SEPA
                         United States
                         Environmental Protection
                         Agency
                                   Risk Reduction
                                   Engineering Laboratory
                                   Cincinnati, OH 45268
                         Research and Development
                                    EPA/600/S-94/016  September 1994
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ment has been superseded by the Facility Pollution Prevention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/60Q/R-92/Q88, 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

                                                     Printed on Recycled Paper

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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
refining. 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
paniculate 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 bn 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

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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
    of the cation and anton 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 chemi-
    cals used were well within industry standards.

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

  * Install a reverse osmosis unit to treat the wastewaterf rom 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.
           Com
          kernels
Steeping

w
Wet
milling


Hording
tank
                            Germ for   #   1   3^ Gluten for
                             com oil    Fiber fyr    pet food
                                      cattle and
                                      dairy feed

Starch \ *•
slurry |






Drying,
mixing.
cyclone
separation

4

Enzyme
addition
jk_
i Dextrose
'-r-

Dry com
starch to
brewery
Filtering,
removal of
particulate
matter
Fractionation



h. 90% h
Blend tank
iah fructose corr
                                                      .55% high fructose
                                                      com syrup
                                                     J5% high fructose
                                                     "com syrup
 Figun 1. Abbreviated process flow diagram.

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

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Table 2. Summary of Recommended Waste Minimization Opportunity


                                                        Annual Waste Reduction
                                                                                     Net Annual     Implementation       Simple
Minimization Opportunity         Waste S&sam Reduced     Quantity (Ib)     Per Cant       Sayings           Cost        Payback (yr)

Extend tha life of the fraction-        Fractionator resin          49,100           50          $139,280       $306,250          2.2
 ator rosin by reducing the Ot
 content of the incoming de-
 ionized water by installing
 a dagasiier. Oxygen degrades
 tfie resin in tf?e fractionator.

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