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### Kelly, Shaheerah

From: Kelly, Shaheerah

Sent: Thursday, August 29, 2013 5:32 PM

To: Dave Brown; Eric Albright

Cc: Rios, Gerardo; Christenson, Kara

Subject: SPI Cogeneration Project

Thank you for the updates to the GHG BACT analysis you provided on August 6 and August 15. We have reviewed this

information and have further questions about section 3 of the analysis, which addresses step 1 of the BACT analysis. The

section provides a discussion of fluidized bed boilers (FBB) in the context of “redefining the source” and concludes that

SPI’s proposed operation is unable to use a FBB. We believe the information provided is not sufficient to demonstrate

that an FBB design should be eliminated in Step 1. Therefore, we request the following information to assist us in

continuing our review of the on this project.

1. The analysis states that manufacturers of FBBs indicated that their designs were not appropriate for use when the

boiler would be operated at loads less than 50 percent of the rated capacity (i.e., in “turndown” mode). Although

“turndown” mode is not defined, SPI’s January 23, 2012 letter to EPA generally describes “turndown” mode as

periods when steam is generated at rates as low as 20 percent maximum load. Please provide more details

regarding the information you obtained from manufacturers.

2. The analysis states that a FBB is not appropriate for use at loads less than 50% of capacity (turn down mode)

because the turndown makes FBBs “impractical.” Please describe the technical impracticalities of a FBB.

3. The analysis states that SPI’s unit will be expected to achieve significant load changes (e.g., 100% to 50%) within a

short period of time (e.g., 1 hour) and FBB’s cannot accommodate abrupt load changes. However, SPI’s January 23,

2012 letter states that “because PG&E will provide advance notice of power needs, it is unlikely that the steam

demand variations will require quick responses from the boiler; the variability will be on a day

‐ to

‐ day basis, rather

than hour

‐ to

‐ hour.” Please clarify whether how often load changes will be expected to occur (i.e., hourly, daily, or

weekly, etc).

4. North Springfield Sustainable Energy Project in Vermont and WE Energies in Wisconsin are two recently permitted

cogeneration projects that will construct or have constructed biomass

‐ fired FBBs. It is not clear how these projects

are distinguishable from SPI’s cogeneration operation. Please provide a comparison of these projects and the SPI

Anderson project and how these FBB facilities are distinguishable SPI’S cogeneration operation.

5. The analysis states the following: “The power purchase agreement associated with supplying generated electricity to

the grid requires a high level of availability; the electrical generation commitments for this unit are not compatible

with accommodating an exploratory or innovative application of existing technology.” There are other facilities that

use biomass

‐ fired FBBs. Please clarify why SPI believes FBB is an “exploratory or innovative application of existing

technology.”

If this information is not provided or not sufficient, we may need retain FBB as an available design. If we continue to

include FBB as an available design, then SPI should provide cost information for a Step 4 analysis of cost effectiveness.

We look forward to your response.

************************************

Shaheerah Kelly

U.S. Environmental Protec tion Agency, Region 9

Permits Office, Air Division

San Francisco, CA 94105

Phone: 415-947-41562 Fax: 415-947-3579

Email: kelly.shaheerah@epa.gov