Overview of world energy consumption
Energy is the most essential elements to all the living organisms of the universe. It is the most
fundamental needs for the survival of human life on the Earth. The primary energy
consumption has increased by 2.2% in 2017 compared to 1.2% in 2016 (BP p.l.c., n.d.). The
prediction of energy demand trend might continue to rise by more than 25% to 2040 based on
WEO's New Policies Scenario (SAFETY4SEA, 2018). In other words, the global energy
consumption is said to be increasing gradually over the years. The development of the countries
is the primary factor that resulting the expanding of world energy consumptions.
Since 2009, China as one of the developed countries has become the world’s largest
energy consumer due to the sustained economic growth and strong industrial demand
( Enerdata, 2018). The energy consumption in China can be separated into 5 main energy end-
use sectors, which are the service sector, transportation sector, agriculture sector, household
sector and industry sector. The service sector energy consumption has the highest annual
growth rate of 7 % from 1980 to 2004, followed by household sector at 5.4%, industry sector
at 5.1%, transportation sector at 3.5% and agriculture sector at 3.4% per year which has shown
in figure 1 (Zhou, et al., 2007).
Figure 1: Historical Energy Consumption by Sector in China
(Zhou, et al., 2007)
The source of energy can be categorized into two main groups which are renewable
energy and non-renewable energy. Renewable energy represent as the unlimited energy sources
that do not deplete and able to replenish rapidly after being consumed; while, non-renewable
energy sources is not able to regenerate in a short amount of time after being consumed
(SANFORD , 2006). The most widely used of renewable energy sources are solar energy,
hydro power, geothermal energy, biomass conversion, wind energy and so on. Whereas most
common non-renewable energy includes fossil fuels, natural gas, petroleum and coal.
The non-renewable energy resource is the main source of energy that currently being
used across the world. Over 66% of the total primary energy supply is generated by fossil fuels
such as coal, crude oil and natural gases (GREENTUMBLE, 2017). Fossil fuels are widely
being used due to large amount of energy can be generated through combustion compare to
other energy sources. However, there are some environmental drawback when using non-
renewable energy sources. Greenhouse gasses such as carbon dioxide and methane gas will be
produced when burning of fossil fuels like crude oil and coal, eventually resulting global
warming. Besides, carbon monoxide and soot (carbon particles) will be generated when
incomplete combustion occurs and this will lead to air pollution and affecting human health
once inhaled (ccacoalition, n.d.).
Based on the BP Statistical Review of World Energy 2016, the fossil fuel such as coal,
natural gas and crude oil would be exhausted in the next 150 years, 49 years and 47 years
respectively (Knoema, 2018). These figures might change over the time due to the future
uncertainties in terms of labour and financial to be invested in the projects which requires
advanced technology and equipment to extract out these fossil fuels. Therefore, renewable
energy has introduced as an alternative energy sources to replace non-renewable to become the
main source of energy in power generation. The production of renewable energy has an average
growth rate of 5.4% compare to fossil fuel and nuclear energy of 1.6% for the past 10 years
(2005 to 2015) (REN21, 2018). Renewable energy has a great potential to slowly replace fossil
fuels in the future. It is the key solution to deal with environmental issues such as global
warming and depletion of energy sources. Natural resources such as solar, hydro and wind
energy is considered to be the sustainable energy resources due to infinite regeneration. Besides,
the amount of carbon dioxide being released during the burning of biomass is same as the
carbon dioxide intake by plant during photosynthesis reactions. In other words, biomass is
known as the carbon neutral materials due to zero net emission of carbon dioxide during
combustion.
Figure 2: The Comparison between the Growth of Global Renewable Energy and Total Final
Energy Consumption from 2005 to 2015
(REN21, 2018)
Biofuel
Biofuels are a type of energy source derived from biological carbon fixation. It is a renewable
carbon neutral alternative to replace fossil fuel since both have the same working principles to
generate energy through fuel combustion. Biofuels generated from biomass can be separated
into 3 main types, which are liquid biofuels (ethanol or butanol), gaseous biofuel (Biogas) and
solid biofuel (biomass) (T.C. , et al., 2014 ). Even though they all fall under the same renewable
biofuel categorise but each of them has differences in terms of production method.
Wood, charcoal, leaves, animal dung and municipal waste are some of the examples of
solid biofuels. In most of the case, no further production step is required for solid biofuels due
to it is always appear in convenient form to be burned readily. However, an additional process
known as “densifying” is required to have a better performance in terms of burning and
transportation for some of the biomass such as sawdust and wood chips. Pellets and bricks are
the common “densified” forms of solid biomass (Biofuel.org.uk, 2010).
Furthermore, biogas is basically known as a mixture of different gases generated by the
breakdown of organic matter without the present of oxygen. It can be produced through
anaerobic digestion of raw materials such as municipal waste, sewage, food waste and
agricultural waste by anaerobic organisms (N B , 2016). The composition of biogas is mainly
contained of methane and carbon dioxide and small amounts of hydrogen sulphide moisture
and siloxanes. The energy release during the combustion of biogas and oxygen allow it to be
used as a fuel in gas engine (N B , 2016).
Liquid biofuels can be a potential substitution for all types of internal combustion
engines that operating by diesel, kerosene and gasoline due to the concern of greenhouse gas
emissions from fossil fuels, depletion of fossil fuels and support from government subsidy
policies. Liquid biofuels are more biodegradable compared to fossil fuels which allowing it to
be burned completely during combustion, eventually reducing carbon dioxide emission to the
environment. Besides, liquid biofuels are categorized as the secondary biofuel that generated
from the processing of biomass. There is a total of four generation of biofuels which is
categorized based on the origin and production technology of biofuels (Eva-Mari , 2016).
Table 1: Description on each type of biofuel generations
Generation of Biofuels Description
First Generation biofuels It is directly produced from food crops such as sugarcane and wheat by
abstracting the oils for the usage of biodiesel or generating bioethanol
through fermentation. The main drawback of 1st generation biofuels is
due to the food crops feedstock, it will lead to a debate between fuel vs.
food crisis.
Second Generation Non-food crops such as organic waste, straw and wood is used as the
biofuels feedstock to produce biofuel in order to encounter the food crisis issues
facing in 1st generation biofuels.
Third Generation It is based on improvement in the production of biomass. Engineered
biofuels energy crop such as algae is cultivated and being used as the renewable
energy feedstock to produce biofuels. Algae has the potential to replace
conventional crop to generate more energy at lower cost.
Fourth Generation It is planned to generate sustainable energy but also aimed to capture
biofuels and store carbon dioxide in order to achieve carbon negative rather than
just carbon neutral characteristics.
(IASSCORE, 2018)
Biodiesel
The first publication demonstrating the chemical interesterification of edible lipids was carried
by Normann in the year of 1920 (Dérick , et al., 2017). This advance technique is the alternative
way to replace transesterification of vegetable and plant oil to produce biodiesel which had
started by scientists E. Duffy and J. Patrick in the year of 1853 (ABDULKADIR, et al., 2014).
In the 19th century, the discovery of crude oil across the world has driven the oil company to
expand refinery production in order to reducing the cost of diesel fuel tremendously (Fuel
Sucks, 2018). Therefore, biodiesel was not significantly being used to power diesel engine
during that time due to the available of low-cost diesel fuel.
Long-term effects of global warming and depletion of fossil fuel drives the substitution
of power source from fossil fuel to biodiesel. The global average annual growth rate of
biodiesel has increased 37% over the period started from the end of 2005 to 2011 (Victor , et
al., 2014). The expansion of global biodiesel production indicates that biodiesel has a great
potential to replace petroleum-derived diesel in the future fuel market.
Figure 3: The Comparison between Global and Brazilian Biodiesel Production since the year
of 2000 to 2012
(Victor , et al., 2014)
Production pathway of biodiesel
The table shows below are the potential technologies available in the biodiesel production
industries.
Table 2: Potential technology methods in biodiesel production
Potential Description
Technology Methods
1) Direct use and This method is either mixing of vegetable oil with diesel fuel or to
blending of be used directly in the engines. Based on the long-term engine testing
vegetable oils in result, problems such as choking on injectors, deposition of carbon,
Diesel engines oil ring sticking and thickening and gelling of the engine lubricant
oil might occur (Rajalingam, et al., 2016).
2) Transesterification This method is widely used in the biodiesel production due to the
Process formation of high combustion efficiency biodiesel as the end
products. This process starts with the reaction between triglycerides
in the animal fats or plant oil and alcohol with the help of catalyst to
produce biodiesel and glycerol as the by-products (Rajalingam, et
al., 2016).
3) Pyrolysis and This method is using heat to convert the complex structure of
thermal catalytic hydrocarbons from biomass into biodiesel with or without the help
cracking catalyst (Mujeeb, et al., 2016). The treated fuel could be straight
away use in diesel engine without any addition modification after
this process.
4) Microemulsion of This method is defined as when there are two immiscible liquids and
oil ionic or non-ionic amphiphiles, a colloidal equilibrium dispersion of
optically isotropic fluid with the range of 1-150nm will happen
(Mujeeb, et al., 2016). The viscosity issue is able to be solved but the
amount of energy being released is also reduced (Mujeeb, et al.,
2016).
Chemical Interesterification Process of Biodiesel
Chemical interesterification is an advance alternative way to replace transesterification of
triglyceride with short-chain alcohols to produce biodiesel due to high production of glycerol
as the by-products (Kusumaningtyas, et al., 2016). Therefore, an additional separation steps is
required in order to obtain high purity level of biodiesel. Separation steps is considered to be
the most energy consuming and cost-intensive in the chemical processes. During the separation
process, a separation agent is normally being released out as a waste which might cause
significant impact to the environment (Kusumaningtyas, et al., 2016). Thus, absence of
separation steps is important to have a better economic aspect in terms of cost saving.
Chemical interesterification process is able to prevent the formation of glycerol or water
as the side-products by reacting vegetable oil with methyl or ethyl acetate as the reactant rather
than short-chain alcohols and with the help of catalyst (Kusumaningtyas, et al., 2016). This
chemical process will generate methyl esters (biodiesel) and triacetin as by-product which is
able to use as fuel bio-additive to improve fuel efficiency in terms of oxidation stability, cloud
flow properties (pour point & cloud point) and viscosity. Besides, triacetin is also able to use
as anti-knocking agent in diesel fuels (Kusumaningtyas, et al., 2016).
This chemical interesterification process consists of three consecutive reversible
reactions. Firstly, the triglyceride reacts with methyl acetate to produce fatty acid methyl ester
(biodiesel) and monoacetin diglyceride. The monoacetin diglyceride will again react with
methyl acetate to produce fatty acid methyl ester (biodiesel) and diacetin monoglyceride in the
second step. Finally, diacetin monoglyceride reacts with methyl acetate to generate fatty acid
methyl ester (biodiesel) and triacetin (by-products). In short, the whole process requires 1 mole
of triglyceride and 3 moles of methyl acetate to generate 3 moles of fatty acid methyl ester
(biodiesel) and 1 mole triacetin (by-products) (Kusumaningtyas, et al., 2016). Acid or base
catalysts can be used in this interesterification process in order to shorten the reaction time.
Figure 4: The chemical interesterification reaction of triglycerides with methyl acetate.
(Abraham , et al., 2013)
Figure 5: The overall chemical interesterification reaction of triglycerides with methyl
acetate
(Abraham , et al., 2013)
Types of catalyst being used in chemical interesterification reaction
Acid and base catalysts can be used in the chemical interesterification reaction to produce acid
methyl ester (biodiesel) and triacetin (by-products). The table below shows the comparison of
biodiesel conversion by using different acid and base catalysts under the same reaction
condition.
Table 3: Various of acid and base catalysts in chemical interesterification reaction of
triglycerides with methyl acetate
(Abraham , et al., 2013)
According to the table above, there is no formation of acid methyl ester (biodiesel)
when using potassium hydroxide as the catalysts. This is due to the absence of alcohol in ester
medium that causing hydroxide not able to form alkoxide which is responsible for the reaction
(Abraham , et al., 2013). In fact, potassium hydroxide undergoes irreversible reaction with ester
to form potassium soaps and potassium acetate.
On the other hand, alkaline methoxides are the most widely used catalyst in chemical
interesterification reaction. However, the alkaline methoxide is not likely to dissolve in the
vegetable oil and methyl acetate which has limited their efficiency in the chemical
interesterification reaction, eventually reducing the desire product conversion rate (Abraham ,
et al., 2013). Therefore, a phase transfer catalyst such as polyethylene glycol (PEG) is required
to improve the solubility of alkaline methoxide in organic phase (Abraham , et al., 2013). PEG
will react with potassium methoxide to form PEGK complex. However, there are few problems
encountered when using PEG in the interesterification reaction. Firstly, additional separation
step is needed to remove PEG from the reaction mixture. The remaining of PEG in vegetable
oil can be extracted out by using water due to PEG is highly insoluble in the solvent. Besides,
the hydroxyl groups at both end side of PEG will react with triglycerides and methyl acetate
through transesterification reaction to produce high-molecular-weight PEG esters (Alberto &
Román, 1998).
