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How PM Benefits were calculated for Boiler MACT and Boiler Area Source Rule

Overall Goal: To produce benefit-per-ton estimates for major and area boilers to multiply by the 

anticipated emission reductions for the Boiler MACT and Boiler Area Source Rule

Step 1: Update Emissions Data

We used the information from the Boiler Information Collection Request (ICR) to update National 

Emissions Inventory (NEI). (Unable to incorporate all ICR data into NEI, as explained below)

 + =

Technical details are provided in “Air Quality Modeling Technical Support Document: Boiler Source Sector 

Rules”.

Step 2: Run Air Quality Model

The updated NEI is an input to the CAMx model, which converts emissions to ambient PM2.5 and ozone 

concentrations and mercury deposition.

-> =>

Step 3: Extract Air Quality Data

Using source apportionment in CAMx, we developed a national surface baseline (i.e., gridded air quality 

predictions). Also, we created surfaces that zero out primary PM2.5 and SO2 emissions from point and 

non-point boilers. We assume that point boilers are a surrogate for major boilers and non-point boilers 

are a surrogate for area boilers. We zero out these emissions to estimate the total impacts from boilers. 

=> 

Technical details are provided in “Air Quality Modeling Technical Support Document: Boiler Source Sector 

Rules”.

• Baseline PM2.5 surface

• Surface with no PM from point boilers

• Surface with no PM from non-point boilers

• Surface with no SO4 from point boilers

• Surface with no SO4 from non-point boilers 

Ambient PM2.5 and ozone 

concentrations and mercury 

deposition 

Updated NEI

(all emissions with 

updated boiler data)

Updated NEI

(all emissions with 

updated boiler data)

NEI

(all emissions)

Boiler ICR

data
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Step 4: Run Benefits Model

We ran the baseline and zero’d out surfaces through the BenMAP model to estimate total impacts 

(monetized benefits and incidence) associated with boilers (point and non-point) for both PM precursor

emissions (primary PM2.5 and SO2).

Baseline Air Quality Post-Policy Scenario Air Quality

Incremental Air Quality

Improvement

PM2.5

Reduction

Population

Ages 18-65

Background

Incidence

Rate

Effect

Estimate

Mortality 

Reduction

Step 2: Apply Health 

Impact Function

Technical details are provided in Chapter 7 of the Boiler RIA.

Step 5: Calculate Benefit-per-ton Estimates

We divided the total impacts by the modeled emissions from boilers to create boiler-specific benefitper-ton (BPT) estimates for point and non-point boilers. We assume that point boilers are a surrogate 

for major boilers and non-point boilers are a surrogate for area boilers. 

Total Impacts from Point Boilers PM 

Tons of PM from Point Boilers in Updated NEI

= BPTPM Major

Total Impacts from Non-Point Boilers PM 

Tons of PM from Non-Point Boilers in Updated NEI

= BPTPM Area

Repeat to calculate BPTSO2 Major and BPTSO2 Area. Technical details are provided in Chapter 7 of the Boiler 

RIA.

Step 6: Calculate Benefits of Regulatory Alternatives

We multiplied the new BPT estimates by the emission reductions associated with each regulatory 

alternative.

BPTSO2 Major * SO2 reductions = Benefits from SO2 for major sources

BPTPM Major * PM reductions = Benefits from PM for major sources
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BPTSO2 Area * SO2 reductions = Benefits from SO2 for area sources

BPTPM Area * PM reductions = Benefits from PM for area sources

Emission reductions associated with each regulatory alternative were calculated using average baseline 

emission factors for a model boiler and emission limits based on ICR data and permit limits. Technical 

details are provided in these docket memos: “Revised Development of Baseline Emission Factors for 

Boilers and Process Heaters at Commercial, Industrial, and Institutional Facilities” and “Revised 

Methodology for Estimating Cost and Emissions Impacts for Industrial, Commercial, Institutional Boilers 

and Process Heaters National Emission Standards for Hazardous Air Pollutants”.

Emission Differences

The table below shows the differences between the NEI and the baseline emissions used for the 

NESHAPs. It was impossible to fully reflect the updated ICR data for boilers in the NEI because some 

information was unavailable in the ICR including consistent Plant ID, geographic coordinates, SCC codes, 

stack height, exit temperature, exit velocity, speciation, etc. The NEI data and air quality modeling were 

only used to create updated BPT estimates specifically for the boiler sector. All of the emission 

reductions associated with the rule are calculated using the NESHAP emissions.

Facility* Pollutant NEI Baseline 

Emissions

NESHAP Baseline 

Emissions

Major

Existing

PM2.5 28,990 63,833

SO2 492,676 966,652

VOC 15,451 34,391

Hg 4 6.1

Major

New

PM2.5 - 30

SO2 - 610

VOC - 31

Hg - 0.01

Area

Existing

PM2.5 108,386 32,784

SO2 1,149,402 298,372

VOC 14,107 6,555

Hg - 4.4

Area

New

PM2.5 - 1,362

SO2 - 21,306

VOC - 631

Hg - 0.5

Total

Boilers

PM2.5 137,376 98,009

SO2 1,642,078 1,286,940

VOC 29,558 41,608

Hg 4 11

*We assume that point boilers are a surrogate for major boilers and non-point boilers are a surrogate 

for area boilers. However, some boilers affected by the Boiler MACT for major sources are in the nonpoint inventory in the NEI.