
controversies are raised on its CO2 reduction effect. In the case of ethanol produced from corn
of which the quantity actually supplied is the biggest, it is reported through an LCA that it
actually aggravates the global warming problem as it generates 3 % more CO2 than gasoline
does if the process fuel is utilized as coal [6]. If the by-products generated in corn plantations
are utilized as an energy source, it is shown that the CO2 reduction rate can be increased by
about 50 % at the maximum. Also, if the raw material is replaced with lignocellulose not
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corn, the CO2 reduction rate of ethanol is reported to increase by maximum about 86 %. Such
a study result shows that the rate of CO2 reduction resulting from use of biofuel differs greatly
depending not only on the raw material used but also the process technology applied.
3. ADVANCED BIOFUEL ISSUE
Thoughtless use of fossil fuel causes numerous problems such as depletion of fossil fuel, oil
price increase, etc., and new policies have been announced by many countries in the world
that support diffusion of environment-friendly alternative fuels to overcome the limit of fossil
fuels while solving the problems of global warming and environmental pollution. Therefore,
bio-diesel which receives attention as a clean alternative energy source is most actively used
as a fuel for translation. Bio-diesel can replace fossil fuel without causing a major change in
the existing supply base and can also substantially reduce emission of environmental
pollutants. Moreover, the high oil price continuing recently makes the countries that want to
bail out of dependence on the petroleum from the Middle East enforce a policy of expanding
supply of and support for biofuel.
Though the next generation bio-fuel is desirable in that it utilizes nonedible raw material,
it has a problem that the production unit price is still high. Accordingly, development of
technologies for improvement in the economic efficiency of the next generation bio-fuel is
actively in progress. The core of such improvement in economic efficiency is simplification
of process and enhancement of bio-fuel yield through application of a highly efficient
catalyst. For this reason, as biotechnology advances recently, development of a customized
microbial catalyst that has diverse fermentation functions is intensively studied in particular.
As shown in Fig. 6, though production of catalyst and C5, C6 fermentation were carried
out by a different strain respectively in the case of lignocellulosic ethanol manufacturing
process in the past, studies are carried out recently to lower the ethanol manufacturing cost by
simplifying the manufacturing process of lignocellulosic ethanol through development of a
customized strain that contains each and every gene related to fermentation [3].
Figure 3 Biocatalyst for the consolidate bioprocess
Recently, a study result has been announced on development of a strain that converts
biomass directly into the bio-gasoline having the same material properties as the petroleum-
based hydrocarbon. To avoid the difficulty in sugar extraction process which is the biggest
obstacle in the production process of a lignocellulosic bio-fuel, a fusion process which
gasifies a lignocellulosic material through thermal decomposition and then converts the
synthetic gas so generated into a fuel using microbes is also under development. Though the
said technology has an advantage that pre-treatment which is the most serious problem in
production of a lignocellulosic fuel through a bioprocess can be avoided, there is a problem
that, as the water solubility of the synthetic gas is low, its contact efficiency with microbes as
Genomics Proteomics Bio-Informatics
Biomass Bioalcohol
Custom biocatalyst
- C5, C6 degradative enzyme production
- C5 alcohol fermentation function
- C6 alcohol fermentation function
- Production of lignin-degrading enzyme