
                                       
REVISED TECHNICAL SUPPORT DOCUMENT FOR CALCIUM CARBIDE: SUPPLEMENTAL PROPOSED RULE FOR THE GREENHOUSE GAS REPORTING PROGRAM
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                                    Office of Air and Radiation
                                           U.S. Environmental Protection Agency
                                                                               
                                                                               
                                                                  April 1, 2023
                                   CONTENTS
                                       
1.  Industry Description	1
2.  Total Emissions	2
3.  Review of Existing Programs and Methodologies	3
3.1  Review of Existing Programs	3
3.2  Calculation Methodologies for Calcium Carbide Production Processes	4
4. Options for Reporting Threshold	6
5.  Options for Monitoring Methods	7
5.1  CEMS Method	7
5.2  Mass Balance and Combustion Methods	7
6. QA/QC Requirements	8
6.1 Stationary Emissions	8
6.2 Process Emissions	8
6.3 Data Management	9
7. Options for Estimating Missing Data	9
7.1 Procedures for Option 1: Direct Measurement using CEMS	10
7.2 Procedures for Option 2: Mass Balance and Combustion Method	10
8.  References	11



























1.  Industry Description  

Calcium carbide is an industrial chemical manufactured from lime (CaO) and carbon, usually petroleum coke, by heating the mixture to 2,000 to 2,100 °C (3632 to 3812 °F) in an electric arc furnace (EPA 1995). Calcium carbide has both metallurgical and chemical applications. In modern steel making and ductile iron foundries, it is used to lower the sulfur content. When reacted with water, calcium carbide produces acetylene and calcium hydroxide. The largest use of acetylene is as a cylinder gas used in metal cutting and welding. Acetylene derivatives are also used in a number of consumer products. Calcium hydroxide has several industrial applications including scrubbing sulfur emissions from industrial processes and power plants, pH modification of soil, and neutralization of acidic waste streams from industrial processes. (Carbide Industries, 2016)

During the production of calcium carbide, the use of carbon-containing raw materials (petroleum coke) results in emissions of CO2 and CO. The presence of hydrogen-containing volatile compounds and sulfur (S) in the petroleum coke may cause formation and emission to the atmosphere of CH4 and SO2. (IPCC 2006)

Calcium carbide (CaC2) is made by heating calcium carbonate (limestone) and subsequently reducing CaO with carbon (e.g., petroleum coke). Both steps lead to emissions of CO2. Around 67 percent of the carbon from petroleum coke will be contained in the product. (IPCC 2006).

The basic reactions are:

                              CaCO3 --> CaO + CO2
                                       
                   CaO + 3C --> CaC2 + CO (+ (1/2) O2 --> CO2)

CaO (lime) produced by the calcination of calcium carbonate (limestone) might be produced at the calcium carbide production facility or at a plant other than the carbide plant. In either case, the emissions from the CaO step should be reported as emissions from lime production.

The largest application of calcium carbide is producing acetylene (C2H2) by reacting CaC2 with water. The production of acetylene from CaC2 results in the emissions of CO2. (IPCC 2006) Acetylene is not produced at the one known plant that produces CaC2 (Carbide Industries, 2016); therefore, CO2 emissions from the production of acetylene from CaC2 are not directly considered in this technical support document.

There is currently one producer of calcium carbide in the U.S., Carbide Industries, LLC, located in Louisville, KY. According to their website (https://www.carbidellc.com), calcium carbide is their only product. A calcium carbide production plant located in Pryor, OK, that was owned by Carbide Industries closed in March 2014. Although an important use of calcium carbide, there is no information that indicates the company produces and sells acetylene although they operate an acetylene flare and report the CO2 emissions from the flaring operation. A 2013 report on an electric arc furnace explosion at the facility stated that the facility maintained an acetylene storage tank to collect fugitive acetylene gas from the plant but they did not produce acetylene to sell. (USCSHIB 2013). According to their website, Carbide Industries has an annual capacity of over 100,000 tons per year. According to their title V permit, they have a prevention of significant deterioration (PSD) production limit of 126,887 tons of carbide. The permit notes that the maximum carbide production in the 10-year lookback period was 111,376 tons. (Louisville Metro Air Pollution Control District 2019).

2.  Total Emissions

The only known U.S. producer of calcium carbide, Carbide Industries LLC, currently reports their process greenhouse gas (GHG) emissions under the GHG Reporting Program (GHGRP; 40 CFR part 98), subpart K  -  Ferroalloy Production. Their reporting under subpart K is voluntary as the subpart does not cover the production of calcium carbide. They also report their combustion emissions under GHGRP subpart C  -  Stationary Combustion Sources, which includes CO2 emissions from an acetylene flare. Table 1 below presents the emissions reported to the GHGRP by Carbide Industries LLC (Facility ID 1005537) from 2010 to 2020.

Table 1.  GHG Emissions Reported by Carbide Industries LLC to the GHGRP from 2010 to 2021
                                REPORTING YEAR
                            Process Emissions (mt)
                           Combustion Emissions (mt)

                                      CO2
                                      CH4
                                   Total CO2
                              Acetylene Flare CO2
                                      CH4
                                      N2O
                                     2010
                                    51,872
                                       0
                                      0.4
                                      NR
                                       0
                                       0
                                     2011
                                    14,717
                                      47
                                      0.1
                                      NR
                                       0
                                     0.198
                                     2012
                                    13,470
                                      104
                                     309.2
                                      NR
                                     0.01
                                     0.003
                                     2013
                                   20,893.2
                                     0.97
                                    7,011.2
                                      NR
                                       0
                                     0.002
                                     2014
                                    6,928.6
                                     50.86
                                    1,195.1
                                     183.9
                                     0.03
                                     0.004
                                     2015
                                   45,838.5
                                     53.24
                                    7,652.2
                                      149
                                     0.02
                                     0.004
                                     2016
                                   44,508.1
                                     47.54
                                    1,056.3
                                     139.2
                                     0.03
                                     0.003
                                     2017
                                   51,799.5
                                     48.74
                                    1,078.9
                                     173.4
                                     0.03
                                     0.003
                                     2018
                                   54,388.5
                                     52.5
                                    1,459.7
                                     143.7
                                     0.03
                                     0.003
                                     2019
                                   49,158.7
                                     43.07
                                     1,062
                                     62.3
                                     0.02
                                     0.003
                                     2020
                                   40,048.3
                                     42.71
                                    5,548.3
                                     83.4
                                     0.02
                                     0.005
Source: Facility-Level Information on Greenhouse Gases Tool (FLIGHT) (https://ghgdata.epa.gov/ghgp/service/facilityDetail/2021?id=1005537&ds=E&et=&popup=true) 

NR = not reported


3.  Review of Existing Programs and Methodologies

3.1 Review of Existing Programs
In developing GHG monitoring and reporting options for calcium carbide manufacturing processes, a number of existing programs and guideline methodologies were reviewed. Specifically, the following programs were examined:

 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories.

 European Union (EU). Commission Implementing Regulation (EU) 2018/2066 of 19 December 2018 on the Monitoring and Reporting of Greenhouse Gas Emissions Pursuant to Directive 2003/87/EC of the European Parliament and of the Council and Amending Commission Regulation (EU) No. 601/2012. January 1, 2021. Available at:  
      https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02018R2066-20210101&from=EN. 
       
 CARB (California Air Resource Board). Unofficial Electronic Version of the Regulation for the Mandatory Reporting of Greenhouse Gas Emissions. April 2019. https://ww2.arb.ca.gov/mrr-regulation.

 Environment and Climate Change Canada (ECCC). Canada's Greenhouse Gas Quantification Requirements. Version 4.0. December 2020. http://publications.gc.ca/collections/collection_2021/eccc/En81-28-2020-eng.pdf.
      
 United States Environmental Protection Agency (USEPA). Greenhouse Gas Reporting Program (GHGRP).
      
 Australian National Greenhouse and Energy Reporting (Measurement) Determination 2008, Division 4.3.4-Carbide production, July 1, 2021.
      https://www.legislation.gov.au/Series/F2008L02309 

Each of these programs were reviewed to determine their applicability to the calcium carbide production source category and whether they contained information on the types of emissions to be reported, the facility reporting thresholds, the calculation methodologies, and the monitoring methodologies recommended. The remainder of this section summarizes the key calculation methodologies. The reporting and monitoring options presented in Section 4 and Section 5 are commensurate with the methodologies used in these existing programs and guidelines.

It was determined that methods for calculating GHG emissions from the 2006 IPCC Guidelines were appropriate for the source category. The IPCC methods are classified according to the extent of plant-level data that are available. The Tier 1 method is based on default emission factors. Tier 2 is based on plant-level data on production and use of CaC2 in acetylene production for welding applications. The Tier 3 method is based on plant-level data on petroleum coke input (including the carbon content factor (CCF) and carbon oxidation factor (COF) if available), and plant-level emission factors where relevant.  The following options are provided, largely based on the IPCC methods.

3.2  Calculation Methodologies for Calcium Carbide Production Processes
The following calculation methodologies were identified. The calculation methods are presented in terms of their relative accuracy from most to least accurate.

Method 1  -  CO2 CEMS.  Measure CO2 concentration and total exhaust gas flow rate using a continuous emission monitoring system (CEMS) and calculate CO2 mass emission rates from these measured values using Equation C-6 and, if necessary, Equation C-7 of 40 CFR 98.33(a)(4).

Method 2  -  Carbon balance method. This IPCC Tier 3 method uses the quantity of carbon, in the form of petroleum coke, consumed in the production process minus the amount of carbon in the CaC2 product. Note that the IPCC carbon balance method does not include potential CO2 emissions from electrode consumption, but it is included in Equation 1 below for completeness.

The basic equation is:

ECO2 = 44/12 x 2000/2205 x [(Mcoke x CCFcoke) + (Melect x CCFelect)  -  (MCaC2 x CCFCaC2)]	(Eq. 1)

Where:

   ECO2 = emissions of CO2, metric tons
   
   44/12 = ratio of molecular weights, CO2 to carbon.
   
   2000/2205 = conversion factor to convert short tons to metric tons.
   
   Mcoke = mass of petroleum coke consumed, in short tons. 
   
   CCFcoke = carbon content of petroleum coke used at the facility, weight fraction.
   
   Melect = mass of electrode consumed, in short tons
   
   CCFelect = carbon content of electrode, weight fraction.
   
   MCaC2 = mass of calcium carbide product produced at the facility, in short tons.
   
   CCFCaC2 = carbon content of calcium carbide product produced at the facility, weight fraction. [Note, this could be a measured quantity or calculated based on product purity. Using product purity, CCFCaC2 = Purity (mass fraction) x 24/64.1, where 24 is mass of carbon in one mole of CaC2 and 64.1 is the molecular weight of CaC2.]

Method 3  -  Carbon consumption method. In this IPCC Tier 2 approach, the carbon balance method expressed in Equation 1 is used, but the emission factor is calculated based on the carbon consumption. This method uses a stoichiometric conversion assuming two-thirds of the carbon consumed is in the CaC2 product and one-third is emitted as CO2. In this case, the emission factor is:  

           ECO2 = 0.33 :: CCF :: COF :: Mcoke :: 44/12		(Eq. 2)

Where:

   0.33 = Adjustment factor for the amount of carbon in calcium carbide product (assuming 67 percent of carbon input is in the carbide product).
   
   CCF = Carbon content factor for petroleum coke consumed (measured by plant or use default carbon content for petroleum coke).
   
   COF = Carbon oxidation factor (assumed to be 1).
   
   44/12 = Ratio of molecular weights, CO2 to carbon.

This is essentially the method used for silicon carbide production (40 CFR part 98, subpart BB). 

Method 4  -  Default emission factors. Using this IPCC Tier 1 method, emissions from carbide production can be estimated from activity data on petroleum coke consumption or carbide production and the default emission factors. The basic equation for estimating emissions is:

                           ECO2 = AD :: EF		(Eq. 3)

Where:

   ECO2 = emissions of CO2, metric tons.
   
   AD = activity data on petroleum coke consumption or carbide production, metric tons raw material used or metric tons carbide produced.
   
   EF = CO2 emission factor. Use EF = 1.09 metric tons CO2/metric tons CaC2 produced when carbide production is used as activity data. Use EF = 1.70 metric tons CO2/metric tons material when petroleum coke consumption is used as activity data. (IPCC 2006)

These default emission factors account for additional petroleum coke consumption and resulting CO2 emissions than direct stoichiometric conversion suggests.

Equation 3 above can also be used to estimate methane emissions where EF is the appropriate emission factor for methane. Unlike for silicon carbide, the IPCC chapter does not provide an EF for methane emissions from CaC2 production.

Method 5  -  Non-CEMS subpart K method. The one currently operating calcium carbide production facility is reporting GHG emissions under subpart K  -  Ferroalloy Production. This facility does not measure its CO2 emissions using CEMS and therefore calculates its emissions using the IPCC Tier 3 equations in GHGRP subpart K. The equations in subpart K have the following general format:

                ECO2 = 44/12 x 2000/2205 x ∑(M x C)		(Eq. 4)

Where:

   ECO2 = annual process CO2 emissions from an EAF.
   
   44/12 = Ratio of molecular weights, CO2 to carbon.
   
   2000/2205 = Conversion factor to convert tons to metric tons.
   
   M = mass of ore, electrode, reducing agent, etc, in short tons.
   
   C = Carbon content of M
   
If Carbide Industries LLC accounts only for the consumption of carbon from the electrode of the electric arc furnace, this equation is expected to underestimate the CO2 emissions from the process. If Carbide Industries LLC includes the mass of coke fed to the process (as mass of ore), then this equation is expected to overstate the CO2 emissions since some of the carbon in the petroleum coke is contained in the CaC2 product. 

4. Options for Reporting Threshold

Different options for reporting thresholds are presented, including an emissions threshold, a production capacity threshold, and no threshold. 

Four emissions threshold levels were considered for the calcium carbide manufacturing sector 
based on actual emissions. These thresholds, 100,000, 25,000, 10,000, and 1,000 metric tons carbon dioxide equivalent (mtCO2e) per year, were analyzed. Table 2 provides the threshold analysis for the calcium carbide sector. The threshold analysis estimated total 2020 emissions for the calcium carbide sector at 46,878 metric tons CO2e. This total was the additive sum of estimated process emissions (41,244 mtCO2e) and combustion emissions (5,634 mtCO2e). The single facility with known production would surpass all but the 100,000 metric tons CO2 reporting threshold. Process and combustion emissions are those reported to the GHGRP under subpart K, Ferroalloy Production, and subpart C, General Stationary Fuel Combustion Sources.


Table 2. Emissions Threshold Analysis for Calcium Carbide Production
                         Threshold Level (Metric Tons)
                  Process Emissions (Metric Tons CO2e/yr)[a]
                 Combustion Emissions (Metric Tons CO2e/yr)[a]
                Total National Emissions (Metric Tons CO2e/yr)
                              Number of Entities
                               Emissions Covered
                               Entities Covered





                                 Tons CO2e/yr
                                    Percent
                                    Number
                                    Percent
                                  100,000.00
                                    41,244
                                     5,634
                                    46,878
                                       1
                                       0
                                      0%
                                       0
                                      0%
                                   25,000.00
                                    41,244
                                     5,634
                                    46,878
                                       1
                                    46,878
                                     100%
                                       1
                                     100%
                                   10,000.00
                                    41,244
                                     5,634
                                    46,878
                                       1
                                    46,878
                                     100%
                                       1
                                     100%
                                   1,000.00
                                    41,244
                                     5,634
                                    46,878
                                       1
                                    46,878
                                     100%
                                       1
                                     100%
[a] Assumes CH4 GWP of 28 and N2O GWP of 265.

Production capacity threshold is another option for reporting that has been evaluated for subparts included in the GHGRP. Information from the title V permit for the only operating calcium carbide production facility as well as information on the facility's website, indicates that the facility's calcium carbide production capacity is over 100,000 tons (90,700 metric tons) per year. Process emissions for the facility reported under subpart K for reporting year 2020 were 41,116 mtCO2e/yr. 

Another reporting threshold option to consider is the no emissions threshold. The no emissions threshold includes all calcium carbide manufacturing facilities included in this Technical Support Document regardless of their emissions or capacity. The option of regulating all calcium carbide manufacturing facilities regardless of their emissions profile is similar to the emissions threshold option when only the known facility is considered because at each threshold level the known facility would be regulated. When the possibility of new facilities is considered, the no emissions threshold option becomes more inclusive since it is likely that an emissions threshold option would not include smaller facilities at certain emission thresholds.

5.  Options for Monitoring Methods 

5.1  CEMS Method 
The CEMS method uses direct measurement CO2 concentration and total exhaust gas flow rate, The CEMS monitoring requirements are outlined in 40 CFR 98.33(a)(4). 

5.2  Mass Balance and Combustion Methods 
All of the non-CEMS methods require monitoring of mass quantities of petroleum coke fed to the process, calcium carbide produced, the carbon content of the petroleum coke, or the use of emission factors in the case of Tier 1 calculations. The carbon balance method in Eq. 1 also includes mass quantities of carbon electrodes consumed.

The mass quantities can be determined using commercial weighing equipment meeting selected accuracy requirements or can simply specify the use of company records. Generally, most facilities would follow the National Institute of Standards and Technology (NIST) requirements for weighing and measuring devices (NIST, 2023). Measurements made following NIST requirements are expected to be more accurate than measurements made not following NIST requirements.

Subpart BB  -  Silicon Carbide Production requires determination of carbon content of the petroleum coke. The carbon content of the petroleum coke is commonly determined via ultimate analysis of the coke. Suitable methods include:

 ASTM D3176-89 Standard Practice for Ultimate Analysis of Coal and Coke. 
 ASTM D5373-08 Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Laboratory Samples of Coal.

Subpart K  -  Ferroalloy Production requires determination of carbon content of material inputs and outputs. The carbon content is determined using the information provided by the material supplier or using the following methods:

 ASTM E1941-04, Standard Test Method for Determination of Carbon in Refractory and Reactive Metals and Their Alloys.
 ASTM D5373-08 Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Laboratory Samples of Coal.
 ASTM C25-06, Standard Test Methods for. Chemical Analysis of Limestone, Quicklime, and Hydrated Lime.

It is expected that ultimate analyses composition will be available from purchase records of petroleum coke and from routine monitoring of feed material and product quality analyses. The carbon content is not likely to vary that significantly. The rule could specify a measurement frequency (weekly, monthly, quarterly, or annually). Typically, the more measurements conducted, the more accurate the average value will be. 

6. QA/QC Requirements

Facilities should conduct quality assurance and quality control (QA/QC) of the production and consumption data, supplier information (e.g., carbon contents), and emission estimates reported. Facilities are encouraged to prepare an in-depth quality assurance and quality control plan which would include checks on production data, the carbon content information received from the supplier or from the lab analysis, and calculations performed to estimate GHG emissions. Several examples of QA/QC procedures are listed below.

6.1 Stationary Emissions
For QA/QC options for stationary combustion, refer to Docket item EPA-HQ-OAR-2008-0508-0004.

6.2 Process Emissions
Options and considerations for QA/QC will vary depending on the proposed monitoring method. Each option would require unique QA/QC measures appropriate to the particular methodology employed to ensure proper emission monitoring and reporting.

6.3 Data Management
Data management procedures should be included in the QA/QC Plan. Elements of the data 
management procedures plan are as follows:

 For measurements of carbonate content, assess representativeness of the carbonate content measurement by comparing values received from supplier and/or laboratory analysis with IPCC default values. 
 Check for temporal consistency in production data, carbonate content data, and emission estimate. If outliers exist, they should be explained by changes in the facility's operations or other factors. A monitoring error is probable if differences between annual data cannot be explained by: 
 Changes in activity levels, 
 Changes concerning fuels or input material, 
 Changes concerning the emitting process (e.g. energy efficiency improvements) (European Commission 2007). 

 Determine the "reasonableness" of the emission estimate by comparing it to previous year's estimates and relative to national emission estimate for the industry: 
 Comparison of data on fuel or input material consumed by specific sources with fuel or input material purchasing data and data on stock changes, 
 Comparison of fuel or input material consumption data with fuel or input material purchasing data and data on stock changes, 
 Comparison of emission factors that have been calculated or obtained from the fuel or input material supplier, to national or international reference emission factors of comparable fuels or input materials 
 Comparison of emission factors based on fuel analyses to national or international reference emission factors of comparable fuels, or input materials, 
 Comparison of measured and calculated emissions (European Commission 2007). 

 Maintain data documentation, including comprehensive documentation of data received through personal communication.
 Check that changes in data or methodology are documented.

7. Options for Estimating Missing Data

For the emissions calculation based on petroleum coke and other data inputs, a complete record of all measured parameters is needed. Whenever a value of a required parameter is not available, a substitute data value for the missing parameter can be used in calculations. Options and considerations for missing data vary will vary depending on the proposed monitoring method. Each option would require a complete record of all measured parameters as well as parameters determined from company records that are used in the GHG emissions calculations (e.g., carbon contents, monthly fuel consumption, etc.).

7.1 Procedures for Option 1: Direct Measurement using CEMS
For options involving direct measurement of CO2 emissions using CEMS, Part 75 establishes procedures for the management of missing data. Specifically, the procedures for managing missing CO2 concentration data are specified in §75.35. In general, missing data from the operation of the CEMS may be replaced with substitute data to determine the CO2 emissions during the period for which CEMS data are missing. Section 75.35(a) requires the owner or operator of a unit with a CO2 CEMS to substitute for missing CO2 pollutant concentration data using the procedures specified in paragraphs (b) and (d) of §75.35; paragraph (b) covers operation of the system during the first 720 quality-assured operation hours for the CEMS, and paragraph (d) covers operation of the system after the first 720 quality-assured operating hours are completed. 

During the first 720 quality-assured monitor operating hours following initial certification at a particular unit or stack location, the owner or operator would be required to substitute CO2 pollutant concentration data according to the procedures in §75.31(b). That is, if prior quality assured data exist, the owner or operator would be required to substitute for each hour of missing data, the average of the data recorded by a certified monitor for the operating hour immediately preceding and immediately following the hour for which data are missing. If there are no prior quality-assured data, the owner or operator would have to substitute the maximum potential CO2 concentration for the missing data. 

Following the first 720 quality-assured monitor operating hours, the owner or operator would have to follow the same missing data procedures for SO2 specified in §75.33(b). The specific methods used to estimate missing data would depend on the monitor data availability and the duration of the missing data period.

7.2 Procedures for Option 2: Mass Balance and Combustion Method
For process sources that use a simplified emission calculation, no missing data procedures would apply because the emission calculation is derived from default emission factors and activity data. Businesses closely track activity data such as purchase and use of production inputs; therefore, 100 percent data availability would be expected.

For process sources that use a site-specific emission factor, no missing data procedures would apply because the site-specific emission factor is derived from an initial carbon content analysis from the petroleum coke supplier (carbon content analysis test) and used in each calculation. The same factor would be multiplied by the production rate or process input rate, which are readily available. Therefore, 100 percent data availability would be required.

8.  References 
ASTM International. Website accessed March 2023. https://www.astm.org/

Australian National Greenhouse and Energy Reporting (Measurement) Determination 2008, Division 4.3.4-Carbide production, July 1, 2021. 
https://www.legislation.gov.au/Series/F2008L02309

Butcher T, Harshman R, Konijnenburg J, Lee GD, Williams J, Warfield L, Benham E, Bowers S, and Lippa K (2022) Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. (National Institute of Standards and Technology, Gaithersburg, MD), NIST Handbook (HB) NIST HB 44-2023.  https://doi.org/10.6028/NIST.HB.44-2023

California Air Resource Board (CARB). Unofficial Electronic Version of the Regulation for the Mandatory Reporting of Greenhouse Gas Emissions. April 2019. https://ww2.arb.ca.gov/mrr-regulation.

Carbide Industries LLC. 2016. Calcium Carbide - Carbide Industries LLC (carbidellc.com). Last accessed April 5, 2023.

Environment and Climate Change Canada (ECCC). Canada's Greenhouse Gas Quantification Requirements. Version 4.0. December 2020. http://publications.gc.ca/collections/collection_2021/eccc/En81-28-2020-eng.pdf.

European Union (EU) 2007. Official Journal of the European Union, August 31, 2007. Commission Decision of 18 July 2007, Establishing guidelines for the monitoring and reporting of greenhouse gas emissions pursuant to Directive 2003/87/EC of the European Parliament and of the Council. Available at https://op.europa.eu/en/publication-detail/-/publication/77d4c46f-99a6-4a97-89fd-ca2f839d9b31/

European Union (EU) 2021. Commission Implementing Regulation (EU) 2018/2066 of 19 December 2018 on the Monitoring and Reporting of Greenhouse Gas Emissions Pursuant to Directive 2003/87/EC of the European Parliament and of the Council and Amending Commission Regulation (EU) No. 601/2012. January 1, 2021. 
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02018R2066-20210101&from=EN. 

IPCC, 2006. 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Volume 3, Industrial Processes and Product Use; Chapter 3.  Available at: https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol3.html   

IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.

Louisville Metro Air Pollution Control District. Title V Operating Permit, 
Effective 09/30/2019. Carbide Industries, LLC. https://louisvilleky.gov/government/air-pollution-control-district/title-v-operating-permits 

Office of Air and Radiation, U.S. Environmental Protection Agency (USEPA). 2009. Technical Support Document for Stationary Fuel Combustion Emissions: Proposed Rule for Mandatory Reporting of Greenhouse Gases, January 30, 2009. Docket Item No. EPA-HQ-OAR-2008-0508-0004.
U.S. Chemical Safety and Hazard Investigations Board (USCSHIB). 2013. Carbide Industries, LLC, Louisville, KY. Electric Arc Furnace Explosion. February 7, 2013. https://www.csb.gov/file.aspx?DocumentId=5665

U.S. Environmental Protection Agency (USEPA). 1995. AP 42, Fifth Edition, Volume I Chapter 11: Mineral Products Industry, 11.4 Calcium Carbide Manufacturing. https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-fifth-edition-volume-i-chapter-11-mineral-products-0 

U.S. Environmental Protection Agency (USEPA). Greenhouse Gas Reporting Program (GHGRP). Ferroalloy Production (40 CFR part 98, subpart K).

U.S. Environmental Protection Agency (USEPA). Greenhouse Gas Reporting Program (GHGRP). Silicon Carbide Production (40 CFR part 98, subpart BB).

