Appendix C to Subpart DDDD of Part 63 - Considerations for a Small-Scale Kiln Emission Testing Program

1.0Purpose

Emissions test data from small-scale lumber kilns can be used to reasonably approximate emissions from full-scale lumber kilns if representative lumber samples are dried and the venting characteristics of the small-scale kiln mimic those of the full-scale kiln. This appendix provides a list of considerations that must be taken into account by facilities conducting small-scale lumber kiln emissions testing to approximate emissions from their full-scale lumber kilns for purposes of the low-risk demonstration described under appendix B to subpart DDDD of part 63.

The considerations described in this appendix apply only for small-scale lumber kiln emissions testing conducted to provide data for the low-risk demonstration described under appendix B to subpart DDDD of part 63. Permitting authorities may require different procedures for testing or estimating lumber kiln emissions for purposes other than the low-risk demonstration described under appendix B to subpart DDDD of part 63.

2.0Considerations for Lumber Samples

2.1A written plan must be developed for obtaining representative lumber samples to use as charges at the small-scale kilns. The plan must discuss how the samples are selected and handled and the basis upon which they are considered to be representative. If possible, information on the harvest site, date harvested, segregation from other lumber (if segregated), and processing at the sawmill must be included. If this information is unavailable, a general description of the sawmill's wood procurement and processing practices must be provided. The affected source and testing laboratory must approve the written test plan before beginning the small-scale kiln testing.

2.2Samples must not be subject to significant air drying during processing, shipping, or storage prior to charging into the small-scale kiln.

2.3Enough lumber must be collected to provide for extra lumber charges in case of testing failures.

2.4Information on the lumber used for each small-scale kiln charge must be reported including the items in paragraphs 2.4.1 though 2.4.4 of this section:

2.4.1Total kiln charge, board feet,

2.4.2Nominal dimensions of lumber dried (for example, 2x4s),

2.4.3Moisture content (dry basis) of the green lumber, and

2.4.4Moisture content (dry basis) of the kiln dried lumber.

3.0Considerations for Kiln Operating Parameters

The small-scale kiln must operate in a similar manner to the full-scale kilns for items 3.1 through 3.3 of this section. The small-scale kiln must operate in a reasonably consistent manner from charge-to-charge for all items (3.1 through 3.5) listed in this section.

3.1Air velocity through the kiln charge.

3.2Temperature profiles or kiln schedules (wet-bulb/dry-bulb temperatures throughout the kiln cycle).

3.3Ending moisture content (dry basis) of the lumber (may need to be mathematically adjusted for small-scale kilns).

3.4Kiln venting profile (trend) for the sample event/kiln cycle (normalized to a board foot or thousand board feet).

3.5Mass emission rate profile (trend) for the sample event/kiln cycle.

4.0Considerations for Emission Sampling

4.1Sample equipment must be able to sample gases with high moisture content.

4.2You must accurately measure/calculate total kiln exhaust and exhaust moisture content. If direct measurements are impractical other methods used must be explicitly discussed in the report.

4.3You must accurately measure the concentration of the compounds of concern either in the kiln exhaust or at a proper location within the kiln.

5.0Considerations for Sample Intervals and Sampling Runs

5.1A minimum of two full kiln cycles or batches must be tested to determine the emissions for a particular wood species or for a facility utilizing only one wood species.

5.2You may use a single kiln cycle for emission values for wood species that require more than 3 days to dry.

5.3Since kiln drying cycles typically exceed 20 hours, it is suggested that sampling be conducted in intervals throughout the drying cycle. Three hours provide a reasonable sample interval (sample run), but sampling equipment or manpower may dictate other schedules. Sampling equipment “turnaround” will result in gaps in the kiln emission data. The gaps must not exceed 45% of the kiln cycle. Data for the gaps occurring at certain periods of time in the drying cycle can be calculated by linear interpolation from the sampling values on either side of the gap. Other techniques may be required if the data gap occurs when the measured data exhibit high levels of variability. As a minimum, sampling intervals must include initial hours of the kiln operating cycle once the kiln has warmed to target wet bulb and/or dry bulb temperatures and begins venting, hours of kiln operation during the middle of the kiln drying cycle, and hours of kiln operation towards the end of the kiln drying cycle.

5.4The final production-based mass emission rate for the small-scale kiln sample event is determined by integrating the area under the mass emission rate profile curve.

6.0Considerations for Reporting

The emissions report must contain the information in paragraphs 6.1 through 6.9 of this section.

6.1Graphical, charge-by-charge results for items 3.2, 3.4, and 3.5 above and numerical data for items 3.1 and 3.3. Describe how the full-scale kiln operates in comparison to the small-scale kiln in order to show that the full-scale kiln drying cycle was reasonably reproduced in the small-scale kiln.

6.2A moisture balance by comparing the water loss (from the green versus dry lumber charge weight difference) to the water exhausted from the kiln (using the exhaust flow rate and moisture content of the exhaust).

6.3A description of the sampling system and sampling methodology.

6.4A summary and background data for all quality assurance measures required by the sampling methods.

6.5Discussion of method detection limits and treatment of values below the detection limit.

6.6An example of emission rate calculations.

6.7Explanation or reference to the methodology used to calculate emissions to the target or desired ending lumber moisture content.

6.8Information outlined in section 2.0 of this appendix, including a discussion of collection and handling of lumber samples.

6.9Data and show calculations for developed emission factors.

7.0Guidance

7.1NCASI Technical Bulletin 845 provides a large amount of detail that can be of assistance in many phases of a small-scale kiln testing program. This report should be viewed as “one way,” not “the only way” to conduct testing.

7.2Oregon State University, Mississippi State University, the University of Idaho, and others have published information regarding operation and testing of small-scale kilns. These publications are a very good source of information on small-scale kilns.