Susan Thorneloe US EPA National Risk Management Research Laboratory Research Triangle Park, North Carolina September 13, 2006 Susan Thorneloe US EPA National.

Susan Thorneloe

US EPANational Risk Management Research Laboratory

Research Triangle Park, North Carolina

September 13, 2006

Susan Thorneloe

US EPANational Risk Management Research Laboratory

Research Triangle Park, North Carolina

September 13, 2006

Evaluating Life-Cycle Environmental Trade-Offs from Use of FGD Gypsum

Evaluating Life-Cycle Environmental Trade-Offs from Use of FGD Gypsum

Research Objective

Evaluate impact of air pollution control on coal combustion residues (CCRs)

Identify potential cross-media transfers of mercury and other metals from CCR management which includes FGD gypsum and fly ash

Compare life-cycle environmental tradeoffs from use of CCR and non-CCR materials

BackgroundIn March 2005, EPA announced a multipollutant approach to reduce power plant air emissions through the Clean Air Interstate Rule (CAIR) and the Clean Air Mercury Rule (CAMR) through cap and trade approach.

Air pollution control (APC) results in transferring metals from the flue gas to fly ash and other APC residues.

Anticipate that wet scrubber usage and production of FGD gypsum will double or triple in response to CAIR.

Primary focus on mercury but also interest in arsenic, selenium, and other constituents of concern.

Key release route for land-managed CCRs is leaching to groundwater. Concern also for release to surface waters, re-emission of mercury (e.g., cement kilns), and bioaccumulation.

Importance of Coal - Electricity Production by Fuel for 1980 – 2030 (Billion kilowatt hours) Source: DOE/EIA 2006

CCR Production and Utilization

Production122 million tons

Source: ACAA 2004 CCR Survey; DOE, 2005

40% Utilization 49 million tons

Cement/Concrete

36%

Construction25%

Mining5%

Wallboard17%

Waste Stabilization8%

Other 9%

Fly Ash 57%

Bottom Ash 15%

Boiler Slag 2%

FGD Material 25%

FBC Ash1%

Calculating Hg Mass Balance in Response to CAIR and CAMR Implementation

0

10

20

30

40

50

60

70

80

90

Tons of Mercury

2004 2010 2018

Hg Emissions (Flue GasStack)Hg in CCRsDisposed

Hg in CCRsUtilized

Source: Thorneloe, 2006Source: Thorneloe, 2006

Projection of Scrubber Use at Existing Units

0

50

100

150

200

250

300

350

MegaWatts (Thousands)

2004 2010 2020

Total ProjectedCoal-FiredCapacity

Projected Coal-Fired Capacitywith WetScrubbersProjectd Coal-Fired Capacitywith DryScrubbers

COAL SUPPLY BOILER

SUPERHEATER

SCR

AMMONIAINJECTION

SORBENT

SORBENTINJECTION

ESP OR FF

ASH + SORBENTREMOVAL

WET FLUE GASDESULFURIZATION(FGD) SCRUBBER

FGD GYPSUMOR SCRUBBERSLUDGE REMOVAL

FLUE GAS STACK

Impact of Air Pollution Control on CCR Characteristics and Utilization

9

Tracking Fate of Hg and Other Metals Through Life-Cycle Analysis

In 2004, 31 million tons of wet scrubber residues were produced. – 12 million tons (or 40%) used to make gypsum.

– 90% of the 12 million tons used to make wall board.

– Expect increased interest in other uses of FGD gypsum such as use as soil amendment (collaboration with China).

Comparing life-cycle environmental tradeoffs for production of wallboard with and without use of FGD gypsum. This is also being done for the production of cement and asphalt.– Considering potential pathways of environmental release

(includes used of leaching and thermal stability studies)– Need to understand stability of Hg and track fate of Hg and other

metals on a life-cycle basis.

– Information will help with ensuring if intended mercury reductions are achieved in mercury cap and trade program.

Series of 4 Reports Documenting Findings

1. Enhanced sorbents for mercury capture (Jan, 2006)

2. FGD gypsum and other scrubber residues (2007)

3. Residues from other air pollution control strategies (2008).

4. Probabilistic assessment of mass release rate for a range of management scenarios, including disposal and beneficial use (2008).

Leach Testing Protocol ORD adopted OSW’s recommended approach to evaluating the

leaching potential of coal combustion residues (CCRs) anticipated to be generated as a result of CAIR & CAMR

OSW recommended the use of a leach testing framework developed by Kosson et.al, from Vanderbilt University.

• The detailed protocol is published at: Kosson, D.S., van der Sloot, H.A., Sanchez, F. and Garrabrants, A.C., 2002. An Integrated Framework for Evaluating Leaching in Waste management and Utilization of Secondary Materials. Environmental Engineering Science 19(3):159-204.

• An additional publication on using the data in probabalistic modeling is: Sanchez, F., Kosson, D.S., 2005. Probabilistic approach for estimating the release of contaminants under field management scenarios. Waste Management, 25(5), 643-472.

OSW’s recommendation was based on the fact that this approach:

• Most fully considers the key conditions affecting leaching for a range of CCRs and their plausible management;

• Is appropriate for evaluating a broader range of materials, beyond fly ash; and

• Addresses previous concerns raised by Science Advisory Board.

Leach Testing ProtocolConsiders range of values for key parameters that

both affect leaching and vary with disposal and reuse: pH: The solubility of constituents of concern vary with pH. Liquid to Solid ratio (L/S):

Reflects rainfall infiltrationLower L/S ratio can result in different pH and contaminant concentration

Waste form –Fine particles (equilibrium test)Stabilized and solid materials (mass transfer effects)

A single set of test results can be used to evaluate leaching potential for a range of management scenarios including disposal and reuse.

Data Can Support Environmental Assessment Modelling for Different Scenarios……..

Drinking water well

Landfill

Road base

Plant

Agriculture

Coastal protectionContaminate

d soil

Drinking water pipes

Mining

Construction

sewer

Drinking water well

NAS Concern for Providing Full Characterization of reuse

materials ….• Historically, CCRs are given special

consideration because of their wide range of beneficial use applications Since 1991, CCR utilization increased from 31

to 40%.

RCC goal is to increase CCR utilization to 50% by 2010.

• Recent National Academy of Science (NAS) report on CCR use in mine filling stated that full characterization should not be cut short “in the name of beneficial use”.

Arsenic Leaching as a Function of pH for Coal Fly Ash

MDL

ML

5.8

25.95MCL

0.001

0.01

0.1

1

10

100

1000

10000

2 4 6 8 10 12 14

pH

As [µ

g/L]

SR2-LAB - A SR2-LAB - B

5% 95%

5%

95%

MDL

ML

11.3

237.37

MCL

0.001

0.01

0.1

1

10

100

1000

10000

2 4 6 8 10 12 14

pH

As

[µg/

L]

SR2-GAB - A SR2-GAB - B

SR2-GAB - C

5% 95%

5%

95%

Facility L Facility C

MDL

ML

9.5

4.8

MCL

0.001

0.01

0.1

1

10

100

1000

10000

2 4 6 8 10 12 14

pH

As

[g/

L]

SR2-BPT-0001 - A

SR2-BPT-0001 - B

SR2-BPT-0001 - C

5% 95%

5%

95%

Brayton Point

Coal Fly Ash Results For Facilities Using Sorbents for Enhanced Hg Capture

Mercury: Low totals and leach Total: 0.1-1 mg/kg Leach: Most 0.1 ug/L or lower

• MCL=2 ug/L• TC= 200 ug/l

Low leach variability relative to pH Results do not include modeling of

transport from landfill site to drinking water well (i.e, no DAF applied)

Ranges of Hg Leachate Concentrations (From Report 1 on Use of Enhanced Sorbents)

Coal Fly Ash Results For Facilities Using Sorbents for Enhanced Hg Capture

• Arsenic: Totals and leach high/variable Total: 20- 500 mg/kg Leach: 1-1000 ug/L

• MCL=10 ug/L• TC=5000 ug/L

Leach variability is moderately to highly pH dependent

Results will be used in modeling of transport from disposal or management site to drinking water well

Ranges of As Leachate Concentrations (From Report 1 on Use of Enhanced Sorbents)

Coal Fly Ash Results For Facilities Using Sorbents for Enhanced Hg Capture

• Selenium: Totals moderate; leach high/variable Total: 20- 500 mg/kg Leach: 1-10,000 ug/L

• MCL=50 ug/L• TC=1000 ug/L)

Leach variability moderately pH dependent

Results will be used in modeling of transport from disposal or management site to drinking water well

Ranges of Se Leachate Concentrations (From Report 1 on Use of Enhanced Sorbents)

What do the CCR Leach Test Results Mean for CCRs Evaluated to Date? For CCRs evaluated in Report 1, found

apparent low release potential for Hg from CCRs that are land applied or landfilled Current emphasis is on wet scrubber

residues including FGD gypsum Arsenic and Selenium showed higher potential

for release by leaching: Highest As leach values at 20% of TC Highest Se leach value is 10 x TC

Arsenic was identified as a concern in the 1999 Report to Congress on coal combustion wastes

Indicate importance of evaluating full range of CCRs and use of results in risk assessment modeling.

How Is This Information To be Used?

Beneficial use programs to help clarify appropriate practices and quantify potential benefits RCC program for coal combustion products State, Federal (DOE, DOT, DOI), and industry programs

that promote beneficial use

Regulatory efforts including Effluent guidelines (OW), RCRA Subtitle D for coal combustion waste (OSW), Cap and trade programs through implementation of CAIR

and CAMR (OAR)• Identifying potential cross media transfers• Helping to ensure that intended reductions are achieved

Cement kilns (MACT) – issue raised regarding use of CCRs (OAR)

• Helping to quantify life-cycle environmental tradeoffs

Development of a CCR Management Decision Support Tool

LeachXS is a set of integrated software tools under development to provide:

• Guidance on the selection of test methods to answer specific management option questions

• Database of leaching characteristics, lysimeter and field data for wide range of materials for performance comparison

• Database of management scenarios (disposal, beneficial use), case studies and prior experience

• Data management, evaluation and presentation to communicate scenarios and results

• Geochemcial speciation and coupled reaction - mass transfer models to estimate long-term release for specific combinations of CCR material and use or disposal scenario

• Quality control for materials production and use – tracking CCR material conformance with use criteria

FGD Gypsum is Under Evaluation for these Scrubber Facilities

Facility Code

Coal Rank

Scrubber Type

Oxidation

Type

SCR Particulate Control

O,N Bit Wet Forced Yes ESP-CS

O,N Bit Wet Forced No ESP-CS

B,K Sub-Bit Wet Natural Yes ESP-CS

B Sub-Bit Wet Natural No ESP-CS

M Bit Wet Inhibited Yes ESP-CS

M Bit Wet Inhibited No ESP-CS

A Bit Wet Natural SNCR-On

Fabric Filter

Conclusions Working to develop information that will provide

understanding of impact of air pollution control on FGD gypsum and coal fly ash; current emphasis is on FGD gypsum

Conducting life-cycle analysis that allows comparison of environmental tradeoffs from use of CCR and non-CCR materials

Providing information to help determine if intended reductions of CAMR cap and trade programs are being achieved

Developing leach testing protocol into official EPA method in SW846

Identifying potential CCR management practices of concern resulting from application of new air pollution control technology at coal-fired power plants