Abstract
The Houston-Galveston-Brazoria (HGB) area of Texas is a moderate nonattainment region for ozone, and has a history of severe summer ozone episodes. W. A. Parish power plant (WAP) located in the greater Houston area is the largest coal and natural gas based electricity generating unit (EGU) in Texas. Forest residue is an abundant renewable resource, and can be used to offset coal usage at EGUs. This study evaluates the impact of co-firing 5%, 10%, and 15% (energy-basis) of forest residue at WAP on the air quality of the HGB area. Photochemical modeling with Comprehensive Air Quality Model with Extensions (CAMx) was conducted to investigate the air quality at three air quality monitoring sites (C696, C53, C556) in the HGB area, under two source scenarios (all-sources, point + biogenic sources). Significant reduction of SO2 and O3 was observed for 10% and 15% co-firing ratios at monitoring station (C696) close to WAP. The maximum reduction of ozone observed for 15% co-firing is 4.7% and 6.3% for all-sources and point + biogenic sources scenarios respectively. The reduction in other criteria air pollutants is not significant at all locations. The overall results from this study indicate that biomass co-firing at WAP would not lead to a significant reduction in ozone concentrations in the region during periods of peak ozone.
Highlights
IntroductionThe photochemical reactions that lead to the formation of ozone occur predominantly during hot, sunny summer days with high humidity levels [5] [6]
The possible reasons for the insignificant effect due to biomass co-firing could be that W. A. Parish power plant (WAP) power plant is controlled for NOX emissions by using selective catalytic reduction (SCR), and 90% emissions reduction was already observed from 1997 to 2010 [9]
This study evaluated the air quality impact of biomass co-firing with coal at three monitoring sites (C696, C53, C556) in the HGB area with Comprehensive Air Quality Model with Extensions (CAMx) simulations for the month of June 2012
Summary
The photochemical reactions that lead to the formation of ozone occur predominantly during hot, sunny summer days with high humidity levels [5] [6]. Rapid O3 formation occurs when the anthropogenic VOC emissions from the Houston Ship Channel region combine with NOx emissions from EGUs and mobile sources in the HGB area [9] [14]. The Texas Air Quality Study II, on 19th September, 2006 tracked the plume from WAP and estimated the ozone production efficiency (OPE) as 4.4 at the plume age of 0.6 h, indicating that conditions are suitable for rapid O3 formation when emissions from WAP combine with VOC emissions from the ship channel region [14]
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