v>EPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S-92/005 June 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Dairy
Gwen P. Looby and F. William Kirsch*
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). The WMAC
team at the University of Tennessee performed an assessment
at a plant manufacturing pasteurized milk, cream, buttermilk,
chocolate milk, ice cream mix, fruit drinks, and plastic jugs—
approximately 23,300,000 gal/yr of liquid product and 4,160,000
half gallon and 15,600,000 gallon plastic jugs/yr. Raw milk is
delivered to the plant, filtered, then centrifuged to separate the
cream from the skim milk which is then processed through a
high temperature short time (HTST) press. After the press, the
milk is bottled and shipped. Buttermilk is skim milk which has
been inoculated with cultures in a special processing tank.
Chocolate milk is made by adding chocolate powder and fruc-
tose to blended milk prior to processing in the HTST press.
The team's report, detailing findings and recommendations,
indicated that the majority of waste is wastewater generated
from all processes in the plant and that the greatest savings
could be obtained by instituting a wastewater management
plan to reduce uncontained milk waste (38%) and wastewater
(90%).
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 the authors. This brief provides only
* University City Science Center, Philadelphia, PA 19104
summary information and is not intended for use as a thorough
analysis.
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 is to reduce or eliminate the waste at its source.
University City Science Center (Philadelphia, PA) has begun a
pilot project to assist small- and medium-size manufacturers
who want to minimize their formation 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 the University of
Tennessee's (Knoxville) WMAC. The assessment teams have
considerable direct experience with process operations in manu-
facturing 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 $50 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.
/TTV
<^9 Printed on Recycled Paper
-------
Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs folbw the proce-
dures outlined in the EPA Waste Minimization Opportunity
Assessment Manua/(EPA/625/7-88/003, July 1988). The WMAC
staff locates the sources of waste in the plant and identifies the
current disposal or treatment methods and their 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 supporting tech-
nological and economic information is developed. Finally, a
confidential report that details the WMAC's findings and recom-
mendations (including cost savings, implementation costs, and
payback times) is prepared for each client.
Plant Background
This dairy produces pasteurized milk (2% fat, 1% fat, 1/2% fat,
whole, and skim), cream, buttermilk, chocolate milk, ice cream
mix, and fruit juice drinks. The plant also manufactures milk
jugs from HOPE (high density polyethylene) pellets. The plant
operates 4,420 hr/yr to produce approximately 23.4 million gal
of milk annually.
Manufacturing Process
Raw Milk Processing
The dairy receives fresh raw milk via 19 to 20 daily truck
deliveries. Raw milk is pumped from the trucks through a
centrifuge clarifier where undesirable solids in the milk are
removed. Waste from the clarifier is collected in a holding tank
and is trucked offsite daily to be used as fertilizer. After each
delivery the truck tanks are cleaned with a Clean-ln-Place
(CIP) cleaning system which utilizes a spray system built into
each tank. Initially a four-second burst of water at 60-80 psi is
supplied to the tanks; the water/milk solution is pumped through
the clarifier and processed with the milk initially pumped from
the truck. That rinse is followed by an alkaline rinse, an acid
rinse, and a rinse containing a sanitizing agent. The rinse
solutions drain to the municipal sewer. During one CIP cycle
each day the clarifier is also washed.
It is estimated that approximately 2% of the total amount of
milk purchased annually is lost during processing. Solids re-
moved from the milk in the clarifier account for part of the
volume loss. The remainder results from milk spills and leaks
from processing equipment, contamination of milk with the CIP
sanitizer solutton during HTST press washing, and spills of
packaged product in the storage cooler. Spills and leaks of milk
during processing are partially contained in equipment drip-
pans; drip-pan waste is collected by a local farmer and is
subsequently used as hog feed. The remaining milk lost annu-
ally is drained to the municipal sewer. It is not possible to
quantify the amounts of waste milk associated with each piece
of equipment.
Milk exiting the clarifier is cooled to 36°F in a cooling press. At
this point a second CIP system is used to clean the raw milk
lines. Drip-pan waste is generated and uncontained spills and
leaks occur at the cooling press. Five percent of the milk from
the cooling press is shipped to other dairies for further process-
ing. The remaining 95% is transferred to one of three storage
silos.
Milk in the storage silos contains on average 3.75% butterfat.
Approximately 40% of the milk from the storage silos is di-
rected through a centrifuge where cream is separated from the
milk. The cream contains about 40% butterfat and the remain-
ing skim milk has a butterfat content of approximately 0.25%.
Each fraction is stored in its own tank. Cream from the cream
storage tank is transferred to either the ice cream mix process
or the filling machines where cream is packaged and trans-
ported to the storage cooler (33°F). Drip-pan waste is gener-
ated at the filling machines and uncontained spills and leaks
occur at both the filling machines and in the storage cooler.
A fraction of the skim milk in the storage tank is transferred to
the buttermilk process. Another fraction is transferred to the
pasteurized milk process to be pasteurized and homogenized
and sold. The remainder of the skim milk is blended with whole
milk from the storage silos in a processing blender to obtain
milk with different fat contents. Milk from the processing blender
is then sent to the pasteurized milk process, chocolate milk
process, and the ice cream mix process.
Pasteurized Milk
Skim, 1/2% fat, 1% fat, 2% fat, and whole milk are received
from the skim milk storage tank and blend tank and are pas-
teurized and homogenized in two HTST presses. The first
stage of the HTST press is a regenerator (heat exchanger)
section in which heat is transferred from milk already in the
press to milk coming into the press. After passing through the
regenerator, milk is steam-heated further to 172°F in a
vacuumizer where bacteria in the milk are killed. Then it is
subjected to a pressure of 1,900 psi in a homogenizer. Follow-
ing the homogenizer, milk flows back through the regenerator
transferring its heat to incoming milk. The milk is then cooled to
36°F in a chilled water heat exchanger and finally to 32°F in a
glycol cooling unit. The dairy operates 150- and 180-HP boilers
which are used to produce the needed steam. Steam condom-
sate is disposed of to the municipal sewer as is the cooling
water because of the risk of contamination. The HTST presses
used in all of the dairy processes are washed a total of five
times per day with a water rinse and three times per day with
an acid wash. Wastewater is disposed of to the municipal
sewer. During the washing process, milk remaining in the
presses may be contaminated with the acid or it may be diluted
with water. Diluted milk is reprocessed and contaminated milk
is disposed of in the municipal sewer. Some waste milk is also
collected in drip-pans under the presses.
The pasteurized and homogenized milk is then transferred to a
10,000-gal storage tank where it is stored at 33°F. Next,
cardboard cartons and plastic jugs are filled with milk from the
storage tank and transported to the storage cooler. A third CIP
system is used to clean the pasteurized milk lines. This system
generates waste cleaning solution which is disposed of in the
municipal sewer. Drip-pan waste is generated at the filling
machines and spill waste and leaks occur at both the filling
machines and in the storage cooler (33°F).
Buttermilk
Skim milk is received from the skim milk storage tank and is
pumped to a processing tank. In the processing tank the milk is
steam-heated to 186°F for 30 min. (Steam condensate is
disposed of in the municipal sewer.) The milk is then cooled to
75°F in the tank with chilled water. (Cooling water is disposed
of in the municipal sewer.) At 75°F the milk is inoculated with
"ready-set" culture to promote bacterial growth which thickens
and flavors the milk. Finally, the processing tank is fed with
chilled water to cool the milk to a temperature between 40 and
-------
4S°F Ks Vne buttevnVrtk \ank is emptied, drip-pan waste is
generated and spills and leaks occur.
The buttermilk is then pumped to filling machines for packaging
and is transported to the storage cooler. Drip-pan waste is
generated at the filling machines and leaks and spills occur at
both the filling machines and in the storage cooler (33°F). The
pasteurized milk line C1P system is used to clean the process-
ing tank and the filling machines.
Chocolate Milk
Milk from the blend tank is pumped to a mixing tank where
chocolate powder and fructose are added to the milk. The raw
milk line CIP system is used to wash the mixing tank as
needed. After the ingredients are mixed, chocolate milk is
pasteurized and homogenized in an HTST press, as described
in the pasteurized milk process. Following pasteurization and
homogenization, chocolate milk is stored in a tank until it is
transferred to filling machines for packaging. Finally, packaged
milk is transferred to the storage cooler. The pasteurized milk
line CIP system is used to wash the storage tank and the filling
machines. Drip-pan waste is generated at the filling machines
and spills and leaks occur at both the filling machines and in
the storage cooler (33°F).
Ice Cream Mix
Milk is received from the blend tank and is mixed in a blender
with cream from the cream storage tank, milk powder, fructose,
stabilizers, and vanilla. The mixture is then transferred to one
of three holding tanks. The raw milk line CIP system is used to
clean the blender and the holding tanks.
From the holding tanks the mixture is pumped to an HTST
press as described in the pasteurized milk process. Following
processing in the press, ice cream mix is stored in a storage
tank at 33°F. The mix is then pumped from the storage tank to
filling machines where it is packaged and is then transferred to
the storage cooler. Drip-pan waste is generated at the filling
machines and spills and leaks occur at both the filling ma-
chines and in the storage cooler. The pasteurized milk line CIP
system is used to clean the storage tanks and the filling
machines.
Fruit Drinks
In addition to milk-based products, this dairy also produces
several different flavors of fruit drinks. City water is first pumped
through a charcoal filter which removes debris and chlorine
from the water. Periodic backwashing of the filter results in
wastewater which is drained to the municipal sewer. Next, the
de-chlorinated water is mixed in a steam-heated mixing tank
(168°F) with preservative, liquid juice concentrate, and either
sucrose or fructose. Spills of approximately 2,080 gal are
drained to the municipal sewer each year.
The drink mixture then enters the small HTST press. Spills,
leaks, and contaminated product from the presses are drained
to the municipal sewer. There is no drip-pan waste associated
with this process.
Drink mixture from the HTST press is then transferred to a
surge tank. Finally, the drink mixture is pumped to filling ma-
chines where it is packaged in cartons or jugs and transferred
to a storage cooler. Spills from the filling machines and the
storage cooler are drained to the municipal sewer.
Waste Water
Wastewater streams from the entire dairy are collected in a
wastewater collection pit before discharge to the municipal
sewer. Most of the waste streams were 'described previously.
Wastewater is also generated in floor washing operations,
partially from cleaning up milk spills as they occur throughout
the day, but mainly from the practice of turning water hoses on
during the entire cleanup shift. The cooling water for the chiller
system is also treated as is the daily sanitizing waste from the
cleaning of all tanks in the plant during the cleanup shift.
Blow Molding
This dairy produces 1-gal and 1/2-gai jugs used in packaging
product. High density polyethylene (HOPE) pellets from a stor-
age silo enter a blend hopper where they are mixed with
regrind pellets. Following the blend hopper, the pellets are
gravity fed into the extruder barrel, melted at 325°F. and then
extruded into molds for blow-molding with compressed air.
Jugs are automatically ejected from the mold and trimmed of
excess plastic. Next, the jugs are leak tested. Defective jugs
and trimming are reground for reuse which results in the
generation of dust. Finally, the jugs are labeled and transferred
to the filling line.
Existing Waste Management Practices
• Milk solids from the clarifier are trucked offsite by a
local farmer for use as fertilizer.
• Drip-pans have been installed to contain milk spills
and leaks. The collected waste milk is then trans-
ported offsite by a local farmer for use as hog feed.
• Wastewater streams and milk-contaminated waste
streams are combined to achieve dilution before dis-
charge to the municipal sewer.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the quantity of the waste, and the annual man-
agement costs are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The type of waste,
the minimization opportunity, 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, in most cases, the economic savings of
the minimization opportunities result from the need for less raw
material and from reduced present and future costs associated
with waste treatment and disposal. Other savings not quantifi-
able by this study include a wide variety of possible future
costs related to changing emissions standards, liability, and
employee health. It should also be noted that the savings given
for each opportunity reflect the savings achievable when imple-
menting each waste minimization opportunity independently
and do not reflect duplication of savings that would result when
the opportunities are implemented in a package.
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.
•U.S. Government Printing Office: 1992— 648-080/60015
-------
Table 1. Summary of Current Generation
Waste Generated
Milk solids
Drip-pan
milk waste
Uncontalned
milk waste
Wastewater
Spilled
frultjulce
High density
polyethylene dust
Source of Waste
Ctarifier in the raw milk processing line. Milk solids are
shipped offsite for use as fertilizer.
Milk spills and leaks from various processes. The milk is
collected in drip-pans; a local farmer transports the waste
offsite for use as hog feed.
Milk spills and leaks from various processes. Uncontained and
contaminated milk is sent to the plant's waste collection pit
and Is discharged into the municipal sewer.
Truck and clarifier washing, milk line washing, HTST press
washing, steam condenser water. Wastewater is collected
In the plant's waste collection pit and is discharged into
the municipal sewer.
Fruit juice spills from process line. Waste fruit juice is collected
in the plant's waste collection pit and is discharged into the
municipal sewer.
Blow molding of jugs. Dust is generated during regrind of defective
jugs.
Annual Quantity
Generated (gal)
65,000
65,000
394,000
37,299,660
6,340
1,300
Annual Waste
Management Cost ($)
8,800
790
(see wastewater)
194,190'
(see wastewater)
0'
' Includes costs for monitoring plant effluent; plant labor costs for sampling, testing, handling, and record keeping; surcharges imposed by the
POTW; and sewer charges.
1 The plant reports no cost associated with the disposal of this waste.
Table 2.
Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
Annual Waste Reduction
Quantity (gal) Percent
Net Annual
Savings
Imple-
mentation
Cost
Payback
Years
Uncontained milk waste
Wastowater
Institute a wastewater management plan. 147,810
Begin an ongoing employee training
and awareness program to minimize
milk spills due to human error and
to minimize water usage due to
lazy maintenance practices.
Minimize the use of water for clean-
up through the use of high pressure
nozzles and automatic shut-off
nozzles on hoses.
Install an activated sludge treatment
system to treat the wastewater
collected in the waste pit before
discharge to the POTW. Currently,
the effluent does not meet the
POTWs standards and surcharges
are being assessed.
14,601,600
38
39
$320,810
$661,200
2.1
United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S-92/005
------- |