Amanda Singleton - Bagasse Boiler Proposed Subcategory 

 

Jim and Amanda, please see the attached document which further supports bagasse boilers as a class of boilers 

that should be afforded a separate subcategory under the new boiler MACT rules. I am also FedExing a hardcopy 

to you. Once you have had a chance to review this information, please call me if you have any questions or need 

further information. As always, we are available to meet with you at any time to discuss this request. We will be 

submitting to you’re a bagasse Boiler MACT floor analysis within the next week. Thanks again for your help and 

support. 

David A. Buff, P.E., Q.E.P. | Principal Engineer | Golder Associates Inc. 

6026 NW 1st Place, Gainesville, Florida, USA 32607 

Tel: +1 (352) 336-5600 ext. 21145 Fax: +1 (352) 336-6603 | Cell: +1 352 514-5600 | 

E: dbuff@golder.com | www.golder.com 

Work Safe, Home Safe 

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Please consider the environment before printing this email. 

 

 

From: "Buff, Dave" <DBuff@GOLDER.com>

To:

 

"Eddinger.Jim@epamail.epa.gov" <Eddinger.Jim@epamail.epa.gov>, 

AmandaSingleton <Amanda.Singleton@erg.com>

Date: 5/14/2009 6:18 PM

Subject: Bagasse Boiler Proposed Subcategory

CC: GNV- Document Production <GNV-DocumentProduction@golder.com>

Attachments: Boiler MACT-WhitePaper2.pdf

Page 1 of 1

file://C:\Documents and Settings\JONeil\Local Settings\Temp\XPgrpwise\4A0C6059Dom-MorPO1-...
Bagasse Boilers Should be Regulated in a Separate Subcategory 

under the Boiler MACT Rules 

Because they are a Unique Class of Boilers 

Submitted by the Florida Sugar Industry1

May 14, 2009 

I. Introduction

The U. S. Environmental Protection Agency (EPA) is currently developing new Boiler MACT rules that 

will regulate many types of industrial boilers, including the bagasse boilers operated by the Florida Sugar 

Industry. Accordingly, the Florida Sugar Industry is providing this white paper to EPA to explain why

(a) bagasse boilers constitute a unique class of industrial boilers, and (b) bagasse boilers should be placed in 

a separate subcategory under the new Boiler MACT rules. 

Bagasse boilers exhibit several distinctive design, operating, and emissions characteristics when burning 

bagasse. These characterisitcs can be summarized as follows: 

(a) Bagasse is a unique fuel, with high moisture content and low density; 

(b) Bagasse boilers are uniquely designed and operated to burn bagasse; and 

(c) Bagasse boilers are fully integrated with sugar mill and the other boilers at the mill. 

When these characteristics are considered together, it is clear that bagasse boilers constitute a unique class 

of industrial boilers. Consequently, bagasse boilers should be regulated in a separate subcategory under the 

new Boiler MACT rules. This subcategory should not include other types or classes of boilers (e.g., boilers 

that burn other types of biomass or fossil fuel). 

Bagasse is produced when a sugar mill is extracting sugar from sugarcane. Bagasse is the wet fibrous 

material remaining after the sugarcane has been cut, ground, and repeatedly washed and pressed to recover 

as much sucrose as possible. Since the very beginning of its operations in the United States, the sugar 

producing industry has used bagasse as the primary fuel for its boilers. Bagasse boilers are specifically 

designed to dry and burn the bagasse in one unit, and the boilers are wholly integrated into the operations of 

the sugar mills. As bagasse is produced in the milling process, it is fed directly into the boilers, where the 

bagasse is dried and burned. In a typical integrated sugar mill, the burning of the bagasse generates enough 

heat to produce the steam and electricity needed to power the operation of the sugar mills. 

Many times in the past, EPA has created various subcategories in rulemaking under the Clean Air Act 

(CAA) because EPA has recognized that a facility’s emissions can be significantly affected by the 

facility’s fuel, design, size, age, and use. When establishing the upcoming Boiler MACT rules, EPA has 

the statutory authority pursuant to Section 112 of the CAA to create subcategories based on “classes, 

types, or sizes” of industrial boilers. 

 

1 The Florida Sugar Industry is comprised of sugarcane processors located in south Florida. These processors 

harvest sugarcane to produce raw and/or refined sugar. The FSI operates industrial boilers fired primarily by 

bagasse, which is a co-product of the sugarcane processing operations. Wood and other agricultural materials, as 

well as very limited amounts of fossil fuel, may also be burned in the FSI’s boilers. The FSI also is coordinating the 

submittal of this paper with a sugarcane processor located in Hawaii. 
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EPA should create a subcategory for bagasse boilers because these boilers constitute a distinct class.

Their design and operation sets them apart from other solid fuel boilers. Their unique characteristics 

significantly affect the boilers’ emissions. Bagasse also has distinctive characteristics that affect the 

boilers’ emissions. Creating a subcategory for bagasse boilers, based on the class of boilers or fuel type, 

will help ensure that the MACT emissions standards for bagasse boilers are based on the performance of

“similar sources,” as required by the CAA. Conversely, EPA would not be able to establish an 

appropriate MACT floor for bagasse-fired boilers if bagasse boilers were regulated in a MACT category 

that includes other types or classes of solid fuel-fired or biomass boilers. 

II. Background Information on Sugarcane and Sugarcane Processing 

The following discussion summarizes some basic information about sugarcane, sugarcane processing, 

bagasse, and bagasse boilers. Sugarcane is a member of the grass family, and is grown in numerous 

countries around the world, including the United States, China, India, Cuba, Venezuela, Indonesia, 

Australia, and many more. The cane grows year round, but typically the harvesting and milling 

operations occur over just a few months. In the U.S., the sugar mills typically run 24 hours per day 

during the milling season. The milling operations usually are completed in 3 to 4 months in Louisiana, 

4 to 6 months in Florida, and 9 months in Hawaii. 

The tops of the sugarcane plants and most of the leaves are removed in the field and then the cane is 

brought to the mills in large trailers by truck or railcar. The typical composition of the sugarcane is 

presented in Table 1, below. 

Table 1. Typical Sugarcane Composition (from various literature sources)

 Water 75% 

 Sugars 12% (mostly sucrose, with some glucose & fructose) 

 Fiber/Pith 12% (mostly cellulose, with some lignins) 

 Other 1 to 2% (mostly salts and soil minerals, with some organic compounds) 

In the sugar mill, the cane is first cut into smaller pieces.2 Next the sugarcane is subjected to grinding 

and washing, which may occur 4 to 8 times in a sugar mill “tandem.” This process extracts as much of 

the sugarcane juices (primarily sucrose) as possible from the cane. This process also removes some, but 

not all, of the soil that may be clinging to the cane (carried in from the fields). The sugarcane juices are 

then clarified and evaporated to produce raw sugar crystals. 

Bagasse is the traditional name given to the cellulosic fiber and pith that remain after the sucrose juice has 

been extracted from a sugarcane stalk during the milling process. The composition of the biomass is 

changed in this process of producing bagasse from sugarcane. The typical composition of bagasses is 

shown in Table 2. 

 

Table 2. Typical Bagasse Composition

 Water 48 to 55% 

 Sugars 1 to 2% 

 Fiber/Pith 44 to 50% 

 Other 1 to 4% 

 

2

 In Hawaii, but not Florida, the cane is washed in a cane “cleaner” prior to cutting. The cleaner is used to remove 

some of the extraneous soil that adheres to the cane when it is brought in from the fields. 
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The heat needed to operate the evaporators in the sugar production process, and the power needed to 

operate the mill equipment, are obtained by burning the bagasse in boilers that are specifically designed 

for the simultaneous drying and combustion of bagasse. The design of a sugar mill always includes the

complete integration of the bagasse-burning boilers with the rest of the mill. The bagasse generated in 

the mill is normally sent directly to the boilers as fuel. The boilers produce steam, which in turn is used 

in the mill. The steam also is used in steam turbine generators to produce electricity for the mill’s

internal consumption. In some locations, excess electricity is fed back into the local power grid. 

III. Design and Operation of Bagasse Boilers 

The design and operation of bagasse boilers differs significantly from other solid fuel boilers (even other 

biomass boilers). First, because bagasse contains about 50% moisture, it must be dried before it can be 

burned. This is accomplished in boilers specifically designed for this task. The bagasse typically is 

conveyed directly from the mill to the boiler and then is dropped into chutes and fed into the boilers by 

means of fuel distributors. The distributors inject air at the point where the bagasse is introduced into the 

boiler in order to spread the baggase over the boiler width. The drying (and much of the combustion) 

occurs while the material is suspended in air. Hence, they are often called “suspension” boilers. 

However, some of the bagasse is not burned completely and falls to the grate or floor below, where the

combustion continues. Accordingly, many bagasse boilers have grates of various types, which allow 

additional air to mix with the fuel and thus enhance the combustion. For this reason, many bagasse 

boilers can also be called “stoker” boilers. In reality, bagasse boilers utilize a combination of suspension 

firing and grate firing, and that affects the performance of the boilers. 

Bagasse boilers almost universally are designed to have high heat release rates ([all except one above

22,800 British thermal units per hour per cubic foot (Btu/hr-ft3

)]. These high heat release rates are 

needed to quickly dry the wet bagasse as it is blown into the boilers. Despite the high heat release rates, 

the combustion temperatures are considerably lower than in other classes of boilers, due mainly to the

wet nature of the fuel. The high heat release rates means shorter residence times for flue gases. 

Consequently, even though bagasse is a very clean fuel with respect to metals, sulfur and chlorine, the 

wet bagasse and the shorter residence times in the boiler result in an incomplete burn out of carbon 

monoxide (CO). As a result of these factors, the concentrations of CO in the furnace gases can be very 

high in comparison with the CO emissions from other classes of boilers. Conversely, the lower 

temperature in the furnace results in significantly lower NOx emissions compared with other classes of 

boilers. 

Normally, bagasse generated in the mill is fed directly to the boilers, without any intermediate storage. 

No blending or further processing of the bagasse takes place prior to combustion in the boilers. This

characteristic of bagasse boilers differs from other biomass-fired boilers. Because the boilers receive the 

bagasse as it is produced, the performance of the boilers can be adversely affected when there is 

variability in the moisture content or other characteristics of the bagasse being produced by the sugar 

mill. Since the moisture content of the bagasse often fluctuates significantly, there often is considerable 

variability (minute-to-minute and hour-to-hour) in the CO concentrations and emissions from bagasse 

boilers. 

All of the mill’s boilers are tied into a single steam header, which provides high-pressure steam to the 

sugar mill tandems that grind the sugarcane. The integrated operations of the boilers and the sugar mill 

tandems is a unique feature of sugar mills. High-pressure steam is also provided to steam turbine 

electrical generators, and low pressure steam is provided to the raw sugar manufacturing process. 

Because all of the operations are integrated (i.e., linked together), the boilers’ emission rates are affected 
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by mill steam demand, mill upsets, startups/shutdowns, and other events occurring in the mills which 

affect steam consumption affect the steam load on the boilers. Operating conditions in one boiler can

also adversely affect the other boilers, again due to the effect on steam demand. 

Appendix A contains additional technical information concerning the unique design features of bagasse 

boilers. Appendix A also contains additional technical information comparing bagasse boilers to woodfired boilers. 

IV. EPA’s Statutory Authority to Create Subcategories

Section 112 of the CAA contains the statutory requirements for establishing emission standards for 

industrial boilers based on the use of maximum achievable control technology (MACT). 

Section 112(d)(1) of the CAA expressly authorizes EPA to establish subcategories: 

The [EPA] Administrator shall promulgate regulations establishing emission standards 

for each category or subcategory of major sources...The Administrator may distinguish 

among classes, types, and sizes of sources within a category or subcategory in 

establishing such standards... 

Section 129 of the CAA also authorizes EPA to distinguish between classes, types, and sizes of units 

when setting MACT standards for incinerators. When construing Section 129, the U.S. Court of Appeals 

noted that EPA has “broad discretion to differentiate among units in a category” while setting MACT 

standards. Northeast Maryland Waste Disposal Authority v. EPA, 358 F.3d 936, 946 (D.C. Cir. 2004). 

The court concluded that the term “class” is “not defined in the Clean Air Act, and the dictionary 

definition –‘a group, set, or kind marked by common attributes’- could hardly be more flexible.” Id. The 

court’s analysis implies that EPA may reasonably establish subcategories based on a “class” whenever 

EPA finds that there is a “group, set, or kind” of unit (boiler, incinerator, etc.) marked by common 

attributes. 

EPA has exercised its discretionary authority to create subcategories in many prior MACT rulemaking 

proceedings. For example, EPA previously created subcategories when EPA set the MACT emissions 

standards for industrial boilers, electric utility steam generating units, and municipal waste combustors. 

EPA created these subcategories because EPA wanted to account for the differences between source 

types, the types of fuel used, the size of the regulated units, and other factors. In EPA’s “Notice of 

Regulatory Finding on the Emissions of Hazardous Air Pollutants from Electric Utility Steam Generating

Units” [Federal Register (FR), December 20, 2000], EPA stated: 

In developing standards under Section 112(d) to date, the EPA has based 

subcategorization on considerations such as: the size of the facility, the type of fuel used 

at the facility, and the plant type. The EPA may also consider other relevant factors 

such as geographic conditions in establishing subcategories. 

In EPA’s 2004 MACT proposal for electric utility steam generating units (Utility MACT) (FR, January 

30, 2004), EPA stated that it has broad discretion to create subcategories based on these same criteria 

(i.e., size of the facility, type of fuel used, and plant type). [pg. 4664] In addition, “EPA also is free to 

consider other relevant factors, such as geographic factors, process design or operation, variations in 

emission profiles, or differences in the feasibility of application of control.” [pg. 4664] In the Utility 

MACT, EPA exercised its discretion by proposing to create five separate subcategories for coal-fired 

electric utility boilers. [pg. 4666]. Four of the proposed subcategories were based on the type of coal 
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burned (i.e., bituminous/anthracite, sub-bituminous, lignite, and coal refuse). The fifth subcategory was 

based on the type of process used by the utility to convert coal into electricity (i.e., integrated gasification 

combined cycle technology). 

In EPA’s 2008 MACT proposal for mercury cell chlor-alkali plants (73 FR 33258; June 11, 2008), EPA 

noted that “EPA’s broad authority to establish categories and subcategories of industry sources is firmly 

established, and has been recognized as entitled to substantial deference by the U.S. Court of Appeals for 

the D.C. Circuit and the U.S. Supreme Court.” [page 33273]. In defense of its decision to create a 

subcategory for mercury cell chlor-alkali plants, EPA stated that “we have a long history of using 

subcategorization . . . Subcategories, or subsets of similar emission sources within a source category, may 

be defined if technical differences in emissions characteristics, processes, control device applicability, or 

opportunities for pollution prevention exist within the source category. This policy is supported by 

section 112(d)(1), the legislative history, our prior rulemakings, and judicial precedent.” (emphasis

added) [Id.] 

EPA has previously used criteria such as furnace heat release rate in developing NSPS subcategories for 

boilers. For example, 40 CFR 60 Subpart Db contains separate NOx limits for low heat release rates 

boilers and high heat release rate boilers burning fuel oil. For purposes of Subpart Db, a high heat 

release rate is defined as greater than 70,000 Btu/hr-ft3

 and a low heat release rate is less than or equal to 

70,000 Btu/hr-ft3

Another example of EPA using subcategories to set emission standards involved the NSPS for municipal 

waste combustors (MWCs) in 40 CFR 60, Subpart Ea. In this rulemaking, EPA set new standards for 

two categories of MWC combustor types. In the 1995 emission guidelines, EPA identified three distinct

types of MWC units that burn refuse-derived fuel (RDF), as follows: (1) RDF stoker, (2) pulverized 

coal/RDF mixed fuel-fired combustor, and (3) spreader stoker coal/RDF mixed fuel-fired combustor. 

Recently, EPA identified two additional types of RDF-fired MWC designs that do not fit within the three 

types of RDF combustors defined in the regulations. Since none of the three previous subcategories of

RDF municipal waste combustors correctly describe the design or operation of these particular units, 

EPA recognized a need to add combustor types that would adequately describe and set CO emission 

limits for these combustors. The EPA therefore added definitions for ‘‘spreader stoker RDF-fired 

combustor/100 percent coal capable’’ and ‘‘semi-suspension RDF-fired combustor/wet RDF process 

conversion.’’ This latter subcategory was defined as follows: 

Semi-suspension refuse-derived fuel-fired combustor/wet refuse-derived fuel process 

conversion means a combustion unit that was converted from a wet refuse-derived fuel 

process to a dry refuse-derived fuel process, and because of constraints in the design of 

the system, includes a low furnace height (less than 60 feet between the grate and the 

roof) and a high waste capacity-to-undergrate air zone ratio (greater than 300 tons of 

waste per day (tpd) fuel per each undergrate air zone). 

For these additional MWC technology types, EPA creasted CO emission limits based on the use of good 

combustion practices. A spreader/stoker RDF-fired combustor/100-percent coal-capable combustor 

feeds RDF into the combustion zone by a mechanism that throws the fuel onto the grate from above. 

Combustion takes place both in suspension and on the grate. Such a unit is capable of firing 100-percent 

coal as a replacement for RDF. A semi-suspension RDF-fired combustor/wet RDF process conversion 

means a combustion unit that was converted from wet RDF processing to dry RDF processing. For both 

of these technologies, CO emission limits were promulgated by EPA based on the CO levels achievable 

with good combustion practices. 
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Section 112(d)(3) of the CAA indicates that the MACT floor for new sources shall be established by 

determining “the maximum degree of reduction in emissions that is deemed achievable for new sources 

in a category or subcategory”. The MACT floor for new sources must be based on the emissions 

achieved by “the best controlled similar source, as determined by the Administrator” [Section 112(d)(3)]. 

The EPA’s regulations define the term “similar sources” to mean: 

 “a stationary source or process that has comparable emissions and is structurally 

similar in design and capacity to a constructed or reconstructed major source such that 

the source could be controlled using the same control technology.” [40 CFR 63.41] 

When the definition of “similar source” is read in conjunction with the mandate in Section 112(d)(3), 

which requires EPA to evaluate similar sources when setting MACT standards, it is clear that EPA has 

the discretion to establish MACT standards and MACT categories that account for the differences in 

design and capacity between sources. Indeed, the use of subcategories is necessary to ensure that EPA’s 

MACT standards are only applied to groups or classes of sources that have similar design, operational, 

and performance characteristics for controlling HAP emissions. 

Therefore, when setting MACT standards for industrial boilers, it appears that EPA is authorized to 

distinguish between: 

 (a) General classes or types of fuels (e.g., solid, liquid, and gaseous fuel); 

 (b) Specific classes or types of solid fuels (e.g., coal, wood, bagasse, and other biomass); 

 (c) Types of boilers (e.g., spreader stoker, fuel cell, fluidized bed, bagasse); 

 (d) Sizes of boilers; and 

 (e) Geographical locations of the boilers. 

Determining the appropriate source categories and subcategories is a critical first step when EPA sets the 

MACT floor for biomass-fired boilers, because there are a wide range of combustion processes, control 

technologies, unit sizes, and fuels used by biomass-fired boilers. These factors can have major impacts 

on a boiler’s performance and emissions profile. 

Based on the analysis set forth in the preceding paragraphs, the Florida Sugar Industry believes the 

MACT standards for industrial boilers should include a category for biomass boilers, and a separate 

subcategory for bagasse boilers. These categories and subcategories are necessary to ensure that EPA 

only compares the performance of “similar sources” when EPA sets the emissions standards for bagassefired boilers. As explained below, boilers that burn bagasse constitute a separate class of boilers that are 

different than other solid fuel and biomass boilers. Technical support data is provided in Appendix A. 

Given the differences between bagasse boilers and other types and classes of boilers, EPA should create 

a separate subcategory for bagasse boilers, and this subcategory should not include boilers that burn 

wood or other types of biomass. 

V. Characteristics of Bagasse and Bagasse Boilers

Bagasse and bagasse boilers have many distinctive characteristics. When all of these characteristics are 

considered together, it is apparent that bagasse boilers are a unique class of boilers. These boilers must 

contend with the chemical and physical nature of the fuel, the drying and combustion of the fuel in the 

boiler, and other factors that affect the design and operation of the bagasse boilers. These combined

characteristics warrant the creation of a separate class and subcategory in the new Boiler MACT rules. 

Refer to Appendix A for additional technical information concerning the unique design features of 

bagasse boilers. 
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A. Key Characteristics of Bagasse Fuel 

Bagasse has the following key characteristics, which collectively make bagasse unique and much 

different than other types of biomass fuel: 

• Bagasse is a co-product of an industrial process, wherein sugarcane is crushed 

and washed, and water displaces sucrose within the sugarcane fiber; 

• The industrial process alters the composition of the biomass; 

• The bagasse goes directly from the process (mill) to the boilers for fuel; 

• The geographic area in which sugarcane is grown, and the variety of sugarcane 

that is grown, affects the composition of the bagasse; 

• Bagasse is about 3 times less dense than wood. 

• Bagasse boilers must be designed specifically and uniquely to burn this fuel: 

• Bagasse absorbs moisture while stored; 

• Harvesting conditions and harvesting methods affect the composition, including 

the moisture content of the bagasse; 

• Bagasse as produced and burned has a high moisture content (48 to 55 percent); 

• It is very low in heavy metals; 

• It is typically only 2 percent ash; 

• The heating value [British thermal units per pound (Btu/lb)] as-fired is ample, 

but it is relatively low by comparison to the heating value of wood and other 

types of biomass; 

• Its use eliminates the need to import and use millions of gallons of fuel oil3

 or 

other types of fossil fuel each year in Florida and Hawaii, and thus its use greatly 

reduces the emissions of greenhouse gases in Florida and Hawaii; and 

• It is a renewable resource, which is produced annually without disturbing new 

land. 

Bagasse consistently contains from 48- to about 55-percent moisture as produced, and about 2-percent 

ash. The solids portion is composed mostly of cellulose fiber and pith, but it also contains some 

minerals, ash, and a small amount of sugars. It is bagasse’s high moisture content in combination with its 

processed state (highly fibrous with high porosity) that renders it unique compared with other forms of 

biomass. This high moisture content has a direct effect upon its combustion characteristics, as has been 

recognized by researchers.4

 

Bagasse is also distinctive in that it is “spongy,” like peat moss. Consequently, the bagasse absorbs

moisture more easily than woody biomass. Moisture is absorbed and contained in tiny pores throughout 

the bagasse material, as opposed to woody biomass, where the moisture is primarily surface moisture. 

This difference affects the combustion characteristics of bagasse and emissions of organics (especially 

CO). 

Both the high moisture content and the low ash content of bagasse is a result of the thorough washing of 

the sugarcane during the processing to extract the sugars. In this process, water displaces sucrose within 

 

3 The Florida Sugar Industry estimates that the use of bagasse in Florida’s sugar mills offsets or displaces the use of 

approximately 150 million gallons of fuel oil each year. 

4

 Shanmukharadhya, K.S. and Sudhakar, K. G., “Effect of Fuel Moisture on Combustion in a Bagasse Fired 

Furnace,” Transactions of the ASME, Vol. 129, September 2007. 
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the fiber of the sugarcane. The washing removes some, but not all, of the soil material that comes into 

the mill with the sugarcane. 

As noted above, the mill-run bagasse has a moisture content ranging from 48 to 55 percent, but it also has 

a heat content of about 3,600 to 4,200 Btu/lb as-fired. Consequently, bagasse can be readily used as a 

valuable fuel. Indeed, bagasse has been the main fuel of the sugar industry for the past 200 years. 

When bagasse is burned, small amounts of ash remain, most of which either falls out as bottom ash or is 

collected by air pollution control devices. Most of the sugar industry uses wet scrubbers and/or multiclones to capture the ash. Two bagasse boilers at one sugar mill in Florida have an ESP control device. 

Bagasse bottom ash and fly ash contain some unburned carbon and some of the non-combustible 

minerals that entered the mill (some from the soil clinging to the cane, but also some minerals in the cane 

itself). Some of the soluble minerals are extracted during the washing of the bagasse and are later 

precipitated from the sugarcane juices. These “clarifier muds” are not combusted, but are returned to

farm fields to reduce the need to add fertilizers or other necessary soil amendments. 

As noted earlier, bagasse is a very clean fuel with respect to heavy metals and, as a result, the ash 

particles emitted from bagasse-fired boilers contain extremely low concentrations of such metals. 

Bagasse boilers are equipped with either wet scrubbers or ESPs and, consequently, the boilers emit 

relatively small amounts of particulate matter (PM) and even smaller amounts of metal HAPs. 

PM is a good surrogate for metals emissions from bagasse boilers, but given the low metals content of 

bagasse ash, an appropriate PM emissions limit for bagasse boilers could likely be higher than the PM 

emissions limit for other solid fuel boilers. Additionally, the wet scrubbers used at most sugar mills will 

remove almost all of the small amounts of HCl that might be formed in the boilers from the combustion 

of bagasse. 

B. Key Combustion Characteristics of Bagasse 

Bagasse fuel is a light-weight, fibrous, high-moisture content fuel. Given these characteristics, bagasse is 

combusted differently than wood, wood chips and bark, which are heavier and have a lower moisture 

content and a higher heating value than bagasse. If EPA contemplates setting emission limits for organic 

HAPs, or for CO as a surrogate for organic HAPs, EPA should recognize that the combustion 

characteristics of bagasse are different than the combustion characteristics of other types of biomass, and 

these characteristics strongly influence emissions. The key combustion characteristics of bagasse, which 

collectively make bagasse burn differently than other types of biomass, are as follows: 

• It has a low combustion temperature because it has a high moisture content; 

• It is dried and burned in boilers with relatively high heat release rates and high 

excess air rates; 

• It has relatively low NOx emissions and very low SO2 emissions; 

• It is carbon neutral; 

• It is burned for combined heat and power production (i.e., steam and electricity); 

and 

• It is combusted on a seasonal basis. 

These characteristics of bagasse, combined with the distinctive design and operation of bagasse boilers, 

strongly influence the emissions from bagasse boilers. The high moisture content (48 to 55 percent) of 
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bagasse (and especially the moisture absorbed in the fiber) results in a relatively low combustion 

temperature in bagasse-fired boilers. The low temperature occurs because a significant amount of heat is 

consumed in the furnace by the process of evaporating the water from the bagasse, and the moisture 

suppresses the combustion temperatures. 

These factors, combined with the furnace design, and in particular the amount of heat input per unit of 

furnace volume (Btu/hr-ft3

), cause significant effects on the combustion process and the subsequent 

emissions of CO. Higher heat release rates produce shorter residence times for combustion gases 

within the furnace, allowing less time to completely burn out the CO in the gases. Existing Florida and 

Hawaii bagasse boilers, except for one newer boiler, have furnace heat release rates ranging from 23,000 

to 51,000 Btu/hr-ft3. 

Additionally, it must be remembered that sugarcane processing is a seasonal operation; in some cases, the 

season is only a few months. Given similar emission factors, seasonal operations produce lower total 

annual emissions than year-round operations. It also means that many of these boilers are older compared 

to non-seasonal industries because (being used only part of a year each year) they are typically operated 

for more years to achieve the same operating life. This seasonality is another factor in requesting a

separate sub-category for bagasse boilers. 

Refer to Appendix A for further information regarding the combustion characterisitics of bagasse. 

C. Key Design and Operating Characteristics of Bagasse Boilers 

Bagasse boilers are designed and operated differently than other solid fuel boilers: 

• The boilers are designed to dry and burn bagasse; 

• The boilers operate primarily with suspension firing, with some grate firing; 

• The boilers operate at relatively low temperatures;

• The boilers have relatively high heat release rates; 

• The boilers have relatively high excess air rates; 

• The boilers are fully integrated into the milling operation; and 

• The boilers experience considerable variability in operation during a typical day. 

As described previously, moisture in bagasse is both surface moisture and moisture contained throughout 

the fiber. As a result, this moisture is more difficult to remove compared to surface moisture, such as 

that present with wood. The combustion of bagasse in a bagasse boiler is carried out in a three-step 

process within the furnace. The first step is drying of the bagasse, which occurs mainly in suspension but 

also on the grate or fuel pile. The second step is the driving off of the volatile constituents. The third 

and final step is combustion of the bagasse (carbon burning). The high moisture content (48 to 

55 percent) of bagasse coupled with the porous fibers results in a relatively low combustion temperature 

in bagasse-fired boilers. This factor, combined with the furnace design, and in particular the heat release 

rate (amount of heat input per unit of furnace volume) and higher excess air amounts, causes significant 

effects on the combustion process and the subsequent emissions of CO compared with fossil fuels or 

woody biomass. Existing bagasse boilers were designed with smaller furnace volumes and higher heat 

release rates than the newest bagasse boilers. Nonetheless, even the newest bagasse boilers with low heat 

release rates experience variable and transient CO emissions due to bagasse variability and their 

integration with mill operations, as described below. 
May 2009 0838-7513 

Reports/Boiler MACT 2/Separate Class of Bagasse Boilers 05-14-09.doc 10

Using bagasse as a fuel also produces lower emissions of NOx and SO2 compared with fossil fuels. 

Bagasse, like most biomass, has a significant oxygen content within its molecular structure. The internal 

oxygen and internal moisture content of bagasse contribute to bagasse burning at a lower temperature 

than fossil fuels. In turn, the lower combustion temperature reduces the formation of combustion-related 

NOx (mostly NO and NO2), in comparison to the levels associated with the combustion of fossil fuel. 

This reduction is important because NOx is one of the main pollutants responsible for urban smog and 

ozone, and SO2 and NOx are the largest contributors to acid rain. 

The integrated operation of sugar mills and sugar mill boilers is unique, to our knowledge, and has a direct 

impact on emissions from the boilers. The bagasse for the boilers comes directly from the mill. When the 

quality of cane coming into the mill changes (e.g., due to wet, muddy field conditions), the performance of 

the mills can be adversely affected. Any change in the output of the mills will have an immediate impact on 

the quality of bagasse being fed to the boilers. Bagasse moisture, for example, can swing widely in a very 

short period of time. These fluctuations in the quality of the bagasse necessitate constant adjustments by 

boiler operators (e.g., adjustments to combustion air) to optimize combustion as the fuel quality varies, and 

may also require the use of supplemental fuels (e.g., fossil fuels) to stabilize combustion. 

All of these adjustments contribute to transient conditions in CO emissions (and therefore higher average 

CO emissions) than would be observed in a boiler operating on fuel of consistent quality. Even the burning 

of supplemental fossil fuels cannot always resolve these transient CO conditions. As a result, even newer 

bagasse boilers can experience higher CO emissions than wood or other biomass-fired boilers. 

Fluctuating steam loads are typical of sugar mill operations and they contribute to emissions transients. 

This phenomenon can be witnessed in the control room of any sugar mill and it is documented by the steam 

charts for the boilers. Unlike utility boilers and many industrial boilers which operate at a relatively steady 

load, steam loads at a sugar mill can vary widely over short periods of time. Field conditions or a lack of 

cane can result in the sudden starting and stopping of the mills, which are a major steam load for the boilers. 

The rapid change in steam load has a dual impact on the boilers because (1) it causes emissions transients 

and (2) it also adversely impacts the bagasse moisture when the mill restarts because the hydraulic pressure 

exerted by the mills is dependent on adequate steam load. As a result, unstable regimes of combustion often 

occur in bagasse boilers.5

 

Similarly, conditions in the boiling house can cause increases and decreases in steam demand. For units that 

supply power to electric utilities, fluctuations on the transmission line grid can result in a sudden increase in 

electricity demand, which again results in an increase in steam demand. These operational considerations 

significantly affect the emissions from bagasse-fired boilers and thus they are important factors to consider 

when determining the emissions standards that are achievable for sugar mill boilers. 

Representative steam charts from actual bagasse boiler operations are provided in Appendix B. These 

steam charts demonstrate the typical variability in steam production rates experienced by bagasse boilers. 

VI. Other Considerations

Given the unique characteristics of bagasse, it would be appropriate to create a subcategory in the Boiler 

MACT rules for bagasse boilers, based on the type of fuel used and the design of these boilers. The 

information contained in this document provides a rationale basis for such a subcategory. Although the bulk 

 

5

 Woodfield, P., Kent, J., Novozhilov, V., and Dixon, T., “Prediction of unstable regimes in the operation of bagasse 

fired furnaces,” Second Internation Conference on CFD in the Minerals and Process Industries, CSIRO, Melbourne, 

Australia, December 6-8, 1999. 
May 2009 0838-7513 

Reports/Boiler MACT 2/Separate Class of Bagasse Boilers 05-14-09.doc 11

of this document advocates the creation of a subcategory based on the class of boilers used by the sugar 

industry, a strong argument can be made that the subcategory should be based on the type of fuel used by 

the sugar industry’s boilers. 

A subcategory for bagasse fuel is not inconsistent with the concept that fuel switching may be a suitable 

emissions control technique in certain industries. In some industries, there may be several fuels (e.g., fuel 

oil and natural gas) that can be used in a cost-effective manner and thus it may be possible for those

industries to switch to a cleaner fuel. In the sugar industry, however, fuel switching is not a feasible option. 

Bagasse is the only fuel that is produced by the sugar industry. Bagasse is a co-product of the sugarcane 

harvest and it is essentially a free fuel. There is no other fuel that could be substituted for bagasse and used 

by the sugar industry in an economically viable fashion. 

Creating a subcategory for bagasse boilers is consistent with the national goal of using locally-produced 

renewable energy sources to meet our national energy needs. Bagasse is truly a “green” resource—it is

produced during the sugarcane harvest each year and it displaces the use of fossil fuels. Bagasse also is 

carbon neutral (or a carbon sink) and, therefore, its use as an energy source helps reduce the creation of 

greenhouse gases. 

For these reasons, EPA should encourage the continued use of bagasse as a renewable fuel. Conversely,

EPA should not adopt Boiler MACT rules that would hinder or preclude the use of this valuable resource. 

The unique characteristics of this fuel warrant the creation of a separate subcategory for bagasse boilers, 

based on the type of fuel they use. 

VII. Conclusions

In summary, bagasse is a valuable fuel that is unique to the sugar industry. Bagasse results from and is a 

co-product of the cane sugar production process, which alters the characteristics of this biomass fuel. 

Bagasse boilers constitute a separate and unique class of boilers, which are are uniquely designed and

operated to dry and burn bagasse in a fully integrated process within the sugar mills. This combination 

of factors results in a unique emissions profile (low metals, low NOx, low-sulfur oxides, low HCl, but 

high CO). For all the reasons discussed above, we are convinced that the emissions data from other 

solid-fuel boilers are not representative of bagasse boilers. Including bagasse boilers with other solidfuel or biomass boilers will result in an inappropriate MACT floor for bagasse boilers. 

Given the design and operation of sugar mill boilers, as well as nature of bagasse, the FSI believes that it 

is appropriate for EPA to place bagasse boilers in a separate subcategory (containing only the class of 

boilers designed to burn bagasse) under Section 112 of the CAA when EPA establishes MACT standards 

for industrial boilers. 
APPENDIX A 

 
May 2009 - 1 - 0838-7513 

Appendix A to FSI White Paper 5-14-09.docx 

APPENDIX A 

TECHNICAL DATA CONCERNING THE DESIGN AND OPERATION 

OF BAGASSE BOILERS 

This document contains technical data concerning the design and operation of bagasse boilers. The 

following data demonstrate that bagasse boilers should be placed in a separate subcategory under the 

Boiler MACT rules being promulgated by the U.S. Environmental Protection Agency (EPA). 

INTEGRATION OF BOILERS WITH MILL 

The most significant difference between bagasse boilers and other biomass-fired boilers is the integration 

of bagasse boilers directly with the sugar mill. The two primary aspects of boiler and mill integration 

which can affect bagasse boiler emissions are: 

 Integration of the fuel supply from the mill to the boilers; and 

 Integration of the steam supply from the boilers to the mill. 

The attached flow diagram shows the integrated nature of these operations. Actual mills are more 

complicated than shown, since they typically have two grinding mills (tandems) and from three to six 

boilers, all integrated together. 

Bagasse is a fuel that is delivered to the boilers directly from the juice extraction process. Therefore, the 

quality of the bagasse is dependent on the stability and consistency of the juice extraction process. 

However, this process is variable due to changing varieties of sugar cane, changing field conditions which 

affect the quality of the incoming cane, mill stops/starts, etc. These factors also affect the steam demands 

of the mills, which in turn affects the boiler operations because all the boilers are tied into a single steam 

header system. 

Any problems or excursions occurring in the extraction process normally result in an increased bagasse 

moisture content of the bagasse delivered to the boilers. This combined with the lower adiabatic flame 

temperatures and the lack of thermal inertia on the grate leads to increased concentrations of unburned 

volatiles and carbon monoxide. 

These fundamental differences mean that a bagasse boiler experiences continuous fuel quality changes, 

which are far more difficult to control or to accommodate compared to operations in a typical wood-fired 

boiler 

In contrast, wood-fired boilers are normally fed from a stockpile of fuel that has known characteristics 

and a more consistent quality. The wood fuel supply is not tied to the process it is serving, nor is the fuel 

subject to relatively frequent and significant variations due to the process. 

At a sugar mill, all the boilers are tied into a single steam header. The steam header supplies steam to 

multiple grinding/extraction mills, steam turbine electrical generators, and to the raw sugar manufacturing 

process. Because of this integration, the operation of a single boiler affects the operation of the other 

boilers at the mill. If one boiler experiences problems due to changing bagasse quality or to mill 

fluctuations, its steam production can drop quickly, and this affects the other boilers (i.e., they must 
May 2009 - 2 - 0838-7513 

Appendix A to FSI White Paper 5-14-09.docx 

attempt to increase their steam production to compensate), because they are all tied into one steam 

system. 

To demonstrate the variability of steam production rates associated with bagasse boilers, typical steam 

charts from two representative boilers are attached. These charts clearly show the continuing variability 

in steam production rates resulting from the integration of the boilers with the mills. Indeed, the steam 

production and CO data (attached) from the sugar industry’s newest boiler (U. S. Sugar Boiler No. 8) 

demonstrates that even the newest bagasse boilers experience this variability. The variability experienced 

with this boiler is much less than the variability experienced with most of the other sugar mill boilers, 

because the new boiler is designed with newer technology that can better handle these fluctuations. 

Accordingly, this boiler would be representative of a new boiler, not an existing boiler. 

In contrast, wood-fired boilers are normally tied into a much more stable process where steam demand is 

relatively stable, and where the process has much less affect on the boiler operation and no affect on fuel 

quality. 

BOILER DESIGN

Furnace Heat Release Rate 

The second most significant difference between wood-fired/other biomass boilers and bagasse-fired 

boilers is in furnace heat release rates. The furnace heat release rate is the measure of how much energy 

is released from burning the fuel per cubic foot of furnace volume. This directly relates to the residence 

time of the combustion gases in the furnace, which in turn affects carbon burnout and emissions of 

particulate matter, volatile organics, and carbon monoxide. 

ABB Combustion Engineering Systems (ABB) performed a survey of biomass boilers and presented the 

results in Technical Paper TIS 8496 (copy attached). A total of nine boilers were field surveyed. 

Although the type of biomass was not specified for each boiler, it is appears that these were wood-fired 

boilers. Given ABB’s description of the boilers, it is clear that they were not bagasse boilers located in 

Florida. All of the boilers, except one, had tangential overfire air systems. Excess air ranged from 22 to 

58 percent on the units (although one unit operated with 108 percent excess air). Furnace heat release 

rates ranged from 8,900 to 17,900 British thermal units per hour per cubic foot (Btu/hr-ft3

), except for one 

unit that had a heat release rate of 23,200 Btu/hr-ft3

. Grate heat release rates ranged from 530,000 to 

1,019,000 British thermal units per hour per square foot (Btu/hr-ft2

), except for one unit with a grate heat 

release rate of 1,324,000 Btu/hr-ft2

. 

Typical design parameters for biomass boilers are also provided in Combustion Fossil Power, 4th Edition 

(Combustion Engineering, 1991). The typical furnace heat release rate for wood-fired boilers ranges 

from 15,000 to 20,000 Btu/hr-ft3

, while the typical grate heat release ranges from 900,000 to 

1,200,000 But/hr-ft2

. 

In contrast, bagasse boilers have furnace heat release rates ranging from 18,700 to 51,600 Btu/hr-ft3

, 

with only one new boiler and one middle-aged boiler having furnace heat release rates less than 

25,000 Btu/hr-ft3

. Grate heat release rates for bagasse boilers range from 855,000 to 1,667,000 Btu/hr-ft2. 

Table 1 (attached) contains a compilation of bagasse boiler furnace heat release rates. Typical values for 

wood-fired boilers are also shown at the bottom of Table 1. As shown, furnace heat release rates for 

bagasse boilers are significantly higher than for wood-fired boilers, while grate heat release rates are 
May 2009 - 3 - 0838-7513 

Appendix A to FSI White Paper 5-14-09.docx 

slightly higher for bagasse boilers. The furnace heat release rates for bagasse boilers have a significant 

effect upon the emissions from the bagasse boilers, and they cause the emissions from bagasse boilers to 

be significantly different than the emissions from wood boilers. 

EPA has previously used criteria such as furnace heat release rate in developing NSPS subcategories for 

boilers. For example, 40 CFR 60 Subpart Db contains separate NOx limits for low heat release rates 

boilers and high heat release rate boilers burning fuel oil. For purposes of Subpart Db, a high heat release 

rate is defined as greater than 70,000 Btu/hr-ft3

 and a low heat release rate is less than or equal to 

70,000 Btu/hr-ft3

. The FSI is requesting a similar determination for bagasse boilers. 

A bagasse boiler must be designed differently than other solid-fueled boilers. For example, when an 

existing coal-fired boiler at a power plant was purchased by a sugar mill, the boiler had to be converted 

before it could be used to burn bagasse at the mill. The coal-fired boiler originally was designed for a 

300,000-pound-per-hour (lb/hr) steam rate. It had a furnace volume of 17,200 cubic feet (ft3

) and a grate 

area of 506 square feet (ft2

). This design resulted in a furnace heat release rate of 23,400 Btu/hr-ft3, a 

grate heat release rate of 938,700 Btu/hr-ft2

, and a grate fuel loading rate of 0.0375 ton per hour per 

square foot (ton/hr-ft2

). 

The sugar mill had to modify the boiler so that the boilers could achieve a steam capacity of 275,000 lb/hr 

while burning bagasse. The drum centers were extended, new fuel distributors installed, and the furnace 

volume was increased to 21,245 ft3

. Since bagasse has a lower heating value than coal, much more 

bagasse than coal was needed to be burned to achieve the desired steam generation. So the boiler heat 

input rating was increased from 402 MMBtu/hr (coal) to 633 MMBtu/hr (bagasse). Due to the higher 

moisture content and the lower heating value of bagasse, the resulting heat release rates were increased to 

29,800 Btu/hr-ft3

 for the furnace and 1,251,000 Btu/hr-ft2 for the grate. The fuel loading rate was 

increased to 0.174 ton/hr-ft2

. All of these parameters are significantly higher for the bagasse boiler than 

the coal-fired boiler. 

Excess Air Levels 

Bagasse boilers are also designed for much higher excess air levels than wood-fired or other biomass 

boilers. Wood-fired boilers typically operate at approximately 25 to 50 percent excess air. Bagasse 

boilers on the other hand operate between 50 to 110 percent excess air. Actual excess air levels for the 

Florida and Hawaii bagasse boilers, based on historic stack test data, are shown in Table 1 (attached). 

The major reasons for the high excess air levels are as follows: 

 Higher gas upflow and velocities and hence, more excess air, are needed for the higher 

moisture fuels in order to keep the gas in contact with the fuel particles for the longer 

period of time needed to dry them (Cane Sugar Engineering, Chapter 27, Steam 

Generation, by N. Magasiner, Thermal Energy Systems, South Africa). The higher 

excess air levels are also required to maximize combustion in suspension while 

minimizing combustion on the grate. If excess air is reduced or minimized, piles can 

form on the grate and inhibit the combustion process. Higher excess air levels help 

insure that combustion on the grate is minimized. 

 To accommodate anticipated swings in bagasse moisture (higher moisture fuel requiring 

more excess air). The boilers are operated with higher than optimum excess air in order 
May 2009 - 4 - 0838-7513 

Appendix A to FSI White Paper 5-14-09.docx 

to smooth operational swings and minimize upset conditions when wetter bagasse 

(requiring higher excess air) comes from the mill. 

Wood boilers generally operate with much more consistent moisture and ash levels than bagasse boilers. 

Consequently, wood boilers can fine-tune their excess air levels to the anticipated, stable moisture 

content. The closer excess air levels are to being optimized, the more complete combustion will be. High 

excess air levels in bagasse boilers further contribute to the already lower combustion temperatures, 

which result in higher CO emissions. In addition, more air flow means there is less residence time in the 

boiler for the combustion gases, which in turn contributes to higher CO emissions. Even if the bagasse 

boilers are operated at the optimum excess air for a “typical” moisture content (say, 50 percent), CO 

emissions will increase as soon as wetter fuel (which requires more excess air) is introduced into the 

boiler, unless and until air flows can be adjusted. 

Bagasse boilers are designed to provide higher excess air levels. This design goal is achieved by 

employing greater forced draft, induced draft, and overfire air capacity. This, design goal also is achieved 

by using a greater number of overfire air nozzles and by using overfire air nozzles that have a higher 

capacity. Wood–fired boilers typically employ tangential overfire air systems, unlike bagasse boilers, 

which utilize wall-mounted overfire air nozzles. The wall-mounted nozzles are typically located on the 

front and rear walls of the bagasse boiler, but the nozzles can also be located on the side walls. 

Suspension Burning versus Grate Burning 

Bagasse and wood are very different fuels on an as-fired basis, requiring that the firing systems be 

designed differently. Bagasse is typically between 50- and 55-percent moisture with 2- to 4-percent ash, 

depending on the type and efficiency of the juice extraction process. Wood fired in spreader stoker 

boilers typically has a moisture content of 30 to 35 percent. The typical density of wood fuel is three (3) 

times that of bagasse. The density of the wood, combined with the particle-size distribution resulting 

from a typical hogger and screening system, means that the bulk of the wood fuel will burn on the grate, 

and only the fines burn in suspension. In contrast, bagasse has a much finer (smaller) particle size 

distribution, due to the nature of the cane preparation process and the cane grinding process, which both 

facilitate the extraction of the cane juice. As discussed above, bagasse boilers are also designed and 

operated with higher excess air levels than wood-fired boilers, in order to promote greater suspension 

firing as opposed to firing on the grate. Thus, in a bagasse boiler, the fuel burns primarily in suspension 

and not on the grate. 

Fuel Feed System 

Bagasse has a lower bulk density than wood, so a greater volume of fuel must be fired for the same heat 

input. The need for more fuel is further exacerbated by the higher moisture content of bagasse. 

Consequently, fuel feed systems for bagasse generally need to be larger than for wood to achieve the 

same boiler heat input. The use of more fuel and larger fuel feed systems also negatively affect the 

boiler’s ability to respond to an increase in fuel moisture or changes in boiler loads. When moisture 

increases in bagasse fuel, a larger volume of fuel must be fed to make up for the higher moisture than 

would be the case for the same moisture increase in wood fuel. Similarly, when the boiler load changes, a 

larger volume of bagasse fuel must be fed into the boiler to supply the additional heat than would be the 

case for a wood boiler. These factors can contribute to a less responsive boiler and therefore larger 

emissions transients in bagasse boilers than in wood boilers. 
May 2009 

1-hr Steam 

Capacity

Heat Input 

Capacitya

Bagasse 

Feed Rate

Furnace 

Volume

Furnace Heat

Release 

Ratea

Gra

Surfa

Are

Company (lb/hr) (MMBtu/hr) (TPH) (ft3) (Btu/hr-ft3) (ft2

U.S. Sugar Clewiston 1 1968 Riley SS Vibrating 245,000 495 68.8 9,670 51,189 29U.S. Sugar Clewiston 2 1968 Riley SS Vibrating 215,000 447 62.1 9,670 46,225 29U.S. Sugar Clewiston 4 1984 Foster Wheeler SS Traveling 300,000 633 87.9 21,245 29,795 50U.S. Sugar Clewiston 7 1997 Alpha Conal SS Vibrating 385,000 812 112.8 43,470 18,680 704 U.S. Sugar Clewiston 8 2004 TES/McBurney SS Traveling 633,000 1185 164.6 50,520 23,456 98SCGCF 1 1963 Riley SS

Traveling; Watercooled Pinhole 139,700 267 37.1 8,450 31,598 264 

SCGCF 2 1963 Riley SS

Traveling; Watercooled Pinhole 138,154 269 37.4 8,450 31,834 264 

SCGCF 3 1966

Combustion 

Engineering SS

Traveling; Watercooled Pinhole 110,000 229 31.8 5,400 42,407 224 

SCGCF 4 1971 Riley SS Traveling 300,000 572 79.4 21,100 27,109 54SCGCF 5 1968 Riley SS Traveling 230,000 439 61.0 15,145 28,986 39SCGCF 8 1982 Riley SS Traveling 264,000 504 70.0 21,100 23,886 54Osceola 2 1965 Bigelow SS Inclined 140,000 280 38.9 9,768 28,665 405 Osceola 3 1961 Alpha SS Inclined 150,000 292 40.6 10,106 28,894 405 Osceola 4 1965 Bigelow C N/A 140,000 280 38.9 6,400 43,750 N/A Osceola 5 1978 Alpha C N/A 165,000 330 45.8 6,400 51,563 N/A Osceola 6 1981 Distral SS Traveling 195,000 379 52.6 11,300 33,540 36Puunene- Hawaii 1 1952 Riley SS Traveling 125,000 212 29.4 7,174 29,551 235 Puunene- Hawaii 2 1952 Riley SS Traveling 125,000 212 29.4 7,174 29,551 235 Puunene- Hawaii 3 1973 Foster Wheeler SS Traveling 290,000 568 78.9 24,852 22,855 57Typical Wood-Fired Boiler Ref. 1

180,000 - 

550,000

 8,900 - 

23,200 

Typical Wood-Fired Boiler Ref. 2

 15,000 - 

20,000 

Note: SS= spreader stoker. C= fuel cell.

a Based on 2008 EPA MACT Combustion Survey.b Side of furnace which includes fuel feeders.c Derived from last 10 years of stack test data.

References:1. Biomass Fuel Combuston System Design, Technical Paper TIS 8496. ABB Combuston Engineering Systems.2. Combustion Fossil Fuel, 4th Edition. Combustion Engineering, Inc., 1991. 

TABLE 1. BAGASSE BOILER FURNACE DATA

Boiler Year Manufacturer Type Grate Type

Fl-HAW Furnace Design Data 5-14-09.XLS Golder Associates

APPENDIX B 
May 2009 0838-7513 

Appendix B 5-14-09.docx 

APPENDIX B 

The typical variability in steam flow and CO emissions from bagasse boilers is portrayed in the attached 

graphs and figures. These data are provided to show the degree of variability that bagasse boilers 

typically experience due to their full integration with the operation of the sugar mill and the variable 

nature of the bagasse fuel received from the mills. Each set of data are further described below. 

Steam Flow- Typical Boiler 

These charts display several typical operating days for one of the boilers at a sugar mill. Note the 

constant fluctuation in steam flow. 

USSC - Boiler 8 Steam Flow and Mill Episodes vs. CO 

These charts display several typical operating days for the newest boiler in the industry, which began 

operating in 2005 at U. S. Sugar Corporation (USSC). For each day presented, there is a corresponding 

chart that provides the hourly average CO emissions from the boiler. The boiler has a limit of 400 parts 

per million by volume, dry (ppmvd) at 7-percent O2, 30-day rolling average, based on the now-vacated 

Boiler MACT rule. It is noted that the boiler has been in compliance with this limit since startup through 

the present time, despite these normal fluctuations in short-term CO emissions. 

USSC – Boiler 8 Steam Flow 

This chart displays the hourly steam production rate of Boiler 8 at USSC (the newest boiler in the 

industry) over the 2008-2009 crop season. The purpose of this chart is to show the continuous variability 

in steam production, which is normal operation for a sugar mill boiler, and that even the newest boiler 

experiences these fluctuations. 
Steam Flow – Typical Boiler 

 
250

STEAM FLOW

FSI - Typical Boiler

12/1/2008

150200100

Steam Flow (klbs) 

0

50

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 
250

STEAM FLOW

FSI - Typical Boiler

12/2/2008

150200100

Steam Flow (klbs) 

0

50

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 
250

STEAM FLOW

FSI - Typical Boiler

12/3/2008

150200100

Steam Flow (klbs) 

0

50

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 
250

STEAM FLOW

FSI - Typical Boiler

12/4/2008

150200100

Steam Flow (klbs) 

0

50

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:0
USSC – Boiler 8 Steam Flow and 

Mill Episodes vs. CO 

 
800

10001200

7% O2)

USSC Boiler 8 - Mill Episodes vs. CO

10/08/2008

0

200400600

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 

CO Emissions (ppm @ 7
400

500600

USSC - Boiler 8

Steam Flow

10/08/2008

0

100200300

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 

Steam Flow (klbs) 
500

600700

7% O2)

USSC Boiler 8 - Mill Episodes vs. CO

10/11/2008

0

100200300400

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

CO Emissions (ppm @ 7
400

500600

USSC - Boiler 8

Steam Flow

10/11/2008

0

100200300

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 

Steam Flow (klbs) 
600

700800900

1000

7% O2)

USSC Boiler 8 - Mill Episodes vs. CO

11/03-04/2008

0

100200300400500

0:00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 0:00

CO Emissions (ppm @ 7
400

500600

USSC - Boiler 8

Steam Flow

11/03-04/2008

0

100200300

0:00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 

Steam Flow (klbs) 
800

10001200

7% O2)

USSC Boiler 8 - Mill Episodes vs. CO

11/18/2008

0

200400600

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:0

CO Emissions (ppm @ 7
400

500600

USSC - Boiler 8

Steam Flow

11/18/2008

0

100200300

21:37 23:37 1:37 3:37 5:37 7:37 9:37 11:37 13:37 15:37 17:37 19:37 21:37 23:37

Steam Flow (klbs) 
500

600700

7% O2)

USSC Boiler 8 - Mill Episodes vs. CO

02/15/2009

NCh 

0

100200300400

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

CO Emissions (ppm @ 7Ch

BocoMm
500

600700

USSC - Boiler 8

Steam Flow

02/15/2009

0

100200300400

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 

Steam Flow (klbs) 
500

600700

USSC - Boiler 8

Steam Flow

02/15/2009

0

100200300400

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 

Steam Flow (klbs) 
USSC – Boiler 8 Steam Flow 
700

USSC - Boiler 8

Steam Flow

2008-2009 Crop Season

500600200300400

Steam Flow (klbs) 

0

100

10/1/08 0:00 10/21/08 0:00 11/10/08 0:00 11/30/08 0:00 12/20/08 0:00 1/9/09 0:00 1/29/09 0:00