ncasi

NATIONAL COUNCIL FOR AIR AND STREAM IMPROVEMENT, INC.

P.O. Box 13318, Research Triangle Park, NC 27709-3318

Phone (919) 941-6400 Fax (919) 941-6401

John E. Pinkerton, Ph.D.

Vice President, Air Quality

(919) 941-6406

jpinkerton@ncasi.org

July 15, 2011

Mr. Brian Shrager

Energy Strategies Group (C205-01)

Sectors Policies and Program Division

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711

Dear Brian:

Subject: CO Emission Limits for the Biomass Stoker/Sloped Grate/Other Subcategory

We are making this submittal in response to EPA’s May 18, 2011 call for additional data and information 

related to the reconsideration of the Boiler MACT standards. Attached are two documents.

The first document Review of the Biomass Stoker CO Limits and Suggestions for Revisions is a review of 

the emissions information and statistical calculations that were the basis for the CO emission limits for 

the biomass stoker/sloped grate/other subcategory promulgated by EPA. As previously discussed with 

you, we believe there are significant problems with the data and analysis carried out by EPA and ERG to 

arrive at the limits. Furthermore, there are additional emission test reports being submitted by several of 

the ’best performers’ which will have a major effect on the limits. In our review, we have assessed how 

the limits would change upon incorporation of these additional test results into the UPL calculations. 

Finally, we have included an analysis of 12 months of CO CEMS data from two boilers that we think 

would meet the criteria for being substantially similar to the best performing units for CO. The raw data 

for these two boilers can be provided to EPA upon request. 

The second document Developing an Alternative CO Limit for Biomass Stoker Units Having a CO CEMS

deals with establishing an alternative CO limit for this subcategory for units with CO CEMS. This 

subject was discussed at the June 7 meeting with yourself, Bob Wayland, and Peter Tsirigotis. An 

analysis based on the 12 months of CEMS data from the two boilers mentioned above was conducted to 

demonstrate how such a limit could be developed and what type of numerical limits might be appropriate 

for averaging times of one day, one week, and one month. 

In our opinion, there are critically important questions that EPA must resolve as soon as possible to avoid 

needless iterations of the floor analysis for this subcategory.

1. Will EPA modify the definitions for the stoker/sloped grate/other, Dutch oven/suspension burner, 

and/or hybrid suspension grate boiler subcategories? Given the vague and somewhat 

overlapping definitions, many boilers could be placed in more than one of these subcategories. 
The implications for the CO and dioxin/furan limits for the three subcategories are potentially 

significant.

2. Which secondary materials will be classified as solid waste? Because a significant number of 

boilers were burning secondary materials during their CO tests, it is not clear if EPA would allow 

such tests to be used in the floor analysis. Furthermore, many of the biomass boilers equipped 

with CO CEMS routinely burn one or more secondary materials, bringing into question whether 

data from such units would be used by EPA to establish alternative CO limits.

3. How will EPA determine if a boiler with a CO CEMS is similar to a top performer, and will EPA 

continue to rely on Method 10 short-term tests where over 90% of the boiler heat input came 

from biomass to identify the top performers in each biomass subcategory?

4. Will EPA make changes to the default CO span gas assumptions that have been made for the 

majority of the best performers in the biomass stoker/sloped grate/other subcategory, and if so, 

what changes will be made?

The National Council was informed by AF&PA that at an industry coalition meeting with Deputy 

Administrator Perciasepe and Deputy Assistant Administrator McCabe, AF&PA stated its commitment to 

conduct additional new boiler tests to examine the variability of best performers over a wider range of 

conditions. NCASI has been tasked to manage this testing program. We are very uneasy about selecting 

units for additional CO CEMS testing until the above questions are answered. Thus we need EPA’s 

feedback as soon as possible so that boilers can be selected for the testing program and arrangements with 

a sampling contractor can be finalized. 

We had planned to do a similar analysis for the biomass fluidized bed subcategory CO limit, but it could 

not be completed by July 15. Please let us know if EPA would still consider this analysis if it were to be 

submitted in mid-August. 

We would be happy to discuss any questions you or your contractor may have on this material.

Sincerely,

John E. Pinkerton

cc: R. Wayland, EPA 

P. Tsirigotis, EPA

J. Eddinger, EPA

T. Hunt, AF&PA 

A. Jain, NCASI

A. Someshwar, NCASI