bt analysis de proceso

Bioprocess Design and Economic Analysisfor the Commercial Production ofEnvironmentally Friendly BioinsecticidesFrom Bacillus thuringiensis HD-1 kurstaki

Gerald E. Rowe,* Argyrios Margaritis

Department of Chemical and Biochemical Engineering, Faculty of Engineering,The University of Western Ontario, London, Ontario, Canada N6A 5B9;telephone: (519) 661-2146; fax: (519) 661-3498; e-mail: [email protected]

Received 14 August 2003; accepted 27 October 2003

Published online 5 April 2004 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/bit.20146

Abstract: A production process for B. thuringiensis (Bt)bioinsecticides was designed in detail, including alternativebatch, low-density fed-batch (LDFB), and high-density fed-batch (HDFB) fermentation configurations. Capital andoperating costs, as well as profitability based on simplerate of return, were performed using a purpose-writtenFORTRAN program, explicitly analyzing production of awater-based flowable product used in forestry applications.

The total capital cost was $18 million (Canadian dollars)for a stand-alone plant with base-scale capacity of 3 � l07

billion international units (BIU)/year. Raw material costsamounted to $1.5 million yearly, of which approximatelyhalf was for formulation ingredients. Per-unit productioncost rose sharply for scales of less than 1 � 107 BIU/year,but was little affected by scale above 3 � 107 BIU/year.Product cost was much lower at all scales for a LDFB asopposed to batch fermentation process, but HDFB gaverelatively little additional cost benefit. Profitability analysisperformed by co-varying scale and selling price showed thatbreak-even occurred at a price of $0.45/BIU for a batchprocess at base scale, while with LDFB fermentation thesame production volume sold at $0.35/BIU gave a 12% rateof return. Since the assumed base scale would represent8–15% of current world Bt bioinsecticide production,based on value or volume, itwas concluded that profitabilitywould require some or all of the following elements: tar-geting higher-value markets such as disease vector control,in addition to forestry; a potentially lower plant capacity(although at least 1 � 107 BIU/year); and coproduction ofother large-volume microbial products to absorb capacityand match bioinsecticide output to market demand. B 2004Wiley Periodicals, Inc.

Keywords: bioinsecticides; bioprocess design; bioinsecti-cides production and costs; bacillus thuringiensis; eco-nomic visibility analysis

INTRODUCTION

Bioinsecticides derived from cultivation of Bacillus thu-

ringiensis (Bt) comprise over 90% of all biopesticides sold

on a world scale (Glare and O’Callaghan, 2000). These pro-

ducts provide effective, non-toxic, and environmentally

benign control of a wide range of lepidopteran, coleopteran,

and dipteran insect pests in agricultural, forestry, ornamental,

and disease-vector applications.

Based on a literature review, Glare and O’Callaghan

(2000) gave a 3-page list of commercial Bt products made in

dozens of countries, acknowledging that it was far from

complete. These materials derive from fermentation of

Bt subspecies kurstaki, aizawai, morrisoni (tenebrionis),

israelensis, and others that are formulated into a wide range

of solid and liquid product types. Some 26 Bt products are

registered with the United States Environmental Protection

Agency, and marketed worldwide as part of the US$l00

million annual global market for Bt bioinsecticides (Bishop,

2002). Annual world production of Bt bioinsecticides is

estimated to be approximately 13,000 tons (World Health

Organization, 2003a), with China and other developing

countries accounting for at least half of the total (Bishop,

2002). It is predicted that in the current decade the market

for biopesticides will grow by 10–15%, driven especially

by increased use of Bt for insect control in organic agri-

culture, forestry, and control of mosquito-borne diseases

(Bishop, 2002).

Despite (as well as because of) this commercial im-

portance of Bt bioinsecticides, little has been published on

their mass production and formulation (Couch, 2000). Even

less has been published on the economics of commercial

production, the only significant exception being the brief

generic analysis of product cost and gross profit for an

unspecified formulation type at scales of 20 and 200 tons

per annum done by Lisansky et al. (1993). Given this dearth

of information on industrial production of Bt bioinsecticides,

the significant scale on which they are used to control forest

B 2004 Wiley Periodicals, Inc.

Correspondence to: Argyrios Margaritis

*Present address: Biotechnology Research Institute, National Research

Council of Canada, 6100 Royalmount Avenue, Montreal, Quebec, Canada

H4P 2R2

Contract grant sponsors: The Natural Sciences and Engineering

Research Council of Canada; the EJLB Foundation

Contract grant number: OGP4388

378 BIOTECHNOLOGY AND BIOENGINEERING, VOL. 86, NO. 4, MAY 20, 2004

insect pests in Canada (Van Frankenhuyzen, 2000), and as

a natural outgrowth of our years of research in this area

(Rowe andMargaritis, 1987, 1994, 2003; Rowe et al., 2003),

it was decided to perform a state-of-the-art bioprocess design

study and economic feasibility analysis for commercial

production of Bacillus thuringiensis bioinsecticides.

At the present time, there is worldwide interest in envi-

ronmentally friendly, non-toxic, and biodegradable bio-

insecticides produced by the soil bacterium B. thuringiensis

for use in agricultural crops (corn, soybean, wheat, cotton,

rice, vegetables, fruits, etc.), forestry, floriculture, and

disease vector control. Such interest arises fundamentally

from the serious, global-scale environmental pollution

problems caused by excessive use of chemical insecticides

during the last 50 years. Through this article, we intend to

assist in renewing interest in commercialization of B.

thuringiensis bioinsecticides, especially in developing

countries where native raw materials can be used to produce

effective biorational pest control agents.

MATERIALS AND METHODS

All prices stated are in Canadian dollars ($Cdn), taken as

equivalent to $US 0.73 for purposes of conversion.

General Process Description

Process analysis and economic evaluation of the production

of various formulations of B. thuringiensis bioinsecticides

was performed using a model created in FORTRAN. Both

batch and fed-batch fermentation methods were explicitly

modeled, while recovery and formulation operations for

various product types were kept invariant. A generic

flowsheet showing major unit operations for the process is

given in Figure 1. Although several items of equipment are

not shown, their cost was taken into account in the

economic analysis (see discussion below, and Table I).

With reference to Figure 1, soymeal is milled to

200 mesh in Substrate Hammer Mill C-110, and suspended

with corn steep liquor (CSL) in half the initial medium

volume in Fermentor R-400 before being sterilized with

steam. Corn syrup is diluted in Corn Syrup Mix Tank F-

210, then continuously preheated, sterilized by steam

injection and passage through Sterilization Holding Coil

R-320, and cooled before entering R-400. In fed-batch

configurations only, Medium Feed Tank F-460 is designed

to hold one half the volume of the initial medium in R-400.

Following fermentation, the stabilized broth is cooled to

10jC in Broth Cooler E-530 then adjusted to pH 4 with 5M

sulfuric acid in Broth Tank F-520. It is next concentrated

in disk-stack Centrifuge H-540, operating at a 20% of

its swallowing capacity and 2% solids loss (Villafana-

Rojas et al., 1996), to a paste containing 100 g biomass dry

matter/L. The paste is formulated in Primary Blending Tank

F-600, for production of either a primary powder inter-

mediate or water-based flowable final products (Lisansky

et al., 1993). Stream S-122 going to make primary powder

is dried in Spray Dryer D-620 and comminuted in Hammer

Mill C-621. D-620 was designed to reduce the moisture

content of the feed from 88.5% to 7.0%, assuming 35jCproduct outlet temperature and residence time of 42 s (Mas-

ters, 1991). Primary Powder Storage Bin F-630 is sized to

hold product from five fermentation runs. From there,

primary powder passes through Powder Weigh Hopper

F-632 (not shown), either to Wettable Powder Mixer X-650

for wettable powder production or to Secondary Blending

Tank F-640 for emulsification into an oil-based flowable

product. Fill and Weigh System X-610 is assumed to be

capable of packaging all three product types.

Raw Materials and Sterile Medium Preparation

Receiving and storage of medium ingredients, and medium

preparation and sterilization, comprise Sections 100, 200,

and 300 of the process (Fig. 1, Table I).

Medium composition was essentially that given by

Lisansky et al., (1993), comprising corn syrup as the main

carbon source, hammer-milled defatted soymeal and corn

steep liquor (CSL) as nitrogen sources, and 0.1% v/v

polypropylene glycol 2000 as antifoam. As indicated in

Figure 1, soymeal would be replaced with fishmeal in

B. thuringiensis subsp. israelensis fermentation for disease

vector control products (Lisansky et al., 1993); soymeal

cost was used for economic analysis. The fraction of

substrate dry matter from corn syrup, soy flour, and CSL in

the final medium for both batch and fed-batch config-

urations was assumed to be 0.526, 0.305, and 0.169,

respectively. Substrate concentrations were calculated as

follows: for the batch case, a total substrate dry matter

concentration of 33.1 g/L was assumed, corresponding to

the 18 g/L glucose concentration advocated by Lisansky

et al., (1993); for the two fed-batch cases total substrate dry

matter concentrations of 65.6 and 131.4 g/L were assumed,

in correspondence with the amount of glucose used in the

two most successful fed-batch runs reported by Liu et al.

(1994), designated by them as runs #6 and #7 (see below).

A detailed list of raw material usage and costs for the

base case is given in Table II. Delivered costs for raw

materials in appropriate delivery quantities were estimated,

assuming delivery cost of $30 per ton, using data either

directly from suppliers or the current chemical trade

literature (Chemical Market Reporter, 2003).

A combination of continuous and batch sterilization of

medium ingredients is employed (Lisansky et al., 1993).

Soy flour and CSL, in half the medium volume, are batch

sterilized for 4.5 h in Fermentor, R-400 (cf. Medium Feed

Tank F-460 in fed-batch configurations). After this has

Figure 1. Process flowsheet for production of a range of B. thuringiensis bioinsecticide formulations by batch or fed-batch fermentation.

ROWE AND MARGARITIS: COMMERCIAL PRODUCTION OF ENVIRONMENTALLY FRIENDLY BIOINSECTICIDES 379

Table I. Equipment list, capital cost (in thousands $Cdn), and power usage for base case production scenario (LDFB process; 3 � 107 BIU/year).

Description No. Capacity Installed cost $000

Section 100: Soymeal receiving, storage, and milling

F-100: Soymeal storage bin 1 30 cu m 12.3

X-101: Truck dump scale 1 91 tons 89.6

J-102: Receiving elevator 1 12 m 23.3

J-103: Auger 1 2.6 m 6.0

C-110: Substrate hammer mill 4 55 kW 32.2

J-111: Milling elevator 1 10 m 21.8

F-112: Surge hopper 1 3.5 cu m 6.2

H-115: Bag filter 1 2.0 cu m/s 83.0

F-116: Weigh hopper 1 33 cu m 25.3

Subtotal 299.7

Section 200: Liquid substrate storage and preparation

F-202: Corn steep storage tank 1 20 cu m 23.7

L-203: Corn steep pump 1 0.7 cu m/h; 0.4 kW 22.2

F-210: Corn syrup mix tank 2 105 cu m 90.5

M-211: Corn syrup mixer 1 8.4 kW 31.4

F-212: Corn syrup storage tank 1 61 cu m 42.0

L-213: Corn syrup pump 1 2.0 cu m/h; 1.1 kW 32.2

L-243: Medium sterilization pump 1 42 cu m/h; 16.5 kW 105.0

Subtotal 347.0

Section 300: Medium sterilization

E-300: Medium pre-heater 3 382 sq m 1,008.8

M-310: Steam injector 1 0.18 m ID 11.5

H-311: Steam carbon filter 4 4.6 sq m 50.1

H-312: Steam particulate filter 4 4.6 sq m 50.1

R-320: Sterilizer holding coil 1 0.31 m ID; 30 m 103.0

H-330: Flash cooler 1 0.88 mID; 1.6 m H 69.6

H-331: Entrainment separator 4 4.0 sq m 50.7

L-332: Hot medium pump 1 42 cu m/h; 16.7 kW 116.1

E-340: Medium cooler 1 33.4 sq m 160.3

Subtotal 1,620.2

Section 400: Fermentation

R-400: Fermentor 1 281 cu m; 322.6 kW 2,565.6

L-402: Broth pump 2 441 cu m/hr; 15.3 kW 127.8

R-410: Inoculum fermentor 1 14 cu m 380.8

F-420: Alkali storage tank 1 10 cu m 16.5

L-421: Alkali pump 1 3.1 cu m/h; 0.6 kW 27.9

F-460: Medium feed tank 1 94 cu m 65.1

M-461: Conc’d. medium mixer 3 19.4 kW 82.7

L-462: Conc’d. medium pump 2 7.5 cu m/h; 4.2 kW 90.1

Subtotal 3,356.5

Section 500: Product recovery

F-510: Sulfuric acid tank 1 61 cu m 67.4

L-511: Acid pump 2 5.0 cu m/h; 0.60 kW 26.5

F-520: Broth tank 3 95 cu m 1,267.4

M-521: Broth tank mixer 1 9.5 kW 65.3

E-530: Broth cooler 2 356 sq m 736.9

L-531: Broth pump 1 84 cu m/h; 5.9 kW 852.4

H-540: Centrifuge 3 420 cu m/h 2,322.9

L-541: Centrifuge feed pump 1 84 cu m/h; 5.9 kW 71.3

Subtotal 5,410.1

Section 600: Formulation and packaging

F-600: Primary blending tank 1 74 cu m 46.5

L-601: Primary blending pump 3 30 cu m/h; 5.9 kW 120.0

X-610: Fill-and-weigh system 1 200 L/min 172.3

D-620: Spray dryer 1 20 cu m 1,180.8

C-621: Powder hammer mill 1 54.7 Kw 15.8

F-630: Powder storage bin 1 41 cu m 14.5

J-631: Primary powder auger 1 3.0 m 6.0

F-632: Powder weigh hopper 1 7.0 cu m 18.1

F-640: Secondary blending tank 1 19 cu m 22.9

M-641: Emulsifier 2 12.4 kW 122.1

L-642: Blending tank pump 1 2.4 cu m/hr; 0.5 kW 23.8

(continued )


been cooled to 50jC, diluted corn syrup is sterilized in

high-temperature, short residence-time Sterilization Hold-

ing Coil R-320. In this operation the solution is heated to

90jC in Medium Pre-heater E-300 which also serves to

cool the sterilized liquid to 39jC. The preheat temperature

of 90 jC was chosen based on an approximate optimization

of heat exchanger vs. steam cost. Injection of clean, filtered

steam at 16 barg in Steam Injector E-320 heats the syrup to

140jC. After 3.0 min in R-320 the syrup is cooled to 98jCin Flash Cooler H-330, then cooled to 30jC by sequential

passage through E-300 and Medium Cooler E-340.

Fermentation Process Configurations

Fermentation operations per se comprise Section 400 of

the process (Fig. 1, Table I). Broth and product potency is

expressed in billions (109) of international units per unit

volume or mass viz. BIU/L or BIU/kg.

The fermentor, operating cycle of 66 h was assumed to

be similar to that of Lisansky et al. (1993), specifically

as follows: sterilization and checks: 1.0 h; medium load-

ing, sterilization, and cooling: 11.0 h; inoculation: 0.5 h;

fermentation: 38.0 h; product stabilization: 4.0 h; broth

discharge: 2.5 h. Inoculum volume was assumed to be l0%

of initial medium volume. Sparging with compressed air

was costed at a flow rate of 0.2 vvm, and mixer power

(electrical) assumed to be 2.1 W/L based on industry

practice at large scale. In fed-batch configurations the total

feed volume was assumed to be half the initial medium

volume. Culture conditions at harvest are typified by 90%

free spores and y- endotoxin crystals, with less than 10%

vegetative cells (Lisansky et al., 1993).

Fermentation biomass concentration and toxicity were

based on experimental data from Liu et al. (1994), which is

shown along with viable spore concentrations in Figure 2.

The biomass and spore concentration results of Arcas et al.

(1987) are also shown since these workers obtained the

highest reported Bt biomass concentration of 56.4 g/L, using

fed-batch fermentation. As the figure shows, the latter group

achieved biomass concentrations as high as 32.5 g/L in batch

fermentations, but with relatively low spore counts. The fed-

batch results of Liu et al. (1994) demonstrated that much

Table II. Raw material use and cost for base case production scenario (LDFB process; 3 � 107 BIU/year).

Raw materiala Use, ton/year Cost, $/ton Annual cost $000

Fermentation

Soymeal 560 320 178.0

Corn syrup 1,040 425 441.7

Corn steep liquor 560 100 56.1

Poly(propylene glycol) 30 190 5.8

Caustic soda, 50% 52 280 14.6

Subtotal 696.2

Product recovery

Sulfuric acid 300 85 25.8

Subtotal 25.8

Formulation

Poly(acrylic acid, Na salt), aqueous 180 1,580 285.4

Smectite clay 27 6,900 187.0

Xanthan gum 3.6 16,000 57.8

Non-ionic surfactants 30 3,500 105.4

Potassium sorbate 12 13,000 156.6

Subtotal 792.2

Total raw materials (thousands of $Cdn): $1,516.0

aExample vendors: soymeal: ADM Agri-Industries, Windsor, ON; corn syrup, corn steep liquor: Casco, London, ON; poly(propylene glycol), caustic

soda: Alphachem, Mississauga, ON; poly(acrylic acid): Polycryl, Stamford, CT; smectite clay: Elementis Specialties, Hightstown, NJ; xanthan gum:

NutraSweet Kelco, Chicago, IL; non-ionic surfactants, potassium sorbate: Ashland Canada, Mississauga, ON.

Description No. Capacity Installed cost $000

F-650: Oil storage tank 2 84 cu m 99.7

L-651: Formulation oil pump 1 4.2 cu m/h; 0.8 kW 28.6

Subtotal 1,871.1

Contingency and fee = $2,182.3

Capital cost of utilities, buildings, and site preparation = $3,637.1

Total capital cost: $17,943.2 Total continuous power: 1,060 kW

Table I. (continued )


higher spore concentrations are achievable for a given bio-

mass concentration. They also showed that nutrient feeding

could increase whole broth toxicity proportionally with

spore count at biomass concentrations up to 36.4g/L; at

a biomass concentration of 53.7g/L, however, broth toxi-

city was no higher and viable spore count fell precipitously.

These results also imply that the high-biomass fed-batch

results of Arcas et al. (1987) may have been suboptimal

in terms of broth toxicity. Based on these results the two

fermentations of Liu et al. (1994) giving the highest spore

concentrations (runs #6 and #7) were assumed to

be representative of results potentially achievable via fed-

batch fermentation.

For the batch fermentation case, it was assumed that

results using the equivalent of 18 g/L of glucose would be

directly proportional to those found by Liu et al. at 8 g/L

glucose, i.e., biomass concentration was assumed to be

13.3 g/L [(18/8) � 5.9 g/L], and broth toxicity to be

0.61 BIU/L [(18/8) � 2.72 � 108 IU/L]. The data of runs

#6 and #7 of these authors for the two fed-batch cases

exhibited biomass concentrations of 23.8 and 36.4 g/L, and

toxicities of 1.21 and 1.73 BIU/L respectively. These three

fermentation process configurations are designated hence-

forth as batch, low-density fed-batch (LDFB), and high-

density fed-batch (HDFB) processes, respectively.

Recovery and Formulation

Product recovery, formulation and packaging comprise

Sections 500 and 600 of the process (Fig. 1, Table I).

The plant was assumed to be capable of producing a range

of formulated final products for application in forestry,

agriculture, and disease vector control. It was designed to

produce three B. thuringiensis subsp. kurstaki formulations

for forestry and agricultural applications, namely: a water-

based flowable with activity of 12.4 BIU/L [i.e., the high-

potency ‘‘48B‘‘ product described by Lisansky et al.

(1993) for forestry applications], an oil-based flowable

with activity of 16.9 BIU/L, and a wettable powder with

activity of 16.0 BIU/kg. It was also designed to produce a

B. thuringiensis subsp. israelensis water-based flowable

formulation with activity equivalent to 8.45 BIU/L, used

for control of dipteran disease vectors. Detailed formulation

compositions were taken from Lisansky et al. (1993),

with the exception of the SurfynolR surfactants which were

judged to be prohibitively expensive at estimated bulk

delivered prices in the range of $16,000 to $18,000 per ton.

For economic analysis purposes it was assumed that a

combination of sorbitan monostearate and poly(oxyeth-

ylene) monostearate costing $7,000 per ton would give

satisfactory wetting performance. The formulation ingre-

dients used are shown in the list of raw material usage and

costs for the base case given in Table II.

Economic Analysis Calculation Methods

Economic analysis was performed in Canadian dollars for a

stand-alone plant located in southern Ontario, Canada, using

methods given in Ulrich (1984) unless noted. The plant was

assumed to operate 24 h/day, 330 days per year, resulting in

120 batches per annum with fermentation cycle time of 66 h.

The base case was taken to employ low-density fed-batch

fermentation yielding 1.21BIU/L, at a production scale of 3 x

107 BIU per annum, with all of the product formulated as a

water-based flowable for forestry applications and sold at an

average price of $0.35 per BIU. This price was chosen based

on reliable information that the current price of this type of

product to a large volume user is about $0.30 per BIU, and

$0.45 per BIU for small-volume purchases (Van Frank-

enhuyzen, 2003). Although a bioinsecticide plant would be

expected to produce all types of formulation for which a

market of at least a minimum volume exists, it was decided

to base the manufacturing cost and profitability analyses on

production of a water-based flowable only, due to a lack

of reliable price information for large-volume purchases of

other formulation types. The issue of production scale is

discussed below.

A FORTRAN program was written to calculate required

equipment size, number of identical units and installed cost,

total capital investment, operating costs, revenue, and over-

all profitability. The calculation procedures used are des-

cribed below, and an outline of the algorithms is given in the

Appendix. Program code was debugged, compiled and run

using WATFOR-77R Version 4.0 PC/DOS software

(WATCOM Systems Inc., Waterloo, Ontario).

Equipment costs were in general derived from Ulrich

(1984), and in some cases Peters and Timmerhaus (1980),

using a Chemical Engineering Plant Cost Index of 400.9.

Both sources give log–log graphs of purchase cost vs. unit

size from which the equations of linear segments of the

appropriate plots were estimated, generally over several size

Figure 2. Viable spore concentration results from [10] (5,n) and (o,.),and broth toxicity results from [10] (D,E). Open and closed symbols

represent batch and fed-batch fermentation results, respectively.


ranges, and coded to allow calculation of purchase cost as a

function of unit size. Installed cost for each piece of process

equipment (cf. Table I) was obtained by multiplying pur-

chase cost by an installation cost factor which varies with the

type of unit, construction material, etc. The installation cost

factor accounts for transportation of the equipment to the

site, direct materials (e.g., piping, valves, structural supports,

etc.) and labor, indirect expenses, contingency and fee

allowances, and capital for auxiliary facilities (e.g., steam

generation, etc.; Ulrich, 1984). All equipment in contact

with aqueous process liquids was costed on the basis of

316 stainless steel.

Two subroutines were used to perform these calculations

as the main program went through the equipment list,

namely: subroutine RANGE checked that the required size

was not greater than the maximum for the particular type of

equipment, and if it was, specified the number and size of

identical units; subroutine COST calculated the installed

bare module cost for the required size and number of units,

and accumulated these costs and electrical power require-

ments (continuous basis). The cumulative figure resulting

from this procedure was the total base bare module capital

required for the plant. To this value was added 18% for

contingency indirect costs for design and engineering,

construction expenses per se, contractual’s fee and con-

tingency (Peters and Timmerhaus, 1980). A further 30% of

total base bare module cost was added for the capital cost

of utilities, buildings and site preparation, to give an

estimate of total installed equipment cost. This type of

preliminary capital cost estimate, based on a detailed pro-

cess flow sheet and approximate material and energy

balances, is expected to be accurate to within 20% (Peters

and Timmerhaus, 1980; Ulrich, 1984). Total installed equip-

ment cost was multiplied by 1.09 to allow for start-up

costs, giving total fixed capital. Finally, working capital

(for raw materials and supplies, finished and semifinished

product, etc.) was added at 15% of total installed equipment

cost to give total capital investment.

Manufacturing cost and profitability calculations were

performed as described briefly below (cf. Table III,

Appendix). Raw materials usage and costs were summed;

packaging costs were assumed to be zero, i.e., product

supplied in bulk tanker or returnable bulk drums F.O.B.

plant. Operating labor consisted of four operators on each of

four shifts, each costed at $40,000 per annum; annual

administrative labor cost was assumed to be $120,000.

Individual costs were then calculated for steam generation

(natural gas assumed as energy source at a cost of $0.267 per

standard m3), electricity ($0.043 per kWh), cooling and

process water, demineralized water (for steam), refrigerated

water, and compressed air. Detailed trial calculations

showed costs for waste clarified broth disposal to be neg-

ligible. Total annual costs and profitability were calculated

as described in detail in the Appendix, assuming straight-line

capital depreciation over 15 years, zero initial research and

development costs, no tax concessions, and the current

Canadian federal tax rate of 21%.

RESULTS AND DISCUSSION

Installed Equipment and Total Capital Cost

Table I presents a listing of plant equipment, and total capi-

tal cost and power requirements, for base case production at

a scale of 3 � 107 BIU/year. For a stand-alone plant, total

capital cost was estimated to be almost $18million, of which

approximately $12 million is the total installed equipment

cost. The distribution of installed equipment cost. The

distribution of installed equipment cost among process

Sections 100 to 600 (see Table I) was found to be 2, 3,13, 26,

42, and 14%, respectively.Major items of equipment include

a fermentor of nearly 300 m3 volume, three large disk-stack

centrifuges, three broth-holding tanks, a spray dryer (not

required if all production were in fact water-based flowable),

and the medium preheater, accounting collectively for

approximately 69% of total installed equipment cost.

Production Cost Analysis

Usage and costs for raw materials for the base case are

shown in Table II. Raw material costs are estimated to total

approximately $1.5 million per annum of which the prin-

cipal carbon source, corn syrup, is the largest single cost

item (29% of the total). Nevertheless, even for a water-

based flowable product formulated using a low-priced sur-

factant, formulation ingredients comprise 52% of total raw

material costs.

Figure 3 shows unit production cost vs. annual production

rate for each of the three fermentation process configurations

considered, as well as a line corresponding to the assumed

selling price of $0.35 per BIU. It is seen that production cost

Table III. Manufacturing cost analysis for base case production scenario

(LDFB process; 3 � 107 BIU/year).

Expense item $000/year $/BIU

Raw materials 1,516 .051

Operating labor 640 .021

Administrative labor 120 .004

Utilities:

Steam: 16 barg @ $0.021 /kg

5 barg @ $0.016 /kg 881 .029

Electricity @ $.043 /kWh 398 .013

Process water @ $0.153 /cu m 592 .020

Demineraized water @ $.919 /cu m 101 .003

Cooling water @ $.007 /MJ 356 .012

Compressed air @ $.018 /std cu m 212 .007

Maintenance and repairs 978 .033

Operating supplies 147 .005

Laboratory charges 96 .003

Overhead and storage 521 .017

Local taxes and insurance 430 .014

Depreciation (15-year plant write-off) 1,304 .043

Administration 130 .004

Distribution and market development 349 .012

Total expense: $8,770 0.292


falls sharply, regardless of fermentation configuration, as,

production scale is increased in the range 5 � 106 BIU/year

to 1 � 107 BIU/year. Conversely for scales above about 3 �107 BIU/year, production cost does not decrease much as the

scale of operations is increased. It is also seen that increasing

fermentation broth potency from 0.61 BIU/L to 1.21 BIU/L

(i.e., going from batch-to low-density fed-batch operation)

has a strong effect in lowering unit production cost, while a

further increase to 1.73 BIU/L (i.e., HDFB operation) has

only a marginal effect on cost. For the two fed-batch cases

analyzed, production scale at the break-even point for

the assumed average selling price of $0.35/BIU occurs at

approximately 2 � 107 BIU per annum. Conversely, the

break-even point for the batch fermentation case, occurs at a

production scale of 6 � 107 BIU/year. This plot also shows

that for the fed-batch cases the actual selling price will have a

relatively strong effect on the scale at which the break-even

point is reached.

These results can be compared with total product cost

estimated by Lisansky et al. (1993), who found that 3.2 �106 BIU/year could be produced for $0.436/BIU [assuming

the ‘‘industry standard’’ (Lisansky et al., 1993) 16 BIU/kg

product and the usual currency conversion]. From Figure 3 it

is evident that, even if a HDFB fermentation process were

used, our estimate of total production cost is approximately

double their estimate for the same scale of operation. The

major difference between the two analyses appears to be

the magnitude of capital-dependent operating costs. Thus

Lisansky et al. (1993) project the same $/BIU capital-

dependent operating costs at a scale of 3.2� 106 BIU/year as

we estimate at a scale of 3 � 107 BIU/year. A judgment on

this discrepancy can be made by calculating the quantitative

variation of these costs with production scale found by the

two analyses, and comparing these to values reported in the

economic analysis literature. Accepted wisdom in this

regard is commonly known as the six-tenths-factor rule,

viz. ‘‘a log-log plot of capacity versus equipment cost for a

given type of equipment should be a straight line with a slope

equal to 0.6’’ (Peters and Timmerhaus, 1980). The capital-

dependent operating cost data for the two scales presented by

Lisansky et al., i.e., 3.2� 105 and 3.2� 106 BIU/year, give a

slope of 0.28 for log($/year) vs. log(BIU/year). For the

LDFB configuration of the present analysis with scale in the

range 0.5–6 � 107 BIU/year the slope for log($/year) vs.

log(BIU/year is 0.53 (r2 = 0.995), i.e., much closer to the

accepted value. It appears warranted to conclude that the

present capital cost estimates are considerably more realistic

than those of Lisansky et al. (1993), and hence to infer that

our production cost estimate is likely to be more realistic

than theirs.

The output from a detailed manufacturing cost analysis for

the base case is shown in Table III. Utilities as a group com-

prise the largest cost component, followed in decreasing

order by raw materials, depreciation, and maintenance and

repairs. Table IV shows operating costs by category as a

function of fermentation configuration at production scales

of 1 � 107 and 3 � 107 BIU/year. At both scales the fed-

batch processes gave significantly lower capital and utility

costs than the batch fermentation process, as well as some-

what lower administration and overhead costs, due to their

greater volumetric productivities. The lowest overall opera-

ting costs regardless of scale occurred for the high-density

fed-batch (HDFB) process, although raw material cost was

higher here than at somewhat lower productivity (LDFB).

As observed in both Figure 3 and Table IV, produc-

tion scale had a large effect on total per-unit operating

cost ($/BIU), which at 3 � 107 BIU/year was only 60–64%

of that at 1 � 107 BIU/year. Amounts in all cost categories

except for rawmaterials were substantially reduced at higher

scale, with the category showing the largest reduction

depending on the fermentation process configuration. Thus,

for batch fermentation by far the largest reduction was for

capital-dependent items, followed by labor-dependent items,

administration and overhead, and utilities. In the fed-batch

cases, the order for capital and labor dependent items

was reversed, reflecting the much lower capital cost of the

Table IV. Annual operating costs by category versus fermentation

configuration at two production scales (A: 1 � 107 BIU/yr; B: 3 �107 BIU/yr); all values in $/BIU.

Batch LDFB HDFB

Production scale A B A B A B

Direct fixed capital dependent items .203 .122 .139 .081 .122 .077

Labor dependent items .086 .028 .086 .028 .086 .028

Administration and overhead .120 .066 .094 .047 .087 .046

Raw materials .054 .054 .051 .051 .061 .061

Utilities .188 .144 .121 .083 .097 .064

Total .652 .415 .490 .292 .453 .279

Figure 3. Total per-unit production cost vs. production scale for batch

(solid line), low-density fed-batch (LDFB; dashed line), and high-density

fed-batch (HDFB; dotted line) fermentation processes.


latter type of process. For the LDFB fermentation process,

Figure 4 shows the effect of production scale on the per-

centage of total production cost for each of the cost cate-

gories in Table IV. It is seen, as expected, that as scale

increases raw material costs assume greater importance

while labor costs decrease as a percentage of total costs. It is

also seen that the cost of utilities becomes increasingly more

important as scale increases. Comparison of these results

with those given in Lisansky et al. (1993) for production of

3.2 � 106 BIU/year indicates agreement (at the same scale)

on utilities’ costs, but a much lower estimate in our case for

raw materials (about 7% vs. 21%) and a somewhat higher

estimate for capital costs, includingmaintenance (about 28%

vs. 23%). Although Lisansky et al. estimated utility costs at

$0.089/BIU vs. our value of $0.159/BIU, this factor accounts

for a similar percentage of total cost due to their low estimate

of the latter (see above). Their higher raw materials cost,

$0.090/BIU vs. our value of $0.05l/BIU, is no doubt due to

the higher priced formulation ingredients, especially surfac-

tants, which they specified (see the Materials and Methods

section). Finally, as discussed above, their $0.099/BIU ca-

pital cost estimate is unrealistically low compared to our

value of $0.213/BIU.

The present results can also be compared on a more

general basis with economic analyses of fermentation

processes found in the literature. One such analysis of a

comparable process at similar scale is that of Chong

and Lee (1997) for production of the biodegradable plas-

tic feedstock, poly(3-hydroxybutyrate). Their Alcaligenes

eutrophus process with product recovery by surfactant-

hypochlorite digestion at a scale of 24,800 m3 annual fer-

mentation broth volume was estimated to cost $US 640/m3

(about $880 in Canadian dollars). Our cost estimate to pro-

cess the same annual broth volume using LDFB fermen-

tation (3 � 107 BIU/year scale) is $3.54/m3. Given that the

former process requires much more elaborate operations

downstream of fermentation (i.e., three centrifugation stages

as well as spray drying), and that waste treatment/disposal

comprises 10% of their total costs, the production costs per

unit broth volume appear quite comparable.

Profitability Analysis

Profitability in terms of simple rate of return on total capital

invested was estimated for the three fermentation process

configurations by co-varying production scale and sale

price for a water-based flowable product. These parameters

were varied over the range 5 � 106 to 6 � 107 BIU/year,

and $0.18 to $0.50 per BIU respectively. For the batch

process, an average selling price of $0.45/BIU would be

required just to cover depreciation at the base scale of 3 �107 BIU/year. However the results for the fed-batch con-

figurations were much more promising.

The positive rate-of-return results obtained are plotted

for the LDFB process in Figure 5, and the HDFB process in

Figure 6. These plots show that at higher sale prices and

relatively low production scale the potency of fed-batch

fermentation broth (i.e., BIU/L) has only a slight effect on

profitability, while the effect becomes more substantial

as either price decreases or scale increases, or both. For

example, for LDFB the rate of return was 9.4% for 2 �107 BIU/year sold at $0.40/BIU and 9.5% for 4 �107 BIU/year sold at $0.30/BIU (Fig. 5), but 13.5 and

14.8% for the same combinations for HDFB (Fig. 6).

However, for 4 � 107 BIU/year sold at the assumed base

price of $0.35/BIU, the returns for LDFB and HDFB were

Figure 5. Rate of return on capital invested in a low-density fed-batch

(LDFB) fermentation process vs. product selling price and annual

production scale.

Figure 4. Percentage of total production cost due to various cost catego-

ries vs. production scale for a low-density fed-batch (LDFB) fermentation

process; (o) capital, (5) labor, (D) administration and overhead, (inverted

triangle) raw materials, (diamond) utilities.


15.3 and 22.1%, respectively. For the base case scale of 3 �107 BIU/year and sale price of $0.35/BIU, the profitability

of the LDFB and HDFB processes differs relatively little,

being 12.0 and 13.9%, respectively. Under the same

assumptions the rate of return for the batch fermentation

process is nil, viz. 0.1%. Thus, under the best-estimate sale

price and moderate production scale assumptions there

appears to be much to be gained by employing a low-

density fed-batch (LDFB) as opposed to a batch fermenta-

tion process. Conversely, there is little economic incentive

to push broth potencies and biomass concentrations to

values attainable by HDFB operation. Given the feed

control and aeration problems encountered by Liu et al.

(1994) at high biomass concentrations (cf. Fig. 2), process

robustness concerns further reinforce this conclusion.

Obviously it is necessary to have a realistic estimate of

howmuch of the various products could actually be sold (as a

function of price) to assess the prospects for commercially

viable production of Bt bioinsecticides. The Canadian Bt

market is overwhelming for control of forest insect pests:

during the 5-year period 1998–2002, annual Bt usage ranged

from approximately 6 to 12.5 � 106 BIU on an area of

208,000 to 353,000 ha, with average usage of some 8 �106 year (Van Frankenhuyzen, 2003). During the past few

years operational use of Bt in Canadian forestry has

decreased considerably because the spruce budworm out-

break that accounted for most spraying since the mid-1980s

has collapsed throughout eastern North America. However,

from 1985 to 2000 an average of approximately 1� 107 BIU

were applied annually, and during the worst years of the

spruce budworm infestation, from 1985–1991, yearly usage

was 1.4� 107 BIU (van Frankenhuyzen, 2003). Assuming a

return to these historic usage rates in the future, Canadian

forestry demand could amount to almost half of the 3 �107 BIU/year taken as base case output above.

From the perspective of total world Bt bioinsecticide

production of about 13,000 tons (World Health Organ-

ization, 2003a), assuming the industry-standard potency of

16 BIU/kg, base scale output would be 15% of present

global production. Given that about half of world Bt pro-

duction occurs in developing countries such as China

(Bishop, 2002), precisely to avoid having to import rela-

tively expensive inputs such as pesticides from the indus-

trialized countries, it seems more relevant to consider that

base case output would amount to some 30% of the current

market in the latter countries. It would appear unrealistic to

expect that such a large increase in output could be

profitably absorbed, whether or not anticipated modest

growth in market size materializes (see below).

In terms of value, global sales of Bt bioinsecticides are

estimated at US$ 100 million (Bishop, 2002), or in

Canadian dollars approximately $137 million. For the base

case scenario of 3 � 107 BIU sold at an average price of

$0.35/BIU, total revenue would be $10.5 million, which is

approximately 7.7% of the present value of world sales.

Given that this market is expected to expand at a rate of

1.0–1.5% per annum in the foreseeable future (Bishop,

2002), market growth could absorb these increased sales

within a period of 5–8 years, assuming that no additional

competing products were brought to market during that

time. Although this simple calculation ignores questions of

which market sectors will actually grow at such a rate, in

terms of geographic location and product type (target

insects and formulations), it does indicate that sufficient

global market demand could exist not long after the time

that a new plant was actually in production.

Although no figures are publicly available, one Bt

market sector that has been growing in recent years is that

of mosquito control to prevent the spread of diseases such

as West Nile virus, dengue fever, and malaria (Anonymous,

2003); one authority estimates it to comprise at least 20%

of global Bt use (Van Frankenhuyzen, 2003). It is also

appears to be a sector in which prices are higher than, for

example, the forestry market. One apparently large-volume

purchase of AquabacR B. thuringienis subsp. israelensis

granules, having a potency equivalent to 0.2 BIU/kg, was

priced at $US64.00 per 40 lb bag (Commonwealth of

Massachusetts, 2003). This price, about $24/BIU in

Canadian funds, is 80 times that of the $0.30/BIU price

which prevails in the bulk forestry market, and is probably

representative of prices in other ‘‘specialty’’ market sectors

such as horticulture, etc. However, it is likely that a

substantial fraction of Bt disease vector control products

have historically been sold in very large-volume purchases

at correspondingly lower prices to the World Health

Organization for its 1974–2002 Onchocerciasis Control

Programme (World Health Organization, 2003b). In sum-

mary, it is not possible to make a quantitative price esti-

mate for Bt products in the disease vector control market,

although it is certainly higher than that of the forestry

Figure 6. Rate of return on capital invested in a high-density fed-batch

(HDFB) fermentation process vs. product selling price and annual

production scale.


market (Van Frankenhuyzen, 2003). Thus, in conclusion,

no more realistic profitability estimates than those pre-

sented in Figures 5 and 6 are possible without a thorough

study of the entire range of Bt market sectors, which is well

beyond the scope of the present work.

It is possible, however, to conclude from the above

that profitable production of Bt bioinsecticides in Canada

will require a strategy involving some or all of targeting

higher-price markets, reducing production scale below the

assumed base case, or coproduction of other microbial

products in a shared facility. The figures cited above for

world Bt market value and production quantity can be

evaluated to give an average selling price of almost $0.70/

BIU, implying that much of this output is sold in con-

siderably higher value markets than that of Canadian

forestry (viz. bulk price of $0.30/BIU). From Figure 3 it is

evident that, if this average world price were attainable, by

selling a substantial fraction of the output into higher value

agricultural, ornamental, and disease-vector markets, Bt

production at a scale of somewhat less than 1 � 107 BIU/

year could be quite profitable, provided that at least a low-

density fed-batch fermentation process were employed.

Another, possibly complementary, alternative would be to

build a plant with a capacity of at least 1–2 � 107 BIU/year

to maintain economies of scale, but to produce other

microbial products as well. One such co-product might be

Rhizobium or Azospirillium inoculants that appear to

have substantial potential for increasing the efficiency of

utilization of fertilizers and the yields of both leguminous

and nonleguminous crops (Okon and Labandera-Gonzalez,

1994; Rao, 2003; Thomas et al., 1995). Another alternative

could be the biodegradable plastic, poly(3-hydroxybuty-

rate), which appears to have a scale similar to B. thu-

ringiensis bioinsecticides for economical production (Chong

and Lee, 1997).

CONCLUDING REMARKS

With reasonable care it should be possible to generalize the

present results to any fermentation-based process in which

the amount of product formed is proportional to biomass

concentration. For the three configurations analyzed above,

this quantitative relationship is (g biomass dry matter per

liter) = (20–22) � (BIU/L). For the LDFB configuration

producing 24,800 m3 of fermentation broth annually,

production cost was estimated at about $350/m3, compared

to $880/m3 for a biopolymer production process comprising

several more downstream processing operations. This

difference underlines the relative importance of post-

fermentation processing costs, especially primary recovery

operations, which accounted for 42% of our total operating

costs (cf. their waste disposal costs). The breakdown of our

base case operating costs in terms of major process

operations was calculated to be approximately as follows:

medium preparation, 20%; fermentation, 25%; primary

recovery, 40%; finishing, 15%. The detailed process design

and results presented herein, especially if critically

compared to the economic analysis of biopolymer produc-

tion by Chong and Lee (1997), should make it possible to

quickly perform an estimate of about F 30% accuracy of

the production cost of an arbitrary, semi-purified, biomass-

associated, submerged fermentation product.

The capital cost estimation approach implemented in the

present study, based on a detailed technical analysis and

design of the Bt bioinsecticide production process, appears

to be capable of generating capital cost estimates of suf-

ficient accuracy (i.e., F20%) for preliminary budget

approval purposes (Peters and Timmerhaus, 1980). The

methodology developed to obtain such estimates for var-

ious operating configurations and production scales con-

sists of a purpose-written computer program employing

piecewise log–log correlations of purchase cost vs. unit

size, combined with unit-specific installation cost factors

(Ulrich, 1984). The program also calculates requirements

for raw materials and utilities via static simulation of each

particular process. This approach, especially if the detailed

process can be faithfully modeled using a commercially

available process design software package, is a cost-

effective way of obtaining capital and operating cost

estimates for preliminary budget approval purposes. Of

course, the reliability of the results is crucially dependent

on the accuracy of the major assumptions, such as the

volumetric productivity of fermentation. To proceed with

any measure of confidence to estimate the profitability of a

facility it is necessary to have a reliable estimate of average

selling price, which for Bt bioinsecticides means price as a

function of the quantities sold in typical transactions, for

each of the various product market sectors.

APPENDIX

Outline of Economic Analysis Algorithm

Input process and economic parameters annual production,

BIU/year, fermentation configuration (batch or fed-batch);

broth potency, BIU/L; total medium substrate concentra-

tion, g dry matter/L; broth biomass concentration at har-

vest, g dry matter/L; selling price of each final product, $/L

or $/kg.

Calculate required fermentor broth volume per batch:

based on annual production, number of batches per year

(120), broth potency and product loss during recovery (2%).

Go through the equipment list sequentially for the

specified process configuration, performing the following

for each unit:

� Calculate size and required electrical power (continuous

basis)� Via subroutine RANGE, check that size does not exceed

maximum for type of unit; if it does, calculate the num-

ber and size of identical units� Via subroutine COST, calculate installed bare module

cost, and accumulate these costs and electrical power

requirements.


Multiply the total base bare module cost by 1.48 to

account for contingencies, fees, and the capital cost of

utilities, buildings and site preparation, to give an estimate

of total installed equipment cost.

Add 9% to total installed equipment cost for start-up

costs, giving total fixed capital investment.

Add 15% of total installed equipment cost for working

capital, giving total capital investment.

Calculate and sum raw material costs.

Calculate operating and administrative labor costs.

Calculate costs for each of low-and high-pressure steam,

electricity, water (cooling and process, demineralized refri-

gerated), and compressed air.

Calculate total direct costs by summing the costs for raw

materials, labor, utilities, maintenance and repairs (5% of

total fixed capital), operating supplies (15% of maintenance

and repairs), and laboratory costs (15% of operating labor).

Calculate overhead and storage costs as 30% of the total

of labor, and maintenance and repairs.

Calculate local taxes and insurance costs as 2.2% of total

fixed capital.

Calculate total indirect costs as the sum of overhead and

storage costs, plus local taxes and insurance costs.

Calculate total manufacturing cost, excluding deprecia-

tion, as the sum of total direct and total indirect costs.

Calculate annual depreciation as fixed capital investment

divided by 15.

Calculate administrative costs as 25% of overhead and

storage costs.

Calculate distribution and market development costs as

5% ot total manufacturing cost.

Sum administrative, and distribution and market devel-

opment costs, to get total general expenses.

Sum total manufacturing cost, depreciation, and total

general expenses to get total expense (total annual costs).

Calculate annual revenue assuming all production sold at

specified price.

Subtract total annual costs from annual revenue to get net

annual profit before taxes.

Calculate income taxes as 21% of net annual profit, and

subtract from the latter to give net annual profit after taxes.

Calculate aftertax rate of return, in %, as 100 times the

sum of net annual profit after taxes plus depreciation,

divided by total capital investment.

The authors wish to thank Dr. K. Van Frankenhuyzen of the

Canadian Forest Service, Sault Ste. Marie, Ontario for valuable

insights into the Bt forestry market in Canada; and S. Dodds for

implementing the process diagram in BioProR Designer. Dr. A.

Margaritis thanks NSERC; EJLB for their financial support.

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