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© by PSP Volume 24 – No 4. 2015 Fresenius Environmental Bulletin
1215
LIFE CYCLE ASSESSMENT OF WASTE TIRE PYROLYSIS
Müfide Banar
Department of Environmental Engineering, Faculty of Engineering, İki Eylül Campus 26555, Anadolu University, Eskişehir, Turkey
ABSTRACT
In this study, in order to provide the input for decision-
makers in Turkey, the environmental impact of a waste tire
pyrolysis plant was researched using the Life Cycle As-
sessment (LCA) method. The functional unit is defined as
1 t of waste tires entering the pyrolysis process. The system
boundary, including feedstock pretreatment and pyrolysis,
was illustrated and material/energy flows, including raw
material, pyrolysis products were determined according to
a pilot pyrolysis plant and literature data. The LCA calcu-
lations were carried out using licensed SimaPro 8 software.
At the impact assessment step, the CML-IA baseline
(V3.00) method was applied for selected impact categories
(abiotic depletion, global warming, human toxicity, marine
aquatic toxicity, acidification and eutrophication). The char-
acterization results show that all the impact categories have
negative values, except for acidification. Negative values re-
sulting from avoided products were due to the valuable
products of pyrolysis. The acidification impact resulted
mainly from SO2 emissions in combustion flue gases. As a
summary, the results show that utilization of pyrolysis
products in sufficient quantities and the application of flue
gas treatment systems play an important role in presenting
pyrolysis as an environmentally effective solution for
waste tires.
KEYWORDS: life cycle assessment (LCA), pilot pyrolysis plant, py-
rolysis, simapro 8, waste tire
1. INTRODUCTION
The remarkable worldwide increase in the number of
vehicles, and a lack of both technical and economical dis-
posal mechanisms made for waste tires are being consid-
ered as a serious pollution problem [1]. It is estimated that
1.5 billion tires are produced worldwide each year, most of
which will eventually end up as waste. In terms of tonnage,
waste tires represent a significant proportion of the total
solid waste stream. For example, approximately 3.3 million
tonnes of waste tires were generated annually within Europe
(EU-27) in 2010, with an estimated stockpile of 5.7 million
tonnes of waste tires throughout Europe. The management
of waste tires in the European Union has been regulated
under the ‘End of Life Vehicle Directive’, which stipulates
the separate collection of tires from vehicle dismantlers,
and encourages the recycling of tires. In addition, the EU
‘Waste Landfill Directive’ has banned the landfilling of
tires. These directives have changed direction of waste tire
treatment in the EU over the last 15 years. For example, in
1996, approximately 50% of waste tires were sent to land-
fills; however, currently the figure is only 4% (0.13 million
tonnes/year) [2].
The management of waste tires is intended to follow a
hierarchical approach, that is, to decrease the environmen-
tal impact according to the following order: waste minimi-
sation, reuse, recycling, energy recovery, and landfilling.
Legislation related to waste management requires the
search for economical and environmental mechanisms that
can contribute solving this waste disposal problem. Waste
tire disposal in landfills is banned in the EU, with minimi-
sation and reuse being options with only limited applica-
bility, and recycling being insufficient to mitigate the dis-
posal problem by itself. Therefore, energy recovery seems
to have a high potential to process and to valorize waste
tires. Thermochemical processes, such as pyrolysis, gasifi-
cation and combustion, offer important advantages from an
energy point of view to address this challenge. More than
1.15 million tonnes of waste tires (>3.3 million tonnes) are
used as fuel in cement kilns each year in the EU. Other en-
ergy recovery options for tires include use in power plants
and co-incineration with other wastes, which use approxi-
mately 0.1 million tonnes per year of tires. Approximately,
1.1 million tonnes of tires are used in material recovery op-
tions through the production of rubberised flooring for
sports fields and playgrounds, paving blocks, roofing ma-
terials etc. A significant proportion of waste tires are used
in civil engineering applications, such as road and rail
foundations and embankments (0.24 million tonnes), re-
treads (0.26 million tonnes), or are exported (0.33 million
tonnes) each year [1-3].
Other treatment alternatives are based on thermal tech-
nologies. Pyrolysis is becoming one of the best thermal al-
ternatives for waste tires. Pyrolysis of tyres is viewed as an
environmentally attractive and viable technological route
for the recycling of scrap tyres that, depending on market
conditions, all products of the pyrolysis process, the char,
oil, gas and residual steel may have an end use [4]. Table 1
shows examples of commercial and semi-commercial tire
pyrolysis systems around the world. The table shows some
examples, rather than an exhaustive list of the wide range of
companies which have developed tire pyrolysis technologies.
© by PSP Volume 24 – No 4. 2015 Fresenius Environmental Bulletin
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TABLE 1 - Examples of commercial and semi-commercial tire pyrolysis systems [2]
Company Location Reactor Type Capacity (tons/day)
Splainex Ltd The Hague, Netherlands Rotary kiln approx. 20
Xinxiang Doing Renewable Energy Equipment Co., Ltd Xinxiang, China Rotary kiln 6–10
RESEM Shangqui, China Rotary kiln 8–20
Kouei Industries Vancouver, Canada Fixed bed/Batch 16
DG Engineering Gummersbach, Germany Rotary kiln approx.10
FAB India Amedabad, India Rotary kiln 5–12
Octagon Consolidated Selangor, Malaysia Rotary kiln 2.4–120
No-Waste Technology Reinach, Germany Fixed bed/Batch 4
PYReco Teeside, UK Rotary kiln 200
Pyrocrat Systems Navi Mumbai, India Rotary kiln 2–10
Batch tire pyrolysis reactors have throughputs of typi-
cally between 1–2 tonnes per day, and for increased through-
puts, additional modules could be added. For larger through-
puts, continuous tire pyrolysis reactors have been developed,
the most common being rotary kiln reactors [2].
In Turkey, annual tire production numbers reach ap-
proximately 24 million units. In addition, annually, 8 mil-
lion units of waste tires are generated. Despite such large
quantities, the number of recovery and disposal facilities
for waste tires are limited [5]. The Ministry of the Environ-
ment and Urban has granted licenses to 22 recovery facili-
ties between 2006-2013. This corresponds to a total capac-
ity of 113,500 tons/year. The recovery of waste tires as
granulated material is not sufficient for effective treatment.
In relation to this, The Regulation on Control of End of Life
Tires came into force in 2006 (Official Gazette of 25 No-
vember 2006, number 26357) [6]. This regulation aims to
prevent direct and indirect delivery of waste tires to recep-
tor platforms which may harm the environment, the instal-
lation of collection and carriage of tires for recycling or
disposal, and to establish a management plan. According
to this regulation, plants, which produce carbon black from
waste tires via pyrolysis, have to have an environment li-
cense. However, there are no environmental limit values
for gaseous emissions resulting from the pyrolysis of waste
tires. Hence, unique regulations for pyrolysis plants do not
exist in Turkey, and limit values for gaseous emissions re-
sulting from waste combustion plants are taken into ac-
count for pyrolysis plants (Large Combustion Plants Reg-
ulation, Official Gazette of 8 June 2010, number 27605,
Regulation on Control of Industrial Air Pollution, Official
Gazette of 3 July 2009, number 27277) [7].
LCA is a valuable tool for providing an overall evalu-
ation or comparison of any potential environmental impact
of various waste management technologies. However, a
limited number of LCA studies on the pyrolysis of waste
tires have been investigated. Li et al. (2010) [8] compared
the potential environmental impact of four different end of
life tire (ELT) treatment technologies in China. Corti and
Lombardi (2004) [9] used life cycle assessment to compare
different processes for the end life treatment of exhausted
tires. For that reason, this study aims to determine the en-
vironmental impact of waste tire pyrolysis in the context of
a pilot plant using the LCA method. To the best of our
knowledge, this is the first LCA study on waste tire pyrol-
ysis in Turkey. Therefore, the findings of this study should
help decision-makers and practitioners in Turkey, and also
would make a genuine contribution with real plant data to
the related literature.
2. MATERIALS AND METHODS
This study was conducted according to standard LCA
guidelines (TSE EN ISO 14040:2006 and TSE EN ISO
14044:2006) developed by the International Organization
for Standardization [10, 11]. The LCA study was consid-
ered under three sections: the goal and scope definition
(functional unit, system description and system bounda-
ries), life cycle inventory (data collection and allocation
procedure), and life cycle impact assessment.
2.1 Goal and scope definition
The aim of the study is to evaluate the potential envi-
ronmental impact of waste tire pyrolysis in Turkey using
pilot pyrolysis plant data. The functional unit is defined as
1 ton of waste tires entering the pyrolysis process.
2.2 System description
The system that was modeled in the LCA method is
based on a pilot pyrolysis plant. This plant (Aker Bioen-
ergy, http://akerbioenerji.com) was established in the prov-
ince of Adapazarı/Sakarya. Adapazarı is an industrial city
in the Marmara Region of Turkey, 55 km from the Mar-
mara Sea.
The process includes pre-treatment (shredding and
grinding) and pyrolysis processes. In the pre-treatment pro-
cess, waste tires are separated into 3 groups: truck tires,
passenger tires and working machine tires. Before shred-
ding, the sidewall wires of the truck tires are removed with
© by PSP Volume 24 – No 4. 2015 Fresenius Environmental Bulletin
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a drawing machine, and working machine tires are cut into
large pieces using a hydraulic cutting device. A drawing
machine is not applicable for working machine tires, since
they have thicker wires, with a diameter of 9-10 cm. The
hydraulic cutting device helps to divide a working machine
tire into 5 pieces to extract the wires. Next, truck tires with-
out wires, cut working machine tires and raw passenger tires
are fed into the shredder together. The chips enter a grinder
to obtain rubber granules of a suitable size for pyrolysis.
In the pyrolysis process, rubber granulates of 20 mm
are fed into a pyrolysis reactor. Pyrolysis is achieved by a
horizontal rotary batch reactor. The pyrolysis temperature
is 400 °C. The reactor reaches this temperature after ap-
proximately 3 h, remains constant for 4 h, and returns to its
initial temperature after a further 4 h. So, a batch pyrolysis
takes about 11 h. The output of this process consists mainly
of 3 fractions: gaseous fraction (hydrogen, methane and
carbon oxides), liquid fraction (water, tar and oils), and a
solid product (char, ash and metals). The average yield
(weight %) of products as measured in the pilot plant was
as follows: gas = 15%, pyrolysis oil = 41%, solid product
= 32%, and steel = 12%.
2.3 System boundaries
The system boundaries that were considered in this
LCA analysis are shown in Fig. 1, based on the system de-
scription and the assumptions given below:
Production and use phases were not considered in this
study, since the feed of the pyrolysis is waste. Simi-
larly, the transport of waste tires was not considered,
since the aim was to assess the pyrolysis process.
For the waste tire treatment process, with regards to
the impact related to the life cycle of materials and
fuels required during the processes, only electric
power generation and heating oil consumption were
considered.
Secondary waste transport and treatment (such as land-
filling) were excluded from the system boundaries.
Infrastructure was also excluded from the system
boundaries.
Negative environmental effects were considered for
the avoided materials.
As seen in Fig. 1, the total environmental impact, re-
garding waste tire pyrolysis, consists of 3 components: in-
direct impact caused by energy and the material production
stage, direct impact caused by waste tire pyrolysis, and
avoided impact caused by valuable products (recycled ma-
terial and energy).
2.4 Life cycle inventory
The life cycle inventory (LCI) is an inventory analysis
to identify input (materials and energy), output (emissions)
and data quality, which play an important role in LCA re-
sults. Primary data on the input (electricity and heating oil
consumption) and output (pyrolysis gas composition, py-
rolysis products and other products) were mainly obtained
from the pilot pyrolysis plant (Aker Bioenergy). SimaPro
8 software was used to develop and link primary unit pro-
cesses. Secondary data were gathered from the EcoInvent
(v2.2-v.3.0.3) database which is embodied in SimaPro 8.
FIGURE 1 - System boundaries
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2.5 Energy and material requirement
According to the pilot pyrolysis plant electricity con-
sumption data, the average amount of electricity required
for production is 155.51 kWh per ton of waste tires. This
consumption quantity includes a pre-treatment (drawing
machine, hydraulic cutting device, shredder and convey-
ors), cooling equipment, valves, scrubber, grinding, carbon
treatment unit, gas storage and packaging unit. Turkey’s
grid mix electricity profile was compiled in SimaPro 8 us-
ing a breakdown of Turkey’s grid electricity primary en-
ergy sources in 2011 (45% natural gas, 29% lignite coal,
23% hydraulic, 2.5% wind and 0.5% geothermal) by Banar
et al. (2013) [7]. In this study, this profile was used for
electricity data.
Heating oil is used for the start-up (for the first 3 h)
until the system produces its own gas. In this study, heating
oil was considered as fuel oil no.4 that has an average heat-
ing capacity of 9700 kcal/kg and a C content of 85%. In
SimaPro 8, light fuel oil, at refinery/CH U data was used
for fuel oil no.4.
2.6 Emissions from pyrolysis gas combustion
Pilot pyrolysis plant gas product efficiency is normally
15% by weight. Pyrolysis gas is used as a fuel by feeding
back into the pyrolysis process. The averaged chemical
composition of pyrolysis gas measured at the pilot plant is
given in Table 2. The density of the pyrolysis gas was de-
termined to be 0.895 kg/m3 using the volume percentages
and densities of the components at Normal Temperature &
Pressure (NTP). In addition, the Gross Calorific Value
(GCV) of pyrolysis gas was determined to be 42.54 MJ/kg
(38.10 MJ/m3) from Table 2. This GCV value of the pyrol-
ysis gas is in the range of 37.85–40.72 MJ/m3 reported by
Islam et al. (2011) [12].
The total CO2 emission amount was calculated to be
68.06 (kg/ton waste tire pyrolysis). Details of the calcula-
tion are given in Table 3. This calculated amount is con-
sistent with the amount (60kg CO2/t tires treated) reported
by Li et al. (2010) [8].
SO2, NOx and dust emission data (3.55 kg SO2, 1.40 kg
NOx and 0.58 kg dust per 1 t of waste tire pyrolysis) were
obtained from Li et al. (2010) [8].
TABLE 2 - The averaged chemical composition of pyrolysis gas.
Component % (volume)
Methane 32.93
Hydrogen 21.10
Ethane 13.06
Carbon dioxide 12.05
Carbon monoxide 6.40
Propane 5.14
Propene 3.77
Ethylene 1.93
1-Butene 1.26
2-Fumaric acid 1.26
Butane 0.90
Nitrogen 0.85
Isobutane 0.30
Cis-2-butene 0.08
Pentane 0.06
Hydrogen chloride <0.01
Hydrogen sulfite <3 (mg/m3)
2.7 Allocation
There is a need for allocation to consider the benefits of
pyrolysis processes modelled in this study. According to ISO
14044, allocation should be avoided by dividing processes
into subprocesses, or by expanding the system boundary so
that co-products are included in the system. In this study, al-
location was avoided by expanding the system boundary with
avoided products given in the following section.
TABLE 3 - CO2 emission calculation steps.
The capacity of batch reactor 12 t /batch
Capacity of the burner 301,000 kcal/h
Total operation time 11 h
Total CO2 generation for 1 t of waste tires pyrolysis 68.06 kg CO2
Heating oil combustion calculation
Operation duration with heating oil 3 h
GCV of heating oil 9700 kcal/kg
Heating gas consumption for 1 t waste tires pyrolysis 93 kg
C content of heating oil 85%
CO2 generation from combustion of heating oil 24.18 kg CO2
Pyrolysis gas combustion calculation
Operation duration with pyrolysis gas 8 h
GCV of pyrolysis gas 38.10 MJ/m3
Heating requirement for 1 t waste tire pyrolysis supplied by pyrolysis gas 838.79 MJ
Pyrolysis gas consumption for 1 t waste tires pyrolysis 22.02 m3
Produced pyrolysis gas volume from 1 t waste tires pyrolysis 167.51 m3
The percentage of recovered pyrolysis gas for 1 t waste tires 13.14%
The total C amount in the recovered pyrolysis gas 80.83 kg
CO2 generation from combustion of pyrolysis gas 43.88 kg CO2 *
*89% from hydrocarbons and 11% from pyrolysis gas own CO2
© by PSP Volume 24 – No 4. 2015 Fresenius Environmental Bulletin
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2.8 Avoided products from valuable products
There are 4 kinds of valuable products produced from
waste tire pyrolysis: pyrolysis gas, pyrolysis oil, solid
product, and steel. Because the recycled material may not
be accepted as a full substitution of the same amount of
virgin material due to decline in its physical/chemical prop-
erties, a substitution factor between certain recovered and
virgin material should be assumed. Pyrolysis valuable
products and their substitutes are explained with their sub-
stitution factors below:
Pyrolytic oil can substitute diesel, which is used in sta-
tionary diesel generators. The GCV value is an im-
portant parameter to utilize an alternative fuel. The el-
emental composition and GCV value of the pyrolytic
oil were determined using a LECO CHN and S and
IKA C200 calorimeter (ASTM D-5865), respectively.
The comparison of the results with diesel are listed in
Table 4. The GCV of pyrolytic oil is slightly lower
than that of diesel. The higher nitrogen in the pyrolytic
oil comes from the initial introduction of nitrogen to
the pyrolysis system, and the sulfur content in the py-
rolytic oil comes from the origin of tire.
TABLE 4 - The comparison of pyrolytic oil with diesel.
Parameter Pyrolytic oil Diesel
Elemental analysis (% wt.)
C 86.74 87.4
H 10.41 12.1
N 0.52 370 ppm
S 1.15 1.39
Oa 1.18 2.1
GCV (MJ/kg) 40.37 45.5
a by difference
On the other hand, the cetane number (CN) is another
important parameter that has to be carefully considered
when an unconventional fuel is used inside a compression
ignited engine. When the traditional CN cannot be directly
measured, it is possible to make a good estimation of it, by
calculating the cetane index (CI) [14]. The CI is calculated
from the formula given below (ASTM D976-06).
454.74 1641.416 774.74
0.544 97.803 (1)
In this equation, D is the fuel density at 15 °C (g/ml)
and T50 is the mid-boiling temperature (°C) corresponding
to a 50% point in the distillation curve. In this study, the CI
of the pyrolysis oil was calculated by combining the pilot
plant data and the experimental data. The density (15 °C)
of the pyrolytic oil was reported as 925.6 kg/m3 by the pilot
pyrolysis plant. Banar et al. (2012) [13] measured the T50
of the tire pyrolysis oil as 250.1 °C for a pyrolysis heating
rate of 5 °C/min. By using these values, the CI value of the
pyrolysis oil was estimated to be 25.6. This calculated CI
value is close to Frigo et al. (2014) [14] who found a CI of
27. According to ASTM D975-13a, the minimum CI value
of diesel fuel should be 40. At this point, it was not practi-
cal to substitute 100% pyrolysis oil for diesel fuel, although
the GCV values of the pyrolysis oil and diesel fuel are
close. Based on this explanation, it was concluded that 1 kg
of pyrolytic oil can substitute 0.5 kg of commercial diesel
fuel. Diesel, at refinery/RER U data, was used for the
avoided diesel.
The solid product that exits in the pyrolysis reactor
contains both carbon black and the steel from the tires.
For the solid product, scrap steel and carbon black are
separated using a 3-step magnet process. The latter is
then ground and packed. Carbon black obtained from
pyrolysis only can substitute any commercial carbon
black in the case of a further acid treatment because of
its high ash and sulphur contents (12.14 and 1.71%,
respectively) [15]. For this reason, it was assumed that
1 kg of pyrolytic carbon black can substitute 0.5 kg of
commercial carbon black, which is produced by the
oil-furnace method. Carbon black, at plant/GLO U
data, was used for commercial carbon black.
The separated steel in the pre-treatment process was
shipped to recycling, together with the scrap steel re-
moved from the solid product. The substitution rates
of this recovered steel were quantified as 1:1 for
avoided steel production. According to a web search
for steel wire producers for tires, it was found that high
carbon steel wire rods are used to reinforce the dura-
bility of automobile tires. For this reason, steel, low-
alloyed, at plant/RER U data, was used for avoided
steel.
2.9 Life cycle impact assessment
The LCA calculations were carried out using licensed
SimaPro 8 software. In the impact assessment step, the
CML-IA baseline (V3.00) method was applied. The CML-
IA baseline method is an update of the CML 2 baseline
2000, and elaborates the problem-oriented (midpoint) ap-
proach. Normalization results were also calculated using
the EU25+3, 2000 calculation method under the CML-IA
baseline (V3.00) method. In addition, the modeled system
was analyzed by excluding infrastructures.
3. RESULTS AND DISCUSSION
The characterization and normalization results of all
impact categories in the CML-IA baseline (V3.00) method
are given in Table 5. As seen in Table 5, all the impact cat-
egories have negative values, except acidification. Nega-
tive values result from avoided products from valuable
products. Normalization values can help to compare the
impact of the different categories. According to the nor-
malization results, it can be concluded that acidification
and marine aquatic ecotoxicity impact categories are the
endpoints of the total impact that represent the environ-
mental effects and avoided effects, respectively. Six impact
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TABLE 5 - Characterization and normalization results.
Impact category Characterization Normalization
Unit Amount
Abiotic depletion (element) kg Sb eq. -2.39E-03 -1.44E+04
Abiotic depletion (fossil fuels) MJ -2.16E+04 -7.58E+17
Global warming (GWP100a) kg CO2 eq. -5.10E+02 -2.66E+15
Human toxicity kg 1,4-DB eq. -7.78E+02 -3.89E+14
Marine aquatic ecotoxicity kg 1,4-DB eq. -3.63E+05 -1.61E+19
Acidification kg SO2 eq. 2.92E+00 4.90E+10
Eutrophication kg PO4--- eq. -3.91E-01 -7.23E+09
Fresh water aquatic ecotoxicity kg 1,4-DB eq. -2.54E+02 -5.30E+13
Terrestrial ecotoxicity kg 1,4-DB eq. -6.56E-01 -7.61E+10
Ozone layer depletion (ODP) kg CFC-11 eq. -2.66E-04 -2.71E+03
Photochemical oxidation kg C2H4 eq. 5.15E-03 8.91E+06
(a)
(b)
FIGURE 2 - AD impact of 1 ton of waste tire pyrolysis: a) ADe impact, and b) ADff impact.
-2,50E-03
-2,00E-03
-1,50E-03
-1,00E-03
-5,00E-04
0,00E+00
5,00E-04
kg Sb eq.
Nickel
Chromium
Molybdenum
-1,50E+04
-1,20E+04
-9,00E+03
-6,00E+03
-3,00E+03
0,00E+00
3,00E+03
6,00E+03
MJ
Crude oil
Natural gas
Coal
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categories were further investigated: abiotic depletion (el-
ement and fossil fuel), global warming, acidification, eu-
trophication, human toxicity, and marine aquatic toxicity.
Fresh water aquatic ecotoxicity and terrestrial ecotoxicity
were excluded from further investigation, since marine
aquatic ecotoxicity was the dominant impact of the ecotox-
icity impact.
3.1 Abiotic depletion
Abiotic depletion (AD) was investigated under two
subcategories: the abiotic depletion element (ADe) (Fig.
2a) and abiotic depletion fossil fuel (ADff) (Fig. 2b). Fig-
ure 2a shows that there is a significant saving for ADe from
steel alloy production elements due to avoided steel pro-
duction. From the point of view of ADff, as expected, there
are remarkable savings for crude oil and coal consumption
due to avoided diesel, carbon black and steel production
(Fig. 2b). On the other hand, heating oil production causes
abiotic depletion, entirely due to the crude oil
3.2 Global warming
The GWP (100a) impact of 1 t of waste tire pyrolysis
is shown in Fig. 3. As can be seen, there are savings for the
GWP value due to the avoided production of diesel, carbon
black and steel. CO2 accounts for over 95% of the total
avoided impact. In the foreground, the highest saving is in
the carbon black production while in the background, the
saving is because of avoided crude oil used in the oil-fur-
nace method. Beside the saving resulting from avoided
products, there are also positive impacts. The combustion
of pyrolysis gas and heating oil during the pyrolysis pro-
cess accounts for 49.7% of the total positive GWP (100a)
impact. The production of heating oil and electricity con-
tributes 27.5 and 22.8% to the total positive GWP, respec-
tively.
3.3 Human toxicity
Figure 4 shows the human toxicity impact of 1 t of
waste tire pyrolysis. From Fig. 4, it can be seen that there
is a saving of the human toxicity impact, mainly from
avoided Chromium VI generation during the steel produc-
tion.
3.4 Marine aquatic toxicity
The marine aquatic toxicity impact of 1 t of waste tire
pyrolysis is demonstrated in Fig. 5. As can be seen in Fig. 5,
in the foreground, there is a remarkable negative impact
due to avoided steel production. In the background, beryl-
lium, cobalt, hydrogen fluoride, nickel and vanadium emis-
sions generated from steel production were avoided. Ex-
cept for these, only heating oil and electricity production
caused a positive marine aquatic toxicity impact at very
low values.
3.5 Acidification
The distribution of the acidification impact resulting
from 1 t of waste tire pyrolysis into the subprocesses is
shown in Fig. 6. Among the subprocesses, pyrolysis has the
highest acidification impact, mainly due to the acidifica-
tion potential of SO2 and NOx emissions in combustion flue
gases. The negative impact is due to the avoided generation
of SO2 resulting from diesel, carbon black and steel.
FIGURE 3 - GWP (100a) impact of 1 ton of waste tire pyrolysis.
-4,00E+02
-3,00E+02
-2,00E+02
-1,00E+02
0,00E+00
1,00E+02
kg CO2eq.
Carbon dioxide
Methane
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FIGURE 4 - Human toxicity impact of 1 ton of waste tire pyrolysis.
FIGURE 5 - Marine aquatic toxicity impact of 1 ton of waste tire pyrolysis.
-8,00E+02
-6,00E+02
-4,00E+02
-2,00E+02
0,00E+00
2,00E+02
kg 1,4-DB eq.
Chromium VI
Vanadium
Barium
Selenium
Nickel
-4,00E+05
-3,00E+05
-2,00E+05
-1,00E+05
0,00E+00
1,00E+05
kg 1,4-DB eq.
Vanadium
Selenium
Nickel
Hydrogen fluoride
Cobalt
Beryllium
Barium
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FIGURE 6 - Acidification impact of 1 ton of waste tire pyrolysis.
FIGURE 7 - Eutrophication impact of 1 ton of waste tire pyrolysis.
-2,00E+00
0,00E+00
2,00E+00
4,00E+00
6,00E+00
kg SO2eq.
Sulfur dioxide
Nitrogen oxides
-5,00E-01
-4,00E-01
-3,00E-01
-2,00E-01
-1,00E-01
0,00E+00
1,00E-01
2,00E-01
kg PO4--- eq.
Phosphate
Nitrogen oxides
Nitrate
COD, Chemical Oxygen
Demand
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3.6 Eutrophication
Figure 7 shows the eutrophication impact of 1 t of
waste tire pyrolysis. In the foreground, the impact is mainly
due to NOx emissions in the combustion flue gases. There
is a noticeable negative impact on avoided steel produc-
tion. This negative value was sustained by the avoided NOx
and phosphate emissions. The avoided NOx emissions also
sustain negative eutrophication values on avoided diesel
and carbon black production. Additionally, diesel produc-
tion is also significant for eutrophication, due to the
avoided pollutants which cause a COD.
3.7 Sensitivity analysis
In the sensitivity analysis, the parameters with poten-
tially impact on the overall results were investigated: diesel
substitution rate, carbon black substitution rate, and im-
proved flue gas treatment. Two different substitution rates
(0.1 and 0.25), worse than baseline case (0.5), for diesel
and carbon black were considered. The SOx, NOx and dust
emission data regarding to waste tire pyrolysis represent
the average technology tire pyrolysis plant that sustains the
limits of air contol legislations. Most of the average tech-
nology flue gas treatment systems have, at least, a flue gas
desulphurization (FGD) unit, and this FGD system in-
cludes a wet scrubbing using a slurry of alkaline sorbent.
Wet scrubbers are also effective for particulates removal.
SO2 and particulates (PM10) removal efficiencies using al-
kaline sorbents range between 95-99% and 80-95%, re-
spectively [16]. Although the wet FGD system has experi-
enced high SO2 and particulates removal efficiencies, that
is not so for NOx. For that reason, instead of a post-com-
bustion system, an improved control technology for NOx
removal was considered in terms of flue gas treatment. In
that case, replacement of the conventional gas burner in the
system with a Low NOx Burner (LNB) was investigated.
The reasons for the selection of LNB system are very low
nitrogen content of pyrolysis gas, low operational cost than
other NOx removal systems, such as Selective Catalytic
Reduction (SCR). LNBs can reduce NOx by 50% [17-19]
On the other hand, to select a SCR system would not be so
meaningful for a small plant that will only burn the excess
of pyrolysis gas. As a summary, a sensitivity analysis with
NOx emission reduction by 50% was performed to deter-
mine the improved flue gas treatment on the environmental
profile of the system.
Each assumption was changed independently of all
others; therefore, the magnitude of its effect on the baseline
case could be assessed. The assumptions considered in the
sensitivity analysis and their corresponding effects on the
baseline case are shown in Table 6. It is concluded from
Table 6 that decreasing the substitution factor for diesel
and carbon black increases the impact categories values
(max. 37% for diesel and max. 58% for carbon black).
Substitution factor has remarkable influences on the abiotic
depletion, global warming, acidification and eutrophication
TABLE 6 - Results of sensitivity analysis for assumptions.
Impact categories
% Change in characterization results of impact categories*
Parameters**
A B C
s.f.=0.1 s.f.=0.25 s.f.=0.1 s.f.=0.25 50% NOx red.
Abiotic depletion (element) 0.04 0.02 0.00 0.00 0.00
Abiotic depletion (fossil fuels) 36.48 22.80 47.17 29.48 0.00
Global warming (GWP100a) 13.15 8.22 57.06 35.66 0.00
Human toxicity 1.71 1.07 1.01 0.63 -0.11
Marine aquatic ecotoxicity 5.90 3.68 2.36 1.48 0.00
Acidification 30.69 19.18 26.50 16.56 -11.99
Eutrophication 25.92 16.20 14.60 9.12 -23.28
* Changes in characterization results are expressed as a percentage of the baseline case; ** Parameters - A: Substitution of pyrolytic oil for diesel,
substitution factors = 0.1 and 0.25, B: Substitution of pyrolytic solid product for carbon black, substitution factors = 0.1 and 0.25, C: Improved
gas treatment system, 50% reduction on the emissions of NOx).
TABLE 7 - Comparison results
Impact categories Unit Amount (2):(1)
This study
(1) Li et al. [8]
(2)
Climate change DALY -1.07E-04 -1.17E-04 1.09
Respiratory organics DALY -5.21E-07 -2.00E-07 0.38
Respiratory inorganics DALY -1.70-04 -4.20E-05 0.25
Carcinogens DALY -1.01E-04 -1.14E-05 0.11
Acidification / Eutrophication PDF*m2yr 5.31E+00 1.00E+01 1.88
Ecotoxicity PAF*m2yr -5.38E+02 1.00E+00 -0.001
Fossil fuels MJ surplus -2.82E+03 -1.57E+03 0.56
DALY: Disability adjusted life years; PDF: Potentially disappeared fraction of plant species; PAF: Potentially af-
fected fraction; * the rounded value of -0.00186.
© by PSP Volume 24 – No 4. 2015 Fresenius Environmental Bulletin
1225
for both diesel and carbon black. On the other hand, NOx
emission reduction influences acidification and eutrophi-
cation by the changes of 12 and 23%, respectively.
3.8 Comparison of the results
Life cycle assessments are always associated with un-
certainties, especially when data is not obtained directly
from a specific plant [20]. However, in this study, most
data represent the plant-specific data. For this reason, a
sensitivity analysis was performed in terms of different im-
pact categories using the EcoIndicator 99 method. The re-
sults were compared with the findings of Li et. al. (2010)
[8], which were also based on real plant data (Table 7). As
can be seen in Table 7, the ratios of the results are in the
range of 0.1-1.9, except for ecotoxicity. Ecotoxicity values
show a significant difference. This difference mainly re-
sults from power generation. Ranging of the negative val-
ues results from avoided products.
4. CONCLUSIONS
In this study, the environmental impact of waste tire
pyrolysis was determined in the context of a pilot plant us-
ing the LCA method. The results of the study illustrate that
there are large savings from waste tire pyrolysis in terms of
material and emissions, due to the substitution of pyrolysis
products (solid product-carbon black and pyrolysis oil-die-
sel). Sensitivity analysis indicated the importance of sub-
stitution rate on the savings.
The savings are listed in more detail below:
Steel alloy production elements, crude oil and coal
consumption due to avoided diesel, carbon black and
steel production.
A GWP impact due to avoided production of diesel,
carbon black and steel (CO2 is the main avoided emis-
sion.
A human toxicity impact resulting from the steel pro-
duction (chromium VI generation is a mainly avoided
emission).
A marine aquatic toxicity impact generated from the
steel production (beryllium, cobalt, hydrogen fluoride,
nickel and vanadium are the avoided emissions).
An acidification generation from the diesel, carbon
black and steel production (SO2 is the mainly avoided
emission).
An eutrophication impact due to diesel and carbon
black production (NOx and phosphate emissions and,
in addition, a COD parameter are the avoided effects).
On the other hand, with respect to the environmental
savings, this study shows that waste tire pyrolysis also has
an environmental impact:
Heating oil production causes abiotic depletion en-
tirely due to the crude oil.
The production of heating oil and electricity contrib-
utes 27.5 and 22.8% to the total positive GWP, respec-
tively.
The combustion of pyrolysis gas and heating oil during
the pyrolysis process accounts for 49.7% of the total
positive GWP (100a) impact.
Pyrolysis has an acidification impact, due mainly to
the acidification potential of SO2 emissions in combus-
tion flue gases.
NOx emissions in the combustion flue gases cause
acidification and eutrophication. Sensitivity analysis
shows that a 50% NOx emission reduction resulted in
a decrease of acidification and eutrophication by 12
and 23%, respectively.
As a consequence of this LCA study, in the light of the
sensitivity analysis, the results show that the sufficient uti-
lization of pyrolysis products and the application of flue
gas treatment systems play an important role in demon-
strating that pyrolysis is an environmentally effective solu-
tion for waste tires.
This is the first LCA study on waste tire pyrolysis in
Turkey. Therefore, the finding of this study could help de-
cision-makers and practitioners by providing a framework
to better understand the major environmental effects of
waste tire pyrolysis and conversion to useful products.
The author has declared no conflict of interest.
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Received: June 26, 2014
Revised: August 12, 2014
Accepted: September 29, 2014
CORRESPONDING AUTHOR
Müfide Banar
Department of Environmental Engineering
Faculty of Engineering
İki Eylül Campus
Anadolu University
26555 Eskişehir
TURKEY
Phone: +90.222.321 35 50/6400 (ext.)
Fax: +90.222.323 95 01
E-mail: mbanar@anadolu.edu.tr
FEB/ Vol 24/ No 4/ 2015 – pages 1215 - 1226
