EPA Releases Boiler Rules for C&D Wood

Comments
Commenters argued that, although C&D-derived wood is discarded by construction and demolition sites, it is sufficiently processed into a non-waste fuel. It is received at a fixed C&D processing facility as part of loads from construction and demolition sites. Potential contaminants are removed as much as possible before it enters the plant. Clean C&D wood is then separated out from the rest of the incoming stream one of two ways; either through mechanical means or through humans sorting along a specially built picking line. Painted and treated wood is identified either visually or using x-ray fluorescence (XRF) analyzers. After separation, the wood is ground to a specific size and density per the specification of the plant using the biomass product. The creation of natural wood products follows a similar processing path, except that C&D wood is more carefully prepared because of the chemical analysis the C&D product undergoes.

Commenters also stated C&D-derived wood meets the legitimacy criterion for having a meaningful heating value. They stated that C&D-derived wood has a heating value of between 7,000-8,200 Btu/lb, and thus, should be considered a non-waste fuel. Data from one plant that combusts C&D-derived wood found that it had a heating value that ranges from 6,700-9,000 Btu/lb, with an average value of 8,200 Btu/lb.

One company provided chemical constituent data on C&D-derived wood used at its plant to demonstrate the material meets the legitimacy criterion for contaminants. The results of this analysis found the chemical constituents were comparable to or lower to those found in coal (of unknown source or type). See Table 1 below for the results of this study.

Some commenters discussed studies that concluded that the use of appropriately processed C&D wood is similar in its emission profile to that of virgin wood, although some older studies indicated an increase in metals emissions (likely due to the inclusion of treated wood).⁴⁹ Another commenter submitted a life-cycle assessment that described how the recovery of C&D wood as a fuel decreased greenhouse gas emissions. This study found that combusting all C&D wood generated in New Hampshire per year (280,000 tons) will off-set energy from the northeast power grid and, therefore, result in 70,000-130,000 tons less of carbon emissions, 600 tons/year less of particulate matter, 430 tons/y less of NOx, 2,300 tons/y less of SOx, 890 tons/y less of CO, and 10 lb/y less of lead. Even when compared simply to the combustion of virgin wood, it was found that the combustion of C&D-derived wood had lower impacts: 16,700 metric tons of carbon equivalents were offset, 50 tons/y less of particulate matter, 200 tons/y less of NOx, 485 tons/y less of SOx, and 69 tons/y less of CO. ⁵⁰

EPA’s Response
The proposed rule included clean construction wood in the definition of traditional fuels.
The final rule retains this conclusion, although clarifies the definition of traditional fuels to include alternative fuels. Clean cellulosic biomass is an alternative fuel as they are clean cellulosic materials that are indistinguishable in composition from wood that is commonly burned in combustion units. We note the final definition of traditional fuels clarifies this category includes clean demolition wood as well.

On the other hand, C&D-derived wood that is not clean would not be considered a traditional fuel, but a solid waste under today’s rule. However, C&D-derived wood can be classified as a non-waste fuel if it has been sufficiently processed and meets the legitimacy criteria. C&D-derived wood is typically sorted to remove contaminants (e.g., lead-painted wood, treated wood, non-wood materials), and size reduced prior to burning, producing material that likely meets the processing and legitimacy criteria for contaminants. (We would also note the technology in use today to remove contaminants from C&D-derived wood has increased considerably.) The data provided by one company demonstrates that C&D-derived wood can be sufficiently processed to meet the legitimacy criterion for four contaminants, even when these contaminants are compared to untreated wood concentrations presented in the background document, Preliminary Characterization Study Prepared in Support of the Proposed Rulemaking—Identification of Nonhazardous Secondary Materials that are Solid Waste: Traditional Fuels and Key Derivatives.⁵¹ A complete determination, however, would also include the comparison of As and Cr concentrations. We would also note that based on the data presented, C&D derived wood also meets the meaningful heating value criterion.

With respect to those comments that argued that C&D derived wood have an emissions profile similar to that of virgin wood and that it would decrease greenhouse gas emissions, as we have noted previously, the criterion or test for determining whether a material is burned as a waste or a commodity fuel is the level of the contaminant in the secondary material itself—that is destruction of contaminants indicates a waste treatment activity rather than a commodity fuel.

This is also consistent with the legitimacy criteria that would require that the non-hazardous secondary material, itself, must have contaminant levels that are comparable to (or lower than) those in traditional fuels. In any event, because we had no information from the studies on the extent that these C&D materials were sufficiently processed to remove the contaminants of concern, we do not know what the emissions results from the submitted studies represent.

Comment
Some comments argued there should be a de minimis exemption for C&D-derived wood that is processed to remove painted and treated materials because while most of the contaminants are removed from the C&D derived wood, there still may be a small or de minimis amount remaining on it. Additionally, they also argued that while most non-wood contaminants are removed, there might still remain some small or de minimis amounts of other materials (e.g., paper, insulation, etc.).

EPA’s Response
C&D-derived wood can contain de minimis amounts of contaminants and other materials provided it meets the legitimacy criterion for contaminant levels.

Footnotes
⁴⁸    Source: EPA-HQ-RCRA-2008-0329-0774; Since the legitimacy criterion for contaminants compares concentrations per mass of the material (not per the heating value of the material), all concentrations reported in pounds per billion Btu (lb/billion Btu) were converted into parts per million (ppm) with the assumption that C&D derived wood has a heating value of 8,200 Btu/lb (as fired) and that sub-bituminous and bituminous coal (the most common types of coal to be utilized in combustion units) have a heating value of 8,500 – 14,000 Btu/lb (per Preliminary Characterization Study Prepared In Support of the Proposed Rulemaking –Identification of Nonhazardous Secondary Materials That Are Solid Waste: Traditional Fuels and Key Derivatives, EPA-HQRCRA- 2008-0329-0461.21).
⁴⁹    U.S. EPA, ‘‘Wood Products in the Waste Stream: Characterization and Combustion Emissions, Vol. 1,’’November 1996. National Council for Air and Stream Improvement, Inc. Technical Bulletin (TB) 906, ‘‘Alternative Fuels Used in the Forest Products Industry: Their Composition and Impact on Emissions.’’ September 2005. Larsen, F.S., W.H. McClennen, X. Deng, G.D. Silcox-Person, and K. Allison, 1992. “Hydrocarbon and Formaldehyde Emissions from the Combustion of Pulverized Wood Waste.” Combustion Science and Technology, 85 (1-6) p. 259 – 269.
⁵⁰    Jambeck, J., A. Carpenter, K. Gardner, and K. Wietz, 2007. “University of New Hampshire Life-Cycle Assessment of C&D Derived Biomass/Wood Waste Management,” University of New Hampshire, Durham, NH, December 5.
⁵¹    EPA-HQ-RCRA-2008-0329-0461.21

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