API Publ 4720-2002 pdf download.Comparison of API and EPA Toxic Air Pollutant Emission Factors for Combustion Sources.
Both the U.S. Environmental Protection Agency 1 (EPA) and the American Petroleum Institute 2 (API) have published toxic air pollutant emission factors for combustion sources. These emission factors are frequently used by industry to prepare emission inventories to satisfy regulatory reporting requirements. State and federal agencies also use them to identify emission reduction priorities. While there is some agreement between the two data sets, there are many inconsistencies between the two. In addition, many of the factors are based on very limited data sets or are missing altogether. This study compares and explains differences in published toxic air pollutant emission factors for combustion sources and recommends priorities for gathering additional emission factor information. The specific objectives of this project were: • To compare the emission factors published by EPA and API to identify gaps and inconsistencies. • To identify available emission test data that can potentially be used to verify published factors and fill in existing gaps. • To recommend additional field-testing or other efforts needed to fill in gaps or resolve inconsistencies. This report describes the efforts completed to meet these objectives. 2 COMPARISON OF PUBLISHED EMISSION FACTORS The two primary sources of published emission factors for air toxics from combustion processes are the EPA’s AP-42 document and the API’s Petroleum Air Toxics Emission Factors (PATEF) database. The EPA periodically updates emission factors to incorporate new available test data. The AP-42 emission factors for boilers and heaters were updated in 1998 to include information from the electric utility hazardous air pollutant study. In the summer of 2000, the EPA updated emission factors for gas turbines and gas-fired reciprocating engines based upon information compiled during the Industrial Combustion Coordinated Rulemaking (ICCR) efforts.
Detailed graphical summaries of gaps and inconsistencies for each source category and pollutant are presented in Appendix B. Figure 1 summarizes the information in Appendix B by assigning a single color code for each source and pollutant category. Major gaps in air toxic emission factors for combustion sources include: • A lack of data for dioxin/furan emissions for most source categories. This gap may be important because EPA’s Per- sistent Bioaccumulative Toxic regulation is focusing attention on these chemicals. The reporting threshold for the dioxin and dioxin-like compounds is 0.1 grams per year. While the relative potential for dioxin emissions from gas- fired heaters is generally considered very low, the industry needs a reasonable and defensible position regarding their potential to emit dioxin. • A lack of data for metals emissions for reciprocating internal combustion engines (RICE) and gas-fired gas turbines. While it is likely that metal emissions from these sources are small, there are no published emission factors to con- firm this assumption. • No consistent list of target compounds used in the emission testing. Not all HAPs were tested for in all tests. For example, newer testing of reciprocating engines using Fourier Transform Infrared (FTIR) techniques included many more individual organic HAP compounds than older testing, which tended to focus on aldehydes, benzene, toluene, and xylene. Thus, there is a lack of data for certain organic HAP emissions from certain source categories such as gas- fired and fuel oil-fired boilers and heaters. Similarly, not all metals or polycyclic compounds were tested for in all tests. This results in isolated gaps for specific organic HAPs, polycyclic compounds, and metals throughout the database. There are several inconsistencies in the reported emission factors. For example, several metal EPA emission factors for gas- fired boilers/heaters are 10-50 times lower than the API emission factor.