SW548
WRAPPING UP
THE SOLID WASTE
MANAGEMENT PROBLEM:
A Model for
Regional Solid Waste
Management Planning
-------
This report was prepared by the Mitre Corporation, Bedford,
Massachusetts, under Contract No. 68-01-2976.
An environmental protection publication (Igpi) in the solid waste
management series. Mention of commercial producTsdoes not constitute
endorsement by the U.S. Government.
Single copies of this publication are available from Solid Waste
Information, U.S. Environmental Protection Agency, Cincinnati, Ohio
45268.
-------
WRAPPING UP
THE SOLID WASTE
MANAGEMENT PROBLEM:
A Model for
Regional Solid Waste
Management Planning
bW-548
This report ^HH^as prepared for the Office of Solid Waste
under contract No. 68-01-2976
U.S. ENVIRONMENTAL PROTECTION AGENCY
1977
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402
-------
-------
FOREWORD
According to a 1973 survey conducted by the
National League of Cities, municipal officials across
the country feel that solid waste management is
the most critical issue facing their administrations.
And a recent Environmental Protection Agency
Report to Congress on Resource Recovery and
Waste Reduction states that the amount of municipal
solid waste disposed annually will increase by 30
million tons in the next 10 years.
States, regions, counties, cities and towns across
the country are facing critical questions about what
to do with solid waste. How can we plan systems
that dispose of these wastes? Which of the many
disposal options is the best? Which will meet en-
vironmental objectives as well as provide the least
expensive solution? These questions are particularly
difficult to answer when a plan must be developed
for a region consisting of a number of municipali-
ties, a large area, and a complex transportation
network.
In order to assist decision makers with these
and other complex questions, a computer model
called WRAP (Waste Resources Allocation Program)
has been developed. The model enables its users to
quickly sort out all the various options and generate
and calculate the cost of a number of solid waste
management plans.
Each plan indicates the selection, location and
capacity of sites and processes, and the flow of waste
throughout the region's transportation network.
Total annual cost of the system and cost per ton are
computed. One of the most important features of
the model is that it can be used to guide the decision-
making problem in the selection of alternative sys-
tems and to translate the impact of this selection into
cost figures.
What WRAP can do to help decision makers, and
how it can do it, are the subjects of this document.
This report has been prepared by the MITRE
Corporation, Bedford, Massachusetts, (Contract No.
68-01-2976) for the Systems Management Division
of the Office of Solid Waste, U.S. Environmental Pro-
tection Agency, under the direction of Ms. Donna M.
Krabbe.
-SHELDON MEYERS
Deputy Assistant Administrator for the
Office of Solid Waste
ill
-------
-------
TABLE OF CONTENTS
I
Page
INTRODUCTION: THE SOLID WASTE
MANAGEMENT PROBLEM 1
THE WRAP MODEL: A DECISION-
MAKING TOOL 2
WHAT IS A MODEL? 2
WHY SHOULD DECISION MAKERS
USE THE MODEL? 3
HOW IS THE WRAP MODEL USED? 3
WHAT IS NEEDED TO USE WRAP? 4
WHO SHOULD USE THE WRAP
MODEL? 5
WHEN SHOULD THE WRAP MODEL
BE USED? 5
WHERE HAS THE WRAP MODEL
BEEN USED? 5
WHAT KINDS OF QUESTIONS HAS
THE MODEL ANSWERED? 5
EXAMPLES OF MODEL USE 6
WHAT KIND OF DOCUMENTATION
IS AVAILABLE ABOUT WRAP? 10
HOW IS THE WRAP MODEL
OBTAINED? 10
-------
-------
INTRODUCTION: THE SOLID WASTE MANAGE-
MENT PROBLEM
The millions of tons of solid waste produced
annually create difficult decisions that must be made
at local levels. City councils, mayors, town managers,
public works officials, and state solid waste agencies
must decide today how to dispose of the solid waste
generated within their jurisdictions. The decisions
were once rather straightforward: engineering firms
were contracted to upgrade existing incinerators or,
build new ones, or new landfill sites were located.
But today, officials are confronted with a com-
plex and confusing array of alternatives and con-
straints.
landfills have traditionally been the least
expensive method of disposal, but today land is be-
coming difficult to find. Incinerators designed to
comply with environmental regulations are increa-
ingly expensive. Similarly, the newly emerging
resource recovery technologies offer environmentally
sound waste disposal, but are generally too expensive
for single communities to own and operate. Thus
there are strong pressures toward regionalization of
solid waste management functions.
Regionalization, however, gives rise to two fun-
damental problems:
complexity of the regional system design;
and
obtaining a political consensus amongst
the participants.
These issues can best be addressed by developing
and clearly presenting technical and economic data
about the consequences of various regional
approaches.
Selection and implementation of a regional solid
waste management plan can be viewed as one of ec-
onomic choice in which decision makers must seek
the least expensive solution that meets environ-
mental and political constraints. In this context,
solid waste management planning is sensitive to a
number of important conditions.
First, there are important variations in condi-
tions found in different regions. The quantity of
waste generated may vary considerably: from a very
few tons per day to many thousands of tons per
day. Regions differ in the prices obtainable for
recovered materials and in the transportation costs
necessary to realize those prices. They also differ
in the availability and proximity of land for landfill.
Therefore, the system that is right for one region is
not necessarily right for another.
Secondly, there is a tradeoff on haulage costs
versus processing costs that varies among tech-
nologies which is represented by the choice be-
tween central or dispersed locations for processing
facilities. Larger facilities can generally process a
ton of refuse at a lower cost than smaller facilities.
Thus, the decision to choose a centralized process-
ing center makes available economies of scale in
processing, but at the expense of higher haulage
costs to achieve the required volume of waste. On
the other hand, a system of dispersed processing will
offer lower haulage costs at the sacrifice of econo-
mies of scale in processing.
THE ECONOMIC TRADEOFF IN REGIONAL DESIGN
COST PER
TON OF
REFUSE
PROCESSING COST
TRANSPORTATION COST
O SIZE OF REGION
O GROSS TONNAGE
O NUMBER OF PARTICIPANT COMMUNITIES
Finally, a proper economic analysis of choice
should not only identify which alternative solid waste
management plan is preferred but also the compara-
tive costs of other "good" alternatives. This informa-
tion assists decision makers in their search for the
best "politically acceptable" alternative.
-------
THE WRAP MODEL: A DECISION MAKING
TOOL
Faced with an array of available alternatives and
considerations, decision makers are confronted with
the recognition that although regionalizing solid
waste management functions has economic advan-
tages, regionalization itself gives rise to some ques-
tions: Where should the disposal facility be located?
What is the preferred technology? Who should it
serve? How large should it be? Should partici-
pating communities haul their refuse directly to the
facility, or through intermediate transfer stations?
What size and where should the transfer stations be?
What will a system that meets all the objectives
cost? What are good alternatives and what will they
cost? In sum, what is the most economically pre-
ferred regional system design and what are the costs
associated with changing that design?
In order to assist those faced with these complex
issues, the U.S. Environmental Protection Agency has
sponsored the development of a computer model
called the Waste Resources Allocation Program,
WRAP. It specifically evaluates the economic trade-
How WRAP Can Help
AIDS IN STRUCTURING THE ANALYSIS
The decision maker.
defines issues to be examined
defines all processing and disposal alternatives
WRAP provides for uniform data definition
OBJECTIVE ECONOMIC ANALYSIS
WRAP
evaluates all options presented
selects lowest cost regional plan
identifies physical plan behind lowest cost solution
EFFECTIVE DECISION-MAKING
The decision-maker.
uses WRAP to generate a set of alternative plans
evaluates these alternative plans
considers the economic impact of choosing among alternatives
offs within the entire processing and disposal sys-
tems, including haul costs of collection vehicles to
a disposal facility, capital and operating costs of
transfer stations, resource recovery facilities and
landfills, transfer haul costs, and revenues available
from materials and energy recovery. It helps to sort
out all the various options within a specific region by
indicating a preferred solution that identifies the
minimum cost regional solid waste management plan
that meets all the objectives determined by its users.
Use of the model enables officials to study and ana-
lyze the costs and implications of all available alter-
natives.
WHAT IS A MODEL?
A model is an abstract representation of a system
(which can be a real thing or an idea) that is being
studied or examined. Although a model is never
more than a partial representation of reality, its use
allows one to adequately predict the effect of changes
in the system on that system's overall effectiveness
or cost.
The use of models is not new to modern man.
From the beginning of history, models have been
used to represent objects or ideas in an effort to ex-
press meanings. Physical models are perhaps the
most familiar; however, mathematical models (models
in which the system is represented by a set of equa-
tions which can be manipulated mathematically)
form the basis of the scientific disciplines.
Increasingly, computerized mathematical models
have been used as aids in management planning.
These are simply sets of mathematical equations ex-
pressed or written according to a particular set of
rules so that they can be processed by the computer.
The advent of the computer has proven invaluable
in modeling, as it frees its users from time consuming
and cumbersome calculations.
-------
WHAT IS THE WRAP MODEL?
WRAP is such a computer model. It can be used
as a tool by decision makers who are seeking a solid
waste management plan that most economically
meets environmental and political criteria. The
model reviews information about the region and from
this provides a minimum cost regional solid waste
management plan.
A key capability of WRAP is its ability to bal-
ance the economies of scale achievable through
centralization of processing at one location against
the additional haul costs required for centralization.
This makes it possible to determine what levels of
centralization make the most economic sense.
WRAP consists of a series of equations which
consider the sources of solid waste generation over a
given planning region, a set of possible sites, and
processes to be considered at those sites, as well as
various site and process capacity constraints. The
processes can be transfer stations, resource recovery
processes (including the extraction of recoverable
resources to be marketed), secondary processes
(which receive the residue of primary processes as in-
put) and various disposal processes. WRAP further
considers many transportation route alternatives
from sources of waste generation to sites, and from
sites to sites, and allows for site traffic constraints.
Processing costs are input to WRAP so as to re-
flect the economies of scale available for each proc-
ess, and the revenues from the marketing of recovered
materials. Haul costs are included, which increase
directly with both tonnage and travel time.
WRAP has three essential components:
structure which assures that each alternative
considered is feasible in the sense that all
wastes generated are entered into trans-
portation, that all wastes arriving at a site
are processed, that all residues generated
are processed at the site or entered into
transportation, and that no process ex-
ceeds the indicated tonnage maxim urns;
cost which assures that each alternative is
properly costed, including economies of
scale where appropriate; and
procedure an organized mathematical pro-
cedure which allows those options which
improve the solution to be separated
from those that make it worse, and in-
dicates when the procedure has identified
the least cost solution.
WHY SHOULD DECISION MAKERS USE THE
MODEL?
When planning a regional system, decision
makers should consider many different siting, proc-
ess, capacity and transportation alternatives. Design-
ing the minimum cost plan could involve hundreds
of time consuming and cumbersome calculations.
The WRAP model should be used because it allows
its users to make these calculations in a relatively
brief period of time, thereby permitting a continuous
planning and decision process. The model makes it
practical to examine many more questions and alter-
natives than would be possible without its use.
Because the model mathematically analyzes the
economic advantages and disadvantages of each of the
alternatives, it avoids the potential errors of decision
based purely on intuition.
HOW IS THE WRAP MODEL USED?
To use the WRAP model, data and information
about the region are structured in a set of model
runs. Each run examines specific issues and questions
that decision makers wish to address. The lowest
cost solution for each alternative being examined is
generated by the model, as well as a regional system
plan for each alternative. Decision makers can then
use the model to calculate the incremental costs of
moving from one alternative to another, and in
particular, the costs of moving from less political
acceptability to greater acceptability. In any given
planning region, for example, WRAP can be used to
-------
quantify the system cost difference in a regional
system compared with a county by county solution;
or the system cost impact of the political accepta-
bility or technical availability of certain resource
recovery or disposal processes; or the system cost
impact of alternative revenues for marketing re-
covered materials and energy.
Each plan generated by WRAP indicates what
kinds of waste disposal technologies would be best
for the region based upon differing assumptions,
where to locate the facilities for processing and
disposal as well as transfer stations, how much
capacity to install at each site, and the transporta-
tion network to link the elements of the system
together to achieve the minimum cost solution.
WHAT IS NEEDED TO USE WRAP?
Users need four things to apply the WRAP
model: a sense of the kinds of questions for which
answers are wanted; access to analytical skills; the
use of or access to a computer; and data.
CAPACITY
SITES
TRAfJSFEZ STATIONS
Questions To Be Asked
In order to sort out the various alternatives
and options, as well as to illuminate potential poli-
tical issues, users should have some feeling for the
kinds of questions for which they desire answers.
For example,
where should transfer stations be located?
is resource recovery viable? or
what is the cost impact of locating an ele-
ment of the system in one place versus
another?
On the other hand, time and budget should be allow-
ed to answer additional questions, for it has usually
been the case that the first few runs in answering a
question have suggested additional questions.
Ana ytical Skills
Model users either need to have, or have access
to, persons with analytical skills (for example, re-
gional planners) who are capable of examining the
situation and identifying and structuring issues
which WRAP will address. In addition, persons
with technical skills, who can actually use the model,
are necessary. The nature and extent of the skills
neeced can be determined by reading the supporting
information available about the WRAP Model, or by
inquiring of EPA's Systems Management Division
staff.
Coirputer
It is necessary to have access to a computer,
the actual size requirement of which may vary
according to the dimensions of the problem being
addressed. WRAP has been designed to operate
on an IBM 370/165 system.
Data
Two basic groups of data are required: those
that are tailored to the specific planning region; and
those that are generally applicable throughout the
courtry. The former group must be provided by
the users; the latter group is available from earlier
runs but should be reviewed before use. A brief
description of the specific kinds of data required
is provided here. However, all of these data and
potential sources are described in greater detail in
supporting volumes of the WRAP model designed
for its users.
Data to be provided include estimates of waste
generation volumes, possible sites being considered
for the location of transfer stations, primary and
secoidary solid waste processing facilities, and land-
fills; data on the local transportation network in
terms of transit times between the sources of waste
generation and each site, and among sites; and esti-
mates of revenues from the sale of recovered energy
and materials, representing local market conditions.
Other data required which are perhaps the
mosl difficult to obtain are the costs of the various
solid waste disposal processes being considered as
well as the estimated costs per ton-minute of trans-
-------
porting the refuse in packer and transfer vehicles.
The costs of all solid waste disposal processes being
considered need to be provided as input to the
model.
WHO SHOULD USE THE WRAP MODEL?
The WRAP model has been developed to assist
a wide range of decision makers who must make
choices concerning the future direction of solid
waste management. This includes officials within
various regional or county agencies, state agencies
which are responsible for this function, and city
agencies or officials, who are contemplating regional
systems.
Because the model has been developed to assist
in regional solutions, it should not be used unless
there are large enough geographical areas to warrant
investigation of economic tradeoffs.
WHEN SHOULD THE WRAP MODEL BE USED?
The WRAP Model should be used by decision
makers who are faced with situations in which
local solid waste disposal options are no longer
available, and regional solutions must be considered.
For example, the model can be used in the early
regional planning stages to identify how large the
region should be and which communities should
participate. It can determine which technology is
most appropriate and where it and subscribing
transfer stations should be located to produce the
minimum system cost to the communities. The
model can be used to determine the economic fea-
sibility of a system proposed for the region, the eco-
nomic effects of alternative volumes of waste, and
the effects of variations in revenues from recovered
materials.
During the early stages of planning, data, espe-
cially concerning process costs and markets are
necessarily estimates. The quality of the model's
solutions are, of course, only as good as the data
supplied to it. As the planning process progresses and
better data becomes available, WRAP should be used
to verify earlier plans or to evaluate any changes
which might be indicated.
WHERE HAS THE WRAP MODEL BEEN USED?
The WRAP model has been used in Northeast
Massachusetts and Greater St. Louis, and is currently
being used in other areas.
For the Commonwealth of Massachusetts,
the model was applied to a region encompassing
63 communities in Northeast Massachusetts and New
Hampshire in an effort to assist the Commonwealth
in the initial planning stages of a regional solid waste
management plan. The Commonwealth's plan em-
phasizes the implementation of regional resource
recovery systems throughout the State, and it desired
assistance in identifying the most efficient regional
system design for the first region.
Under EPA sponsorship, the model was applied
to identify and illuminate issues in Greater St. Louis,
where the Union Electric Co. is proposing to install
an 8,000 ton-per-day resource recovery system using
the shredded fuel process developed by them. The
proposed system included the marketing of the
recovered fuel to Union Electric's power generating
stations within Greater St. Louis. A local regional
planning agency, the East-West Gateway Coordinating
Council, requested EPA to fund an application of
the model to provide further insights into the ad-
vantages to the communities of participating in such
a plan.
WHAT KINDS OF QUESTIONS HAS THE MODEL
ANSWERED?
Use of the WRAP model by the Commonwealth
of Massachusetts provided significant information
concerning the elements and makeup of the state's
first regional resource recovery system.
-------
In response to a request from five communities
in the Merrimack Valley region who were faced with
critical disposal problems, the Commonwealth
agreed to sponsor the implementation of a regional
resource recovery system that would provide compre-
hensive, full scale disposal services to those communi-
ties. Recognizing that there would be clear economic
advantages to creating a larger region, the Common-
wealth used the model to determine:
Which of the many technologies would
produce the minimum cost solution?
How large an area should the system serve
in order to minimize the cost?
Where should the facility be located and
what size should it be?
Which communities should participate in-
transfer stations, and where and what size
should those transfer stations be?
What will be the overall system costs of
alternative system designs?
- The model indicated that with all options avail-
able, gas pyrolysis facilities at two sites in the region
would provide the minimum cost solution at $4.40
per ton. Because gas pyrolysis is in the developmen-
tal stages and not available for implementation, the
model was asked to provide the "next best" solution,
and selected sanitary landfill in six locations through-
out the region, at an incremental cost of around $3
per ton. Recognizing that landfills are of question-
able political acceptability in Massachusetts the
model was asked to pick the next best system, and
selected the dry shredded fuel process at a single
location for an incremental cost of $4 per ton over
the original solution. (A later analysis showed that
the markets for shredded fuel at that time were weak,
thus a different technology was finally recommend-
ed.) The selected system in each case indicated which
communities should participate, the location and
size of transfer stations and the secondary resource
recovery facility, as well as the most economical
transportation routes for communities to utilize in
reaching the facility.
The use of the model enabled the Common-
wealth to determine the minimum cost regional sys-
tem design, as well as the incremental costs of pro-
ceeding to a regional design of greater political
acceptability.
In the Greater St. Louis area, the East-West
Gateway Coordinating Council asked EPA to fund an
application of the model to assist in the resolution of
two issues of primary importance in that area. One
was to determine the economic feasibility of com-
munity participation in a resource recovery system
proposed by Union Electric compared to continued
landfill operations. The second issue concerned the
design of a resource recovery system, e.g., what de-
sign would produce the minimum cost to the parti-
cipa its?
Based upon the data inputs, the model solution
indicated that the resource recovery system was
indeed a viable, economically feasible solid waste
management plan, and was in almost all cases the
least cost system as compared to landfill. The gen-
erated solution included the location of the facilities
and transfer stations.
The model was then asked to provide informa-
tion relative to the incremental costs of changing that
design. Specifically, what would be the incremental
cost of prohibiting the flow of waste across the state
boundaries of Missouri and Illinois; of losing a parti-
cular market or a portion of the tonnage; and, what
would be the effect on the regional design and the
cost of forcing the model to consider locating the
facility in a particular location?
\lthough the cost of each of these solutions
did lot vary significantly, the result of these varia-
tions, both singly and together, changed the structure
of the preferred solid waste plan. For example, pro-
hibiting the interstate flow of waste altered the
regional configuration by locating the shredded fuel
processing facility farther away from the urban
area, and deeper into the suburbs.
The application of the model provided signi-
ficant information concerning the economic viability
of resource recovery in comparison with landfill
operations.
EXAMPLES OF MODEL USE
Examples of the kinds of issues which WRAP
can address are provided here to illustrate its capa-
bilities and versatility. These examples are drawn
from actual model applications in St. Louis and
Massachusetts.
-------
Background
The WRAP model was used to analyze a 450
square mile area in Greater St. Louis, encompassing
185 municipalities, and roughly two and one-half
million people, producing an estimated 8,000 tons
per day of residential, commercial and industrial
waste. One hundred eighty five landfills and dumps,
and two incinerators currently provide inadequate
disposal services to the area, often in violation of
environmental regulations. The Union Electric
Company is proposing a large resource recovery
system using the shredded fuel process developed by
the company, including the marketing of the fuel
to Union Electric's steam generating stations within
the region.
Data for the application was drawn from an
earlier report prepared for the East-West Gateway
Coordinating Council, one of the agencies concerned
with the course of solid waste management in the
region. The data comprised costs of the proposed
Union Electric process, the Bureau of Mines residue
recovery process, transfer stations, landfills, transfer
haul and rail haul, revenues from the sale of recovered
materials and energy, as well as waste generation
tonnages and possible site locations.
In Massachusetts, the Commonwealth desired
to provide solid waste disposal services for North-
eastern Massachusetts communities faced with
critical disposal problems. The WRAP model was
used to analyze a 750 square mile region, encom-
passing 63 communities, with over one million
people. Data for the Massachusetts application
included costs of various disposal technologies,
including pyrolysis, dry shredded fuel, landfill,
residue recovery, transfer stations and transfer
haul, as well as waste generation tonnages and possi-
ble sites.
Is Resource Recovery Economically Viable for a
Planning Region Under Consideration? How Can
WRAP Help in Determining the Answer?
The WRAP model was used in Greater St. Louis
in an effort to determine the answer to one of the
questions facing the region: Is it economically
sensible for the region's communities to participate
in the proposed Union Electric resource recovery
system? Because the size of the region under con-
sideration was extremely large, the seven-county
area and the City of St. Louis were divided into
29 districts, in order to promote an effective and
rapid manipulation of the data. The district bound-
aries consolidate smaller subdistricts of similar
character. This classification was used for the analy-
sis and presentation of data for areas larger than
subdistricts, but smaller than counties.
(Y) DISTRICT
DISTRICT BOUNDARY
- CITY/COUNTY BOUNDARY
O DISTRICT CENTROID
* CITY/COUNTY CENTROID
GREATER ST. LOUIS
Estimates were used for 1980 waste generation
tonnages for each of the 29 districts. Thirty-four
sites throughout the region were identified as possible
locations of transfer stations, primary and secondary
processing facilities, and landfills.
Two initial model runs were made to answer
the question of resource recovery viability based
upon locally supplied data. When offered only
resource recovery as an option (Run A), the WRAP
model generated a minimum cost regional plan,
at a cost of $1.253 per ton. When offered landfill
as an option, only one-half of one percent of the
waste flowed to landfill, while 99.5% entered re-
source recovery processing. Run B operated at a
cost of $1.249 per ton, only four tenths of a cent
less than Run A, as shown.
U Resource Recover) A Viable Option9
(A ( ompanson of the WRAP Model Runt, m St Louis)
Run
A ReM>uri.e Recovery
Landfill Seleued
None
B Ljndtili Added Ji Option 1 24l> for 400 TPD (0 57r of total)
The model solution indicated that the resource
recovery system proposed by St. Louis could indeed
be competitive with landfill. The revenues for fuel
and secondary materials proved too attractive to
permit a regional system that relied on landfill.
Which of the Many Solid Waste Disposal Options
Is Best for a Planning Region in Terms of Total
-------
System Cost? What Are the Effects on the Regional
System of the Unavailability or Political Unaccepta-
bility of Those Options Selected?
Three runs in the application of the WRAP
model for the Commonwealth of Massachusetts
provided the answers for these questions: Which of
several solid waste processing and disposal options
(pyrolysis, refuse-derived fuel, and landfill), is best
for the region? If the selected option is not available,
or is politically unacceptable, what are the effects
on both the system cost and the regional design?
Input data was prepared in a fashion similar
to that in St. Louis. The region was divided into 13
districts with centroid and waste generation identi-
fied in each district. Costs of transfer stations and
truck haul, possible sites, and distances and times
between those sites were determined. Costs for the
three solid waste disposal options were input, as
well as expected revenues from the sale of recovered
products for the resource recovery technologies,
and a residue recovery process. (It should be noted
that the residue recovery process used in the model
was that being planned at that time for the City of
Lowell, under an EPA grant.)
NORTHEASTERN MASSACHUSETTS PLANNING REGION
Three runs were made. The model solution
indicated that with all the options available the
minimum cost solution could be achieved through the
selection of the gas pyrolysis technology at two
locations within the 63 community region. The
minimum cost solution included a single transfer
station, and the residue recovery facility at a system
cost of S4.38 per ton.
Runs
(Options Available)
E Transfer Stations,
Shredded Fuel,
Gas Pyrolysis,
Residue Recovery,
Landfill
F Transfer Stations,
Shredded Fuel,
Residue Recovery.
Landfill
G Trar sfer Stations,
Shredded Fuel,
Residue Recovery
Structure of
Run Solution
Two Pyrolysis Facilities
One Transfer Station
Residue Recovery
$4.38/ton
Six Landfills
Residue Recovery
$7.34/ton
One Shredded Fuel Facility
Residue Recovery
Four Transfer Stations
$11.23/ton
Although the model selected the pyrolysis tech-
nology it was still in the developmental stages and
not ready for implementation. Consequently, a
second run was made, and the model was asked to
provide the "next best" solution. The model selec-
ted landfill at six locations throughout the region at
a cost of $7.34 per ton, or an incremental cost of
about S3.00 per ton.
REGONAL FACILITY
O RESIDUE RECOVERY
A TRANSFER STATION
C1 LANDFILL
WHERE SHOULD THE ELEMENTS OF THE REGIONAL PLAN BE LOCATED
IN ORDER TO ACHIEVE MINIMUM SYSTEM COST?
(MASSACHUSETTS RUNS E.F&G]
Because landfill disposal is of questionable
political acceptability in Massachusetts, Run G was
made asking the model for the next best solution.
The model determined that, given markets for the
sale of the recovered products, the minimum cost
solution consisted of a dry shredded fuel process in
one location, with four subscribing transfer stations
and the residue recovery facility. The cost for this
system was $11.23 per ton, or an incremental cost of
roughly $4.00 per ton.
The results of the WRAP application indicated to
the Commonwealth which of the many solid waste
disposal options would provide the minimum system
cost wiile meeting all applicable criteria. Most
importantly, the WRAP application gave the Com-
-------
monwealth the incremental dollar costs of the un-
acceptability of another.
Where Should the Components of a Regional Solid
Waste Management System Be Located in Order to
Achieve the Least Cost System? How Large Should
They Be? And Whom Should They Serve?
In the applications of WRAP previously dis-
cussed, a variety of questions were asked. In pro-
viding an answer to each, WRAP generated a system
design which comprised the best regional design that
would produce the minimum cost while answering
the specific question. Each design indicated where
the facilities should be located; how large and where
the transfer stations should be; and how the system
should be linked together.
The optimal region design generated by WRAP
for Massachusetts is shown schematically in the figure
above. The location and size of the system compon-
ents for each plan varies according to which option
was selected. In the regional design in which the
gas pyrolysis technology (Run E) was selected, one
processing facility handled 700 tons per day, and
served 15 communities, while the other, at 1500
tons per day, served 34 communities. A single
transfer station served one community with 90
tons per day.
Run F generated a minimum cost design com-
prising six landfills, and no transfer stations. Run G
generated a design consisting of a single dry shredded
fuel facility to serve the entire region, with four
transfer stations serving a total of 34 communities.
The remaining 19 communities hauled their waste
directly to the facility.
How Can WRAP Help in Determining the Effect on
the Preferred Regional Design of Having More or Less
Than the Expected Volume of Tonnage?
In both the St. Louis and Massachusetts appli-
cations, runs of the WRAP model were made to deter-
mine the effect on both the makeup of the regional
system and the overall system cost of having more or
less than the expected tonnage.
For St. Louis, Run E asked the model: What
is the preferred regional design if the private haulers
in the region, who are largely responsible for the haul
and disposal of commercial waste, do not join the
regional system? In order to determine this effect,
Run E included only half the amount of commercial
tonnage generated in the region. Since commercial
tonnages tend to be concentrated in urban areas,
the model generated a solution which caused primary
processing to be relocated toward the suburbs. The
cost impact of this change was relatively small.
Based upon locally supplied data, the model gener-
ated a system cost of $1.75 per ton, or an incre-
mental cost of $.31 per ton over the base case for
that solution.
WHAT IS THE EFFECT ON THE REGIONAL DESIGN OF HAVING
LESS THAN THE EXPECTED VOLUME OF TONNAGE?
1ST LOUIS RUN E]
RUN A I
PREFERRED REGIONAL DESIGN
RUN E
ONE HALF COMMERCIAL TONNACE
REGIONAL SYSTEM COST 11 44 TON
REGIONAL SYSTEM COST SI 75 TON
Runs H and I were made to determine the
effects of doubling the amount of tonnage in the
region on both the design generated when all options
were available (Run G). The purpose of these runs
was to determine how sensitive the model solution
was to radical changes in tonnage.
Run H generated a regional configuration that
was identical to that of Run E but with two addi-
tional transfer stations. The effect on the system
cost was a decrease from $4.38 per ton to $3.45
per ton.
Run I generated a somewhat different design
from that generated by the earlier Run G. The addi-
tion of twice the amount of tonnage caused a reloca-
tion of the shredded fuel facility to a more northerly
location, four transfer stations in slightly different
locations, and the residue recovery facility in the
northeastern part of the region. As in Run H, the sys-
tem cost decreased from $11.23 per ton to $8.47
per ton.
Comparison of Massachusetts Runs E, G, H and I
Run Structure Solution Cost
E All options available $4.38/ton
G Only shredded fuel available S11.23/ton
H Doubled tonnage, $3.45/ton
all options available
I Doubled tonnage, $8.47/ton
only shredded fuel available
-------
Use of the WRAP model in both Massachusetts
and St. Louis provided its users with valuable infor-
mation concerning the most economically preferred
solution for those regions.
WHAT KINDS OF DOCUMENTATION ARE
AVAILABLE ABOUT WRAP?
Comprehensive information that describes and
documents the use of the WRAP model is available.
This information comprises three documents: A
User's Guide; A Programmer's Manual; and a full
documentation of the model applications made for
EPA.
The User's Guide (127 Pages)
This guide is addressed to the individual or
group of individuals who are intending to use the
WRAP model to assist in the decision-making proc-
ess. The model is fully described in terms of its
makeup and equation structure to familiarize the
users with its capabilities. The guide contains a
full description of the kinds of data required for its
use, as well as how to prepare and utilize those data
and how to interpret outputs. Examples of pre-
pared data inputs are provided, as well as a guide to
the design and operation of the model.
The Programmer's Manual (345 Pages)
Addressed to the data processing individual,
this manual provides information about how the
program is actually applied and how it is run. An
overview of how the computer program is set up,
and how information inside the program is stored
is provided.
Operational and Exercise Runs (222 Pages)
This includes a full documentation of the model
applications made for EPA in St. Louis and Massa-
chusetts. It contains a detailed description of all
data inputs and outputs used, where these were
obtained, and the assumptions used. The document
is addressed to any individual who desires to ana-
lyze and review the actual model application in an
effort to more fully understand its capabilities.
HOW IS THE WRAP MODEL OBTAINED?
For further information about the WRAP model,
call or write:
WRAP
Office of Solid Waste Management
U.S. Environmental Protection Agency
401 M Street S.W.
Washington, D.C. 20460
at (202) 755-9125
yol385
SW-137c
10
------- |