### 1 MEMORANDUM

TO: Hillary Ward, EPA

FROM: ERG

DATE: April 2014

SUBJECT: Estimating Secondary Impacts of the Landfills NSPS Review

The EPA is reviewing the new source performance standards (NSPS) for air emissions from municipal solid waste landfills (40 CFR part 60, subpart WWW). This memo presents the assumptions and equations used to calculate the secondary impacts that would result from the proposed new subpart XXX in 40 CFR part 60.

The proposed new subpart would affect the nation’s en ergy supply and is expected to generate a net increase in the nation’s energy supply. The combustion of landfill gas (LFG) also creates secondary air impacts in the form of by-product emissions, additi onal energy demand required to operate the control system, and avoided emissions from the national electrical grid as a result of new LFG energy supply.

The secondary impacts are computed for the year 202 3, which is 10 years after the NSPS is proposed. This is consistent with the presentation of the costs and emission impacts in the preamble. The methodologies for estimating costs and emission redu ctions are presented in the cost and emission impacts methodology memorandum 1 . The secondary impacts are computed on an incremental basis relative to the current NSPS requirements (baseline).

1. Distribution of Methane to Flares and Engines

The gas curve models (that were used to estimat e costs and emission reductions) compute the total amount of methane destroyed, as well as the total reve nue generated from the sale of electricity to the grid, by the current NSPS and the proposed 40 CF R part 60, subpart XXX. Using these values, it is possible to back calculate the amount of methane destro yed by the engines vs. the flares. Equations 1, 2, and 3 are used to determine the annual electricity produced (in megawatt hours per year or MWh/yr), the annual methane sent to engines (metric tons/yr), and the annual methane sent to flares (in cubic feet per year or ft 3 /yr) in 2023. These amounts are then used to compute the secondary impacts using equations

described in Sections 2 and 3 of this memorandum.

Equation 1: Quantity of Electricity Produced

Elec_Produced = Eng_Revenue ÷ Electricity_Price ÷ 1,000

Where: Elec_Produced = Electricity produced (2023), MWh/yr Eng_Revenue = $/yr (computed using equations in the cost and emission impacts methodology memorandum)

1 ERG. 2014. Methodology for Estimating Cost and Emission Impacts of Proposed MSW Landfill Regulations.

### 2 Electricity_Price = Average electricity price, $0.06297 per kWh 1,000 = Conversion factor, kW per MW

Equation 2: Quantity of Methane Sent to Engines

CH 4Engines = Elec_Produced × 11,100 × 1,000 ÷ 1,012 × 0.0423 ÷ 2,000 × 0.9072

Where:

CH 4Engines = Methane sent to engines (2023), metric ton/yr Elec_Produced = Electricity produced, MWh/yr, from Eqn. 1 11,100 = Engine heat rate, 11,100 Btu/kWh 1,000 = Conversion factor, kW per MW 1,012 = Heating value of methane, Btu/ ft 3 CH 4 0.0423 = Density of CH 4 , lb/ ft 3

2,000 = Conversion factor, lb/ton 0.9072 = Conversion factor, metric ton per short ton

Equation 3: Quantity of Methane Flared

CH 4flared = (CH 4Total - CH 4Engines ) × 2,000 ÷ 0.9072 ÷ 0.0423

Where:

CH 4flared = Methane sent to flares (2023), ft 3 /yr

CH 4Total = Methane destroyed, (2023), (computed using equations in cost and emission impacts methodology memorandum

, metric ton/yr)

CH 4Engines = Methane sent to engines, from Eqn. 2 2,000 = Conversion factor, lb/ton 0.9072 = Conversion factor, metric ton per short ton 0.0423 = Density of CH 4 , lb/ ft 3

2. Energy Impacts

As discussed in the cost and emission impacts methodology memorandum, 2 the regulatory options analysis assumes that landfills with sufficient gas to support an LFG engine that are located in areas with favorable electricity prices will install LFG e ngines as a least cost control alternative.

The energy impacts of the proposed 40 CFR part 60, subpart XXX are two-fold:

1. Energy demand to operate the bl owers of the LFG collection system. This energy is expected to be purchased from the grid for landfills that do no t have LFG electricity projects installed. For landfills with LFG engines installed, the engines ar e expected to provide this energy to the LFG collection system.

2. Energy supply from the LFG engines. Additional energy generated above what is required to operate the LFG collection system is exp ected to be sold to the local grid.

2 ERG. 2014. Methodology for Estimating Cost and Emission Impacts of Proposed MSW Landfill Regulations.

### 3 The net energy impacts can be estimated using the following equations:

Equation 4: Energy Demand

E_demand = CH 4 _flared × 0.002 × 2 ÷ 1,000

Where: E_demand = Energy demand (2023), MWh

CH 4 _flared = Quantity of methane flared in each option, ft 3 /yr, from Eqn. 3 0.002 = Energy demand of LFG collection system, kWh/ft 3 LFG (see cost and emission impacts methodology memorandum) 2 = Multiplier, methane in LFG, assuming 50% methane 1,000 = Conversion factor kW/MW

Equation 5: Net Energy Impact

E_Impact = Elec_Produced – E_demand

Where: Elec_Produced = Electricity produced (2023), MWh, from Eqn. 1 E_demand = Energy demand 2023, MWh, from Eqn. 4

Table 1 summarizes the energy impacts of the pr oposed 40 CFR part 60, subpart XXX. The proposed subpart XXX is expected to generate a net increase in the nation’s energy supply. The energy revenue provided from new LFG engine energy supply was estimat ed as part of the cost analysis; as described in the cost and emission impacts methodology memorandum. 3 Applying an average national electricity price of $0.0629/kWh to the net energy impact, the energy supply is also summarized in Table 1 for the proposed subpart XXX. Appendix A shows the detailed cal culations of the energy impacts for all of the regulatory options presented in the preamble.

Table 1 Summary of Incremental Energy Impacts of Proposed Subpart XXX in 2023 Above the

Current NSPS

Option Incremental Energy Demand (MWh) Incremental Energy Supply (MWh) Incremental Net Energy Impact (MWh) Incremental

Value of Net Energy Supply (2012$) Proposed subpart to

reduce NMOC

threshold to 40 Mg/yr 

### 674 42,421 42,421 $2,671

3. Secondary Air Impacts

In addition to the reduction of methane and NMOC emissions, the proposed subpart has secondary air impacts, which are expected to incur in three main components:

3 ERG. 2014. Methodology for Estimating Cost and Emission Impacts of Proposed MSW Landfill Regulations.

### 4 1. By-product emissions created from the combustion of LFG in flares or engines

2. Emissions created from purchasing energy from the grid to operate the blowers on the LFG collection system.

3. Avoiding or offsetting emissions from grid electricity by supplying new energy from LFG engines.

By-product Emissions from Flares or Engines

When LFG is controlled using engines or flares, combustion by-product emissions such as SO 2 and NOx are generated. In addition, trace amounts of LFG cons tituents, such as mercury (Hg), can be emitted in the engine or flare exhaust gas. Equations 6a and 6b an d 7a and 7b along with emission factors from Chapter

2 of EPA’s AP-42 4 were used to estimate the secondary air impacts resulting from the combustion of

LFG.

Equation 6a: NOx Emissions from Flares

NOx flare = EFNOx flare × CH 4 _flared ÷ 2,000

Where:

NOx flare = NOx emitted from flared LFG (2023), tpy

EFNOx flare = NOx emission factor, 40lb/ 10 6 dscf methane, from AP-42

CH 4 _flared = Quantity of methane flared (2023), dscf/yr 2,000 = Conversion factor lb/ton

Equation 6b: NOx Emissions from Engines

NOx engine = EFNOx engine ÷ 1,012 × 11,100 × 1,000 × Elec_Produced ÷ 2,000

Where:

NOx engine = NOx emitted from LFG engines (2023), tpy

EFNOx engines = NOx emission factor, 250 lb/ 10 6 dscf methane, from AP-42 1,012 = Methane heating value, Btu/scf 11,100 = Engine heat rate, Btu/kWh 1,000 = Conversion factor kW/MW Elec_Produced = Electricity produced 2023, MWh, from Eqn 1 2,000 = Conversion factor lb/ton

SO 2 emissions from the flare and engines vary depending on the sulfur content of the LFG. This analysis assumes all sulfur compounds in LFG are converted to SO 2 during combustion and uses the AP-42 default sulfur content for raw LFG rather than using landfill-specific data.

Equation 7a: SO 2 or Hg Emissions from Flares

Poll flare = Pconc LFG ÷ 10 6 × MW poll ÷ LFG std ×2 × CH4_flared ÷ 2000

Where:

Poll flare = Pollutant emitted from flared LFG (2023), tpy

4 USEPA. 1998. AP-42 Vol. I. Chapter 2.4. Muni cipal Solid Waste Landfills. Available on-line at: http://www.epa.gov/ttn/chief/a p42/ch02/final/c02s04.pdf.

### 5 Pconc LFG = Pollutant concentration of LFG 5 , ppmv MW Poll = Molecular weight of SO 2 (64.06) or Hg (200.61), lb/lb-mol

LFG std = LFG at standard conditions, 385.5 scf/lb-mol 2 = Multiplier, ratio of LFG to methane, assuming 50% methane

CH 4 _flared = Quantity of methane flared, (2023), dscf/yr, from Eqn 3 2,000 = Conversion factor lb/ton

Equation 7b: SO 2 or Hg Emissions from Engines

Poll eng = Pconc LFG ÷ 10 6 × MW poll ÷ LFG std *2 ÷ 1,012 × 1,000 × 11,100 × Elec_Produced ÷ 2,000

Where:

Poll eng = Pollutant emitted from LFG engines (2023), tpy

Pconc LFG = Pollutant concentration of LFG 6

MW Poll = Molecular weight of SO 2 (64.06) or Hg (200.61), lb/lb-mol

LFG std = LFG at standard conditions, 385.5, scf/lb-mol 2 = Multiplier, ratio of LFG to CH 4 , assuming 50% methane 1,012 = Methane heating value, Btu/scf 1,000 = Conversion factor kW/MW 11,100 = Engine heat rate, 11,100, Btu/kWh Elec_Produced = Electricity produced (2023), MWh, from Eqn. 1 2,000 = Conversion factor lb/ton

Emissions from Purchased Electricity

In addition to the emissions resulting directly fro m the combustion of LFG, there are also emissions associated with the energy demand to operate the LFG control system. The energy demand is quantified using Equation 2, and emission factors from EPA eGRID (9 th edition) 7 can be applied to estimate the emissions associated with this purchased electricity . While cap and trade mechanisms in place for SO 2 and NOx emissions in the electricity sector prev ent quantifying emissions resulting from purchased electricity, the eGRID factors can be used to estimate the increase in CO 2 and Hg emissions from purchased electricity. However, eGRID data are unavailable to estimate the impacts on CO or PM from purchased electricity.

The eGRID factors are presented as lb/MWh output a nd the data are available for an overall national average grid factor as well as an average of only fossil -fuel based electricity. For this analysis, the overall national grid average factors were chosen to estimate emissions because on average the purchased electricity would reflect the overall national average a nd not just electricity from fossil sources. The grid factors used in this analysis are documented in Tabl e 2. The most recent version of eGRID data does not include a factor for mercury, so the 2007 eGRID data set was used to estimate mercury emissions.

Equation 8: CO 2 or Hg Emissions from Grid Purchased Electricity

Poll grid = 0.002 × CH 4 _flared × 2 × EF grid ÷ 2,000 ÷ 1,000

Where:

5 Sulfur concentration is 46.9 ppmv, from AP-42 page 2.4-8; Hg concentration is 2.92E-04 ppmv from Table 2.4-1.

6 Sulfur concentration is 46.9 ppmv, from AP-42 page 2.4-8; Hg concentration is 2.92E-04 ppmv from Table 2.4-1.

7 USEPA. eGRID 9th Edition (2010 data). February 24, 2014. http://www.epa.gov/cleanenergy/energyresources/egrid/index.html.

### 6 Poll grid = Pollutant emitted from grid purchased electricity in 2023, tpy

EF grid = Emission factor from grid purchased electricity, lb/MWh from Table 2 0.002 = Electricity consumption by LFG collection blowers, kWh/ft 3 LFG CH4_flared = Quantity of CH 4 flared(2023), dscf/yr, from Eqn. 3 2 = Multiplier, ratio of LFG to CH 4 , assuming 50% methane 1,000 = Conversion factor kWh/MWh 2,000 = Conversion factor lb/ton

Table 2. eGRID Emission Factors Used in Impacts Analysis

Pollutant Factor (lb/MWh) Source Hg 27.2 eGRID2007 V1.1, national average, all sources

CO 2 1216.18 eGRID 9 th Edition (2010 Data) V1.0 , national average, all

sources

Avoided Emissions from Excess Energy Supply

The third component affecting overall secondary air impacts are the emissions avoided as a result of increased LFG energy production expected to occur as a result of the new subpart. LFG electricity sold to the grid is expected to offset the demand of pu rchased electricity from the national grid. The eGRID factors from Table 2 were used with Equation 9 to estimate the avoided air impacts.

Equation 9: Avoided CO 2 and Hg Emissions from LFG Energy Supply

Poll avoided = Elec_Produced × EF grid ÷ 2,000

Where:

Poll avoided = Pollutant avoided from grid electricity (2023), tpy

EF grid = Emission factor from avoided grid electricity, lb/MWh from Table 2 Elec_Produced = Average annual electricity produced (2023), MWh, from Eqn. 1 2,000 = Conversion factor lb/ton

Net Emissions Impact

Considering the three sources of emissions impacts from the proposed subpart, a net impact on emissions can be computed according to Equation 10 for each pollutant that was estimated using Equations 6 through 9 above.

Equation 10: Net Secondary Emissions Impact

Net Emissions = Poll eng + Poll flare + Poll grid - Poll avoided

Where: Net Emissions = Net emissions (2023), tpy

Poll eng = Pollutant emitted from LFG engines (2023), tpy

Poll flare = Pollutant emitted from flared LFG (2023), tpy

Poll grid = Pollutant emitted from grid purchased electricity (2023), tpy

Poll avoided = Pollutant avoided from grid electricity (2023), tpy

### 7 Table 3 summarizes the secondary air impacts of th e proposed subpart compared to the current NSPS requirements. The CO 2 emission reductions presented in this table are in addition to the CO 2 e emission

reductions achieved from the direct destruction of me thane in flares or engines. Appendix B shows the detailed calculations of the secondary air impacts for all of the regulatory options considered.

Table 3. Summary of Increment al Secondary Air Impacts for Proposed Subpart XXX in 2023

Pollutant Emissions Created (LFG Flares and

Engines) (tpy) Emissions Avoided (tpy) Net Emissions (tpy)

SO 2 

### 5 Cannot compute Cannot compute
Hg 

### 9 586 -577

NOx 

### 62 Cannot compute Cannot compute

CO 2 

### 415 26,554 -26,139