Combustion Webinar 

June 9, 2010 

Frequently Asked Questions 

Are boilers located at electric utilities covered by the proposed boiler rules? 

This will depend on the characteristics of each boiler. 

 A boiler will be covered by the utility MACT if it meets the definition of an “electric 

utility steam generating unit” (EGU) contained in section 112(a)(8). 

 A boiler is not an EGU if it does not meet the definition of an EGU contained in section 

112(a)(8) (i.e., combustion unit of equal to or less than 25 MW or do not produce 

electricity for sale). This boiler will be covered under the boiler MACT or boiler area 

source rule. 

 A boiler that does not burn any coal or oil, regardless of size, will be covered under the 

boiler MACT or boiler area source rule. 

 We have not made a determination on combustion units of more than 25 MW that co-fire 

coal and/or oil with biomass (or anything else that isn't classed as a "solid waste"), in 

whatever respective quantities. This determination will be made as the Utility MACT 

rulemaking package is developed and reviewed. 

How are natural gas-fired units regulated? 

In the proposed major source boiler rule, new and existing natural gas-fired boilers are regulated 

with a work practice standard requiring that an annual tune-up be conducted for units equal to or 

greater than 10 MMBtu/hr and a biennial tune-up for units less than 10 MMBtu/hr. 

Natural gas-fired boilers are not regulated by the proposed area source boiler rule. 

How is the initial fuel category of a unit established? 

In the proposed major and area source boiler rules, the definitions of the coal, biomass, and oil 

subcategories establish the initial fuel subcategory under which each boiler would be regulated. 

Can a unit be switched to another fuel category or will it always have to meet those limits? 

The proposed boiler major source rule covers major source boilers and process heaters that do 

not burn solid waste material. Similarly, the proposed boiler area source rule covers area source 

boilers that do not burn solid waste material. A major source boiler or process heater, or an area 

source boiler, would no longer be covered by these rules if it began burning solid waste. Instead, 

that unit would be covered by rules for solid waste incinerators. 

In the proposed boiler major source rule, we are requesting comment on whether the owner of a 

boiler or process heater which has been burning solid waste should be able to choose coverage 

by the boiler rule (instead of the waste incinerator rules) if the owner agrees to an enforceable 

restriction that the unit will not burn solid waste in the future. 
What is a traditional fuel? 

Traditional fuels are fuels that have been historically managed as valuable fuel products rather 

than being managed as waste materials. Examples include fossil fuels (e.g., coal, oil, including 

used-oil meeting on-specification levels, natural gas), and their derivatives (e.g., petroleum coke, 

bituminous coke, coal tar oil, refinery gas, synthetic fuel, heavy recycle, asphalts, blast furnace 

gas, recovered gaseous butane, coke oven gas), as well as clean cellulosic biomass (e.g., green 

wood, forest thinnings, sawdust, bagasse, peanut shells, etc.). Traditional fuels are unused 

products that have not been discarded and therefore are not solid wastes. We are requesting 

comment in the proposed rule on whether there are other traditional fuels that we have not 

identified. 

What are some examples of ingredients burned for energy recovery that would not be 

considered solid waste? 

An ingredient in a manufacturing process (whether by the generator or a third party) that meets 

the legitimacy criteria (i.e., be managed as a valuable commodity, provide a useful contribution, 

be used to make a valuable product, and contain contaminants that are comparable or lower than 

in traditional products), would not be considered a solid waste. Examples include materials such 

as cement kiln dust, coal ash, and foundry sand that are used as ingredients in manufacturing 

processes (e.g., in cement kilns), so long as they satisfy the legitimacy criteria. For more 

information, please see the Flow Chart for Determining Whether Non-Hazardous Materials Used 

as Fuel In Combustion Units are Solid Waste 

<http://www.epa.gov/epawaste/nonhaz/define/flow-fuel.htm> 

and 

Flow Chart for Determining Whether Non-Hazardous Secondary Material Ingredients Burned In 

Combustion Units are Solid Waste

<http://www.epa.gov/epawaste/nonhaz/define/flow-ingredient.htm> 

Which rule would apply to units that burn mostly traditional fuels but also some solid 

waste? 

A unit that burns mostly traditional fuels but also some solid waste would be subject to the 

Combustion and Solid Waste Incinerator (CISWI) rule. By definition, a CISWI unit is any 

distinct operating unit of any commercial or industrial facility that combusts any solid waste 

pursuant to Subtitle D of Resource Conservation and Recovery Act (RCRA).
Does the CISWI, Boiler Major Source Rule, or Boiler Area Source Rule apply to units that 

burn coal and clean biomass? 

Depending on the major source status of the facility, the boiler major source rule or boiler area 

source rule would apply to boilers burning coal and pure biomass. 

What is meant by "contaminated" construction & demolition debris? 

By “contaminated,” EPA means the material contains contaminants at levels that are not 

comparable or lower in concentration than traditional fuels. The proposal defines 

“contaminants” as all hazardous air pollutants (HAPs) listed under CAA section 112(b), as well 

as the nine pollutants required to be regulated under CAA section 129. An example of 

contaminated construction and demolition material is wood painted with lead-based paint that 

has not been sufficiently processed to produce a legitimate product (by removing the lead-based 

paint). 

How are qualifying cogeneration facilities and qualifying small power producers that 

combust a homogeneous waste stream covered under these rules? 

The CISWI Rule contains an exemption for qualifying small power producers, qualifying 

cogeneration units and metals recovery units pursuant to Section 129(g)(1) of the Clean Air Act. 

If a unit otherwise fits the definition of a major source boiler or process heater or an area source 

boiler, it would be subject to either the major source boiler or area source boiler rule. 

What rules/testing is required for boilers under 10 MMBtu/hr? 

In the proposed area source boiler rule, new boilers under 10 MMBtu/hr are subject to emission 

limits. New coal-fired boilers are subject to mercury (Hg), carbon monoxide (CO), and 

particulate matter (PM) limits, and new biomass-fired boilers and oil-fired boilers are subject to 

CO and PM limits. Initial and annual emissions testing are required for all boilers subject to 

emission limits. 

In the proposed major source boiler rule, new boilers, except for units in the “Gas 1” 

subcategory, under 10 MMBtu/hr are subject to emission limits for Hg, CO, PM, dioxin, and 

HCl. Initial and annual emissions testing are required for all boilers subject to emission limits. 

When do these rules take effect? 

Existing affected boilers must achieve compliance with the applicable provisions in 40 CFR 

63.7485 of subpart DDDDD (National Emission Standards for Hazardous Air Pollutants 

(NESHAP) for Industrial, Commercial, and Institution Boilers and Process Heaters) for major 

source boilers, and in 40 CFR 63.11193 of subpart JJJJJJ (National Emission Standards for 

Hazardous Air Pollutants for Industrial, Commercial, and Institutional Boilers Area Sources) for 

area source boilers, no later than 3 years after publication of the final rule. New affected boilers 

that start up on or before the publication of the final rule must achieve compliance no later than 

the date of publication of the final rule. New affected boilers that start up after publication of the 

final rule must achieve compliance upon startup. 
For the CISWI Rule, the NSPS for new incineration units become effective six months after 

promulgation (i.e., December 16, 2010). The EG for existing incineration units become effective 

no later than three years after EPA approves a state plan implementing the EG or five years after 

the date they are promulgated, whichever is earlier. 

Are "new" units identified by the proposed rule determined by publication date or by the 

publication date of the final rule? 

New boilers and CISWI units are determined based on the date of publication of the proposed 

rule (i.e., June 4, 2010). 

Where can I find the presentation materials from the June 9, 2010 webinar? 

The webinar and presentation materials are available at 

http://www.epa.gov/apti/broadcast.html#boilers060910