chapter 4 emissions inventory - imperial county … plans/sip meetings/04... · chapter 4 -...

Created on 6/06/2008

Chapter 4; of 14

CHAPTER 4

EMISSIONS INVENTORY

4.1 Introduction

4.2 Emission Source Classification System

4.3 2002 Baseline Inventory Categories

4.4 Comparison of Baseline Inventories

4.5 Emissions Inventory Forecast

4.6 Comparison of Baseline and Summer Emissions

Inventories


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CHAPTER 4 - EMISSIONS INVENTORY

4.1 - INTRODUCTION

Effective control strategies cannot be developed without an understanding of the type and number of emission sources contributing to the air quality problem. An emissions inventory is a comprehensive description of the sources of air pollution in a given region and a quantitative estimate of their emissions. These inventories are used to track emission levels over designated time periods, to aid the development and evaluation of emission reduction strategies, to provide data for air quality modeling, and to project emissions for future years. In cooperation with CARB, the District develops a complete emissions inventory every year for all sources in Imperial County. This chapter presents emissions that occurred in Imperial County during the base year 2002 and projected emissions in year 2009. The U.S. EPA designates the 2002 inventory as the baseline for measuring progress toward attainment. Thus, a significant effort has gone into making this inventory as complete and accurate as possible. Emissions inventories for future years will be compared to 2002 emission levels to determine progress in meeting emission reductions necessary to attain the 8-hour ozone NAAQS. Imperial County is required to demonstrate attainment with the 8-hour Ozone NAAQS no latter than June 15, 2010. Therefore, the 2009 emission inventory has been selected as the future emission inventory for attainment and modeling purposes. The emissions inventory contains estimates of emissions which occurred in a calendar year, and classifies those emissions into various source categories. The pollutants included in these categories are reactive organic compounds (ROG) and oxides of nitrogen (NOx), both precursors to ozone formation. Different inventories are prepared for regulatory and AQMP performance tracking: an annual average inventory and a summer planning inventory. The average annual emission inventory was derived primarily by dividing the annual total emission by 365, except for the emissions derived from CARB’s EMFAC2007 (on road sources) and OFFROAD (most off-road mobile sources) models. The 2002 average annual inventory was developed for ozone precursor pollutants only (Table 4-1). On the other hand, the Attainment Demonstration requires the use of a new type of inventory for attainment planning. This “planning inventory” is designed to more accurately represent emissions that occur during the summer ozone season (May through October), when violations of the standard are more likely to occur. The 2002 summer planning inventory reports emissions in units of tons per day and includes data for only the pollutants And only includes data for the pollutants ROG and NOx, the two precursors to ozone (Table 4-2). Any strategy designed to mitigate air pollution in the Imperial County must consider this seasonal variation in ambient air quality. This inventory is the key to the implementation of this Plan and forms the basis for the emissions reduction strategies presented in this plan.


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4.2 – EMISSION SOURCE CLASSIFICATION SYSTEM CARB has established a standardized system of emission source categories for the state. All sources are classified as either stationary or mobile. Stationary sources are further subdivided into point and area sources categorized depending on their permit status, relative size, and emission characteristics. Point sources, such as factories, geothermal plants, and rock quarries, are generally of a significant size and are required to have a District Permit to Operate. In contrast, area sources usually have emissions that fit a generalized category, and are either too numerous or too small to warrant individual attention; examples include architectural coatings, consumer products, residential fuel combustion and others. Most sources in this category are not required to obtain a District permit. Mobile sources include automobiles, airplanes, trains and others and are generally regulated at the state or federal level. Emissions calculations require the use of an appropriate emissions factor and some indication of activity level for each source or source category. For stationary point and area sources, emission factors can be based on either actual measurements obtained through source testing, or on engineering data derived from reference literature. The most common reference document for emission factors is EPA’s Compilation of Air Pollutant Emission Factors, AP-42. Activity indicators for large stationary point sources are generally based on source-specific data such as fuel usage, hours of operation or some other measured parameter. Area source and small point source activity indicators are usually estimated using standardized techniques. For instance, a common method for analyzing area sources, such as architectural coatings, is to apportion statewide usage data to different geographical areas based on regional population counts. A more refined approach would involve surveys of local suppliers or distributors of the coatings to obtain individual usage data specific to the County. Mobile sources consist of two subcategories: on-road and off-road sources. On-road vehicle emissions are calculated using socioeconomic data and transportation models provided by SCAG, spatial distribution data from Caltrans, and EMFAC2007 V2.3 inventories obtained from CARB. Emissions from off-road vehicle categories (e.g., trains, off-road equipment, and aircraft) were developed primarily based on estimated activity levels and emission factors. 4.3 – 2002 BASELINE INVENTORY CATEGORIES This section provides a brief description of the major emissions inventory categories. Sources are first grouped as to whether they are stationary or mobile. These are then differentiated by their type of activity, such as those that burn fuel or process petroleum. It is not uncommon to find different source types at the same facility. Thus, an individual company’s emission inventory may be divided among two or more source categories. The emissions inventory data for stationary and off-road mobile equipment was obtained


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from the California Emission Forecast System (CEFS), version 1.06. The on-road mobile source emission inventory data was obtained from CARB’s Planning and Support Division and was generated using EMFAC 2007 v2.3 and the vehicle population provided by SCAG in March 2008. Table 4-1 summarizes the 2002 average annual emissions inventory by major source category. A detailed breakdown of emissions per each source category is presented in Appendix 4. The 2002 average annual emissions inventory reflects adopted air regulations with current compliance date as of 2002. A list of Imperial County APCD and CARB rules and regulations that are part of the base year is presented in Chapter 5. Fuel Combustion: This category includes sources that burn fuels such as natural gas and diesel to do work or to produce useful heat. Combustion processes are a significant source of NOx emissions due to the oxidation of nitrogen in the fuel and in the combustion of air. Examples of sources in this category are electric utility boilers, process heaters, internal combustion engines, home furnaces, and orchard heaters. Emissions from this source category represent 7.44% of the NOx emissions and 0.36% of the ROG emissions in the 2002 annual average emissions inventory. Managed Burning and Disposal: The emission inventory data for this activity is reported in the Miscellaneous Processes source category. The burning of agricultural waste can generate considerable quantities of ROG, CO and PM10 due to incomplete combustion. The bulk of these emissions result from the open burning of wheat straw and Bermuda grass. Other sources in this category include residential burn barrels, open burning of agricultural and residential tree pruning, and range improvement burns. Waste burning generates approximately 2.3 tons per day or 6.91% of the ROG emissions in the annual average emissions inventory. Solvent Use: Organic solvents are used in a wide variety of industrial processes and are ingredients in numerous household and commercial products. The major concern here is that most solvents volatilize as ROG, which then becomes available to form ozone Example categories are dry cleaning, degreasing, asphalt paving, architectural coatings, and printing operations. These sources are responsible for approximately 20.68% of the ROG emissions in the annual average emissions inventory. Petroleum Production and Marketing: Emissions in this category result from the petroleum industry (petroleum pumping stations, truck loading and unloading.) Other activities include retail and commercial gasoline marketing and combustion related emissions that do not qualify for the Fuel Combustion category above. While most of the sources emit reactive organic compounds, the combustion-related facilities also produce the majority of the sulfur dioxide emissions in the County. This source category accounts for 1.96% of the ROG emissions in the 2002 annual average inventory. Industrial Processes: The sources and activities included here primarily emit PM10 and ROG. Examples are feed and grain mills, rock quarries, sand and gravel operations, and concrete batch plants. The ROG emissions from this group of sources represent


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approximately 0.21% of the ROG emissions in the 2002 annual average emissions inventory. Miscellaneous Processes: This category contains stationary source emissions which cannot be classified into those source groups already described. Included is the organic portion of both commercial and residential pesticide emissions. These sources combined are responsible for approximately 35.62% of the ROG in the annual average emissions inventory. On-Road Motor Vehicles: This category is divided into vehicle types ranging from motorcycles to heavy duty trucks. Motor vehicle emissions occur both from combustion of fuel in the engine and from evaporation of fuel in the gas tank. This category represents a major portion of the ROG and NOx emissions in Imperial County, contributing 55.60% of the NOx and 22.88% of the ROG in the 2002 annual average emissions inventory. Off-Road Mobile Sources: Included here are moving sources of air pollution that do not use paved roads. Examples are trains, boats, aircraft, off-road recreational vehicles, farm vehicles, and construction equipment. Some sources such as motorcycles can travel both on and off the road, but only emissions resulting from the latter activity are in this section. Emissions from these source types represent 34.15% of the NOx and 16.98% of the ROG in the annual average emissions inventory. The 2002 annual average emissions inventory is summarized in Tables 4-1 and graphically displayed in Figures 4-1 and 4-2.

Table 4-1 Emissions By Major Source Category: 2002 Base Year

Annual Average Emissions Inventory (tons/day) Source Category ROG %

Total NOx %

Total Stationary Sources

Fuel Combustion 0.120 0.36 2.614 7.44Waste Disposal 0.016 0.05 0.000 0.00Cleaning and Surface Coatings 0.418 1.26 0.000 0.00Petroleum Prod. and Marketing 0.653 1.96 0.000 0.00Industrial Processes 0.070 0.21 0.035 0.10

Total Stationary Sources 1.277 3.84 2.649 7.54Area-wide Sources

Solvent Evaporation 6.877 20.68 0.000 0.00Miscellaneous Processes 11.848 35.62 0.952 2.71

Total Area-Wide Sources 18.725 56.30 0.952 2.71Mobile Sources

On-Road Vehicles 7.612 22.88 19.535 55.60


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Off-Road Vehicles 5.648 16.98 12.002 34.15Total Mobile Sources 13.260 39.86 31.537 89.75 Total for Imperial 33.262 100.00 35.137 100.00

Figure 4-1 Emissions By Major Source Category: 2002 Base Year - Reactive Organic Gases -

Stationary Sources4%

Area Wide Sources56%

Off-Road Vehicles17%

On-Road Vehicles23%

Figure 4-2 Emissions By Major Source Category: 2002 Base Year - Nitrogen Oxides

Stationary Sources8%

Area-Wide Sources3%

On-Road Vehicles55%

Off-Road Vehicles34%


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4.4 – COMPARISON OF BASELINE INVENTORIES The 2002 summer planning emissions inventory was derived from much of the same data used in the development of the annual average emissions inventory. However, the summer planning emissions inventory differs from the annual average emissions inventory in four significant areas:

1. The temporal information used to determine seasonal planning inventories is also used to develop month/day-specific modeling inventories, it is just further resolved for modeling inventories. It should be noted that modeling inventories generated by CEFS are not actual day specific emissions based on field studies, they are estimates of emissions for “typical” operating conditions. The summer planning emissions inventory focuses on only NOx and ROG, because they are the primary precursors to ozone.

2. Point source emissions in the summer planning inventory are calculated based on

an ‘average annual operating day’, which discounts periods of non-operation such as weekends. The annual average emissions inventory totals emissions over the entire year and presents them in units of tons per year. Daily emissions are derived by dividing this total by 365 days, representing an ‘average annual day’ emission rate.

3. Area source emissions in the summer planning emissions inventory are calculated

using an ‘average seasonal operating day’. Monthly and weekly operating profiles for each area source category are used to apportion the annual emissions into the ozone and non-ozone seasons of the year. CARB has designated the months of May through October as the ozone season for the purpose of this calculation. The ‘average seasonal day’ is simply the total emissions for the ozone season divided by the number of days during the season. Again, the annual inventory uses the ‘average annual day’ calculation method for this source category.

4. The summer planning emissions inventory calculates on-road motor vehicles

emissions using a typical ‘episode day’. This method accounts for the higher temperatures and the resulting increased evaporative emissions that occur on hot summer days when elevated ozone levels are most likely. The annual inventory again uses the ‘average annual day’ method for this source category.

One aspect of the summer planning inventory that is not readily apparent is that emissions from natural sources have been excluded by CARB. Natural sources include wildfires, petroleum seeps, and biogenic emissions (organic compounds emitted from trees and plants). This is done because emissions resulting from natural sources are significantly beyond the District’s control. Thus, ozone violations that might occur as a result of emissions from natural sources are also not included in CARB’s determinations of nonattainment.


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The 2002 summer planning emissions inventory is summarized in Table 4-2. A detailed breakdown of emissions per each source category is presented in Appendix 4, Table 4-2. An examination of this table provides the following information.

1. Total emissions of ROG countywide were calculated at 37.300 tons per day for the

2002 summer planning emissions inventory. Table 4-2 shows that over 23% of the daily ROG emissions are attributable to on-road vehicles, primarily automobiles. Other mobile sources, such as off-road vehicles, trains, and aircraft contribute another 17% of these emissions. Area sources such as: solvent use (emissions from pesticides application), petroleum related activities, and farming operations (emissions from feedlots and dairies) constitute most of the remaining ROG emissions with approximately 55.82% .

2. The total NOx emissions countywide were estimated to be 42.347 tons per day. As

shown in Table 4-2, sources in the on-road vehicles category were the largest contributor, with about 54% of the daily NOx emissions in the summer of 2002. Other mobile categories were again a significant component with about 33% of daily NOx emissions.

3. Pesticide application is a large stationary source of ROG emissions. In the summer

of 2002 it emitted 5.4 tons per day with approximately 31% of the total ROG inventory.

4. The largest source of NOx emissions for both the summer planning and annual

inventories were mobile sources, which emitted approximately 32 tons per day in 2002 or approximately 88% of the total NOx emissions.

It is important to note that emissions for some source categories can be highly variable from year to year; other sources may generate emissions at a relatively stable rate over an extended period. Considered as a whole, however, the effect of these fluctuations by individual facilitate or source groups is largely muted by the substantial number and diversity of sources, and by the volume of emissions generated each year. Thus, the 2002 emissions inventory is likely representative of average emissions that might occur in any other given year, discounting the obvious effects of population growth and regulatory controls. The use of 2002 as the baseline emissions year is therefore appropriate for planning purposes.

Table 4-2 Emissions By Major Source Category: 2002 Summer Planning Emissions Inventory

(tons/day) Source Category ROG %

TOTAL NOx %

TOTALStationary Sources Fuel Combustion 0.121 0.32 3.570 9.54Waste Disposal 0.016 0.04 0.000 0.00


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Cleaning and Surface Coatings 0.417 1.12 0.000 0.00Petroleum Prod. and Marketing 0.653 1.75 0.000 0.00Industrial Processes 0.071 0.19 0.035 0.09Total Stationary Source 1.279 3.43 3.606 9.63Area-Wide Sources Solvent Evaporation 9.008 24.15 0.000 0.00Miscellaneous Processes 11.814 31.67 0.917 2.45Total Area-Wide Sources 20.822 55.82 0.917 2.45Mobile Sources On-Road Vehicles 8.755 23.47 20.267 54.14Off-Road Vehicles 6.444 17.28 12.644 33.78Total Mobile Sources 15.2 40.75 32.911 87.92 Total for Imperial 37.300 100.00 37.433 100.00

4.5– EMISSION INVENTORY FORECAST This section summarizes the ROG and NOx emissions inventory for 2009. The 2009 average annual and summer planning emissions inventories were developed from the 2002 Base Year Inventory, applying the CEFS growth factors and the emission reductions described in Chapter 5. According to CAA, Imperial County is required to demonstrate attainment with the 8-hour Ozone NAAQS no latter than June 15, 2010. Therefore, the 2009 emission inventory has been selected as the future emission inventory for attainment and modeling purposes. Resulting emission projections for 2009 average annual and summer planning emissions inventories are summarized in Table 4-3 and Table 4-4, respectively. A detailed breakdown of emissions per each source category is presented in Appendix 4, Table 4-3 and Table 4-4. Both ROG and NOx emissions are predicted to decrease dramatically in Imperial County from 2002 to 2009 due to State and District programs, as discussed in Chapter 5. The emission reductions discussed in this section, and depicted in Table 4-4 and Table 4-5, result from the control strategies relied upon to comply with RFP and modeled attainment requirements. Several other programs are in place, or are being pursued, that would provide additional emissions reductions increase the probability of achievement in the 2009 timeframe. The emission inventory data depicted in this document was obtained from the California Emission Forecast System (CEFS), Version 1.06, and CARB’s Planning and Support Division. Future Year Emissions for stationary and off-road mobile equipment for all areas throughout the state are maintained by CEFS, which is a computer model that utilizes pollutant-specific algorithms. The on-road mobile source data was evaluated by the Planning and Support Division using EMFAC 2007 v2.3 and updated vehicle population information provided by SCAG, as of March 2008. ROG and NOx emissions for a summer day that pertain to Imperial County for the year


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2009 were generated using an emission forecast model. The method of forecasting emissions applies growth and control factors to the 2002 base year emissions to estimate future emissions. The calculation of future emissions inventory data, using growth and control factors, is determined by analyzing the actual emissions for 2002, future socioeconomic assumptions, and the future impact of state and federal control strategies. CARB’s CEFS emissions forecast model formula is as follows: FYt = BY*GFt*CFt Where: FYt = controlled planning day emissions for the forecast year (t) BY = base year (2002) planning day emissions per process GFt = growth factor for forecast year (t) CFt = control factor for forecast year (t) With the data provided by the districts, CARB maintains statewide CEFS models and is able to compute growth factors. Growth Factors account for modifications in future year socioeconomic conditions relative to the 2002 base year inventory using activity indicators. Activity indicators such as population, housing, and employment data are collected to track economic status, or social trends of the surrounding area. Once determined, CARB assigns activity indicators to emission categories. For rule development analysis, CARB updates the socioeconomic data that is utilized in CEFS periodically. Control Measures are evaluated by the District based on estimated control effectiveness, knowledge of local sources, and future control technologies. During the rule development process, Control Factors (CF) are modified as newer and more accurate information becomes available, it represents the estimated effectiveness of each control measure to mitigate emissions. A control factor is a combination of the following four elements:

1. technological control efficiency (CE) of the control technology, equipment or strategy requirements of the control measure;

2. compliance efficiency, or rule effectiveness (RE) of the control measure, reflecting the actual “real world” ability of a control measure to achieve expected emission reductions;

3. rule penetration (RP), or impact factor, representing the relative amount of emissions in a source category subject to a control measure, Taking into consideration any exemptions and other control measures; and,

4. implementation factor (IP), or relative amount of total control taking place in a given year, for control measures having phased implementation or control requirements taking place in tiers.

Control factors are used to quantify the remaining uncontrolled emissions in a source


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category after control is applied. Control Factors are represented by the following equation: CF = 1 – (CE*RE*RP*IP) Control Factors are specific to an emission source and are relative to the control levels for the base year 2002 and reveals future year’s projected emission controls. Most recent reports of emission estimates for mobile sources are included by CEFS with support of the EMFAC model for on-road vehicles and Off-road vehicle models. With cooperation amongst transportation agencies, local planning agencies, CARB, and SCAG, growth assumptions for mobile sources categories are determined. Table 4.5 shows important motor vehicle growth indicators from CARB EMFAC 2007v2.3 on-road mobile model and SCAG 2008 RTP.

Table 4-3 Motor Vehicle Growth Trends

Imperial County Totals

Indicators 2002 2009

All vehicle categories Vehicles 121,707 161,231Vehicle miles traveled (x1000)

VMT/1000 4,780 6,277

All vehicle trips Trips 808,700 1,054,090Gasoline 217.44 285.15Fuel Consumption (1000

gallons) Diesel 97.07 115.09Notes: EMFAC2007v2.3; Nov 1, 2006 Run Date: 03/18/2008 Season Summer

CARB’s Planning and Technical Support Division has the primary responsibility for developing on-road and off-road mobile source emissions inventories in the state. CARB mobile source mathematical models, EMFAC and OFFROAD, produce future year inventories by geographic area for all pollutants. The 2009 annual average emissions inventory is summarized in Table 4-4.

Table 4-4 Emissions By Major Source Category: 2009 Annual Average Day Inventory (tons/day)

Source Category ROG %

Total NOx %

Total Stationary Sources

Fuel Combustion 0.122 0.43 2.541 8.50


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Waste Disposal 0.020 0.07 0.000 0.00Cleaning and Surface Coatings 0.417 1.47 0.000 0.00Petroleum Pro. and Marketing 0.720 2.53 0.000 0.00Industrial Processes 0.071 0.24 0.039 0.13

Total Stationary Sources 1.350 4.75 2.580 8.63Area-wide Sources

Solvent Evaporation 6.738 23.70 0.000 0.00Miscellaneous Processes 8.076 28.41 0.919 3.07

Total Area-Wide Sources 14.814 52.11 0.919 3.07Mobile Sources On-Road Vehicles 5.704 20.06 16.801 56.22Off-Road Vehicles 6.562 23.08 9.587 32.08Total Mobile Sources 12.266 43.14 26.388 88.30 Total for Imperial 28.430 100.00 29.887 100.00

The 2009 summer planning emissions inventory is summarized in Table 4-5. An examination of this table provides the following information.

1. Total emissions of ROG for Imperial County were calculated at 32.383 tons per

day for the 2009 summer planning emissions inventory. Table 4-5 shows that over 20% of daily ROG emissions are attributable to on-road vehicles, primarily automobiles. Other mobile sources, such as off-road vehicles, trains, and aircraft contribute another 23% of these emissions. Area sources such as: solvent use (emissions from pesticides application), petroleum related activities, and farming operations (emissions from feedlots and dairies) constitute most of the remaining ROG emissions with approximately 51.8%.

2. The total NOx emissions in summer 2009 were estimated to be 31.931 tons per

day. As shown in Table 4-5, sources in the on-road vehicles category were the largest contributor, with about 55% of the daily NOx emissions. Other mobile categories were again a significant component with about 32% of daily NOx emissions.

3. Despite a significant reduction from the 2002 inventory, pesticide application is

still a large stationary source of ROG emissions. In the summer of 2009 it will emit 4.9 tons per day of ROG.

4. The largest source of NOx emissions for both the summer planning and annual

inventories were mobile sources, which will emit approximately 27.5 tons per day or approximately 86% of the total NOx emissions in 2009.


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Table 4-5

Emissions By Major Source Category: 2009 Summer Planning Inventory (tons/day)

Source Category ROG % TOTAL

NOX % TOTAL

Stationary Sources Fuel Combustion 0.123 0.38 3.437 10.76Waste Disposal 0.020 0.06 0.000 0.00Cleaning and Surface Coatings 0.417 1.29 0.000 0.00Petroleum Prod. and Marketing 0.720 2.22 0.000 0.00Industrial Processes 0.072 0.22 0.040 0.13Total Stationary Sources 1.352 4.18 3.477 10.89Area-wide Sources Solvent Evaporation 8.735 26.97 0.000 0.00Miscellaneous Processes 8.043 24.84 0.886 2.77Total Area-Wide Sources 16.778 51.81 0.886 2.77Mobile Sources On-Road Motor Vehicles 6.779 20.93 17.410 54.52Off-Road Vehicles 7.474 23.08 10.158 31.81Total Mobile Sources 14.253 44.01 27.568 86.34 Total for Imperial 32.383 100.00 31.931 100.00

4.6 – COMPARISON OF BASELINE AND SUMMER EMISSIONS INVENTORIES A comparison of 2002 and 2009 ROG and NOx summer planning inventories is summarized in Table 4-6 and graphically displayed in Figures 4-3 and 4-4. Significant reductions in ROG and NOx summer planning emissions are shown in Table 4-6. ROG summer planning emissions should decrease by 4.5 tons per day, 12.1% in 2009 compared to the 2002 base year. In addition, NOx summer planning emission should decrease by 5 tons per day, 11.8% for the same year period.

Table 4-6 Imperial County Summer Planning Emissions Inventory Comparison

ROG Tons per Day Reductions

2002-2009 2002 2009 Tons

per day Percent

Stationary 1.279 1.352Area-Wide 20.822 16.778


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On-Road Mobile 8.755 6.779Off-Road Mobile 6.444 7.474Total ROG 37.300 32.383

4.917

13.18

NOx Tons per Day Reductions

2002-2009 2002 2009 Tons

per day Percent

Stationary 3.606 3.477Area-Wide 0.917 0.886On-Road Mobile 20.267 17.410Off-Road Mobile 12.644 10.158Total NOx 37.433 31.931

5.502

14.70

Figure 4-3 ROG 2002-2009 Summer Planning Emissions Inventories

20.8

8.8 6.4

37.3

1.35

16.8

6.8 7.5

32.4

1.280

10203040

Stationary Area-Wide On-Road Off-Road Total

Tons

/day

2002 2009 Column 3

Figure 4-4 NOx 2002-2009 Summer Planning Emissions Inventories

3.6 0.91

20.312.6

37.4

3.5 0.88

17.410.2

31.9

010203040

Stationary Area-Wide On-Road Off-Road Total

Tons

/day

2002 2009

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