October 2008

The Characteristics of Waste Studies

As with any survey, the more samples the greater the confidence level in the final product.

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The noted garbologist William Rathje wrote a story about a study involving a dietary survey of people who lived in a retirement community located in Arizona. As with any Neilson-type survey, researchers provided the members of the community with a diary to log all food and beverage consumed within a specific time period. The researchers, however, took the added step of taking the garbage generated at homes of these survey subjects during that same time frame and segregated, weighed, and logged all categories. When the researchers compared the diaries with the results of the waste characterization, they found that the survey subjects had drastically underestimated the amount of alcohol consumed and seriously overestimated the amount of vegetables eaten. Here was a case where the characterization of the waste from these survey subjects acted as a check and balance to the subjective traits of human nature. There is an objective quality to the makeup of trash that speaks volumes to the social habits of waste generators. The best solid waste employees, whether formally educated or not, tend to be self-taught sociologists estimating the social traits of their customers.

Waste characterization studies define the composition of a wastestream and tell us what type of items we discard. These studies can take a bead on specific waste generation events, such as a music concert, or all that is generated in a specific geographic area known, by some, as “waste sheds.” The items studied can range from the delicate to the indestructible, from the ugly grime of the indeterminable to such precious bounty as aluminum. These studies are what we make of them—to be used, hopefully, for the better management of waste or, unfortunately, to sit upon a shelf as a memento to an unfulfilled hope used sparingly as a statistical resource when answering questions from the public, the press, or a political body.

Professionals in the field of waste characterization may start at one of two conceptual methodological ends and ease toward the center, depending upon the size, complexity, and funding available to complete the objective. At one end of the scale, a modeling strategy sits that extrapolates the details of a wastestream from broad economic indicators and manufacturing statistics to estimate waste generation for a specific jurisdiction. The EPA and its consultant, Franklin Associates, call this method a “materials flow methodology” that uses “data gathered from industry associations, key businesses . . . and supported by governmental data from sources such as the Department of Commerce and the US Census Bureau.” The flow of goods, allowing for adjustments in imports and exports, is estimated, as is the life expectancy of such goods. These variables are calculated so as to take a broad swipe of the brush upon the national canvas of waste, defining an order of magnitude. This “top-down” view of waste generation and flow has its roots with the Public Health Service and its successor, the EPA’s Office of Solid Waste (Municipal Solid Waste In The United States: 2005 Facts And Figures, Environmental Protection Agency, pages 2 and 23).

Waste characterization studies define the content of the wastestream.

On the other end of the methodological scale, men and women in Tyvek suits wearing latex gloves and breathing through respirators spend their time sifting among 200- to 200-pound sections from truckloads of trash, filling buckets of predetermined categories, weighing them, and carefully inputting the data for further statistical analysis. This method builds a picture of the wastestream a pixel at a time so that the image ultimately drawn has a defined and supported definition to its shape that will instill a high level of confidence in the picture the numbers paint. This “bottom-up” approach consumes more time and labor than the “top-down” methodology.

The city of Seattle has been doing the bottom-up methodological approach since 1988 on three substreams: commercial, residential, and self-haul. Table 1 is taken from the city’s 2006 “Residential Waste Stream” study done with the assistance of Cascadia Consulting Group Inc. The table shows the number of samples for each of the waste characterization studies of the three substreams of waste. The Seattle Public Utilities, the agency overseeing these studies, has maintained a strong commitment to this activity since 1988.

However, not all solid waste managers may be employed by an agency or jurisdiction that has either the commitment or the funds to support a waste characterization study with a high level of sampling. Financial pressures on governments appear to be increasing at an exponential rate, causing policymakers to look for creative ways to estimate the character of their waste.

The EPA’s data predict this very problem: “If resources are not available to adequately estimate these [waste] materials by other means,” the authors of the study write, “local planners may turn to the national data” (Municipal Solid Waste In The United States: 2005 Facts and Figures, page 21). The authors do point out, however, that this would only be a ballpark estimate that would not take into account climate variation, scope of the wastestream of individual facilities, cultural and economic differences in purchase and disposal practices, commercial activity, and local and state regulations that may influence the wastestream.

Less-intensive options, therefore less costly, can be used to estimate the composition of a wastestream without hand sorting. These include the review of similar studies, as well as direct inquiry and observation.

Don’t reinvent the wheel—Other communities have performed waste characterization studies that could possibly be used to provide an estimate of a different jurisdiction’s waste-stream. Parameters of the other study and its location must be carefully reviewed to ensure that one is comparing similar situations. First, the correct substream must be reviewed. If a solid waste manager is looking to find out the type of material single-family units are generating, for instance, then a waste characterization study of commercial waste will not help. Second, the jurisdiction that performed the study may have advanced recycling programs that divert considerable material, such as greenwaste, or, for example, has a bottle bill that transfers plastic and glass bottles out of the disposal stream and into the recycled stream. Significant programs diverting recyclables out of the disposal stream will show considerable differences from a jurisdiction that does not have such programs or vice versa. Third, demographic and cultural differences can create variations in purchase and disposal habits. Large immigrant populations, for instance, may have different dietary habits that could contribute more or less foodwastes to the total waste shed. Fourth, climate conditions will affect the level of material in the wastestream in terms of greenwaste and in terms of potentially destructive natural forces. In other words, Fargo, SD, may not have the same level of greenwaste as Kauai, HI, or where tornadoes regularly spin through communities ripping trees and bushes out of the ground as if they were carrots in the garden.

Purists may argue that only hand-sorts should be used.

Look—If a community does not wish to expend the funds to systematically segregate and count the waste from a specific or multiple substreams, then one can estimate the material in loads at the disposal points by visually seeing them dumped and, if need be, spread out and estimated. Local public waste auditors, who go to businesses free of charge to help the commercial community lower its disposal costs and increase its diversion rate, have learned to do quick estimates of materials in dumpsters and items in the work place so as to provide projections to business owners on how to cut down on quantity disposed and divert more. This skill can be expanded to all generators. Getting out of the office to look at the flow of materials with an eye toward counting the number of trucks and estimating percentage of material in a load can provide an order of magnitude that would be helpful in judging the effectiveness of potential waste management programs.

Ask—The local waste market, if not the national one, is made up of a close-knit group of individuals who make it their business to know market share. Asking the owners and mangers of hauling, disposal, and processing operations what is done with the material generated in the jurisdiction will unravel a plethora of threads that need to be followed. Some of these threads will represent nothing more than a strategy of misdirection, some will end in a tangled web making a Los Angeles freeway interchange look rational, but others will lead to unknown processors, to non-permitted disposal and processing facilities, to back-haul operations, and to once-unknown pilot programs handling a portion of the waste. Telephone surveys of waste receivers and generators can provide tonnage data that will help to build a more complete picture of a jurisdiction’s waste flow. Asking questions can lead to interesting discoveries about the flow of waste.

States Help
States have attempted to assist localities with waste characterization studies. In 1988, for instance, the State of Florida passed a solid waste management act setting 30% as its recycling goal. The state provided up to $20 million a year to help localities meet this goal and required all of its 67 counties to perform waste characterization studies in order to develop a baseline for meeting the recycling goal. The faucet that funded these individual waste characterizations was wrenched shut, but in 2001 the State of Florida Department of Environmental Protection gave an Innovative Recycling Grant to Pinellas County, which partnered with several other jurisdictions. Together they hired the services of Franklin Associates and Kessler Consulting to create a waste calculator built upon a merging of a materials flow methodology, top-down, and hand-sorts, bottom-up, held in four of the participating counties and 10 other Florida samplings that had already been performed.

A Florida county waste manager can go to and follow the simple instructions to input demographic, recycling, and total tonnage information and get, in return, a waste characterization for that county (www.dep.state.fl.us/wastecalc/fdepcountydata.asp)

At one end of the methodoligical scale, men and women in Tyvek suits sift through trash, filing buckets with predetermined categories.

Georgia’s Department of Community Affairs also recognized, and says on its Web site, that “[t]he cost and level of resources associated with conducting these [waste characterization] studies are prohibitive for many counties.” This state office hired R.W. Beck to develop a waste composition computer model for local waste managers to utilize (www.gasolidwaste.org/GADCAWebCalc/index.aspx).

As with so many things waste-related, the California Integrated Waste Management Board (CIWMB) provides a fairly comprehensive Web site for waste characterization data. Along with the CIWMB’s waste characterization database, the site includes six pages and links to more information describing protocols for sampling at landfills and where the waste is generated.

In 1999, the CIWMB spent $635,700 for a waste characterization study, followed by $316,650 for another in 2003. The second study was less expensive, in part, because the CIWMB opted not to hand-sort at the site of the commercial generator of waste. It chose to do the sorting at the disposal site. Each study focused on three generators: commercial, residential, and self-haul. The results are shown in Table 2, as taken from the CIWMB’s “Update of California Waste Characterization Data” December 2004.

The CIWMB is currently performing another waste characterization study to update and compare with those done previously.

Local Jurisdictions: Seattle
Since 1988, Seattle’s Public Utilities has performed consistent waste characterization studies using the bottom-up methodology. It follows a four-step process.

Step 1 is that of developing a sampling plan dedicating two-thirds of the sampling to residential single-family waste and one-third to multifamily waste. A schedule of sampling was developed for the calendar year. During each month there would be two or three consecutive days of sampling randomly chosen.

Step 2 entails the random selection of vehicle routes from each of the areas to be sampled. The hauling contractor would be called on the day of sampling to have a randomly chosen truck deliver material to the sampling location.

Next, the collection vehicle chosen goes to the sampling location and is verified as being the correct truck from the correct route. The material is unloaded onto the floor and about 250 pounds is separated out into 83 component categories.

Finally, field researchers build the information into a database and aggregate the sampling using annual waste tonnages to divine the waste characterization of the targeted wastestream.

Tables 3 and 4 show the changes in waste characterization of residential disposed over time in the city of Seattle. The city decided to ban recyclable items, such as fiber, from the wastestream, based in part on the findings of these waste characterization studies.

Seattle also broke down its study to show the disposal habits of single-family as well as multifamily dwellings. Single-family units, the study found, produced a higher percentage of foodwaste than did multifamily dwellings. Single families also doubled the output of disposable diapers but newspapers made the top ten items disposed by residents of multifamily units only.

Seattle studied the waste coming from the commercial sector as well. It set up a sampling regime for loose rolloff trucks, compactor rolloff vehicles, rear-loaders, and front-loaders. The field researchers worked with the haulers to account for the type of generator so it could develop composition by generator types, such as educational institutions, health care facilities, hotels, manufacturing, offices, retail, transportation industry, wholesale, and mixed commercial generators. Tables 6 and 7 compare the results of aggregated percentages done in various years. Construction, demolition and land clearing dropped since the first study, as did paper, but organics have increased.

City and County of San Francisco
Whether it is simply the foreshadowing of expectations or fact, people see the city and county of San Francisco as pushing the proverbial envelope, whether it is in politics, in culture, or in trash. The jurisdiction’s relationship with its hauler, Norcal Waste Systems Inc., is unlike any other in the nation: The jurisdiction’s long-term disposal contract, based on total volume, creates a financial incentive for the jurisdiction to divert waste away from burial. The local culture and political institutions support the aggressive goals of 75% landfill diversion by 2010 and zero waste by 2020 that the San Francisco Department of the Environment has advocated.

Robert Haley, with the city’s department of the environment, uses “these characterization studies to design programs and policies.” Approximately every seven years, the department sponsors a study at the cost of about $150,000 for waste disposal characterizations and $75,000 for diversion characterizations. The most recent was released in March 2006 and uses a mixture of hand-sort sampling and visual characterization. Table 8 shows the number of samples from each waste sector utilizing each method.

The visual characterization method may sound hokey to those wearing pen protectors in their breast pockets, but systemizing this art into a skill through standard operating procedures can provide valuable information at a reduced cost. Field technicians would have the material dumped, spread out if needed, and volume estimates made. For instance: “If a 20-cubic-yard load appeared to hold 5 cubic yards of foodwaste and 15 cubic yards of prunings, then it was recorded as 25% food waste and 75% prunings. The differing densities of materials were taken into account in subsequent calculations, not during the actual observations” (San Francisco Department of the Environment, Waste Characterization Study: Final Report, March 2006, Appendix C: Waste Sampling and Methodology, page C-6).  If materials were in opaque bags, the bags were then opened and the contents spread out so they could be seen.

An interesting aspect of San Francisco’s waste study is its unflinching look at city operations. Whether intended or not, waste characterization studies do not regularly underscore waste from specific operations, especially if those activities do not have waste management as their primary duty. Yet, the shining city by the bay does not mitigate when it comes to its own jurisdiction’s operations. It shows, for instance, that the housing authority disposes of trash made up of 19% old corrugated containers and kraft bags and another 14% from prunings. Thirty-one percent of the loads leaving the Muni Yard, for instance, have low-grade paper, with another 20% made up of old corrugated containers and kraft. This pinpoint characterization can help to implement in-house recycling programs.

Policy Makers and Waste Characterization Studies
Rathje’s story of using waste characterization as a check on human nature is important in this sense: The characterization of specific wastestreams can be used to check and balance the effectiveness of programs, policies, and educational outreach. These studies can provide tangible, not anecdotal, evidence to the effectiveness of those activities funded with increasingly limited public resources. Yet, the studies can be done, as San Francisco has shown, by using multiple techniques to help keep the costs low and still provide valuable information.

Purists may argue that only hand-sorts should be used in these studies, whereas others will debate the value of the resources expended for the benefits gained. The battle between the ideal and the contingent is as old as the debates between Plato, the teacher of the ideal, and Aristotle, the pesky student who continually reminded his teacher of everyday human contingencies. The debate will always be there, and solid waste managers must weigh the benefits versus the costs when contemplating the strategies to perform a waste characterization study.

Charlie Scott has been doing waste characterizations for decades and is widely respected by both his competitors and clients across the country. He advises policymakers to think through the purpose of these studies before enacting them and to ask themselves the following questions:

• What are the study’s objectives? Is the success of a program being measured or are potential programs being discovered?
• Are there going to be decisions based on such a study? Will facilities, for instance, be built based on the findings?

The answers to these questions bring to the fore the level of confidence a policy maker needs to have in the data. The greater the need for confidence in the numbers the more precise the study needs to be. Many of the reports that stay closed and on the shelf are those where the goals were not defined ahead of time.

Scott also believes that waste managers hinder the project when they stipulate, in the request for proposals (RFP), the precise methodology to be followed. Sometimes, he says, the RFP will go so far as to state the number of samples to be performed. This, he correctly says, squelches possible innovative techniques that would otherwise be proposed for achieving the objective of the waste characterization while reducing costs. Such RFPs, Scott believes, should break out, not jail in, ideas of how best to reach the clear objectives of the waste characterization study.

Author's Bio: Writer Chace Anderson is also vice president of Gershman, Brickner & Bratton Inc.