A Proposed Bioreactor Landfill Demonstration Project Final Draft: March 24, 1998 A Large-scale, Multi-year, Multi-organizational Project to Demonstrate the Mass Processing of Municipal Solid Waste in a "Bioreactor" Landfill with the Utilization of Stabilized Recovered Residuals
Florida Center For
Solid and Hazardous Waste Management Abstract A PROPOSED BIOREACTOR LANDFILL DEMONSTRATION PROJECT Each of Florida’s 14 million people generates over 9 pounds of municipal solid waste per day, for a yearly statewide total of over 24 million tons. Since the passage of the 1988 Solid Waste Management Act, recycling has grown dramatically and Florida has experienced a substantial decline in landfilling. In 1988, of the 15.8 million tons of MSW generated, 75 percent was landfilled, 21 percent was burned in waste-to-energy plants, and only 4 percent was recycled. In contrast, in 1996, of the 24 million tons of MSW generated, 42 percent was landfilled, 18 percent was burned in waste-to-energy plants, and 40 percent was recycled. However, the per capita MSW generation rate and the state’s population both continue to grow. Because of these growth factors, coupled with stalled growth in the waste-to-energy sector and only modest anticipated improvements in the recycling rate, the total tons of waste landfilled will continue to rise and, in fact, will surpass the amount landfilled in 1988 in the near future. To move Florida into the twenty-first century in solid waste management, further reductions in landfilling are needed. One promising approach is the mass processing of municipal solid waste in "bioreactor" landfills. Under this model, landfills become "bioreactor" processing facilities where the waste is actively digested, rather than "dry tombs" where the waste decomposes slowly, if at all. Using this approach, the life of landfills can be greatly extended, perhaps indefinitely. The proposed project will develop and demonstrate a scaled-up, fully instrumented landfill cell, engineered from the start as a bioreactor facility. The project would be constructed at the New River Solid Waste Authority landfill (New River is a joint program of Baker, Union and Bradford Counties), with related work conducted at the Sumter County Solid Waste Facility. The project would be operated over a period of five years by the Florida Center for Solid and Hazardous Waste Management, a Type I Center of the Board of Regents comprised of nine Florida universities, in collaboration with state and federal agencies and local government. A Fixed Capital Outlay budget of $3.2 million is proposed for the design, construction, operation, and evaluation of a bioreactor landfill and related project components. I. PROBLEM STATEMENT: Landfills Are Not Going Away Each of Florida’s 14 million people generates 9.2 pounds of municipal solid waste (MSW) per day, for a yearly total of approximately 24 million tons. Since the passage of the 1988 Solid Waste Management Act, recycling has increased dramatically and Florida has achieved a substantial decline in landfilling. In 1988, of the 15.8 million tons of MSW generated, 75 percent (11.9 million tons) was landfilled, 21 percent (3.3 million tons) was combusted, and 4 percent (0.6 million tons) was recycled. In contrast, in 1996, of the 23.8 million tons of MSW generated, 42 percent (10 million tons) was landfilled, 18 percent (4.1 million tons) was combusted, and 40 percent (9.7 million tons) was recycled. On a per capita per year basis, the amount landfilled decreased from 1,960 pounds (1988) to 1,340 pounds (1995) [Note: the data used in this report is taken from reports submitted annually to the Florida Department of Environmental Protection by the state’s 67 counties, and published annually by FDEP].
Within the past five years, Florida has developed an integrated, "three-legged " waste management strategy of recycling, waste-to-energy and landfills. This is illustrated in Figure 1: On a percentage basis, the state’s recycling and waste-to-energy efforts have substantially reduced the amount of solid waste being disposed of in landfills—from 75% in 1988 to 40% in 1996. However, because the state’s population continues to grow, and the per capita MSW generation rate—the amount of MSW each person generates per year--continues to increase, the total amount of waste generated increased from 15.8 million tons in 1988 to 24.7 million tons in 1996. Therefore, the actual reduction in total tons landfilled from 1988 to 1996—11.9 to 10.1 million tons--was only 1.8 million tons. In other words, Florida’s recycling and resource recovery efforts are just keeping ahead of increases in per capita generation and population growth. Moreover, based on future projections, the total tons of waste landfilled will continue to rise. This projected increase is due to four factors: stalled growth in the waste-to-energy sector; only modest further improvements in the recycling rate; the growth in per capita generation rate; and population growth. These factors are discussed more fully below. A. Stalled Growth In Waste-To-Energy
Waste-to-energy (WTE) capacity grew significantly in Florida during the period 1982 through 1995. This trend is shown in Figure 2. However, the future of WTE suffered a significant blow in 1994 with the United States Supreme Court’s Clarkstown decision, which ruled flow control unconstitutional. Flow control, which was enacted by the Florida Legislature as part of the Resource Recovery Act legislation of the 1970s, authorizes local governments to mandate the flow of MSW to specific resource recovery facilities, such as WTE plants, to ensure an adequate source of revenue to pay for the facilities. Flow control was considered essential to obtaining bonds to fund most of the WTE plants currently operating in Florida. The uncertainty at this point is whether any more new WTE plants will be built, or whether existing facilities expand, without flow control. The evidence in Florida is not clear. On the positive side, a private company without flow control built the Ridge Generating Station in Polk County (although this facility burns only wood waste and waste tires). And it appears that nearly all of the existing facilities will retrofit to comply with new Clean Air Act emission control requirements, although there has been some speculation that the Bay County facility may close rather than retrofit. On the negative side, there are no plans to expand the capacity of existing facilities, or build new plants. Moreover, as shown in Figure 2, the amount of waste burned at WTE plants has dropped significantly, from 5.3 million tons in 1995 to 4.1 million tons in 1996. The reasons for this drop are not completely clear, but reduction occurred, which across all the WTE plants in the state, may reflect the loss of flow control and the diversion of waste to less expensive landfills.
In brief current projections indicate that most of the current stock of WTE plants should continue to operate well into the next century. But given the loss of flow control, coupled with high costs and public fears of incineration, construction of any new WTE plants seems unlikely. As the Florida MSW stream continues to grow, and no new plants are built, WTE will continue to shrink as a total of the waste managed. B. Limited Potential For Growth In Recycling Further improvements in the recycling rate are possible, especially in the commercial and institutional sectors. However, given the current collection infrastructure, status of end-use markets, and citizen willingness to pay, recycling will likely not exceed 45-50% of the total amount of waste generated, and achieving that rate will probably not occur on a statewide basis until well into the next century. In the early years of the state recycling program (1989-1995), the program was growing at a rate of increase in the diversion rate of about 5% per year (that is, in 1988 the rate was about 5%; in 1989, it was 10%; in 1990, 15%, and so forth). However, now that the state has achieved a 40% recycling rate, further increases will be much more difficult to achieve. Stated another way, the "low hanging fruit" has been harvested, and additional increases in recycling rates will most likely be slow and incremental. Figure 3 shows the growth in tons of materials recycled and recycling rate and illustrates this slowing trend. C. Rising Per capita MSW Generation Rate The per capita generation rate, along with population growth, determines how much MSW will be generated in future years. The assumptions range from no growth in the per capita generation rate to a continuation of the historic growth rate. Figure 4 shows the historical growth in the per capita generation rate, and includes a trend line projection to the year 2010. D. Continued Population Growth The FDEP June 1997 Solid Waste Annual Report cites the Executive Office of the Governor, Office of Planning and Budgeting, which estimates the Florida’s population will be between a low of 17.5 and a high of 23 million people by 2020. The annual percentage growth rates for these two projections are 0.86% (low) and 1.95% (high). A mid-range growth rate of 1.4% can be estimated by averaging the low and high rates. E. Estimating Future Landfilling Estimates of how much MSW will be landfilled in future years can be made by varying the assumptions made about the four factors discussed above—future WTE capacity; the recycling rate; and the growth, or lack thereof, in per capita generation rate and the growth rate in population. Literally dozens of combinations of these variables are possible, but three cases seem the most likely. These three cases are described below. For all three cases, the population rate is assumed to be the mid-range projection, which is a growth rate of about 1.4% per year. With regard to projections of future WTE use, the total MSW burned in WTE plants in 1995 was 5.3 million tons, while the amount reported to have been burned in 1996 was only 4.1 million tons. Therefore, an average of the two years of 4.7 million tons per year is assumed throughout the period. Two recycling rates are evaluated: Case I assumes that the statewide recycling rate for 1996 of 40% is sustained throughout the period. Case II assumes the recycling rate rises to 45% and is sustained at that level throughout the period. Finally, Case III maintains a 45% recycling rate, but increases the per capita generation rate to the projected historical rate (shown in Figure 4). Case I
Case II
Case III
Graphs of the three cases are shown in Figures 5-7. For all three graphs, the data shown for the period 1988-1996 is historic data that is reported annually to FDEP, while that from 1997 forward is projected. F. Comparison To Amount Of MSW Landfilled In 1988 In 1988, a population of 12.1 million people generated nearly 16 million tons of MSW, of which 11.9 million tons were landfilled. In Case I, Florida will be landfilling as much MSW in 2006 as it was in 1988, the year the Solid Waste Management Act was passed. In Case II, with the recycling rate increased to 45%, this doesn’t occur until 2012. However, Case III, demonstrates that even if the recycling rate is sustained at 45%, if the per capita generation rate continues at its historic rate, then Florida will be landfilling as much MSW in 2002 as it did in 1988. By varying the assumptions, one can move this declination point forward or backward in time. However, it seems likely, based on the cases analyzed, that within the next five to ten years, Florida will be back where it started from in 1988, in terms of the amount of MSW landfilled.
G. Landfill Siting Difficulties While modern landfills with composite or double liners are safe, they are still problematic, most notably when it comes to siting a new facility. Because of strong public opposition, siting new landfills has become very difficult. And, while solid waste management is clearly a responsibility of local government, the problems associated with siting new facilities quickly become state problems. An historical case in point is the proposed Southeast Landfill, which Duval County sought to build in the late 1980’s. The siting became a bitter state fight. Before it was all over, the conflict involved Duval and St. Johns counties, the Department of Environmental Regulation, the St. Johns River Water Management District, the Department of Community Affairs, and the Governor and Cabinet, not to mention dozens of lawyers and consultants. An estimated $15 to $20 million was spent by the parties involved. More recently, a similar war was fought in Alachua County. After a five-year battle with neighborhood groups opposed to the proposed site, the County Commission threw up its hands and decided to ship its garbage to a landfill in another county. And last year, in Gilchrist County, a proposal by a private waste management company to build a large, regional landfill resulted in such public outcry that the county was forced to hold a public meeting on the proposal in the local high school football stadium, the only local facility large enough to hold the crowd. Fifteen hundred people showed up to oppose the site. While solid waste management remains a local government responsibility, clearly the state has a role in working to resolve conflicting pressure from the public to curtail new landfill siting and impending demand for more landfill space. The following proposal lays out a plan to demonstrate a landfill technology that will help to mediate these competing demands and to respond to the need for an acceptable alternative to conventional landfills. II. PROPOSAL: Transforming Landfills From Dry Tombs to Bioreactors To move Florida into the twenty-first century in solid waste management and deal with the increasing fraction of waste going to landfills, the state must try to develop a new strategy to optimize the use of existing landfills and prolong the life of any new ones. One promising approach is through the mass processing of municipal solid waste in "bioreactor" landfills. In a bioreactor landfill, the waste actively decomposes rather being simply buried in a "dry tomb." This active decomposition is possible because over half the MSW waste stream is comprised of organic material (food, paper, etc.) which will decompose fairly rapidly under the right conditions. Under this model:
The primary objective of the proposed project is to design, construct, operate, monitor, and evaluate a bioreactor landfill cell. However, the project also includes support components addressing MSW composting, education, training, and other landfill research objectives discussed more fully below. The project would be directed by the Florida Center for Solid and Hazardous Waste Management (FCSHWM), a Type I Center created by the Legislature in 1988. The FCSHWM reports to the Board of Regents, and consists of nine participating Florida universities. The bioreactor landfill concept builds on research already completed by FCSHWM researchers, particularly leachate recirculation work conducted by University of Florida environmental engineering faculty and students at the Alachua County Southwest Landfill. If funded during the 1998 session of the Florida Legislature, the project would be initiated with a large national solid waste research conference in the Fall of 1998, sponsored by the FCSHWM, in collaboration with other solid waste centers around the country, such as those at Clemson University and the University of Wisconsin. The purpose of the conference would be to bring together the nation’s most knowledgeable university, government, and private sector researchers in landfill technology to fully explore the various components of the project. The components of the proposed project are described below. The bioreactor landfill cell itself would be constructed at the New River Solid Waste Authority landfill site in Union County. Additional testing and research in connection with maximizing the benefits of bioreactor landfill technology will be conducted at the Sumter County Solid Waste Facility, a MSW recycling and composting facility that includes the state’s only in-vessel compost digester system The proposed project is comprised of four primary components:
Each of these components, and the activities that will be conducted in connection with them, are presented in more detail in the following sections. A. Bioreactor Landfill Cell The operation of municipal solid waste landfills as bioreactors has been practiced to some extent at many landfills throughout the United States (Reinhart and Townsend, 1997). The level to which bioreactor landfill operation has been implemented, however, has most commonly been limited to some form of leachate recirculation. Thus, experience is minimal with regard to: (a) controlling or monitoring the treatment process occurring within the landfill, and (b) the impact of the leachate recirculation on the internal landfill system. In most cases, leachate recirculation has been practiced as a novel approach to managing leachate without much thought to using the landfill as a treatment system. Landfills utilizing leachate recirculation have typically not been designed specifically to operate as treatment systems. Full-scale implementation of bioreactor technology has not yet been demonstrated, and optimal design and operation methods for bioreactor landfill treatment systems have not been developed. This absence of operating models has limited the widespread use of this technology for waste management. A few studies have investigated areas of bioreactor landfill operation at the full-scale level beyond simple operation of leachate recirculation systems. One of the first systems was operated in Florida, at the Southwest Landfill in Alachua County. University of Florida researchers operated segments of the existing sanitary landfill as a bioreactor treatment system. However, the landfill was not designed with leachate recirculation in mind. A variety of leachate recirculation methods were employed (Townsend et al., 1995). Solid waste samples were collected from treated and untreated areas within the landfill, and the degree of waste treatment was measured (Miller et al., 1993). This research demonstrated that waste treatment was rapidly accelerated by leachate recirculation. In the Alachua County project, instrumentation was installed to control and monitor the waste treatment process. This instrumentation included temperature thermocouples placed within the waste to monitor the progress of treatment. No system was available, however, to measure the hydraulic characteristics of leachate movement within the landfill or the impact of leachate recirculation on leachate head on the liner. While leachate recirculation was successfully used to treat the landfilled waste, the fact that the landfill was not designed from the beginning to operate as a bioreactor left a number of areas unexplored. The experience gained, however, provided much information for the design of future full-scale bioreactor research. A small-scale, experimental bioreactor landfill system was recently constructed in Yolo County, California (Reinhart and Townsend, 1997). This facility was designed to carry out leachate recirculation, and instrumentation was installed to measure leachate head on the liner and landfill temperature. This landfill cannot accurately be characterized as full-scale, however, since it was constructed in an area of 100 ft. by 100 ft. The instrumentation is expected to provide valuable information about how to monitor treatment progress and the hydraulic influence in a bioreactor system. The results of this project should be considered preliminary, however, since clearly the circumstances encountered in a full-scale operation may differ drastically from those of small-scale pilot operations. The successful implementation of bioreactor technology requires that a full-scale operation be implemented in concert with an intensive research program to develop the tools necessary to design and operate such facilities, and to determine whether this is a feasible and attractive alternative for waste management. Important unanswered questions that this project will address include:
Other questions addressed by the proposed project relate to the impact and implementation of such technology at the operating landfill level, particularly under Florida rainfall and temperature conditions. The bioreactor landfill test cell proposed here will incorporate all facets of bioreactor landfill design and will employ monitoring technologies previously unused. The project’s key research areas are grouped in the following categories:
Leachate Monitoring and Control System Current landfill regulations require the construction of a liner and leachate collection system to prevent leachate from entering the environment. The bioreactor landfill design will include a double liner. The leachate collection system (LCS) will be divided into two distinct sections so leachate quality and flow can be monitored for two types of liner and leachate collection system designs. An important issue in connection with landfill operation is actual depth of leachate above the liner since this depth controls potential leakage through the liner. Engineers have developed landfill design methods based on head on the liner, but the true depth of leachate on the liner during operation can not be monitored in typical landfill designs. The proposed bioreactor landfill will be instrumented with pressure transducers on the liner surface that which will be used to measure the depth of leachate on the liner and to send signals back to a central data processing facility. A leachate monitoring system will be installed in all of the primary LCS lift stations to keep a constant check on the quality of leachate, especially as related to leachate recirculation and rainfall. The data collected from this monitoring system will help engineers better design and operate bioreactor landfill treatment systems. Leachate Recirculation System A distinctive feature of a bioreactor landfill system is the recirculation of leachate to the landfilled waste. The addition and movement of moisture to the interior of the landfill creates an environment in which naturally occurring microbes degrade the waste at a much greater rate than they normally would. Instead of landfilled waste presenting a potential environmental hazard for many decades into the future, the waste can be treated in a matter of years in the same manner as a compost system. But while bioreactor landfills operate on the same biological principles as compost systems, in-situ landfill treatment is much less expensive than waste treatment outside of the landfill. One of the greatest challenges to effective leachate recirculation design and operation is the difficulty of distributing moisture evenly throughout the landfill. Waste tends to be very heterogeneous, and, thus, moisture movement is not always uniform. The proposed bioreactor landfill will be instrumented with a series of moisture sensors to track the flow of leachate as a function of leachate recirculation. This data will enable engineers to better design and operate bioreactor landfill systems. Another question that remains to be answered is how should leachate recirculation systems be managed after closure. Under current regulations, leachate may not be recirculated after a landfill has been closed with an engineered landfill cap. The waste at closure may not be completely treated, however, and the leachate might benefit from continued recirculation. The bioreactor landfill will be constructed to monitor leachate quality and assess the potential benefits of post-closure recirculation. To answer these questions, in this project, leachate recirculation will be carried out by a combination of direct application and horizontal injection galleries. Sensors will be installed to track the movement of water in the landfill, and the landfill will be designed to continue to practice leachate recirculation after closure. Landfill Gas Control System The direct end product of waste degradation is landfill gas production. Thus, a bioreactor landfill, which has a rapidly stabilized waste, will also have rapidly enhanced gas production. This gas must be controlled for a number of reasons. Gas control is required to some extent under new federal regulations. Gas can also be used as a fuel source. Gas collection must be designed hand-in-hand with the leachate collection and recirculation systems. Although in most modern landfill designs, gas collection often is not practiced until after the landfill has closed, the proposed bioreactor landfill will institute gas recovery from the very beginning of landfill operation. Gas collection will be accomplished by constructing the leachate collection system to collect gas and through the use of horizontal pipe galleries within the landfill. A series of continuous recording gas meters will be installed at various locations throughout the landfill. Data will be collected by a central data processing system. After closure, the landfill will be capped in a manner that uses a horizontal gas collection layer under the cap, rather than the traditional method of vertical wells that penetrate the cap. The leachate collection system will be designed so that gas can be collected after the first complete lift of waste has been placed. Horizontal leachate injection pipes will be used to serve as gas collectors in the top layer of the landfill. The landfill cap will be constructed in a manner such that no wells penetrate the cap, but rather will employ a collection layer above the top layer of waste and below the cap. References Miller, Townsend, Earle, Lee and Reinhart (1994). "Leachate recycle and the augmentation of biological decomposition at municipal solid waste landfills." Presented at the Second Annual Research Symposium of the Florida Center for Solid and Hazardous Waste Management, Tampa, Fla. Reinhart and Townsend (1997). "Landfill Bioreactor Design and Operation." CRC Press, Boca Raton, Fla. Townsend, Miller and Earle (1995). "Leachate recycle infiltration ponds." Journal of Environmental Engineering, ASCE, 121(6), 465-471. B. Stabilization and Reclamation of Residuals The second major component of the project concerns the stabilization and possible reclamation of the residuals that result from the bioreactor landfill. One of the key goals of bioreactor landfill operation is the rapid stabilization of the waste. Therefore, the progress of such stabilization will be monitored throughout operation, especially as a tool to determine when bioreactor landfill operation is complete. In the proposed project, the stabilization process and the health of the treatment system will be monitored by a combination of temperature, gas, and leachate measurements. Since a biologically active landfill typically exhibits very warm temperatures, the health of the treatment system can be measured by tracking landfill temperature. Thus, in addition to the gas and leachate monitoring systems described above, temperature sensors will be placed within the landfill that send signals to a central data processing system. Samples of solid waste will also be collected at specified intervals to monitor the progress of the process of stabilization. This aspect of the project will entail the use of a drill rig to collect samples of landfill waste. The degree of stabilization will be measured by analyzing samples for biochemical methane potential. In addition to rapid stabilization, a second major potential benefit of bioreactor landfill operation is its potential to reclaim material from the landfill once degradation is complete. When stabilized, the landfilled waste can be excavated using the process of landfill reclamation. Stabilized waste will consist of a compost-like material, soil, and large non-degradable items. The compost and soil can be recovered by screening, and the remaining non-degradable material, which is inert, can be re-landfilled with little environmental risk. Some non-degradable materials such as metals may even be recovered from the waste stream. In order to maximize the benefits of bioreactor landfilling, the second component of this project will evaluate several possible methods for promoting rapid stabilization, enhancing the value of recovered stabilized waste products, and increasing operating efficiency. Several pre-treatment processes and compost product enhancements will be demonstrated, and their potential benefits evaluated. Pre-treatment processes include, for example, front-end sorting and shredding. Following excavation, stabilized waste can be screened, mixed with additives, and further processed in an in-vessel composter to enhance the value of the compost end product. The effects of each of these processing strategies on the value of the compost end product will be documented to measure the benefits and estimate the cost effectiveness of each alternative. These processing options are described in more detail in the following sections. Evaluating Pre-treatment Processes Pre-treatment processing can enhance bioreactor landfill operations in two ways. First, reducing the size of material particles entering the landfill promotes rapid organic decomposition. Second, sorting in-coming MSW to remove non-degradable materials improves operating efficiency. Both of these pre-treatment processing strategies will be demonstrated and evaluated by this project. Reducing the size of material particles prior to landfilling increases the relative amount surface area and, thus, accelerates the natural process of organic decomposition. To demonstrate the effects of particle size reduction, a hammer mill will be used to shred waste going into selected sections of the landfill. The rate of stabilization in these designated sections will be monitored by temperature sensors and compared to stabilization rates in landfill sections containing un-shredded material. In addition, waste samples will be collected and analyzed to assess the degree of stabilization during treatment and prior to reclamation. The results of these comparisons will help bioreactor landfill operators evaluate the benefits of pre-treatment shredding and facilitate future planning. To evaluate the benefits of sorting material before it is introduced into a decomposition/composting process, FCSHWM researchers will conduct studies at the Sumter County Solid Waste Facility, a mixed waste processing facility that includes a front-end materials recovery facility and an in-vessel compost digester system. Although a much more controlled and refined process, mixed waste composting has some objectives in common with bioreactor landfills, including front-end sorting, odor management, hazardous waste screening, developing a cost-effective testing protocol, and producing a final product that has many applications and markets. Generally, front-end sorting offers two advantages to bioreactor landfills. First, front-end removal of non-compostable materials from the waste stream reduces the quantity of material being introduced into the landfill and, thus, conserves landfill capacity. Second, front-end sorting eliminates the need to manage non-degradable material when stabilized residuals are excavated, thereby improving operating efficiency. Sumter County is currently removing non-compostable material from the waste stream, and project researchers will characterize and quantify the materials removed and assess the benefits of front-end recovery for recycling rates. The project will also assess the benefits of removing such materials as film plastic and glass to produce a higher quality or most cost effective compost end product. Based on study results, design or equipment improvements will be made to the facility to increase the quantities of the non-compostable material being removed prior to composting. Testing Stabilized Residuals and Identifying Applications Stabilized residuals excavated from the bioreactor landfill will consist of a compost-like material, soil, and large non-degradable items. Using a screening device, the larger non-degradable and inert materials will be segregated from the smaller compost-like and soil residuals. The larger non-degradable and inert materials will be either recovered for recycling (in the case of metals) or re-landfilled with little environmental risk. Smaller, stabilized residuals have numerous potential applications and market uses. Since these stabilized residuals are extracted from solid waste, the classifications established by current regulations will apply to material/compost produced from the excavation of bioreactor landfills. These regulations specify protocols for five distinct classifications of compost made from solid waste. To determine the parameters of appropriate applications and uses, the residuals will be tested for a variety of characteristics including heavy metal content, foreign matter content, and arsenic level. Samples of the smaller, stabilized residuals will be tested regularly to monitor quality and to document that the materials will not endanger public health or the environment. These test results will be compiled and compared with the data collected by the landfill’s central data processing center. Comparisons will be analyzed to establish relationships between operational activities of the landfill, including the pre-treatment processing described above, and the quality of the stabilized residuals. Beneficial applications and market uses for smaller, stabilized residuals are varied and extensive. Potential uses include, for example, commercial horticultural and agricultural applications; institutional and governmental projects; daily landfill cover; and land reclamation projects. Specific applications and market uses for the residuals will depend upon the material’s classification under current regulations. In each case, the application or use of the residuals will not adversely affect public health or the environment. Enhancing Compost End-Products To improve the quality or marketability of the stabilized residuals, additional processing strategies will be tested. For example, to reduce the foreign matter content of the material, additional screening may be performed following excavation of stabilized residuals. Additives such as sand may be mixed with stabilized residuals to produce a more useful product. The materials produced by alternative processing procedures will be tested and evaluated to determine if alternative procedures are beneficial to compost quality. One promising alternative that will be explored by this project is the introduction of residuals excavated from the bioreactor landfill into the in-vessel digesting system at the Sumter County Solid Waste Facility. The benefit of such an approach is to achieve a substantial reduction in waste in the bioreactor landfill at relatively low cost and to produce a high quality compost end product from the residuals. Since both the Union County and the Sumter County sites have good access to the interstate highway system, transporting materials between the sites at reasonable cost is feasible. To complement this phase of the project, material excavated from existing dry cells at the former Sumter County landfill will also be introduced into the compost digester system. Compost produced from processed dry cell residuals will be compared to compost produced from wet cell residuals to evaluate the potential benefits of this strategy. C. Education and Training Activities The project will provide valuable opportunities for education and training of engineering and environmental studies students in the university system. Some of the actual design work on the bioreactor cell, as well as some aspects of day-to-day operations of the facility would be done by university engineering students. The cell will be designed from inception as a training facility, with provisions for an instrumentation building and other components specifically designed for education and training. A second training opportunity lies with using inmate labor as workers in some elements of the project. In response to pressures to control costs and improve cost effectiveness, many solid waste managers view inmate labor as an attractive alternative. A well-planned inmate training program can help reduce operating costs and can also make a contribution to the community by providing training that will help in-mates who participate in the program secure employment in related fields on release. Inmate labor offers facility managers significant cost savings, but the effective use of in-mate labor depends upon a good training program and well managed work crews. Both of these elements require planning, experience, and the cooperation of local correctional staff. Sumter County has over ten years of experience using inmate labor from the Sumter Correctional Institution and currently uses inmate work crews in the operation of their MSW composting facility. Inmate labor for the bioreactor facility may also be available from the correctional facilities located in Union County. This project offers an excellent opportunity to develop a formal, certified training program for solid waste workers employed in operations at mixed waste processing facilities or bioreactor landfills. The training program could be developed with the cooperation of local correctional staff. A certificate program offers inmates an incentive to complete the training successfully and ensures uniformity of training standards over time. A formal training program is highly transferable and would be a valuable tool for facility managers who wish to implement in-mate labor at their facilities. This project provides an opportunity to systematically develop a training program to formalize lessons learned from Sumter County’s experience and from other research components of the project. D. Additional Project Objectives In addition to the three major components described above, the proposed project is also intended to achieve other important related objectives. These objectives are summarized briefly in the following sections. Regulatory Compliance Since the bioreactor landfill concept is a substantial deviation from current landfill design and operational regulatory criteria, a critical aspect of the project will be convincing regulatory agencies that such a facility can be operated in a manner which meets environmental standards and is protective of public health. The Florida Department of Environmental Protection and the U.S. Environmental Protection Agency will be full participants in the project to ensure that protective standards are met. Other Research Objectives Since the bioreactor landfill cell will be fully instrumented, it will provide an excellent opportunity to study many of the internal phenomena that occur in every landfill. These phenomena include the head or depth of leachate over the liner in an actual operating landfill (the head is the variable in determining possible leaking through the liner membrane), internal temperatures, moisture conditions in the waste, and other factors. Obtaining this data will be of enormous value to improving the design and operation of all types of landfill cells. Benefits to Rural Counties Finally, it should be noted that the project would provide fixed capital and other benefits to four rural counties, where solid waste management is an ongoing technical and financial challenge. These counties are particularly appropriate to receive these benefits since they have already demonstrated their willingness to try innovative solid waste management solutions. Baker, Union, and Bradford counties have demonstrated a creative solution to solid waste problems by forming the first multi-county solid waste authority in the state, while Sumter County has invested five million dollars in local bond revenue to design and implement the only working MSW composting facility in the state. III. PROJECT PARTICIPANTS The project would be a collaborative effort of the FCSHWM and its nine-university consortium, state agencies, and local governments. A Technical Advisory Group comprised of representatives of the participating entities and top private sector engineers and scientists will be established to provide technical advice during the life of the project. While other agencies and organizations may be added as the project gets underway and additional roles and opportunities for collaboration become apparent, currently proposed project participants include the following: The FCSHWM and Its Nine Member Universities:
State Agencies:
Local Governments:
Federal agencies:
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