Emissions Calculations 101 Tim Trumbull Iowa Air Emissions Assistance Program Iowa Waste Reduction Center University of Northern Iowa

Estimating Emissions Developing emission control strategies Determining affects of sources and mitigation strategies Emissions Inventories Permit Applications

Estimation Hierarchy

Preferred Method of Estimating Emissions Continuous Emission Monitoring any monitoring effort that “continuously” measures ( I.e. very short averaging time) and records emissions Very expensive but most accurate

Second Best Method of Estimating Stack Test Data Short term scientific tests to quantify an emission rate Results are applicable only to the conditions existing at the time of the test Reliable and somewhat expensive

Third Method of Estimating Emissions Material Balance Reliable average emission rate For use when a high percentage of material is lost to the atmosphere May be inappropriate when a material is consumed or combined in a process Need to account for all materials going into and coming out of a process

Fourth Method of Estimating Emissions Emission Factors Ratios that relate emissions of a pollutant to an activity level that can be easily measured . Given an emission factor, simple multiplication can yield an estimate of emissions Represent typical values for an industry, not necessarily representative of a specific source

Fifth Method of Estimating Emissions Engineering Estimates Term applied to the best approximation that can be made when stack testing, material balance, or emission factors are not available.

Usually made by an engineer familiar with a specific process, and is based on process information

Material Balance: Commonly used for surface coating operations Required: Process rates, material used, material properties (from MSDS), and knowledge of process Example: Spray Paint Booth

Material Balance Sample Exercise

ACME’s Spray Paint Booth ACME Corp. applies a base coat and a top coat to each wagon it produces. The paint is sprayed directly from the container with no thinning or mixing. ACME has a federally enforceable paint usage limit of 2000 gallons per year. ACME sprayed 1,300 gallons last year (500 gallons of base coat and 800 gallons of topcoat). An HVLP spray gun with a maximum capacity of 7 gal./hr is used. The paint booth’s filters have a 95 percent particulate removal efficiency.

MSDS Information All percents are weight percents and expressed as a percent of total paint weight Top Coat Paint Weight (lbs/gal) % VOC % Solids % Xylene % Toluene % MEK 8 -- 2 8.75

25 75 Base Coat 7.21

42 58 2 15 ---

Step 1- Determine paint usage Since ACME has a usage limit of 2,000 gal/yr,this is the maximum amount of paint that they can use.

If this limit was not in place potential usage would be calculated as follows: Gun capacity x hours/yr = gallons / year 7.0 gal/hour x 8760 hr/yr = 61,320 gal./yr.

Step 2- Calculate Potential VOC and HAP emissions Top Coat Base Coat Use the highest constituent amount of VOC and HAPs from the base or top coat to calculate potential emissions.

First, determine which paint has the highest amount of VOC.: Paint Weight (lbs/gal) % VOC % Solids % Xylene % Toluene % MEK 8.75

25 75 8 -- 2 7.21

42 58 2 15 -- Base=7.21lb/gal x .42 = 3.02 lb/gal Top= 8.75 x .25 = 2.01 lb/gal

Step 2- Calculate Potential VOC and HAP emissions (cont) Density (lb/gal) x Usage Limit (gal/yr) x Max. % VOC x ton/2000 lb (7.21 lb/gal) x (2000 gal/yr) x 0.42

VOC x (1 ton / 2000 lbs) = 3.02 Tons / year VOC Use the same formula for each HAP but replace VOC % with the highest specific HAP % from the two coatings Xylene: 8.75 lb/gal x 2000 gal/yr x 0.08

x ton/2000 lb = 0.7 tons/yr Toluene: 8.75 lb/gal x 2000 gal/yr x 0.15

MEK: 8.75 lb/gal x 2000 gal/yr x 0.02

x ton/2000 lb = 1.31 tons/yr x ton/2000 lb = 0.18 tons/yr

Step 3 – Calculate Potential PM-10 Emissions To calculate PM-10 emissions the spray transfer efficiency (TE) of the spray gun and the control efficiency (CE) of the filter must be inserted into our earlier formula for VOC. Transfer Efficiency is the percentage of paint from the gun that adheres to the part being painted.

Step 3 – Potential PM-10 Emissions (Sample Transfer Efficiencies) Method of Spraying Flat Surface % Table Leg Surface % Bird Cage Surface % Air Atomized Airless Electrostatic Disk Airless Air Atomized 50 75-80 95 80 75 15 10 90-95 70 65 10 10 90-95 70 65

Step 3 – Calculate Potential PM-10 Emissions (cont) The HVLP gun has a transfer efficiency of 65% The filter control efficiency (CE) is 95% In ACME’s process, 65% of the paint sprayed hits the part and 35% enters the exhaust stream.

The filter captures 95% of the solids in the exhaust.

The remaining 5% is discharged up the stack

Step 3 – Potential PM-10 Emissions (cont) Calculations: Density (lb/gal) x Usage Limit x Max % solids x (1 TE ) x (1 CE ) x ton / 2000 lbs. = ton/yr PM-10 8.75 lb/gal x 2000 gal/yr x 0.75 x (1 -.65

) x (1-.

95 ) x ton/2000 lbs = 0.11 tons/yr PM-10 Top Coat 8.75

Base Coat 7.21

Paint Weight (lbs/gal) % VOC % Solids % Xylene % Toluene % MEK 25 75 8 -- 2 42 58 2 15 ---

Step 4- Calculate Maximum Hourly Emissions Multiply the capacity of the gun by the weight of the heaviest paint and by the highest percentage amount of each constituent. The paint density multiplied by the percent of the pollutant (by weight) equals a pound per gallon emission factor. To calculate hourly PM-10 emissions the transfer efficiency and collection efficiency must be included in the formula

Step 4- Calculate Maximum Hourly Emissions (cont.) Gun Capacity (gal/hr) x Density (lb/gal) x Max. % VOC/HAP = VOC or HAP Gun Capacity (gal/hr) x Density (lb/gal) x Max % PM-10 x (1-TE) x (1-CE) = PM-10 VOC’s= 7 gal/hr x (8.75 lb/gal x 0.42

) = 25.73 lb/hr VOC Xylene= 7 gal/hr x (8.75 lb/gal x 0.08

) = 4.9 lb/hr Xylene Toluene= 7 gal/hr x (8.75 lb/gal x 0.15

) = 9.19 lb/hr Toluene MEK= 7 gal/hr x (8.75 lb/gal x 0.02

) = 1.23 lb/hr MEK PM-10 7 gal/hr x (8.75 lb/gal x 0.75

) x (1-.65) x (1-.95)= 0.8 lb/hr PM

Step 5- Calculate Actual Annual VOC and Toxic Emissions Emissions from each coating must be calculated and added together.

Paint used (gal/yr) x Paint Weight (lb/gal) x Pollutant % x ton/2000 lbs. = Actual Tons/ year VOC-Top Coat 800 gal/yr x (8.75 lb/gal x 0.25) = 1,750 lb/yr x ton/2000 lb = 0.875 TPY VOC VOC- Base Coat 500 gal/yr x (7.21 lb/gal x 0.42) = 1,514 lb/yr x ton/2000 lb = 0.75 TPY VOC + 1.63 TPY VOC

Step 5- Calculate Actual Annual VOC and Toxic Emissions Xylene -Top Coat 800 gal/yr x (8.75 lb/gal x 0.08

) = 560 lb/yr x ton/2000 lb = 0.28 TPY Xylene Xylene- Base Coat 500 gal/yr x (7.21 lb/gal x 0.02

) = 72.1 lb/yr x ton/2000 lb = 0.04 TPY Xylene + 0.32 TPY Xylene Toluene -Top Coat 800 gal/yr x (8.75 lb/gal x 0.0

) = 0.0 lb/yr x ton/2000 lb = 0.00 TPY Toluene Toluene- Base Coat 500 gal/yr x (7.21 lb/gal x 0.15

)= 540.75 lb/yr x ton/2000 lb = 0.27 TPY Toluene + 0.27 TPY Toluene

Step 6- Calculating annual PM-10 Emissions Use the same formula with the incorporation of Transfer and Control Efficiencies: Top Coat: 800 gal/yr x (8.75 lb/gal x 0.75) x (1-.

65 ) x (1-.

95 ) = 122.5 lb/yr x ton/2000 lb = 0.05 Tons/yr PM-10 Base Coat: 800 gal/yr x (7.21 lb/gal x 0.58) x (1-.

65 ) x (1-.

95 ) = 63.09 lb/yr x ton/2000 lb = 0.02 Tons/yr PM-10 + 0.07 TPY PM-10

Emission Factors

Emission Factors An emission factor is a representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant.

In most cases, EF’s are an average of all available data of acceptable quality and are generally assumed to be long-term averages for all facilities in the source category.

Emission Factors General Equation for Emission Estimation: E = A x EF x (1-ER/100) Where: E = emissions A = activity rate EF = emission factor ER = overall emission reduction efficiency, % further, ER is the efficiency of the control system

Sources of Emission Factors AP-42- includes descriptions of activities that produce emissions FIRE- The Factor Information Retrieval Data System menu driven software Air CHIEF 9.0 CD-ROM- includes AP-42 and FIRE TANKS- estimates VOC & HAP emissions from tanks CHIEF Bulletin Board System- includes latest guidance and information on air emission inventories and emission factors available at: www.epa.gov/ttn/chief

Other Sources of Emission Factors: State Published Emission Factors Vendor Supplied Emission Factors

Emission Factor Example: ACME Company has a welding station that it uses to construct wagons. Process: Gas Metal Arc Welding, E308 electrode Maximum Feed Rate: 30 lb. electrode per hour Actual Throughput: 40,000 lbs. Electrode per year

Air CHIEF to find Emission Factors

ACME’s Welding Station SCC No. 30905212 Emission Factors: (HAPs from table 12.19-2) PM-10 5.4 lbs/1000 lb of electrode consumed Cr 0.524 lbs/1000 lb of electrode consumed Mn Ni 0.346 lbs/1000 lb of electrode consumed 0.184 lbs/1000 lb of electrode consumed

Step 1- Calculate Annual Potential Make sure units of rate and emission factor match.

30 lb/hr x lb/1000 lb = 0.03 1000 lb/hr 0.03 1000 lb/hr x 5.4 lb/1000 lb x 8760 hr/yr x ton/2000 lb =0.71 tons/yr PM-10 Potential Chromium = 0.07 tons/yr Potential Manganese = 0.05 tons/yr Potential Nickel = 0.02 tons/yr

Step 2- Calculate Actual Emission Actual PM-10 in tons per year 40 1000 lb/yr x 5.4 lb/1000 lb x ton/2000 lb =0.11 tons/yr Use the same formula for the other HAPs with their corresponding emission factors Actual Chromium = 0.01 tons/yr Actual Manganese = 0.01 tons/yr Actual Nickel = 0.00

Emission Factor Cautions: Because emission factors are an average, 50 percent of sources will have rates above or below the factor used Emission factors are neither emission limits nor standards If a factor for a pollutant is not available from EPA, this does not mean that the source does not emit a pollutant

Questions?

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