UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

SECTOR POLICIES AND PROGRAMS DIVISION

OFFICE OF AIR QUALITY PLANNING AND STANDARDS

OFFICE OF AIR AND RADIATION

November 22, 2011

MEMORANDUM

SUBJECT: Summary of Pulp Bleaching Technology Review

FROM: Kelley Spence (EPA/OAR/OAQPS/SPPD/NRG)

John Bradfield (EPA/OAR/OAQPS/SPPD/NRG)

TO: Docket EPA-HQ-OAR-2007-0544

This memorandum summarizes the technology review of bleaching technology in pulp mills 

subject to 40 CFR 63, subpart S analyzed for the Risk and Technology Review (RTR) of the 

National Emission Standards for Hazardous Air Pollutants (NESHAP) for the pulp and paper 

industry. 

Background1,2:

Bleaching is the whitening of pulp utilizing a chemical treatment; bleaching can be lignin 

preserving or lignin removing, based on which chemicals are used for treatment. Lignin 

preserving is commonly used for mechanical and secondary pulps, as they are used to produce 

products of which brightness is not always required, such as newspapers. Bleaching that 

removes lignin is typically used for higher grades of paper, such as printing and writing grades, 

where brightness has a significant impact on the final product properties.

Bleaching is performed in a continuous sequence of processing which involves chemical 

treatment, chemical extraction, and washing. Bleaching chemicals include the following: 

chlorine (C), hypochlorite (H), alkaline extraction (E), chlorine dioxide (D), oxygen (O), 

peroxide (P), ozone (Z), and enzymes (X). These chemicals are used in sequence to obtain the 

desired product brightness. For example, a sequence for a highly bleached sheet could be 

OD(EOP)DD, representing oxygen delignification, followed by chlorine dioxide, enriched 

extraction with oxygen and peroxide, followed by two more chlorine dioxide stages. The process 

involves mixing the pulp and bleaching chemicals, reaction of the chemical in a retention tower, 

and removal of the chemical by washing the pulp. Washing is typically performed between each 

stage, to remove chemicals prior to the following stage. An example of this sequence is shown 

in Figure 1.
Figure 1: Bleaching line sequence OD(EOP)DD

Prior to the original NESHAP, chlorine was used for bleaching. It was replaced by most 

facilities with chlorine dioxide to meet effluent guidelines and federal water rules after 

promulgation of “The Cluster Rule” (a simultaneous publication of Federal water and air 

pollution control regulations for the pulp and paper industry). 

Subpart S requires mills to collect and control bleaching process vent emissions from stages 

utilizing chlorinated compounds with a caustic scrubber and to eliminate the use of certain 

bleaching chemicals (chlorine and hypochlorite) from kraft, sulfite, and soda pulp bleach plants.

In this definition, a stage consists of a retention tower, washers, seal tanks, chemical and steam 

mixers, and vacuum pumps. There are three alternative emission limits for total chlorinated HAP 

(excluding chloroform): 

1. Reduce chlorinated HAP emissions by 99% weight 

2. Achieve a total outlet mass emission rate less than or equal to 0.002 pounds chlorinated 

 HAPs per ton oven-dried pulp for all subject stages

3. Achieve an outlet concentration of chlorinated HAPs less than or equal to 10 ppmv 

For chloroform, subpart S requires elimination of the use of chlorine and hypochlorite, or 

compliance with the applicable effluent limitations guidelines and standards in 40 CFR 430.

Washer

O2 

Delig

Pulp

Chlorine 

Dioxide

Stage

(D0) Washer

Extraction

(EOP)

Washer

Chlorine 

Dioxide 

Stage 

(D1)

Chlorine 

Dioxide 

Stage

(D2)

Washer

Bleached Pulp
Developments in Practices, Processes, and Control Technologies

2011 Information Collection Request (ICR) – Part 1 Technologies

The Information Collection Request (ICR)3collected data from the major and synthetic 

minor pulp and paper source facilities in the US. Of these respondents, 98 facilities reported (in 

the bleaching tab of the survey) that they perform pulp bleaching with 164 bleaching lines. 

Elemental chlorine free (ECF) processing was used in 104 bleaching lines, while totally chlorine 

free (TCF) was used in 31 lines, and processed chlorine free (PCF) was used in 22 lines. The 

remaining 7 lines utilized peroxide, sodium sulfate, hypochlorite, chlorine, or a combination of 

these bleaching chemicals. Oxygen delignification was utilized on 42 of the ECF bleaching lines 

to reduce emissions and bleaching chemical cost and consumption. Review of the survey data 

also showed 2 major source facilities, subject only to the effluent guidelines referenced in section 

63.445(d)(1) that utilize chlorine as a bleaching agent and 2 that utilize hypochlorite. Options 

were not recommended for ending the use of chlorine and hypochlorite at these facilities, as it 

would be a change to the effluent guidelines, not the air regulations. 

There were 108 reported scrubbers in the Part I database. Packed-tower caustic scrubbers 

were the most popular type of air pollution control device used to collect and reduce emissions. 

Packing material was typically saddles made of polyvinyl chloride (PVC) and emissions 

reductions were reported at greater than 99%. White liquor, weak wash, and sodium hydroxide 

with fresh water were commonly reported as the source of liquid for the scrubber. 

Table 1: Summary technologies from ICR part I review

Number of Facilities

Facilities performing bleaching 98

Bleach lines 164

 ECF (elemental chlorine free) 104

 TCF (totally chlorine free) 31

 PCF (processed chlorine free) 22

 Other 7

O2 delig pretreatment 42

Facilities (59) provided bleach plant scrubber test reports for chlorine and chlorine dioxide with 

their Part I ICR responses. The common test methods were EPA M26A and NCASI 520 & 548. 

The majority of tests were performed once to show compliance, however, several permitting 

authorities required testing annually or every five years (once per permit cycle).

Review of RBLC

Review of the RBLC identified two facilities (RBLC ID: OK-0112 and WI-0205) with VOC 

BACT-PSD control methods for bleaching. The facility in Oklahoma utilized bleaching using no 

chlorine or chlorine dioxide; the facility in Wisconsin conducted mechanical bleaching with only 

hydrogen peroxide, sodium hydrosulfite, and sodium borohydride4.

Review of Other Available Information

The Multi-Pollutant Emission Reduction Analysis Foundation (MERAF) for the Pulp and 

Paper Sector report was reviewed for additional information5. The report was prepared by
AMEC Forest Industry Consulting for Environment Canada and The Canadian Council of 

Ministers of Environment (CCME). This report identifies the current best design for chlorine 

dioxide generation as venting miscellaneous vents from the process through a tail gas scrubber 

and to use the tail gas packed tower scrubber (using chilled water) after the chlorine dioxide

absorption tower to reduce air emissions.

Mills that use Chlorine Dioxide (ClO2) for bleaching must generate it on site since it is 

unsafe to transport. A review of the air permits collected under Part I of the ICR indicates that 

the control technology discussed above, caustic scrubbing, is typical for the control of 

chlorinated compounds from ClO2 generation units and is equally effective (i.e. 99%+). Because 

similar technology is also required for bleaching vents employing chlorinated compounds under 

Subpart S, facilities can employ a common scrubber for both processes instead of a stand alone 

scrubber.

Available HAP Emissions Data:

Substantial HAP emissions reductions were achieved through the implementation of subpart 

S for beaching vents. HAPs from this process originate in the incoming pulp or from side 

reactions that occur during bleaching.

2011 Information Collection Request (ICR) – Part II Data

A total of approximately 2,600 tons of HAP per year are emitted from bleaching, according 

the ICR Part II data collected. The average amount emitted from these facilities is approximately

38 tons per year.

NCASI Data

Toxic air emissions from kraft mill bleach plants were tested and reported by NCASI 

(Technical Bulletin No. 973, page 15-25), mean emission factors are presented in Table 2. Of the 

United States facilities tested, only 5 of 54 were either ECF or TCF facilities. All facilities tested 

in Canada (6) were ECF mills. This means that the emission factors shown in Table 2 are limited 

in their representation of chlorinated HAPs from mills utilizing ECF or TCF bleaching. Also 

noted is that chloroform is formed at approximately 0.3 – 3.0 lb/ODTP in hypochlorite 

bleaching; ECF mills, however, only produce 0.005 lb/ODTP. The quality of bleach plant 

scrubber shower water and type of wood are thought to have an impact on VOC compounds 

from the bleach plant. 
Table 2: Summary of air toxic emissions from 

kraft mill bleach plants (NCASI TB 973) 

Pollutant

Non-ECF

Emissions 

(lb/ADTBP)

Non-ECF

No. of Sources

ECF 

Emissions 

(lb/ADTBP)

ECF 

No. of Sources

Acetaldehyde 1.64E-03 39

Acetone 3.70E-03 47

Acetophenone -- 15

Acrolein 6.23E-05 15

Acrylonitrile <1.3E-04 1

Aniline <3.7E-08 1

Benzaldehyde 2.80E-04 12

Benzene 5.74E-05 42

Biphenyl -- 3

Bromodichloromethane 3.70E-03 8

Bromomethane <6.4E-04 1

1,3-Butadiene 4.94E-05 6

Carbon Disulfide 1.11E-04 5

Carbon Tetrachloride 1.92E-04 16 5.06E-06 2

3-Carene (sftwds) 4.72E-03 10

3-Carene (hdwds) -- 3

Catechol <8.4E-08 1

Chlorobenzene 9.30E-04 14 1.07E-05 8

Chloromethane <8.8E-04 1

m-Cresol -- 2

o-Cresol 2.68E-03 5

Cresols (mixed isomers) -- --

Crotonaldehyde 6.20E-05 2

Cumene 2.20E-04 2

Cyclohexanone 9.40E-05 5

p-Cymene (sftwds) 3.84E-04 5

p-Cymene (hdwds) -- 3

1,2-Dibromoethane 2.33E-04 3

1,1-Dichloroethane <9.7E-05 1

1,2-Dichloroethane 6.90E-05 13 -- 8

1,1-Dichloroethene <1.8E-03 1

1,2-Diochloropropane <9.1E-05 1

1,2-Dichloroethylene 3.20E-04 13 9.30E-06 7

1,2-Dimethoxyethane -- 3

Ethanol 2.50E-03 24

Ethyl Benzene 8.00E-06 3

Formaldehyde 6.21E-04 30

Hexachlorocyclopentadiene 4.34E-03 1

Hexachloroethane -- 6 2.50E-02 1

n-Hexane 2.80E-05 12

Hydrochloric Acid 2.30E-02 7

Iodomethane <5.3E-05 1

Isopropanol 1.48E-03 17

Limonene (sftwds) 5.20E-04 1
Pollutant Emissions 

(lb/ADTBP) No. of Sources

ECF 

Emissions 

(lb/ADTBP)

ECF 

No. of Sources

Limonene (hdwds) -- 1

Methanol 1.62E-01 57

Methyl Ethyl Ketone 1.40E-03 48

Methyl Isobutyl Ketone 7.56E-04 24

Methylene Chloride 1.69E-03 33 1.67E-04 7

Napthalene -- 4

Phenol 4.96E-03 17

Alpha-Pinene (sftwds) 1.60E-02 24

Alpha-Pinene (hdwds) 5.83E-03 7

Beta-Pinene (sftwds) 6.39E-03 23

Beta-Pinene(hdwds) 2.14E-03 5

Propionaldehyde 7.01E-04 8

Styrene 2.04E-04 22

Terpenes (sftwds) 3.18E-02 9

Terpenes (hdwds) 7.70E-03 8

Alpha-Terpineol -- 2

Tetrachloroethylene 3.74E-04 10 -- 7

Toluene 2.37E-04 23

1,2,4-Trichlorobenzene 2.73E-03 14 1.45E-04 6

1,1,1-Trichloroethane 2.11E-04 13 -- 8

1,1,2-Trichloroethane 2.66E-04 13 6.85E-06 1

Trichloroethylene 4.43E-04 21 9.70E-06 4

Valeraldehyde 5.10E-04 6

m-,p-Xylene 1.93E-04 12

o-Xylene 1.03E-04 12

Xylenes (mixed) 2.17E-04 21

VOCs as C 1.03E-01 34

Review of Other Available Data

The Multi-Pollutant Emission Reduction Analysis Foundation (MERAF) for the Pulp and 

Paper Sector report was reviewed for additional data (i.e., Canadian data). A summary of the 

estimated emissions are shown in Table 3 for emission points in the bleaching process, based on 

stage chemical type. As expected, the chlorine and hypochlorite bleaching stages emit 

significantly more HAP than the extraction and the chlorine dioxide stages.
Table 3: Summary of estimated emissions from MERAF (kg/t)

Emission Point Total HAPa Chloroform Chlorine Methanol

C-stage tower 0.054-0.252 0.0009-0.01 0.05-0.21 0.00062-0.029

C-stage washer 0.062-0.647 0.0009-0.0113 0.05-0.21 0.009-0.415

C-stage seal tank 0.0084-0.323 5.5E-5 - 7.2E-4 0.00127-0.0053 0.0067-0.311

E-stage tower 0.013-0.026 0.0014-0.01 0-0.003 0.0027-0.0054

E-stage washer 0.031-0.168 0.0014-0.01 0-0.003 0.0035-0.078

E-stage seal tank 0.013-0.101 0.00009-0.0005 0-0.000076 0.0026-0.029

D-stage tower 0.011-0.036 0.00003-0.02 0.01 0.0002

D-stage washer 0.01-0.06 0.00003-0.02 0.01 0.00001-0.003

D-stage seal tank 0.0005-0.02 0.000003-0.001 0.0003 0.000008-0.002

H-stage tower 0.088-0.62 0.04-0.05 0.01 0.00049-0.0063

H-stage washer 0.15 0.04 0.01 0.091

H-stage seal tank 0.074 0.003 0.0003 0.068

Acid sewer 0.12-0.52 0.008-0.005 0 0.05-0.5

Caustic sewer 0.041-0.032 0.002-0.0023 0 0.03-0.3

Regulatory Options:

Section 112(d)(6) of the CAA requires EPA to review and revise the MACT standards, as 

necessary, taking into account developments in practices, processes, and control technologies. 

The information presented in this memorandum is relevant for consideration in the development 

of regulatory options under 112(d)(6).

As explained in the previous sections of this memo, bleach plant chlorinated vent gas 

emissions are effectively controlled at 99%. Our technology review did not identify any new 

control technologies that had been installed to reduce emissions further beyond the current 

requirement to control 99%+ at bleaching vents where chlorinated bleaching compounds are 

used. It is the staff recommendation not to amend the current NESHAP regarding bleach plant 

vents.

References:

1. Pulp and Paper NESHAP: A Plain English Description. U.S. Environmental Protection 

Agency, Office of Air Quality Planning and Standards. EPA-456/R-98-008. November 

1998.

2. Smook, G. Handbook for Pulp & Paper Technologists. 3rd Edition. Angus Wilde Publications 

Inc., Bellingham WA. 2002. 

3. Pulp and Paper ICR 2011.

4. Memorandum from T. Holloway, C. Gooden, and K. Hanks, to J. Bradfield and B. Schrock, 

EPA. Summary of RBLC and Other Findings to Support Section 112(d)(6) Technology 

Review for Pulp and Paper NESHAP. RTI. 2011.

5. Multi-pollutant Emission Reduction Analysis Foundation (MERAF) for the Pulp and Paper 

Sector. AMEC Forest Industry Consulting. 2002.