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Virtual garbage: computer simulation in solid waste planning.

LAST year, when Columbus, Ohio asked Tina Redmond to help the city develop alternatives for its garbage and recycling services, she began by punching numbers into a computer program. Three weeks later, she had what the city wanted: cost projections for more than 60 solid waste and recycling programs that the city could implement. Her projections were backed by hundreds of pages of computer printouts. "I have a stack of paper that's a foot and a half high," said Redmond, director of the Franklin County Solid Waste Authority, the agency that manages waste disposal facilities for the Columbus metropolitan area.

The computer program Redmond used is called WastePlan, a solid waste planning model developed by the Tellus Institute, a Boston-based research and development center. WastePlan helped Redmond cost out a large array of recycling program and equipment options, including conventional curbside collection systems, "blue-bag" co-collection systems, alleyway collection using 300-gal containers, paper vs. plastic storage bags, and one option that would send mixed garbage--by direct haul or transfer--to a large-scale mixed-waste processing facility 20 miles outside the city.

Redmond completed the project on her own--after office hours. The computer-aided planning model helped her build the scenarios in a fraction of the time she used to spend coming up with the projections by hand. "I've done the exact same thing before, only I did it manually, and it took me forever," she said. Redmond will probably use WastePlan to help write an update to the authority's solid waste management plan. She sees other counties in Ohio, all of which have access to the software, doing the same thing.

"We may see a lot more of them using WastePlan instead of going and hiring consultants," said Redmond.

Computer Simulation

WastePlan is one of a handful of computer models--most developed in the past few years--that attempt to simulate the complex world of solid waste management. The beauty of computer simulation, proponents say, is that it enables planners to develop and assess policy and technical alternatives quickly and cheaply on a computer screen. Used wisely, computer models can save governments time and money by reducing the need for costly pilot programs, outside consultants, and tedious, fragmented number chasing.

Others, however, doubt that computer programs can accurately reflect real world complexities. While they acknowledge the usefulness of computer spreadsheets and other automation tools, they are not ready to entrust key policy decisions to a "black box," and they wonder whether the average solid waste manager has the time or inclination to master yet another complicated piece of software.

"I think computer models are nice," said Chaz Miller of the National Solid Wastes Management Association, "but you got to remember they're all garbage in, garbage out. They're prisoners of the assumptions of the people that make the models and the quality of data you put in."

Nonetheless, a growing number of government planners and solid waste managers use modeling software to help them forecast state and regional waste-disposal capacity, set user fees, develop solid waste management plans and make large capital-investment decisions. The Eastern Rensselaer County Solid Waste Authority, for example, used WastePlan to help plan a $3.3-million composting facility. On the basis of the model's calculations, the authority decided they could save money by having the authority--rather than the vendor--own the facility. The authority also used the model to estimate the quantity of non-compost-able waste that would have to be shipped to a regional incinerator--and how much this "waste export" operation would cost over 20 years. Meg Morris, the authority's director, is satisfied with the program, though she admits "getting lost" in it a couple times. She also had to beef up her computer's memory so WastePlan would run faster; the program needs at least three megabytes of RAM.

Developed in 1988 for the U.S. Office of Technology Assessment, WastePlan is probably the most widely used--and most vigorously marketed--solid waste planning model currently available. Seven states have purchased special licenses allowing them to distribute the program to local cities and counties, though Tellus is not sure how many individual users are out there. Other purchasers of WastePlan include New York City, the U.S. Army Corps of Engineers in Illinois, the Tennessee Valley Authority, the Audubon Society, two private consultants, five universities, and Beijing, China.

Though WastePlan is by far the most widely used model, it is not the only one available. Probably the first solid waste computer model was the Waste Resource Allocation Program--or WRAP--developed by the Environmental Protection Agency in 1977. Several more models have come out since, among them:

* RRPLAN (Resource Recovery Planning Model), developed by the U.S. National Bureau of Standards;

* SWAP (Solid Waste Analysis Package), developed by the University of New Hampshire;

* SWIM (Solid Waste Integrated Management), developed by the Royal Melbourne Institute of Technology and the University of Melbourne;

* MUNI (Municipal), developed by the Eastman Chemical Company;

* GIGO (Garbage In, Garbage Out), developed by the University of California, Davis.

Asking the Questions

Model builders use a variety of computer languages and modeling techniques. Some, like WRAP and SWAP, rely on "optimization" routines; others, like WastePlan and GIGO, favor simulation techniques and are built around a series of spreadsheets. A planning session with a computer model starts by plugging in as much information as possible about the existing community--its population, geography, waste stream, vehicle fleet, and other waste-related infrastructure--and proceeds by conducting what if experiments on this "virtual" community.

What would happen, for instance, if the city changes to a fully-automated refuse collection system that cuts crew size in half? What if it builds 15--or 50--recycling drop-off centers, or starts a commercial recycling service? How much would these programs cost over time and how would the waste stream be impacted? Being able to ask these kinds of questions--and getting immediate answers--is what makes the idea of computer simulation so appealing.

In Minnesota, the state had some very specific questions, and turned to WastePlan to answer them. "What's going to happen in terms of capacity, that was our question," said Tom Osdoba of the Minnesota Office of Waste Management. "What if over the next 20 years, through a combination of new policies plus local action, this happens, recycling rates go up to this level, waste generation changes at this rate over time. Are we going to run out of capacity? If so, when, and how much more capacity would we need and how much would it cost?" Osdoba incorporated WastePlan's capacity projections into the state's solid waste management plan, which was submitted to the legislature last year.

As with any model, the real question is whether the answers--the program's output--are believable. David Cornell, who created the MUNI model for Eastman Chemical, has tested the predictions of his model against real-world numbers. For example, he recently compared MUNI-generated cost projections with actual costs taken from programs in Palm Beach and Seattle. "I plugged in a very minimal amount of information, and it cranked out total costs pretty accurately," reported Cornell.

Researchers at the University of California-Davis tested their GIGO model against the actual costs reported by their local refuse collection operation. After loading in baseline data, such as hourly wages for drivers, vehicle type and cost, number of houses, and the time spent stopping at a house, the model was able to predict fairly closely what the city was actually experiencing. "You crunch the collection module and sure enough, the collection cost is about what it is for Davis per ton," said Robert Anex, a research associate at the university who helped to write the program. "That makes me feel good," he added.

After WastePlan calculated a $50 per ton cost for a composting facility, Meg Morris turned to the Eastern Rensselaer authority's financial advisor for a second opinion. Independently, he estimated $46 per ton. "So we were relatively close," said Morris.

But in many cases, reality-checks just are not available--or will not be for many years. "When you try to force it one way or the other," said Anex, "push it up to a 50 percent diversion rate, for example, there's no way to test that because the city hasn't operated at that point." Nonetheless, model users say, programs like WastePlan provide decision-makers with the "best guesses" available, acknowledging that some margin of error is inevitable.

"We never put any claims that these were the most accurate figures you could get," said Redmond of her collection cost estimates for Columbus. "It was just the best data that the [city] had at the time." She believes that the "cost differentials" between scenarios were valid decision-making guides, even though she "would not want to develop a first year operating budget" based on these numbers.

Accurate Input Data Important

Getting accurate baseline waste stream data and cost figures--a prerequisite to calculating reliable recovery and cost estimates--can be a daunting task. Existing characterization studies may lack scientific rigor or fail to categorize materials in a useful way. Lacking hard numbers to put into the models, planners are forced to do a good deal of preliminary data gathering.

To track down yard waste quantities, Meg Morris ended up quizzing a local farmer on how many truckloads of leaves he thought were delivered to his farm. The New York Department of Environmental Conservation (DEC), which holds the statewide license for WastePlan, helped the authority set up the model.

"With Meg we probably sat down for a dozen all-day sessions where we collectively brain-stormed the information that went in," said Jim Close, a solid waste management specialist with the DEC, which sent two staff people to Morris's office in Stephentown, New York. Even so, they were not able to come up with firm numbers on the size of the commercial waste stream. The percentage they used--20 percent--was a "ballpark" figure.

Jim Close thinks that the chore of data entry and the sheer size of WastePlan--it contains dozens of input and output screens--may explain why so few of the governments supplied with the program have used it. Though about 100 solid waste managers received training in WastePlan and took home copies of the software, Close knows of only two communities--Eastern Rensselaer and Schenectady County--that have done extensive planning with the program. Local solid waste officials, he said, "frequently don't have time to sit down and fuss with the model when they're constantly dealing with running the landfill and there's too many other things on their plate." In Michigan, a university study found that very few of the 100-plus Michigan localities supplied with WastePlan were using it. A third of governments said they never even bothered to turn the program on.

To ease the burden of data entry, WastePlan and other models can be loaded with "default data"--such as national averages on waste composition and standard cost estimates--enabling the program to run even when local numbers don't exist or the planner doesn't have time to get them. But relying extensively on default data can comprise the validity of the results. After all, the model should represent the community being studied, not Anytown USA. The default figures are just a "place holder," said Paul Ligon, a research associate at the Tellus Institute who oversees WastePlan installations. Good local data should be plugged in if available, but the user is not faced with filling in every blank before trying out a scenario. To jump start users on the data entry process, Tellus conducts training sessions.

Still, WastePlan can be a big project for a small-town waste manager with limited resources. New York later encouraged Tellus to create an easier-to-use version of WastePlan, which Tellus now markets as "WastePlan Basic." (Jim Close calls it the "EZ Form.") The simpler version designed for New York also comes loaded with reporting forms that the state requires local governments to send in each year. Rather than "doing a lot of head scratching," New York's Close said, "planning units can now use WastePlan to generate these forms." Close called the form feature a "carrot" to get people to try out the program.

Other modeling programs combat model fatigue through an attractive user interface. The SWAP model, for example, has a graphical interface that lets the user build a model by moving icons around with a mouse and connecting them. "Instead of typing in a lot of equations, you just build a picture," said Robert Anex, the UC Davis researcher who has worked with several solid waste planning models. Anex helped develop the university's GIGO model, which is built around the popular Excel spreadsheet program. This gives the program a feel that Anex thinks should appeal to those users already familiar with spreadsheet software.

Computer or Consultant?

Of course, no model can be expected to run itself. Like any new piece of equipment, a good planning model requires a reasonable investment of time and manpower. But the question many ask is, why not just hire a good consultant instead?

Model fans answer that a good computer program, on balance, is simply a better deal. "I think you spend almost as much time doing the planning Ion the computer model] as you do monitoring the consultants," said Jeff Edwards, a planner with Schenectady County, New York. The county hired consultants last year to develop a solid waste management plan, but is not using consultants now.

Tom Osdoba, the Minnesota solid waste official, envisions the state, armed with WastePlan, teaming up with local governments on regional planning projects. Since Minnesota's model is already loaded with local waste statistics, Osdoba thinks the partnership would be hard to beat. "This is a perfect opportunity for them to save some money," he said. "We can work with them on this stuff and probably do it in a quarter of the time and the results will be as good or better because we're directly involved and they're directly involved."

Computer models are also viewed as a means of tightening the decision-making loop between local politicians and the government planning staff. "If you had WastePlan, you could allow the plan to be policy maker driven," said Schenectady's Edwards. "You can go back to the policy makers and say, well, this is what we came up with, what assumptions do you want me to make that are different from what I'm making?" Plus, said Edwards, "you're doing it in-house so you know where everything's coming from." According to Paul Ligon, one of the original purposes of creating the software was to "empower local solid waste officials so they could be less dependent on consultants."

But can computer models in fact "stand in" for a seasoned consultant? "That's patently ridiculous," said Robert Anex. "You're not going to get an expert in a box. The world is so idiosyncratic and the thing isn't an expert system--and even if it were, it wouldn't be as bright as a good consultant." Nonetheless, Anex thinks cities and counties could use computer models instead of consultants for some projects, such as rate setting. "Every year they pay these guys $50,000," said Anex. "If they get themselves up on a model, it may cost more initially, but they don't have same recurring cost."

The cost of getting up and running on a computer model depends, in part, on which model you use--and who is footing the bill. Tellus charges $1,500 for a bare-bones "single-site" copy of WastePlan. Statewide licenses, sold for $10,000, let up to 100 users within a state install the program. Extra training and customization cost more: Minnesota spent about $50,000 for a single site license, extra training, and extensive model customization. New York's contract with Tellus, which included training, software support, and enhancements, totaled $140,000.

Other programs, however, are available at little or no cost. UC Davis hopes to see GIGO distributed freely, even to private consultants. Eastman Chemical's MUNI program has been available at no charge for several years, though David Cornell says the zero price tag might have actually dampened the public's demand for his model. "I frankly think it's like a free steak," he says, "if you don't pay money for it, you don't appreciate it."

Another issue facing model users is how to get help when they are stuck. Availability of technical support is an important consideration in deciding whether to launch into the world of computer modeling.

The Tellus Institute provides four hours of free assistance with each WastePlan license, and states have tried to offer local governments additional help by underwriting training sessions and other support. In Michigan, the cooperative extension service ran a hot line for two years to help county WastePlan users. New York wants to provide more hands-on assistance to communities like Eastern Rensselaer and Schenectady, but is limited now to just mailing out the program disks and manuals. "If we had all kinds of time and manpower, we might get involved in going out to the individual planning units," says Jim Close. In California, the completion of the GIGO model--now in its final stages of development--is dependent on the continued flow of grant money.

The best bet, of course, is to have a model enthusiast on staff, a person like Morris, Edwards, or Redmond, who can stick out the learning curve, power through the data input, and--crucially--carefully read the program's voluminous output.

A WastePlan planning project can generate reams of computer printouts--40 or 50 pages of tables and statistics are not uncommon from a modeling session. Interpreting the results judiciously--and formulating sound policy directives from them--is probably the trickiest part of a modeling project. And while the program can help in fleshing out dozens of options, it cannot guarantee that any of them will be funded.

In Columbus, of the 60-plus scenarios generated by WastePlan, none were acceptable to the city's policy makers. "They made the decision that all the alternatives were too expensive," said Tina Redmond, noting that the cheapest recycling scenario was expected to cost the city about $25 per household per year. Instead of funding a recycling service, the city now asks residents to make independent arrangements with private recyclers. A small pilot curbside recycling program funded by the city has since been shut down.

"We can't hardwire that recycling comes out cost-effective, regardless of our politics," says the Tellus Institute's Paul Ligon. However, he points to a WastePlan study of the New York City region in which a combination of recycling and "waste prevention" programs was projected to reduce the per-ton cost of managing waste over 20 years.

Prognostications far into the future, of course, should be taken with a grain of salt. Today more than ever, the job of planning large waste facilities and predicting waste flows is fraught with uncertainties. Increasingly, collection and disposal operations are run by private contractors seeking the best price and lowest costs, while government planners may be powerless to direct where garbage and recyclables go. While acknowledging this difficulty, Paul Ligon thinks that WastePlan could at least be used to keep private contractors honest. Government waste managers, he says, could go to their contractors for efficiency and other data, plug the information into WastePlan, and then determine if the community is getting its money's worth.

Down the road, computer-aided waste planning, in one form or another, is probably here to stay. Already computer programs are widely used for routine waste management tasks such as truck scheduling, scale-house record keeping, account billing, and program budgeting. Computer simulation of the fully integrated system is likely to attract a growing base of PC-literate solid waste managers. And. for computer types, booting up a solid waste simulation program is the next best thing to being there. "Frankly, I enjoy working with computers," says Jeff Edwards. "I have a slant that says this would be a fun way to do planning."

Mr. Bracken is an independent waste consultant based in San Francisco.
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Author:Bracken, Robert
Publication:Public Works
Date:Aug 1, 1994
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