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M EMORANDUM

TO: Hillary Ward, EPA

FROM: ERG

DATE: June 2015

SUBJECT: Estimating Secondary Impacts of the Emission Guidelines for MSW Landfills

The EPA issued is proposing a review of the emission guidelines for air emissions from existing municipal solid waste landfills (40 CFR part 60, subpart Cc). This memo presents the assumptions and equations used to calculate the secondary impacts that would result from the proposed new subpart Cf in 40 CFR part 60.

The proposed new subpart would affect the nation’s energy 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, additional 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 2025. This is consistent with the presentation of the costs and emission impacts in the preamble. The methodologies for estimating costs and emission reductions are presented in the cost and emission impacts methodology memorandum 1 . The secondary impacts are computed on an incremental basis relative to the current emission guidelines requirements (baseline).

1. D istribution of Methane to Flares and Engines

Th e gas curve models (that were used to estimate costs and emission reductions) compute the total amount of methane destroyed, as well as the total revenue generated from the sale of electricity to the grid, by the current NSPS/emission guidelines and the proposed 40 CFR part 60, subpart Cf. Using these values, it is possible to back calculate the amount of methane destroyed 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 2025. 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 (2025), MWh/yr Eng_Revenue = $/yr (computed using equations in the cost and emission impacts methodology memorandum)

1 ERG. 2015. Updated Methodology for Estimating Cost and Emission Impacts of MSW Landfill Regulations.

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E lectricity_Price = Average electricity price, $0.0655 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 (2025), 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 (2025), ft 3 /yr

CH 4Total = Methane destroyed, (2025), (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. E nergy 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 engines as a least cost control alternative.

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

1. Energy demand to operate the blowers of the LFG collection system. This energy is expected to be purchased from the grid for landfills that do not have LFG electricity projects installed. For landfills with LFG engines installed, the engines are 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 expected to be sold to the local grid.

2 ERG. 2015. Updated Methodology for Estimating Cost and Emission Impacts of MSW Landfill Regulations.

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T he 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 (2025), 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 (2025), MWh, from Eqn. 1 E_demand = Energy demand 2025, MWh, from Eqn. 4

Appendix A summarizes the energy impacts of the proposed 40 CFR part 60, subpart Cf. The proposed subpart Cf is expected to generate a net increase in the nation’s energy supply. The energy revenue provided from new LFG engine energy supply was estimated as part of the cost analysis; as described in the cost and emission impacts methodology memorandum. 3 Applying an average national electricity price of $0.0655/kWh to the net energy supply, the value of the energy supply is also estimated in Appendix A for the proposed subpart Cf.

3. Secondary Air Impacts

I n 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:

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

W hen 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 constituents, such as mercury (Hg), can be emitted in the engine or flare exhaust gas. These emissions are expected to be relatively small and were not estimated.

Emissions from Purchased Electricity

3 ERG. 2015. Updated Methodology for Estimating Cost and Emission Impacts of MSW Landfill Regulations.

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I n addition to the emissions resulting directly from 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 4, and emission factors from EPA eGRID (9 th edition) 4 can be applied to estimate the CO 2 emissions associated with this purchased electricity. Purchased electricity is also expected to yield

emissions such as SO 2 and NOx and trace amounts of mercury (Hg). These emissions are expected to be relatively small and were not estimated.

Equation 6: CO 2 Emissions from Grid Purchased Electricity

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

Where:

Poll grid

= Pollutant emitted from grid purchased electricity in 2025, tpy

EF grid = Emission factor from grid purchased electricity, lb/MWh from Table 1 0.002 = Electricity consumption by LFG collection blowers, kWh/ft 3 LFG CH4_flared = Quantity of CH 4 flared(2025), 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 1. eGRID Emission Factors Used in Impacts Analysis

Pollutant Factor (lb/MWh) Source

CO 2 1232.35 eGRID 9 th Edition (2010 Data) V1.0, national average, all

sources

A voided Emissions from Excess Energy Supply

T he 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 purchased electricity from the national grid. The eGRID factors from Table 1 were used with Equation 7 to estimate the avoided air impacts.

Equation 7: Avoided CO 2 Emissions from LFG Energy Supply

Poll avoided = Elec_Produced × EF grid ÷ 2,000

Where:

Poll avoided = Pollutant avoided from grid electricity (2025), tpy

EF grid = Emission factor from avoided grid electricity, lb/MWh from Table 1 Elec_Produced = Average annual electricity produced (2025), MWh, from Eqn. 1
2,000 = Conversion factor lb/ton

Net Emissions Impact

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

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C onsidering the three sources of emissions impacts from the proposed subpart, a net impact on emissions can be computed according to Equation 8 for each pollutant that was estimated using Equations 6 and 7

above.

Equation 8: Net Secondary Emissions Impact

Net Emissions = Poll eng

+ Poll flare + Poll grid

- Poll avoided

Where: Net Emissions = Net emissions (2025), tpy

Poll eng = Pollutant emitted from LFG engines (2025), tpy

Poll flare = Pollutant emitted from flared LFG (2025), tpy

Poll grid = Pollutant emitted from grid purchased electricity (2025), tpy

Poll avoided = Pollutant avoided from grid electricity (2025), tpy

Appendix B shows the detailed calculations of the secondary air impacts for the proposed option.Appendix A: Annual Energy Impacts 2025: 6/30/15CH4 Flared (ft3/yr)EnergyNeeded toOperateBlowers onGCCS(MWh)MWhgeneratedfrom EnginesNet EnergyImpacts (MWh)Value of energysupply ($/yr)Energy Demandto Operate GCCS(MWh)Energy Supply(MWh)NetEnergyImpacts(MWh)Value ofenergysupply($/yr)1200,639,654,854802,559 19,579,04918,776,490$1,229,86013197,387,162,254789,54919,991,32719,201,778$1,257,716(13,010)412,278425,288$27,856Proposal 2.5/34Current NSPS requirements (40 CFRpart 60 subpart WWW)2.5/50Incremental ImpactsTotal ImpactsOptionAppendix B: Annual Secondary Air Impacts (2025): 6/30/15Flare + EnergyTotal Net EmissionsEmissionsCreatedEmissionsAvoidedEmissionsCreatedCO2 fromPurchasedElectricity forBlowers (tpy) CO2 Avoided CO2 CO2 (tpy)CO2 (tpy)CO2 (metrictpy)1200,639,654,854494,51619,579,04912,064,097494,516(11,569,581)Proposal 2.5/3413197,387,162,254486,49919,991,32712,318,132486,499(11,831,633)(262,051)(238,228)FlaringLFG ElectricityIncremental NetEmissionsCurrent NSPSrequirements (40 CFRpart 60 subpartWWW)(2.5/50)MWhgeneratedfrom EnginesCH4 Flared (ft3/yr)Option