United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

Research

Paper

FPL 415

A Wood and Bark

Fuel Economics

Computer Program

(FEP)
Abstract

Demands for wood residue-type materials are expected

to create competing alternate uses. The objectives of

the wood and bark fuel economics computer program

presented are to provide (1) a means to assess the

relative energy values of wood and bark for use as fuel,

and (2) pre-engineering assessments of the potential

investment that may be justified by benefits gained

through modification of wood/bark fuel systems. It is

suggested that more advanced engineering and

financial analytic methods be used for further

evaluation whenever this program indicates favorable

venture likelihoods.
United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory1

Research

Paper

FPL 415

September 1982

A Wood and Bark

Fuel Economics

Computer Program

(FEP)

By

GEORGE B. HARPOLE,

PETER J. INCE,

JOHN L. TSCHERNITZ,

and

EDWARD BILEK

Introduction

Forest products harvesting and manufacturing

processes are expected to provide large and continuing

supplies of wood and bark residues. At the same time,

the demand for wood residue-type materials for

production of wood-fiber based products as well as

wood and bark fuels is expected to create competing

utilization alternatives. Primary objectives of the fuel

economics computer program (FEP) presented here are:

(I) to provide a means for assessing the relative energy

values of fossil fuels and wood/bark fuels, and (2) to

provide pre-engineering assessments of the potential

investment that may be justified by benefits gained

through modification of systems to burn wood/bark

fuels.

The FEP computer program utilizes readily available

fuel and economics information, standard combustion

equations, and discounted cash flow analytic

techniques. Because the FEP program is designed for

preliminary assessments of wood/bark fuel use

1

 Maintained in Madison, Wis. in cooperation with the University of

Wisconsin.

2

 Italicized numbers in parenthesis refer to literature cited at the end of

this report.

opportunities it is suggested that more advanced

engineering and financial analytic methods be used for

further evaluation whenever favorable venture

likelihoods are indicated by the FEP program (1-4)2

The computer program presented is written in

FORTRAN. The program listing may be found in

appendix A.

Program Objectives

The computational objectives of the fuel economics

program (FEP) are:

(1) To compute steam heat recovery, or theoretical

wood drying capacities of exhaust gasses from

different fuels (Figs. I and 2).

(2) To compute fuel costs per million Btu’s of steam, or

costs per thousand pounds of evaporated water

(Figs. I and 2).

(3) To compute volumes of fuel types required to yield

specified heat requirements, at a least cost from

among alternatives (Fig. 3).

(4) To compute prospective savings in fuel costs if

wood and bark residue are used as alternatives for

oil, gas or other fuel (Fig. 3), and to capitalize such

benefits into assignments to working capital

requirements and justifiable facilities investment

(Fig. 4).
********** FUEL TYPE ASSUMPTIONS AND ESTIMATES OF REQUIREMENTS, COSTS AND SAVINGS ( 450. DEG.F STACK TEMP.)

**********

- - - -HEAT-ENERGY VALUES- - - -

UNIT UNITS AVAIL. CU.FT. SPEC. M.C. $ COST HIGHER VALUE HEAT TO STEAM

BASIS ANNUALLY SOLID GRAV. (WET) PER UNIT. MBTU/UNIT MBTU/UNIT $/MMBTU

A) CURRENT SOURCE

1) OIL BBL 5000. .00 .000 .0000 $ 34.00 6000. 4950.00 $ 6.87

B) PROPOSED SOURCE(S)

2) N RED OAK

3) SO PINE

4) Y BIRCH

5) DOUG FIR

6) Y POPLAR

7) P PINE

8) W HEMLOCK

9) RED ALDER

10) E SPRUCE

UNIT 600. 72.00 .560 .4400 $ 60.00 24237. 16739.02 $ 3.58

UNIT 400. 72.00 .470 .2400 $ 60.00 21926. 16485.05 $ 3.64

UNIT 800. 72.00 .550 .4300 $ 60.00 23087. 16026.88 $ 3.74

UNIT 100. 72.00 .450 .2700 $ 60.00 18606. 13887.79 $ 4.32

UNIT 900. 72.00 .400 .4500 $ 60.00 17312. 11914.09 $ 5.04

UNIT 300. 72.00 .380 .2900 $ 60.00 15541. 11559.98 $ 5.19

UNIT 500. 72.00 .380 .4600 $ 60.00 14516. 9915.90 $ 6.05

UNIT 700. 72.00 .370 .4900 $ 60.00 13303. 8882.56 $ 6.75

UNIT 200. 72.00 .320 .3400 $ 60.00 11649. 8458.46 $ 7.09

* HIGHER OF COST OR MARKET. IE: OPPORTUNITY COST IS INCLUDED MERE.

NOTE--M IS THOUSANDS, MM IS MILLIONS.

Figure 1.—Printed output of heat-energy to steam

and costs for fuel types analyzed.

(M151-269)

**********

FUEL TYPE ASSUMPTIONS AD ESTIMATES OF REQUIREMENTS, COSTS\ AND SAVINGS **********

UNIT UNITS AVAIL. CU.FT. SPEC. M.C. $ COST

BASIS ANNUALLY SOLID GRAV: (WET) PER UNIT*

- - - -HEAT-ENERGY VALUES- - - -

HIGHER VALUE EFFECTIVE EVAPORATION

MBTU/UNIT *H2O/UNIT $/M#H2O

6000. 3529.41 $ 9.63

A) CURRENT SOURCE

1) OIL BBL 5000.

B) PROPOSED SOURCE(S)

2) SO PINE

3) N RED OAK

4 ) Y BIRCH

5) DOUG FIR

6 ) Y POPLAR

7) P PINE

8 ) W HEMLOCK

9) RED ALDER

10) E SPRUCE

UNIT

UNIT

UNIT

UNIT

UNIT

UNlT

UNIT

UNIT

UNIT

400.

600.

800.

100.

900.

300.

500.

700.

200.

* HIGHER OF COST OR MARKET. IE: OPPORTUNITY COST

NOTE--M IS THOUSANDS, MM IS MILLIONS.

.00 .000 .0000 $ 34.00

72.00

72.00

72.00

72.00

72.00

.470 .2400 $ 60.00 21926. 11148.73 $ 5.38

.560 .4400 $ 60.00 24237. 11108.77 $ 5.40

.550 .4300 $ 60.00 23087. 10564.31 $ 5.68

.450 .2700 $ 60.00 18606. 9179.32 $ 6.54

.400 .4500 $ 60.00 17312. 7882.03 $ 7.61

.380 .2900 $ 60.00 15541. 7592.41 $ 7.90

.380 .4600 $ 60.00 14516. 6319.15 $ 9.49

.370 .4900 $ 60.00 13303. 5512.99 $ 10.88

.320 .3400 $ 60.00 11649. 5418.89 $ 11.07

HERE.

72.00

72.00

72.00

72.00

IS INCLUDED

Figure 2.—Printed output of effective evaporative

capacities and costs for fuel types analyzed.

(M151-268)

* * * * PROSPECTUS REQUlREMENTS ( 58000. MlLLION STEAM-HEAT BTU'S/YEAR) AND ANNUAL SAVINGS * * * *

--------ANNUAL VOLUMES REQUIRED AT VARIOUS MOISTURE CONTENTS (WET BASIS)--------

UNIT AT GIVEN AT HIGHER MOISTURE CONTENT* AT LOWER MOISTURE CONTENT * *

BASlS M.C. + 5 PCT. + 10 pct. + 20 PCT. -5 PCT. -10 PCT. -20 PCT.

PROPOSED SOURCES

A) CURRENT SOURCE

1) OIL

B) PROPOSED SOURCE(S)

2) N RED OAK

3) SO PINE

4) Y BIRCH

5) DOUG FIR

6) Y POPLAR

7) P PINE

8) W HEMLOCK

9) RED ALDER

10) E SPRUCE

AVG. COST/MMBTU

BBL

UNIT

UNIT

UNIT

UNIT

UNIT

UNIT

UNIT

UNIT

UNlT

EST. ANNUAL SAVINGS

360.8 710.1 1079.2 4078.4 93.3 . 0 . 0

600.0

400.0

800.0

100.0

900.0

300.0

500.0

700.0

. 0

$ 5.08 $

$ 103.7M $

600.0

400.0

800.0

100.0

900.0

300.0

. 0

. 0

. 0

5.60

73.7M

600.0

400.0

800.0

100.0

900.0

300.0

500.0

700.0

. 0

$ 4.50 $

$ 137.2M $

600.0

400.0

800.0

100.0

900.0

300.0

500.0

611.7

. 0

4.36

145.7M

600.0

400.0

800.0

100.0

900.0

300.0

500.0

407.0

. 0

$ 4.15

$ 158.0M

600.0

400.0

800.0

100.0

900.0

300.0

500.0

700.0

. 0

$ 4.66

$ 128.1M

600.0

400.0

800.0

100.0

900.0

300.0

500.0

700.0

. 0

$ 4.86

$ 116.2M

* WOOD FUEL CALCULATIONS ASSUME 40-PCT EXCESS AIR AND 4-PCT HEAT LOSS FROM UNBURNED

FUEL, RADIATION AND UNACCOUNTED LOSSES. THE PROGRAM ALLOWS WOOD FUEL MOISTURE

CONTENTS TO DROP BELOW 0-PCT BUT DISQUALIFIES A FUEL TYPE WHEN MOISTURE CONTENT

EXCEEDS 65-PCT. NON-WOOD FUEL ASSUMES A BOILER EFFICIENCY OF 82.5-PCT UNLESS

OTHERWISE SPECIFIED BY DATA ENTRY.

NOTE--M IS THOUSANDS, MM IS MILLIONS.

Figure 3.—Printed output of fuel requirements and

costs for specified heat-energy requirement.

(M151-270)

2
********** CAPITALIZED VALUE OF PROSPECTIVE FUEL SAVINGS **********

ECON. LIFE OF PROSPECTUS = 10 YRS AD VALOREM COSTS ( 8.50 PCT. OF CAP. VAL.) = $ 26.7M

AVERAGE FUEL INVENTORY SUPPLY = 2.4 WKS CHANGE IN OTHER OPER. COSTS (DOLLARS) = $ 20.0M

AVERAGE ANNUAL RATE OF INFLATION = .0800 FIRST YEAR INV. TAX CREDIT (10.00 PCT. OF CAP. VAL.) = $ 31.4M

REQUIRED IRR TO INVESTMENT = .2000 EFFECTIVE TAX RATE = .4500

CAPITALIZED VALUES FOR . . .

GIVEN ---CHANGE (+ OR -) IN CAPITALIZED VALUES DUE TO CHANGE IN MOISTURE CONTENT---

PROSPECTUS INCREASE OF MOISTURE CONTENT DECREASE OF MOlSTURE CONTENT

+5 PCT. +10 PCT. +20 PCT. -5 PCT. -10 PCT. -20 PCT.

FAClLITIES INVESTMENT 313.8M $ -36.0M $ -74.1M $ -162.0M $ 27.6M $ 53.5M $ 91.3M

WORKING CAPITAL $

$

14.6M $ -.1M $ -.2M $ -3.4M $ .1M $ -.1M $ -.5M

TOTAL $ 328.5M $ -36.1M $ -74.3M $ -165.3M $ 27.7M $ 53.4M $ 90.8M

NOTE--M IS THOUSANDS, MM IS MILLIONS.

  PROGRAM ASSUMPTIONS ** **

1) STRAIGHT LINE DEPREClATION IS TAKEN ON ALL DEPRECIABLE ASSETS (IE: FACILITIES).

2) INITIAL INVESTMENTS (FACILITIES AND WORKING CAPITAL) ARE COMPUTED FROM DISCOUNTED PRESENT VALUE OF ANNUAL NET FUEL SAVINGS.

SUBSEQUENT INVESTMENT REQUIREMENTS--SUCH AS INCREASES IN WORKING CAPITAL REQUIREMENTS AND REPLACEMENT OF MOBILE EQUIPMENT,

ETC.--ARE NOT INCLUDED.

Figure 4.—Printed output of economically

justified facilities investment costs.

(M151-271)

(5) To compute capitalized values of cost changes

associated with changes in specified moisture

contents of wood/bark fuels considered (Fig. 4).

There are also two important computational

characteristics of the program:

(1) for simplicity, computations of sensitivities to

changes in fuel moisture content will allow adjusted

wood/bark fuel moisture contents to drop below zero

percent moisture content (Fig. 1 and 2); (2) the program

will only compute capitalized values when annual fuel

savings exceed annual operating costs and working

capital requirements. (See Tables 1-3 for conversion

and estimating factors.)

FEP Data Input Requirements

Card Type 1

Title card-one only. May be used to enter alpha

numeric title information in columns 2 through 29.

Card Type 2 Data Requirements

Only one Card Type 2 is required that provides input

information independent of fuel types considered (Fig.

Range of

moisture content

(wet basis)

From To

0 0.285

0.286 0.443

0.444 0.545

0.545 0.614

0.615 greater

5). The following types of information are required for

program input with Card Type 2:

Output copies.—The number of printed output copies

desired must be entered in column 1, up to a maximum

of 9 copies. If no entry is made the program will provide

one set of printed output.

Number of alternatives.—The total number of different

types of fuel to be included in analysis must be entered

in columns 4 and 5, up to a total of 10. The number

entered must correspond to the number of Card Type 3

cards prepared and positioned in the data card deck

following Card Type 2.

Stack gas temperature.—A stack gas temperature, in

Fahrenheit degrees, must be entered in columns 9

though II to provide program control and information

required for computation of boiler efficiency and

resulting heat-energy to steam computations. Boiler

efficiency calculations assume 40 percent excess air

and 4 percent heat loss from unburned fuel, radiation

and unaccounted heat losses (1 and 4). The following

equations are used for computation of boiler

efficiencies for wood/bark fuels:

Boiler Efficiency (BE) vs.

Moisture Content (MCW) and

Stack Temperature (ST)

BE = 0.9350 - (MCW * 0.18182) - (ST * 0.000310)

BE = 1.0019 - (MCW * 0.35454) - (ST * 0.000345)

BE = 1.0920 - (MCW * 0.51232) - (ST * 0.000385)

BE = 1.3128 - (MCW * 0.87770) - (ST * 0.000410)

BE = 1.4646 - (MCW * 1.09615) - (ST * 0.000445)

3
Table 1 .—Higher heating value, specific gravity and moisture Table 3.—Range of approximate energy requirements for

content for some softwood and hardwood species drying of some species of wood products1

Timber

Higher heating Green moisture

value1 Specific content2

(Btu/O.D. lb) gravity2

(wet basis)

Softwoods

Douglas-fir:

Old growth

Second growth

Engelmann spruce

Ponderosa pine

Southern pine

Western hemlock

9,200 0.45 0.27

8,800 .45 .27

8,100 .32 .34

9,100 .38 .29

10,380 .47 .24

8,500 .38 .46

Hardwoods

Northern red oak 9,360 .56 .44

Red alder 8,000 .37 .49

Yellow birch 9,340 .55 .43

Yellow poplar 9,630 .40 .43

1

 See Ref. 4.

2

 For heartwood. See Ref. 5.

Table 2.—Average volumes of solid wood/bark

content for some standard units

Units

Cubic feet

of solid

wood/bark content

200 Cubic Foot Units:

Sawdust

Sawdust and shavings

Hogged fuel

Pulp chips

80

57

73

72

1,000 Board Feet of Lumber 60 to 83

1,000 Board Feet of Logs

(Scribner Decimal C Scale):

15-inch diameter and larger

Less than 15-inch diameter

144 to 169

170 to 220

One Cord:

Slabs and edgings

Pulpwood

67 to 75

90 to 110

1

 From conversion factors for Pacific Northwest forest

products, Institute of Forest Products, State of Washington,

303 Anderson Hall, Seattle, Wash., 1957, 28 pages.

For non-wood/bark fuel entered via the first Card Type

3, a boiler efficiency of 0.825 will be assumed for heatto-steam computations unless an override fraction is

entered in lieu of moisture content (see moisture

content data input instructions).

The FEP program may also be used to estimate the

effective evaporative capacities of furnace exhaust

gases used for kiln drying. If a stack gas temperature is

not entered the FEP program will compute an

estimated effective, or theoretical evaporative

Products

Lumber:

Btu’s required per

pound of H2O evaporated

Douglas-fir

Southern pine

Red oak

Plywood:

2,000 - 3,000

1,600 - 2,200

3,000 +

Douglas-fir

Southern pine

Particleboard:

2,000 - 3,000

1,600 - 2,200

Dry wood residues 2,000 - 3,000

Wet wood residues 1,600 - 2,000

Green wood chips 2,000 - 2,500

1

 From G. L. Comstock, Energy requirements for

drying of wood products, In: Wood Residue as an Energy

Source, Proc. No. P-75-13, Forest Products Research

Society, Madison, Wis., 1975.

capacity (pounds of H2O evaporated) of the furnace

exhaust gases for each specified unit of fuel. The

assumption has been used that 1,700 Btu’s (higher

heating value) of furnace exhaust gases is required

for each pound of water evaporated from a dry kiln

operating at about 60-percent efficiency. This assumption can be changed via program card 15.

The effective evaporative capacities for each standard

unit of wood/bark fuels are computed using the

following formulas:

where,

EEC

EEA

EEC = EEA * (HHX - 0.54 * LBPU) (1)

is the effective evaporative capacity of heat

energy per standard unit of fuel type,

is the effective evaporative coefficient of

heat-energy in excess of that required to

evaporate moisture contained in the fuel

(see formula 2).

HHX is the higher heating value per standard

unit of fuel (see formula 3).

0.54 is the approximate weight of chemically

produced water per pound of dry wood/bark

fuel (4), and

LBPU is pounds of dry wood/bark per standard

unit of fuel.

EEA = (1.0/EVRT) - (MCW/(HHV(1.0 - MCW)) (2)

where,

EEA is the effective evaporative coefficient,

EVRT is the effective rate of evaporation

expressed as thousands of BTu’s required

to evaporate each pound of water from a

dry kiln charge,

MCW is the moisture content fraction, wet basis,

of the corresponding fuel.

4
HHV is the higher heating value, in thousands of

Btu’s per dry pound of wood/bark fuel type.

HHX = SG * 62.42 * CFPU * HHV (3)

Some caution should be used when analyzing the

effective evaporative capacities of fuels in kiln drying

processes because of the greater number of climatic,

facilities, wood products, and kiln scheduling variables

that contribute to the required number of Btu’s for

evaporation of water in kiln drying operations. A

practical approach for using the FEP program in

preparing an analysis for a specific kiln is to determine

from historical operating data the average annual

number of Btu’s (higher heating value) required to

evaporate each pound of water removed from the wood

processed. The FEP program assumption of 1,700 Btu’s

(higher heating value) per pound of water evaporated

may be changed via program card 15.

Yearly heat requirement.-The yearly heat requirement,

or pounds of evaporated water requirement must be

where,

HHX is the higher heating value per specified unit of

fuel,

SG is the specific gravity of wood/bark fuel type,

62.42 is the weight of water per cubic foot, in

pounds.

CFPU is the cubic feet of solid wood/bark material per

standard unit of fuel type, and

HHV is the higher heating value per dry pound of fuel

type, in thousands of Btu’s.

* Cubic content of solid material.

** Current source fuel type.

*** Total BTU value per unit for card #1. Card #2 through #10, enter BTU value per oven dry pound.

Figure 5.—FEP data coding record form sample, filled out. (M151-359)

5
entered in columns 14 through 23. If a stack gas

temperature has been entered the program will be

instructed to compute boiler efficiencies and resulting

heat-to-steam values. In electing this option for

computation, a yearly heat requirement must be

entered in millions of Btu’s. If the stack gas

temperature entry is left blank the program will be

instructed to compute the effective evaporative

capacities for each fuel type. If this option is chosen,

the number of pounds of water evaporated annually, as

from a kiln, must be entered in thousands of pounds.

Years considered.—The number of years entered in

columns 26 and 27 indicates the number of years over

which discounted cash flow analyses will be completed

for computation of the capitalized values of the net

benefits that might be realized from use of wood/bark

fuels as alternatives to a specified non-wood/bark fuel

type.

Advalorem costs.—Economic analyses are directed to

estimation of the capitalized value of fuel costs

savings that might be realized from use of alternative

wood/bark fuels via new facilities investment. For this

reason, operating costs that may be associated with

such new investment need to be considered as a

reduction of a gross fuel cost savings. Advalorem

operating costs are typically regular and recurring

costs such as for repair, maintenance, service supplies

local taxes, insurance and such that can be expressed

as a fraction of facilities investment costs. The

appropriate decimal fraction of facilities investment

that may be expected to represent total periodic

advalorem costs must be entered in columns 30

through 35.

Change in other operating costs.—All increases in

annual operating costs associated with a prospective

conversion of an existing furnace system need to be

considered in analysis. Cost increases that cannot be

accounted for as advalorem costs should be estimated

and entered as fixed annual operating costs. These

costs typically cover additional labor requirements,

supervision, utility costs, etc. Fuel preparation costs

that are independent of the unit volume of fuels used

should also be included. However, fuel preparation

costs that vary directly with the unit volume of fuel

should be included in the fuel type cost, designated

“cost per unit,” for Card Type 3 program input. The

estimated annual increase in operating costs described

here should be entered in columns 38 and 43.

Inflation.—The amounts entered for analysis as

advalorem and increased operating costs, and the

annual gross benefit computed as the annual gross

savings in prospective fuel savings will be equal in

each year of discounted cash flow evaluation unless an

inflation rate is entered. Entering an inflation rate

increases annual costs and gross benefits at an annual

compound rate equal to the inflation rate entered. The

program does not consider unequal rates of inflation.

The annual rate of inflation selected for analysis

6

should be entered as a decimal fraction in columns 46

through 51.

Investment tax credit.—In general, an IRS investment

tax credit for 10 percent of processing equipment

investment cost is allowed for tax reductionexcluding land, buildings, and other non-process fixed

asset costs. Investments for cogeneration of electricity

and process heat-energy may qualify for an IRS

investment tax credit of 20 percent. A tax specialist

should be consulted for specific information. The

estimate of investment costs that might be allowed as

an investment tax credit should be entered as a

fraction in columns 54 through 59.

The estimate of investment cost that might be allowed

as an investment tax credit will typically be less than

10 or 20 percent because of the inclusion of land and

building costs in the facilities costs to which the

investment tax credit fraction will computationally

apply. Also, the investment tax credit computed will be

treated as a tax rebate in the first year of discounted

cash flow analysis, whether greater or less than the

computed taxes payable for the first year. Although

this is not a technically correct procedure for all

circumstances, the procedure may be applicable when

the investment tax credit may be fully realized as a

reduction of taxes payable by a corporation.

Discount rate.—The amount entered as a discount rate

should be the rate of return (interest) required for financing of similar investments (alternative rate of

return). The annual rate of interest earnings for financing

requirements will represent a reduction of annual gross

fuel cost savings. The discount rate should be entered

in columns 62 through 67 in decimal fraction form.

Effective tax rate.-Because any reduction of fuel

costs, less additional operating costs, will add directly

to a corporation’s total profits and tax costs, an

effective state and Federal income tax rate needs to be

considered. Annual after-tax benefits (ATNB) are

computed using the following formula:

ATNB = ((Gross benefit - Advalorem Costs -

Increased Operating Costs - Depreciation) x

(1.0 - Effective Tax Rate)) + Depreciation.

(4)

The amount of investment tax credit computed is

added to the first year’s after-tax net benefit. Straight

line depreciation, assuming no salvage, is computed by

the computer program, i.e., Depreciation = Facilities

Cost/Years Considered.

Card Type 3 Data Requirements

Up to 10 different types of fuel may be included for

evaluation, including the “current” non-wood/bark fuel

type (Fig. 5). One card must be prepared for each fuel

type and included in the data card deck following the

one Card Type 2. The data card carrying the one nonwood/bark fuel type information must be the first card
following Card Type 2. Card Type 3 carries the alphanumeric description and associated statistics for each

fuel type to be considered. Appendix A includes

average statistics for a selected number of fuel types.

Fuel type.—The alpha-numeric description identifying

each fuel type must be entered in columns 1 through

18.

Unit basis.—The unit basis, entered as alpha-numeric

input, should correspond with the fuel type’s standard

unit upon which cost and cubic feet of solid wood/bark

material may be most commonly related. Typical entries

will be “BARRELS,” “OD TONS,” “MBF,” and so-forth.

This information must be entered in columns 21 through

26.

Cubic feet per unit.—The cubic feet of solid wood or

bark per standard unit varies considerably and is

needed for computing the amount of heat-energy

available per unit of wood/bark fuel type utilized. No

data entry is required for non-wood/bark fuel as entered

by the 1st Card Type 3 data card. The cubic feet of solid

wood or bark per standard unit must be entered in

columns 29 through 33 for each wood/bark type fuel.

Cost per unit.—The cost, or value, per unit must be

entered in columns 36 through 41. The amount entered

should reflect purchasing and handling costs per unit

for each fuel type as entering the furnace.

If an entry is made in columns 67 through 71 for the

non-wood/bark fuel the program will use this input data

directly as the boiler efficiency fraction for the nonwood/bark fuel as an override of the 0.825 boiler

efficiency otherwise assumed by the program. Entries

in the non-wood/bark fuel card columns 67 through 71

will not affect the effective evaporative capacity

computations for the first fuel type. (See appendix B for

a blank data coding record form.)

Inventory tenure.— Fuel inventories will be required to

cover periods of time during which fuel supplies may

not be resupplied, but furnace demand continues. The

costs of fuels held in inventory, and some portion of

advalorem and other fixed operating costs will normally

be funded by working capital investment. The FEP

program assumes that advalorem and other fixed

operating costs will be funded by working capital for

the same period of time for which fuel inventories must

be funded. Consequently, any difference in the working

capital requirements computed from use of a nonwood/bark fuel and wood/bark fuels will affect the

computed annual net benefit of prospective fuel costs

savings. That is, any change in working capital

requirements will affect annual net benefits in an

amount equal to the change in interest earnings

accrued to working capital by the discount rate used

for analysis.

Inventory tenure requirements should be expressed in

number of weeks in decimal fraction form. For

example, if oil deliveries are expected every two-andone-half weeks “2.5” must be entered in columns 74

through 78.

SUMMARY

The primary objective of the fuel economics computer

program (FEP) is to provide a means for assessing

relative energy and economic values of fossil fuels and

wood/bark fuels, and to provide a means for preengineering assessments of the potential investment

that may be justified by benefits gained through

modification of systems to burn wood/bark fuels. The

FEP computer program may be used to compute either

steam heat recovery or theoretical wood drying

capacities of exhaust gases from different fuels using

readily available fuel and economic information,

standard combustion equations, and discounted cash

flow techniques.

The FEP computer program also computes a variety of

quantitative and economic information including:

volumes of fuel types required to yield specified heat

requirements; prospective savings in fuel costs if wood

and bark fuels are used as alternatives for oil, gas, or

other fuel; capitalized benefits of fuels savings into

working capital requirements and justifiable facilities

investment; and, capitalized values of cost changes

associated with changes in specified moisture contents

of wood and bark fuels.

LITERATURE CITED

1. Corder, S. F. Wood and bark as fuel. School of

Forestry Research Bulletin 14, Oregon State Univ.,

Corvallis, Oreg.; 1973.

2. Ellis, Thomas H. Economic analysis of wood- or bark.

fired systems. Gen. Tech. Rep. FPL 16, Forest

Prod. Lab., Madison, Wis.; 1978.

3. Harpole, George B. A cash flow computer program to

analyze investment opportunities in wood products

manufacturing. USDA For. Serv. Res. Pap. FPL

305, Forest Prod. Lab., Madison, Wis.; 1978.

4. Ince, Peter J. How to estimate recoverable heat

energy in wood or bark fuels. Gen. Tech. Rep. FPL

29, Forest Prod. Lab., Madison, Wis.; 1979.

5. U.S. Forest Products Laboratory. Wood Handbook:

Wood as an Engineering material. U.S. Dept. of

Agric., Agriculture Handbook No. 72 (rev.); 1974.

7
Appendix A: Fuel Economics Program Listing 8
9
10
Appendix B: FEP Data Coding Record

Date

Estimates prepared by

CARD TYPE 1 (Title Card):

* Cubic content of solid material.

** Current source fuel type.

*** Total BTU value per unit for card #1. Card #2 through #10, enter BTU value per oven dry pound.

Figure 6.—FEP data coding record form sample, blank.

(M151-355)

2.0-13-9/82

11
U.S. Forest Products Laboratory

Wood and Bark Fuel Economics Computer Program (FEP), by

George B. Harpole, Peter J. Ince, John L. Tschernitz, and Edward Bilek,

Madison, Wis., FPL 1982.

12 p. (USDA For. Serv. Res. Pap. FPL 415).

This computer program uses readily available fuel and economics information, standard combustion equations, and discounted cash flow analytic

techniques to provide (1) a means to assess relative energy values of wood

and bark for fuel and (2) pre-engineering assessments of the potential investment that may be justified by benefits gained through modifying

wood/bark fuel systems. The authors suggest evaluation by more advanced

engineering and financial methods whenever this program indicates

favorable venture likelihoods. The program listing, written in FORTRAN, is

included, as are coding record forms.
U.S. GOVERNMENT PRINTING OFFICE: 1982-554-030/9