Energy and Power Engineering, 2013, 5, 350-355
doi:10.4236/epe.2013.54B068 Published Online July 2013 (
A Comparison of the Use of Pyro lysis Oils in Diesel Engine
C. Wongkhorsub, N. Chindaprasert
Department of Mechanical Engineering, Faculty of Engineering, Rajamangala University of Technology Phra Nakhon,
Bangkok, Thailand
Received March, 2013
Creating a sustainable energy and environment, alternative energy is needed to be developed instead of using fossil fu-
els. This research describe a comparison of the use of pyrolysis oils which are the tire pyrolysis oil, plastic pyrolysis oil
and diesel oil in the assessment of engine performance, and feasibility analysis. Pyrolysis oils from waste tire and waste
plastic are studied to apply with one cylinder multipurpose agriculture diesel engine. It is found that without engine
modification, the tire pyrolysis offers better engine performance whereas the heating value of the plastic pyrolysis oil is
higher. The plastic pyrolysis oil could improve performance by modifying engine. The economic analysis shows that
the pyrolysis oil is able to replace diesel in terms of engine performance and energy output if the price of pyrolysis oil is
not greater than 85% of diesel oil.
Keywords: Pyrolysis; Pyrolysis Oil; Engine Performance; Feasibility Study
1. Introduction
Due to the fossil fuel crisis in past decade, mankind has
to focus on developing the alternate energy sources such
as biomass, hydropower, geothermal energy, wind en-
ergy, solar energy, and nuclear energy. The developing
of alternative-fuel technologies are investigated to de-
liver the replacement of fossil fuel. The focused tech-
nologies are bio-ethanol, bio-diesel lipid derived biofuel,
waste oil recycling, pyrolysis, gasification, dimethyl
ether, and biogas [1]. On the other hand, appropriate
waste management strategy is another important aspect
of sustainable development since waste problem is con-
cerned in every city.
The waste to energy technology is investigated to
process the potential materials in waste which are plastic,
biomass and rubber tire to be oil. Pyrolysis process be-
comes an option of waste-to-energy technology to deliver
bio-fuel to replace fossil fuel. Waste plastic and waste
tire are investigated in this research as they are the
available technology. The advantage of the pyrolysis
process is its ability to handle unsort and dirty plastic.
The pre-treatment of the material is easy. Tire is needed
to be shredded while plastic is needed to be sorted and
dried. Pyrolysis is also no toxic or environmental harmful
emission unlike incineration [2].
The tire pyrolysis oil and plastic pyrolysis oil have
been investigated and found that they both are able to run
in diesel engine and the fuel properties of the oils are
comparable to diesel oil [3,4]. Both pyrolysis oils are a
complex mixture of C5-C20 organic compounds. The tire
pyrolysis oil contains a great proportion of aromatics and
up to 1.4% sulfur content whereas the plastic pyrolysis
oil is able to occur high chlorine content if the plastic is
unsorted [5,6]. The assessment in terms of chemical
process, production and feasibility study of both pyroly-
sis oils are done in previous researches [7-9]. There is no
research about the use of the oil in terms of cost analysis
and potential of fossil fuel replacement.
This research describes a comparison of the use of py-
rolysis oils which are the tire pyrolysis oil and plastic
pyrolysis oil in the assessment of engine performance,
environmental impact, and feasibility analysis. The oils
are researched and applied with DI Diesel engine. The
sensitivity analysis of the oil price subjected to the oil
performance is also distinguished in the research. The oil
characteristic and financial data are studied from a com-
mercial plastic pyrolysis and a commercial tire pyrolysis
plant in Thailand.
2. Pyrolysis Oil
Feedstock material is the main factor to indicate the
properties of the pyrolysis oil. Tire pyrolysis and plastic
pyrolysis technologies are the available technologies on
the market in Thailand. The feedstock pre-process is one
of the main factors to assess the possibility of the tech-
nology. The waste tires are collected easily from the
scavenger and garage as they are bulky and heavy but
only shredding process is required to reduce the size. The
Copyright © 2013 SciRes. EPE
waste plastics are collected from scavenger, MSW sort-
ing plant, and landfill area. The weakness of the plastic is
the character of the plastic, which is mainly from plastic
bag, is small high impurity and bulky. Soring and clean-
ing is required for plastic process. However, as the pur-
pose of the process is turning waste to energy, the pyro-
lysis process of tire and plastic is distinguished and
compared in this research. Physical and chemical analy-
sis properties of both oils are studied and compared in
order to ensure to usage of the oil in diesel engine.
2.1. Plastic Pyrolysis Oil
In the USA, plastic waste approximately 31 million of
tons was generated in 2010 which is about 17.45% of
total waste by weight as shown in Table 1 [10]. The
percentage of the plastic waste is also similar in Thailand
and around the world. As known that plastic is a non-
degradable petroleum based product. The old landfill
area is found that degradable product is composted, be-
come soil while plastic is still exist. This problem is
solved by converting waste plastic to energy by pyrolysis
As the petroleum based plastic is the polymeric mate-
rial, the plastic pyrolysis process is the thermal de-po-
lymerization process in the absence of oxygen which is
able to convert plastic into gasoline-range hydrocarbons
[11]. The waste plastic used in pyrolysis process is
needed to be sorted and cleaned. The Polyethylene (PE)
and Polypropylene (PP) which are the main component
of the plastic in municipal solid waste are used in the
process in order to prevent the contamination of chlorine
in the oil [6]. The classified waste plastic is processed
from an autoclave pyrolysis reactor. In general, product
yields from pyrolysis are varied with temperature. The
plastic pyrolysis oil used in this research is processed at
300-500°C at atmospheric pressure for 3 hours. The
product output consists of 60-80% pyrolysis oil, 5-10%
residue and the rest is pyrolysis gas on weight basis. The
plastic pyrolysis oil used in this research is processed
from a commercial waste plastic pyrolysis plant in Thai-
Table 1. Contents of municipal solid waste in the USA year
Component Amount
(Millions of tons)
(by weight)
Paper Waste 71.31 40.09%
Glass 11.53 6.48%
Metal 22.41 12.60%
Plastic Waste 31.04 17.45%
Woods 15.88 8.93%
Miscellaneous 25.69 14.44%
2.2. Tire Pyrolysis Oil
In the USA, about 303.2 million of waste tires were dis-
carded in year 2007, while about 60 million of waste tires
in Thailand year 2011. Not to mention about the cumula-
tive waste tire in landfill, the problem of tire disposal will
be increasing gradually due to the expanding of vehicle
market. The tire pyrolysis process converts waste tires
into potentially recyclable materials such as flammable
gas, pyrolysis oil and carbon black [12]. Although the
amount of waste tire is less than the waste plastic, the
option of the waste tire conversion is limited.
Tire pyrolysis oil plant has been established around the
world in order to produce the substitute liquid fuel for
heating purpose as found that the tire pyrolysis oil have a
high gross calorific value (GCV) of around 41-44 MJ/kg
[13]. Waste tire is needed to be shredded before process.
The desulphurization is required in the pyrolysis system
to eliminate the sulfur. It was determined that the oil
production yield of tire pyrolysis process has a maximum
at 350°C and decomposes rapidly above 400°C [13]. The
plastic pyrolysis oil used in this research is processed at
300-500°C at atmospheric pressure for 3 hours. The tire
pyrolysis oil used in this research is processed from a
commercial waste tire pyrolysis plant in Thailand. The
product output consists of 35% pyrolysis oil, 56% resi-
due and the rest is pyrolysis gas on weight basis. The
amount of the residue is tire wire scrap and carbon black.
2.3. Characteristic of Pyrolysis Oil
Pyrolysis is a complex series of chemical and thermal
reactions to decompose or depolymerize organic material
under oxygen-free conditions. The products of pyrolysis
include oils, gases and char. The pyrolysis oil products in
this research are from tire and plastic which are dissimi-
lar in physical properties and chemical properties. The
appearance of the tire pyrolysis oil is thick-liquid and
dark colour oil whereas the appearance of the plastic py-
rolysis oil is grease oil liked and dark colour oil at 30°C
(room temperature). They all strong smell due to the high
aromatic substance.
As the comparison usage of this research is in diesel
engine, the pyrolysis oil from process is a mixture of
carbon composition which are C5-C20 in tire pyrolysis oil
and C10-C30 in plastic pyrolysis oil. The oil requires dis-
tillation process to differentiate the diesel-like oil from
other compounds. The distillation temperature applied in
this research is 180°C. The substance that evaporates
before 180°C is taken out. The remaining is analyzed and
tested in one cylinder multipurpose agriculture diesel
engine. The properties comparison of plastic oil, tire oil
and diesel oil is analyzed as shown in Table 2.
The proximate analysis was conducted using a ther-
mo-gravimetric analyzer. The elemental determination
Copyright © 2013 SciRes. EPE
(carbon, hydrogen, nitrogen and sulfur content) are ana-
lyzed by a CHNS Elementary Analyzer. The chlorine
content of PVC was determined by improved oxygen
bomb combustion – ion chromatography method which
is based on the standard method in ASTM D 4208-02.
The heating value of all the samples was measured using
bomb calorimeter.
The heating value and the flash point of plastic pyro-
lysis oil is the highest while the other properties are
comparable. As the plastic pyrolysis oil is wax form in
room temperature, the oil requires pre-heating process
before input to diesel engine.
3. Engine Performance Analysis
Engine performance indicates the effects of a fuel in the
engine. It shows the trend and possibility of using pyro-
lysis oil to replace diesel oil without any engine modifi-
cation. It is necessary to determine break torque (T), en-
gine break power (P), break specific fuel consumption
(bsfc), and break thermal efficiency (th ). These several
parameters can be obtained by measuring air and fuel
consumption, torque and speed of the engine, and heating
value of the oil. The performance parameters can be cal-
culated by equations as followed [14].
3.1. Break Torque
Torque is an indicator of the function of break torque
calculated by the moment of engine arm connected to
weight scale as:
TFd (1)
where T is break torque in Nm, F is force of engine arm
applied to the load in N, and d is the distance of engine
arm from center of the rotor to the load.
Table 2. Properties of pyrolysis oil.
Property Tire Pyrolysis oil Plastic Pyrolysis Oil Diesel Oil
Heating Value
(kJ/kg) 43225.9 46199.12 45814.74
C (%) 84.67 83.79 87
H (%) 10.44 11.36 13
O (%) 4.17 2 -
Cl (%) n.a 0.03 n.a
S (%) 1 - -
Density @
30°C (g/cc) 0.924 0.8147 0.7994
Viscosity @
40°C (cp) 2.69 2.49 1-4.11
Flash Point
(°C) 68 100 70
3.2. Engine Break Power
Engine break power (P) is delivered by engine and ab-
sorbed load. It is the product of torque and angular en-
gine speed where P is engine break power in kW, N is
angular speed of the engine in rpm as:
60 1000
3.3. Break Specific Fuel Consumption
Break specific fuel consumption (bsfc) is the comparison
of engine to show the efficiency of the engine against
with fuel consumption of the engine in g/kW-hr where
is the fuel consumption rate in g/hr as:
bsfc P
3.4. Break Thermal Efficiency
The percentage of break thermal efficiency of the engine
) is related to engine break power (P) and the total
energy input to the engine which is QLHV lower heating
value of fuel in kJ/kg applied to the fuel consumption
rate as:
1000 100
th mQ
 
3.5. Experimental Detail
The characteristics of an engine used this experiment
which is a multi-purpose agricultural direct injection di-
esel engine (Kubota ET-70) are shown in Table 3.
Schematic of the experimental set up is shown in Fig-
ure 1. The engine equipped with measuring elements
including weighing device, manometer, orifice plate,
tachometer, thermocouple and black smoke meter at the
exhaust. As the experiment was run in constant speed,
the torque output from the experiment is measured by the
breaking force absorbed by the load. The absorbed load
is maximum 7 kW. The pure distilled plastic pyrolysis oil,
Table 3. Engine specification.
Engine Specification Kubota ET70
Bore X Stroke 78 mm. X 84 mm.
Swept Volume /Cylinder 401 cc.
Compression Ratio 23.5:1
Max.Torque @1800 rpm 22.56 Nm
Max. Output, HP/rpm 7 (5.15)/2200
Rated. Output, HP/rpm 6 (4.41)/2200
Copyright © 2013 SciRes. EPE
distilled tire pyrolysis oil and diesel oil were tested in
this experiment.
The experiments were conducted by starting engine
with the blended testing fuel. The operating conditions
were set at a rated engine speed 1500 rpm. Loads were
applied from 500 W and stepped up until reached the
maximum load. The air box and orifice plate flow meter
are applied for air flow measurement. Fuel consumption
is measured from the differential of the fuel in time. A
chromel-alumel thermocouple was installed to measure
the exhaust gas temperature. The engine was run for 5
minutes to reach the steady state of test condition before
collecting data. At the end of the test, the engine was run
with diesel fuel for sometime to flush out from the en-
1. Orifice Plate 2. Air box
3. Fuel Tank 4. Weighing Device
5. Tachometer 6. Engine
7. Black Smoke Meter, Thermocouple 8. Generator
9. Torque Meter 10. Load
Figure 1. Schematic of the experimental setup.
3.6. Engine Performance Result
The experimental result of the engine performance shows
the opportunity of using pyrolysis oil in diesel engine.
The variation of the break thermal efficiency with the
break power shows that the trend of thermal efficiency
performance of the tire pyrolysis oil and plastic pyrolysis
oil are comparable to diesel oil. The tire pyrolysis oil
offers higher efficiency in the medium load while the
plastic pyrolysis offers slightly lower efficiency. The
maximum load production from plastic pyrolysis oil is
the lowest which is 3,064 W where as the tire pyrolysis
oil produces 3,282 W and diesel produces 3,500 W as
shown in Figure 2. The trend lines of the plastic pyroly-
sis oil and diesel oil are similar in linear line unlike the
tire pyrolysis oil which is in parabolic curve.
It shows that the tire pyrolysis oil consists of aromatics
and complex compound which reflected in high effi-
ciency in the medium load. The variation of the break
specific fuel consumption with the break power in Fig-
ure 3 is also shown that both of the pyrolysis oil is ap-
plicable to use in diesel engine. The plastic pyrolysis oil
offer the lowest break specific fuel consumption at 294
g/kW-hr with maximum break power at 3,064 W. As
diesel engine is designated to apply with diesel oil, some
50010001500 20002500 3000 3500 4000
Tire Oil
Plastic Oil
Figure 2. The variation of the break thermal efficiency
with the break powe r.
500100015002000 2500 3000 3500 4000
Tire Oil
Plastic Oil
Figure 3. The variation of the break specific fuel consump-
tion with the break power.
properties in tire pyrolysis and plastic pyrolysis such as
density and viscosity might cause the less efficiency and
the limitation in combustion condition.
The engine exhaust gas temperature for plastic pyroly-
sis oil varies from 120℃ at low load to 225 at full
load where in case of tire pyrolysis oil varies from 119
at low load to 295 at full load and in case of diesel oil
varies from 119 at low load to 312at full load. The
experiment shows the combustion of diesel oil deliver
higher heating rate due to the ignition delay condition.
However, the performance of the use of plastic pyrolysis
oil could be enhanced by modifying the injection timing
of the engine [15].
Exhaust soot was measured in Bosch Smoke Units
(BSU) by a Bosch smoke meter. The smoke opacity of
the plastic pyrolysis oil is the highest which is varies
from 18% at no load to 97% at full load. The tire pyrolsis
oil is slightly higher than the diesel oil as fuels with
higher aromatics exhibit higher NOx and smoke at full
load [16]. The smoke opacity varies from 11% at no load
to 84% at full load for Diesel where as for tire pyrolysis
oil varies from 15% to 95%. The result reflects that the
best oil for engine is diesel oil. The plastic pyrolysis is
the lowliest while the tire pyrolysis is acceptable for the
engine use without modification.
Copyright © 2013 SciRes. EPE
4. Economic Analysis
Comparison of the use of two types of pyrolysis oils are
cannot be completed if the economic analysis concerning
the cost and sensitivity. Fuel costs are estimated regard-
ing the information from pyrolysis plant in Thailand. The
currency unit used in this research is in Thai Baht.
4.1. Fuel Production Cost Analysis
The investment and expenses of these two pyrolysis
plants are concerned and analyzed to estimate the pro-
duction cost of respectively oil as shown in Table 4.
Though the core technology of each plant is similar, the
characteristics of feedstock and product are slightly dif-
ferent. It is assumed that the feedstock input is 6 tons per
day. Plastic used is waste plastic from landfill site and
tire used is collected from garages.
Sorting system of plastic pyrolysis plant carry out
higher capital cost and feedstock expense but in return,
the amount of oil production is higher. The tire pyrolysis
plant require only shredding process but in return, it
produce less amount of oil compare to the same amount
of feedstock as the tire contains tire wire and high carbon
residue. The cost of plastic oil is slightly lower than tire
oil due to the production amount.
4.2. Energy Cost and Sensitivity Analysis
The fuel cost analysis is done under financial assumption
which is not concerning about efficiency output of oil.
Table 4. Pyrolysis oils cost estimation.
Type of Cost Unit Plastic Oil Tire Oil
Total Capital Cost Baht 9,000,000 6,000,000
Capital cost Baht/Day 24,658 16,438
Feedstock Expenses Baht/Day 30,000 8,000
Operation Expense Baht/Day 3,000 1,500
Maintenance Expenses Baht/Day 1,000 440
Labor Expense Baht/Day 3,000 2,000
Utilities Expense Baht/Day 1,000 1,000
Taxes, Insurance Baht/Day 450 200
Total Expenses Baht/Day 38,450 13,140
Profit 30% Baht/Day 11,535 3,942
Total production Baht/Day74,643 33,520
Oil production Liter/Day 4,500 2,000
Production cost Baht/Liter16.59 16.76
The cost might not applicable to all situations as the en-
gine performance result shows the diverse of efficiency.
Therefore, the indicator that is applicable to all situations
to predict the use of oil in terms of economic analysis
should be energy cost consumption per power output as:
bsfc Cost
where E is the cost of energy consumption per power
output in Baht/kW-hr,
PO is the density of calculating oil.
Equation (6) shows the cost of energy compared regard-
ing to the efficiency.
The energy consumption cost indicates that the use of
both tire pyrolysis oil and plastic pyrolysis oil is eco-
nomically comparable to diesel oil. Though the engine
performance is lower, the cost of fuel is significantly
lower as shown in Figure 4.
However, the sensitivity analysis of the fuel cost is
done and it is found that the both pyrolysis oil is suitable
to use as diesel replacement in terms of engine perform-
ance and economic analysis as long as the price of pyro-
lysis is less than 85% of diesel oil price.
5. Conclusions
The use of plastic pyrolysis oil and tire pyrolysis oil in
diesel engine in the aspect of technical and economical is
compared and found that both of the oils are able to re-
place the diesel oil.
Though the plastic pyrolysis oil offers lower engine
performance, the plastic waste amount is enormous and it
needed to be process to reduce the environmental prob-
lems. Moreover, the engine can be modify follow the
combustion condition of plastic pyrolysis oil. The waste
plastic used in the process must be PE or PP in order to
protect the contamination of chlorine in the oil.
Tire pyrolysis offers comparable efficiency to diesel
oil in medium to high load but it has been question on the
desulfurization process. Therefore, the development of
the tire pyrolysis oil is depending on the cost of desulfu-
rization process. Although the tire pyrolysis oil offer
Tire Oil
Plastic Oil
Figure 4. The variation of the energy cost consumption per
power output with the bre ak power .
Copyright © 2013 SciRes. EPE
Copyright © 2013 SciRes. EPE
better quality than plastic pyrolysis oil, the amount of
waste tire is minimal compare to plastic waste and the oil
production is less. Additionally, by product of the tire
pyrolysis plant carbon residue and tire wire from waste
tire, the plant entrepreneur need to find an opportunity to
process these by products due to the amount of the by
product is correspondent to the oil product.
Turning waste to energy is not only financial profit-
able but it also environmental friendly business which
the government should offer a strong policy to encourage
the entrepreneur to invest in the waste to energy busi-
6. Acknowledgements
The authors would like to acknowledge a tire pyrolysis
plant and a plastic pyrolysis plant to sponsor us the oils.
The authors are also grateful for the laboratory support of
Energy Technology Department, Thailand Institute of
Scientific and Technological Research. The research was
conducted by researchers in the pyrolysis research group,
in support of Rajamangala University of Technology
Phra Nakhon.
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