Terminal operations: case study

Purpose

To provide terminal operations with guidance on how to report to the National Pollutant Release Inventory (NPRI).

Background Information

The NPRI defines a terminal operation as either:

  1. the use of storage tanks and associated equipment at a site used to store or transfer crude oil, artificial crude or intermediates of fuel products into or out of a pipeline,
    or
  2. the operating activities of a primary distribution installation normally equipped with floating roof tanks that receives gasoline by pipeline, railcar, marine vessel, or directly from a refinery.

The NPRI requires that terminal operations report for each substance (Parts 1 - 5) that met or exceeded its reporting threshold, regardless of the number of employees working at the facility. This is because even with very few staff, terminal operations can still release significant quantities of NPRI substances.

Terminal operations must report Part 4 substances (criteria air contaminants - CACs) from all sources, including any stationary combustion on site. Stationary combustion sources can be broken down into two categories: external combustion equipment and internal combustion equipment.

External combustion sources include boilers, heaters, flares, etc. These are sources where the combustion occurs under atmospheric conditions with excess air.

Internal combustion sources include equipment such as: reciprocating engines and generators. Internal combustion units are identified as ones in which combustion of the fuel takes place in a confined space and above atmospheric pressure. The expanding gases produced by the combustion are used to provide mechanical power.

Sources other than combustion that should be considered when performing the Part 4 CAC threshold calculations include, but are not limited to: equipment painting, storage tanks, storage piles, loading and unloading releases, spills, equipment leaks and road dust.

Scenario

This terminal operation has two crude oil storage tanks, a natural gas reciprocating engine to provide power to various pieces of equipment, and a diesel-fired back-up generator. During the reporting year, some of the tanks and process equipment were painted. This terminal is staffed with 1 full-time employee and 3 full-time contractors.

Step 1 - Identify Requirements

The first step is to identify the NPRI reporting requirements that apply to the facility. A terminal operation must consider all NPRI substances and sources when performing the threshold calculations. A report is required for each substance which meets or exceeds the reporting threshold. A complete list of all NPRI substances along with their reporting thresholds is available on the NPRI website.

Part 1A substances, have a 10-tonne manufactured, processed, or otherwise used (MPO) threshold. Part 1B substances are treated the same as Part 1A substances, but with lower mass and concentration thresholds.

Since Part 2 substances (polycyclic aromatic hydrocarbons - PAHs) are not incidentally manufactured at the terminal, these substances will not need to be considered by this facility.

Part 3 substances (dioxins, furans and hexachlorobenzene) need to be reported if any of 17 specified activities occur on-site. Since none of these 17 activities took place at the terminal, Part 3 substances will not need to be considered by this facility.

The terminal must consider all sources of Part 4 substances (CACs). Some sources include, but are not limited to, internal and external combustion, painting activities, storage tank releases, and loading and unloading activities. More information on these sources can be found in the Guide for Reporting to the National Pollutant Release Inventory.

If a report is required for total volatile organic compounds (VOCs) under Part 4, then reporting is required for each of the speciated VOCs listed in Part 5 that is released in a quantity of 1 tonne or more.

Step 2 - Identify the Emission Sources at the Facility

Based on a survey of emission sources at the terminal, the following sources were identified:

  • Source 1: Storage tanks - crude oil (one 67 000 barrel fixed roof tank and one 100 000 barrel floating roof tank)
  • Source 2: Painting the storage tanks and process equipment
  • Source 3: Reciprocating Engine - natural gas fired
  • Source 4: Reciprocating Engine - back up diesel generator

Step 3 - Threshold Calculations

Emission Source 1 - Storage tanks

Crude oil, the fixed roof tank holds 67 000 barrels (bbl), and the internal floating roof tank holds 100 000 bbl.

Identify the Substances of Concern
Material Safety Data Sheet for the crude oil contained in both tanks
Substance (composition/information on ingredients) CAS NumberFootnote1 Percent by weight
Benzene 71-43-2 0.16%
Crude Oil (containing paraffins, naphthalenes, and PAHs in concentrations of less than 1%) 8002-05-09 99.84%

Part 1A: Crude oil contains Part 1A substances such as: naphthalene and benzene in a concentration of less than 1%. These substances are not required to be reported when they are MPO at a concentration less than 1%.

Part 1B: This specific crude oil does not contain Part 1B substances.

Part 2: PAHs are found in the crude oil, however they are not incidentally manufactured at the terminal, therefore they do not need to be considered by the facility.

Part 3: Storage tanks are not one of the 17 specified activities that require the reporting of Part 3 substances.

Part 4: The storage of crude oil in tanks will release VOCs.

Identify the Method of Calculating Emissions

The acceptable methods of estimation are described in the Guide for Reporting to the National Pollutant Release Inventory.

This case study uses an emission factor and a model to estimate releases.

The following list includes possible sources of emission factors (in order of preference):

  • Site specific. Site specific emission factors are more accurate than published emission factors since they are developed specifically for the facility with site specific data,
    or
  • Obtained from equipment dealers. Some equipment dealers can provide emission factors for the equipment they supply,
    or
  • Obtained from using the US EPA's AP-42 document. AP-42: compilation of Air Pollutant Emission Factors, AP-42, Fifth Edition, Volume I: Stationary Point and Area Sources,
    or
  • WebFIRE. WebFIRE is a database and accessing software containing U.S. EPA's recommended emission estimation factors for criteria and hazardous air contaminants.
Calculate Emissions

For this crude oil storage tank (Source Classification Code - SCC 40301010), the emission factor from WebFIRE was used (with the appropriate conversion factor for imperial to metric) and is shown in Table 1.

Table 1: Emission Factor for the Release of VOCs from Storage Tanks (SCC 40301010)
NPRI Substance Emission Factor (kg/bbl storage capacity)
Volatile organic compound (VOC) 0.124

The general equation for estimating uncontrolled air releases using an emission factor is:

Emission (kg/year) = storage capacity (bbl) x EF (kg/bbl storage capacity)

Example Calculation - Emission Factors

67 000 Barrel Tank - fixed roof

  • VOC Emission = 67 000 bbl x 0.124 kg/bbl per year
  • VOC Emission = 8 308 kg
  • VOC Emission = 8.308 tonnes
Example Calculation - Emission Model

The emission model being used in this example was downloaded from the US EPA's website free of charge. The software is called TANKS and uses chemical and meteorological data, and the tank's specifications to generate emissions estimates for several types of storage tanks. To use the software, specific information about storage tank construction and the stored liquid is entered. More information on TANKS can be found in the NPRI Toolbox website.

100 000 bbl Tank - floating roof

The storage tank used in this case had the following specifications which were inputted into the TANKS model:

Tank Specifications

  • Tank Dimensions
    • Tank diameter is 100 ft
    • Tank volume is 4 200 000 gallons
    • Four turnover throughout the year
    • The tank has a self-supporting roof
  • Paint Characteristics
    • The internal shell condition is a gunite lining
    • The shell color/shade is white
    • The shell condition is good
    • The roof color/shade is white
    • The roof condition is good
  • Rim-Seal System
    • Primary seal is a liquid-mounted type
  • Deck Characteristics
    • Welded deck type
  • Deck Fitting/Status
    • One access hatch (24-in diameter), unbolted cover, gasket
    • One automatic gauge float well, bolted cover, gasket
    • One column well (24-in diameter), built-up col.- sliding cover, gasket
    • One gauge-hatch / sample well (8-in diameter), weighted mech. Actuation, Gasket.
    • One sample pip or well (24-in diameter), slotted pipe-sliding cover, no gasket.
  • Site Selection
    • The tank is located in the Calgary, Alberta area (Latitude -51, Longitude 114). The location is required to determine the climatic condition for the TANKS software. See the NPRI Toolbox for details on the software and the input information.
  • Tank Contents
    • To include the benzene portion in the TANKS model you will need to select "multiple liquid components with partial speciation." From the MSDS we know the species are crude oil and benzene.

Entering these parameters into the TANKS software, the amount of VOCs emitted is16 224.570 lb or 7.359 tonnes.

Emission Source 2 - Painting of Storage Tanks and Process Equipment

During the paint drying process, VOCs are released to air.

Last year approximately 5 000 L of Paint ABC was used to paint the two storage tanks and process equipment.

Identify the Substances of Concern
Material Safety Data Sheet for Paint ABC
Section 1: Chemical Product and Company Identification
Product Names: PAINT ABC
Supplier: ABC INC
Specific Gravity: 1.03
Section 2: Composition / Information on Ingredients
Chemical Name CAS NumberFootnote1 Percent by Weight
Methyl ethyl ketone 78-93-3 30%
Xylene 1330-20-7 20%
Ethylbenzene 100-41-4 15%
n-Butyl alcohol 71-36-3 25%
Carbon Black 133-86-4 <3%
Other   balance
Section 3: Physical and Chemical Properties
  Specific Gravity Percent Volatile
Methyl ethyl ketone 0.805 100%
Ethylbenzene 0.867 100%
Xylene 0.867 100%
N-Butyl alcohol 0.810 100%

Part 1A: The Paint ABC contains the Part 1A substances methyl ethyl ketone, xylene, ethylbenzene, and n-butyl alcohol in a concentration greater than 1%. These substances are reportable when in a concentration of 1% or greater.

Part 1B: The paint contains no Part 1B substances.

Part 2: The paint contains no Part 2 substances.

Part 3: Painting is not one of the 17 specified activities that require the reporting of Part 3 substances.

Part 4: Methyl ethyl ketone, xylene, ethylbenzene, and n-butyl alcohol are also VOCs and need to be added together to determine the amount of total VOCs are released due to the paint activities. Total VOCs are the only Part 4 substance of concern for painting processes.

Identify the Method of Calculating Emissions

Part 1A Substances: Since there are no emission factors available for this type of operation the appropriate estimation method is to use a mass balance.

The general mass balance equation is:

  • Me = Mi - Mo - Ma - Mr

Where:

  • Me = Mass of coating compound emitted
  • Mi = Mass of coating compound in input stream. In this case Mi is the mass of the substance in the coating being applied.
  • Mo = Mass of coating compound in the output stream in the finished product. For this scenario, the amount of the substance in the finished product is zero, due to the 100% volatility.
  • Ma = Mass of coating compound accumulated in the system. Due to the nature of the activity there is no accumulation of the substance so Ma is zero.
  • Mr = Mass of coating compound captured for recovery or disposal. This term would be required, if for example the coating was conducted in a sealed environment, where some or all of the substances released were captured for recovery or disposal - this is not the case for this scenario so it is also zero.

For the given scenario, the general mass balance equation reduces to: Me = Mi

Calculate Emissions

To apply the mass balance the substance content in the coating compound must be determined. In many instances, the MSDS for that compound will indicate percent weight content of the predominate substances. The annual consumption of the compound could be obtained from the facilities operation log or sales slips.

It is assumed that all VOC substances in "Paint ABC" were released to air. The following equation will be used to determine the amount of each of the Part 1A substances released to air, and is based on the specific gravity and percent volatiles.

Example Calculation
  • Me = Mi = Q x D x c

Where:

  • Me = Total uncontrolled emission, kg
  • Q = Total annual consumption of coating material, litres = 5 000  litres
  • D = Density of coating material, kg/litre from MSDS. Note that the specific gravity (SG) of substances is usually supplied in Section 3: Physical and Chemical Properties of the MSDS. To convert the SG to density, into units of kg/litre, multiply the SG by the density of water, 1 kg/litre.
  • c = Percent Volatile content by weight in coating material (from MSDS)

Me Methyl ethlyl ketone = 5 000 litres x (1.03 kg/litres) x (30 kg / 100 kg)
Me Methyl ethlyl ketone = 1 545 kg
Me Methyl ethlyl ketone = 1.545 tonnes

Me Xylene = 5 000 litres x (1.03 kg/litres) x (20 kg / 100 kg)
Me Xylene = 1030 kg
Me Xylene = 1.030 tonnes

Me Ethyl benzene = 5 000 litres x (1.03 kg/litres) x (15 kg / 100 kg)
Me Ethyl benzene = 772.5 kg
Me Ethyl benzene = 0.773 tonnes

Me n-Butyl alcohol = 5 000 litres x (1.03 kg/litres) x (25 kg / 100 kg)
Me n-Butyl alcohol = 1 287.5 kg
Me n-Butyl alcohol = 1.288 tonnes

Part 4 Substances: The Part 1A VOCs released due to the painting process can be added together to calculate the total VOCs released due to the painting activities.

Example Calculation
  • Total VOCs = Methyl ethyl ketone + Xylene + Ethylbenzene + n-Butyl alcohol
  • Total VOCs = (1.545 + 1.030 + 0.773 + 1.288) tonnes
  • Total VOCs = 4.635 tonnes

Emissions Source 3 - Reciprocating Engine - Natural Gas

Identify the Substances of Concern

The only substances of concern released from the internal combustion engine are Part 4 substances.

Identify the Method of Calculating Emissions

Since the facility did not have any monitoring system installed, an appropriate method to use is emission factors. Determine if there are any manufacturer-supplied, or site-specific emission factors for the natural gas engine. If these are not available reference the US EPA's AP-42 or the latest version of FIRE database.

Calculate Emissions

In this case study, the emission factors from WebFIRE were used (Table 2). For the natural gas reciprocating engine in this case study, the following is required to select the appropriate emission factors:

  • The internal combustion engine is a for 2-cycle, lean burn, natural gas reciprocating engine (SCC 20200252)
  • The engine was operated with no emission control devices
  • The engine was operating at 100% of rated load
Table 2: Uncontrolled Emission Factors for the Combustion of Natural Gas in a Reciprocating Engine (SCC 20200252)
NPRI Substance Emission Factor (kg/GJ of Natural Gas)
NOxFootnote* 1.363
SO2 0.0002528
CO* 0.166
VOC 0.052
TPMFootnote** 0.017
PM10 0.017
PM2.5 0.017

For this scenario, the natural gas engine had an annual consumption of 46 320 gigajoules of natural gas per year (GJ/yr)

The general equation that is used for estimating uncontrolled emission from natural gas combustion is:

Emission (kg / year) = fuel burned (GJ / year) x EF (kg / GL)

Example Calculation
  • VOC emissions = (46 320 GJ/yr) x (0.052 kg/GJ)
  • VOC emissions = 2 408.64 kg
  • VOC emissions = 2.408 tonnes

The same method is used to calculate the remaining CAC emissions using emission factors provided in Table 2.

Table 3: Uncontrolled Annual CAC Releases from the Combustion of Natural Gas in a Reciprocating Engine
NPRI Substance Annual Uncontrolled Emissions (tonnes)
NOx 63.134
SO2 0.012
CO 7.689
VOC 2.408
TPM 0.787
PM10 0.787
PM2.5 0.787

Emissions Source 4 - Reciprocating Engine - Backup Diesel

Identify the Substances of Concern

The only substances of concern released from the reciprocating engine are Part 4 substances.

Identify the Method of Calculating Emissions

Since the facility did not have a monitoring system, an appropriate method to use is emission factors. Determine if there are any manufacturer-supplied or site-specific emission factors for the diesel fuel engine. If these are not available, reference the US EPA's AP-42 or the latest version of the FIRE database.

Calculate Emissions

In this case study, the emission factors from WebFIRE were used (Table 4). For the diesel fuel reciprocating engine in this case study, the following is required to select the appropriate emission factors:

  • The internal combustion engine is a diesel reciprocating engine (SCC 20300101)
  • The engine was operated with no emissions control devices
  • The engine was operating at 100% of rated load
Table 4: Uncontrolled Emission Factors for the Combustion of Diesel in Reciprocating Engine (SCC 20300101)
NPRI Substance Emission Factor (kg/cubic metre of diesel)
NOx 72.375
SO2Footnote*** 4.757
CO 15.577
VOC 0
TPM 5.093
PM10 5.093
PM2.5 5.093

For this scenario, the diesel engine had an annual consumption of 6 cubic metres of diesel fuel per year (m3/year).

The general equation that is used for estimating uncontrolled emissions from the combustion of diesel is:

Emission (kg / year) = fuel burned (m3) x EF (kg/m3)

Example Calculation
  • TPM emissions = 6m3 x 5.093 kg/m3
  • TPM emissions = 30.558 kg
  • TPM emissions = 0.031 tonnes

The same method is utilized to calculate the remaining CAC emissions using emission factors provided in Table 4.

Table 5: Uncontrolled Annual CAC Releases from the Combustion of Diesel in a Reciprocating Engine
NPRI Substance Annual Uncontrolled Emissions (tonnes)
NOx 0.434
SO2Footnote*** 0.003
CO 0.093
VOC 0
TPM 0.031
PM10 0.031
PM2.5 0.031

Step 4 - Add Emissions from All Sources

After calculating emissions from each source at the facility, the next step is to add emissions from each source and calculate the total emissions from the facility to determine if the NPRI thresholds were met.

Total facility Part 1-3 emissions

Based on the threshold calculations no report is required for Parts 1-3 substances. The only source meeting the Part 1 concentration threshold was the painting activity. However, the mass balance calculation for this activity showed that none of the 4 substances met the 10-tonne reporting threshold, therefore substance reports are not required. Part 2 substances are in the crude oil storage tanks. However, in this situation, these substances were not incidentally manufactured and therefore no substance reports are required. Finally, substance reports for Part 3 substances are not required since none of the activity triggers were met.

Total facility Part 4 emission (CAC emissions)

Table 6: Total Facility Emissions
Sources NPRI Substance Releases (tonnes)
NOx SO2 CO VOCs TPM PM10 PM2.5
Fixed Roof Tank 0 0 0 8.308 0 0 0
Floating Roof Tank 0 0 0 7.359 0 0 0
Painting 0 0 0 4.635 0 0 0
Natural Gas Engine 63.134 0.012 7.689 2.408 0.787 0.787 0.787
Diesel Engine 0.434 0.003 0.093 0 0.031 0.031 0.031
 TOTAL 63.568 0.015 7.782 22.710 0.818 0.818 0.818

NPRI Reporting Determination for CACs

Table 7: Comparison of Annual Emissions to the NPRI Reporting Thresholds
NPRI Substance Total Emission (tonnes/year) NPRI Facility Threshold (tonnes/year) NPRI Threshold Exceeded (?) Rationale
NOx 63.568 20 Yes Facility emission is > than NPRI threshold
SO2 0.015 20 No Facility emission is < than NPRI threshold
CO 7.782 20 No Facility emission is < than NPRI threshold
VOC 22.710 10 Yes Facility emission is > than NPRI threshold
TPM 0.818 20 No Facility emission is < than NPRI threshold
PM10 0.818 0.5 Yes Facility emission is > than NPRI threshold
PM2.5 0.818 0.3 Yes Facility emission is > than NPRI threshold

Step 5 - How to Report Facility Emissions

The on-line reporting system is available here.

Report all air releases of the NPRI substances that met the air release threshold (Table 7). Air releases are broken down into the following categories.

Stack or point releases - For this case study, this will include,

  • Storage tanks
  • Reciprocating Engines

Fugitive releases - Air releases that are not released through stacks or points. For this case study, this includes the:

  • Painting of storage tanks and process equipment

Step 6 - Speciated VOC Calculations

Since the Part 4 total VOC emissions were required to be reported, speciated VOC calculations are required. A report is required for each of the speciated VOCs that is released to air in a quantity of 1 tonne or greater.

Methyl ethyl ketone, xylene, and n-butyl alcohol were each released to air in quantities of more than 1 tonne from the painting activities. Even though these substances were not required to be reported under Part 1A, a report is required for each of them under Part 5. Ethyl benzene was also released to air during the painting activities, but the release quantity was less than 1 tonne, therefore, a report for ethyl benzene under Part 5 is not required.

Step 7 - Calculate the Monthly Breakdown of Annual Releases to Air by Percentage

Detailed emission estimates show that the facility is required to report to the NPRI. Additional reporting such as monthly breakdown of emissions by percentage for each pollutant must be reported. The general equation and methodologies for estimation monthly emissions is the same as the annual emissions for each source.

Example

Usage of natural gas, diesel fuel, paint, and crude oil for each month is obtained from facility records. You can calculate emissions for each month and add the total to determine the annual emissions. Using the annual total, calculate the monthly emission percentage using the following equation:

January emission percentage = (January emission / Total annual emission) X 100%

For example, add the VOC emission from each source for the month of January. If the January emission of VOC from the emission sources is 15.700 tonnes, the January percentage VOC emission is:

January emission percentage = (15.700 tonnes / 22.710 tonnes) X 100%

January emission percentage = 69.13%

The percentage for months must total 100%.

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