Choice of emission factors

This section includes a discussion of the choice of emission factors for the Tier 1 method. The Tier 2 method is based on mass balance principles and the Tier 3 method is based on plant-specific data; therefore there are no default emission factors applicable to the Tier 2 and Tier 3 methods.

Table 3.11

Petrochemical production Tier 1 default feedstocks and processes

Petrochemical Process

Default Feedstock

Default Process

Methanol

Natural Gas

Conventional steam reforming without primary reformer

Ethylene

North America, South America,

Australia - Ethane

Other Continents - Naphtha

Steam cracking Steam cracking

Ethylene Dichloride / Vinyl Chloride Monomer

Ethylene

Balanced Process for EDC production with integrated VCM production plant

Ethylene Oxide

Ethylene

Catalytic Oxidation, Air Process, with thermal treatment

Acrylonitrile

Propylene

Direct Ammoxidation with secondary products burned for energy recovery or flared

Carbon Black

Carbon black feedstock and natural gas

Furnace black process with thermal treatment

TIER 1

Tier 1 emission factors for CO2 emissions and CH4 emissions for petrochemical products are provided below. Tier 1 emission factors for CO2 emissions do not include carbon emitted as CO, CH4, or NMVOC. Separate Tier 1 emission factors are provided for CH4 emissions from petrochemical processes. Tier 1 emission factors are not provided for carbon monoxide and NMVOC emissions.

The Tier 1 method allows for the selection of a 'default' feedstock and 'default' process in instances where activity data are not available to identify the feedstock or the process utilised to produce the petrochemical. Table 3.11 provides the default feedstocks and default processes for each petrochemical production process. In the event that no activity data are available concerning the specific processes and feedstocks used within a country to produce the petrochemical, the default process and default feedstock identified in Table 3.11 and the associated Tier 1 emission factors identified in the subsequent tables in this section are used to estimate the CO2 emissions from the petrochemical production process. Country-specific emission factors may be used instead of the default emission factors if country-specific factors are available.

Methanol

Carbon dioxide emissions

Emissions of CO2 from methanol production from the steam reforming and partial oxidation processes may be estimated by applying the default process feedstock emission factors, or the feedstock-specific and process-specific emission factors in Table 3.12, to activity data for methanol production, process configuration and process feedstock. The default emission factors are based on the average of plant-specific CO2 emissions data reported for four methanol plants using the conventional steam reforming process without primary reformer and using natural gas feedstock. Emissions data used in developing the default CO2 emission factor were reported for conventional process methanol plants in New Zealand, Chile, and Canada and in the Netherlands. Emission factors in the table include both the CO2 emissions arising from the process feedstock and the CO2 emissions arising from feedstock combusted within the steam reforming process. Table 3.13 summarises the total feedstock consumption, in units of GJ/tonne methanol produced, for the various methanol production process configurations and feedstocks shown in Table 3.12.

The conventional reforming process can include a single reformer unit or both a primary reformer unit and a secondary reformer. The emission factors differ depending upon the number of reformer units. Lurgi is a provider of methanol process technology and has published emission factors for several conventional reforming process technologies, see Table 3.12. The production capacity of Mega Methanol plants is generally greater than 5 000 tonnes per day of methanol. The emission factors for the Lurgi Conventional process technologies should be applied only if the specific process technology is known. Otherwise the emission factor for conventional steam reforming without primary reformer, or the emission factor for conventional steam reforming with primary reformer, should be applied.

The conventional steam reforming process for methanol production can be integrated with an ammonia production process. The emission factor for integrated methanol and ammonia production should be used only if the specific process technology is known.

Table 3.12

Methanol production CO2 emission factors

tonne CO2/tonne methanol produced

Process Configuration Feedstock

Nat. gas

Nat. gas + CO2

Oil

Coal

Lignite

Conventional Steam Reforming, without primary reformer (a) (Default Process and Natural Gas Default Feedstock)

0.67

Conventional Steam Reforming, with primary reformer (b)

0.497

Conventional Steam Reforming, Lurgi Conventional process (c1)

0.385

0.267

Conventional Steam Reforming, Lurgi Low Pressure Process (c2)

0.267

Combined Steam Reforming, Lurgi Combined Process (c3)

0.396

Conventional Steam Reforming, Lurgi Mega Methanol Process (c4)

0.310

Partial oxidation process (d)

1.376

5.285

5.020

Conventional Steam Reforming with integrated ammonia production

1.02

Nat. gas + CO2 feedstock process based on 0.2-0.3 tonne CO2 feedstock per tonne methanol

Emission factors in this table are calculated from the feedstock consumption values in Table 3.13 based on the following feedstock carbon contents and heating values:

Natural Gas: 56 kg CO2/GJ 48.0 GJ/tonne

Oil: 74 kg CO2/GJ 42.7 GJ/tonne

Coal: 93 kg CO2/GJ 27.3 GJ/tonne

Lignite: 111 kg CO2/GJ

Uncertainty values for this table are included in Table 3.27

Sources: (a) Struker, A, and Blok, K, 1995; Methanex, 2003: (b) Hinderink, 1996: (c1 - c4) Lurgi, 2004a; Lurgi, 2004b; Lurgi, 2004c: (d) FgH-ISI, 1999

Table 3.13

Methanol production feedstock consumption factors

GJ feedstock input /tonne methanol produced

Process Configuration Feedstock

Nat. gas

Nat. gas + CO2

Oil

Coal

Lignite

Conventional Steam Reforming, without primary reforme (a) (Default Process and Natural Gas Default Feedstock)

36.5

Conventional Steam Reforming, with primary reformer (b)

33.4

29.3

Conventional Steam Reforming, Lurgi Conventional process (c1)

31.4

Conventional Steam Reforming, Lurgi Low Pressure Process (c2)

29.3

Combined Steam Reforming, Lurgi Combined Process (c3)

31.6

Conventional Steam Reforming, Lurgi Mega Methanol Process (c4)

3G.1

Partial oxidation process (d)

37.15

71.6

57.6

Nat. gas + CO2 feedstock process based on 0.2-0.3 tonne CO2 feedstock per tonne methanol

Sources: (a) Struker, A, and Blok, K, 1995; Methanex, 2003: (b) Hinderink, 1996: (c1 - c4) Lurgi, 2004a; Lurgi, 2004b; Lurgi, 2004c : (d) FgH-ISI, 1999

Uncertainty values for this table are included in Table 3.27

Methane emissions

Methanex reported CH4 emissions from two Canadian methanol production plants in their 1996 Climate Change Action Plan (Methanex, 1996). Methanex reported that CH4 emissions from methanol production may arise from reformers, package boilers, methanol distillation units, and crude methanol storage tanks. CH4 emissions from the plants accounted for approximately 0.5 percent to 1.0 percent of the total greenhouse gas emissions from the plants, but were reported to vary depending upon the level of maintenance and operational control of the plant equipment. The average emission factor reported for two reporting years is 2.3 kg CH4 emissions per tonne of methanol produced. CH4 emissions from a second Methanex methanol production plant were reported to be 0.15 kg CH4 per tonne of methanol produced. The higher of the two reported values, 2.3 kg CH4 per tonne of methanol produced, should be applied as the default CH4 emission factor for methanol production. CH4 emissions as low as 0.1 kg/tonne have been estimated for the methanol plant Tjeldbergodden, Norway (SFT, 2003a).

Ethylene

Carbon dioxide emissions

Emissions of CO2 from steam cracking for ethylene production may be estimated using the feedstock-specific emission factors in Table 3.14 and activity data for the amount of ethylene produced from the steam cracking processes. Separate emission factors are provided in Table 3.14 for the CO2 emissions from feedstock consumption and from supplemental energy consumption in the steam cracking process. However, the CO2 emissions from both feedstock consumption and supplemental energy consumption are to be reported as Industrial Process emissions under the reporting convention discussed above. The default emission factors are derived from plant-specific data for steam crackers operating in Western Europe. The emission factors may be adjusted by applying the default geographic adjustment factors in Table 3.15 to account for differences in the energy efficiency of steam cracking units among various countries and regions. Note that as indicated in Table 3.11, the default feedstock for steam crackers operating in North and South America and Australia is ethane, and the default feedstock for steam crackers operating on other continents is naphtha.

These default emission factors do not include CO2 emissions from flaring. Emissions from flaring amount to about 7 percent of total emissions in a well-maintained plant in Norway. Steam cracking processes that utilise naphtha, propane, and butane feedstocks are assumed to be energy neutral, requiring no use of supplemental fuel, therefore there are assumed to be no CO2 emissions associated with supplemental fuel consumption for these feedstocks.

Table 3.14

Steam cracking ethylene production Tier 1 CO2 emission factors

tonnes CO2/tonne ethylene produced

Feedstock

Naphtha

Gas Oil

Ethane

Propane

Butane

Other

Ethylene (Total Process and Energy Feedstock Use)

1.73

2.29

0.95

1.04

1.07

1.73

- Process Feedstock Use

1.73

2.17

0.76

1.04

1.07

1.73

- Supplemental Fuel (Energy Feedstock) Use

0

0.12

0.19

0

0

0

Source: Neelis, M., Patel, M., and de Feber, M., 2003, Table 2.3, Page 26.

Default feedstocks for ethylene production are identified in Table 3.11. The emission factors do not include supplemental fuel use in flares. Other feedstocks are assumed to have the same product yields as naphtha feedstock. Uncertainty values for this table are included in Table 3.27.

The emission factors in Table 3.14 may be used in the event that activity data are available only for the amount of ethylene produced by the steam cracking process. Steam cracking is a multi-product process that leads to ethylene, propylene, butadiene, aromatics, and several other high-value chemicals. There is an inherent assumption of a specific product mix in the default emission factors in Table 3.14. The default product mix for each emission factor in Table 3.14 is identified in the ethylene steam cracking feedstock-product matrix in Section 3.9.2.3. The feedstock/product matrix identifies the default values for production of ethylene, propylene, and other hydrocarbon products from the steam cracking process in units of kilograms of each product produced per tonne of feedstock. In order to develop the emission factors for steam cracking shown in Table 3.14 the total CO2 process emissions of a steam cracker have been divided by the output of ethylene only. In other words ethylene has been chosen as the reference for estimating the total CO2 emissions from the steam cracking process as a whole. Multiplication of the emission factors in Table 3.14 by the ethylene production therefore leads to the total CO2 emissions resulting not only from the production of ethylene but also from the production of propylene, butadiene, aromatics, and all other chemicals produced by the steam cracking process. The default emission factors in Table 3.14 provide the total CO2 emissions from the steam cracking process, not only the CO2 emissions associated with the production of the ethylene from the steam cracking process.

Table 3.15

Default Geographic Adjustment Factors for Tier 1 CO2 emission factors for steam cracking ethylene production

Geographic Region

Adjustment Factor

Notes

Western Europe

100%

Values in Table 3.14 are based on data from Western European steam crackers

Eastern Europe

110%

Not including Russia

Japan and Korea

90%

Asia, Africa, Russia

130%

Including Asia other than Japan and Korea

North America and South America and Australia

110%

Source: Adjustment factors are based on data provided by Mr. Roger Matthews in personal communication to Mr. Martin Patel, May 2002. Uncertainty values for this table are included in Table 3.27.

Methane emissions

Default fugitive CH4 emission factors for steam cracking of ethane and naphtha for ethylene production are estimated from total VOC emissions factors and VOC species profile data from EMEP/CORINAIR Emission Inventory Guidebook (EEA, 2005). Overall volatile organic compound emissions from steam cracking are estimated to be 5 kg/tonne ethylene produced based on a European publication, for which the feedstock is assumed to be naphtha, and estimated to be 10 kg VOC/tonne ethylene produced based on a U.S. publication, for which the feedstock is assumed to be ethane. From the total VOC emission factors the overall CH4 emissions from steam cracking of naphtha are estimated from the VOC species profile to be 3 kg/tonne ethylene produced, primarily from leakage losses, and the overall CH4 emissions from cracking of ethane are estimated from the species profile to be twice those from cracking of naphtha (6 kg/tonne ethylene produced); however these factors are subject to uncertainty as the overall VOC emission factors of 5 kg VOC/tonne ethylene for naphtha feedstock and 10 kg VOC/tonne ethylene for ethane feedstock are each based on a single publication. Emissions of CH4

from steam cracking of feedstocks other than ethane and naphtha have been assumed to be the same as that estimated from the EMEP/CORINAIR data for steam cracking of naphtha.

Published data show a large variability in reported CH4 emission factors for ethylene production. The European Association of Plastics Manufacturers (APME) Eco-Profiles of the European Plastics Industry reports a CH4 emission factor for ethylene production of 2.9 kg CH4/tonne ethylene produced, as referenced in the APME Eco-Profiles for Olefins Production (Boustead, 2003a). The CH4 emission factor for ethylene steam cracker process operations is based on life-cycle analysis data for 15 European steam crackers. Emissions as low as 0.14 kg CH4/tonne ethylene are estimated on the basis of direct measurement at a Norwegian ethylene plant (SFT 2003b) and as low as 0.03 kg CH4/tonne ethylene based on company data reported in the Australian Methodology for the Estimation of Greenhouse Gas Emissions and Sinks, 2003 (AGO, 2005). Other European and Australian steam cracker operators reported plant-specific CH4 emissions on the order of 10 percent of the values reported in Table 3.16 (DSM, 2002; Qenos, 2003; Qenos, 2005). Therefore, the emission factors in Table 3.16 should not be used to estimate CH4 emissions from steam cracker ethylene plants for which plant-specific data are available. In this case the plant-specific data and the Tier 3 method should be used. Default CH4 emission factors for various process feedstocks are shown in Table 3.16. Note that the default feedstocks for ethylene production are identified in Table 3.11.

Table 3.16

Default methane emission factors for ethylene production

Feedstock

kg CH4/ tonne ethylene produced

Ethane

6

Naphtha

3

All Other Feedstocks

3

Source: EEA, 2005 (EMEP/CORINAIR Emission Inventory Guidebook) Uncertainty values for this table are included in Table 3.27.

Ethylene dichloride and vinyl chloride monomer

Carbon dioxide emissions

Emission factors are provided in Table 3.17 for the ethylene dichloride and vinyl chloride monomer production processes, including the direct chlorination process, oxychlorination process, and balanced process. The CO2 emission factors are derived by averaging plant-specific CO2 emissions data for European plants reported in the Integrated Pollution Prevention and Control (IPPC) Reference Document on Best Available Techniques in the Large Volume Organic Chemical Industry (European IPPC Bureau, February 2003; referred to in this section as the IPPC LVOC BAT Document). Note that as indicated in Table 3.11, the default process is the balanced process for EDC production with an integrated VCM production plant. The total CO2 emission factor for each process includes noncombustion CO2 emissions from the ethylene dichloride process vent and combustion CO2 emissions from ethylene dichloride plant combustion sources. Plant combustion source emission factors include combustion of both process waste gas and auxiliary fuel in the process waste gas thermal incinerator. The combustion-related emission factor does not include emissions from flares. Combustion-related emission factors in Table 3.17 are based on data from oxychlorination process plants but the emission factors are assumed also to apply to direct chlorination and balanced process plants. Feedstock consumption factors for ethylene dichloride and vinyl chloride monomer production processes are provided in Table 3.18. The PlasticsEurope EcoProfiles (Boustead, 2005) for EDC production indicates ethylene utilisation of 0.306 tonnes ethylene per tonne EDC produced, based on eight European plants.

It should be noted that the CO2 emission factors in Table 3.17 in units of tonnes CO2 per tonne EDC produced and in units of tonnes CO2 per tonne VCM produced are not additive. The two CO2 emission factors both apply to the integrated EDC/V CM production process, however the tonnes CO2 per tonne EDC factor is based on EDC production activity data while the tonnes CO2 per tonne VCM factor is based on VCM production activity data. The CO2 emission factor that will be applied will depend upon whether activity data for EDC production or activity data for VCM production are available. Similarly, the feedstock consumption factors in Table 3.18 in units of tonnes ethylene consumed per tonne EDC produced and in units of tonnes ethylene consumed per tonne VCM produced are not additive. The feedstock consumption factor that will be applied will depend upon whether activity data are available for EDC production or for VCM production.

Table 3.17

Ethylene dichloride/vinyl chloride production process Tier 1 CO2 emission factors

Process Configuration

tonne CO2/tonne EDC produced

tonne CO2/tonne VCM produced

Direct Chlorination Process

Noncombustion Process Vent

negligible emissions

negligible emissions

Combustion Emissions

0.191

0.286

Total CO2 Emission Factor

0.191

0286

Oxychlorination Process

Noncombustion Process Vent

0.0113

0.0166

Combustion Emissions

0.191

0.286

Total CO2 Emission Factor

0.202

0.302

Balanced Process [default process]

Noncombustion Process Vent

0.0057

0.0083

Combustion Emissions

0.191

0.286

Total CO2 Emission Factor

0.196

0.294

Values for CO2 emissions from EDC and VCM production for several European production plants were provided in Tables 12.6 and 12.7 of the IPPC LVOC BAT Document (European IPPC Bureau, 2003). These values were averaged to calculate CO2 emission factors for EDC and VCM production. One EDC plant that is equipped with a CO2 control device and that reported zero CO2 emissions from the process is not included in the average emission factor.

Source: European IPPC Bureau, 2003 (IPPC LVOC BAT Document, Tables 12.6 and 12.7 data). Uncertainty values for this table are included in Table 3.27.

Table 3.18

Ethylene dichloride/vinyl chloride monomer process Tier 1 feedstock consumption factors

Process Configuration

tonne ethylene/tonne EDC produced

tonne ethylene/tonne VCM produced

Direct Chlorination Process

0.290

--

Oxychlorination Process

0.302

--

Balanced Process

0.296

0.47

Source: European IPPC Bureau, 2003 (IPPC LVOC BAT Document, Section 12.3.1, Page 299-300, Section 12.1 Table 12.3, Page 293). Uncertainty values for this table are included in Table 3.27.

Methane emissions

The EMEP/CORINAIR 'species profile' for the ethylene dichlo ride/vinyl chloride monomer balanced process indicates that there are no CH4 emissions from the process other than CH4 emissions from combustion sources. The EMEP/CORINAIR species profile reports that VOC emissions from leakage losses and storage and handling do not contain CH4. The EMEP/CORINAIR also reports that 2 percent of the total VOC emissions from the balanced process are from combustion sources and that CH4 constitutes 1.2 percent of overall VOC emissions. Therefore it may be assumed that non-combustion CH4 emissions from ethylene dichloride/vinyl chloride monomer production are negligible.

CH4 emissions from combustion of natural gas supplemental fuel in the ethylene dichloride/vinyl chloride monomer production process may be estimated from activity data for natural gas supplemental fuel consumption and CH4 emission factor for natural gas combustion. Natural gas consumption for integrated ethylene dichloride/vinyl chloride monomer production is estimated to be 110.1 Nm3 natural gas/tonne VCM produced for an integrated ethylene dichloride/vinyl chloride monomer production plant in the Netherlands and 126.4 Nm3 natural gas/tonne VCM produced for an integrated ethylene dichloride/vinyl chloride monomer production plant in Germany. The average of these two values is 118.3 Nm3 natural gas/tonne VCM. The CH4 emission factor for the integrated EDC/VCM production process is based on a CH4 emission factor of 5 g CH4/GJ natural gas combusted and the average natural gas consumption of the two European plants. The default CH4 emission factor for the integrated ethylene dichloride/vinyl chloride monomer production process is provided in Table 3.19. The default emission factor is not applicable to stand-alone EDC production plants. If natural gas consumption activity data are available, the CH4 emission factor of 5 g CH4/GJ may be applied directly to the activity data, rather than using the default emission factor.

Table 3.19

Ethylene dichloride/vinyl chloride process Tier 1 default CH4 emission factor

Process Configuration

kg CHHt/tonne VCM product produced

Integrated EDC/VCM Production Plant

G.G226

Sources: European IPPC Bureau, 2003 (IPPC LVOC BAT Document, Section 12.3.1, Table 12.4, Page 300); EEA, 2005 (EMEP/CORINAIR Emission Inventory Guidebook, Processes in Organic Chemical Industries (Bulk Production) 1, 2-Dichloroethane and Vinyl Chloride (Balanced Process), Activity 040505, February 15, 1996, Section 3.4, Page B455-3, and Table 9.2, B455-5).

Ethylene oxide

Carbon dioxide emissions

Emissions of CO2 from ethylene oxide production may be estimated using emission factors based on activity data for ethylene oxide production, and activity data for process configuration and catalyst selectivity. Separate CO2 emission factors are provided in Table 3.20 for the CO2 emissions from the air process and for the CO2 emissions from the oxygen process for a range of catalyst selectivity. The default emission factors for the air process and for the oxygen process are estimated from process-specific catalyst selectivity data provided in the IPPC LVOC BAT document. Specific data concerning the type of process and the selectivity of the process catalyst are needed in order to select emission factors from Table 3.20. The emission factors are derived from the catalyst selectivity using stoichiometric principles and are based on the assumption that emissions of CH4 and NMVOC from the process are negligible and that all of the carbon contained in the ethylene feedstock is converted either into ethylene oxide product or to CO2 emissions. The emission factors in Table 3.20 do not include emissions from flares.

As shown in Table 3.20, the default emission factor for the air process is based on a default process catalyst selectivity of 70 percent and the default emission factor for the oxygen process is based on a default catalyst selectivity of 75 percent. If activity data are not available for the process configuration or the catalyst selectivity, the default process configuration is the air process and the default catalyst selectivity is 70 percent. If activity data are available that identify the process used as the oxygen process, but activity data are not for the catalyst selectivity for the oxygen process, the emission factor for the default catalyst selectivity of 75 percent for the oxygen process in Table 3.20 should be used.

Table 3.20

Ethylene oxide production feedstock consumption and CO2 emission factors

Process Configuration

Catalyst Selectivity

Feedstock Consumption (tonne ethylene/ tonne ethylene oxide)

Emission Factor (tonne CO2/ tonne ethylene oxide)

Air Process [default process]

Default (70)

0.90

0.863

75

0.85

0.663

80

0.80

0.5

Oxygen Process

Default (75)

0.85

0.663

80

0.80

0.5

85

0.75

0.35

Source: European IPPC Bureau, 2003 (IPPC LVOC BAT Document, Section 9.2.1, Page 224, Section 9.3.1.1, Page 231, Figure 9.6)

Methane emissions

The IPPC LVOC BAT document for ethylene oxide production reported CH4 emissions factors (in units of kilograms methane per tonne ethylene oxide produced) for the ethylene oxide process vent, ethylene oxide purification process exhaust gas steam, and fugitive emissions sources. CH4 emission factors were reported in the IPPC LVOC BAT document for European ethylene oxide plant carbon dioxide removal vents before and after treatment. CH4 emissions were also reported for two ethylene oxide plants in the Netherlands. CH4 emission factors for ethylene oxide production were developed by averaging these data. Emissions of CH4 may be estimated by applying the emissions factors included in Table 3.21 to activity data for ethylene oxide production. The default CH4 emission factor for ethylene oxide production assumes no thermal treatment process.

Table 3.21

Ethylene oxide production Tier 1 CH4 emission factors

Process Configuration

kg CH4/tonne ethylene oxide produced

No Thermal Treatment [default factor]

1.79

Thermal Treatment

0.79

Source: European IPPC Bureau, 2003 (IPPC LVOC BAT Document, Table 9.6, Page 233; Table 9.8, Page 236; Table 9.9, Page 236).

Acrylonitrile

Carbon dioxide emissions

Process vent CO2 emissions from the acrylonitrile production process by the direct ammoxidation of propylene may be calculated from acrylonitrile production activity data using the emission factors provided in Table 3.22:

Table 3.22

Acrylonitrile production CO2 emission factors

Process Configuration

Direct Ammoxidation of Propylene

tonnes CO2/tonne acrylonitrile produced

Secondary Products Burned for Energy Recovery/Flared (default)

1.00

Acetonitrile Burned for Energy Recovery/Flared

0.83

Acetonitrile and Hydrogen Cyanide Recovered as Product

0.79

Source: European IPPC Bureau, 2003 (IPPC LVOC BAT Document, Section 11.3.1.1, Table 11.2, Page 274 and Section 11.3.1.2, Page 275)

The emission factors in Table 3.22 are based on an average (default) propylene feedstock consumption factor of 1.09 tonnes propylene feedstock per tonne acrylonitrile produced, corresponding to a primary product yield factor of approximately 70 percent. The default CO2 emission factor is based on conversion of propylene feedstock to secondary product acetonitrile at 18.5 kilograms per tonne acrylonitrile produced, and conversion of propylene to secondary product hydrogen cyanide at 105 kilograms per tonne acrylonitrile produced, and is based on process-specific acrylonitrile yield data and process-specific feedstock consumption data reported in the IPPC LVOC BAT document (European IPPC Bureau, 2003). Note however that the acrylonitrile production process may be configured and operated to produce a greater or lesser amount of secondary products. The default CO2 emission factor is based on the assumption that the secondary products (acetonitrile and hydrogen cyanide) of the acrylonitrile production process and hydrocarbon by products in the main absorber vent gas are either burned for energy recovery or flared to CO2 and are not recovered as products or emitted to the atmosphere without combustion treatment. The CO2 emission factors do not include CO2 emissions from any combustion of auxiliary fuel (e.g., natural gas) for the process waste gas energy recovery or flare systems.

If activity data are not available concerning whether secondary products are recovered for sale, the default assumption is that the secondary products are either burned for energy recovery or flared to CO2 and the default primary product process yield factor is 70 percent.

For the process configuration where secondary products (acetonitrile and hydrogen cyanide) are recovered for sale and are not either flared to CO2 or burned for energy recovery, the overall process yield factor of primary and secondary products is 85 percent.

If activity data for propylene feedstock consumption are not available, the propylene feedstock consumption may be estimated from the acrylonitrile production activity data by applying a default feedstock consumption factor of 1.09 tonnes propylene feedstock consumed per tonne acrylonitrile produced.

Methane emissions

The Life-Cycle Analysis Data Summary for Acrylonitrile reports a CH4 emission factor for acrylonitrile production of 0.18 kg CHVtonne acrylonitrile produced, as referenced in the European Association of Plastics Manufacturers (APME) Life-Cycle Analysis Report (Boustead, 1999). The CH4 emission factor for acrylonitrile process operations is based on life-cycle analysis data for European acrylonitrile plants in Germany, Italy, and the United Kingdom collected between 1990 and 1996. CH4 emissions from acrylonitrile production may be estimated by applying this default emission factor to the acrylonitrile production data.

Carbon black

Carbon dioxide emissions

Emissions of CO2 from carbon black production may be estimated by applying the process and feedstock-specific emission factors to the carbon black production activity data. Separate emission factors are provided in Table 3.23 for the furnace black process, thermal black process, and acetylene black process and their associated feedstocks, and separate emission factors are provided for primary feedstock and secondary feedstock. The emission factors are based on the assumption that process emissions are subjected to a thermal treatment process.

A range of values for primary and secondary carbon black feedstock is included in Table 4.11 of the draft Integrated Pollution Prevention and Control (IPPC) Reference Document for Best Available Techniques in the Large Volume Inorganic Chemicals (LVIC) Solid and Others Industry (European IPPC Bureau, June 2005; referred to in this chapter as the Draft IPPC LVIC BAT Document.) The CO2 emission factors in Table 3.23 are based on the average of the range of values. Primary and secondary feedstock consumption is converted to carbon consumption using average values for carbon black feedstock carbon content. The CO2 emission factors are calculated from the carbon input to the process (primary and secondary feedstocks) and carbon output (carbon black) from the process, using an average value for carbon black carbon content.

Table 3.23

Carbon black production Tier 1 CO2 emission factors

Process Configuration

tonnes CO2/tonne carbon black produced

Primary Feedstock

Secondary Feedstock

Total Feedstock

Furnace Black Process (default process)

1.96

G.66

2.62

Thermal Black Process

4.59

G.66

5.25

Acetylene Black Process

G.12

G.66

G.78

Source: European IPPC Bureau, 2005 (Draft IPPC LVIC BAT Document, Table 4.11 data)

Methane emissions

CH4 emissions for the carbon black production process are provided in Table 3.24. The draft IPPC LVIC BAT document for carbon black reported the CH4 content of uncombusted tail gas from the carbon black production process and the estimated rate of generation of tail gas from the carbon black production process. Based on 10,000 Nm3 tail gas per tonne carbon black produced and an average reported CH4 concentration of 0.425 percent by volume, the uncontrolled CH4 emission factors is 28.7 kg CH4/tonne carbon black produced. Combustion flare efficiency for carbon black process flare systems was reported in the Draft IPPC LVIC BAT Document as 99.8 percent for carbon monoxide, and the same efficiency is assumed to apply to CH4. The CH4 emission factor for carbon black production after application of combustion control is 0.06 kg CH4/tonne carbon black produced. An overall CH4 emission factor of 0.11 kg CH4/tonne carbon black, based on company data, was reported in the Australian Methodology for the Estimation of Greenhouse Gas Emissions and Sinks, 2003 (AGO, 2005.) Three carbon black production plants in Germany reported a common CH4 emission factor of 0.03 kg CH4/tonne carbon black produced, based on measurement data after waste gas combustion using BAT (Thermische Nachverbrennung als Stand der Technik.)

Table 3.24

Carbon black production Tier 1 CH4 emission factors

Process Configuration

kilogram CH4/tonne carbon black produced

(Carbon Black Process Tail Gas )

No Thermal Treatment

28.7

Thermal Treatment (default process)

0.06

Source: European IPPC Bureau, 2005 (Draft IPPC LVIC BAT Document, Table 4.8, Page 209; Table 4.10, Page 213, Section 4.3.2.3, Page 210).

TIER 2

The Tier 2 methodology is based on mass balance calculations and therefore there are no emission factors associated with the methodology.

TIER 3

For the Tier 3 method plant specific emissions may be estimated using Equations 3.20 through 3.22 for CO2, and using either Equation 3.26 or Equations 3.27 through 3.29 for CH4. The emission factors may be related to annual production for estimation of emissions between measurements when these are not continuous.

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