Comparison of VOC emissions impact from addition of PV-Vent requirement to addition of exemption for salvage yard operators


Data and Assumptions for PV-Vent Calculation:

1.  The PV-Vent requirement will affect approximately 390 facilities not currently required to have such devices.  (Source: Background Document for Proposed Revisions to 310 CMR 7.24(6), Dispensing of Motor Vehicle Fuel (The Stage II Vapor Recovery Program); pg. 6).

2.  The average gasoline throughput at these facilities is 500,000 gallons / yr.  (Source: pg. 7 of the reference cited in assumption 1.)

3.  PV-vents reduce emissions by 90%.  (Source: July 19, 2000 letter from Region 1 to CT-DEP)

4.  Breathing losses (VOC emissions) from tanks without PV vents = 1 lb VOC per 1,000 gallons of throughput.  (Source: EPA's AP 42, Table 5.2-7) 


Calculation:


(390 stations add PV-Vents) * (500,000 gallons / station) = 195,000,000 gallons of gas newly subject to this requirement.

195,000,000 gallons * 1 lb VOC / 1,000 gallons of throughput =  195,000 lbs of uncontrolled VOC emissions.

195,000 lbs uncontrolled emissions * 0.9 (90% control efficiency) = 175,500 lbs VOC controlled (87.7 tons / yr emission reduction).
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Data and Assumptions for salvage yard calculation:

1.  Number of registered motor vehicles in Massachusetts = 5,333,915.  (Source: US DOT; Federal Highway Administration; Highway Statistics Series; State Motor Vehicle Registrations  -  2010; Table MV-1; December, 2011).

2.  National average vehicle scrappage rate = 4.3%.  (Source: National Automobile Dealers Association; State of the Industry Report, 2011, pg. 16)

3.  5 gallons of gas recovered per scrapped vehicle (my assumption)

4.  Uncontrolled filling of storage tank: 11.5 lbs VOC / 1,000 gallons (Source: Table 5.27 of AP-42)

5.  Uncontrolled vehicle refueling: 11.0 lbs VOC / 1,000 gallons (Source: Table 5.27 of AP-42)

6.  Breathing loss (VOC emissions) from tanks without PV vents = 1 lb VOC per 1,000 gallons of throughput.  (Source: EPA's AP 42, Table 5.2-7)


Calculation:


(5,333,915 MA vehicles) * (0.043 scrappage rate) = 229,358 vehicles scrapped 

(229,358 vehicles scrapped) * (5 gallons gas/vehicle) = 1,146,790 gallons of gas recovered at scrap yards.

(1,146,790 gallons gas) * (23.5 lbs VOC / 1,000 gallons (combined emission rate)) = 26,950 lbs VOC emitted (13.5 tons/year)


Comparison:  the PV vent requirement being added to the Massachusetts Stage 2 regulation will reduce VOC emissions by approximately 88 tons per year, whereas exempting salvage yards will increase VOC emissions by approximately 14 tons/year.



