Emissions Calculations 101Tim TrumbullIowa Air Emissions Assistance ProgramIowa Waste Reduction CenterUniversity of Northern Iowa

Estimating EmissionsDeveloping emission control strategiesDetermining affects of sources and mitigation strategiesEmissions InventoriesPermit Applications

Estimation Hierarchy

Preferred Method of Estimating Emissions

Continuous Emission Monitoringany monitoring effort that “continuously” measures ( I.e. very short averaging time) and records emissionsVery expensive but most accurate

Second Best Method of EstimatingStack Test DataShort term scientific tests to quantify an emission rateResults are applicable only to the conditions existing at the time of the testReliable and somewhat expensive

Third Method of Estimating Emissions

Material BalanceReliable average emission rateFor use when a high percentage of material is lost to the atmosphereMay be inappropriate when a material is consumed or combined in a processNeed to account for all materials going into and coming out of a process

Fourth Method of Estimating Emissions

Emission FactorsRatios 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 emissionsRepresent typical values for an industry, not necessarily representative of a specific source

Fifth Method of Estimating Emissions

Engineering EstimatesTerm 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 operationsRequired: Process rates, material used, material properties (from MSDS), and knowledge of processExample: Spray Paint Booth

Material Balance

Sample Exercise

ACME’s Spray Paint BoothACME 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 InformationAll percents are weight percents and expressed as a percent of total paint weight Top Coat Base Coat

Paint Weight (lbs/gal) 8.75 7.21

% VOC 25 42

% Solids 75 58

% Xylene 8 2

% Toluene --- 15

% MEK 2 ---

Step 1- Determine paint usageSince 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

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.:Base=7.21lb/gal x .42 = 3.02 lb/galTop= 8.75 x .25 = 2.01 lb/gal

Top Coat

Base Coat

Paint Weight (lbs/gal)

8.75 7.21

% VOC 25 42

% Solids 75 58

% Xylene 8 2

% Toluene --- 15

% MEK 2 ---

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/yrToluene: 8.75 lb/gal x 2000 gal/yr x 0.15 x ton/2000 lb = 1.31 tons/yrMEK: 8.75 lb/gal x 2000 gal/yr x 0.02 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 50 15 10

Airless 75-80 10 10

Electrostatic Disk Airless Air Atomized

958075

90-957065

90-957065

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-108.75 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 Base Coat

Paint Weight (lbs/gal)

8.75 7.21

% VOC 25 42

% Solids 75 58

% Xylene 8 2

% Toluene --- 15

% MEK 2 ---

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 HAPGun 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 VOCXylene= 7 gal/hr x (8.75 lb/gal x 0.08) = 4.9 lb/hr XyleneToluene= 7 gal/hr x (8.75 lb/gal x 0.15) = 9.19 lb/hr TolueneMEK= 7 gal/hr x (8.75 lb/gal x 0.02) = 1.23 lb/hr MEKPM-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 EmissionsEmissions 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 Coat800 gal/yr x (8.75 lb/gal x 0.25) = 1,750 lb/yr x ton/2000 lb = 0.875 TPY VOCVOC- Base Coat500 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 Coat800 gal/yr x (8.75 lb/gal x 0.08) = 560 lb/yr x ton/2000 lb = 0.28 TPY XyleneXylene- Base Coat500 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 XyleneToluene -Top Coat800 gal/yr x (8.75 lb/gal x 0.0) = 0.0 lb/yr x ton/2000 lb = 0.00 TPY TolueneToluene- Base Coat500 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-10Base 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 FactorsAn 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 FactorsGeneral Equation for Emission Estimation:

E = A x EF x (1-ER/100)Where:E = emissionsA = activity rateEF = emission factorER = overall emission reduction efficiency, % further, ER is the efficiency of the control system

Sources of Emission FactorsAP-42- includes descriptions of activities that produce emissionsFIRE- The Factor Information Retrieval Data System menu driven softwareAir CHIEF 9.0 CD-ROM- includes AP-42 and FIRETANKS- estimates VOC & HAP emissions from tanksCHIEF 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 FactorsVendor Supplied Emission Factors

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

Air CHIEF to find Emission Factors

ACME’s Welding StationSCC No. 30905212Emission Factors:

(HAPs from table 12.19-2)

PM-10 5.4 lbs/1000 lb of electrode consumedCr 0.524 lbs/1000 lb of electrode consumedMn 0.346 lbs/1000 lb of electrode consumedNi 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-10Potential Chromium = 0.07 tons/yrPotential Manganese = 0.05 tons/yrPotential Nickel = 0.02 tons/yr

Step 2- Calculate Actual EmissionActual 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/yrActual Manganese = 0.01 tons/yrActual Nickel = 0.00

Emission Factor Cautions:Because emission factors are an average, 50 percent of sources will have rates above or below the factor usedEmission 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?

Contact Info:Phone: 800-422-3109E-mail: trumbull@uni.edu