Table 2. Summary of Recommended Waste Minimization Opportunity

Annual Waste Reduction
TOO Net Annual Implementation Simple
Minimization Opportunity Waste Stream Reduced Quantity (Ib) Per Cent Savings Cost Payback (yr)
Extend the life of the fraction- Fractionator resin 49,100 50 $139,280 $306,250 22

ator resin by reducing the O,
content of the incoming de-
ionized water by installing

a dagasifier. Oxygen degrades
the resin in the fractionator.



Table 1. Summary of Currant Waste Generation

Annual Quantity Annual Waste
Waste Generated Source of Waste Generated (Ib) Waste Management Method Management Cost"
Spent cation resin Dextrose ion exchange 8,750 Shipped to landfill $15,630
Cation regeneration liquid Dextrose ion exchange 257,000,000 Balancad; discharged to onsite ponds 346,000
Sweeten-off rinse water Dextrose and fructose ion exchange 36,900,000 Balanced; discharged to river 3,320
Spent anion rasin Dextrose ion exchange 25,700 ‘Shipped to landfill 109,090
Anion regeneration liquid Dextrose ion exchange 229,000,000 Balanced; discharged to onsite ponds 79,700
Anion caustic cleaning liquid Dextrose ion exchange 3,320,000 Balanced; discharged to onsite ponds 12,100
Spent water softener resin Water softening 1,590 Shipped to landfill 2,290
Water softener regeneration liquid Water softening 25,740,000 Balanced; discharged to onsite ponds 2,050
Spent mixed-bed cation resin Fructose ion exchange 9,180 ‘Shipped to lanctil! 18,430
Cation regeneration liquid Fructose ion exchange 100,000 Balanced; discharged to onsite ponds 3,480
Spent mixed-bed anion resin Fructose ion exchange 16,300 Shipped to landfill 74,760
Anion rageneration liquid Fructose ion exchange 392,000 Balanced; discharged to onsite ponds 32,900
Regeneration rinse water Regeneration of ion exchange resins 66,900,000 Balanced; discharged to onsite ponds 9,720
Spent fractionator resin Fractionation 98,200 ‘Shipped to landfill 286,330
Fractionator regeneration liquid Fractionation 2,400 Balancad; discharged to onsite ponds 0
PH adjustment reagents Wastewater treatment 4,400,000 Balanced; discharged to onsite ponds 9,680
Waste laboratory chemicals Tast laboratory 290 Shipped offsite for incineration 4,140

* Includes waste treatment, disposal, and handling costs and applicable raw material costs.




United States
Environmental Protection
Agency

Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268

Research and Development

EPA/600/S-94/016 September 1994

SEPA

ENVIRONMENTAL

RESEARCH BRIEF

Waste Minimization Assessment for a Manufacturer
of Corn Syrup and Corn Starch

Harry W. Edwards*, Michael F. Kostrzewa’,
and Gwen P. Looby**

Abstract

The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. In an effort to assist these manufactur-
ers, Waste Minimization Assessment Centers (WMACs) were
established at selected universities and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). That docu-
ment has been superseded by the Facility Pollution Prevention
Guide (EPA/600/R-92/088, May 1992). The WMAC team at
Colorado State University performed an assessment at a plant
that produces corn syrup and dry corn starch. Corn is pro-
cessed by wet milling and refining into the desired products.
The team's report, detailing findings and recommendations,
indicated that the largest quantities of waste are generated by
the regeneration of the ion-exchange columns used in the
production processes and that significant savings could result
from extending the life of the fractionator resin.

This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
nati, OH, to announce key findings of an ongoing research
project that is fully documented in a separate report of the
same title available from University City Science Center.

Introduction

The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
additional stress on the environment. One solution to the prob-
lem of waste generation is to reduce or eliminate the waste at
its source.

* Colorado State University, Department of Mechanical Engineering
** University City Science Center, Philadelphia, PA

University City Science Center (Philadelphia, PA) has begun a
pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the in-house expertise to do so. Under agreement with EPA's
Risk Reduction Engineering Laboratory, the Science Center
has established three WMACs. This assessment was done by
engineering faculty and students at Colorado State University's
(Fort Collins) WMAC. The assessment teams have consider-
able direct experience with process operations in manufactur-
ing plants and also have the knowledge and skills needed to
minimize waste generation.

The waste minimization assessments are done for small and
medium-size manufacturers at no out-of-pocket cost to the
client. To qualify for the assessment, each client must fall
within Standard Industrial Classification Code 20-39, have gross
annual sales not exceeding $75 million, employ no more than
500 persons, and lack in-house expertise in waste minimiza-
tion.

The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, and
reduced waste treatment and disposal costs for participating
plants. In addition, the project provides valuable experience for
graduate and undergraduate students who participate in the
program, and a cleaner environment without more regulations
and higher costs for manufacturers.

Methodology of Assessments

The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the proce-
dures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The
WMAC staff locate the sources of waste in the plant and
identify the current disposal or treatment: methods and their

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associated costs. They then identify and analyze a variety of
ways to reduce or eliminate the waste. Specific measures to
achieve that goal are recommended and the essential support-
ing technological and economic information is developed. Fi-
nally, a confidential report that details the WMAC’s findings
and recommendations (including cost savings, implementation
costs, and payback times) is prepared for each client.

Plant Background

This plant produces high fructose corn syrup and dry corn
starch. It operates 24 hr/day, 365 days/yr to process over 8
million bushels of corn. Approximately 265 million Ib/yr of corn
syrup and 100 million Ib/yr of corn starch are produced.

Manufacturing Process
The two major processes in this plant are wet milling and

tefining. Those processes are described in the following sec-
tions.

Wet Milling

Corn kernels are first softened by steeping in warm water. The
steep water dissolves salts, soluble carbohydrates, and protein
in the corn. The softened kernels are degerminated in a milling
process that tears the kernels apart and extricates whole corn
germs. This process yields a pulpy material that contains germ,
starch, gluten, and fiber. The germ is recovered using
hydroclones, dried, and sold for processing into corn oil.

The remaining slurry containing starch, gluten, and fiber under-
goes additional milling to release the rest of the starch from the
fiber and then to separate the fiber from the gluten and starch.
After washing to remove additional starch, excess water is
removed from the fiber by pressing and drying. Steep water
and broken corn are added to the dried fiber and the resulting
mixture is sold for use as cattle and dairy feed.

Centrifuges are used to separate the gluten from the starch
slurry. The gluten is thickened by removing excess water and
then dried in rotary vacuum filters to a cake-like consistency.
The gluten is further dried to a granular form for sale as a pet
food additive.

Refining

The remaining starch slurry from the wet milling process serves
as the starting material for this company's two major prod-
ucts—dry corn starch and high fructose corn syrup. The slurry
is washed with fresh water in a counterflow system and fed to
a holding tank. Some of the slurry is drawn from the tank into
the refinery for processing into corn syrup. The balance is
processed into dry corn starch by a sequence of centrifuge
drying, mixing, heated air drying, and cyclone air separation.
The resulting corn starch is sold to a local brewery.

In the refining process, three enzymes are used in a series of
operations to convert the starch slurry into fructose. Starch
granules are broken down into chains of dextrose molecules by
the first enzyme. The second enzyme breaks down the dex-
trose chains into individual dextrose molecules. Insoluble ma-
terials and unconverted starch are filtered from the dextrose
solution in rotary drum vacuum filters. After filtering, colored
particulate matter is removed in a carbon column.

The dextrose solution is then sent through a set of ion ex-
change columns that remove metal salt impurities from the

solution. Water is removed from the solution in an evaporator
before the third enzyme is added. That third enzyme converts
the dextrose into fructose. The resulting fructose follows a
process similar to the one for the dextrose solution—decoloriz-
ing, ion exchange, and evaporation.

Some of the fructose goes to a finishing evaporator yielding
55% high fructose corn syrup. That grade of corn syrup is sold
or reserved for blending. The rest of the corn syrup is further
enriched in a fractionator that uses calcium resins to remove
remaining dextrose and impurities from the corn syrup. Deion-
ized water is then used to dilute the syrup to the highest grade
produced (90%). The 90% high fructose corn syrup is sold or
blended with the 55% high fructose corn syrup to yield 75%
high fructose corn syrup, the other grade produced by this
plant. The corn syrup is sold to various clients in the soft drink
industry.

The largest volume waste streams do not result from the
Production process itself, but from regeneration of the ion
exchange columns used in the production process and from
the treatment of city water for use in the production process.
Hazardous lab wastes are generated in the test lab, but these
wastes are minor in volume.

A simplified process flow diagram is given below.

Existing Waste Management Practices

This plant already has implemented the following techniques to
manage and minimize its wastes.

* Cation exchange resins that are used in dextrose processing
are treated with a brine solution that keeps the products of the
resin regeneration solution. Without that treatment, an un-
desired byproduct precipitate (gypsum) would form.

Sulfuric acid solution that is used to regenerate cation ex-
change resins is a mixture of fresh acid and reclaim acid.

The water that is used to rinse the ion exchange resins prior
to regeneration (“sweet water"), which contains residual
carbohydrates, is given to local pig farmers instead of being
Processed through the wastewater plant.

Spent diatomaceous earth from the rotary drum vacuum
filters used to remove insoluble materials and unconverted
‘starch from the dextrose solution is added to animal feed
instead of being landfilled.

Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the quantity of the waste, the waste management

method, and the annual treatment and disposal costs are given
in Table 1.

Table 2 shows the opportunity for waste minimization that the
WMAC team recommended for the plant. The minimization
opportunity, the type of waste, the possible waste reduction
and associated savings, and the implementation cost along _
with the payback time are given in the table. The quantities of
waste currently generated by the plant and possible waste
reduction depend on the production level of the plant. All
values should be considered in that context.

It should be noted that the economic savings of the minimiza-
tion opportunity results from the need for less raw material and
from reduced present and future costs associated with waste
treatment and disposal. Other savings not quantifiable by this


study include a wide variety of possible future costs related to
changing emissions standards, liability, and employee health.

Additional Recommendations

In addition to the opportunity recommended and analyzed by
the WMAC team, additional measures were considered. These
measures were not completely analyzed because of insuffi-
cient data, minimal savings, implementation difficulty, or a
projected lengthy payback. Since one or more of these ap-
proaches to waste reduction may, however, increase in attrac-
tiveness with changing conditions in the plant, they were brought
to the plant's attention for future consideration.

+ Reduce the quantity of chemicals used during regeneration
ofthe cation and anion exchange columns in the fructose and

dextrose lines. Initially it was thought that excessive amounts.
of chemicals were used during the regeneration process.
Further investigation determined that the quantities of chami-
cals used were well within industry standards.

Investigate the cause of the resin breakdown in one of the
fructose ion exchange columns.

Install areverse osmosis unit to treat the wastewater from the
flushing of the ion exchange resins used to treat incoming city
water; recycle the treated water.

This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmen-
tal Protection Agency. The EPA Project Officer was Emma
Lou George.

— 74
c Wer Holding |_| Starch /—————> Enzyme
komels Stesping |—>| ming [1 tank [>| sluny | ‘addition
{Lp e ,
Drying,
Gorm tor KY Ss cuter or ming | __ ¥
‘at wr ott ez, | (aa
an og L
onteom | removal o
starch to particulate
brewery matter
fon
exchange
—_ [
lon Removal of Enzyme
exchange \e—) Particulate | rece La addition ké—4 Evaporation
Evaporation |—t1 Evaporation [> 25% Biot friciose
; 75% high fructose
Fractionation |p) Bland tank be 2 man

L, 20% high fructose com syrup

Figure 1. Abbreviated process flow diagram.