DOE/EE-0288Leading by example,saving energy and Biomass Cofiring in Coal-Fired Boilerstaxpayer dollarsin federal facilities Using this time-tested fuel-switching technique in existing federal boilers helps to reduce operating costs, increase the use of renewable energy, and enhance our energy security Executive Summary To help the nation use more domestic fuels and renewable energy technologies—and increase our energy security—the Federal Energy Management Program (FEMP) in the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, assists government agencies in developing biomass energy projects. As part of that assistance, FEMP has prepared this Federal Technology Alert on biomass cofiring technologies. This publication was prepared to help federal energy and facility managers make informed decisions about using biomass cofiring in existing coal-fired boilers at their facilities. The term “biomass” refers to materials derived from plant matter such as trees, grasses, and agricultural crops. These materials, grown using energy from sunlight, can be renewable energy sources for fueling many of today’s energy needs. The most common types of biomass that are available at potentially attractive prices for energy use at federal facilities are waste wood and wastepaper.The boiler plant at theDepartment of Energy’s One of the most attractive and easily implemented biomass energy technologies is cofiringSavannah River Site co-fires coal and biomass. with coal in existing coal-fired boilers. In biomass cofiring, biomass can substitute for up to 20% of the coal used in the boiler. The biomass and coal are combusted simultaneously. When it is used as a supplemental fuel in an existing coal boiler, biomass can provide the following benefits: lower fuel costs, avoidance of landfills and their associated costs, and reductions in sulfur oxide, nitrogen oxide, and greenhouse-gas emissions. Other benefits, such as decreases in flue gas opacity, have also been documented. Biomass cofiring is one of many energy- and cost-saving technologies to emerge as feasible for federal facilities in the past 20 years. Cofiring is a proven technology; it is also proving to be life-cycle cost-effective in terms of installation cost and net present value at several federal sites. Energy-Saving Mechanism Biomass cofiring projects do not reduce a boiler’s total energy input requirement. In fact, in a properly implemented cofiring application, the efficiency of the boiler will be the same as it was in the coal-only operation. However, cofiring projects do replace a portion of the non- renewable fuel—coal—with a renewable fuel—biomass. Cost-Saving Mechanisms Overall production cost savings can be achieved by replacing coal with inexpensive biomass fuel sources—e.g., clean wood waste and waste paper. Typically, biomass fuel supplies should cost at least 20% less, on a thermal basis, than coal supplies before a cofiring project can be economically attractive. U.S. Department of Energy Energy Efficiency Internet: www.eere.energy.gov/femp/ and Renewable Energy No portion of this publication may be altered in any form without Bringing you a prosperous future where energy prior written consent from the U.S. Department of Energy, Energy is clean, abundant, reliable, and affordable Efficiency and Renewable Energy, and the authoring national laboratory.
Federal Technology AlertPayback periods are typically To make economical use of captive investment of $850,000 wasbetween one and eight years, wood waste materials—primarily required, resulting in a simpleand annual cost savings could bark and wood chips that are payback period for the projectrange from $60,000 to $110,000 unsuitable for making paper—the of less than four years. The netfor an average-size federal boiler. U.S. pulp and paper industry has present value of the project,These savings depend on the cofired wood with coal for evaluated over a 10-year analysisavailability of low-cost biomass decades. Cofiring is a standard period, is about $1.1 million.feedstocks. However, at larger- mode of operation in that indus- Test burns at SRS have shown thatthan-average facilities, and at try, where biomass fuels provide the present stoker boiler fuel han-facilities that can avoid disposal more than 50% of the total fuel dling equipment required nocosts by using self-generated input. Spurred by a need to reduce modification to fire the biomass/biomass fuel sources, annual fuel and operating costs, and coal mixture successfully. No fuel-cost savings could be signifi- potential future needs to reduce feeding problems were experi-cantly higher. greenhouse gas emissions, an enced, and no increases in main- increasing number of industrial- tenance are expected to be neededApplication and utility-scale boilers outside at the steam plant. Steam plantBiomass cofiring can be applied the pulp and paper industry are personnel have been supportiveonly at facilities with existing being evaluated for use in cofiring of the project. Emissions measure-coal-fired boilers. The best oppor- applications. ments made during initial testingtunities for economically attrac- showed level or reduced emissionstive cofiring are at coal-fired facili- Case Study Summary for all eight measured pollutants,ties where all or most of the fol- The U.S. Department of Energy’s and sulfur emissions are expectedlowing conditions apply: (1) coal (DOE) Savannah River Site (SRS) to be reduced by 20%. Opacityprices are high; (2) annual coal in Aiken, South Carolina, has levels also decreased significantly.usage is significant; (3) local or installed equipment to produce The project will result in a reduc-facility-generated supplies of bio- “alternate fuel,” or AF, cubes from tion of about 2,240 tons per yearmass are abundant; (4) local land- shredded office paper and finely in coal usage at the facility.fill tipping fees are high, which chipped wood waste. After a seriesmeans it is costly to dispose of of successful test burns have been Implementation Barriersbiomass; and (5) plant staff and completed to demonstrate accept-management are highly motivated For utility-scale power generation able combustion, emissions, andto implement the project success- projects, acquiring steady, year- performance of the boiler and fuelfully. As a rule, boilers producing round supplies of large quantities processing and handling systems,less than 35,000 pounds per hour of low-cost biomass can be diffi- cofiring was expected to begin in(lb/hr) of steam are too small to cult. But where supplies are avail- 2003 on a regular basis. The bio-be used in an economically attrac- able, there are several advantages mass cubes offset about 20% oftive cofiring project. to using biomass for cofiring opera- the coal used in the facility’s two tions at federal facilities. For exam- traveling-grate stoker boilers. The ple, federal coal-fired boilers areField Experiences project should result in annual coal typically much smaller thanCofiring biomass and coal is a time- cost savings of about $112,000. utility-scale boilers, and theytested fuel-switching strategy that Cost savings associated with avoid- are most often used for spaceis particularly well suited to a ing incineration or landfill disposal heating and process heat appli-stoker boiler, the type most often of office waste paper and scrap cations. Thus, they do not havefound at coal-fired federal facili- wood from on-site construction utility-scale fuel requirements.ties. However, cofiring has been activities will total about $172,000successfully demonstrated and In addition, federal boilers needed per year. Net annual savings frompracticed in all types of coal for space heating typically operate the project, after subtracting theboilers, including pulverized- primarily during winter months. $30,000 per year needed to oper-coal boilers, cyclones, stokers, During summer months, waste ate the AF cubing facility, will beand fluidized beds. wood is often sent to the mulch about $254,000. An initial capital
Federal Technology Alertmarket, which makes the wood • Economics is the driving factor. energy efficiency and renewableunavailable for use as fuel. Thus, Project economics largely deter- energy projects. Projects can befederal coal-fired boilers could mine whether a cofiring proj- funded through Energy Savingsbecome an attractive winter mar- ect will be implemented. Performance Contracts (ESPCs),ket for local wood processors. This Selecting sites where waste Utility Energy Services Contracts,has been one of the driving fac- wood supplies have already or appropriations. Among thesetors behind a cofiring demonstra- been identified will reduce resources is a Technology-Specifiction at the Iron City Brewery overall costs. Larger facilities “Super ESPC” for Biomass andin Pittsburgh, Pennsylvania. with high capacity factors— Alternative Methane Fuels (BAMF), those that operate at high loads which facilitates the use of bio-These are some of the major policy year-round—can utilize more mass and alternative methaneand economic issues and barriers biomass and will realize fuels to reduce federal energy con-associated with implementing greater annual cost savings, sumption, energy costs, or both.biomass cofiring projects at assuming that wood suppliesfederal sites: are obtained at a discount in Through the BAMF Super ESPC, comparison to coal. This will FEMP enables federal facilities• Permit modifications may be also reduce payback periods. to obtain the energy- and cost- required. Permit requirements savings benefits of biomass and vary from site to site, but Conclusion alternative methane fuels at no modifications to existing up-front cost to the facility. More emissions permits, even for DOE FEMP, with the support of information about FEMP and limited-term demonstration staff at the DOE National Labor- atories and Regional Offices, offers BAMF Super ESPC contacts and projects, may be required for many services and resources to contract awardees is provided in cofiring projects. help federal agencies implement this Federal Technology Alert. Disclaimer This report was sponsored by the United States Department of Energy, Energy Efficiency and Renewable Energy, Federal Energy Management Program. Neither the United States Government nor any agency or contractor thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or useful- ness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or other- wise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency or contractor thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency or contractor thereof.
Federal Technology AlertContents Abstract .....................................................................................................2 About the Technology ..............................................................................3 Application Domain Cost-Saving Mechanisms Other Benefits Installation Requirements Federal-Sector Potential ............................................................................9 Estimated Savings and Market Potential Laboratory Perspective Application .............................................................................................11 Application Prerequisites Cost-Effectiveness Factors Where to Apply What to Avoid Equipment Integration Maintenance Equipment Warranties Codes and Standards Costs Utility Incentives Project Financing and Technical Assistance Technology Performance........................................................................17 Field Experience Fuel Supply and Cost Savings Calculations ...........................................17 Case Study — Savannah River Cofiring Project ....................................18 Facility Description Existing Technology Description New Technology Description Energy Savings Life-Cycle Cost Performance Test Results The Technology in Perspective ..............................................................20 Manufacturers.........................................................................................21 Biomass Pelletizing Equipment Boiler Equipment/Cofiring Systems Biomass and Alternative Methane Fuels (BAMF) Super ESPC Competitively Awarded Contractors For Further Information .........................................................................21 Bibliography ...........................................................................................21 Appendix A: Assumptions and Explanations for Screening Analysis .......23 Appendix B: Blank Worksheets for Preliminary Evaluation of a Cofiring Project ......................................................................................24 Appendix C: Completed Worksheets for Cofiring Operation at Savannah River Site ................................................................................28 Appendix D: Federal Life-Cycle Costing Procedures and BLCC Software Information .............................................................................31 Appendix E: Savannah River Site Biomass Cofiring Case Study: NIST BLCC Comparative Economic Analysis ........................................33 FEDERAL ENERGY MANAGEMENT PROGRAM — 1
Federal Technology AlertAbstract nity for federal energy managers This Federal Technology Alert was to use a greenhouse-gas-neutral produced as part of the New Tech-Biomass energy technologies con- renewable fuel while reducing nology Demonstration activitiesvert renewable biomass fuels to energy and waste disposal costs in the Department of Energy’sheat or electricity. Next to hydro- and enhancing national energy Federal Energy Management Pro-power, more electricity is gener- security. Specific requirements gram, which is part of the DOEated from biomass than from any will depend on the site. But in Office of Energy Efficiency andother renewable energy resource general, cofiring biomass in an Renewable Energy, to providein the United States. Biomass existing coal-fired boiler involves facility and energy managerscofiring is attracting interest modifying or adding to the fuel with the information they needbecause it is the most economical handling, storage, and feed sys- to decide whether to pursue bio-near-term option for introducing tems. Fuel sources and the type mass cofiring at their facilities.new biomass resources into today’s of boiler at the site will dictateenergy mix. This publication describes biomass fuel processing requirements. cofiring, cost-saving mechanisms, Biomass cofiring can be economi- and factors that influence its per- cal at federal facilities where most formance. Worksheets allow the or all of these criteria are met: reader to perform preliminary cal- current use of a coal-fired boiler, culations to determine whether access to a steady supply of com- a facility is suitable for biomass petitively priced biomass, high cofiring, and how much it would coal prices, and favorable regu- save annually. The worksheets latory and market conditions for also allow required biomass sup- renewable energy use and waste plies to be estimated, so managers reduction. Boilers at several fed- can work with biomass fuel bro- eral facilities were originally kers and evaluate their equipment designed for cofiring biomass needs. Also included is a case with coal. Others were modified study describing the design, oper- after installation to allow cofiring. ation, and performance of a bio- Some demonstrations—e.g., at the mass cofiring project at the DOEFigure 1. The NIOSH boiler plant wasmodified to cofire biomass with coal. National Institute of Occupational Savannah River Site in Aiken, Safety and Health (NIOSH) Bruce- South Carolina. A list of contacts ton Boiler plant in Pittsburgh, and a bibliography are alsoCofiring is the simultaneous com- Pennsylvania (Figure 1)—show included.bustion of different fuels in the that, under certain circumstances,same boiler. Cofiring inexpensive only a few boiler plant modifica-biomass with fossil fuels in exist- tions are needed for cofiring.ing boilers provides an opportu-2 — FEDERAL ENERGY MANAGEMENT PROGRAM
Federal Technology AlertAbout the Technology involves substituting biomass for cles, because biomass is a more a portion of the fossil fuel used volatile fuel. Biomass that doesBiomass is organic material from in a boiler. not meet these specifications isliving things, including plant likely to cause flow problems inmatter such as trees, grasses, Cofiring inexpensive biomass with the fuel-handling equipment orand agricultural crops. These fossil fuels in existing federal boilers incomplete burnout in the boiler.materials, grown using energy provides an opportunity for federal General biomass sizing require-from sunlight, can be good energy managers to reduce their ments for each boiler type men-sources of renewable energy energy and waste disposal costs tioned here are shown in Table 1.and fuels for federal facilities. while making use of a renewable fuel that is considered greenhouse-Wood is the most commonly used Table 1. Biomass sizing requirements. gas-neutral. Cofiring biomassbiomass fuel for heat and power. counts toward a federal agency’s Existing Type Size RequiredThe most economical sources of of Boiler (inches) goals for increasing the use ofwood fuels are wood residues from renewable energy or “green power” Pulverized coal ≤1/4manufacturers and mill residues, (environmentally benign electricsuch as sawdust and shavings; Stoker ≤3 power), and it results in a net costdiscarded wood products, such Cyclone ≤1/2 savings to the agency. Cofiringas crates and pallets; woody yard Fluidized bed ≤3 biomass also increases our use oftrimmings; right-of-way trim- domestic fuels, thus enhancingmings diverted from landfills; More detailed information follows the nation’s energy security.and clean, nonhazardous wood about the cofiring options fordebris resulting from construction This publication focuses on the stoker and pulverized-coal federaland demolition work. Using these most promising, near-term, boilers.materials as sources of energy proven option for cofiring—usingrecovers their energy value and solid biomass to replace a portion Stoker boilers. Most coal-fired boilersavoids the need to dispose of of the coal combusted in existing at federal facilities are stokers,them in landfills, as well as coal-fired boilers. This type of similar to the one shown in theother disposal methods. cofiring has been successfully schematic in Figure 2. Because demonstrated in nearly all coal- these boilers are designed to fireBiomass energy technologies con- fairly large fuel particles on travel- fired boiler types and configura-vert renewable biomass fuels to ing or vibrating grates, they are tions, including stokers, fluidizedheat or electricity using equip- the most suitable federal boiler beds, pulverized coal boilers, andment similar to that used for type for cofiring at significant cyclones. The most likely opportu-fossil fuels such as natural gas, biomass input levels. In these nities at federal facilities will beoil, or coal. This includes fuel- boilers, fuel is either fed onto found at those that have stokershandling equipment, boilers, the grate from below, as in under- and pulverized coal boilers. Thissteam turbines, and engine gener- feed stokers, or it is spread evenly is because the optimum operatingator sets. Biomass can be used in across the grate from fuel spread- range of cyclone boilers is muchsolid form, or it can be converted ers above the grate, as in spreader larger than that required at a fed-into liquid or gaseous fuels. Next stokers. In the more common eral facility, and few fluidized bedto hydropower, more electricity spreader-fired traveling grate stoker boilers have been installed at fed-is generated from biomass than boiler, solid fuel is mechanically eral facilities for standard, non-from any other renewable energy or pneumatically spread from the research uses.resource in the United States. front of the boiler onto the rear One of the most important keys of the traveling grate. Smaller par-Cofiring is a fuel-diversification ticles burn in suspension above to a successful cofiring operationstrategy that has been practiced the grate, while the larger particles is to appropriately and consistentlyfor decades in the wood products burn on the grate as it moves the size the biomass according to theindustries and more recently in fuel from the back to the front of requirements of the type of boilerutility-scale boilers. Several fed- the boiler. The ash is discharged used. Biomass particles can usuallyeral facilities have also cofired from the grate into a hopper at be slightly larger than coal parti-biomass and coal. Cofiring the front of the boiler. FEDERAL ENERGY MANAGEMENT PROGRAM — 3
Federal Technology Alert 03381101The retrofit requirements for cofir-ing in a stoker boiler will vary,depending on site-specific issues.If properly sized biomass fuel canbe delivered to the facility pre-mixed with coal supplies, on-site Gas burnerscapital expenses could be negligi-ble. Some facilities have multiple Hoppercoal hoppers that discharge onto Receivinga common conveyor to feed fuel bin Travelinginto the boiler. Using one of the grate Overfireexisting coal hoppers and the Boiler airassociated conveying equipment injectionfor biomass could minimize new Figure 2. Schematic of a typical traveling-grate spreader-stoker.capital expenses for a cofiringproject. Both methods have been Front end loadersuccessfully employed at federal to blend wood Metalstoker boilers for implementing and coal supplies detector Magnetic (coal and wooda biomass cofiring project. If blend is passed separator Dump conveyor through existing #1 Walking floor trailerneither of these low-cost options Dump or dump truck coal pulverizers)is feasible, new handling and Wood conveyor #2 pile Scalestorage equipment will need 03381102to be added. The cost of theseadditions is discussed later. Figure 3. Schematic of a blended-feed cofiring arrangement for a pulverized coal boiler.Pulverized coal boilers. There are twoprimary methods for cofiring bio- heat input basis. If the biomass is the NIOSH Bruceton boiler plantmass in a pulverized coal boiler. obtained at a significant discount in Pennsylvania and DOE’s Savan-The first method, illustrated in to current coal supplies, the addi- nah River Site in South Carolina—Figure 3, involves blending the tional expense may be warranted have been considering implement-biomass with the coal before the to offset coal purchases to a ing commercial cofiring applica-fuel mix enters the existing pul- greater degree. tions. Other federal sites withverizers. This is the least expensive cofiring experience include KImethod, but it is limited in the Application Domain Sawyer Air Force Base in Michi-amount of biomass that can be gan, Fort Stewart in Georgia, Puget The best opportunities for cofiringfired. With this blended feed Sound Naval Shipyard in Washing- biomass with fossil fuels at federalmethod, only about 3% or less ton, Wright- Patterson Air Force facilities are at sites with regularlyof the boiler’s heat input can be Base in Ohio, Brunswick Naval operating coal-fired boilers. Biomassobtained from biomass at full Air Station in Maine, and the cofiring has been successfullyboiler loads because of limitations Red River Army Depot in Texas. demonstrated in nearly all coal-in the capacity of the pulverizer. fired boiler types and configura- More than 100 U.S. companies orThe second method, illustrated in tions, including stokers, fluidized organizations have experience inFigure 4 on page 5, requires beds, pulverized coal boilers, and cofiring biomass with fossil fuels,installing a separate processing, cyclones. The least expensive and many cofiring boilers are inhandling, and storage system opportunities are most likely to operation today. Most are foundfor biomass, and injecting the be for stoker boilers, but cofiring in industrial applications, inbiomass into the boiler through in pulverized coal boilers may which the owner generates adedicated biomass ports. Although also be economically attractive. significant amount of biomassthis method is more expensive, it At least 10 facilities in the federal residue material (such as sawdust,allows greater amounts of biomass sector have had experience with scrap wood, bark, waste paper, orto be used—up to 15% more on a cardboard or agricultural residues biomass cofiring. Two facilities—4 — FEDERAL ENERGY MANAGEMENT PROGRAM
Federal Technology Alert Metal detector Magnetic separator Conveyor #1 Wood Disc screener pile Grinder Scale Front end Walking floor trailer 03381103 loader or dump truck Rotary airlock feeder Separator Air Intake Exhaust Bin Dedicated biomass vent injection Existing coal Injection ports Wood silo Boiler Scale Pressure blowerFigure 4. Schematic of a separate-feed cofiring arrangement for a pulverized coal boiler.like orchard trimmings and coffee project, and the next 10 states were Within each group in Table 2,grounds) during manufacturing. classified as having good potential. states are shown in alphabeticalUsing these residues as fuel allows See Table 2 and Figures 5 and 6. order, because slight variationsorganizations to avoid landfill in rankings result from selectingand other disposal costs and off- Table 2. States with most attractive weighting-factor values. The anal-sets some purchases of fossil fuel. conditions for biomass cofiring. ysis was intended simply to indi-Most ongoing cofiring operations cate which states have the most Cofiring helpful conditions for econom-are in stoker boilers in one of four Potential Stateindustries: wood products, agricul- ically successful cofiring projects.ture, textiles, and chemicals. High Connecticut It found that the Northeast, South- Potential Delaware east, Great Lakes states, andA screening analysis was done to Florida Washington State are the mostdetermine which states have the Maryland attractive locations for cofiringmost favorable conditions for a Massachusetts projects.financially successful cofiring proj- New Hampshire New Jersey Utility-scale cofiring projects areect. The primary factors consid- New York shown on the map in Figure 5.ered were average delivered state Pennsylvaniacoal prices, estimated low-cost These sites are in or near states Washingtonbiomass residue supply density identified by the screening model Good Alabama as having good or high potential(heat content in Btu of estimated Potential Georgiaavailable low-cost biomass resi- for cofiring. This increases confi- Indianadues per year per square mile of dence that the states selected by Michiganstate land area), and average state Minnesota the screening process were reason-landfill tipping fees. See Appendix North Carolina able choices. Figure 6 shows theA for a more detailed discussion. Ohio locations of existing federal coal- South Carolina fired boilers. There is good corre-The top 10 states in the analysis Tennessee spondence between the locationswere classified as having high Virginia of these facilities and the statespotential for a biomass cofiring identified as promising for cofiring. FEDERAL ENERGY MANAGEMENT PROGRAM — 5
Federal Technology Alert pay off the initial investment— by switching part of the fuel sup- ply to biomass. Federal facilities that operate coal-fired boilers but are not in states on the list in Table 2 could still be good candi- dates for cofiring if specific condi- tions at their sites are favorable. “Wild card” factors, such as the impact of a motivated project manager or biomass resource supplier, the local availability of biomass, and the fact that a large federal facility or campus could act as its own source of biomass fuel, capitalizing on 03381104 fuel cost reductions while avoid- High potential for a Good potential for a biomass cofiring project biomass cofiring project ing landfill fees. These factors Locations of existing utility Locations of existing operational could easily tip the scales in power plants cofiring biomass coal plants within the Federal System favor of a particular site. TheFigure 5. States with most favorable conditions for biomass cofiring, based on coal-fired boilers in Alaskahigh coal prices, availability of biomass residues, and high landfill tipping fees. could be examples of good candidates not located in highly rated states because of WA a long heating season, large (57) NH MT VT (49) ME size, and very high coal prices. ND (50) (46) OR (19) (26) MN (34) (56) MA The map in Figure 6 indicates ID SD WI NY (48) (26) WY MI (71) average landfill tipping fees for (29) (33) (32) RI (23) IA each state. It also shows cities NV NE PA(51) NJ (41) (15) (24) (31) CT in which fairly recent local bio- UT IN OH (74)(61) CO IL (26) (29) WA (29) mass resource supply and cost CA (16) KS MO (25) (39) VA MD DE (29) (25) (27) KY(27) (38) (43) (47) studies have been performed, AZ NC(30) as reported in Urban Wood Waste NM OK TN(28) (20) AR (16) (21) Resource Assessment (Wiltsee 1998). (18) MS AL GA SC Additional information on poten- TX (19) (25) (25) (29) AK (23) LA tial biomass resource supplies near (22) federal facilities can be obtained (42) FL (41) from the DOE program manager HI (50) for the Technology-Specific Super 03381105 ESPC for Biomass and Alternative High potential for a Good potential for a Methane Fuels, or BAMF; contact biomass cofiring project biomass cofiring project information can be found later in (##) State average tipping Locations of recent local fee ($/ton)* biomass supply studies this publication. To encourage *Source: Chartwell Information Publishers, Inc., 1997. new projects under the BAMF Super ESPC, the National EnergyFigure 6. Average tipping fee and locations of local biomass supply studies Technology Laboratory (NETL)(Chartwell 1997, Wiltsee 1998). has compiled a database thatCoal-fired federal boilers in the biomass if annual coal use is high identifies federal facilities within20 states indicated in the study enough to obtain significant 50 miles of 10 or more potentialwould be promising for cofiring annual cost savings—enough to sources of wood waste.6 — FEDERAL ENERGY MANAGEMENT PROGRAM
Federal Technology AlertCost-Saving Mechanisms mated the quantities and costs of dry biomass would have a heatingCofiring operations are not imple- unused and discarded wood resi- value of about 7,000 Btu/lb, com-mented to save energy—they are dues in the United States, large pared with an average of 11,500implemented to reduce energy quantities of biomass are available Btu/lb for the coal used at DoDcosts as well as the cost of other at delivered costs well below the facilities. Each ton of biomassfacility operations. In a typical $2.10 per million Btu average will thus offset 7,000/11,500 =cofiring operation, the boiler price of coal at the DoD facilities. 0.61 ton of coal. If the biomassrequires about the same heat Coal prices at other federal facili- is used to replace coal at $49/ton,input as it does when operating ties are likely to be similar. each ton of biomass is worthin a fossil-fuel-only mode. When $49/ton x 0.61 = $30 in fuel cost For example, if 15% of the coalcofiring, the boiler operates to savings. The typical cost of pro- used at a boiler were replaced bymeet the same steam loads for cessing biomass waste material biomass delivered to the plant forheating or power-generation into a form suitable for use in a $1.25 per million Btu, annual fueloperations as it would in fossil- boiler is $10 per ton, so the net cost savings for the average DoDfuel-only mode; usually, no costs savings per ton of biomass boiler described above would bechanges in boiler efficiency residues could be about $56: more than $120,000. Neither theresult from cofiring unless a $66/ton for the fuel and landfill cofiring rate of 15% of the boilersvery wet biomass is used. With cost savings minus $10/ton for total heat input, nor the deliveredno change in boiler loads, and the biomass processing cost. This price of $1.25 per million Btu, isno change in efficiency, boiler assumes that the biomass is avail- unrealistic, especially for stokerenergy usage will be the same. able at no additional transporta- boilers. Higher cofiring rates andThe primary savings from cofiring tion costs, as is the case at the lower biomass prices are commonare cost reductions resulting from Savannah River Site. in current cofiring projects. Note(1) replacing a fraction of high- that the cost of most biomass If the average DoD facility using acost fossil fuel purchases with residues will range from $2 to coal-fired boiler could obtain bio-lower cost biomass fuel, and (2) $3 per million Btu, so successful mass fuel by diverting its ownavoiding landfill tipping fees or cofiring project operators must residues from landfill disposal,other costs that would otherwise try to obtain the biomass fuel the net annual cost savings wouldbe required to dispose of the at a low price. be about $560,000 per year. Thisbiomass. would require about 10,000 tons The average landfill tipping fee inAccording to data obtained from of biomass residues per year, a the United States is about $36 perthe Defense Energy Support quantity higher than most federal ton of material dumped. AverageCenter (DESC), the average facilities generate internally. The tipping fees for each state aredelivered cost of coal for 18 coal- savings generated by a real cofir- shown in Figure 6. If significantfired boilers operated by the ing project would be expected to quantities of clean biomassDepartment of Defense (DoD) fall somewhere between the residues—such as paper, card-was about $49 per ton in 1999, two examples given here— board, or wood—are generatedor about $2.10 per million Btu. between $120,000 and $560,000 at a federal site, and if some of(The average coal heating value per year. They would probably that material can be diverted fromfor those boilers is about 11,500 depend on using some biomass landfill disposal and used as fuelBtu/lb) Coal costs for those facili- materials generated on site and in a boiler, the savings generatedties ranged from $1.60 to $3 per some supplied by a third party. would be equivalent to aboutmillion Btu, depending on the $66 per ton of biomass: $36/tonlocation, coal type, and annual Other Benefits by avoiding the tipping fee, andquantity consumed. The average $30/ton by replacing the coal When used as a supplemental fuelannual coal cost for these boilers with biomass. Since biomass has in an existing coal boiler, biomasswas about $2 million and ranged a lower heating value than coal, can provide the following bene-from $28,000 to $8.9 million per it takes more than one ton of bio- fits, with modest capital outlaysyear. According to three independ- mass to offset the heat provided for plant modifications:ently conducted studies that esti- by one ton of coal. A ton of fairly FEDERAL ENERGY MANAGEMENT PROGRAM — 7
Federal Technology Alert• Reduced fuel costs. Savings in • Renewable energy when needed. modifications to existing opera- overall production costs can Unlike other renewable energy tional procedures, such as increas- be achieved if inexpensive technologies like those based ing over-fire air, may also be nec- biomass fuel sources are avail- on solar and wind resources, essary. Increased fuel feeder rates able (e.g., clean wood waste). biomass-based systems are are also needed to compensate for Biomass fuel supplies at prices available whenever they are the lower density and heating 20% or more below current needed. This helps to accelerate value of biomass. This does not coal prices will usually pro- the capital investment payoff usually present a problem at fed- vide the cost savings needed. rate by producing more heat eral facilities, where boilers typi-• Reduced sulfur oxide and nitrogen or power per unit of installed cally operate below their rated oxide emissions. Because of dif- capacity. output. When full rated output ferences in the chemical is needed, the boiler can be oper- • Market-ready renewable energy composition of biomass and ated in a coal-only mode to avoid option. Cofiring offers a fast- coal, emissions of acid rain derating. track, low-cost opportunity precursor gases—sulfur oxides to add renewable energy Expected fuel sources and boiler (SOx) and nitrogen oxides capacity economically at type dictate fuel processing (NOx)—can be reduced by federal facilities. requirements. For suspension replacing coal with biomass. firing in pulverized coal boilers, Because most biomass has • Fuel diversification. The ability biomass should be reduced to a nearly zero sulfur content, to operate using an additional particle size of 0.25 in. or smaller, SOx emissions reductions fuel source provides a hedge with moisture levels less than occur on a one-to-one basis against price increases and 25% when firing in the range with the amount of coal supply shortages for existing of 5% to 15% biomass on a heat (heat input) offset by the fuels such as stoker coals. In input basis. Equipment such as biomass. Reducing the coal a cofiring operation, biomass supply to the boiler by 10% hoggers, hammer mills, spike rolls, can be viewed as an opportu- will reduce SOx emissions and disc screens may be required nity fuel, used only when the by 10%. Mechanisms that to properly size the feedstock. price is favorable. Note that lead to NOx savings are Local wood processors are likely administrative costs could more complicated, and to own equipment that can ade- increase because of the need relative savings are typically quately perform this sizing in to purchase multiple fuel less dramatic than the SOx return for a processing fee. Other supplies; this should be reductions are, on a percent- boiler types (cyclones, stokers, considered when evaluating age basis. and fluidized beds) are better suited this benefit. to handle larger fuel particles.• Landfill cost reductions. Using • Locally based fuel supply. The waste wood as a fuel diverts Two common forms of processed most cost-effective biomass the material from landfills biomass are shown in Figure 7, fuels are usually supplied and avoids landfill disposal along with a typical stoker coal, from surrounding areas, so costs. shown in the center of the photo. economic and environmental Recent research and demonstra-• Reduced greenhouse-gas emissions. benefits will accrue to local tion on several industrial stoker Sustainably grown biomass is communities. boilers in the Pittsburgh area has considered a greenhouse-gas- shown that wood chips (on the neutral fuel, since it results in Installation Requirements right) are preferable to mulch-like no net carbon dioxide (CO2) Specific requirements depend on material (on the left) for cofiring in the atmosphere. Using bio- the site that uses biomass in cofir- with coal in stoker boilers that mass to replace 10% of the coal ing. In general, however, cofiring have not been designed or in an existing boiler will reduce biomass in an existing coal boiler previously reconfigured for the net greenhouse-gas emis- requires modifications or addi- multifuel firing. The chips are sions by approximately 10% if tions to fuel-handling, processing, similar to stoker coal in terms the biomass resource is grown storage, and feed systems. Slight of size and flow characteristics; sustainably.8— FEDERAL ENERGY MANAGEMENT PROGRAM
Federal Technology Alerttherefore, they cause minimal The potential savings resulting occur. In terms of CO2 reductions,problems with existing coal- from using the technology at this would be equivalent to remov-handling systems. Using a mulch- typical federal facilities with ing about 1,000 average-sizedlike material, or a biomass supply existing coal-fired boilers were automobiles from U.S. highways.with a high fraction of fine parti- estimated as part of the technol- Additional indirect benefits couldcles (sawdust size or smaller) can ogy-screening process of FEMP’s also occur. If the biomass fuelcause periodic blockage of fuel New Technology Demonstration would otherwise be sent to a land-flow openings in various areas activities. Payback periods are fill to decay over a period of time,of the conveying, storage, and usually between one and eight methane (CH4) would be releasedfeed systems. These blockages years, and annual fuel cost sav- to the atmosphere as a by-productcan cause significant maintenance ings range from $60,000 to of the decomposition process,increases and operational prob- $110,000 for a typical federal assuming no landfill-gas-capturinglems, so fuel should be processed boiler. Savings depend on the system is installed. Since CH4 isto avoid those difficulties. With availability of low-cost biomass 21 times more powerful than CO2properly sized and processed feedstocks. The savings would in terms of its ability to trap heatbiomass fuel, cofiring operations be greater if the federal site can in the atmosphere and increasehave been implemented success- avoid landfill costs by using its the greenhouse effect, cofiringfully without extensive modifica- own clean biomass waste mate- at one typical coal-fired federaltions to equipment or operating rials as part of the biomass fuel facility could avoid decompositionprocedures at the boiler plant. supply. processes that would be equiva- lent to reducing an additional Estimated Savings and MarketFederal-Sector Potential 29,000 tons of CO2 emissionsPotential per year. The National Renewable EnergyA large percentage of federal facili- Laboratory (NREL) conducted a Payback periods using cofiringties with coal-fired boilers have study for FEMP of the economic at suitable federal facilities arethe potential to benefit from this and environmental impacts of between one and eight years.technology. However, as noted, biomass cofiring in existing fed- Annual cost savings range fromthe potential is highest in areas eral boilers, as well as associated about $60,000 to $110,000 forwith high coal prices, easy-to- savings. Results of the study are a typical federal boiler, if low-obtain biomass resources, and presented in Tables 3 through 6 cost biomass feedstocks are avail-high landfill tipping fees. on pages 10 and 11. As shown in able. There are more than 1500 Table 6, cofiring bio- industrial-scale stoker boilers in mass with coal at operation in the United States. one typical coal- If federal technology transfer fired federal facility efforts result in cofiring projects will replace almost at 50 boilers (this is about 7% 3,000 tons of coal of existing U.S. stokers), the per year, could resulting CO2 reductions would divert up to about be about 405,000 tons/yr (the 5,000 tons of bio- equivalent of removing about mass from landfills, 50,000 average-size cars from U.S. and will reduce net highways), and SO2 reductions carbon dioxide would be about 6,700 tons/yr. (CO2) emissions by If all biomass materials used in more than 8,000 these boilers were diverted from tons per year and landfills with no gas capture, theFigure 7. Comparison of two biomass residues with coal. sulfur dioxide (SO2) greenhouse-gas equivalent of anBecause they are similar in size and flow characteristics, emissions by about additional 1.45 million tons ofwood chips (right) flow more like coal (center) in stoker 136 tons per year. CO2 emissions would be avoided.boilers. Wood chips can thus be used in existing boilers Reductions in NOxwith minimal modifications to fuel-handling systems. emissions could also (Continued on page 11)Mulch-like processed wood (left) is more problematic. FEDERAL ENERGY MANAGEMENT PROGRAM — 9
Federal Technology AlertTable 3. Example economics of biomass cofiring in power generation applications (vs. 100 percent coal). Net Example Heat Total Annual Production Production Plant from Biomass Unit Cost for Cost Payback Cost, no Cost, with Size Biomass Power Cost Cofiring Savings Period Cofiring Cofiring Boiler Type (MW) (%) (MW) ($/kW)1 Retrofit ($) ($/yr)2 (years) (¢/kWh)3 (¢/kWh)3 Stoker (low cost) 15 20 3.0 50 150,000 199,760 0.8 5.25 5.03 Stoker (high cost) 15 20 3.0 350 1,050,000 199,760 5.3 5.25 5.03 Fluidized bed 15 15 2.3 50 112,500 149,468 0.8 5.41 5.24 Pulverized coal 100 3 3.0 100 300,000 140,184 2.1 3.26 3.24 Pulverized coal 100 15 15.0 230 3,450,000 700,922 4.9 3.26 3.15Notes:1Unit costs are on a per kW of biomass power basis (not per kW of total power).2Net annual cost savings = fuel cost savings – increased O&M costs.3Based on data obtained from EPRIs Technical Assessment Guide, 1993, EIAs Costs of Producing Electricity, 1992, UDIs Electric Power Database, EPRI/DOEs Renewable Energy Technology Characterizations, 1997, coal cost of $2.10/MBtu, biomass cost of$1.25/MBtu, and capacity factor of 70%.Table 4. Example environmental impacts of cofiring in power generation applications (vs. 100 percent coal). Example Annual Annual Annual Plant Heat Reduced Biomass CO2 SO2 NOx Size from Coal Use Used Savings Savings Period Boiler Type (MW) Biomass (tons/yr) (tons/yr)1 (tons/yr)2 (tons/yr) (tons/yr) Stoker (low cost) 15 20% 10,125 16,453 27,843 466 N/A Stoker (high cost) 15 20% 10,125 16,453 27,843 466 N/A Fluidized bed 15 15% 7,578 12,314 20,839 349 N/A Pulverized coal 100 3% 7,429 12,072 20,430 342 N/A Pulverized coal 100 15% 37,146 60,362 102,151 1,709 N/ANotes:1Depending on the source of biomass, “biomass used” could be avoided landfilled material.2Carbon savings can easily be calculated from CO savings (i.e., carbon savings = 12/44 x CO savings). 2 2Table 5. Example economic of biomass cofiring in heating applications (vs. 100 percent coal). Example No. of Heat from Biomass Total Cost Net Annual Payback Boiler Size Boilers Biomass Capacity Unit Cost for Cofiring Cost Savings Period (steam lb/hr) at Site (steam lb/hr) (steam lb/hr) ($/lb/hr)1 Retrofit ($) ($/yr)2 (years) 120,000 2 15% 36,000 2.8 100,075 41,628 2.4Notes:1Unit costs are on a per unit of biomass capacity basis (not per unit of total capacity).2Assumptions: coal cost of $2.10/MBtu and capacity factor of 25% (based on data from coal-fired federal boilers), biomass cost of$1.25/MBtu.10— FEDERAL ENERGY MANAGEMENT PROGRAM
Federal Technology AlertTable 6. Potential environmental impact of cofiring in heating applications (vs. 100 percent coal). Annual Annual Annual No. of Reduced Biomass CO2 SO2 NOx Cofiring Coal Use Used Savings Savings Period Projects1,2 (tons/yr) (tons/yr)3 (tons/yr)4 (tons/yr) (tons/yr) 1 2,947 5,057 8,103 136 N/A 2 5,893 10,114 16,206 271 N/A 10 29,466 50,570 81,030 1,355 N/A 50 147,328 252,851 405,151 6,777 N/ANotes:1There are approximately 1500 industrial stoker boilers operating today.2Assumptions for the average project were: 120,000 lb/hr steam capacity per boiler, 2 boilers at site, 15% heat from biomass, and a 25% capacity factor.3Depending on the source of biomass, “biomass used” could be avoided landfilled material.4Carbon savings can easily be calculated from CO savings (i.e., carbon savings = 12 / 44 x CO savings). 2 2Laboratory Perspective that, in general, NOx emissions be used more easily as fuel atSince the 1970s, DOE and NETL decrease with cofiring as a result existing coal-fired facilities. Inhave worked with alternative fuels of the lower nitrogen content of a separate project with fundingsuch as solid waste and refuse- most woody biomass in relation from NETL, the University ofderived fuel. In 1995, NETL, to coal, and the greater volatility Missouri-Columbia’s CapsuleSandia National Laboratories, and of biomass in relation to coal. Pipeline Research Center exam-NREL sponsored a workshop that The greater volatility of biomass ined the potential for compactingled to several projects evaluating results in a natural staging of the various forms of biomass intotechnical and commercial issues combustion process that can small briquettes or cubes for useassociated with biomass cofiring. reduce NOx emissions to levels as supplemental fuels at existingThese projects included research below those expected on the coal-fired boilers. The results indi-conducted or sponsored by NETL, basis of fuel nitrogen contents. cated that biomass fuel cubesNREL, Sandia, and Oak Ridge could be manufactured and deliv- DOE, NETL, and the Electric PowerNational Laboratory (ORNL) on ered to a power plant for as little Research Institute (EPRI) also col-char burnout; ash deposition; as $0.30 per million Btu, or less laborated on short-term demon-NOx behavior; cofiring demon- than $5 per ton. This price stration projects. Several of thestration projects using various included all capital and operating demonstrations took place atboiler types, coal/biomass feed- costs for the manufacturing facility federal facilities in the Pittsburghstock combinations, and fuel plus transportation costs within area. They found no significanthandling systems; reburning for a 50-mile radius. The analysis impact on boiler efficiency at lowenhanced NOx reduction; and the assumed the facility would levels of cofiring. Fuel procure-use of ash. These efforts have led collect a $15-per-ton tipping ment, handling, and preparationto improved and documented fee for biomass delivered to the were found to require specialknowledge about the impacts site. See the bibliography for attention.of cofiring biomass with coal more detailed information onin a wide range of circumstances. In addition, DOE’s Idaho National biomass cofiring research activities Energy and Environmental Labor- and published results of researchResults from a joint Sandia/NETL/ atory (INEEL) and DOE’s Savan- led by DOE and its laboratories.NREL project found that in terms nah River Site have biomass-of slagging and fouling, wood was cubing equipment that can Applicationmore benign than herbaceous convert paper and wood waste This section addresses technicalcrops. It has also been shown materials into a form that can aspects of biomass cofiring in FEDERAL ENERGY MANAGEMENT PROGRAM — 11
Federal Technology Alertcoal-fired boilers, including the access to local expertise in dirt. It may also be possiblerange of situations in which cofir- collecting and processing to arrange storage throughing technology can be used best. waste wood. This expertise the biomass fuel provider.First, prerequisites for a successful can be found primarily • Receptive plant operators at thebiomass cofiring application are among companies specializ- federal facility. At the verydiscussed, as well as the factors ing in materials recycling, least, increases will bethat influence the cost-effective- mulch, and wood products. necessary in administrativeness of projects. Design and inte- • Boiler plant equipped with a bag- activities associated withgration considerations are also house. Cofiring biomass with adding a new fuel to a boilerdiscussed and include equipment coal has been shown to plant’s fuel mix. In addition,and installation costs, installation increase particulate emissions new or additional boiler con-details, maintenance, and permit- in some applications in com- trol and maintenance proce-ting issues. parison to coal-only opera- dures will be required to use tion. If the existing facility is biomass effectively. AsApplication Prerequisites already equipped with a bag- opposed to a capital improve-The best opportunities for cofiring house or cyclone separation ment project, which requiresoccur at sites in which many of devices, this should not be a one-time installation andthe following criteria apply: significant problem; in other minimal attention afterwards• Existing, operational coal-fired words, it should not cause (such as equipment upgrades), boiler. It is possible to cofire noncompliance with particu- a cofiring operation requires biomass with fossil fuels late emissions standards. The ongoing changes in fuel pro- other than coal; however, existing baghouse or cyclone curement, fuel-handling, and the similarities in the fuel- typically provides sufficient boiler control operations. handling systems required particulate filtration to allow Receptive boiler plant opera- for both coal and biomass stack gases to remain in com- tors and management are (because they are both solid pliance with air permits. How- therefore instrumental in fuels) usually make cofiring ever, some small coal-fired implementing and sustaining less expensive at coal-fired boilers are not equipped with a successful cofiring project. facilities. An exception could these devices. Instead, they • Favorable regulatory climate for be cofiring applications in use methods such as natural renewable energy. As of Febru- which the biomass fuel is gas overfiring to reduce par- ary 2003, 28 states had either gas piped to the boiler from ticulate emissions. In such enacted electricity restructur- a nearby landfill. Cofiring cases, a new baghouse may ing legislation or issued orders with landfill gas has been be required to permit cofiring to open their electricity mar- done in both coal-fired and biomass at significant input kets to competition. Most of natural-gas-fueled boilers, levels, and this would increase these states have established but is less common than project costs significantly. some type of incentive pro- solid-fuel cofiring because of • Storage space available on site. gram to encourage more the need for a large boiler Unless the biomass is imme- installations of renewable very close to the landfill. diately fed into a boiler’s energy technologies. Since• Local expertise for collecting and fuel-handling system upon biomass is a renewable energy processing biomass. Most boiler delivery, a temporary staging resource, some states may operators at federal facilities area at the boiler plant will provide favorable conditions are not likely to be interested be needed to store processed for implementing a cofiring in purchasing and operating biomass supplies. An ideal project through incentive equipment to process biomass storage facility would have programs, technical assis- into a form that can be used at least a concrete pad and tance, or flexible permitting as boiler fuel.Thus, it is advan- a roof to minimize the accu- procedures. tageous for the facility to have mulation of moisture and12 — FEDERAL ENERGY MANAGEMENT PROGRAM