Volume 9, Number 2
A Gossman Consulting, Inc. Publication
April 2004

How the Proposed HWC MACT Regulation Pushes Waste to Incinerators and Away from Cement Kilns


David Constans, Gossman Consulting, Inc.


In Section VIII D of the Proposed Standards for Hazardous Air Pollutants of Hazardous Waste Combustors (Phase I Final Replacement Standards and Phase II) the EPA is proposing the new standards to limit emissions of semi-volatile metals (SVM).  Section VIII E then proposes the new standards to limit emissions of low-volatile metals (LVM).  See Federal Register for Tuesday, April 20, 2004, page 21248.

These two sections propose to limit SVM and LVM input rates tied to the heat content of the hazardous waste fuel. What impact will this rule change have on cement kilns?  The incinerators, solid fuel fired boilers and hydrochloric acid production furnaces do not have such a requirement.  Why not?

GCI has a waste fuel input calculator that will calculate the maximum allowable concentration of the SVM or LVM for existing and new facilities based on the heat content of the fuel and the facility’s system removal efficiency. The table illustrates the impact of the proposed regulation.

Assuming a SVM SRE of 99.0% and a LVM SRE of 99.9% the maximum allowable concentration of the metals in the HWF is shown in the following table.  Note how the allowable concentration decreases with heat content. 


Maximum Allowable Concentration in HWF, expressed as ppm by weight

Heat Content BTU/lb.
















Certainly, these SRE’s are lower than many of the kilns have established.  However, some kilns have not been rigorous in the establishment of SRE values and have relied on maximum metal input rates established during trial burns to set metal feed rate limits not SRE’s.  Remember the facility will have a total and liquid HWF feed rate limit as before. 

Metals concentrations do not generally decrease with decreasing heat content.  Waste minimization requirements cause generators to reduce volatile organic components in their wastes, which increase the solids concentrations in the waste and consequently the metals concentration in the waste.  It is not a hard and fast rule but certainly a concept well known and well understood by the industry and the EPA.  This is less of a problem for liquid wastes than for solid wastes.  The way this rule is written cement kilns that feed low heat content solids may have to restrict their generator base to ensure having the correct metal/heat content ratio in the fuel they burn.  If this is an important criterion in hazardous waste fuels emissions control why are incinerators and solid fuel boilers exempted from this requirement?

In the past, under BIF and the current HWF, if the waste fuel in the facility had a high concentration of a particular metals such that the facility could not feed at its maximum allowable rates it could feed at a lower rate.   Under the proposed rule, the facility will have to blend this high metal concentration fuel with other fuels to achieve the proper metals/heat content ratio.  The question that immediately comes to mind is, why?  This is not required of incinerators.  It is not an emissions control scheme that is superior to the current requirements.   There are already state permits issued based on the current control scheme in the HWC MACT requirements.  Will these permits be voided?  What about kilns that utilize non-hazardous wastes and substitute raw materials that have significant quantities of regulated metals?  How will the states and the EPA address those kiln’s permit requirements?

GCI sees three events resulting from EPA’s proposed changes in the regulation:

1.     Some wastes will be sent to incinerators instead of cement kilns, lightweight aggregate kilns or liquid fired boilers because the correct metals/heat content ratio can not be met economically and these devices will not be allowed to burn these wastes even at a very low feed rate.  This is bad for the cement kilns economically and bad for the environment.  Any waste burned in an incinerator without a heat recovery system versus an industrial furnace means that more fossil fuel must be consumed and more carbon dioxide generated in the US each year (a concept EPA never discusses).

2.   The price differential for having waste burned in a commercial incinerator versus an approved and permitted industrial furnace can be substantial.  This proposed regulation would discourage waste minimization efforts by generators.  The industrial furnaces mindful of the metals/heat content ratio will charge more for high concentration/low heat content wastes.  The generator seeing his disposal costs increasing as he minimizes his waste generation will certainly think twice about any further waste minimization efforts.

3.  This change in the EPA’s approach to metals emissions control for industrial furnaces will result in considerable expense and time.  Not only in lost customers, but in redesign of control and monitoring schemes, as well as fixing the permits to reflect the new regulations.  None of this will improve the environment!  Indeed the end result is likely to be increased carbon dioxide emissions.


For cement kilns, the EPA assumes that since these industrial furnaces do not do anything specific (i.e., carbon absorption or chemical scrubbing) to capture and reduce mercury emissions, that the SRE for mercury is proclaimed by EPA to be zero.  The EPA is going to have to have a talk with the state of Texas.  They issued an adjudicated permit to TXI that recognizes a significant mercury SRE.

In Section VIII B in the proposed regulation, it states: “Given that no cement kilns burning hazardous waste use a control device which captures mercury from the flue gas streams, for purposes of this analysis, we assumed all sources achieved a SRE of zero.   The effect of that assumption is that the sources with the lowest mercury concentrations in the hazardous waste were identified as the best performing sources”.  This is a serious design flaw in the EPA’s regulation.

By EPA’s own text, this statement is refuted on the same page, 2 paragraphs down.  “We did not use the stack emissions data of preheater/ precalciner kilns in the floor analysis because we believe the mercury emissions are biased low when the in-line raw mill is on-line and biased high when the in-line raw mill is off-line”. (Emphasis added)

The EPA does not offer a reason for its ascribing this data as biased and hence all of it being discounted.  Could an explanation for this phenomenon be that when the raw mill is on-line the raw feed “captures mercury from the flue gas stream”?  The fact that the mercury is subsequently scrubbed from the recycled raw feed material when the raw mill is off-line was clearly the reason the EPA wanted the kilns tested in both the raw mill on-line and raw mill off-line modes.  Now the EPA discounts the data as biased.  Clearly, the raw feed is removing the mercury from the flue gas stream.  This fact does not support EPA’s purpose, however, so the data is ascribed to be biased and so discounted.

Since the cement kilns had no reason to ensure that the mercury was not scrubbed from the recycled dust during the raw mill off-line period, they did not do so.  They met the emissions limit using the prescribed method.  If however, the cement kilns had had a need to reduce their mercury emissions to meet the standard, they could have removed recycled dust from the system to reduce the mercury in the raw feed fed to the kiln during periods when the raw mill was off.  In which case, the mercury emissions during the raw mill off-line period would not have been “biased high” as EPA ascribes those values to be.  Clearly, this is a case where the regulated community is being punished for complying with the regulations.

As noted previously, TXI has a state permit that recognizes a substantial SRE for mercury.  Technically cement kilns do not “use a control device which captures” any metal “from the flue gas stream”.   So why has EPA focused on this concept for mercury only?  Indeed mercury is not generally captured well by the usual cement production process, but some kilns have or could possibly do so if need be.  By proclaiming that an SRE for mercury will be zero the EPA closes off any efforts by cement facilities to even attempt to reduce mercury emissions by making adjustments in its process operations.  In addition, by proclaiming an SRE of zero for cement kilns, the reported emissions will be increased when in actual fact they have not.  This will give the environmental groups more reason to attack waste burning cement kilns.

GCI sees three events resulting from this mercury emissions control regulation:

1.     Cement kilns will have to restrict the amount of waste containing mercury even though  they  could   achieve   the    emission standard  if  they  were  allowed to  utilize   a documented SRE greater than EPA’s proclaimed zero SRE.  These wastes could possibly be disposed of at incinerators or solid waste fuel boilers.   (Though this later option is highly unlikely as the maximum allowable metals emission rate for solid waste fuel boilers is less than 1/6 of that for cement kilns.)  Disposal at incinerators for these wastes as noted before is likely to increase carbon dioxide emissions in the US.

2.     As noted above some cement kilns have already been issued permits that document a significant SRE for mercury and allow mercury feed rates that would be greater than that allowed by the proposed regulation.   The efforts to reconcile these permits with the proposed regulation will entail a significant cost to both the states and the cement facilities for no discernable improvement in mercury emissions control.  A cost that incinerators will not be subject to.

3.     Incinerators are allowed twice the emissions rate per dscm for mercury versus cement kilns.  This regulation will shift more mercury to those devices.  Has the EPA examined the effect of this increase in mercury feed rates at these incinerators?

Clearly these proposed regulations favor incinerators at the expense of industrial furnaces and the environment as a whole.  There is no other justification for how these regulations are written.   The EPA is calling for comments on these proposed regulations.  This proposed regulation was published April 20, 2004.  The EPA must receive comments by July 6, 2004. 

GCI is offering its services to help your company respond to this request for comments.  GCI will be glad to assist you in addressing these issues or other issues more specific to your facility.   Please contact us at 563-652-2822 or by e-mail to dgossman@gcisolutions.com.