At a conference a few weeks ago, the question was asked: “what is BACT for GHG”? The answer is…”it depends”. As detailed in previous posts on this website, and highlighted several times throughout the EPA BACT GHG Guidance, it is important to remember that BACT for any pollutant is determined on a case-by-case basis via a BACT Analysis, including BACT for GHG. That being said, the EPA has provided white papers that outline GHG control measures for several industrial sectors. These include:

• Electric Generating Units
• Large Inustrial/Commercial/Institutional Boilers
• Pulp and Paper
• Cement
• Iron and Steel Industry
• Refineries
• Nitric Acid Plants

The control measures discussed in these documents include energy efficiency, alternative fuel considerations, and carbon capture and sequestration.

If you have any questions regarding BACT and GHG, or permitting of GHG under the CAA, feel free to send me an e-mail at BMogan@Geosyntec.com.

In general, the BACT Cost Analysis for each control device must include:

• Total Capital Investment (TCI)
• Indirect Annual Cost
• Direct Annual Cost

The Total Annualized Cost (in current dollars) is divided by the amount of pollutant removed (in tons/year). This value is known as the “Cost Effectiveness” value and for the purposes of a BACT Analysis; it is used to determine whether a control scenario is economically feasible or infeasible. For economic reasons, it is important that your BACT Cost Analysis takes into account ALL of the costs associated with the installation and use of the control scenarios in question. There are a few resources available for estimating these costs (EPA software, vendor quotes, etc.). However, none of these resources should be considered completely accurate.

For common control devices, the EPA’s Air Compliance Advisor (ACA) software can be used to estimate these costs. However, the equations that are used to generate these estimates are valid only for certain operational ranges, do not consider site specific aspects for installing and operating the control technologies, and may provide unacceptably low cost effectiveness values. For some BACT Analysis projects, relying on the ACA software may mean that a BACT is selected that is not, in fact, the best available control technology (taking into account energy, environmental, and economic impacts). This could potentially cost the facility hundreds of thousands, if not millions, of dollars in unwarranted control device requirements.

In order to accurately estimate the cost of each control device to be considered in your BACT Cost Analysis, it is important to understand each line item:

• TCI = Indirect Capital Costs + Direct Capital Costs + Contingency Costs + Inventory Capital
  • Indirect Capital Costs (installation and erection)
    • General Facilities Costs
    • Engineering and Office Costs
    • Process Contingency Costs
  • Direct Capital Costs
    • Cost of purchased equipment
• Indirect Annual Costs
  • Capital Recovery Costs
  • Property Taxes
  • Insurance
  • Administrative Charges
  • Overhead
• Direct Annual Costs
  • Fuel
  • Reagent (as required)
  • Electricity
  • Water
  • Maintenance
  • Labor
  • Parts Replacement (e.g., catalyst replacement)

Understanding the equations and parameters used to perform the BACT Cost Analysis is very important, especially if you are relying on the EPA’s ACA software. Here are some examples of how minor changes to the equations and parameters used in the BACT Cost Analysis can affect the result of your Economic Impact Study:

Example 1
A BACT Cost Analysis found the Cost Effectiveness value for a SCR used to control NOx emissions from a wood-fired boiler to be $14,175/ton NOx removed. However, this value was calculated assuming an interest rate of 7%, when a more realistic interest rate may have been 10%, bringing the Cost Effectiveness value to $16,871/ton NOx removed.

Example 2
Within certain operational ranges, a high-temperature catalyst (catalytic oxidation) can be used to control CO emissions from a fuel burning source, which has a purchase price of approximately $300,000 (actual vendor quote form BACT Analysis project). Upon further investigation, it is determined that the exhaust temperature is lower than required for the efficient destruction of CO in a high-temperature catalyst. As such, a catalyst containing precious metals must be used to allow reactions at lower temperatures. This low-temperature catalyst costs $600,000, bringing the Cost Effectiveness value from $12,497/ton CO removed to $13,426/ton CO removed.

Things to remember:

• Many control device cost estimation resources provide cost values in historical dollars. These values need to be updated, using an inflation factor, to reflect current dollar amounts.
• Vendors are a good source for direct capital costs (i.e., equipment costs). However, vendors know what a BACT Analysis is and may attempt to give you a “conservative” (low) estimate in hopes that their product is chosen as BACT. Furthermore, unless they have performed a site inspection, they can’t account for site specific factors, which may alter the cost provided in their quote. Finally, if you do use a vendor as a source for your cost estimate, be prepared to wait weeks (or sometimes even months) for them to get back to you with a quote.
• Each regulatory agency has a different opinion about the maximum economically feasible cost effectiveness value, and many (e.g., CTDEP) will not tell you what that value is. Just because you or your client believe that the control device is economically burdensome does not mean that the permit reviewer will agree. As such, it is always safer to make sure that your BACT Cost Analysis is as accurate, and site specific, as possible.

If you have any questions concerning, or would like assistance completing, a BACT Cost Analysis or any other portion of your project, feel free to contact me at any time.

SCR systems require a minimum temperature of approximately 575°F for the destruction of NOx. For applications where the process or equipment burns biomass fuels, a particulate control device is usually needed upstream of the SCR for it to function properly. However, by the time the flue gases pass through the particulate control device their temperature range is much less than required (between 57 and 61 percent) for the SCR to operate effectively. The traditional solution would be to install a natural-gas or oil fired burner between the SCR and particulate control device to re-heat the air to the appropriate temperatures. The economic burden of the capital costs associated with this control scenario, as well as the cost of the fuel required to operate the burners, is not cost effective given the amount of NOx removed.

As a solution, Babcock Power teamed with Pro-Environmental, Inc. (PEI) to combine Babcock’s SCR expertise with PEI’s Regenerative Thermal Oxidation (RTO) technology, capable of achieving heat recovery efficiencies of greater than 95 percent, to produce the RSCR technology. In 2005, a RSCR system installed at a 50MW power plant fired by wood and construction/demolition waste achieved a NOx emission rate of 0.07-lb/mmBTU. This emission rate equates to an 86% reduction in NOx emissions from wood waste combustion (AP-42 Chapter 1.6, Table 1.6-2 “Dry wood-fired boilers”).

If you would like more information on RSCR techology, visit Babcock Power’s website.

If you would like help completing your BACT Analysis, or any portion thereof, feel free to contact me.

According to the 1990 EPA NSR Workshop Manual, in order to show that a control scenario is technically infeasible you must “clearly document and show, based on chemical, physical, and engineering principles, that technical difficulties would preclude the successful use of the control option on the emission unit under review”.

Here is an example:

Our client wanted to install a 6-MW Biomass Boiler to supply process heat for the greenhouses at their facility. Because of the potential emissions from the proposed emission unit, our client was required to perform a BACT Analysis for PM, PM10, NOx, and CO.

One of the control devices identified for the control of particulate matter (PM and PM10) from the boiler was a fabric filter, also known as a baghouse. Although baghouses are used to control particulate emissions from biomass boilers, they are typically installed on larger units at facilities which have full-time boiler staff (1). If left unmonitored, burning cinders, temperature excursions, and/or operating upsets could result in a fire (2). Our client did not have a full-time boiler staff and therefore using a baghouse to control particulates from the proposed boiler was deemed technically infeasible.

If you have questions regarding the technical feasibility of the control technologies that you have identified, feel free to contact Brandon Mogan at (803) 422-5251, or click here for more information.

(1) Resource Systems Group, Inc.
(2) Hog Fuel Boiler RACT Determination. Washington State Department of Ecology. Doc. No. 03-02-009