Office of Air and Radiation October 2010 

 

AVAILABLE AND EMERGING TECHNOLOGIES FOR 

REDUCING GREENHOUSE GAS EMISSIONS FROM 

THE PULP AND PAPER MANUFACTURING INDUSTRY 
Available and Emerging Technologies for Reducing 

Greenhouse Gas Emissions from the Pulp and Paper 

Manufacturing Industry 

Prepared by the 

Sector Policies and Programs Division 

Office of Air Quality Planning and Standards 

U.S. Environmental Protection Agency 

Research Triangle Park, North Carolina 27711 

October 2010 
i 

Table of Contents 

I. Introduction............................................................................................................................... 1

A. Description of the Pulp and Paper Manufacturing Process ....................................... 1

1. Wood Preparation ..................................................................................................... 3

2. Pulping ...................................................................................................................... 3

3. Bleaching .................................................................................................................. 4

4. Chemical Recovery................................................................................................... 5

5. Pulp Drying/Papermaking......................................................................................... 6

B. Pulp and Paper GHG Emission Sources .................................................................... 6

C. Pulp and Paper Energy Use........................................................................................ 9

II. Control Measures and Energy Efficiency Improvements for Direct GHG Emission 

Sources.................................................................................................................................... 11

A. Power Boilers, Chemical Recovery Furnaces, and Turbines................................... 12

1. Control Measures and Energy Efficiency Options for Boilers ............................... 12

2. Control Measures and Energy Efficiency Options for Chemical Recovery 

Furnaces and Combustion Units ..................................................................... 16

3. Energy Efficiency Associated with CHP Systems.................................................. 18

B. Natural Gas-Fired Dryers and Thermal Oxidizers................................................... 22

C. Kraft and Soda Lime Kilns ...................................................................................... 23

D. Makeup Chemicals................................................................................................... 25

E. Flue Gas Desulfurization Systems........................................................................... 26

F. Anaerobic Wastewater Treatment ............................................................................ 26

G. On-site Landfills ...................................................................................................... 27

III. Additional Energy Efficiency Improvements ................................................................... 29

A. Energy Efficiency Improvements in Steam Systems...................................... 29

B. Energy Efficiency Improvements in Raw Material Preparation..................... 32

1. Debarking................................................................................................................ 32

2. Chip Handling, Screening, and Conditioning......................................................... 33

C. Energy Efficiency Improvements in Chemical Pulping ................................. 33

1. Digesters (Chip Cooking) ....................................................................................... 33

2. Pulp Washing.......................................................................................................... 34

3. Bleaching ................................................................................................................ 34

D. Energy Efficiency Improvements in Mechanical Pulping .............................. 35

1. Mechanical Pulping ................................................................................................ 35

2. Repulping of Market Pulp....................................................................................... 36

3. Secondary (Recovered) Fiber Processing ............................................................... 36

E. Energy Efficiency Improvements in Papermaking ......................................... 37

1. Paper Machines – Forming and Pressing Sections ................................................. 37

2. Paper Machines – Drying Section........................................................................... 38

F. Energy Efficiency Improvements in Facility Operations ........................................ 40

1. Energy Monitoring and Control Systems ............................................................... 40

2. High-Efficiency Motors.......................................................................................... 40

3. Pumps...................................................................................................................... 40

4. High-Efficiency Fans.............................................................................................. 41

5. Optimization of Compressed Air Systems.............................................................. 41
ii 

6. Lighting System Efficiency Improvements ............................................................ 42

7. Process Integration Pinch Analysis......................................................................... 42

G. Emerging Energy Efficiency Technologies..................................................... 44

1. Raw Material Preparation ....................................................................................... 44

2. Chemical Pulping.................................................................................................... 44

3. Pulp Washing.......................................................................................................... 46

4. Secondary Fiber Processing.................................................................................... 46

5. Papermaking ........................................................................................................... 46

6. Paper Machines – Drying Section........................................................................... 47

7. Facility Operations - Motors................................................................................... 48

IV. Energy Programs and Management Systems.................................................................... 50

A. Sector-Specific Plant Energy Performance Benchmarks................................ 52

B. Industry Energy Efficiency Initiatives ............................................................ 52

EPA Contacts................................................................................................................................ 53

References..................................................................................................................................... 54
iii 

Acronyms and Abbreviations 

AF&PA American Forest and Paper Association 

ANSI American National Standards Institute 

ASB Aerated stabilization basin 

ASD Adjustable-speed drive 

BACT Best available control technology 

BLO Black liquor oxidation 

BLS Black liquor solids 

Btu British thermal unit(s) 

Ca Calcium 

Ca(OH)2 Calcium hydroxide 

CaCO3 Calcium carbonate 

CaCO3MgCO3 Dolomite 

CaO Calcium oxide (lime) 

CH4 Methane 

CHP Combined heat and power 

CIPEC Canadian Industry Program for Energy Conservation 

ClO2 Chlorine dioxide 

CMP Chemi-mechanical pulping 

CO Carbon monoxide 

CO2 Carbon dioxide 

CO2e CO2 equivalent 

DCE Direct contact evaporator 

DIP De-inked pulp 

DOC Degradable organic carbon 

DOE U.S. Department of Energy 

E/T Electric-to-thermal 

EnMS Energy Management Systems 

EPA U.S. Environmental Protection Agency 

EPI Plant Energy Performance Indicator(s) 

ESP Electrostatic precipitator 

FGD Flue gas desulfurization 

gal Gallon(s) 

GHG Greenhouse gas 

GWh Gigawatt-hour(s) 

H2SO3 Sulfurous acid 

HAP Hazardous air pollutant 

HHV Higher heating value 

hp Horsepower 

hr Hour(s) 

HRSG Heat recovery steam generator 

HSO3

-

 Bisulfite 

ICFPA International Council of Forest and Paper Associations 

IPCC Intergovernmental Panel on Climate Change 

ISO International Organization for Standardization 

kg Kilogram(s) 
iv 

kW Kilowatt(s) 

kWe Killowatt(s)-electric 

kWh Kilowatt-hour(s) 

lb Pound(s) 

MC-ASD Magnetically-coupled adjustable-speed drive 

MEE Multiple-effect evaporator 

Mg Magnesium 

min Minute(s) 

MMBtu Million Btu 

MRR GHG Mandatory Reporting Rule 

MSW Municipal solid waste 

mtCO2e Metric tonne(s) of CO2 equivalents 

MW Megawatt(s) 

MWe Megawatt(s)-electric 

MWh Megawatt-hour(s) 

N2O Nitrous oxide 

Na Sodium 

Na2CO3 Sodium carbonate 

Na2S Sodium sulfide 

Na2SO4 Sodium sulfate 

NaOH Sodium hydroxide 

NCASI National Council for Air and Stream Improvement 

NCG Non-condensable gases 

NDCE Nondirect contact evaporator 

NESHAP National emissions standards for hazardous air pollutants 

NH3 Ammonia 

NOX Nitrogen oxides 

NSSC Neutral sulfite semi-chemical 

PCC Precipitated calcium carbonate 

PM Particulate matter 

PRV Pressure reduction valve 

PSD Prevention of significant deterioration 

RCO Regenerative catalytic oxidizer 

RMP Refiner mechanical pulping 

rpm Revolution(s) per minute 

RTOs Regenerative thermal oxidizer 

RTS Residence time-temperature-speed 

SDT Smelt dissolving tank 

SO2 Sulfur dioxide 

SOG Stripper off gas 

STIG Steam injected gas 

TBtu Trillion Btu 

TMP Thermo-mechanical pulping 

TRS Total reduced sulfur 

VOC Volatile organic compound 

WBCSD World Business Council for Sustainable Development 
v 

WRI World Resources Institute 

WWTP Wastewater treatment plant 

yr Year(s) 
 

1 

I. Introduction 

 This document is one of several white papers that summarize readily available 

information on control techniques and measures to mitigate greenhouse gas (GHG) emissions 

from specific industrial sectors. These white papers are solely intended to provide basic 

information on GHG control technologies and reduction measures in order to assist States and 

local air pollution control agencies, tribal authorities, and regulated entities in implementing 

technologies or measures to reduce GHGs under the Clean Air Act, particularly in permitting 

under the prevention of significant deterioration (PSD) program and the assessment of best 

available control technology (BACT). These white papers do not set policy, standards or 

otherwise establish any binding requirements; such requirements are contained in the applicable 

EPA regulations and approved state implementation plans. 

II. Purpose of this Document 

 This document provides information on control techniques and measures that are 

available to mitigate greenhouse gas (GHG) emissions from the pulp and paper manufacturing 

industry at this time. Because the primary GHG emitted by the pulp and paper manufacturing 

industry include carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), and the control 

technologies and measures presented here focus on these pollutants. While a large number of 

available technologies are discussed here, this paper does not necessarily represent all potentially 

available technologies or measures that that may be considered for any given source for the 

purposes of reducing its GHG emissions. For example, controls that are applied to other 

industrial source categories with exhaust streams similar to the pulp and paper manufacturing 

sector may be available through “technology transfer” or new technologies may be developed for 

use in this sector. 

The information presented in this document does not represent U.S. EPA endorsement of 

any particular control strategy. As such, it should not be construed as EPA approval of a 

particular control technology or measure, or of the emissions reductions that could be achieved 

by a particular unit or source under review. 

A. Description of the Pulp and Paper Manufacturing Process 

The manufacturing of paper or paperboard can be divided into six main process areas, 

which are discussed further in the sections below: (1) wood preparation; (2) pulping; 

(3) bleaching; (4) chemical recovery; (5) pulp drying (non-integrated mills only); and 

(6) papermaking. Figure 1 below presents a flow diagram of the pulp and paper manufacturing 

process. Some pulp and paper mills may also include converting operations (e.g., coating, box 

making, etc.); however, these operations are usually performed at separate facilities. 

There are an estimated 386 pulp and/or paper manufacturing facilities in the in the U.S., 

including: 

• 120 mills that carry out chemical wood pulping (kraft, sulfite, soda, or semi-chemical), 

• 47 mills that carry out mechanical, groundwood, secondary fiber, and non-wood pulping, 
 

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• 102 mills that perform bleaching, and 

• 369 mills that manufacture paper or paperboard products. (EPA 2010b) 

Some integrated pulp and paper mills perform multiple operations (e.g., chemical 

pulping, bleaching, and papermaking; pulping and unbleached papermaking; etc.). Nonintegrated mills may perform either pulping (with or without bleaching), or papermaking (with or 

without bleaching). 

Figure 1. Flow Diagram of the Pulp and Paper Manufacturing Process (Staudt 2010) 
 

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1. Wood Preparation 

Wood is the primary raw material used to manufacture pulp, although other raw materials 

can be used. Wood typically enters a pulp and paper mill as logs or chips and is processed in the 

wood preparation area, referred to as the woodyard. In general, woodyard operations are 

independent of the type of pulping process. If the wood enters the woodyard as logs, a series of 

operations converts the logs into a form suitable for pulping, usually wood chips. Logs are 

transported to the slasher, where they are cut into desired lengths, followed by debarking, 

chipping, chip screening, and conveyance to storage. The chips produced from logs or 

purchased chips are usually stored on-site in large storage piles. (EC/R 2005) 

2. Pulping 

During the pulping process, wood chips are separated into individual cellulose fibers by 

removing the lignin (the intercellular material that cements the cellulose fibers together) from the 

wood. There are five main types of pulping processes: (1) chemical; (2) mechanical; (3) semichemical; (4) recycle; and (5) other (e.g., dissolving, non-wood). Chemical pulping is the most 

common pulping process. 

Chemical (i.e., kraft, soda, and sulfite) pulping involves “cooking” of raw materials (e.g., 

wood chips) using aqueous chemical solutions and elevated temperature and pressure to extract 

pulp fibers. Kraft pulping is by far the most common pulping process used by plants in the U.S. 

for virgin fiber, accounting for more than 80 percent of total U.S. pulp production. 

The kraft pulping process uses an alkaline cooking liquor of sodium hydroxide (NaOH) 

and sodium sulfide (Na2S) to digest the wood, while the similar soda process uses only NaOH. 

This cooking liquor (white liquor) is mixed with the wood chips in a reaction vessel (digester). 

After the wood chips have been “cooked,” the contents of the digester are discharged under 

pressure into a blow tank. As the mass of softened, cooked chips impacts on the tangential entry 

of the blow tank, the chips disintegrate into fibers or “pulp.” The pulp and spent cooking liquor 

(black liquor) are subsequently separated in a series of brown stock washers. (EPA 2001a, EPA 

2008) 

The cooking liquor in the sulfite pulping process is an acidic mixture of sulfurous acid 

(H2SO3) and bisulfite ion (HSO3

-

). In preparing sulfite cooking liquors, cooled sulfur dioxide 

(SO2) gas is absorbed in water containing one of four chemical bases - magnesium (Mg), 

ammonia (NH3), sodium (Na), or calcium (Ca). The sulfite pulping process uses the acid 

solution in the cooking liquor to degrade the lignin bonds between wood fibers. Sulfite pulps 

have less color than kraft pulps and can be bleached more easily, but are not as strong. The 

efficiency and effectiveness of the sulfite process is also dependent on the type of wood furnish 

and the absence of bark. For these reasons, the use of sulfite pulping has declined in comparison 

to kraft pulping over time. (EPA 2001a, EPA 2008) 
 

4 

In mechanical pulping (i.e., refiner mechanical pulping [RMP], thermo-mechanical 

pulping [TMP], chemi-mechanical pulping [CMP]), pulp fibers are separated from the raw 

materials (e.g., round wood, wood chips) by physical energy such as grinding or shredding, 

although some mechanical processes use thermal and/or chemical energy to pretreat raw 

materials. (EPA 2008) 

Semi-chemical pulping uses a combination of chemical and mechanical (i.e., grinding) 

energy to extract pulp fibers. Wood chips first are partially softened in a digester with 

chemicals, steam, and heat. Once chips are softened, mechanical methods complete the pulping 

process. The pulp is washed after digestion to remove cooking liquor chemicals and organic 

compounds dissolved from the wood chips. This virgin pulp is then mixed with 20 to 35 percent 

recovered fiber (e.g., double-lined kraft clippings) or repulped secondary fiber (e.g., old 

corrugated containers) to enhance machinability. The chemical portion (e.g., cooking liquors, 

process equipment) of the pulping process and pulp washing steps are very similar to kraft and 

sulfite processes. At currently operating mills, the chemical portion of the semi-chemical 

pulping process uses either a nonsulfur or neutral sulfite semi-chemical (NSSC) process. The 

nonsulfur process uses either sodium carbonate (Na2CO3) only or mixtures of Na2CO3 and 

NaOH for cooking the wood chips, while the NSSC process uses a sodium-based sulfite cooking 

liquor. (EPA 2001a, EPA 2008) 

In the recycle (i.e., secondary fiber) pulping process, pulp fiber from previously 

manufactured products (e.g., cardboard, office paper) are recovered by hydration and agitation. 

Secondary fibers include any fibrous material that has undergone a manufacturing process and is 

being recycled as the raw material for another manufactured product. Secondary fibers have less 

strength and bonding potential than virgin fibers. The fibrous material is dropped into a large 

tank, or pulper, and mixed by a rotor. The pulper may contain either hot water or pulping 

chemicals to promote dissolution of the paper matrix. Debris and impurities are removed by 

“raggers” (wires that are circulated in the secondary fiber slurry so that debris accumulates on 

the wire) and “junkers” (bucket elevators that collect heavy debris pulled to the side of the pulper 

by centrifugal force). (EPA 2001b, EPA 2008) 

Dissolving kraft and sulfite pulping processes are used to produce highly bleached and 

purified wood pulp suitable for conversion into products such as rayon, viscose, acetate, and 

cellophane. (EPA 2002) 

Non-wood pulping is the production of pulp from fiber sources other than trees. Nonwood fibers used for papermaking include straws and grasses (e.g., flax, rice), bagasse (sugar 

cane), hemp, linen, ramie, kenaf, cotton, and leaf fibers. Pulping of these fibers may be 

performed by mechanical means at high temperatures or using a modified kraft or soda process. 

Non-wood fiber pulp production is not common in the U.S. (EPA 2001b) 

3. Bleaching 

The bleaching process removes color from the pulp (due to residual lignin) by adding 

chemicals to the pulp in varying combinations, depending on the end use of the product. The 

same bleaching processes can be used for any of the pulping process categories. The most 

common bleaching chemicals are chlorine, chlorine dioxide, hydrogen peroxide, oxygen, caustic, 
 

5 

and sodium hypochlorite. Concerns over chlorinated compounds such as dioxins, furans, and 

chloroform have resulted in a shift away from the use of chlorinated compounds in the bleaching 

process. Bleaching chemicals are added to the pulp in stages in the bleaching towers. Spent 

bleaching chemicals are removed between each stage in the washers. Washer effluent is 

collected in the seal tanks and either re-used in other stages as wash water or sent to wastewater 

treatment. (EC/R 2005) 

4. Chemical Recovery 

For economic and environmental reasons, chemical and semi-chemical pulp mills employ 

chemical recovery processes to reclaim spent cooking chemicals from the pulping process. At 

kraft and soda pulp mills, spent cooking liquor, referred to as “weak black liquor,” from the 

brown stock washers is routed to the chemical recovery area at kraft and soda pulp mills. The 

chemical recovery process involves concentrating weak black liquor, combusting organic 

compounds, reducing inorganic compounds, and reconstituting the cooking liquor. The typical 

kraft chemical recovery process consists of the general steps described in the following 

paragraphs. (EPA 2001a, EPA 2008) 

Black liquor concentration. Residual weak black liquor from the pulping process is a 

dilute solution (approximately 12 to 15 percent solids) of wood lignins, organic materials, 

oxidized inorganic compounds (sodium sulfate [Na2SO4], Na2CO3), and white liquor (Na2S and 

NaOH). The weak black liquor is first directed through a series of multiple-effect evaporators 

(MEEs) to increase the solids content to about 50 percent to form “strong black liquor.” The 

strong black liquor from the MEE system is either oxidized in the black liquor oxidation (BLO) 

system if it is further concentrated in a direct contact evaporator (DCE) or routed directly to a 

nondirect contact evaporator (NDCE), also called a concentrator. Oxidation of the black liquor 

prior to evaporation in a DCE reduces emissions of odorous total reduced sulfur (TRS) 

compounds, which are stripped from the black liquor in the DCE when it contacts hot flue gases 

from the recovery furnace. The solids content of the black liquor following the final evaporator/ 

concentrator typically averages 65 to 68 percent. The soda chemical recovery process is similar 

to the kraft process, except that the soda process does not require BLO systems, since it is a 

nonsulfur process that does not result in TRS emissions. 

Recovery furnace. The concentrated black liquor is then sprayed into the recovery 

furnace, where organic compounds are combusted, and the Na2SO4 is reduced to Na2S. The 

black liquor burned in the recovery furnace has a high energy content (5,800 to 6,600 British 

thermal units per pound [Btu/lb] of dry solids), which is recovered as steam for process 

requirements, such as cooking wood chips, heating and evaporating black liquor, preheating 

combustion air, and drying the pulp or paper products. The process steam from the recovery 

furnace is often supplemented with fossil fuel-fired and/or wood-fired power boilers. Particulate 

matter (PM) (primarily Na2SO4) exiting the furnace with the hot flue gases is collected in an 

electrostatic precipitator (ESP) and added to the black liquor to be fired in the recovery furnace. 

Additional makeup Na2SO4, or “saltcake,” may also be added to the black liquor prior to firing. 

Molten inorganic salts, referred to as “smelt,” collect in a char bed at the bottom of the furnace. 

Smelt is drawn off and dissolved in weak wash water in the smelt dissolving tank (SDT) to form 
 

6 

a solution of carbonate salts called “green liquor,” which is primarily Na2S and Na2CO3. Green 

liquor also contains insoluble unburned carbon and inorganic impurities, called dregs, which are 

removed in a series of clarification tanks. 

Causticizing and calcining. Decanted green liquor is transferred to the causticizing area, 

where the Na2CO3 is converted to NaOH by the addition of lime (calcium oxide [CaO]). The 

green liquor is first transferred to a slaker tank, where CaO from the lime kiln reacts with water 

to form calcium hydroxide (Ca(OH)2). From the slaker, liquor flows through a series of agitated 

tanks, referred to as causticizers, that allow the causticizing reaction to go to completion (i.e., 

Ca(OH)2 reacts with Na2CO3 to form NaOH and calcium carbonate [CaCO3]). The causticizing 

product is then routed to the white liquor clarifier, which removes CaCO3 precipitate, referred to 

as “lime mud.” The lime mud is washed in the mud washer to remove the last traces of sodium. 

The mud from the mud washer is then dried and calcined in a lime kiln to produce “reburned” 

lime, which is reintroduced to the slaker. The mud washer filtrate, known as weak wash, is used 

in the SDT to dissolve recovery furnace smelt. The white liquor (NaOH and Na2S) from the 

clarifier is recycled to the digesters in the pulping area of the mill. 

5. Pulp Drying/Papermaking 

After pulping and bleaching, the pulp is processed into the stock used for papermaking. 

At non-integrated mills, market pulp is dried, baled, and then shipped off-site to paper mills. At 

integrated mills, the paper mill uses the pulp manufactured on-site. The processing of pulp at 

integrated mills includes pulp blending specific to the desired paper product desired, dispersion 

in water, beating and refining to add density and strength, and addition of any necessary wet 

additives (to create paper products with special properties or to facilitate the papermaking 

process). Wet additives include resins and waxes for water repellency; fillers such as clays, 

silicas, talc, inorganic/organic dyes for coloring; and certain inorganic chemicals (calcium 

sulfate, zinc sulfide, and titanium dioxide) for improved texture, print quality, opacity, and 

brightness. (EPA 2002) 

The papermaking process is similar for all types of pulp. The pulp is taken from a 

storage chest, screened and refined (if necessary), and placed into a head box of the paper 

machine. From the head box, a slurry of pulp is created using water, usually recycled whitewater 

(drainage from wet pulp stock in pulping and papermaking operations). The pulp slurry is put 

through a paper machine and then passed through a press section, where the whitewater is 

drained and the sheet forming process is begun. The paper sheet is then put through a dryer and 

a series of booths for coating and drying. The finished product then goes through a calender 

(where the sheet is pressed to reduce thickness and smooth the surface) and is wound onto 

storage reels. (EPA 2001b, EPA 2002, EC/R 2005) 

B. Pulp and Paper GHG Emission Sources 

Greenhouse gas emissions from the pulp and paper source category are predominantly 

CO2 with smaller amounts of CH4 and N2O. The GHG emissions associated with the pulp and 

paper mill operations can be attributed to: (1) the combustion of on-site fuels; and (2) non-
 

7 

energy-related emission sources, such as by-product CO2 emissions from the lime kiln chemical 

reactions and CH4 emissions from wastewater treatment. These emissions are emitted directly 

from the pulp and paper plant site. In addition, indirect emissions of GHG are associated with 

the off-site generation of steam and electricity that are purchased by or transferred to the mill. 

Table 1 shows the relative magnitude of nationwide GHG emissions (in million metric tonnes of 

CO2 equivalents per year [mtCO2e/yr] and million short tons of CO2 equivalents per year [ton 

CO2e/yr ) from stationary sources in the pulp and paper manufacturing sector. 

Table 1. Nationwide GHG Emissions from the Pulp and Paper Manufacturing Industry 

Emission Source 

Million metric 

tonnes of CO2e per 

year1

Million short tons of 

CO2e per year 

Direct Emissions 

Direct emissions associated with fuel 

combustion (excluding biomass CO2) 57.7 63.6 

Wastewater treatment plant CH4 releases 0.4 0.4 

Forest products industry landfills2 2.2 2.4 

Use of carbonate make-up chemicals and flue 

gas desulfurization chemicals 0.393

 0.433

Secondary pulp and paper manufacturing 

operations (i.e., converting primary products 

into final products) 

2.5 2.8 

Direct emissions of CO2 from biomass fuel 

combustion (biogenic)4 113 125 

Process-related CO2 including CO2 emitted 

from lime kilns (biogenic)4 unavailable5 unavailable5

Indirect Emissions 

Electricity purchases by pulp and paper mills 25.4 28 

Electricity purchases by secondary 

manufacturing operations (i.e., converting 

primary products into final products) 

8.9 9.8 

Steam purchases unavailable5 unavailable5

1. Except for make-up chemicals, nationwide mtCO2e/yr totals are from National Council for Air and Stream 

Improvement (NCASI) Special Report No. 08-05, The Greenhouse Gas and Carbon Profile of the U.S. Forest 

Products Sector, September 2008; the mtCO2e/yr values are representative of year 2004. 

2. Total includes emissions from wood products industry landfills (but it is expected that pulp and paper landfills are 

the dominant portion of the total). 

3. Nationwide mtCO2e/yr totals associated with carbonate makeup chemical use are from memorandum from Reid 

Miner, NCASI, to Becky Nicholson, RTI International, Calculations Documenting the Greenhouse Gas Emissions 

from the Pulp and Paper Industry, May 21, 2008; the mtCO2e/yr values are representative of years 1995 (CaCO3) 

and 1999 (Na2CO3). 

4. Historically, in voluntary GHG reporting, biogenic emissions at pulp and paper mills were considered “other 

emissions” and were not reported consistently across the industry. EPA’s final GHG mandatory reporting rule 

(MRR) does require reporting of biogenic emissions (40 CFR Part 98). 

5. Information on emissions of process-related CO2 (including CO2 emitted from lime kilns) and indirect emissions 

from steam purchases was not available in the literature reviewed. However, this information is required to be 

reported under subpart AA of EPA’s final GHG MRR (40 CFR Part 98). 
 

8 

 Secondary manufacturing facilities are not engaged in manufacturing primary pulp or 

paper products, but instead convert paper products into other products (e.g., paperboard into 

containers, coated/laminated papers). Some converting operations may operate small fossil fuelfired package boilers. Direct and indirect emissions from secondary manufacturing operations 

are included in Table 1 above, along with emissions from primary manufacturing operations. 

Table 2 lists the stationary direct GHG emission sources found in the pulp and paper 

manufacturing industry. GHG emissions associated with mobile sources and machinery are not 

discussed in this document. Almost all direct GHG emissions from pulp and paper 

manufacturing are the result of fuel combustion, and CO2 emissions from stationary fuel 

combustion represent the majority of GHG emissions from pulp and paper millson-site 

Mill projects might also involve indirect emissions of GHG associated with energy 

consumption by pulp and paper processing equipment, such as new or modified digesters, 

brownstock washers, bleach plant equipment, paper machines, and various other pulp and paper 

mill equipment. Emissions related to energy consumption depend on the type and source of the 

energy (e.g., electrical energy and/or process heat/steam generated on-site or from an outside 

source). 

A number of tools are available to assist with estimating GHG emissions for the pulp and 

paper industry. Notably, EPA’s GHG MRR (40 CFR part 98) contains equations and emission 

factors for stationary combustion (Subpart C), pulp and paper manufacturing (Subpart AA), 

industrial landfills (Subpart TT), and industrial wastewater treatment (Subpart II). The 

calculation procedures in the GHG MRR regulatory text are further described in technical 

support documents (TSDs) related to each subpart. These GHG MRR subparts and TSDs were 

compiled considering various GHG inventory and calculation protocols. Additional resources 

include the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National 

Greenhouse Gas Inventories available at http://www.ipccnggip.iges.or.jp/public/2006gl/index.html and industry-specific guidance for the pulp and paper 

sector entitled Calculation Tools for Estimating Greenhouse Gas Emissions from Pulp and 

Paper Mills, which was developed by the National Council for Air and Stream Improvement 

(NCASI) for the International Council of Forest and Paper Associations (ICFPA) and accepted 

by the World Resources Institute (WRI) and the World Business Council for Sustainable 

Development (WBCSD) (available at http://www.ghgprotocol.org/calculation-tools/pulp-andpaper). It should be noted that these protocols use different emission factors for estimating GHG 

emissions and are broader in scope than the MRR (e.g., include mobile sources). 
 

9 

Table 2. Direct GHG Emission Sources at Pulp, Paper, and Paperboard Facilities 

Emissions Source

Types of pulp and paper mills 

where emissions sources typically 

are located 

Type of GHG 

emissions

Fossil fuel- and/or biomassfired boilers All types of pulp and paper mills fossil CO2, CH4, N2O 

biogenic CO2, CH4,

N2O 

Thermal oxidizers and 

regenerative thermal oxidizers 

(RTOs) 

Kraft pulp mills for NCG control 

and semi-chemical pulp mills (for 

combustion unit control) 

fossil CO2, CH4, N2O 

Direct-fired dryers Gas-fired dryers at some pulp and 

paper mills 

fossil CO2, CH4, N2O 

Combustion turbines All types of pulp and paper mills fossil CO2, CH4, N2O 

Chemical recovery furnaces – 

kraft & soda 

Kraft and soda pulp mills fossil CO2, CH4, N2O 

biogenic CO2, CH4,

N2O 

Chemical recovery furnaces – 

sulfite 

Sulfite pulp mills fossil CO2, CH4, N2O 

biogenic CO2, CH4,

N2O 

Chemical recovery combustion 

units – stand-alone semichemical 

Stand-alone semi-chemical pulp 

mills 

fossil CO2, CH4, N2O 

biogenic CO2, CH4,

N2O 

Kraft and soda lime kilns Kraft and soda pulp mills fossil CO2, CH4, N2O 

process biogenic CO2

Makeup chemicals (CaCO3, 

Na2CO3)

Kraft and soda pulp mills process CO2

Flue gas desulfurization systems Mills that operate coal-fired boilers 

required to limit SO2 emissions 

process CO2

Anaerobic wastewater treatment Chemical pulp mills (kraft, mostly) biogenic CO2, CH4

On-site landfills All types of pulp and paper mills biogenic CO2, CH4

 

C. Pulp and Paper Energy Use 

 The pulp and paper manufacturing process is highly energy intensive. Natural gas, fuel 

oil, biomass-based materials, purchased electricity, and coal are the major energy-related GHG 

emission sources for U.S. pulp and paper mills. When biomass-derived GHG emissions are not 

counted, the remaining four energy sources accounted for an estimated 80 percent or more of the 

industry’s energy related GHG emissions in 2002. Thus, a primary option to reduce GHG 

emissions is to improve energy efficiency. In 2002, the pulp and paper manufacturing industry 

consumed over 2,200 trillion Btu (TBtu), which accounted for around 14 percent of all fuel 

consumed by the U.S. manufacturing sector. (Kramer 2009) 

 Two biomass by-products of the pulp and paper manufacturing process, black liquor and 

hog fuel (i.e., wood and bark), meet over half of the industry’s annual energy requirements. The 

American Forest and Paper Association (AF&PA) estimates that biomass comprises 64 percent 
 

10 

of total fuel use by AF&PA members’ pulp and paper facilities. (AF&PA 2008) The use of these 

by-products as fuels significantly reduces the industry’s dependence on purchased fossil fuels 

and electricity, with the added benefits of reduced raw material costs (i.e., avoided pulping 

chemical purchases) and reduced waste generation. Natural gas and coal comprise the majority 

of the remaining fuel used by the industry. (Kramer 2009) Incidental amounts of pulping vent 

gases and pulping by-products (tall oil and turpentine) are also used, as discussed further in 

Section II.B. 

 Steam is the largest end use of energy in the pulp and paper industry, with more than 

1,026 TBtu used in 2002. The next largest end use of energy is electricity, with approximately 

339 TBtu of electricity (purchased and self-generated) consumed in 2002. Therefore, energy 

efficiency initiatives that are targeted at reducing steam system losses and improving the 

efficiency of process steam-using equipment are likely to reduce energy use at pulp and paper 

mills. (Kramer 2009) 

 For many of the control techniques listed in this document, CO2 emission reductions are 

not explicitly provided. Energy efficiency improvements lead to reduced fuel consumption or 

reduced electricity demand. Thus, where CO2 emission reductions are not provided, these 

reductions can be calculated from the reduction of fuel usage at the boiler or other combustion 

device. In addition, emission reductions that result from reduced electricity usage can be 

calculated from the reduced amount of fuel consumed at the power plant (if fuel combustion 

rather than waste heat is used for this purpose). 
 

11 

II. Control Measures and Energy Efficiency Improvements for Direct 

GHG Emission Sources 

 The control measures and energy efficiency options that are currently available for pulp 

and paper mill processes are listed in Table 3 and discussed in further detail in the sections 

below. 

Table 3. List of Control Measures and Energy Efficiency Options 

Boilers

Burner replacement Boiler maintenance 

Boiler process control Condensate return 

Reduction of flue gas quantities Minimizing boiler blow down 

Reduction of excess air Blow down steam recovery 

Improved boiler insulation Flue gas heat recovery 

Chemical Recovery Furnaces

Boiler control measures and energy efficiency options 

(see above) 

Recovery furnace deposition monitoring 

Black liquor solids concentration Quaternary air injection 

Improved composite tubes for recovery furnaces 

Turbines

Boiler/steam turbine CHP Replacement of pressure reducing valves 

Simple cycle gas turbine CHP Steam injected gas turbines 

Combined cycle CHP Regular performance monitoring and maintenance 

Natural-Gas Fired Dryers and Thermal Oxidizers

Energy efficiency measures Use of thermal oxidizers employing heat recovery (e.g., 

regenerative or recuperative thermal oxidizers) 

Selection of technologies requiring less fuel 

consumption 

Proper design and attention to monitoring and 

maintenance 

Use of existing combustion processes (e.g., power 

boilers or lime kilns) over a separate thermal oxidizer 

Kraft and Soda Lime Kilns 

Piping of stack gas to adjacent PCC plant Lime kiln modifications (e.g., high-efficiency filters, 

higher efficiency refractory insulation brick) 

Lime kiln oxygen enrichment Lime kiln ESP 

Makeup Chemicals 

Practices to ensure good chemical recovery rates in the 

pulping and chemical recovery processes 

Addition of Na and Ca in forms that do not contain 

carbon (e.g., Na2SO4, NaOH, CaO) 

Flue Gas Desulfurization (FGD) Systems 

Use of sorbents other than carbonates Use of lower-emitting FGD systems 

Wastewater Treatment 

Use of mechanical clarifiers or aerobic biological 

treatment systems (instead of anaerobic treatment 

systems) 

Minimization of potential for formation of anaerobic 

zones in wastewater treatment systems (e.g., through 

placement of aerators where practical) 

On-site Landfills 

Dewatering and burning of wastewater treatment plant 

residuals in on-site boiler 

Capture and control of landfill gas by burning it in onsite combustion device (e.g., boilers) for energy 

recovery and solid waste management 
 

12 

A. Power Boilers, Chemical Recovery Furnaces, and Turbines 

 The U.S. pulp and paper industry is the largest self-generator of electricity in the U.S. 

manufacturing sector, with pulp and paper mills using on-site power boilers to generate steam, 

electricity, and process heat needed for mill processes. Recovery furnaces and other types of 

chemical recovery combustion units—used at pulp mills primarily to recover pulping process 

chemicals—also produce steam, electricity, and process heat for the mill. The need to keep up 

with significant mill demands for process steam and electricity, the high annual operating hours, 

and the presence of on-site generated fuels (i.e., wood waste and black liquor) has made 

combined heat and power (CHP) systems an operationally and financially attractive option for 

many mills around the country. 

 Major industrial CHP “prime mover” technologies include steam turbines, gas turbines, 

reciprocating engines, and fuel cells. Of these, steam and gas turbines dominate in U.S. pulp and 

paper mill applications. Traditional boilers, recovery furnaces, and steam turbine systems are by 

far the most common, and account for nearly 70 percent of current installed CHP capacity at 

pulp and paper mills. Around half of these boiler-based systems are fired by on-site fuels (i.e., 

by black liquor and hog fuel), and the other half are fired by purchased fuels (i.e., by coal, 

natural gas, and other fuels). These systems generally produce much more steam than electricity 

and, as a result, do not typically generate enough electricity to meet a mill’s total electricity 

demand. 

 CHP systems based on natural gas-fired combustion turbines account for around 

30 percent of the total installed CHP capacity at pulp and paper mills. Roughly two-thirds of 

these turbine-based systems use combined cycles, which augment a primary gas turbine system 

with a secondary, steam-based turbine system for improved power generation. Combustion 

turbine systems produce more electricity per unit of heat than boiler and steam turbine systems, 

and can often meet a mill’s total electricity demand. From a fuels perspective, around one-third 

of the current CHP capacity in the U.S. pulp and paper industry is fired by biomass-based energy 

sources. 

1. Control Measures and Energy Efficiency Options for Boilers 

 Control technologies, energy efficiency measures, and fuel switching options for power 

boilers are presented in a separate related document of this series titled, Available and Emerging 

Technologies for the Control of Greenhouse Gas Emissions from Industrial, Commercial, and 

Institutional Boilers. Several energy efficiency measures for boilers presented in that document 

that could apply most effectively for boilers at pulp and paper mills were also reported in the 

document Energy Efficiency Improvement and Cost Saving Opportunities for the Pulp and Paper 

Industry. (Kramer 2009)1 Those boiler energy efficiency measures are listed in Table 3 above 

and discussed further in the paragraphs below. The boiler energy efficiency measures presented 

below focus primarily on improved process control, reduced heat loss, and improved heat 

recovery. Additional energy efficiency measures related to stream distribution systems and 

 

1

 Kramer 2009 provides example costs for various energy efficiency measures. However, it is noted that estimates 

of initial installation costs, annual operating costs, and total emissions reductions would be specific to the emission 

source and were not available for inclusion in this document. 
 

13 

reduced electrical consumption that can result in small incremental reductions in boiler demand 

are discussed in Section III of this document. It is expected that new state-of-the-art boiler 

designs would incorporate many of the energy efficiency measures discussed below. 

Burner replacement. According to a study conducted for the U.S. Department of Energy 

(DOE), roughly half of the U.S. industrial boiler population (across all sectors) is over 40 years 

old. Replacing old burners with more efficient modern burners can lead to significant energy 

savings. Energy and cost savings vary widely based on the condition and efficiency of the 

burners being replaced. In one example from the pulp and paper industry, replacing circular oil 

burners with more efficient parallel throat burners with racer type atomizers had a payback 

period of approximately one year. The U.S. DOE estimates that upgrading burners to more 

efficient models or replacing worn burners can reduce the boiler fuel use of U.S. pulp and paper 

mills by around 2.4 percent, with a payback period of around 19 months. (Kramer 2009) 

Boiler process control. Flue gas monitors maintain optimum flame temperature and 

monitor carbon monoxide (CO), oxygen, and smoke. The oxygen content of the exhaust gas is a 

combination of excess air (which is deliberately introduced to improve safety or reduce 

emissions) and air infiltration. By combining an oxygen monitor with an intake airflow monitor, 

it is possible to detect even small leaks. A small 1 percent air infiltration will result in 20 percent 

higher oxygen readings. A higher CO or smoke content in the exhaust gas is a sign that there is 

insufficient air to complete fuel burning. Using a combination of CO and oxygen readings, it is 

possible to optimize the fuel/air mixture for high flame temperature (and thus the best energy 

efficiency) and lower air pollutant emissions. (Kramer 2009) 

 Typically, this measure is financially attractive only for relatively large boilers (e.g., 

250,000 pounds per hour [lb/hr] of steam), because smaller boilers often will not make up the 

initial capital cost as easily. Several case studies indicate that the average payback period for 

this measure is 1.7 years or less. (Kramer 2009) 

 One case study showed that installing a control system to measure, monitor, and control 

oxygen and CO levels on coal-fired boilers was estimated to save nearly $475,000 in annual 

energy costs; at an investment cost of $200,000, the payback period was less than six months. 

(Kramer 2009) Another estimate suggests capital costs around $0.031 per million Btu (MMBtu) 

(2008 dollars) for this measure, with a fuel savings of 2.8 percent. (Staudt 2010) 

Reduction of flue gas quantities. Often, excessive flue gas results from leaks in the boiler 

and/or in the flue. These leaks can reduce the heat transferred to the steam and increase pumping 

requirements. However, such leaks are often easily repaired, saving 2 to 5 percent of the energy 

formerly used by the boiler. This measure differs from flue gas monitoring in that it consists of a 

periodic repair based on visual inspection. The savings from this measure and from flue gas 

monitoring are not cumulative, as they both address the same losses. (Kramer 2009) 

Reduction of excess air. Boilers must be fired with excess air to ensure complete 

combustion and to reduce the presence of CO in the unburned fuel in exhaust gases. When too 

much excess air is used to burn fuel, energy is wasted because excessive heat is transferred to the 

air rather than to the steam. Air slightly in excess of the ideal stochiometric fuel-to-air ratio is 

required for safety and to reduce emissions of nitrogen oxides (NOX); approximately 15 percent 
 

14 

excess air (around 3 percent excess oxygen) is generally adequate. Most industrial boilers 

already operate at 15 percent excess air or lower; thus, this measure may not be widely 

applicable. However, if a boiler is using too much excess air, numerous industrial case studies 

indicate that the payback period for this measure is less than one year. (Kramer 2009) 

 Examples of improvements to reduce excess air include changing automatic oxygen 

control set points, periodic tuning of single set point control mechanisms, installing automatic 

flue gas monitoring and control, fixing broken baffles, and repairing air leaks into the boiler. 

The U.S. DOE estimates that U.S. pulp and paper plants could reduce boiler fuel use by around 

2.3 percent through application of this measure (it was assumed that this measure would be 

feasible at around one-third of U.S. pulp and paper mills). The estimated average payback 

period for this measure was 5 months. (Kramer 2009) 

 One case study showed that combustion tuning of a combination fuel-fired boiler 

(typically green wood and bark) reduced flue gas oxygen concentrations from the 8 to 12 percent 

range to the 6 to 7 percent range. The savings in green wood was reported to be around $70,000 

per year. Similar benefits were predicted for adjusting the boiler oxygen trim controls on another 

mill to lower the oxygen levels to between 2.5 and 3 percent; boiler efficiency improvements 

would save 15,500 MMBtu per year at an annual cost savings of around $118,000. (Kramer 

2009) 

Improved boiler insulation. New materials insulate better and have a lower heat capacity. 

Savings ranging from 6 to 26 percent can be achieved if this improved insulation is combined 

with improved heater circuit controls. This improved control is required to maintain the output 

temperature range of the old firebrick system. As a result of the ceramic fiber’s lower heat 

capacity, the output temperature is more vulnerable to temperature fluctuations in the heating 

elements. The shell losses of a well-maintained boiler should be less than 1 percent. (Kramer 

2009) 

Boiler maintenance. A simple maintenance program to ensure that all components of a 

boiler are operating at peak performance can result in substantial fuel savings (6.5 percent) with 

negligible capital cost investment. (Staudt 2010) In the absence of a good maintenance system, 

burners and condensate return systems can wear or get out of adjustment. These factors can end 

up costing a steam system up to 30 percent of initial efficiency over two to three years. On 

average, the energy savings associated with improved boiler maintenance are estimated at 10 

percent. Improved maintenance may also reduce the emissions of criteria air pollutants. 

(Kramer 2009) 

 Fouling on the fire side of boiler tubes or scaling on the water side of boilers should also 

be controlled. Fouling and scaling are more of a problem with coal-fed boilers than natural gasor oil-fed boilers. (Boilers that burn solid fuels like coal should be checked more often, as they 

have a higher fouling tendency than liquid fuel boilers do.) Tests reported by the Canadian 

Industry Program for Energy Conservation (CIPEC) show that a fire side soot layer of 

0.03 inches (0.8 millimeters [mm]) reduces heat transfer by 9.5 percent, while a 0.18-inch (4.5-

mm) soot layer reduces heat transfer by 69 percent. For water side scaling, 0.04 inches (1 mm) 

of buildup can increase fuel consumption by 2 percent. (Kramer 2009) 
 

15 

Condensate return. For indirect uses of steam, returning hot condensate to boilers for reuse saves energy and reduces the need for treated boiler feed water. Typically, fresh feed water 

must be treated to remove solids that might accumulate in the boiler; however, returning 

condensate to a boiler can substantially reduce the amount of purchased chemical required to 

accomplish this treatment. The fact that this measure can save substantial energy costs and 

purchased chemicals costs often makes building a return piping system attractive. The U.S. 

DOE estimates that this measure can lead to a 1.5 percent reduction in boiler fuel use at U.S. 

pulp and paper mills, at an average payback period of around 15 months. (Kramer 2009) 

In a specific example, the U.S. DOE reports that a large specialty paper plant reduced its 

boiler makeup water rate from about 35 percent of total steam production to less than 20 percent 

by returning additional condensate; annual savings were around $300,000 (2004 dollars). 

(Kramer 2009) Another estimate, provided to the U.S. EPA, indicates a capital cost of 

$0.292/MMBtu (2008 dollars) and a fuel savings of 13.8 percent for this measure. (Staudt 2010) 

Minimizing boiler blow down. Boiler blow down is important for maintaining proper 

steam system water properties and must be done periodically to minimize boiler deposit 

formation. However, excessive blow down will waste energy, as well as water and chemicals. 

The optimum blow down rate depends on a number of factors, including the type of boiler and its 

water treatment requirements, but typically ranges from 4 to 8 percent of the boiler feed water 

flow rate. Automatic blow down systems can be installed to optimize blow down rates. Case 

studies from the pulp and paper industry suggest that automatic blow down systems can have a 

payback period of just six months. (Kramer 2009) 

 The U.S. DOE estimates that around 20 percent of U.S. pulp and paper mills could 

improve blow down practices, which would lead to annual boiler fuel savings of around 

1.1 percent. (Kramer 2009) 

Blow down steam recovery. Boiler blow down is important for maintaining proper steam 

system water properties. However, blow down can result in significant thermal losses if the 

steam is not recovered for beneficial use. Blow down steam is typically low grade, but can be 

used for space heating and feed water preheating. In addition to energy savings, blow down 

steam recovery may reduce the potential for corrosion damage in steam system piping. 

Examples of blow down steam recovery in the pulp and paper industry suggest a payback period 

of around 12 to 18 months for this measure. (Kramer 2009) 

 The U.S. DOE estimates that the installation of continuous blow down heat recovery 

systems is feasible at around 20 percent of U.S. pulp and paper mills and would reduce boiler 

fuel use by around 1.2 percent. (Kramer 2009) 

 In one case study, an existing boiler blow down system was modified by installing a 

plate-and-tube heat exchanger and associated piping to recover energy from the mill’s 

continuous blow downstream from the boiler blow down flash tank. The project resulted in 

annual energy savings of 14,000 MMBtu, with annual fuel cost savings of over $30,000 (2002 

dollars). The period of payback for this project was about six months. In a second case study, a 

plant-wide assessment estimated that the pursuit of blow down heat recovery (as opposed to the 

current practice of venting blow down to atmosphere) could save the mill around $370,000 per 

year (2006 dollars). In a third case study, it was estimated that a significant amount of additional 
 

16 

thermal energy could be recovered from the liquid blow down rejected from the flash vessel. If a 

second stage of blow down energy recovery were installed on the remaining boilers, additional 

blow down energy recovery savings of $100,000 per year were projected (2006 dollars). 

(Kramer 2009) Another estimate, provided to the U.S. EPA, indicates a capital cost of 

$0.061/MMBtu (2008 dollars) and fuel savings of 1.2 percent for this measure. (Staudt 2010) 

Flue gas heat recovery. Heat recovery from flue gas is often the best opportunity for heat 

recovery in steam systems. Heat from flue gas can be used to preheat boiler feed water in an 

economizer. While this measure is fairly common in large boilers, there is often still room for 

more heat recovery. The limiting factor for flue gas heat recovery is that one must ensure that the 

economizer wall temperature does not drop below the dew point of acids contained in the flue 

gas (such as sulfuric acid in sulfur-containing fossil fuels). Traditionally, this has been done by 

keeping the flue gases exiting the economizer at a temperature significantly above the acid dew 

point. In fact, the economizer wall temperature is much more dependent on feed water 

temperature than on flue gas temperature because of the high heat transfer coefficient of water. 

As a result, it makes more sense to preheat feed water to close to the acid dew point before it 

enters the economizer. This approach allows the economizer to be designed so that exiting flue 

gas is just above the acid dew point. (Kramer 2009) 

 Typically, one percent of fuel use is saved for every 45°F reduction in exhaust gas 

temperature. A conventional economizer would result in savings of 2 to 4 percent, while a 

condensing economizer could result in energy savings of 5 to 8 percent. However, the use of 

condensing economizers is limited to boilers using clean fuels due to the risk of corrosion. 

(Kramer 2009) 

 The U.S. DOE estimates that the installation of boiler feedwater economizers is feasible 

at around 19 percent of U.S. pulp and paper mills and would reduce boiler fuel use by around 3.5 

percent. (Kramer 2009) An estimate for flue gas heat recovery provided to the U.S. EPA 

indicates a capital cost of $0.054/MMBtu (2008 dollars) and 1.3 percent fuel savings. (Staudt 

2010) 

2. Control Measures and Energy Efficiency Options for Chemical Recovery Furnaces 

and Combustion Units 

Concentrated spent pulping liquors generated as a byproduct of chemical pulping are 

burned in chemical recovery furnaces (or other types of chemical recovery combustion units) to 

produce steam for use in facility processes and to recover chemicals for re-use in the pulping 

process. Carbon dioxide emissions associated with combustion of spent pulping liquor (e.g., 

black liquor at kraft mills) in chemical recovery furnaces are biomass-derived CO2 because the 

carbon originates from the wood or other cellulosic materials. The carbon in the spent pulping 

liquor exits the recovery furnace in two forms: (1) as CO2 emissions from the recovery furnace 

stack, and (2) as carbonates in the smelt flowing from the bottom of the recovery furnace (which 

eventually makes its way to the lime kiln). (EPA 2009c) 

Fuel switching is generally not an option of significance for recovery furnaces and other 

chemical recovery combustion units because spent pulping liquor comprises most of the heat 

input. Small amounts of supplemental fossil fuels (e.g., oil or natural gas) are also fired in the 
 

17 

furnace, usually during startup or shutdown conditions. Therefore, chemical recovery furnaces 

are sources of both biogenic and fossil fuel-based CO2 (which must be accounted for separately 

for the federal GHG reporting rule) as well as small amounts of CH4 and N2O. (EPA 2009c) 

Many of the boiler control technologies and/or energy efficiency measures noted in the 

previous section for power boilers will also apply for chemical recovery furnaces and 

combustion units. Additional control technologies, energy efficiency measures, and fuel 

switching options for power boilers are presented in a separate related document entitled, 

Available and Emerging Technologies for the Control of Greenhouse Gas Emissions from 

Industrial, Commercial, and Institutional Boilers. Efficiency measures specific to recovery 

furnaces are summarized in the following sections. 

Black liquor solids concentration. Black liquor concentrators are designed to increase the 

solids content of black liquor prior to combustion in a recovery furnace. Increased solids content 

means less water must be evaporated in the recovery furnace, which can increase the efficiency 

of steam generation substantially. There are two primary types in use today: submerged tube 

concentrators and falling film concentrators. (Kramer 2009) 

In a submerged tube concentrator, black liquor is circulated in submerged tubes, where it 

is heated but not evaporated; the liquor is then flashed to the concentrator vapor space, causing 

evaporation. One study estimated that, for a 1,000 ton per day pulp mill, increasing the solids 

content in black liquor from 66 to 80 percent would lead to fuel savings of 30 MMBtu per hour 

(hr), or about $550,000. Capital costs of the high solids concentrator would include concentrator 

bodies, piping for liquor and steam supplies, and pumps. (Kramer 2009) 

A tube-type falling film evaporator effect operates almost exactly the same way as a more 

traditional rising film effect, except that the black liquor flow is reversed. The falling film effect 

is more resistant to fouling because the liquor is flowing faster and the bubbles flow in the 

opposite direction of the liquor. This resistance to fouling allows the evaporator to produce 

black liquor with considerably higher solids content (up to 70 percent solids, rather than the 

traditional 50 percent), thus eliminating the need for a final concentrator. One study estimated a 

steam savings of 0.76 MMBtu per ton of pulp with this type of concentrator. (Kramer 2009) 

According to another study, a 900 ton per day pulp and paper mill which installed a 

liquor concentrator increased its solids content from 73 to 80 percent and reduced annual energy 

usage by about 110,000 MMBtu. Cost savings for the mill were about $900,000 per year, with 

an estimated payback period of 4 years. (Kramer 2009) 

Improved composite tubes for recovery furnaces. Recovery furnaces consist of tubes that 

circulate pressurized water to permit steam generation. These tubes are normally made out of 

carbon steel, but severe corrosion thinning and occasional tube failure has led to the research and 

development of more advanced tube alloys, including new weld overlay and co-extruded tubing 

alloys. Replacing carbon steel tubes in the recovery furnace with these composite alloy tubes 

allows the use of black liquor with higher dry solids content, which increases the thermal 

efficiency of the recovery furnace and decreases the number of furnace shutdowns. Improved 

composite tubes have been installed in more than 18 kraft recovery furnaces in the U.S., leading 

to a cumulative energy savings of 4.6 TBtu since their commercialization in 1996. (Kramer 

2009) 
 

18 

Recovery furnace deposition monitoring. Better control of deposits on heat transfer 

surfaces in recovery furnaces can lead to higher operating efficiencies, reduced downtime (by 

avoiding plugging), and more predictable shutdown schedules. A handheld infrared inspection 

system is currently available that can provide early detection of defective fixtures (tube leaks or 

damaged soot blower) and slag formation, preventing impact damage and enabling cleaning 

before deposits harden. The system can reportedly provide clear images in highly particle-laden 

boiler interiors and enable inspection anywhere in the combustion chamber. As of 2005, 69 units 

were in use in the U.S., generating 1.4 TBtu in energy savings since their introduction in 2002 

(energy savings are attributable to reduced soot blower steam use). (Kramer 2009) 

Quaternary air injection. Most recovery furnaces in the U.S. have three stages of air 

injection but use the third stage in a limited fashion. Fully using the third stage and adding a 

fourth air injection port can reduce carry over and tube fouling, thereby reducing the frequency 

of recovery furnace washing, which will lead to energy savings, because boiler shutdowns and 

reheat can be reduced. One estimate indicated each boiler reheat cycle will consume around 10 

MMBtu at a cost of around $50,000. Capital costs for this measure are estimated at $300,000 to 

$500,000. (Kramer 2009) 

3. Energy Efficiency Associated with CHP Systems 

 

The benefits of CHP are significant and well-documented. Pulp and paper mills benefit 

from improved power quality and reliability, greater energy cost stability, and, possibly, higher 

revenues from the export of excess electrical power to the grid. CHP systems are significantly 

more efficient than standard power plants, because they take advantage of waste heat that is 

usually lost in central power generating systems and also reduce electricity transmission losses. 

Thus, society also benefits from CHP in the form of reduced grid demand, reduced air pollution, 

and reduced GHG emissions. 

 CHP systems in the pulp and paper industry are typically designed with a mill’s thermal 

energy demand in mind, including the supply steam temperatures and pressures that are required 

by key mill processes. Thus, electrical power generation is a secondary benefit to providing 

efficient and reliable process steam to the mill. Many mills will import supplementary electricity 

from the grid as needed, but best practice mills may be able to meet all on-site electrical power 

demand through self generation. CHP systems can also be used to directly drive mechanical 

equipment such as pumps and air compressors. 

 Despite the benefits of CHP systems, and their widespread use in the U.S. pulp and paper 

industry (currently 225 of the 386 mills have some form of CHP system in place, representing 

approximately 12,000 megawatts (MW) of electric generating capacity (ICF 2010)), much 

potential for CHP remains. Examples of CHP technology include power boilers and chemical 

recovery furnaces (e.g., at kraft pulp mills). There are significant remaining opportunities to add 

CHP capacity, based on evaluation of steam requirements met by boilers and by CHP in the 

paper industry. In addition, there are opportunities to repower existing CHP plants, making them 

larger and more efficient. If natural gas is available, existing steam turbine CHP systems can be 

replaced by newer, more efficient combustion turbines; existing simple cycle combustion turbine 
 

19 

CHP systems can be converted to combined cycle operation by adding steam turbines for 

additional power. 

There are a number of barriers that may account for this untapped potential. These 

barriers include high capital investment costs, the complexity of the CHP project development 

process, complexities in permitting, and knowledge barriers related to technology selection, 

operation, and performance characterization. However, there are a number of resources 

available to help U.S. pulp and paper mills overcome such barriers. For example, the U.S. 

EPA’s Combined Heat and Power Partnership provides information on CHP technology basics, 

guidance for streamlining CHP projects, information on federal and state policies and incentives, 

CHP feasibility assessment tools, and a database of funding resources. The U.S. DOE’s CHP 

Regional Application Centers provides educational assistance and project-specific support in 

eight different U.S. regions, including project development and screening tools; technical 

assistance and training; information regarding issues related to permitting, utilities, and siting; 

and case studies. 

 The configuration, economics, and performance of a CHP system will depend highly on 

site-specific conditions. However, a common goal is to choose a CHP system that will provide 

the greatest combined thermal and electrical energy efficiency at the lowest life-cycle cost for 

meeting a given thermal energy requirement. To do so, detailed, site-specific energy and cost 

analyses are required. Mill personnel are encouraged to elicit technical support (e.g., from the 

U.S. EPA and DOE resources mentioned in the previous paragraph) when conducting such 

analyses. 

 There are a variety of applications and configurations of CHP systems. As such, CHP 

systems represent a complex topic. In order to be concise, this section discusses only a few 

measures related to the efficient application of CHP to pulp and paper mills. 

Boiler/steam turbine CHP. The most prevalent form of co-generation in the pulp and 

paper industry is based on steam turbine generators fed by a mill’s power boilers and recovery 

furnaces. An estimated 199 mills currently employ steam turbine CHP, representing 8,400 MW 

of generating capacity (ICF 2010) fueled predominantly by black liquor recovery, coal, and 

wood waste. In these CHP systems, the boilers produce high-pressure steam that runs through 

back-pressure or extraction steam turbines to produce power and exhaust steam at lower pressure 

for process use. The electric-to-thermal (E/T) output ratio for this type of CHP system ranges 

from 0.05 to 0.15; that is, 5 to 15 percent of the energy output from a boiler/steam turbine CHP 

system is in the form of electricity, and the remaining 85 to 95 percent is steam. 

Simple cycle gas turbine CHP. For increased power production, a combustion or gas 

turbine with a heat recovery steam generator (HRSG) can be used, with the existing boilers 

providing supplemental or back-up steam when the CHP system is not operating. Gas turbine 

CHP operating on gaseous fuels such as natural gas or landfill gas offer the advantages of 

reduced emissions, faster start-up times, low noise, and improved electrical generation efficiency 

at full loads. Twenty-six mills currently employ this type of CHP system, generating over 1,000 

MW of power. Combustion turbine CHP may make economic sense at mills with high electric 

loads and access to moderately priced natural gas. This type of system has an E/T ratio of 0.45 

to 1.05 (much more power is produced per pound of process steam compared to boiler/steam 

turbine CHP), with the higher E/T ratios coming from larger turbines with higher electric 
 

20 

generating efficiencies. Additional steam can be generated from this type of system through the 

use of duct burners in the HRSG. This additional steam is generated very efficiently (87 to 90 

percent higher heating value [HHV]) because the turbine exhaust which provides the combustion 

air is effectively preheated to a high temperature level. This type of system is typically used 

where electric and thermal demands are high and either natural gas or distillate oil is already 

used for an existing boiler or fuel switching to a gas CHP system makes economic sense. 

Combined cycle CHP. Additional power can be produced through the use of a combined 

cycle CHP system. In combined cycles, the pressure of the steam produced in the gas turbine 

HRSG is increased, and the steam is run through a back-pressure or extraction steam turbine, 

producing additional power before being used in the mill processes. Twenty-six mills currently 

employ this type of CHP system, generating 2,660 MW of power. (ICF 2010) Combined cycle 

systems can have E/T ratios of around 1.0 to 2.0 and are normally used by larger plants with very 

high power requirements. An important limitation of combined cycle systems is that part-load 

operation will reduce overall system efficiency. (Kramer 2009) 

 In 1999, one pulp and paper initiated a project to install a gas turbine combined cycle 

system. A key goal of the project was to ensure the financial viability of the mill in the face of 

sharply rising electricity prices. Prior to the project, the mill generated 20 MW of electrical 

power based on two boilers fired by hog fuel, sludge, and natural gas. On average, the mill 

purchased 84 MW of power. At a cost of $75 million, the mill installed a 92 MW gas-fired 

power plant consisting of two natural gas-fired turbines with HRSGs to provide steam for 

additional power and process applications. The system allowed the mill to increase the power 

output of its existing steam turbines, which led to a total generating capacity of 130 MW. The 

reported availability of the gas turbines was over 95 percent. The mill is now able to sell 20 to 

25 MW of excess power on the wholesale market. (Kramer 2009) 

Replacement of pressure reduction valves. In many existing paper mill steam systems, 

high-pressure steam produced by boilers is supplied to the plant steam header and reduced in 

pressure through a pressure reduction valve (PRV) before being used in the various mills’ 

processes. A PRV does not recover the energy embodied in the pressure drop. However, this 

energy could be recovered in the form of mechanical or electrical power for beneficial use in a 

mill. For example, a mechanical steam drive turbine can be used in place of a PRV to replace an 

electric motor-based drive, such as the drive for boiler feed water pumps. (Kramer 2009)

 To generate electrical power, a PRV could be replaced by a small back-pressure steam 

turbine. Several manufacturers produce and/or sell these turbine sets, such as Turbosteam 

(previously owned by Trigen) and Dresser-Rand. The potential for application will depend on 

mill-specific conditions; however, applications of this technology have been commercially 

demonstrated for various installations. The investments of a typical turbine set are estimated at 

$600 killowatt-electric (kWe), with operation and maintenance costs at $0.011 per kilowatt-hour 

(kWh). (Kramer 2009) 

 In an energy efficiency assessment of one facility, the installation of a steam turbine to 

replace a PRV was identified as a project that could save 3.1 gigawatt-hours (GWh) of electricity 

per year. Capital costs for the project were estimated at $604,034, and avoided first year energy 

expenses were estimated at $163,999. (Kramer 2009) 
 

21 

Steam injected gas (STIG) turbines. Steam injected gas (STIG) turbines are a variation 

of gas turbine CHP that boost power production and reduce NOX emissions by injecting steam 

into the combustion chamber of the turbine. A reported advantage of a STIG turbine is that partload performance deteriorates at a slower rate with reduced load compared to a combined cycle 

CHP system. In a combined cycle system, when gas turbine efficiency drops under partial 

loading, more waste heat is supplied to the steam turbine. While this increases steam turbine 

electrical output, the overall power efficiency of the combined cycle system is reduced. For 

mills that experience fluctuations in steam demand, a STIG turbine can improve electrical power 

generation during the periods of partial turbine loading. (Kramer 2009)

 The size of a typical STIG turbine starts around 5 megawatts-electric (MWe), and is 

currently scaled up to sizes of 125 MW. STIG turbines have been installed at over 50 sites 

worldwide and are found in various industries and applications, especially in Japan and Europe. 

Energy savings and payback period will depend on the local circumstances (e.g. thermal demand 

patterns and power sales conditions). However, no pulp and paper industry case studies could be 

found. (Kramer 2009) 

Performance and Maintenance. Like other critical mill processes, CHP systems require 

regular performance monitoring and maintenance to ensure that they are operating in the most 

energy efficient manner possible. (Kramer 2009) 

 The efficiency of the steam turbine is determined by the inlet steam pressure and 

temperature as well as the outlet pressure. The higher the ratio of the steam inlet pressure to the 

steam exit pressure and the higher the steam inlet temperature, the more power it will produce 

per unit of steam mass flow. As a result, plant operators should make sure that the steam inlet 

temperature and pressure are as close to the optimum values for a given turbine design as 

possible. For example, an 18°F decrease in steam inlet temperature will reduce the efficiency of 

the steam turbine by 1.1 percent. Additionally, operators should also monitor and maintain the 

outlet pressure of back-pressure turbines, as efficiency losses will occur if this pressure gets too 

high. Monitoring and maintaining proper feed water and steam chemistry are also critical for 

avoiding corrosion and erosion problems. (Kramer 2009) 

 A key variable governing the efficiency of gas turbines is the inlet air temperature. 

Power and efficiency are increased at low air inlet temperatures, whereas high inlet air 

temperatures lead to power and efficiency reductions. Power can be restored with inlet air 

cooling. Options to consider for cooling inlet air include refrigeration cooling (in which a 

compressor or absorption chiller cools inlet air via a heat exchanger and cooling fluid) and 

evaporative cooling (which uses a spray of water directly into the inlet air stream). Each cooling 

option has advantages and drawbacks, however, which should be explored to determine the 

feasibility of this measure on a site-specific basis. (Kramer 2009) 

 Gas turbines that operate on a cyclic basis, or above rated capacity for extended periods, 

will require greater maintenance compared to gas turbines that are steadily operated at the rated 

load. Reportedly, cycling every hour triples maintenance costs versus a turbine that operates for 

intervals of 1,000 hours or more. Thus, ensuring consistency in steam demand is also an 

important operating consideration. (Kramer 2009) 
 

22 

 In addition to the performance optimization options above, routine maintenance is critical 

for reliable and efficient CHP system operations. Many of the steam system maintenance tips in 

the previous section apply to the steam circuit of a CHP system. It must be noted that major 

maintenance of turbines (e.g., a turbine overhaul) should only be performed by trained turbine 

repair specialists. However, there are a number of routine maintenance tasks that can be 

performed by mill personnel to ensure that turbines are operating at peak performance. Typical 

measures include: 

• vibration measurements to detect worn bearings, rotors, and damaged blade tips; 

• inspection of auxiliaries such as lubricating-oil pumps, coolers, and oil strainers; 

• inspection and verification of equipment alignment; 

• checking safety devices such as the operation of overspeed controls; 

• replacement of filter elements; 

• inspection of steam piping supports to check for damage due to torque or vibration; 

• for gas turbines, inspection of the combustion path for fuel nozzle cleanliness and wear, 

along with the integrity of other hot gas path components; 

• for steam turbines, dislodging of water solid deposits by applying manual removal 

techniques, cracking the deposits by shutting the turbine off and allowing it to cool, and 

washing the turbine with water while it is running. (Kramer 2009) 

B. Natural Gas-Fired Dryers and Thermal Oxidizers 

 

Some pulp and paper mills may operate natural gas-fired equipment such as direct-fired 

dryers or thermal oxidizers. Although steam-heated dryers are more common in the pulp and 

paper industry, some mills may operate direct-fired dryers to reduce the moisture content of 

boiler fuel (e.g., wet bark or wastewater treatment residuals) or to dry pulp or paper. Thermal 

oxidizers or regenerative thermal oxidizers (RTOs) may be used to incinerate process vent gases 

such as pulp mill non-condensable gases (NCG) or stripper off gas (SOG) to control organic 

hazardous air pollutant (HAP) or TRS emissions. Semi-chemical pulp mills may also operate 

RTOs in order to comply with the organic HAP emission limit in the national emissions 

standards for hazardous air pollutants (NESHAP) for pulp and paper combustion sources. 

In general, GHG emissions from fossil-fuel fired equipment can be calculated based on 

emissions factors and fuel use data (e.g., following the approach in subpart C of the GHG MRR 

for stationary combustion sources). The GHG emissions associated with combustion of NCG 

and SOG, and also burning of pulping by-products (e.g., tall oil and turpentine that are 

sometimes burned as fuel when no beneficial use is available), are biogenic since NCG, SOG, 

tall oil, and turpentine are derived from wood. The quantity of GHG emissions resulting from 

combustion NCG, SOG, tall oil, and turpentine is expected to be relatively small because of their 

infrequent use as fuel (e.g., in boilers and lime kilns) (e.g., less than 0.005 percent of the mill’s 

total GHG emissions). (EPA 2009c) 

Approaches for reducing GHG emissions from fossil fuel-fired equipment could include 

fuel switching or energy efficiency measures. In the case of natural gas-fired equipment, 

however, fuel switching to a lower carbon fuel is not an option because natural gas emits less 

CO2 per amount of heat derived than other gaseous or liquid fuels commonly used in the pulp 
 

23 

and paper industry (i.e., fuel oil). Selection of technologies requiring less fuel consumption is 

also a consideration. 

 

At many pulp mills, pulping vent gases (NCG and SOG) are routed to power boilers 

and/or lime kilns for destruction. Thermal oxidizers may serve as primary controls (or back-up 

controls for times when the NCG or SOG stream must be diverted from the boiler or lime kiln). 

Use of existing combustion processes such as power boilers or lime kilns is preferable over use 

of a separate thermal oxidizer from both a fuel use and emissions reduction perspective (for 

GHG and other emissions, such as NOX or SO2, which may increase due to RTO use). Thermal 

oxidizers employing heat recovery (e.g., regenerative or recuperative thermal oxidizers) may also 

reduce fuel consumption. Catalytic oxidizers and regenerative catalytic oxidizers (RCOs) 

operate at lower temperatures than do thermal oxidizers or RTOs, but catalytic systems have 

found limited use in the pulping industry (due in part to the high sulfur content of pulp mill vent 

gases, which can blind or poison catalytic systems). 

Combustion efficiencies of some natural gas-fired combustion devices (e.g., some types 

of gas-fired dryers) and emission control devices such as RCOs and RTOs can sometimes be 

relatively low compared to power boilers, allowing a portion of the fuel to exit the combustion 

device as CH4 (in highly variable amounts). This condition may exist in combustion devices that 

operate with low burner temperatures, in situations where the burner is operated at heat input 

rates below or at the low end of its design operating range, due to catalyst problems, or in 

devices where the natural gas burners are damaged or poorly maintained. The auto-ignition 

temperature of natural gas is approximately 1000°F, with greater temperatures (e.g., over 1400°F 

in thermal systems) required to achieve consistent combustion efficiency. (ICFPA 2005) Such 

emissions of CH4 can be mitigated though proper design, and attention to monitoring and 

maintenance of the combustion device (e.g., to ensure combustion temperatures are maintained 

and that valves are functioning properly). 

C. Kraft and Soda Lime Kilns 

Kraft (and soda) pulp mills use lime kilns to regenerate a portion of the chemical cooking 

solution. The function of the lime kiln is to oxidize lime mud (CaCO3) to reburned lime (CaO), a 

process known as calcining. The CaO produced in the lime kiln is used in the causticizing 

reactions that take place in the green liquor slaker and causticizers to produce the NaOH used in 

the white liquor. 

In the kraft (and soda) pulping and chemical recovery process, biomass carbon from the 

wood is dissolved and either emitted as biomass CO2 from the recovery furnace or captured in 

Na2CO3 exiting in the smelt from the recovery furnace. In the process of converting the Na2CO3

into new pulping chemicals, this biomass carbon (i.e., the carbonate ion) is transferred to CaCO3

in the causticizing process. In the lime kiln, the CaCO3 is converted to CaO (i.e., lime material 

used in the chemical recovery process) and biomass CO2 originating from the wood residuals 

contained in black liquor is released to the atmosphere. Figure 2 contains a simplified 

representation of the kraft pulping and chemical recovery process. (EPA 2009c, ICFPA 2005) 
 

24 

Figure 2. Simplified Representation of the Kraft Pulping and Chemical Recovery System 

Unlike lime kilns used at lime production facilities, where CO2 emissions are entirely 

fossil in nature, the CO2 emitted from kraft mill lime kilns originates from two sources: (1) fossil 

fuels burned in the kiln, and (2) conversion of CaCO3 (or “lime mud”) generated in the recovery 

process to CaO (lime). As shown above (in Figure 2), the calcium carbonate-derived CO2

emissions almost exclusively originate from biomass. The lime kiln typically produces about 

95 percent of the lime needed for the causticizing reaction. Either make-up lime or limestone is 

purchased to account for losses. (EPA 2009c) 

Several pulp mills pipe stack gas from lime kilns or calciners to adjacent precipitated 

calcium carbonate (PCC) plants for use as a raw material. PCC is sometimes used as an 

inorganic filler or coating material in paper and paperboard products. 

The EPA is presently unaware of control measures to reduce fossil-related GHG from 

pulp mill lime kilns other than energy efficiency measures. Some energy efficiency measures 

are described below. 

Lime kiln oxygen enrichment. Oxygen enrichment is an established technology for 

increasing the efficiency of combustion and has been adopted in various forms by a number of 

industries with high-temperature combustion processes (e.g., glass manufacturing). According to 

one study, oxygen enrichment of lime kilns can reduce fuel requirements by around 7 to 12 

percent. Reportedly, capital investments for oxygen enrichment are negligible compared to other 

recausticizing plant upgrades, requiring relatively simple equipment, including feed piping, an 
 

25 

injection lance, and controls. Payback periods have been estimated between 1 and 3 years. 

(Kramer 2009, McCubbin 1996) 

Lime kiln modification. Several other modifications are possible to reduce energy 

consumption in lime kilns. High-efficiency filters can be installed to reduce the water content of 

the kiln inputs, thereby reducing the required evaporative energy. Higher efficiency refractory 

insulation brick can be installed to reduce heat losses from the kiln. One estimate indicated that 

newer high-performance refractory can lead to lime kiln energy savings of up to 5 percent. Heat 

can also be recovered from the lime and from kiln exhaust gases to pre-heat incoming lime and 

combustion air. According to one estimate, the energy savings achievable from implementing all 

of these measures is around 0.47 MMBtu per ton of production. Such improvements may also 

improve the rate of recovery of lime from green liquor, thereby reducing a mill’s requirement for 

additional purchased lime (Kramer 2009). 

Lime kiln electrostatic precipitators. Electrostatic precipitators can replace wet scrubbers 

on lime kilns and lead to energy and water savings. Electrostatic precipitators can collect kiln 

dust as a dry material, and return it directly to the kiln feed without unnecessarily loading the 

lime mud filter. In contrast, wet scrubbers require effluent recycling via the lime mud filter and 

are significant consumers of water. One estimate indicated that, for every 1 percent reduction in 

lime mud feed moisture content (through the addition of dry dust), lime kiln energy consumption 

is reduced by around 46 MMBtu. Another analysis found that increasing mud dryness from 70 

to 75 percent would reduce fuel consumption by 0.4 MMBtu per ton of lime. (Kramer 2009) 

D. Makeup Chemicals 

Makeup chemicals are a source of process-related CO2 emissions at chemical pulp mills. 

Over time, small amounts of sodium and calcium are lost from the recovery cycle at kraft and 

soda facilities. Typically, lost sodium and calcium are replaced using make-up chemicals (e.g., 

Na2SO4, CaCO3, Na2CO3) that are added into the recovery loop (e.g., with the spent pulping 

liquor). When carbonates (CaCO3, Na2CO3) are added, the carbon in these make-up chemicals, 

which can be derived from biomass or mineral sources, is emitted as CO2 from recovery furnaces 

and lime kilns. In cases where the carbon is mineral-based, emissions of CO2 would contribute 

to GHG emissions. (EPA 2009c) 

The EPA has not identified any specific control measures for minimizing emissions 

associated with makeup chemicals. Practices to ensure good chemical recovery rates in the 

pulping and chemical recovery process (e.g., at the recovery furnace) would minimize the need 

for carbonate makeup chemicals. The addition of sodium and calcium in forms that do not 

contain carbon, such as Na2SO4, NaOH, and CaO, would further minimize the need for carbonate 

makeup chemicals and is a practice employed at many mills. (NCASI 2008b) As of this writing, 

little data are available on the use and GHG emissions associated with makeup chemical use. 

However, EPA’s GHG MRR will provide this information and may be useful for future 

benchmarking studies of makeup chemical use (and eventual determination of factors that 

contribute to reduction in makeup chemical needs). 
 

26 

E. Flue Gas Desulfurization Systems 

Limestone (CaCO3) and dolomite (CaCO3MgCO3) are basic raw materials used by a wide 

variety of industries, including as a sorbent in flue gas desulfurization (FGD) systems and 

fluidized bed boilers at electric utility and industrial plants. Wet limestone scrubbers are one 

type of FGD that use limestone/water slurries to absorb SO2 from the flue gas. A chemical 

reaction between the SO2 gas and crushed limestone releases CO2 as a by-product. A few coalfired boilers at pulp and paper mills incorporate such FGD systems. (ICFPA 2005) The EPA’s 

GHG MRR for Stationary Combustion (Subpart C) contains an equation for calculating CO2

emissions from sorbent use (for fluidized bed boilers that use sorbent injection and units 

equipped with flue gas desulfurization systems). (40 CFR Part 98, subpart C) 

Methods for reducing SO2 from coal-fired boilers include use of low-sulfur coal or a 

variety of FGD systems. Some types of FGD systems use sorbents other than carbonates, and, 

therefore, do not add CO2 to the boiler stack emissions. The impact of different types of SO2

controls on coal-fired electric generating unit CO2 emissions is discussed in a separate document 

related to this one, Available and Emerging Technologies for Control of Greenhouse Gas 

Emissions from Coal-Fired Electric Generating Units. 

F. Anaerobic Wastewater Treatment 

 

The pulp and paper industry is among the largest industrial process water users in the 

U.S. Many pulp and paper mills operate wastewater treatment systems that can be a source of 

CH4 emissions if operated under anaerobic conditions. Wastewater treatment also produces CO2

that is considered to be biogenic. Emissions of N2O from wastewater treatment are considered to 

be negligible. (ICFPA 2005) 

The EPA’s threshold analysis for the proposed GHG MRR suggested that less than about 

3 percent of pulp and paper wastewater treatment systems would trigger the proposed 25,000 

mtCO2e threshold (equivalent to 27,600 tons CO2e), with only one system triggering a threshold 

of 100,000 mtCO2e. (EPA 2009b) 

NCASI studies have confirmed that mechanical clarifiers and aerobic biological 

treatment systems with high intensity mixing (such as activated sludge treatment systems) do not 

generate significant amounts of CH4. Anaerobic treatment systems are known to generate CH4, 

but there are very few biological treatment systems in the U.S. forest products industry designed 

for anaerobic decomposition of organic matter. There are, however, operations that can contain 

zones that become anaerobic, including aerated stabilization basins (ASBs), primary settling 

basins, and post-aeration basins. (NCASI 2008a) One way to minimize CH4 emissions from 

such systems would be to minimize the potential for formation of anaerobic zones in the 

wastewater treatment system (e.g., though placement of aerators where practical). 

 Though uncommon in the pulp and paper industry, some industrial treatment systems are 

covered and designed for anaerobic wastewater treatment or digestion of sludge. The CH4

released from these systems can be collected and burned. 
 

27 

G. On-site Landfills 

Many pulp and paper mills use on-site landfills to dispose of wastewater treatment plant 

(WWTP) residuals, combustion ash residues, and other inorganic solid wastes (e.g., lime slaker 

grits, green liquor dregs from the causticizing process). According to NCASI 2008a, wastewater 

treatment residuals and ash constitute the vast majority of the solid residuals landfilled. Ash is 

essentially inert, so only WWTP residuals are considered to produce GHG emissions through 

degradation. NCASI and others have documented that residuals collected in primary treatment 

alone degrade in landfills very slowly or not at all, probably because of a lack of essential 

nutrients (particularly phosphorus and nitrogen) to support anaerobic biological activity. (NCASI 

2008a) 

After being placed in a landfill, waste is initially decomposed by aerobic bacteria. After 

the oxygen has been depleted, the remaining waste is available for consumption by anaerobic 

bacteria, which break down organic matter into substances such as cellulose, amino acids, and 

sugars. These substances are further broken down through fermentation into gases and shortchain organic compounds that form the substrates for the growth of methanogenic bacteria. 

These CH4-producing anaerobic bacteria convert the fermentation products into stabilized 

organic materials and biogas. (EPA 2009a) 

Methane generation from a given landfill is a function of several factors, including: 

(1) the total amount of waste disposed of in the landfill each year (annual waste acceptance rate); 

(2) the age of the landfill (or the total quantity of waste in-place); (3) the characteristics of the 

waste (i.e., composition and organic content of waste); and (4) the climatic conditions 

(temperature and soil moisture content – wet soils promote anaerobic degradation). The amount 

of CH4 emitted is dependent on the amount of CH4 generated less the amount of CH4 that is 

recovered (and either flared or used for energy purposes) and the amount of CH4 oxidized near 

the landfill surface prior to being released into the atmosphere. (EPA 2009a) 

 ICFPA 2005 includes a “screening” emission factor for CH4 of 3,500 kilograms (kg) 

CO2e/dry metric ton solid waste (3.86 tons CO2e/dry short ton solid waste). This “screening” 

emission factor conservatively assumes that 50 percent of landfilled waste is degradable organic 

carbon, 50 percent of the degradable organic carbon degrades to gas, 50 percent of the carbon in 

the gas is contained in CH4, none of the CH4 is oxidized in the landfill cover or captured, and all 

is released in the same year that the waste is landfilled. More refined methods of estimating 

landfill CH4 emissions will normally yield lower estimates of emissions. Subpart TT to EPA’s 

GHG MRR (and the associated technical support document) contains the methods for calculating 

CH4 emissions from industrial landfills, based on the quantity of waste disposed in the landfill, 

the fraction of degradable organic carbon (DOC) in the waste, the fraction of DOC dissimilated, 

the fraction by volume of CH4 in the landfill gas, the decay rate of the waste, and the years when 

the waste was disposed and the emissions are calculated. 

 Control measures to reduce GHG emissions from pulp and paper landfills could include: 

(1) dewatering and burning the WWTP residuals in an on-site boiler, or (2) capture and control 

of landfill gas by burning it in an on-site combustion device. The practice of burning WWTP 

residuals in boilers for energy recovery and solid waste management has become more common 

in recent years, particularly as technologies for dewatering this material have advanced. Pulp 
 

28 

and paper mill WWTP residuals are comprised predominantly of wood fiber, considered to be 

biomass material. Pulp mill WWTP residuals are usually co-fired fired in small amounts relative 

to other boiler fuels (e.g., less than 10 percent of boiler heat input). 

Industrial waste landfills are not subject to federal standards. New source performance 

standards and emission guidelines require some municipal solid waste (MSW) landfills to 

capture and control landfill gas. Nevertheless, landfills could potentially be capped with low 

permeability cover material and the landfill gases collected and burned for their energy content. 

It is expected that landfill gas-to-energy projects would only be cost-effective for larger landfills 

in the pulp and paper industry. Cost data for landfill gas-to-energy projects at pulp and paper 

mills are unavailable because, as of this writing, we are unaware of any landfill gas collection 

systems installed at U.S. pulp and paper industry landfills. 
 

29 

III. Additional Energy Efficiency Improvements 

This section discusses general energy efficiency measures that could be employed by 

energy-using equipment at pulp and paper mills (e.g., equipment that uses electricity, steam heat, 

or heat recovered from another process) other than processes that directly emit GHG. Examples 

of such equipment include raw material handling systems, digesters, stock washers, screens, 

evaporators, bleaching equipment, paper machines, and various other types of pulp and paper 

process equipment. 

 If the necessary process energy is generated at the mill site, the application of energy 

efficiency measures can reduce electrical or steam demand from on-site power boilers, 

combustion turbines, or recovery furnaces, resulting in a reduction in GHG emissions at the mill 

site. If the energy required by the process is not self-generated by the mill, then energy 

efficiency measures could result in a reduction of purchased electricity (or in some cases a 

reduction in purchased/imported steam), with a corresponding reduction in indirect GHG 

emissions at the off-site location where the energy is generated. 

The energy efficiency measures presented in this document are summarized from an 

October 2009 ENERGY STAR ® report, Energy Efficiency Improvement and Cost Saving 

Opportunities for the Pulp and Paper Industry, developed by Ernest Orlando Lawrence Berkeley 

National Laboratory (Kramer 2009). Please note that the energy efficiency measures discussed 

here are not universally applicable to all mills. Applicability of energy reducing measures 

depends on the pulping process, equipment configurations, desired product characteristics, or 

various other factors. Also, there are likely other energy efficiency measures not discussed here 

that individual mills might identify, which could be applied on a site-specific basis. 

A. Energy Efficiency Improvements in Steam Systems 

 

 Steam is used in a number of important applications throughout the typical pulp and 

paper mill, but by far most significantly in the cooking, bleaching, evaporation, and drying 

processes. Over 80 percent of the energy consumed by the industry is in the form of boiler fuel. 

According to a recent study by the U.S. DOE, the U.S. pulp and paper industry could reduce its 

fuel use by 12.5 percent, and save 278 TBtu, by implementing best practice steam system 

improvement opportunities. Energy efficiency improvements to steam systems, therefore, 

represent the most significant opportunities for energy savings in pulp and paper mills. (Kramer 

2009) 

 Two primary sources of steam in pulp and paper mill operations are recovery furnaces 

and power boilers. As discussed previously, recovery furnaces are fired with black liquor to 

recover pulping chemicals and produce steam for mill process heating applications, and often for 

co-generation of on-site electricity. Power boilers can be fired with multiple fuels and operate at 

high pressures for co-generation of both electrical power and steam. Whatever the use or the 

source of the steam, efficiency improvements in steam generation, distribution, and end-use are 

possible. (Kramer 2009) 
 

30 

 Steam distribution systems are often quite extensive and can be major contributors to 

energy losses within a typical pulp and paper mill. Energy efficiency improvements to steam 

distribution systems are primarily focused on reducing heat losses throughout the system and 

recovering useful heat from the system wherever feasible. The following measures describe a 

number of key opportunities for saving energy in industrial steam distribution systems. 

Steam distribution controls. Steam demand can be interrupted due to changing operating 

procedures at steam-using processes (e.g., paper machines or turbines), or due to operational 

failures (e.g., a sheet breakage). This can lead to the dumping of excess steam or additional fuel 

use for back-up boilers. Modern control systems have been deployed to better manage a steam 

system, reducing the need for back-up steam capacity or the need to dump steam. (Kramer 2009) 

 In one example, a second-generation control system was implemented for a steam 

system, which consisted of three paper machines, two natural gas-fired gas turbine-based CHP 

units, one steam turbine, and a steam accumulator. The system is a model-based predictive 

control system to manage steam loads better. The system resulted in a 95 percent reduction of 

steam venting and a 70 percent reduction in fuel use for back-up steam generation, with a 

payback period of less than 6 months. (Kramer 2009) 

Improved insulation. Using more insulating material or using the best insulation material 

for the application can save energy in steam distribution systems. Crucial factors in choosing 

insulating material include low thermal conductivity, dimensional stability under temperature 

change, resistance to water absorption, and resistance to combustion. Other characteristics of 

insulating material may also be important depending on the application, such as tolerance of 

large temperature variations, tolerance of system vibrations, and adequate compressive strength 

where the insulation is load-bearing. (Kramer 2009) 

 Removable insulating pads are commonly used in industrial facilities for insulating 

flanges, valves, expansion joints exchangers, pumps, turbines, tanks and other surfaces. 

Insulating pads can be easily removed for periodic inspection or maintenance and replaced as 

needed. Insulating pads also contain built-in acoustical barriers to help control noise. Reported 

estimates indicate that the installation of removable insulation on valves, pipes, and fittings can 

reduce steam system energy use by 1 to 3 percent. (Kramer 2009) 

 

 Case studies from the U.S. pulp and paper industry indicate that the payback period for 

improved insulation is typically less than one year. At one mill, 1,500 feet of saturated steam 

lines to the dryer were not insulated, leading to significant losses of energy and process steam 

temperature and pressure. The addition of insulation reduced this heat loss and maintained the 

process temperature throughout the lines. In addition to adding insulation, the mill also replaced 

70 steam traps, which resulted in a 10 percent increase in condensate return. Total energy 

savings amounted to about 63,000 MMBtu at a cost savings of over $138,000. With 

implementation costs of $69,280, the payback period was six months. (Kramer 2009) 

 At another mill, it was estimated that the repair of insulation could lead to annual energy 

savings of $80,000 at a repair cost of around $25,000. The payback period for insulation repair 

was around four months. (Kramer 2009) 
 

31 

Insulation maintenance. It is often found that after heat distribution systems have 

undergone some form of repair, the insulation is not replaced. In addition, some types of 

insulation can become brittle or rot over time. As a result, a regular inspection and maintenance 

system for insulation can also save energy. (Kramer 2009) 

 One estimate indicates that (as of 2002) roughly half of U.S. pulp and paper mills could 

significantly benefit from insulation improvements and installation and that these mills could 

reduce their boiler fuel use anywhere from 3 to 10 percent if such improvements were pursued. 

(Kramer 2009) 

 As part of an energy use and energy efficiency opportunities case study of 10 different 

pulp and paper mills in Illinois, it was shown that installing or improving insulation on pipes and 

valves could save (on average) over 3,600 MMBtu and over $12,000 per year. (Kramer 2009) 

Steam trap improvement. Using modern thermostatic element steam traps can reduce 

energy use while also improving reliability. The main efficiency advantages offered by these 

traps are that they open when the temperature is very close to that of saturated steam (within 4°F 

or 2°C), purge non-condensable gases after each opening, and are open on startup to allow a fast 

steam system warm-up. These traps also have the advantage of being highly reliable and useable 

for a wide variety of steam pressures. (Kramer 2009) 

 A new steam trap design is the venturi orifice steam trap, which is better suited for 

varying loads than traditional mechanical steam traps. One mill in Europe changed 25 steam 

traps to the new type on a coating battery, which resulted in energy costs savings of nearly 

$200,000, with a payback period of 2.5 months. Other projects saved 11 percent on steam 

demand in preheater and end corrugator rolls (10 steam traps), and a 30 percent on a flute 

machine. (Kramer 2009) 

Steam trap maintenance. A simple program of checking steam traps to ensure that they 

are operating properly can save significant amounts of energy for very little money. In the 

absence of a steam trap maintenance program, it is common to find up to 15 to 20 percent of 

steam traps malfunctioning in a steam distribution system. Annual failure rates are estimated at 

10 percent or more. Energy savings for a regular system of steam trap checks and follow-up 

maintenance are conservatively estimated at 10 percent. Several industrial case studies suggest 

that investments for repair or replacement steam traps are very low, resulting in a payback period 

of only a few months or less. (Kramer 2009) 

 At one mill, opportunities were found for repairing failed steam traps that could save the 

mill about $31,000 in fuel use and about $3,900 in water use annually. The annual energy 

savings were estimated at 1,262 MMBtu of natural gas and 12,168 MMBtu of other fuels. The 

estimated costs to implement this measure were between roughly $7,400 and $12,400, which 

implies a payback period of well under a year. (Kramer 2009) Another estimate suggests a 

capital cost of $0.092/MMBtu (2008 dollars) to implement this measure, with a fuel savings of 

9.2 percent. (Staudt 2010) 

Steam trap monitoring. Attaching automated monitors to steam traps in conjunction with 

a maintenance program can save even more energy without significant added cost. This measure 

is an improvement over steam trap maintenance alone, because it gives quicker notice of steam 
 

32 

trap failure and can detect when a steam trap is not performing at peak efficiency. Employing 

steam trap monitoring has been estimated to provide an additional 5 percent in energy savings 

compared to steam trap maintenance alone, at a payback period of around one year. Systems that 

are able to implement steam trap maintenance are also likely to be able to implement automatic 

monitoring. (Kramer 2009) 

Leak repair. As with steam traps, steam distribution piping networks often have leaks 

that can go undetected without a program of regular inspection and maintenance. Reported 

estimates indicate that repairing leaks in U.S. pulp and paper mill steam distribution systems 

could lead to fuel savings of around 2 percent. Case studies of U.S. pulp and paper mills suggest 

a payback period for this measure of less than one year. (Kramer 2009) 

 One mill found opportunities for repairing steam leaks around paper machines that could 

result in annual fuel and water cost savings of about $20,000, with a payback period of around 1 

to 1.5 years. (Kramer 2009) Another estimate indicates capital costs of $0.023/MMBtu (2008 

dollars) to implement this measure, with a fuel savings of 2.8 percent. (Staudt 2010) 

 

Flash steam recovery. When a steam trap purges condensate from a pressurized steam 

distribution system to ambient pressure, flash steam is produced. As with flash steam produced 

by boiler blow down, steam trap flash steam can be recovered and used for low-grade facility 

applications, such as space heating or feed water preheating. (Kramer 2009) 

 The potential for this measure is site-dependent, as its cost effectiveness depends on 

whether or not areas where low-grade heat is useful are located close to steam traps. Where 

feasible, this measure can be easy to implement and can save considerable energy. In an 

example from the food industry, an analysis of a U.S.-based food processing facility predicted 

that the installation of a flash steam recovery system used for feed water preheating would save 

the plant around $29,000 in fuel costs annually, at a payback period of less than 1.8 years. Based 

on the reduction in boiler fuel use, it was further estimated that the plant’s carbon emissions 

would be reduced by 173 ton/yr. (Kramer 2009) 

B. Energy Efficiency Improvements in Raw Material Preparation 

1. Debarking 

 Cradle debarker. Using a cradle debarker over other debarking methods can reduce 

energy consumption by up to 33 percent. Cradle debarkers also inflict less damage to the logs. 

The U.S. DOE reported that a cradle debarker can reduce costs by $30/ton of wood. (Kramer 

2009) 

Use secondary heat in debarking. When logs need to be defrosted prior to debarking, 

waste heat from the plant can be used to replace steam. Recovering waste heat for this operation 

can save $150,000 (2001 dollars) in energy costs. Capital investments were estimated to be 

$110,000. (Kramer 2009)
 

33 

2. Chip Handling, Screening, and Conditioning 

 Replace pneumatic chip conveyor with belt conveyor. Belt conveyors are typically more 

energy efficient than pneumatic conveyors. One study performed in 2001 indicated that a belt 

conveyor operating at 1 kWh/ton could replace an 18.2 kWh/ton pneumatic conveyor, resulting 

in a savings of 17,200 kWh/day, or $210,000/yr in electricity costs. However, the installation 

and maintenance costs of belt conveyors can be significant. (Kramer 2009) 

 Automatic chip handling and thickness screening. Automatic chip handling and 

thickness screening can reduce steam consumption in the digester and evaporator. Some studies 

suggest that digester yield can be increased by 5 to 10 percent, although this is somewhat offset 

by the raw material screened out. The return on investment may be 15 to 20 percent. (Kramer 

2009) 

 Bar-type chip screens. Bar-type chip screens typically have lower energy consumption 

than other types of screens, even though capital costs are approximately the same. Energy 

savings were estimated to be 0.33 MMBtu/ton chemical pulp due to yield increases, and 

operating and maintenance costs were estimated to be reduced by $0.70/ton pulp (1998 dollars). 

(Kramer 2009) 

 Chip conditioning. Chip conditioners improve the delignification process. Energy 

savings from replacing chip slicers were estimated to be 0.19 MMBtu/ton chemical pulp, and 

savings from reduced operating and maintenance costs were estimated to be $0.40/ton chemical 

pulp (1998 dollars). (Kramer 2009) 

C. Energy Efficiency Improvements in Chemical Pulping 

1. Digesters (Chip Cooking) 

 Use of pulping aids. Chemical pulping aids added to the pulping process can increase 

pulp yields and reduce energy consumption. Viability of this measure will depend on the cost of 

the chemical pulping aids versus the fiber savings. A study of one pulping aid estimated that 

energy savings of 125,000 Btu/ton of processed wood chips may be realized. Other benefits 

include an increase in yield of 2 to 5 percent per ton of wood, reduced pulp rejects, reduced use 

of bleaching chemicals, and reduced sulfur-based emissions. Another study of a different 

pulping aid indicated an energy savings of 8 to 10 percent and yield increases of 4 to 6 percent. 

(Kramer 2009) 

 Continuous digester control systems. Control systems to optimize the digester can reduce 

production losses, operating costs, and environmental impacts while increasing paper quality and 

quantity. Initial implementation of one computer model resulted in a 1 percent energy savings 

for the pulping process. (Kramer 2009) 

 Batch digester modification. The use of indirect heating and cold blow can reduce 

energy consumption in batch digesters. Indirect heating involves withdrawing cooking liquor 

from the digester and pumping it through an external heat exchanger. Energy savings were 
 

34 

estimated to be 3 MMBtu/ton, although maintaining the heat exchanger will increase overall 

maintenance costs. Cold blow systems displace hot spent pulping liquor from the digester using 

brownstock washer filtrate. Heat can be recovered from the spent liquor for heating subsequent 

cooks, which reduces steam consumption. One study estimated the energy savings to be 

$2 million/yr for a 1,000 ton/day mill. However, capital costs for this system can be high. 

(Kramer 2009) 

 Digester blow/flash heat recovery. Heat can be recovered from steam produced when the 

hot pulp and cooking liquor are reduced to atmospheric pressure at the end of the cooking cycle. 

For example, the black liquor that is flashed in stages from continuous digesters can be used in 

chip steaming. An audit at one facility showed that installing new heat exchangers and other 

piping improvements to improve blow heat recovery could save 940,000 MMBtu of fuel, 

705,000 MMBtu of natural gas, and $2.35 million (2003 dollars) annually, with a payback period 

of about one year. At another mill, the addition of a digester heat recovery system was expected 

to reduce natural gas usage by 130,000 MMBtu/yr and save $280,000/yr. (Kramer 2009) 

2. Pulp Washing 

 Optimize dilution factor. Organic solids and spent cooking chemicals can be washed 

from the pulp with brownstock, resulting in a higher level of chemical recovery, while 

minimizing dilution of black liquor. Optimizing the dilution factor control will lower the average 

amount of water that must be evaporated from weak black liquor, thereby reducing steam 

consumption in the evaporators. The dilution factor can be optimized by controlling shower 

water flow on the last washing stage to an optimum level that can be determined by considering 

the cost of steam, the cost of bleaching chemicals, the impact on effluent quality, and other 

process variables. At one plant, it was estimated that these improvements could reduce water 

usage by 200 gallons per minute (gal/min) and reduce natural gas usage by 310,000 MMBtu/yr, 

resulting in costs savings of $580,000/yr. (Kramer 2009) 

 Improved brownstock washing. Replacing conventional vacuum pressure units with 

pressure diffusion or wash presses for brownstock washing can reduce the electricity and steam 

consumption and reduce bleaching chemical usage. Estimated steam savings may be as much as 

9,500 Btu/ton of production, and electricity savings may be about 12 kWh/ton of production. 

(Kramer 2009) 

3. Bleaching 

 Heat recovery from bleach plant effluent. Heat exchangers can be used to recover the 

large amount of heat in the bleach plant effluent. An audit at one facility showed that the heat 

from the bleach plant effluent could be used to generate hot water for the paper machine. Energy 

savings were estimated to be 890,000 MMBtu/yr, with annual cost savings of $2.4 million (2003 

dollars). After a capital investment of $1.6 million, the estimated payback period was 0.7 years. 

(Kramer 2009) 

 Chlorine dioxide (ClO2) heat exchange. Although solutions of ClO2 are normally chilled 

to maximize ClO2 concentration, preheating the solution prior to entering the mixer will reduce 
 

35 

steam demand in the bleach plant. An audit at one mill identified a way to preheat the solution 

that reduced costs by $61,000/yr (2003 dollars) for fuel, electricity, and steam savings. The 

capital costs were estimated to be $124,000 for a payback period of about two years. (Kramer 

2009) 

D. Energy Efficiency Improvements in Mechanical Pulping 

1. Mechanical Pulping 

 

Refiner improvements. Refiners are used in mechanical pulping to rub or grind the wood 

fibers apart. Several improvements are possible within the refiner section of a mill, which can 

reduce electricity consumption in mechanical pulping. For example, a newsprint mill 

implemented a refiner control strategy to minimize variations in the freeness of ultra-high-yield 

sulfite pulps and saved 51.3 kWh per ton of production due to reduced motor load. Another 

option in refining is the switch to conical refiners rather than disk refiners. By decreasing the 

consistency of pulping to about 30 percent from 50 percent, a 7 to 15 percent electricity savings 

may be possible in TMP and RMP processes. One study estimated an electricity savings 

potential of 11 percent due to such mechanical refining improvements, at a capital cost of around 

$7.7/ton (2000 dollars) of pulp production. (Kramer 2009)

 Thermopulping. Thermopulping is a variation of the TMP process, whereby pulp from 

the primary stage refiner is subjected to a high-temperature treatment for a short time in a 

thermo-mixer and in the subsequent secondary refiner. The higher operating pressures in the 

secondary refiner reduce the volumetric flow of generated steam. Published estimates suggest 

that thermopulping can reduce specific energy consumption compared to TMP by up to 

20 percent. (Kramer 2009)

 Heat recovery in TMP. A vast amount of steam is produced as a by-product of thermomechanical pulping. This low-pressure steam is often contaminated, but most of the energy can 

be reclaimed for use in other mill processes through heat recovery equipment. Heat recovery 

options include: (1) mechanical vapor recompression for integrated mills, where the clean steam 

generated can be used in the paper machine dryer section, (2) direct-contact heat exchangers for 

generating hot water for use in paper machines and as boiler makeup water and clean process 

steam, (3) reboilers for producing clean process steam, and (4) other devices such as thermo 

vapor recompression and cyclotherm plus heat pump systems. One study estimated that typical 

heat recovery systems for pressurized refiners can generate 1.1 to 1.9 tons of clean steam at dryer 

can pressure per ton of pulp. Payback periods vary widely depending on capital costs, but can be 

as low as a few months. Average installation costs have been estimated to be $21/ton of pulp 

(2000 dollars), with significant increases in operations and maintenance costs. (Kramer 2009) 

 Pressurized groundwood. In a pressurized groundwood system, grinding takes place 

under compressed air pressure where water temperature is high (more than 95oC), thereby 

allowing for higher grinding temperatures without steam flashing. The higher temperature 

promotes softening of the lignin, which improves fiber separation and reduces specific energy 

consumption. The technical literature claims around 20 to 36 percent saving in electricity 

compared with atmospheric mechanical pulping processes. (Kramer 2009) 
 

36 

2. Repulping of Market Pulp 

Continuous repulping. The repulping process for purchased market pulp involves 

blending the dried pulp feedstock with water in a large tank to produce fibrous slurry. Typically 

this is done as a batch process, but converting to a continuous process can lead to energy savings 

due to improved process efficiency. One study estimated that energy savings of up to 40 percent 

are possible, in the form of reduced pulping motor power requirements. If the existing repulper 

can be retrofitted, capital costs are estimated around $100,000 (2006 dollars). (Kramer 2009)

 Efficient repulping rotors. Newer repulper rotor designs have been optimized for power 

consumption. Reportedly, replacing an existing rotor with a new rotor that is optimized for 

efficiency can reduce rotor motor consumption by 10 to 30 percent. Payback periods for this 

measure have been estimated at 1 to 2 years. One mill installed and tested a new 500–

horsepower (hp) high-efficiency repulper rotor. Reportedly, the high-efficiency rotor reduced 

repulping electricity consumption by 23 percent. Another mill tested a new high-capacity, 

aerodynamic, variable-speed pulping rotor. The new rotor reduced electricity consumption by 

more than 50 percent. Projected annual energy savings amounted to around 3.6 GWh, or about 

$193,000 in electricity costs (2006 dollars). (Kramer 2009)

3. Secondary (Recovered) Fiber Processing 

 Increased use of recycled pulp. Statistics from the AF&PA indicated that, in 2009, a 

record-high 63.4 percent of the paper used in the U.S. was recovered for recycling. (AF&PA 

2010). The production of recycled pulps consumes, on average, significantly less energy than 

that required to produce mechanical or chemical wood pulps. One study estimates that costs for 

the construction of recycled pulp processing capacity in the U.S. is around $485 per ton of pulp; 

however, depending on the price of waste paper versus virgin pulp, this may result in up to $73.9 

per ton of pulp in operations and maintenance cost savings. However, recycled pulp produces 

sludge that can present a disposal difficulty. (Kramer 2009) In addition, there are limitations to 

the amount of recycled fiber that can be used for a given product (e.g., due to the shorter fibers of 

the recycled pulp, difficulty achieving the same brightness as virgin fiber, etc.). 

 Drum pulpers. Drum pulpers are applicable to mills that generate pulp from recovered 

paper and paperboard products. The more gentle mechanical action of drum depulpers allows 

contaminants to remain intact while the paper is defibered. Drum pulpers have lower energy 

requirements than conventional mechanical pulpers, can use less water, and reduce fiber 

shortening. However, when drum pulpers are used in brown fiber applications, the rapid wetting 

of furnish and the incomplete removal of bailing wire can reportedly cause problems. One 

analysis suggested that replacing a vat type batch pulper with a continuous drum pulper in deinking operations can reduce specific pulping energy by over 25 percent. (Kramer 2009)

 Heat recovery from de-inking effluent. De-inking effluents are often discharged at 

elevated temperatures and represent a possible source of low-grade heat recovery. The 

installation of heat exchangers in the effluent circuit can recover some of this heat for other 

beneficial uses, such as facility water heating. A study at one mill that had combined effluent 

streams at approximately 120°F with a flow rate of 600 gal/min showed that a heat exchanger 
 

37 

could generate warm filtered shower water for the mill’s paper machines, which would offset 

some of the mill’s steam demand. Annual boiler fuel savings of 37,000 MMBtu were estimated, 

which would lead to annual cost savings of $125,000 (2004 dollars). Capital costs were 

estimated at $375,000, with a payback period of about 3 years. (Kramer 2009)

 Fractionation of recycled fiber. One mill tested the potential of separating the long fibers 

and short fibers in a deinking line. This enables a simplification of the deinking line, with a 

capital reduction of 13 to 22 percent compared to traditional de-inked pulp (DIP) lines, a 

reduction in electricity consumption of 11 to 13 percent, and thermal energy reductions of 

40 percent. (Kramer 2009)

 Residence time-temperature-speed (RTS) pulping. In RTS (short-residence time, 

elevated-temperature, high-speed) pulping, energy consumption is reduced by increasing the 

rotational speed of the primary refiner. Temperatures of approximately 165°C are used, resulting 

in a reduction in specific energy consumption, with no loss of pulp quality. Published estimates 

for the energy savings achievable with RTS pulping vary. One study estimated that RTS pulp 

can be produced with approximately 15 percent lower specific energy requirements than pulp 

produced with a traditional refining system. Another study suggested that the specific energy of 

RTS pulping is around 20 percent lower than TMP processes. Yet another study estimated that 

the effect of increasing rotational speed on TMP refiners will reduce energy use by anywhere 

from 15 to 30 percent, depending on plate type and refiner mode. (Kramer 2009) 

E. Energy Efficiency Improvements in Papermaking 

1. Paper Machines – Forming and Pressing Sections 

 Shoe (extended nip) press. After paper is formed, it is pressed to remove as much water 

as possible. Normally, pressing occurs between two felt liners pressed between two rotating 

cylinders. Extended nip presses use a large concave shoe instead of one of the rotating cylinders. 

The additional pressing area adds dwell time in the nip and allows for greater water extraction 

(about 5 to 7 percent more water removal) to a level of 35 to 50 percent dryness. Greater water 

extraction leads to decreased energy requirements in the dryer, which leads to reductions in 

steam demand. Furthermore, reduced dryer loads allow plants to increase capacity up to 

25 percent in cases where production is dryer limited. Published estimates for the steam savings 

achievable through the installation of extended nip presses range from 2 to 15 percent, depending 

on product and plant configuration. Capital costs have been estimated at $38/ton of paper, and 

additional maintenance costs have been estimated at $2.24/ton of paper. (Kramer 2009)

 Paper machine vacuum system optimization. Vacuum pumps and a vacuum system exist 

on every paper machine. There is approximately the same horsepower associated with the 

vacuum system as is used to drive the entire paper machine. However, inefficiencies within the 

vacuum system increase the electrical and/or steam energy requirements of water removal, and, 

therefore, represent an important energy efficiency improvement opportunity. For example, 

following an audit of 14 paper machines owned by a Canadian manufacturer, a potential of 3.5 

MW of electrical power demand could be saved following system modifications, operational 

changes, and even removal of some vacuum pumps. Cost to achieve the first MW of savings 
 

38 

was considered negligible, with minor piping or operational changes. Total annual cost savings 

were approximately $400,000/year (2009 dollars). (Kramer 2009)

 Gap forming. Gap formers are an alternative to the Fourdrinier paper machine. The 

forming sections are very short, and the formation takes place in a fraction of the time it takes for 

a Fourdrinier machine (Martin et al. 2000). Coupling the former with a press section rebuild or 

an improvement in the drying capacity may increase production capacity by as much as 30 

percent. Nevertheless, retrofitting a gap former may increase retention losses. Energy savings 

from gap formers come from reduced electricity consumption. Published estimates for 

electricity savings are around 40 kWh/ton of paper. Based on one study, the cost to install a gap 

former, including the head box, is approximately $75,750/inch of width (1996 dollars), as 

opposed to $30,750 for a Fourdrinier with a head box. (Kramer 2009)

2. Paper Machines – Drying Section 

 Advanced dryer controls. One study of dryer control software indicated savings of 4,500 

pounds of steam per hour, which were estimated to lead to $360,000 in annual energy cost 

savings (2006 dollars). The payback period was estimated at under 3 years based on energy 

savings alone (i.e., no consideration of productivity benefits). Another study showed an annual 

savings of $263,000 (2005 dollars) due to reduced energy consumption, lower maintenance cost, 

and higher production. The reported payback period was seven months. (Kramer 2009)

 Reduced air requirements. Air-to-air heat recovery systems on existing machines recover 

only about 15 percent of the energy contained in the hood exhaust air. This percentage could be 

increased to 60 to 70 percent for most installations with proper maintenance and extensions of 

the systems. Paper machines with enclosed hoods require about one-half the amount of air per 

ton of water evaporated compared to paper machines with canopy hoods. Enclosing the paper 

machine reduces thermal energy demands since a smaller volume of air is heated. Electricity 

requirements in the exhaust fan are also reduced. Published estimates suggest steam savings of 

0.72 MMBtu/ton of paper and electricity savings of 6.3 kWh/ton of paper by installing a closed 

hood and an optimized ventilation system. Investment costs and operation and maintenance 

costs have been reported at $9.5/ton paper and $0.07/ton paper, respectively (2000 dollars). 

(Kramer 2009)

 Optimizing pocket ventilation temperature. Mill operators often monitor the operating air 

temperature of pocket ventilation systems, but when such systems operate at greater air 

temperatures than the minimum required for proper operation, energy can be wasted. One 

estimate stated that decreasing the temperature of the pocket ventilation system to between 180 

and 195°F decreased the overall use of steam by about 1,000 to 2,000 lb/hr in a typical mill. 

Paybacks are immediate since this measure involves improved operations and control rather than 

capital investments. (Kramer 2009)

 Waste heat recovery. In the paper drying process, several opportunities exist to recover 

thermal energy from steam and waste heat. One mill replaced the dryers with stationary siphons 

in their paper machine and was able to achieve energy savings of 0.85 MMBtu/ton due to 

improved drying efficiency, with an operation cost savings of $25,000 ($0.045/ton) (1998 

dollars). A second system used mechanical vapor recompression in a pilot facility to re-use 
 

39 

superheated steam into the drying process. Steam savings for this approach were up to 4.7 

MMBtu/ton (50 percent), with additional electricity consumption of 160 kWh/ton. A third 

system noted in the literature was the use of heat pump systems to recover waste heat in the 

drying section. One study estimated steam energy savings of around 0.4 MMBtu/ton of paper 

are achievable through paper machine heat recovery, with installation costs of around $18 per 

ton of paper. However, the installation of heat recovery systems will lead to more maintenance 

since heat exchangers require periodic cleaning. (Kramer 2009)

 Heat can also be recovered from the ventilation air of the drying section and used for 

heating of the facilities. For example, a mill-wide energy assessment found that the recovery of 

paper machine vent heat could be used for heating the plant in winter months. The estimated 

annual cost savings were about $1,000,000. With investment costs of about $1,500,000, the 

payback period was estimated at only 1.5 years (2002 dollars). (Kramer 2009) 

 For direct-fired air dryer hoods, which are mainly used on tissue and toweling machines, 

several opportunities for waste heat recovery exist. Hood exhaust air can be recovered and used 

to preheat the air entering the combustion chamber, thereby reducing hood fuel demand. A 

cascade system can be employed, which uses the hood exhaust air to feed the supply fan of the 

wet section, which will reduce the fuel demand for wet section burners. Lastly, an economizer 

can be installed to reclaim heat from hood exhaust air and use it to heat fresh water for highpressure showers of the paper machine felt and wires. (Kramer 2009) 

 CondeBelt drying. In CondeBelt drying, the paper is dried in a drying chamber by 

contact with a continuous hot steel band, heated by either steam or hot gas. The water from the 

paper is evaporated by the heat from this metal band. This drying technique has the potential to 

completely replace the drying section of a conventional paper machine, with a drying rate 5 to 15 

times higher than conventional steam drying. However, CondeBelt drying is not suited for high 

basis weight papers and has seen limited application in the U.S. to date (although it is operating 

in mills in Europe and Korea). Capital costs are considered to be high, although the size of the 

drying area can be reduced. One study estimated savings of 15 percent in steam consumption 

(1.5 MMBtu/ton of paper) and a slight reduction in electricity consumption (20 kWh/ton of 

paper), with investment costs of $28/ton paper (1998 dollars) for retrofit installations. (Kramer 

2009)

 Air impingement drying. Air impingement drying leads to less steam use and slightly 

higher electricity use. This technology is mostly applicable to coating drying but is also gaining 

acceptance for general paper drying in place of traditional steam cylinders. Published estimates 

suggest that impingement drying can lead to steam savings of 10 to 40 percent compared to 

conventional gas-fired or infrared drying technologies, but with an increased electricity use of up 

to 5 percent. (Kramer 2009)
 

40 

F. Energy Efficiency Improvements in Facility Operations

1. Energy Monitoring and Control Systems 

 Computerized/automated controls systems can be used to maintain operating conditions 

in the process at optimum levels. Many pulp and paper mills currently use modern process 

control systems, but those that do not could see energy and cost savings around 5 percent or 

more for many applications after installing these types of controls. (Kramer 2009) 

2. High-Efficiency Motors 

 Motor-driven systems are by far the most significant consumer of electrical energy in a 

typical U.S. pulp and paper mill. Motor-driven systems accounted for around 90 percent of all 

the electricity used by the industry. Due to the high use of motors at a pulp and paper facility, a 

systems approach to energy efficiency should be considered. Such an approach should look for 

energy efficiency opportunities for all motor systems (motors, drives, pumps, fans, compressors, 

controls). An evaluation of energy supply and energy demand should be performed to optimize 

overall performance. A systems approach includes a motor management plan that considers at 

least the following factors (Kramer 2009): 

• Motor management plan 

• Strategic motor selection 

• Maintenance 

• Proper size 

• Adjustable speed drives 

• Power factor correction 

• Minimize voltage unbalances 

 At one pulp and paper mill, energy efficient motors were an important part of a strategy 

to reduce electricity costs. By replacing its electric motors with premium-efficiency motors, the 

company was able to reduce its consumption of electricity per ton of paper by 35 percent. 

(Kramer 2009) 

 Motor management plans and other efficiency improvements can be implemented at 

existing facilities and should be considered in the design of new construction. 

3. Pumps 

 Pumps account for a significant share of motor-driven system electricity use in the U.S. 

pulp and paper industry. Pumps are used to pressurize and circulate water, process chemicals, 

and pulping slurries as part of the pulp and paper making process. Energy costs and operation 

and maintenance costs are the most important components in the lifetime costs of a pump 

system. Therefore, optimization of the design of a new pumping system should focus on 
 

41 

optimizing the lifecycle costs. Kramer 2009 listed the following factors that should be 

considered regarding pump system improvements: 

• Pump system maintenance 

• Pump system monitoring 

• Pump demand reduction 

• Controls 

• High-efficiency pumps 

• Properly sized pumps 

• Use of multiple pumps for variable loads 

• Adjustable-speed drives 

• Impeller trimming 

• Avoiding throttling valves 

• Replacement of belt drives 

• Proper pipe sizing 

• Precision castings, surface coatings, or polishing 

• Sealings 

• Curtailing leaking through clearance reduction 

 Optimization of the design of a pumping system has been shown to result in large 

reductions in energy use and lifetime costs of a complete pumping system, up to 10 to 17 percent 

in energy savings. (Kramer 2009) 

 At one mill, an over-sized pump was replaced with one of proper size, resulting in an 

energy savings of 2,450 megawatt-hours per year (MWh/yr). With an investment cost of 

$123,500, the payback period was 17 months. (Kramer 2009) 

4. High-Efficiency Fans 

 Fan technology has improved greatly since many older plants were constructed. Basic 

fan system improvements could save the U.S. pulp and paper industry around 1,100 GWh of 

electricity per year. (Kramer 2009) 

5. Optimization of Compressed Air Systems 

 Compressed air systems provide compressed air that is used throughout the mill. 

Although the total energy used by compressed air systems is small compared to the facility as a 

whole, there are opportunities for efficiency improvements that will save energy. Efficiency 

improvements are primarily obtained by implementing a comprehensive maintenance plan for 

the compressed air systems. Kramer 2009 listed the following elements of a proper maintenance 

plan: 

• Ongoing filter inspection and maintenance 

• Keep compressor motors properly lubricated and cleaned 

• Inspect fans and water pumps 

• Inspect drain traps 
 

42 

• Maintain the coolers 

• Check belts for wear 

• Replace air lubricant separators as recommended 

• Check water cooling systems 

• Minimize compressed air leaks throughout the system 

• Check applications requiring compressed air for excessive pressure, duration, or volume. 

 In addition to the maintenance plan, reducing leaks in the system can reduce energy 

consumption by 20 percent. Reducing the air inlet temperature will reduce energy usage, and 

routing the air intake to outside the building can have a payback period in 2 to 5 years. Control 

systems can reduce energy consumption by as much as 12 percent. Properly sized pipes can 

reduce energy consumption by 3 percent. Since as much as 93 percent of the electrical energy 

used by air compressor systems is lost as heat, recovery of this heat can be used for space 

heating, water heating, and similar applications. (Kramer 2009) 

 Air compressor system maintenance plans and other efficiency improvements can be 

implemented at existing facilities and should be considered in the design of new construction. 

6. Lighting System Efficiency Improvements 

 Similar to air compressor systems, the energy used for lighting at pulp and paper mills 

represent a small portion of the overall energy usage. However, there are opportunities for costeffective energy efficiency improvements. Automated lighting controls that shut off lights when 

not needed may have payback periods of less than two years. Replacing T-12 lights with T-8 

lights can reduce energy use by half, as can replacing mercury lights with metal halide or highpressure sodium lights. Substituting electronic ballasts for magnetic ballasts can reduce energy 

consumption by 12 to 25 percent. (Kramer 2009) 

 Lighting system improvements can be implemented at existing facilities and should be 

considered in the design of new construction. 

7. Process Integration Pinch Analysis 

Process integration can be an effective systems optimization approach to improve the 

energy efficiency of complex industrial facilities. Process integration is an analytical approach 

that can be used to optimize the selection and/or modification of processing steps, and of 

interconnections and interactions within the process, with the goal of minimizing resource use. 

Developed in the early 1970s, process integration is now an established methodology for 

improving the energy efficiency of continuous industrial processes. Pinch analysis is one of the 

most widely used process integration techniques. (Kramer 2009) 

Pinch analysis takes a systematic approach to identifying and correcting the 

performance-limiting constraint (or pinch) in any manufacturing process system. It was 

developed originally in response to the “energy crisis” and the need to reduce steam and fuel 

consumption in oil refineries and chemical plants by optimizing the design of heat exchanger 

networks. Since then, the pinch analysis approach has been extended to resource conservation in 
 

43 

general, whether the resource is capital, time, labor, electrical power, water, or a specific 

chemical species such as hydrogen. (Kramer 2009) 

The critical innovation in applying pinch analysis was the development of “composite 

curves” for heating and cooling, which represent the overall thermal energy demand and 

availability profiles for the process as a whole. When these two curves are drawn on a 

temperature-enthalpy graph, they reveal the location of the process pinch (the point of closest 

temperature approach), and the minimum thermodynamic heating and cooling requirements. 

These are called the energy targets. The pinch analysis methodology involves first identifying 

the targets and then following a systematic procedure for designing heat exchanger networks to 

achieve these targets. The optimum approach temperature at the pinch is determined by 

balancing capital and energy tradeoffs to achieve the desired payback. The procedure applies 

equally well to new designs and retrofits of existing plants. (Kramer 2009) 

Energy savings potential using pinch analysis far exceeds that from well-known 

conventional techniques such as heat recovery from boiler flue gas, insulation, and steam trap 

management. For example, one estimate indicates that pinch analyses can lead to energy savings 

of 10 to 35 percent in the pulp and paper industry. (Kramer 2009) 

Since the U.S. pulp and paper industry relies heavily on water, pinch analyses that are 

aimed at optimizing both energy and water use are ideal. Several case studies of the successful 

application of pinch analysis by pulp and paper companies are discussed below. (Kramer 2009) 

At one pulp and paper mill, a process integration analysis of the mill’s energy and water 

systems identified several heat recovery and wastewater reduction options. Pinch analysis was 

used to develop “hot” and “cold” composite curves for the entire mill. In addition to identifying 

all thermodynamically possible synergies between hot and cold systems, the pinch analysis also 

pinpointed inappropriate heat exchanges and ways to improve mill heat recovery. A total of 12 

projects were deemed feasible from this analysis, which were estimated to lead to a 15 percent 

reduction in the mill’s total fuel use. Additional benefits included the reduction in mill effluent. 

The payback period of these improvements was estimated at only ten months. (Kramer 2009) 

 At another pulp mill, a process integration study identified water and energy efficiency 

opportunities that focused on feed water preheating measures and cooling tower hot water 

streams displacement. Five priority projects were identified that would reduce energy 

consumption, while also reducing the use of fresh water by 10 percent. Capital expenditures for 

these projects were estimated at around $1.8 million, but the return on investment is expected to 

take only a little over one year. (Kramer 2009) 

 A third company also identified significant energy savings opportunities by using pinch 

analysis. Three heat recovery projects were identified that could reduce annual costs by about 

$4.8 million and annual natural gas use by 1,845,000 MMBtu. The overall payback period for 

these projects was estimated to be less than one year. At one of the company’s mills, a pinch 

analysis identified eight projects that could offer significant savings. It was estimated that 

annual steam savings of 718,972 MMBtu and annual natural gas savings of 10,483 MMBtu 

would be possible, with an overall payback period of around 2.75 years. (Kramer 2009) 
 

44 

G. Emerging Energy Efficiency Technologies 

1. Raw Material Preparation 

 Microwaving logs. By microwaving logs, the lignin in the wood can be softened, leading 

to lower energy requirements in the TMP process. Test results suggested that high-power 

microwave cooking of commercial black spruce for TMP could lead to energy savings of 15 

percent, with the added benefit of improved pulp quality. A tradeoff is that, with microwaving, 

more bleaching may be required to receive the desired paper quality; however, increased 

bleaching costs may be justified by the energy and quality improvements. Initial estimates of 

capital costs for 20-kilowatt (kW) and 50-kW systems range from $7.5 to $12.5 million (2002 

dollars). (Kramer 2009) 

 Biotreatment. The treatment of wood chips with a fungus or enzymes can soften the 

bonds in wood, resulting in less energy use in pulping processes. The results of a pilot project in 

which the biopulping process for treating wood chips prior to mechanical pulping were scaled up 

to a 50-ton, semi-commercial scale. The economic advantages of biomechanical pulping derive 

from several effects, including significantly improved strength properties and significantly 

reduced refiner energy requirements (about 33 percent less energy use for refining). (Kramer 

2009)

 The physical process begins after the pulpwood has been chipped and screened for 

oversize chips. At this point, the chips are briefly heated to 100oC to kill off anything that might 

compete with the lignin-degrading fungus. The chips are then air-cooled, and the fungus and the 

nutrients are added. The treated chips are placed in a pile for the next 1 to 4 weeks: climatic and 

seasonal factors are very important for the effectiveness of the treatment. The fact that up to four 

weeks worth of chips must be stored may be a problem for mill sites with space constraints. This 

technology is reportedly ready for commercial deployment, but no data could be found on the 

extent to which this technology has been adopted by U.S. pulp and paper mills. (Kramer 2009)

2. Chemical Pulping 

 Black liquor gasification. Kraft mills combust black liquor in so-called Tomlinson 

recovery furnaces to recover pulping chemicals and generate process steam and on-site 

electricity (via a steam turbine). The efficiency of such furnaces is typically low, around 65 to 

70 percent. An alternative to using a recovery furnace is an emerging process known as black 

liquor gasification. Black liquor gasification refers to the process of creating a clean synthesis 

gas (syngas) from black liquor by converting its biomass content into a gaseous energy carrier. 

The syngas can be used in boilers or in combined cycle processes to generate on-site electricity 

and process steam. (Kramer 2009) 

 Black liquor gasifiers may be applied as an incremental addition in chemical recovery 

capacity in situations where the recovery furnace is a process bottleneck. There is also 

increasing interest in using gasifiers in combined cycle power systems as replacements for 
 

45 

Tomlinson recovery furnace systems, to provide fuel for lime kilns, and even for transport fuels 

such as Fischer-Tropsch liquids or hydrogen. (Kramer 2009) 

 The black liquor gasification process may be implemented through one of two systems. 

Both high- and low-temperature mill-scale gasification systems are able to produce syngas and 

assist in recovering pulping chemicals. Both systems have the capacity to create similar end 

products (i.e., syngas and pulping chemicals) but differ from each other and from the Tomlinson 

recovery process in the resulting gasified black liquor chemical compositions. Low-temperature 

gasification tends to produce a sulfur-lean smelt and results in approximately 90 percent of the 

total sulfur components leaving in the syngas when compared to the Tomlinson recovery 

furnace. High-temperature gasification has a similar affect on sulfur loss but the effect is not as 

pronounced. (Kramer 2009) 

 

The potential advantages of black liquor gasification are the greater end-use flexibility 

offered by a gaseous fuel, reduced air pollutant content, and higher electricity-to-heat ratios in 

combined cycle systems than standard recovery furnace steam turbine systems. The secondary 

fuel source will offer the opportunity to eliminate the dependency of grid purchased power and 

produce additional power to sell back. Also, gasification is expected to reduce emissions of SO2, 

NOX, CO, volatile organic compounds (VOCs), PM, CH4, HAP, and TRS and wastes (i.e., water, 

solids, and coal use) generally associated with power production. (Kramer 2009) 

Some potential disadvantages of gasification combined cycle systems include higher lime 

kiln and causticizer loads (and associated fuel inputs) compared to Tomlinson systems, the 

overall installation cost, and the steam demand to operate (and associated fuel inputs). The 

sulfur loss that occurs in black liquor gasification subsequently increases the amount of Na2CO3

in the smelt. This higher concentration of Na2CO3 requires additional lime kiln and causticizer 

loads to convert the Na2CO3 back to NaOH needed for pulping. The additional causticizing 

capacity directly contributes to the installation cost, due to the need to improve or replace the 

current lime kiln. Additionally, since combined cycle systems generate electrical power more 

efficiently than steam turbine-based systems, more fuel is required in the gasification combined 

cycle system than in the Tomlinson boiler system to meet the same level of facility steam 

demand. However, this additional fuel use also results in more available electricity for facility 

use or export to the grid. (Kramer 2009) 

 At least one study (Larson 2003) has comprehensively analyzed the potential for black 

liquor gasification accompanied by combined cycle electricity generation at pulp and paper mills 

in the U.S. The study analyzed the various tradeoffs of different gasification and Tomlinson 

boiler co-generation systems under different assumptions. The study results suggest that, on a 

thermodynamic basis, high-efficiency Tomlinson boiler systems would be more efficient at 

generating steam and power than low-temperature mill-scale gasification systems. However, the 

study results also suggested that high-temperature mill-scale gasification systems would be more 

efficient than high-efficiency Tomlinson boiler systems. The study estimated total installed 

capital costs (including causticizing area upgrades) for a 6 million pound of black liquor solids 

per day (lb BLS/day) gasification unit to be $234 million for a low-temperature system and $194 

million for a high-temperature system (2002 dollars). (Larson 2003) 

 Directed green liquor utilization pulping. This technology is based on the use of green 

liquor for pretreatment of wood chips prior to pulping. Green liquor is naturally rich in 
 

46 

hydrosulfide ions, which can accelerate pulping. The use of green liquor in this manner has been 

demonstrated in pulp mills in Finland and can reportedly increase pulp yields, produce higher 

fiber strength, reduce digester alkali demand by as much as 50 percent, offload the lime kiln by 

up to 30 percent, provide higher pulp bleachability, and reduce energy use by up to 25 percent. 

As of 2006, this technology was being demonstrated at a mill in the U.S. and was expected to be 

commercialized shortly. (Kramer 2009) 

Biomass gasification. Biomass (wood) gasification systems for generating power at pulp 

mills are also under development. Biomass gasification would produce a syngas fuel from the 

gasification of wood residuals. This biogenic syngas could then be used to replace the fossil 

fuels currently being burned in lime kilns, power boilers, or other combustion devices. 

3. Pulp Washing 

 Steam cycle washer for unbleached pulp. According to the U.S. DOE, current U.S. pulp 

washing equipment has an average age of 45 years. Thus, significant energy saving 

opportunities may exist with the development and adoption of new, more efficient pulp washing 

technologies. The U.S. DOE is sponsoring the development of a new steam cycle washer that is 

designed to de-water and wash wood pulp using counter-current washing, steam, and highdifferential pressure. Reportedly, the technology uses 70 to 75 percent less water than 

conventional washers because it allows the pulp mat to be washed at a high consistency of 28 to 

32 percent. This results in less energy consumption, up to a 21 percent decrease in electrical 

power consumption and up to a 40 percent decrease in fuel use for unbleached pulp production. 

This technology is currently undergoing demonstration and commercialization. (Kramer 2009)

4. Secondary Fiber Processing 

 Electrohydraulic contaminant removal. Adhesive materials on secondary fiber feedstock 

can significantly degrade the quality of recycled paper products. A demonstration project 

sponsored by the U.S. DOE indicated that a new contaminant removal technology that is based 

on the principle of electrohydraulic discharge may remove such contaminants effectively and in 

an energy efficient manner. The technology uses the discharge of sparks in cleaning and 

screening processes to enhance the removal efficiency of adhesive materials in screening and 

cleaning and to increase the efficiency of flotation deinking. Trials have been run at several 

mills. One study reported that improved adhesive material removal, flotation, and clarification 

were observed that could lead to direct energy use reductions of 10 to 15 percent in contaminant 

removal and cleaning equipment. (Kramer 2009)

5. Papermaking 

 Laser-ultrasonic web stiffness sensor. A laser-ultrasonic sensor has been developed 

which measures a paper's bending stiffness and shear strength as it speeds through a production 

web. The laser-ultrasonic sensor measures these important mechanical properties in real time, 

which can allow paper manufacturers to optimize the amount of raw material used to make paper 
 

47 

by running closer to specifications. Reportedly, this could save approximately $200 million in 

energy costs and $330 million in fiber costs each year in the U.S. 

 The technology has been proven in a full-scale mill trial, and is currently being evaluated 

in a larger pilot study. At the mill scale, it is estimated that implementation of this technology 

could lead to a 2 percent decrease in basis weight due to the ability of running closer to 

specification. Furthermore, the portion of off-grade paper that must be recycled could be 

reduced by 1 percent (which avoids the additional energy necessary to reprocess the recycled 

fiber in the mill). In total, mill-scale energy savings of 3 percent have been estimated. (Kramer 

2009) 

 Advanced fibrous fillers. Mineral fillers are commonly used to replace wood fibers in the 

production of paper products, but filler loading is currently limited to roughly 15 to 20 percent 

due to paper strength and quality requirements. New inorganic fibrous fillers have been 

developed that could raise the filler loading limit to up to 50 percent, while maintaining paper 

strength and quality in many products. Reportedly, the use of fillers could reduce energy 

consumption by 25 percent and costs by $10 to $50 per ton of paper produced (2006 dollars). 

Energy savings are attributable to avoided wood pulp production and reduced drying energy due 

to an increase in the percentage of press solids in the sheet. Mill-scale production trials of this 

technology are underway. (Kramer 2009) 

 Lateral corrugators. The lateral corrugator holds promise for reducing the fiber use and 

energy consumption associated with the manufacture of corrugated boxes. The lateral corrugator 

is designed to increase the compression strength of corrugated containers by aligning the 

corrugated flutes with the orientation of the linerboard fibers (i.e., the paper machine direction). 

This change reportedly increases the compressive strength of corrugated boxes by up to 30 

percent and may allow manufacturers to use 15 percent less fiber to produce boxes with the same 

strength. Significant energy savings should be possible due to the reductions in raw materials 

preparation, pulping, and paperboard making energy attributable to reduced fiber input. (Kramer 

2009)

6. Paper Machines – Drying Section 

 Impulse drying. Impulse drying may lower the moisture content of the paper web 

entering the drying section by up to 38 percent, thereby significantly lowering the energy 

required in the paper machine’s drying stage. Impulse drying involves pressing the paper 

between one very hot rotating roll (150 to 500°C) and a static concave press with a very short 

contact time. The pressure is about 10 times higher than that in press and CondeBelt drying. 

Potentially, energy savings can be significant. One estimate placed the potential savings in 

drying steam consumption at 50 to 75 percent. Another description of impulse drying claims 

energy savings of about 18 to 20 percent or 2 MMBtu/ton of paper. Electricity requirements do 

increase, however, by 5 to 10 percent. Other reported benefits of this technology include 

reduced capital costs, increased machine productivity, improved strength, reduced fiber use, and 

increased recycled fiber content allowed for any given paper strength. However, current results 

from pilot operations show limited energy efficiency improvements when compared to state-ofthe-art efficient paper machines. (Kramer 2009)
 

48 

 Gas-fired paper dryer. The gas-fired dryer system uses small dimples or cavities for 

combustion in a cylinder dryer, which can replace current steam dryers whose productivity is 

limited by drying capacity. The technology significantly raises drum temperatures (to over 

600°F), thereby increasing drying rates, which can reportedly reduce energy use and increase the 

throughput of the paper machine by an estimated 10 to 20 percent. A key contributor to 

increased efficiency is the fact that diffusion firing allows high levels of heat recovery to preheat 

combustion air. (Kramer 2009)

 Multi-port dryer. A new multi-port cylinder dryer has been developed that can reportedly 

increase paper production rates by 50 percent relative to conventional dryers and by 20 percent 

relative to dryers fitted with so-called “spoiler bars.” Conventional steam-filled drying cylinders 

develop condensate on the inside of the drum, which is a major thermal barrier. The new multiport cylinder dryer uses smaller-sized ports located in close proximity to the inside surface of the 

cylinder dryer, which improves heat transfer by significantly minimizing the condensate layer 

thickness and increasing the surface temperature of the dryer shell. This technology is reportedly 

being designed for retrofit applications and is projected to cost only 20 percent as much as the 

installation of a new dryer cylinder. The multi-port dryer is currently undergoing pilot 

demonstration. (Kramer 2009) 

7. Facility Operations - Motors 

 Magnetically-coupled adjustable-speed drives. Magnetically-coupled adjustable-speed 

drives (MC-ASDs) are a new type of ASD, in which the physical connection between the motor 

and the driven load is replaced with a gap of air. Torque is generated by the interaction of rareearth magnets on one side of the drive with induced magnetic fields on the other side. The 

amount of torque transferred is controlled by varying the air gap distance between the rotating 

plates in the assembly. Compared to existing ASDs, MC-ASDs have several advantages, 

including: (1) a greater tolerance for motor misalignment; (2) little impact on power quality; 

(3) the ability to be used with regular duty motors (instead of inverters); (4) expected lower longterm maintenance costs; and (5) extended motor and equipment lives, due to elimination of 

vibration and wear on equipment. (Kramer 2009)

 One mill opted to install MC-ASDs to reduce wasted energy in the pumping of TMP 

whitewater to its pulping process and de-inking system. The old constant-speed pump ran at full 

capacity during normal operations, which resulted in cavitation and excessive vibration, leading 

to maintenance problems. Further, a bypass valve was used to maintain constant pressure in the 

system when there was no demand for TMP whitewater, which led to significant energy waste. 

The MC-ASD was installed in this application instead of an ASD due to its lower installation and 

infrastructure costs. The coupling allowed the mill to vary the speed of its pump motor to 

maintain the required pressure but with an energy demand that was around 60 percent lower than 

the former constant-speed, bypass-valve based system. Annual energy costs were reduced by 

around $19,000 (2002 dollars), cavitation was eliminated, and pump vibration was dramatically 

reduced. (Kramer 2009) 

 In a similar case study, a MC-ASD was installed in a pumping application at a mill. The 

mill had 100–hp, 1175–revolutions per minute (rpm) motors operated in parallel running vertical 

shaft pumps to move wastewater from the main pump station to a clarifier. These two pumps ran 
 

49 

constantly to meet a maximum flow rate of 7,000 gal/min; however, the average demand was 

only 4,800 gal/min, which meant that 2,200 gal/min was passed through an energy wasting 

bypass valve. The MC-ASDs were installed on the two pumps as a lower-cost alternative 

compared to ASDs. The MC-ASDs allowed the mill to maintain its 4,800 gal/min flow, while 

reducing electricity demand from 142 to 62 kW, a savings of 56 percent. Reportedly, the 

couplings also eliminated damaging vibration and water hammer, resulting in equipment and 

maintenance cost savings of approximately $15,000 per year (2002 dollars). (Kramer 2009) 
 

50 

IV. Energy Programs and Management Systems 

Industrial energy efficiency can be greatly enhanced by effective management of the 

energy use of operations and processes. EPA’s ENERGY STAR Program works with hundreds 

of U.S. manufacturers and has seen that companies and sites with stronger energy management 

programs gain greater improvements in energy efficiency than those that lack procedures and 

management practices focused on continuous improvement of energy performance. Energy 

management practices and system elements can be considered as part of work practice 

requirements established under permitting conditions. 

Energy Management Systems (EnMS) provide a framework managing energy and 

promote continuous improvement. The EnMS provides the structure for an energy program and 

its energy team. EnMS establish assessment, planning, and evaluation procedures which are 

critical for actually realizing and sustaining the potential energy efficiency gains of new 

technologies or operational changes. 

Energy management systems promote continuous improvement of energy efficiency 

through: 

• Organizational practices and policies, 

• Team development 

• Planning and evaluation, 

• Tracking and measurement, 

• Communication and employee engagement, and 

• Evaluation and corrective measures. 

For nearly 10 years, the EPA’s ENERGY STAR Program has promoted an energy 

management system approach. This approach, outlined in the graphic below, outlines the basic 

steps followed by most energy management systems approaches. 

In recent years, interest in energy management system approaches has been growing. 

There are many reasons for the greater interest. These include recognition that a lack of 

management commitment is an important barrier to increasing energy efficiency. Further, lack 

of an effective energy team and program result in low implementation rates for new technologies 

or recommendations from energy assessments. Poor energy management practices that fail to 

monitor performance do not ensure that new technologies and operating procedures will achieve 

their potential to improve efficiency. 

Approaches to implementing energy management systems vary. EPA’s ENERGY STAR 

Guidelines for Energy Management are available for public use on the web and provide 

extensive guidance (see: www.energystar.gov/guidelines). Alternatively, energy management 

standards are available for purchase from American National Standards Institute (ANSI), ANSI 

MSE 2001:200 and in the future from International Organization for Standardization (ISO), ISO 

50001. See Figure 3. 
 

51 

Figure 3 - ENERGY STAR Guidelines for Energy Management 

 (www.energystar.gov/guidelines) 

While energy management systems can help organizations achieve greater savings 

through a focus on continuous improvement, they do not guarantee energy savings or CO2

reductions alone. Combined with effective plant energy benchmarking and appropriate plant 

improvements, energy management systems can help achieve greater savings. 

There are a variety of factors to consider when contemplating requiring certification to an 

Energy Management Standard established by a standards body such as ANSI or ISO. First, 

energy management system standards are designed to be flexible. A user of the standard is able 

to define the scope and boundaries of the energy management system so that single production 

lines, single processes, a plant, or a corporation could be certified. Beyond scope, achieving 

certification for the first time is not based on efficiency or savings (although re-certifications at a 

later time could be). Finally, cost is an important factor in the standardized approach. Internal 

personnel time commitments, external auditor, and registry costs are expensive. 

From a historical perspective, few companies have pursued certification according to the 

ANSI energy management standards to date. One reason for this is that the elements of an 

energy management system can be applied without having to achieve certification, which adds 

additional costs. The ENERGY STAR Guidelines and associated resources are widely used and 

adopted partly because they are available in the public domain and do not involve certification. 

Overall, a systems approach to energy management is an effective strategy for 

encouraging energy efficiency in a facility or corporation. The focus of energy management 

efforts are shifted from a “projects” to a “program” approach. There are multiple pathways 

available with a wide range of associated costs (ENERGY STAR energy management resources 

are public, while the standardized approaches are costly). The effectiveness of an energy 

management system is linked directly to the system’s scope, goals, and measurement and 
 

52 

tracking. Benchmarks are the most effective measure for demonstrating the system’s 

achievements. 

A. Sector-Specific Plant Energy Performance Benchmarks 

Plant energy benchmarking is the process of comparing the energy performance of one 

site against itself over time or against the range of performance of the industry. Plant energy 

benchmarking is typically done at a whole-facility or site level in order to capture the synergies 

of different technologies, operating practices, and operating conditions. 

Benchmarking enables companies to set informed and competitive goals for plant energy 

improvement. Benchmarking also helps companies prioritize where to make investment to 

improve performance of poor performers, while learning from the approaches used by top 

performers. 

When benchmarking is conducted across an industrial sector, a benchmark can be 

established that defines best-in-class energy performance. The EPA’s ENERGY STAR Program 

has developed benchmarking tools that establish best-in-class for specific industrial sectors. 

These tools, known as Plant Energy Performance Indicators (EPI) are established for specific 

industrial sectors and available for free at www.energystar.gov/industrybenchmarkingtools. 

Using several basic plant-specific inputs, the EPIs calculate a plant’s energy performance, 

providing a score from 0 to 100. EPA defines the average plant within the industry nationally at 

the score of 50; energy-efficient plants score 75 or better. ENERGY STAR offers recognition 

for sites that score in the top quartile of energy efficiency for their sector using the EPI. 

As of July 2010, ENERGY STAR had developed two EPIs for the pulp and paper sector. 

These include a Pulp Mill EPI and an integrated Pulp and Paper Mill EPI. The integrated Pulp 

and Paper Mill EPI is applicable to mills that manufacture products in specific product 

categories. EPA is evaluating the development of further EPIs for other mill configurations, 

such as recycled fiber mills, tissue mills, etc. 

B. Industry Energy Efficiency Initiatives 

The U.S. EPA’s ENERGY STAR Program (www.energystar.gov/industry) and U.S. 

DOE’s Industrial Technology Program (www.energy.gov/energyefficiency) have lead industry 

specific energy efficiency initiatives over the years. These programs have helped to create 

guidebooks of energy efficient technologies, profiles of industry energy use, and studies of future 

technologies. Some states have also lead sector-specific energy efficiency initiatives. Resources 

from these programs can help to identify technologies that may help reduce CO2 emissions. 
 

53 

EPA Contacts 

Bill Schrock 

U.S. EPA 

OAQPS/SPPD/NRCG 

Mail Code E143-03 

Research Triangle Park, NC 27711 

Phone: 919-541-5032 

Fax: 919-541-3470 

schrock.bill@epamail.epa.gov
 

54 

References 

AF&PA 2008. Memorandum from Rhea Hale, AF&PA, to Reid Harvey, U.S. EPA Climate 

Change Division. May 22, 2008. 

AF&PA 2010. Paper and Paperboard Recovery Rate. 

http://paperrecycles.org/stat_pages/stat_intro.html Accessed June 17, 2010. 

EPA 1995. Compilation of Air Pollutant Emission Factors, Volume 1: Stationary Point and 

Area Sources, AP-42, Fifth Edition, Chapter 10.2. U.S. Environmental Protection Agency. 

Research Triangle Park, NC. January 1995. 

http://www.epa.gov/ttn/chief/ap42/ch10/final/c10s02.pdf

EPA 2001a. Pulp and Paper Combustion Sources National Emission Standards for Hazardous 

Air Pollutants: A Plain English Description. U.S. Environmental Protection Agency. EPA456/R-01-003. September 2001. http://www.epa.gov/ttn/atw/pulp/chapters1-6pdf.zip

EPA 2001b. Pulping and Bleaching System NESHAP for the Pulp and Paper Industry: A Plain 

English Description. U.S. Environmental Protection Agency. EPA-456/R-01-002. September 

2001. http://www.epa.gov/ttn/atw/pulp/guidance.pdf

EPA 2002. Profile of the Pulp and Paper Industry, 2nd Edition. EPA Office of Compliance 

Sector Notebook Project. U.S. Environmental Protection Agency. EPA/310-R-02-002. 

November 2002. 

http://www.epa.gov/compliance/resources/publications/assistance/sectors/notebooks/pulppasnp1.

pdf

EPA 2009a. Technical Support Document for the Landfill Sector: Proposed Rule for Mandatory 

Reporting of Greenhouse Gases. Office of Air and Radiation, U.S. Environmental Protection 

Agency. February 4, 2009. http://www.epa.gov/climatechange/emissions/archived/ghg_tsd.html

EPA 2009b. Technical Support Document for Wastewater Treatment: Proposed Rule for 

Mandatory Reporting of Greenhouse Gases. Office of Air and Radiation, U.S. Environmental 

Protection Agency. February 4, 2009. 

http://www.epa.gov/climatechange/emissions/archived/ghg_tsd.html

EPA 2009c. Technical Support Document for the Pulp and Paper Sector: Proposed Rule for 

Mandatory Reporting of Greenhouse Gases. Office of Air and Radiation, U.S. Environmental 

Protection Agency. February 11, 2009. 

http://www.epa.gov/climatechange/emissions/archived/ghg_tsd.html

EPA 2010a. Available and Emerging Technologies for the Control of Greenhouse Gas 

Emissions from Industrial, Commercial, and Institutional Boilers. Office of Air and Radiation, 

U.S. Environmental Protection Agency. 
 

55 

EPA 2010b. Information Collection Request for Pulp and Paper Sector New Source 

Performance Standards and National Emission Standards for Hazardous Air Pollutants Residual 

Risk and Technology Review. EPA/OAQPS/SPPD. May 27, 2010. 

ICF 2010. CHP Installation Database. Maintained for the U.S. Department of Energy and Oak 

Ridge National Laboratory. http://www.eea-inc.com/chpdata/index.html

ICFPA 2005. Calculation Tools for Estimating Greenhouse Gas Emissions from Pulp and 

Paper Mills. Version 1.1. July 8, 2005. Prepared by the National Council for Air and Stream 

Improvement for The Climate Change Working Group of The International Council of Forest 

and Paper Associations (ICFPA). Accessed at http://www.ghgprotocol.org/calculationtools/pulp-and-paper

Kramer, K., et al. 2009. Energy Efficiency Improvement and Cost Saving Opportunities for the 

Pulp and Paper Industry (Report No. LBNL-2268E), Ernest Orlando Lawrence Berkeley 

National Laboratory, Berkeley, CA. October 2009. 

http://www.energystar.gov/ia/business/industry/downloads/Pulp_and_Paper_Energy_Guide.pdf

Larson, E., et al. 2003. A Cost-Benefit Assessment of Biomass Gasification Power Generation in 

the Pulp and Paper Industry, Final Report, Navigant Consulting, Inc., Princeton University and 

Politecnico di Milano. October 8, 2003. 

http://www.princeton.edu/pei/energy/publications/texts/BLGCC_FINAL_REPORT_8_OCT_200

3.pdf

McCubbin, N. 1996. “Numerous Recovery Options Offer Solutions for Mill Effluent Closure.” 

Pulp & Paper Magazine. March 1, 1996. 

http://www.risiinfo.com/db_area/archive/p_p_mag/1996/9603/96030131.htm. 

NCASI 2008a. The Greenhouse Gas and Carbon Profile of the U.S. Forest Products Sector. 

National Council for Air and Stream Improvement. Special Report No. 08-05. September 2008. 

http://www.ncasi.org//Publications/Detail.aspx?id=3108

NCASI 2008b. Memorandum from Reid Miner, NCASI, to Becky Nicholson, RTI International. 

Calculations Documenting the Greenhouse Gas Emissions from the Pulp and Paper Industry. 

May 21, 2008. 

Staudt, J. 2010. Memorandum from Jim Staudt, Andover Technology Partners, to Will 

Yelverton, Matt Witosky, and Elineth Torres, U.S. EPA, and Katie Hanks, RTI International. 

ISIS Emissions Control for Pulp and Paper Plants. March 3, 2010.