ENVIRONMENTAL ANALYSIS: Emission Inventories
Have you completed an air emission survey for your operations? Most States are now requiring air emission surveys for nearly all manufacturing operations. The purpose of the air emission survey is to require manufacturing facilities to self-disclose actual and potential air emissions emanating from their operations.
The emission inventory is the foundation of EPA's air pollution regulatory program because it assists EPA in answering questions such as, what is the current stage of pollution in a specific area? Which facilities are the biggest emitters of pollution? What types of emissions are currently controlled and how well are they controlled? etc. The EPA uses this data to proceed to better control sources through regulation. Additionally, the inventory allows the EPA to test a particular rule's effectiveness and extrapolate emissions into the future.
Refractory Air Emission Survey
There are significant challenges to completing an air emission survey for a refractory operation. The challenge lies not only in the number of pollutants to be concerned with, but also the credibility of the emission calculations that are available to estimate actual and potential emissions.
It is obvious to most that the primary pollutant of concern in refractory manufacturing is particulate matter. Particulate matter emissions occur during the crushing, grinding, screening, calcining and drying of the raw materials; the drying of the unfired "green" refractory bricks, tar and pitch operations; and finishing of the refractories (grinding, milling and sandblasting). These emissions are readily identifiable and therefore have been managed using pollution control technologies such as fabric filters (baghouses), wet scrubbers and cyclones.
However, there exists an entire list of not-so-easily identifiable pollutants associated with refractories, particularly in the calcining and kilning processes. These pollutants include sulfur dioxides, nitrogen oxides, carbon monoxide, carbon dioxide and volatile organic compounds. Additional pollutants of concern include chromium and fluoride emissions from the raw materials, and recently, the EPA has been concerned with dioxins and other manmade pollutants that may be present in the raw materials. Nearly all of these types of pollutants have been linked to extremely hot topics, such as global warming, childhood asthma, acid deposition and aesthetic degradation.
In addition to the expansive list of pollutants to be concerned with from refractories, it has become exceedingly important for refractories to accurately calculate and estimate emissions.
One of the more common methods of estimating emissions involves the use of EPA documented emission factors. The benefits of utilizing these types of emission factors are two-fold. First, the EPA will often accept the factors, if applied properly when calculating product throughput, because they are conservative estimates. Secondly, the use of emission factors is a relatively inexpensive way of estimating emissions.
The disadvantage lies in the accuracy of the emission factor. In many cases, the EPA emission factors result in a company overestimating emission releases. When comparing emission factors to a more sophisticated method of analysis such as source (stack) testing, it is not uncommon for the EPA emission factor to be as much as 20-50 percent too high. This level of error can be significant because the emission estimate is applied in a variety of reports including EPA permit-required record keeping and emission fee reporting, Toxic Release Inventories and calculations to determine permit status and compliance.
The best approach to use in estimating emissions is to conduct site-specific source testing; however, in many operations this can be a challenge. For example, difficulties arise when attempting to quantify a representative pollutant laden stream from a crushing operation due to the characteristics of the operation. Furthermore, it can be difficult to determine total gaseous emission losses from a kiln due to the nature of the pollutant make-up, not to mention accounting for furnace leaks and other inefficiencies.
Things to Remember
When completing an emission survey, some very basic concepts should be considered and weighed appropriately during the activity. First, documented emission factors are estimates and should be applied with caution. Your operation may outperform what an emission factor indicates. Secondly, make sure you account for both the capture and control efficiencies of your air handling systems and ensure these conditions are reflected in your air permits. Lastly, there are exemptions and rule specific methodologies for completing an air emission survey, therefore research the approved methods, exercise good judgment and document your approach.
For more information on emission factors for refractory operations: http://www.epa.gov/ttn/chief/ap42/ch11/final/c11s05.pdf