2 Attachments

Anita: Thank you for posing the questions (in the January 27, 2012 e- mails below) about biogenic VOC emissions in Tables 2 and 5 of the 2005 EPA FR notice that ap proved the one-hour ozone maintenance plan and redesignated the area to attainment. It took us a wh ile to respond because we had to retrieve the land use and biogenic data for the one-hour ozone maintenance pl an from the archives. The results of our analysis are described below. Please let us know if you have an y additional questions or concerns. cda

Response to question on Table 2: The 1990 and 1999 biogenic VOC emissions in Table 2 (Page 13430, FR Vol. 70, No. 53) are not comparable because the bio genic emissions were obtained from different plans (i.e., the 1993 MAG ozone plan versus the 2004 MAG one-hour oz one maintenance plan). These plans used different biogenic emissions models (PC- BEIS vs. MAGBEIS2), emissions factors, land use cat egories, and meteorological data to derive biogenic emissions. Note that the 1 993 plan did not provide a comparative estimate of biogenic NOx emissions because the PC-BEIS biogenic model do es not calculate biogenic NOx emissions. Response to question on Table 5: The biogenic emissions in Table 5 (Page 13437, FR Vol. 70, No. 53) were
derived from the 2004 MAG one

- hour ozone maintenance plan, using the MAGBEIS2 mod el. The increase in



### FW: Biogenic VOCs

CATHY ARTHUR

to:

Anita Lee 02/08/2012 10:49 AM

Cc: tshin, lbauer, mpoppen
Hide Details From: CATHY ARTHUR <cathyarthur@msn.com>

To: Anita Lee/R9/USEPA/US@EPA

Cc: <tshin@azmag.gov>, <lbauer@azmag.gov>, <mpoppen @azmag.gov>

History: This message has been replied to and forwa rded.

2000&2004_MAG_Land_Use & Boundaries.pdf 1-Hr & 8-Hr O3 EF and Land use comparison.xlsx 

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...biogenic VOC emissions in this table is due to the predominance of urban land uses in the one-hour ozo ne

nonattainment area, compared with the much larger m odeling domain. A map comparing the land uses in the
one-hour ozone nonattainment area with the one-hour ozone modeling domain is provided in the attached Figure 1. Table A (attached) compares the proportion of urban and non-urban land uses for the nonattainment area (5,336 sq. km.) and modeling domain (15,824 sq. km. ). For both the nonattainment area and modeling d omain, the 2000, 2006 and 2015 land use data were derived from the MAG 2000 land use/cover and MAG projected
2010 and 2020 land use/cover data which were availa ble at the time. As shown in Tables B and C, the increase in biogenic VOC emissions in the nonattainment area between 2000 and 2015 is due to a 14.4% increase i n urban land uses, including commercial, residential, park/golf course, and non-emitting (i.e., transpor tation, airport, and parking) areas, at the expense of agricultural and desert/desert park areas. In the modeling dom ain, the increase in urban land uses is only 6.1% and the re duction in agricultural and desert/desert park land more than offsets the increase in VOC emissions due to growth in urban land use. Table A shows that the biogen ic VOC
emissions for the one-hour ozone nonattainment area increase between 2000 and 2015, whereas these emissions decline for the larger one-hour ozone mod eling domain. In the MAG 2007 eight-hour ozone plan, the 2004 bas e year biogenic source emissions for the 4-km model ing domain were obtained by applying the MAG MEGAN mode l to MAG 2004 land use/cover data. The MEGAN model was developed by ENVIRON based on a 2006 fiel d study in Maricopa County that measured biogenic emission factors for local desert plants, agricultu ral vegetation and trees. The biogenic emissions in the eighthour ozone modeling domain were held constant from the base year of 2004 through the attainment year 2 008, because there was no projected MAG land use/cover d ata available for the attainment year of 2008. It is important to note that EPA guidance for emissions i nventory projections (www.epa.gov/ttn/chief/eiip/techreport/volume10/x01 .pdf ) does not provide any steps or sources of national l and use data needed to estimate future biogenic emissio ns. In addition, a recent EPA study of emissions inventories also held biogenic emissions constant between the b ase year of 2005 and the future years 2012 and 2014 (Page 6, Emissions Inventories, US EPA, June 2010, Docket ID No. EPA-HQ-OAR-2009-0491). In the 2004 land use/cover data, urban land use (co mmercial, residential, parks/golf course, and trans portation) represents 26.9% of the eight-hour ozone nonattainm ent area (Table D) versus 39.1% of the one-hour ozo ne nonattainment area in 2006 (Table A). This differen ce is due to the fact that the eight-hour ozone non attainment
area is1.34 times larger than the one-hour ozone nonattainment area and therefore, includes a much larger proportion of non-urban land uses. A map of the l and uses in the eight-hour ozone nonattainment area and eight-hour ozone modeling domain is provided in Fig ure 2. In addition, the MEGAN biogenic emissions f actors differ significantly from MAGBEIS2. The MEGAN VOC e mission factor for residential areas is 441.8 ug/m2 /hr versus 668.5 ug/m2/hr for MAGBEIS2, while the MEGAN VOC emission factor is 2,221 ug/m2/hr for agricult ure compared with the MAGBEIS2 factor of 125.3 ug/m2/hr (Tables E and F). Due to the increased size of t he eighthour ozone nonattainment area and the major changes in emission factors attributable to different mode ls, the biogenic VOC emission increase due to urban growth is more than offset by the reduction in biogenic VO C emissions caused by decreases in agricultural and d esert/desert park land areas.

In conclusion, holding biogenic emissions constant between the base year of 2004 and the attainment ye ar of 2008 in the 2007 eight-hour ozone plan is considere d to be a reasonable and conservative assumption.

From: Anita Lee [ mailto:Lee.Anita@epamail.epa.gov ]

Sent: Friday, January 27, 2012 2:56 PM

To: Cathy Arthur; Lindy Bauer; Matthew Poppen; Taejoo Shin Subject: Biogenic VOCs

Hello again,

Apologies for the multiple emails.

See also Table 5 of the same FR notice. It shows th at over 1999, 2006, and 2015, that biogenic VOC emissions go up and biogenic NOx emissions go d own. There is also a corresponding discussion that includes statements of increasing r esidential land use at the expense of agricultural land use, and that residential land use is expected to have a higher biogenic VOC emission factor than agricultural land. I realize the FR notice was written by EPA, so if this information does not correctly characterize the modeling from MAG, pleas e also feel free to let me know that.

Thanks again!

anita 

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Anita Lee, PhD

Environmental Scientist US EPA, Region 9 Air Planning Office 75 Hawthorne Street (AIR-2) San Francisco, CA 94105

ph: (415) 972-3958 fax: (415) 947-3579

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Hello all,

Thanks so much for your call today.

I found the table that made me think biogenic VOC e missions would increase with the urbanized

land use - It's from 70 FR 13425 (March 21, 2005). Table 2 on page 13430 shows estimated values for biogenic VOC increased from 1990 to 1999. I thi nk I understood from our conversation today that this change was due to a change in biogenic es timation models used, and if/when the same model is used consistently, the model shows a decre ase in VOC emissions. Is that right? Please feel free to point me to your past submittals to help me understand this further. Thanks so much! Have a great weekend,

anita

* * * * * * * * * * * * * * * * * * * * Anita Lee, PhD

Environmental Scientist US EPA, Region 9 Air Planning Office 75 Hawthorne Street (AIR-2) San Francisco, CA 94105

ph: (415) 972-3958 fax: (415) 947-3579

* * * * * * * * * * * * * * * * * * * * 

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