PHOTOCHEMICAL GRID MODELING SUPPORTING INTER-PRECURSOR TRADING FOR NONATTAINMENT NEW SOURCE REVIEW

Transcription

1 PHOTOCHEMICAL GRID MODELING SUPPORTING INTER-PRECURSOR TRADING FOR NONATTAINMENT NEW SOURCE REVIEW Presented by Qi Zhang Providence Engineering and Environmental Group LLC 1

2 AGENDA What is inter-precursor trading? Why inter-precursor trading is conducted? Why modeling for inter-precursor trading? How to conduct such a modeling analysis? How to analyze the model results? 2

3 PRECURSOR OF OZONE FORMATION Source: US EPA, 3

4 WHAT IS INTER-PRECURSOR TRADING? Nonattainment New Source Review Title 30 Texas Administrative Code (TAC) (a) and (a) allow the use of emission credits (EC) and discrete emission credits (DEC) of one ozone precursor (i.e., nitrogen oxides [NO x ] or volatile organic compounds [VOC]) to meet the requirements for the other ozone precursor. Ozone inter-precursor trading NO x credits for VOC emissions or, the other way around 4

5 WHY INTER-PRECURSOR TRADING? Average Price of Credits Weighted by Trade Volume* NO x VOC $114,766 $146, Only $132,985 $190, Only $81,470 $54,518** Notes: *Trades less than $1 per ton are excluded. Swaps are excluded or adjusted. **When excluding an outlier trade with $8,300 per ton at 54.2 tons, the average comes to $106,165. 5

6 WHY MODELING FOR INTER-PRECURSOR TRADING? To make sure that by retiring one precursor s emission reduction credits for another precursor s new emissions does not negatively affect air quality. inter-pollutant (IP) use of credits requires a photochemical modeling demonstration and the approval of both the Texas Commission on Environmental Quality (TCEQ) and the United States Environmental Protection Agency (EPA). Guidance on the IP Use of Credits for NNSR Offsets, TCEQ, January

7 HOW TO CONDUCT AN IPT MODEL? CAMx Comprehensive Air Quality Model with Extensions 3 Model Runs Attainment Baseline (AB) Credit Baseline (CB) Project Baseline (PB) Comparative Analysis 7

8 SETUP MODEL RUNS AB SIP Run AB = Duplicate SIP run Identical results? Close enough results?

9 SETUP MODEL RUNS AB Credit Sources CB AB Project Sources PB 9

10 HOW TO ANALYZE THE RESULTS? AB CB PB IP m IP e IP ratio 10

11 DEFINE GRID CELL-DAY You modeled 6 grid cells and modeled 3 days, how many grid cell-days are there total? It s a 4D time-space concept. Modeled Dates: Model Domain: Day 1 Day 2 Day 3 (1,1) (1,2) (1,3) (2,1) (2,2) (2,3) 11

12 OVERALL AIR QUALITY IP E AB CB PB IP m IP e IP ratio 12

13 OVERALL AIR QUALITY IP E Identify all grid cell-days that the model predicts an ozone concentration > 65 ppb (5 ppb less than the standard), denote as n. The ozone concentration of the grid cellday n is: OA n AB OC n CB OP n PB 13

14 QUICK ILLUSTRATION AB CASE Day 1 Day 2 Day 3 How many grid cell-days to be considered? 14

15 QUICK ILLUSTRATION PB CASE AB PB Day 1 Day 2 Day 3 Which grid cell-days to be considered? 15

16 OVERALL AIR QUALITY IP E Impact of the Credit Base : E C = σ N n=1 (OC n OA n ) Impact of the Project Base : E p = σ N n=1 (OP n OA n ) Overall effect of the inter-precursor trade: IP e = E c E p If IP e 0 16

17 MONITOR DESIGN VALUES IP M AB CB PB IP m IP e IP ratio 17

18 MONITOR DESIGN VALUES IP M For each monitor within the nonattainment area: DVC m Predicted CB Design Value DVP m Predicted PB Design Value Using EPA s MATS (Modeled Attainment Test Software) program, this is a calibration process, to calibrate modeled impacts with monitored concentration. 18

19 MONITOR DESIGN VALUES IP M Calibration concept: Predicted future monitor reading = Recorded reading (e.g. 50 ppb) x [Modeled future impact (e.g. 80 ppb)/modeled existing impact (e.g. 100 ppb)] = 40 ppb Monitor specific effect of the inter-precursor trade: IP m = DVC m DVP m If IP m 0 19

20 TRADING RATIO IP RATIO AB CB PB IP m IP e IP ratio 20

21 TRADING RATIO IP RATIO IP ratio = CB ei PB ei CB ei Credit to surrender, tpy PB ei Project emissions, tpy This ratio is fixed before the model run, instead of being determined after the model run. Minimum trading ratio? 21

22 QUESTIONS AND DISCUSSION THANK YOU! If you have any additional questions, please contact: Qi Zhang (281)