The Landfill Disposal Rates of Waste-to-Energy and Zero-Waste Communities
A municipal solid waste (MSW) management strategy that is growing in popularity is that of “zero waste.” According to the Grass Roots Recycling Network:
“Zero waste is a philosophy and a design principle for the 21st century. It includes ‘recycling’ but goes beyond recycling by taking a ‘whole system’ approach to the vast flow of resources and waste through human society. Zero waste maximizes recycling, minimizes waste, reduces consumption, and ensures that products are made to be reused, repaired, or recycled back into nature or the marketplace.”
Communities that embrace the zero waste philosophy typically rely on materials recycling, food and yardwaste composting, and composting or anaerobic digestion of mixed waste to achieve high rates of recycling and waste diversion. A key aspect of the zero waste philosophy appears to be the outright rejection of waste-to-energy (WTE) as a possible system component. For example, the city of San Francisco—a city that has embraced the zero waste philosophy—states on its web site:
“Imagine a world in which nothing goes to the landfills or incinerators. We think it’s achievable, and SF Environment is doing everything we can to make it happen in the residential, business and city government sectors, and at special events held throughout the city. Today, San Francisco recovers 72% of the materials it discards, bringing the city ever closer to its twin goals of 75% landfill diversion by 2010, and bringing the city to zero waste by 2020.”
In the past, the WTE industry has conducted numerous studies to document the fact that WTE communities achieve recycling rates that are comparable to or higher than those achieved by communities with robust recycling programs. However, the landfill disposal rates of WTE communities and communities with zero waste programs have, to date, not been documented.
This article presents highlights from a research report developed with input and guidance provided by the SWANA Applied Research Foundation (ARF) FY 2010 WTE Group Subscribers. A major outcome of the research was the development of a new metric, the landfill disposal index, which can be used as a performance measure for solid waste system options, including WTE-based systems and zero-waste systems.
Five organizations subscribed to the SWANA ARF’s WTE group in FY2010, each of which made a funding commitment to the conduct of collective applied research in the WTE area. (If the jurisdiction or organization was already an ARF subscriber and had made a penny-per-ton funding commitment to another group, the funding rate for the WTE group was reduced to $0.005 per ton.) A listing of the five WTE Group subscribers and their contacts are provided in Table 1.
The Landfill Disposal Index
In a presentation given at the “Cispel Confservizi Toscana Symposium” in Florence, Italy, in 2009, Dr. Nicholas Themelis of Columbia University’s WTE Research and Technology Council stated that “Waste management performance should be based on “tons landfilled” per capita (i.e. the fewer tons landfilled per capita the more sustainable the solid waste system.” (Themelis, N. “Materials and Energy Recovery in the US: New York and California,” Cispel Confservizi Toscana Symposium, Florence, Italy. April 24, 2009.)
Based on this recommendation, as well as research conducted during the FY2010 project, a new metric, the landfill disposal index, has been proposed by the ARF’s WTE Group for adoption by the solid waste industry.
The landfill disposal index, or LDI, is defined as the quantity of solid waste generated in a community that is disposed in landfills. The LDI should be reported on an annual weight per capita basis, such as tons of solid waste landfilled per person per year.
As shown in Table 2, an LDI can be calculated for each type of solid waste generated by a community. For example, a typical community is likely to have a municipal solid waste LDI (MSW-LDI) and a construction-and-demolition waste LDI (C&D-LDI). LDIs can also be calculated for the residential and commercial MSW substreams.
The LDIs presented in Table 2 are in line with, but more defined than, the waste reduction and recycling goal parameters established in many states. For example, the state of North Carolina has a waste reduction/recycling goal of 40% of the FY1991 per capita disposal rates. This goal, however, does not distinguish between wastestreams (MSW or C&D) or substreams (residential or commercial). If LDI goals were established by state and local governments for each type of wastestream, it would likely result in a better understanding of the effectiveness of waste reduction and recycling programs targeted toward these wastestreams.
Finally, a “Biodegradable MSW-LDI” would indicate the quantity of MSW generated in a community that has been not been stabilized or biodegraded prior to or during landfill disposal.
The LDIs of WTE Communities
In June 2009, Dr. Eileen Berenyi published a report entitled Recycling and Waste-to-Energy: Are They Compatible? 2009 Update. This report provides solid waste data for communities with WTE facilities, including populations served, tons recycled, and tons disposed in landfills or at WTE facilities.
Dr. Berenyi’s firm (Governmental Advisory Associates Inc.) also publishes the Waste-to-Energy yearbook. In response to a request from the ARF’s WTE Group, Dr. Berenyi provided unpublished data on the actual MSW tonnages processed at United States WTE facilities. Data from these two sources, as well as from the city and the county of Honolulu, were used to calculate the LDIs for 66 WTE communities with the results presented in Table 3.
As shown, communities with WTE facilities dispose of 25%, on average, of the MSW they generate in landfills. Of the remaining 75% of the MSW generated, 33% is recycled and 42% is combusted to generate electricity or produce other useful energy products. The average MSW-LDI for the estimated 37.2 million people served by these WTE facilities is 0.35 of a ton per person per year.
Waste stabilization has long been recognized as an important process in the treatment of certain wastes, such as wastewater treatment plant sludges. The European Commission (EC) recognized the importance of solid waste stabilization in the promulgation of its 1999 landfill directive, which requires member states to reduce the amount of biodegradable waste landfilled to 35% of 1995 levels by 2016. Many member states are implementing WTE facilities to meet the requirements of the directive.
An implicit and reasonable assumption in this approach is that the ash generated by the WTE systems in these communities has been stabilized through the combustion process and is, therefore, non-biodegradable.
The biodegradable MSW-LDI for the 66 WTE communities included in Table 3 can be calculated by dividing the tonnages of “Bypass MSW” by the populations served. The resulting Biodegradable MSW-LDI is 0.21 of a ton per person per year, which equates to 15% of the waste generated in the WTE communities. Therefore, it appears that these communities would comply with the EC landfill directive if a similar policy was adopted in the US.
MSW-LDIs for Zero Waste Communities
Due to the newness of the zero-waste approach, the calculation of MSW-LDIs for zero-waste communities is based on very limited data from communities that have not yet implemented all of their planned zero-waste initiatives. With this understanding, data for two cities that are nationally known for their aggressive recycling programs and/or zero waste plans—San Francisco and Seattle—are presented in Table 4 for consideration.
As shown, in 2008, the city of San Francisco disposed of 594,600 tons of waste that were generated within its jurisdictional limits. In light of its 2008 population of 808,976 and assuming (based on the CalRecycle jurisdiction profile for San Francisco) that 93% of the waste disposed in 2008 was MSW, this equates to an MSW-LDI of 0.68 tons per person per year.
Similarly, in 2009, 351,688 tons of MSW from the city of Seattle were disposed in landfills. This amount was substantially lower than the 439,542 tons disposed in 2007, with the decrease in tonnage presumably due to the economic recession. Even at the low 2009 disposal rate, the city of Seattle had an MSW-LDI of 0.58 tons per person per year.
While this preliminary analysis of the MSW-LDIs of zero waste communities is based on only two communities that have not yet implemented all of their planned zero-waste initiatives, it indicates that significantly lower MSW-LDIs have been achieved by communities with WTE systems—0.35 tons per person per year—when compared with those that are currently being achieved by communities implementing zero-waste systems: 0.58–0.68 tons per person per year. Furthermore, as the WTE systems that are included in Table 3 have typically been in place for 20 years or more, it can be concluded that these communities have been achieving these low MSW-LDIs for many years.
The analysis also indicates that zero-waste communities might not be diverting as much waste from landfill disposal as is indicated by their reported diversion rates. For example, the city of San Francisco reports that it is currently diverting 72% of its waste from landfill disposal. This high diversion rate is difficult to understand in light of the city’s MSW-LDI of 0.68 tons per person per year. In comparison, the documented average MSW diversion rate for the 65 WTE communities in Table 3 is 75%, while the MSW-LDI for these communities averages 0.35 tons per person per year.
This article describes a new metric—the landfill disposal index (LDI)—that can be used to measure the performance of waste management systems. The LDI indicates the amount of waste generated in a community that is landfilled each year on a per capita basis and is reported as “tons landfilled per person per year.”
Based on published and unpublished data from reliable industry sources, the average MSW-LDI for 66 communities that have implemented WTE systems that serve over 37 million people is 0.35 ton per person for year. In addition, the biodegradable MSW-LDI of these communities averages 0.21 ton per person per year, which equates to 15% of the MSW generated.
In comparison, the MSW-LDIs for two communities (San Francisco and Seattle) that have implemented aggressive waste reduction and recycling programs range from 0.58 to 0.68 tons per person per year. These MSW-LDIs are substantially higher than the MSW-LDI of communities with WTE systems and indicate that these communities might not be diverting as much waste from landfill disposal as indicated by their reported recycling/diversion rates.
The FY2010 WTE Group of the SWANA ARF recommends that the LDI be adopted by the solid waste industry as a useful metric to evaluate the performance of MSW management systems. Furthermore, the group recommends that an LDI be developed for each waste substream generated in a community (residential MSW, commercial MSW, C&D, etc.) so that the effectiveness of local waste reduction, recycling, and conversion programs that target these waste substreams can be more accurately measured.
Director for the City of Dallas Sanitation Services to Speak at Annual Landfill Gas Symposium
Mary Nix, P.E., director of sanitation services for the city of Dallas, will be the keynote speaker for SWANA’s 34th Annual Landfill Gas Symposium to be held March 21–24, 2011, in Dallas, Texas.
In her presentation, Nix will discuss the environmental management system used by the city to manage its municipal solid waste, as well as challenges the city has faced over the last decade and solutions that have been implemented to overcome these challenges.
Nix has more than 30 years of experience in the solid waste and environmental arena. As the director for the City of Dallas Sanitation Services Department, she currently manages the city of Dallas’s residential waste collection, recycling, transfer, and disposal—serving a population of 1.3 million. With an annual budget of $75 million and a staff of 750, her department provides competitively priced weekly collection of residential refuse and recycling, monthly bulk and heavy brush collection, operation of the state’s largest landfill, and the fostering of new and innovative ways to advance solid waste practices.
|Photo: Mary Nix
The Landfill Gas Symposium is the leading forum on landfill gas utilization and technology, taking an in-depth look at beneficial use, methane offset projects, available tax and carbon credits, greenhouse gas issues, and legislative and regulatory developments. The event begins on Monday, March 21, 2010, with training opportunities, division and advocacy meetings, and an opening reception. On Tuesday, educational sessions begin with Nix’s keynote address. Other highlights of the conference include the following:
- Ten technical sessions, featuring over 30 presentations
- Two-day landfill gas trade show
- Tour of the McCommas Bluff Landfill
- LFG and MOLO training courses
- Earn up to 30 SWANA CEUs
- Networking events, including a golf tournament
The symposium will be held at the Gaylord Texan, in Dallas, Texas, March 21–24, 2011. For more information, to view the program, or to register for this event, please visit www.lfg.swana.org.
Author's Bio: Jeremy K. O'Brien, P.E., is director of applied research for the Solid Waste Association of North America.
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