SEPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/600/R-93H63
September 1993
Evaluation of the
Collier County, Florida
Landfill Mining
Demonstration
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EPA/600/R-93/163
September 1993
EVALUATION OF THE COLLIER COUNTY, FLORIDA
LANDFILL MINING DEMONSTRATION
by
Edward L. von Stein and George M. Savage
CalRecovery, Inc.
Hercules, California 94547
and
Solid Waste Association of North America
Silver Spring, Maryland 20910
Cooperative Agreement No. 818238
Project Officer
Lynnann Hitchens
Waste Minimization, Destruction, and Disposal Research Division
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Printed on Recycled Paper
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DISCLAIMER
The information in the document has been funded wholly or in part by the United States Envi-
ronmental Protection Agency under assistance agreement CR-818238 to the Solid Waste Association
of North America (SWANA). It has been subject to the Agency's peer and administrative review and
has been approved for publication as an EPA document. Mention of trade names or commercial prod-
ucts does not constitute endorsement or recommendation for use.
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FOREWORD
Today's rapidly developing and changing technologies and industrial products and practices
frequently carry with them the increased generation of materials that, if improperly dealt with, can
threaten both public health and the environment. The U.S. Environmental Protection Agency is
charged by Congress with protecting the Nation's land, air, and water resources. Under a mandate of
national environmental laws, the agency strives to formulate and implement actions leading to a com-
patible balance between human activities and the ability of natural systems to support and nurture life.
These laws direct the EPA to perform research to define our environmental problems, measure the
impacts, and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing, and
managing research, development and demonstration programs to provide an authoritative, defensible
engineering basis in support of the policies, programs, and regulations of the EPA with respect to
drinking water, wastewater, pesticides, toxic substances, solid and hazardous wastes, and Superfund-
related activities. This publication is one of the products of that research and provides a vital commu-
nication link between the researcher and the user community.
This publication is part of a series of publications for the Municipal Solid Waste Innovative
Technology Evaluation (MITE) Program. The purpose of the MITE program is to: 1) accelerate the
commercialization and development of innovative technologies for solid waste management and recy-
cling, and 2) provide objective information on developing technologies to solid waste managers, the
public sector, and the waste management industry.
E. Timothy Oppelt
Risk Reduction Engineering Laboratory
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CONTENTS
Disclaimer ii
Foreword iii
Figures vi
Tables vii
Acknowledgments ix
Conversion Factors ....x
Abstract xi
Executive Summary 1
Introduction 1
Landfill Mining Technology 1
Field Evaluation Procedures and Results 2
Markets for Recovered Materials 3
Regulatory Impact 4
Technical Evaluation 4
Economics 4
1. Introduction 5
Background 5
Site 5
Objectives 6
Methodology 6
Organization of This Report 8
2. Landfill Mining Technology : 9
Concept of Landfill Mining 9
Equipment Used During the Evaluation 9
System Configuration and Mobile Equipment 12
3. Field Evaluation Procedure and Results 13
Description of Processing and Testing Field Activities 13
Methods 14
Results 14
4. Markets for Recovered Materials 30
Description 30
Market Demand Conditions 30
Market Barriers 31
IV
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5. Regulatory Impact 33
Introduction 33
Review of Applicable Florida Regulations 33
Need for Additional Regulations , 34
6. Economic Evaluation 36
General 36
Cost Estimates 36
Revenues and Avoided Costs 40
7. Conclusions and Recommendations 41
Conclusions 41
Recommendations 44
References,
Bibliography.,
.45
.46
Appendices
A1
A2
B1
B2
B3
C1
C2
C3
C4
C5
C6
C7
D1
D2
D3
D4
E1
E2
F1
F2
G1
Comparison of Average Compositions of Solid Wastes in Florida
Naples Landfill - Summary Data
BCMR and Enhanced Landfill Degradation
Other Projects
Equipment Specifications
Air Quality Survey Report
Field Evaluation - Daily Processing Times
Primary Stream Composition Data
Laboratory Reports - Solid Fractions
Laboratory Reports - Solid Fractions - Bacteriological Analyses
Seed and Germination Analysis Data - Soil Fraction
Glass Size Distribution
Landfill Mining Product Evaluation - List of Contacts
Market Survey Responses
General Recyclables Demand and Price
Enhanced Product Quality
Florida Heavy Metal Criteria
Florida Compost Classification and Allowable Use Criteria
Test Conditions - Estimated Costs
Cost Elements for Use in Determining Project Economics
Landfill Mining Site Screening Criteria
Appendices are not included in this document. Limited quantities are available from Lynann Hitchens,
U.S. EPA Center Hill Research Facility, 5995 Center Hill Road, Cincinnati, OH 45224.
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FIGURES
Number Page
1 Block Flow Diagram - MITE Test Conditions 2
2 Naples Landfill - Site Plan 7
3 Landfill Mining Alternatives - Block Flow Diagram 10
4 General Arrangement - Test Conditions 12
5 Composition of Process Output Streams 17
6 Variation in Composition of Potentially Recoverable Target Components 20
7 Average Material Balance for Collier County Landfill Mining System 22
8 Comparison of Metals in Soil Fraction with Florida Compost Regulations 24
9 Estimated Market Potential for Mined Materials 31
VI
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TABLES
Number Page
1 Mass Balance and Efficiency in Stream Concentrations 3
2 Typical Mid-1970's Florida Waste Composition 6
3 Field Evaluation - Daily Processing Times 15
4 Summary of Material Balance and Processing Rate , 16
5 Collier County Average Compositions of the Process Streams 18
6 Composition of Florida Raw Waste and Collier County Mined Material 19
7 Summary of Laboratory Results for the Primary Process Stream Fractions 21
8 Average Recovery by Fraction 23
9 Collier County - Results of Seed and Germination Analysis of Soil Fraction 24
10 Comparison of Collier County Soil Fraction with MSW Compost and Other Products 26
11 Collier County Aluminum/Residue Fraction - Particle Size Characteristics 27
12 Air Quality Monitoring Results 28
13 Collier County - Glass Size Distribution 29
14 Glass and Aluminum Fraction - Adherent Dirt 29
15 Bulk Densities of Product Streams ". 29
16 General Market Barriers for Source Separated Recyclables 32
17 Florida's Heavy Metal Criteria for Compost 34
VII
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18 Florida Compost Classification and Allowable Use Criteria 35
19 Estimated Capital Costs 38
20 Estimated Annual Operating Costs , 38
21 Summary of Net Project Costs... 39
22 Mass Balance and Concentration Efficiency Summaries 41
viii
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ACKNOWLEDGMENTS
This report was prepared under the coordination of Lynnann Hitchens, U.S. Environmental
Protection Agency (EPA) Municipal Solid Waste Innovative Technology Evaluation (MITE) Program
Manager, at the Risk Reduction Engineering Laboratory, Cincinnati, Ohio. Contributors and reviewers
of this report include Charlotte Frola and Tim Donnelly, Solid Waste Association of North America
(SWANA); Robert E. Fahey, Solid Waste Director, Collier County Solid Waste Department; and Richard
I. Stessel, Assistant Professor, University of South Florida.
This report was prepared for EPA's MITE program by Edward L. von Stein and George M.
Savage of CalRecovery, Inc. Air emission samples were collected and analyzed by S. E. Environmental
Laboratories. Solid analyses were done by SSM Laboratories and the Federal Seed Laboratory.
The authors would like to acknowledge the help and support provided by Robert Fahey, former
Solid Waste Director; Keeth Kipp, Recycling Coordinator; and the Collier County Solid Waste
Department Staff in planning and preparing for the demonstration.
IX
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CONVERSION FACTORS
English (US)
Factor
Metric
Length:
Area:
Volume:
Mass:
Pressure:
Energy:
1 inch (in)
1 foot (ft)
1 mile (mi)
1 square foot (ft2)
1 acre
1 gallon (gal)
1 cubic foot (ft3)
1 cubic yard (yd3)
1 grain (gr)
1 pound (Ib)
1 ton (t)
1 psi
1 Btu
1 kilowatt hr (kWh)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
2.54
0.305
1.61
0.0929
4046.7
3.78
0.0283
0.7661
64.8
0.454
907
0.0703
1.05
3.60
centimeter (cm)
meter (m)
kilometer (km)
square meter (m2)
square meter (m2)
liter (L)
cubic meter (m3)
cubic meter (m3)
milligram (mg)
kilogram (kg)
kilogram (kg)
kilogram per square centimeter
(kg/cm2)
kilojoule (kJ)
megajoule (MJ)
Temperature: (Fahrenheit - 32)
0.556
Celsius
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ABSTRACT
This report describes the landfill mining process as demonstrated under the Municipal Solid
Waste Innovative Technology Evaluation (MITE) Program by the Collier County (Florida) Solid Waste
Management Department. The MITE program is sponsored by the U.S. EPA to foster the
demonstration of innovative technologies for the management of municipal solid waste. Landfill mining
is the recovery of useful resources (e.g., cover soil at Collier) from previously landfilled solid wastes.
During the two week demonstration of Collier County's Landfill mining technology, 265 MT (292 tons) of
excavated material were mechanically processed by County staff through coarse and fine screens, an
air knife/de-stoner, and magnetic separators into nine fractions. Two of these fractions - a soil fraction
and a ferrous fraction - were determined to be reusable.
Based on a sampling of the process stream, a material balance prepared for the mechanical
processing system indicated that nearly 60% by weight of the feed was recovered as a minus 2 cm (3/4
in.) soil fraction. Chemical analyses of four key process fractions were conducted. The characteristics
of the recovered soil fraction were similar to a low-grade MSW compost. State regulators have
approved the use of the soil fraction as landfill cover. The residues from processing were handled as
raw MSW and landfilled. The heating value of the process residues was 14,421 kJ/kg (6,200 Btu/lb).
Air quality in the vicinity of the processing equipment was monitored during operation; minor releases
of metals and bacteria were noted.
Samples of the recovered ferrous and plastics fractions were evaluated by potential markets;
none felt that the materials were competitive with recyclables available from source-separation
programs. In the analysis of project economics, then, no revenues were available to offset the costs.
Acquisition of a similar system and preparation of a processing site are estimated to cost
approximately $1,200,000 excluding legal and engineering fees. Amortized capital costs and operating
costs for one year was estimated to be $1,020,000. Based on the demonstration period, the unit cost
was $127/MT ($115/ton) of material mined.
This report was submitted in fulfillment of (Contract #850-0991-1) by CalRecovery, Inc., under
an agreement with Solid Waste Association of North America with the sponsorship of the U. S.
Environmental Protection Agency. This report covers a period from April 1992 to July 1992, and work
was completed as of January 1993.
xi
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EXECUTIVE SUMMARY
INTRODUCTION
The Collier County, Florida, landfill mining project was selected for the United States
Environmental Protection Agency's (EPA) Municipal Solid Waste Innovative Technology Evaluation
(MITE) Program in 1991. Landfill mining is the recovery of useful resources from previously landfilled
solid wastes. Material excavated from a solid waste landfill includes decomposed and undecomposed
solid waste and the soil that was used as cover material. The demonstration project conducted under
the MITE program evaluated Collier County's excavation and mechanical processing of previously
landfilled wastes to reclaim cover material, for continued landfill operations on the site, and other useful
materials.
Objectives of the evaluation were to assess:
• the capacity and performance of the equipment,
• the environmental aspects of the project and the characteristics of the recovered
materials,
• market acceptance of recovered materials, and
• probable costs and economics of the project.
Collier County contains some 5,457 km2 (2,107 sq mi), and had a population of 152,000 in
1990. Residents are generally business owners, professionals, farmers, or retirees. The climate is
subtropical, with 150 cm (60 in.) of rainfall annually. Ground water elevation is generally close to grade.
The composition of raw Florida solid waste from the mid-1970s, the age of material mined, was about
37% paper, nearly 2% plastics, about 10% metals, and approximately 51% other organic or inert
materials.
Five acres of the unlined landfill cells 1 & 2 at the Naples Landfill, the site of the MITE project,
have been mined since 1986. In 1992, between April 21 and 30, the period of the MITE project
demonstration, 265 MT (292 tons) of material were processed through the separation system, and 155
MT (171. tons) (or about 60% of the total) were recovered as a soil fraction and subsequently used as
landfill cover. A site plan of the landfill is provided in Section 1.
LANDFILL MINING TECHNOLOGY
After excavation of landfilled material, the soil fraction was mechanically separated from the
remaining material for use as landfill cover. The system for the MITE demonstration included a front
end loader, a dozer, and an excavator that fed waste to a trailer-mounted coarse screen, a trommel
screen and an air knife/de-stoner interconnected by belt conveyors with two magnetic head pulleys, as
shown in Figure 1. Oversize materials (e.g., tires and carpets) that could not be processed by the
equipment (i.e., the non-processibles) were removed by a coarse screen that was the first piece of
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processing equipment in the processing system. The output streams of the system were soil (S-1)1,
plastics (S-2), ferrous (S-3 & S-6), aluminum/residue (S-4/S-5), non-processibles (S-7), finger-screen
unders (S-8), and heavies (S-9). Of the output streams obtained during the test, finger-screen unders,
heavies, plastics, residue/aluminum and non-processibles Were landfilled again. Ferrous was
stockpiled for later sale. One stream, the soil fraction, was used as landfill cover during the course of
the evaluation.
Soil (S-1) Ferrous (S-3)
-2cm
(-3/4")
Plastics
(S-2)
Stockpile
-15cm
(+3/4")
+15 cm
(+6")
Non-processibles (S-7)
-2cm
(-3/4")
Finger
Screen Unders
(S-8)
Heavies
(S-9)
Figure 1. Block flow diagram - MITE test conditions.
FIELD EVALUATION PROCEDURES AND RESULTS
The process train for the MITE demonstration was selected based on the results of previous
Collier County landfill mining experience and equipment availability. Processing equipment was
leased, loaned or donated to the County. During excavation, one person operated the front end loader
and one drove the truck; in addition, one dozer operator was periodically needed. Five to seven
personnel were required to operate the separation system, a truck, and a front end loader during the
demonstration.
Field protocols for the demonstration were based on an approved EPA Category III Quality
Assurance Project Plan (QAPP). Materials were weighed at all input and output points. Samples were
Designations S-1, S-2, etc. refer to sample locations (S-1 thru S-5) or to unsampled streams (S-6
thru S-9).
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collected from each process stream for laboratory analysis and for waste characterization. Materials
were manually sorted into 14 categories of materials.
Closure of the input and output mass balance exceeded 90% for the week. The average
processing rate was 12 MT (13 tons) per hour; the mass balance and stream purity data are
summarized in Table 1. Stream purity for each fraction is measured as (weight of fraction/weight of
stream).
TABLE 1. MASS BALANCE AND EFFICIENCY IN STREAM CONCENTRATIONS
Fraction Mass
Non-processible
Soil
Ferrous
Plastics
Residue & Other a ..
Fraction (wt %)
18
60
2
2
18
100
Stream Purity (wt %)
Not reported
94
82
75
61
-
a Includes heavies, finger-screen unders and aluminum.
Non-processibles were the oversized materials separated by the coarse screen. The soil
fraction separated by the trommel resembled dirt, and contained only particles that passed through the
2 cm (3/4 in.) screen. The ferrous stream consisted of those materials which were separated by the
primary magnetic separator, and the plastics stream contained primarily light plastics and films. The
residue and other fractions included three streams which were produced by the air knife: those
particles under 2 cm (3/4 in.), the heavies, and the aluminum/residue stream. In Table 1, the stream
purity denotes the weight percentage of target material intended to be in a particular output stream
(e.g., ferrous in the ferrous fraction).
Tests of the soil fraction for 34 parameters indicated, among other results, many bacterial
colony-forming units, a slightly basic pH, a nitrogen content one tenth that of MSW compost or peat, a
lead content of 52 mg/kg (ppm), and mercury content of <0.30 mg/kg (ppm). The residue fraction had
a fuel value of about 14,421 kJ/kg (6,200 Btu/lb), a slightly basic pH, lead content of 104 mg/kg (ppm),
and mercury content of 0.36 mg/kg (ppm).
An air quality survey conducted, concurrently with the waste sampling program indicated that
dust, gypsum fiber, lead and copper concentrations were well below permissible exposure limits based
on workplace standards, but that microbial agents may have been released during processing. These
microbial agents were observed to range between the OSHA limits and ACGIH limits for worker
exposure. Other pollutants were below the detection limit of the equipment.
MARKETS FOR RECOVERED MATERIALS
Occasionally, Collier County, has marketed ferrous scrap recovered from mining to a local
scrap market. Market representatives examined samples of recovered ferrous, aluminum, and plastics,
and an agricultural extension service examined a soil sample. Product quality for these materials was
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less than acceptable to these representatives. Quality could potentially be improved through
additional processing conducted at the landfill mining site or at a materials recovery facility (MRF).
REGULATORY IMPACT
No state or federal regulations currently address landfill mining specifically. As is the case with
other states that have hosted projects, the Florida Department of Environmental Regulation regulates
Collier County's activities through its landfill operations permit, and allows the use of the reclaimed soil
fraction as landfill cover.
No state or federal regulations presently exist to define the quality that a soil fraction must
achieve to qualify for off-site or on-site use. Because Florida regulates compost quality, these
regulations could provide guidance in considering requirements for the off-site use of the soil fraction
from landfill mining operations. Material of the quality produced as soil fraction during the MITE
demonstration project meets all of these compost regulations.
TECHNICAL EVALUATION
The Collier County landfill mining system used relatively simple processing, operations and
equipment. The system effectively and efficiently recovered a soil fraction that was environmentally
benign when compared with Florida compost regulations and was apparently a good growing medium
based on growth tests using timothy grass seeds. The recovery of ferrous averaged about 78% with a
purity of about 82%. The recovery of film plastics yielded a product with a purity of about 75%. No
conclusions are offered regarding the aluminum separator since this subsystem was judged
incompatible with capacity requirements and particle size of the infeed stream, and was not tested.
However, electro-mechanical separation of aluminum in a MSW processing facility typically yields a
recovery in the 50% to 60% range.
Availability of the processing system averaged 53%. Similar equipment would likely perform as
well on a variety of feedstocks (e.g., construction and demolition debris). Equipment downtime during
the test was due primarily to a hydraulic system failure, operator or sampler training, or wet weather
conditions.
ECONOMICS
Capital investment to conduct the Collier County MITE demonstration project was relatively
low, since the County avoided purchasing equipment. The equipment and construction portion of the
capital cost for a similar system would be about $1,200,000. The annual operating cost would be
about $1,020,000. The unit costs of mining, in terms of tons mined during the test, was $127/MT
($115/ton).
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SECTION 1
INTRODUCTION
BACKGROUND
Landfill mining is the excavation and mechanical processing of previously landfilled material to
recover materials or landfill airspace, to reduce the size of a landfill, or to transfer material from an
unlined to a lined landfill. Landfill mining can only occur if wastes were disposed in a landfill or dump, if
the technology to mine is available, and if a technically feasible strategy to manage mined materials
exists.
One of the earliest applications of landfill mining was the mining project conducted by the
Collier County (Florida) Solid Waste Management Department at the Naples Landfill. The mined area
contained municipal solid waste that had been landfilled for 10 to 15 years. Between 1986 and 1992,
the County mined over 63,500 MT (70,000 tons) of solid waste and cover material, averaging 40 to 70
MT (40 to 80 tons) per hour during processing. Since Collier's application of the technology, few other
domestics and internationals communities have applied the concept, partially because the landfill
mining technology is new and solid waste planners could not rely on a well-established body of
experience.
SITE
Collier County
Collier County is located in southwest Florida on the Gulf Coast, and contains approximately
5,457 km2 (2,107 sq mi). Collier is one of the fastest growing areas in the country. Collier County is
primarily residential with some farming in the northern part of the County. The climate is subtropical
with an average annual rainfall of about 150 cm (60 in.). The area's potable water is supplied via
groundwater treated at a treatment plant adjacent to the Naples Landfill. Wastewater is treated
regionally; sewage sludge is disposed at the Naples Landfill.
Solid Waste Management
Historically and currently, Collier County has relied on landfill disposal of solid wastes. Waste-
to-energy was considered in the early 1980's; landfill mining was conceived as a potential fuel source
to meet solid waste commitments at the waste-to-energy facility. Table 2 shows the composition of a
mid-1970's Florida raw residential waste stream similar to that being mined under this test. The Naples
Landfill is a permitted Class I landfill of approximately 130 ha (320 acres), operated by Collier County
and serving almost 90% of the County's population (Collier County, n.d.).
Barre, MA; Bethlehem, NH; Edinburg, NY; Lancaster, PA; and Thompson, CT.
Bangkok, Thailand; and Seoul, Korea.
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TABLE 2. TYPICAL MID-1970'S FLORIDA RAW WASTE COMPOSITION
Component
Paper
Glass
Plastic
Metal
Yard Wastes
Food Wastes
Wood Wastes
Other
Total
Percent
by Weight
37.0
10.6
1.6
9.6
15.6
15.2
1.6
8.8
100.0
The site plan for the Naples Landfill (Figure 2) depicts unlined cells 1 and 2, which were filled
from mid-1976 to mid-1979 and contain approximately 230,000 ms (300,000 yds) of primarily residential
wastes generated by residents and tourists. Site soils are sandy and groundwater is shallow.
OBJECTIVES
The primary objective of this MITE evaluation was to assess the technical feasibility of landfill
mining as demonstrated at the Naples Landfill site. To accomplish this objective, the subcontractor
quantified process output streams through mass-balance measurements, and characterized them
through hand sorting and laboratory analyses. The soil output stream (i.e., the soil fraction) was
evaluated with respect to Florida State compost quality criteria. Air quality impacts were assessed.
The acceptance criterion for project results was determination at a 90% confidence level, with an
estimated error of ± 25%. The landfill mining process as a whole was evaluated with respect to
technical, environmental, and selected health and safety issues.
Other objectives were to assess the reaction of potential materials markets to samples of
ferrous, aluminum, and soil streams; and to estimate the capital and operating costs of the landfill
mining demonstration project.
METHODOLOGY
Background and Preparation
Project background information included descriptions of the Naples Landfill, its past operating
history, and the history of the County landfill mining program. A project plan was prepared in
accordance with EPA Category III Quality Assurance Project Plan requirements. This plan specified
sampling and analytic methods and analyses based on EPA and Florida Department of Environmental
Regulation (FDER) requirements, and provided a concise procedural reference manual.
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1628m (53410
Cu
1
|
Access Road
\ ^Undeveloped
\ Cell 5 -r
\
\tells 3 &A
/ \
1001 Bufler (Tyi
X
Cell 6
plcal, all sides)
X
\Cells1 &^
I a
/^/ \
7 / x
-Scale House Mined Area
MITE Processing Area
Not to Scale
Key:
x Monitoring Well
Figure 2. Naples landfill - site plan.
Field Testing
During the April 20 to 24, 1992, field test, the weather was generally hot and clear with rain
showers on several afternoons. Since Collier County intended that a developmental process train be
evaluated, County staff acquired new landfill mining equipment for the MITE project. The feedstock for
the test system came from a stockpile of excavated material. Fewer samples than originally planned
were taken due to mechanical breakdowns and to operator and sampler training. Output stream
samples were collected and air quality was monitored at the site. Samples were labelled, packaged
and shipped to laboratories for analysis. For mass balance determinations, weighings of material by
input and output stream were taken at the end of the four field sampling days. Between April 27 and
30,1992, Collier County staff collected additional mass balance data.
Evaluation
The separation system was evaluated for its mechanical efficiency, availability, and
environmental effects. Mechanical efficiency was determined from the purity of the output streams,
and the ability of the system to concentrate target waste components in specific streams. Availability
was defined by the actual run time as a fraction of the potential run time over the term of the test; and
environmental effects, including health concerns, were determined by the impacts of the system on air
quality and the quality of products produced.
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r
ORGANIZATION OF THIS REPORT
This introductory section summarizes the background conditions related to the MITE project in
Collier County. Section 2 provides an overview of the landfill mining technology and the equipment at
Collier County. The field test procedures and results are presented in Section 3. Section 4 discusses
the current secondary materials market conditions faced by landfill mining developers. Section 5
outlines Florida regulations related to landfill mining. In Section 6, economic analyses are presented
while Section 7 provides evaluations, conclusions and recommendations. A separately bound
appendix volume contains laboratory reports, detailed equipment specifications, and other data.
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SECTION 2
LANDFILL MINING TECHNOLOGY
CONCEPT OF LANDFILL MINING
This section describes the landfill mining concept generally and the equipment and test
procedures used at Collier County for the MITE evaluation. As the block flow diagram in Figure 3
indicates, the process of landfill mining begins with the excavation of previously landfilled material,
generally with a front-end loader or excavator. Mined material may be stockpiled, then processed
through an array of separation equipment that mechanically sorts the material into discrete streams
("fractions"). The system demonstrated by Collier County was designed to maximize recovery. The
intent was to separate the material into the following streams: non-processibles (e.g., oversized items),
a soil fraction, lighter (e.g., film) plastics, ferrous metals, and aluminum. In simpler systems, the soil
fraction may be separated for use as cover and all remaining streams may be landfilled.
The soil fraction may be used as landfill cover immediately, or stockpiled for future use. With
regulatory approval, recovered recyclable products can be shipped off-site to further processing
and/or market. Non-processibles are landfilled again. The remaining material residue, that is not
suitable for recycling, stockpiling, or landfill cover is typically landfilled; alternatively this residue may be
used at a waste-to-energy facility to supplement MSW feed. The mined area may serve to reduce the
landfilled area to receive final cover under RCRA Subtitle D, or may become a new landfill cell.4
With one exception, domestic landfill mining projects have been performed by the landfill
owner and/or operator. Project participants have included equipment or service suppliers, state
regulatory agencies, and not-for-profit institutions. Future projects may benefit from formal feasibility
analyses to optimize operations; few early projects had the advantage of engineering design. Most
projects have required modifications to landfill operating or closure permits, although the impacts of
such modifications on schedules or costs have not been determined.
Projects in the public sector have typically been structured as public works projects, with
municipal staff or consultants fulfilling architect-engineer roles. In 1990 Collier County received bids
from three firms for landfill mining services; by 1993, however, none of these firms offered such
services. One other firm, MFM Corp. of Greenwich, CT, currently offers landfill mining services.
EQUIPMENT USED DURING THE EVALUATION .
Excavation Equipment
The excavation of materials processed during the field evaluation was accomplished with a
Michigan front-end loader (FEL) with a 5 ms (6 yds) toothed bucket and a Caterpillar D8, used to
The so-called "bury, compost, mine, and reclaim" (BCMR) concept, which relies on waste
degradation in landfills, is an example of planning for a new cell.
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Key Numbers:
1 Excavated Mat'l 4
2 Cover Soil 5
3 RawMSW 6
Residue
Soil Fraction as Cover
To/From Stockpile
7 Mined Recyclables
8 Residue as Fuel
9 Ash
Figure 3. Landfill mining alternatives - block flow diagram.
initiate excavation or break up the more densely compacted areas. The FEL, the D8, and an available
open-top transfer trailer were used to stockpile material prior to processing.
Process Equipment
General-
As Figure 1 indicates, the configuration for this MITE evaluation used a grizzly separator to
separate the oversized non-processibles (S-7) followed by a trommel for separating the soil fraction (S-
1). An excavator was used to feed materials. The trommel oversize fraction passed by a magnetic
separator to capture ferrous materials (S-3) and through an air knife for further separations. Slight
10
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modificationss were incorporated during installation to reduce the amount of material fall-through at
equipment junctures and to maintain safe operations during the evaluation period. Figure 4 provides a
general arrangement sketch of the process equipment used during MITE demonstration project.
Grizzly/Trommel--
The grizzly, a coarse screening device, prevents the processing of oversized bulky materials
that could damage other equipment. The trommel separates feedstock into three streams by size.
Mechanical processing rates obtained by pilot testing the grizzly/trommel were reported for
"dry leaf compost" as being 70 ms/hr (90 yds/hr) of material passing a 2.5 cm (1 in.) screen and 40 to
50 ms/hr (50 to 70 yds/hr) of the same material using a 1.25 cm (1/2 in.) screen (D. Castanzo,
Powerscreen, personal communication, 1992). Controls are chassis-mounted. The machine is
equipped with a system to hydraulic-ally raise the grizzly bars to clear them. Maintenance items
reported by the manufacturer are periodic adjustment of conveyor belts for stretch, routine lubrication,
and attention to keeping mechanical parts clean; no maintenance was required during the test.
Air Knife/De-stoner--
In operation, material entered the air knife/de-stoner, passed over a vibrator finger screen and
was separated into oversize (overs) and undersize (unders) fractions. At the low feed rates used
during the demonstration test, this process appeared smooth and continuous without material
clumping or jamming the finger screen. However, two or three times during the test, the depth of
burden on the finger screen became great enough to impair performance. After the finger screen
section, the overs were further classified through an air fluidizing section before being exposed to dual
"air curtains" which provided the final classification. The heavy materials - "middlings" - (aluminum,
ferrous, and residue) fell out of the air stream within the unit and onto a discharge conveyor and the
final product - "superlights" - (plastic) was carried off with the air stream and discharged (blown) into a
debris box (roll-off box).
Controls were mounted on the blower section of the unit. Modifications to the support
structure of the knife were required to permit conveyors to be installed. Maintenance was not required
during the field evaluation.
Magnetic Separators-
The magnetic head pulleys on the belt conveyors removed magnetic material for recovery and
also served to protect downstream unit operations that could have been damaged by the material. The
primary magnet was used to separate the ferrous fraction from the trommel oversize fraction. The
secondary magnet was added to reduce ferrous content of the aluminum/residue fraction from the air
knife/de-stoner to protect the planned aluminum separators. Field modifications included suspending
a steel baffle plate from the support structure of the conveyors in order to direct the secondary ferrous
discharge into containers. Independent of burden depth and purity level of the respective ferrous
fractions, both magnets appeared to function properly. No maintenance was required during the
operation.
5 Modifications included inserting 1.2 m (4 ft) by 2.4 m (8 ft) plywood sheets to baffle material
discharge from the air knife, and adding containment skirts on conveyors.
6 The planned aluminum separator was undersized and inappropriate for the application and was
not tested.
11
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SYSTEM CONFIGURATION AND MOBILE EQUIPMENT
The equipment was installed on a level, compacted, crushed limestone-surfaced area (46 m by
12 m (150 ft by 40 ft)) on top of cells 1 & 2, as shown in Figure 2. During the test, additional crushed
stone was placed to provide suitable maneuvering room. Based on field experience, a minimum 15 m
(50 ft) buffer is required to move trucks, replace full roll-off boxes, and ensure safe and efficient
equipment operation.
Mobile equipment included one excavator with a 1.1 ms (1.5 yds) bucket, one blade-equipped
bulldozer, one wheeled loader with a 4.6 ms (6 yds) bucket, and one skid steer loader with a 3/4 m3 (1
yds) bucket. A slide body (i.e., roll-off) truck and an open-top transfer trailer were used to transport
material.
Aluminum/Residue (S4/S5)
Ferrous (S3)
27m (87") (221)
Roll-off Debris Box
Roll-off Debris Box for Sampled Stream
Figure 4. General arrangement - test conditions.
12
-------
SECTIONS
FIELD EVALUATION PROCEDURE AND RESULTS
DESCRIPTION OF PROCESSING AND TESTING FIELD ACTIVITIES
This section describes the field methods and presents the results of the MITE evaluation. The
selection of the process train was based on the experience of Collier County staff, and on the timely
and low/no cost availability of suitable equipment. Throughput capacities of equipment could not be
precisely matched, which limited productivity.
Collier County repotted that two full-time and one part-time staff members excavated the
material. Depending on location in cells 1 & 2, the nominal excavation depth varied from 0 to 5.5 m (0
to 18 ft). The 111,000 m3 (145,000 yds) excavated from 2 ha (5 acres) of cells 1 & 2 between 1986 and
1992 took approximately 6,000 hours to complete. This 18.5 m3/hr (24.2 yds/hr) average rate is
substantially lower than typical rates of production (75 m?/hr(100 yds/hr)) (Means, 1992) for excavating
common earth. This lower rate reflects the greater difficulty of excavating waste as compared to
earth. Perched leachate (leachate trapped by an impervious layer) was not reported during the
excavation.
The process train for the MITE project demonstration represented a departure from previous
configurations used by the County in that an air knife/de-stoner was used, making this the most
mechanically intensive system tested at Collier to date. Only portable conveyors and mobile
equipment owned by Collier County were used for the test. Other landfill mining processing equipment
was leased, loaned, or donated to the County. Portable diesel electric generators and diesel-powered,
machine-mounted hydraulic systems supplied the power. At various times, five to seven Collier County
Solid Waste Department equipment operators, maintenance personnel, and supervisors conducted the
demonstration.
Processing equipment arrived at Naples Landfill during the first week of April 1992. Site
preparation took less than 2 days. County employees installed the equipment. Final test runs and
adjustments were complete by April 21, with some assistance from equipment vendors. The aluminum
separator was undersized for the intended use and was not tested.
Field protocols were based on the QAPP. To minimize the impact of sampling, field samples
representing less than 1% of the total production were collected at times when the process line was
stopped for operator break or some other reason. The field evaluation (i.e., mass balance, waste
characterization, and laboratory sampling) occurred between April 21 and 24 with County personnel
recording additional mass balance data between April 27 and 30. Weather during the evaluation
included periodic afternoon showers, with temperatures near 30°C (85°F).
13
-------
METHODS
The processing equipment was installed adjacent to the mined material stockpile. The
excavator loaded materials from fresh stockpiles that did not include earlier process run residuals or
disposed material from site preparation.
For the mass balance determination, materials were weighed at all input and output locations.
Materials were collected in previously weighed 15 to 23 ms (20 to 30 yds) roll-off boxes (debris boxes),
driven the 1.6 km (1 mile) round trip to the scalehouse, and weighed with the landfill's state-certified
truck scale. Multiple weighings? of the soil fraction were sometimes necessary to avoid overloading of
debris boxes. During the evaluation, the reclaimed soil fraction was used as cover material on cell 6.
The remaining fractions were stockpiled and/or landfilled.
To evaluate the quality of recovered products, samples were collected for laboratory testing
and waste characterization. For lab samples, 0.8 to 1.1 ms (1 to 1-1/2 yds) samples were collected by
hand shovel or by skid steer loader from the debris boxes and delivered to a sorting area sampling
grids. Subsamples were randomly selected; these were weighed, manifested, and sent to laboratories
for chemical and phytotoxicity. analysis. The remaining sample was then, shovelled onto a table for
characterization by manual sorting.
To compare the landfHI mining air quality results with those of published permissible exposure
limits (OSHA, NIOSH, ACGIH), an air quality survey was conducted on April 20 through April 24, 1992,
and consisted of 12 individual sampling events. Climatological data were also collected for each
sampling day.
Collier County conducted the demonstration under its own health and safety guidelines. The
subcontractor adopted "level C" protection.9 based on its health and safety plan.
RESULTS
Mass Balance
Processing times appear in Table 3. Availability averaged 53%, assuming 24 possible hours
for the first week of the field test, and reached a peak of 89%. During hours of operation, 265 MT (292
tons) of mined material were processed. Based on truck fuel gauge readings, a variation in net weights
of not more than 0.5% occurred as a consequence of changes in trie weight of fuel. County staff report
that the excavator consumed about 17 liters/hr (4.5 gal/hr) of diesel fuel during the test, the trommel
consumed about 15 liters/hr (4.0 gal/hr), and the generator for the air-knife consumed about 13 liters/hr
(3.5 gal/hr). Estimated roll-off truck consumption was 11 liters/hr (3 gal/hr), and dozer and loader
consumption was 19 liters/hr (5 gal/hr).
Table 4 presents the process mass balance in terms of minimum, average, and maximum
masses; standard deviation; standard error; and 90% confidence interval for each fraction. Note that
with the exception of the "additional ferrous" category, all results exceed the study objectives of a 90%
confidence interval with a standard error of less than 25%. Table 4 also includes an average hourly
process rate and material balance closure (output/input) percentage. Differences between the
7 Using two or more roll-off debris boxes at a sample 'point during one day.
8 A 7.3 by 4.9 m (24 by 16 ft) sampling grid of loose plywood laid on a 1 mil plastic tarp.
9 Hard hats, gloves, boots, eye protection, work clothes, and optional dust masks.
14
-------
TABLES. FIELD EVALUATION - DAILY PROCESSING TIMES
DATE
21 -Apr
22-Apr
23-Apr
24-Apr
27-Apr
28-Apr
29 -Apr
30-Apr
CUMULATIVE
RUN TIMES
RUNTIME DAILY
START STOP (minutes) (hrs.:mins.)
11:22 11:46 24 0:24
11:53 12:00 7 0:31
Lunch
1:38 1:41 3 0:34
Air Knife Clog
1:45 1:55 10 0:44
Broken hydraulic hose
Install new hydraulic hose
9:39 9:50 11 0:11
Modify air knife separator
10:08 10:30 22 0:33
Change S1 box
10:40 11:15 35 1:08
Lunch
12:30 1:30 60 2:08
Light rain, change infeed
-:- -:- 321 5:21
4 run periods
separated by
changes to boxes
-:- -:-r 270 4:30
Run time data were not collected by the County during the second week.
— :— — :— — i • • —
_;_ - _;_ _ . -
_;_ _:_
-:- -:- - -
TEST
(hrs.:mins.)
0:44
2:52
8:13
12:43
_
-
-
-
15
-------
TABLE 4. SUMMARY OF MATERIAL BALANCE AND PROCESSING RATE (a)
Stream
No.
S1
S8
S9
S7
S2
S4/S5
S3
S6
Material
Soil Fraction
(Trommel Unders)
Finger Screenings
Heavies
Non-Processibles
Subtotal
Non-Processibles
Plastics
Aluminum/Residue
Ferrous
Additional Ferrous (c)
TOTAL
Processing Rate (MT/hour) (d)
(TPH)
Material Balance Closure
(Output/Input)
Avg. (b)
59.39%
3.31%
7.43%
17.94%
25.37%
2.42%
7.69%
1.73%
0.08%
100%
12.1
13.3
90.2%
% by Weight
Min.
46.81%
2.43%
5.37%
9.35%
16.44%
1.62%
6.61%
1.34%
0.04%
—
9.9
10.9
Max.
68.61%
4.22%
10.53%
26.45%
36.97%
2.97%
9.00%
3.00%
0.16%
—
16.4
18.1
Notes:
(a) Does not Include April 28 data due to discrepancies in weight recordings.
(b) Based on 7 processing days. Weights are per cent of total recovery in all streams after processing.
(c) "Additional Ferrous" fraction was generated by the residue magnet.
(d) Based on 4 processing run times (see Table 3) and quantities.
16
-------
measured weight of the input material and of that of all the output material are attributable in part to
process loss, moisture loss, and/or variation in equipment weights. For a field test of this nature, the
closure of the input/output material balance to within about 10% denotes an accurate material balance.
Product Quality
Waste Composition-
Using Table 5 data, the relative purity of the primary process output streams is depicted in
Figure 5, which illustrates that stream purity decreases in successive downstream unit processes. Of
.the 29 samples collected and sorted, the average sample weight was approximately 25 kg (54 Ib).
Except for the soil fraction, impurity concentrations were relatively high. Note that the typical raw waste
composition assumed in Florida for the mid-1970s contains 16% yard waste (Table 2) and may not be
representative of wastes nationwide for the same time period. Table 6 illustrates waste decomposition
in landfills by comparing assumed raw waste with field data. Figure 6 presents the mean values, 90%
confidence intervals, and maxima and minima for the target component in the soil, plastics, and ferrous
fractions. Aluminum was not isolated during the test because of inappropriately selected recovery
equipment. As shown by the figure, the soil fraction exhibits the least variability of the fractions; based
on inert content, its purity consistently exceeds 90%. The purity of the ferrous stream exceeds 70%
(See Table 5).
CD
I
I
£
100
90-
80-
70-
60-
50-
40-
30-
20-
10-
0-
Soil
S1
Ferrous Plastics Alum/Res.
S3 S2 S4/S5
Output Stream Fraction
I I Ferrous [77^ Alum |:;x;x;| Plast
[//;/] inerts pT^T] other Legend
Figure 5. Composition of process output streams.
17
-------
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18
-------
TABLE 6. COMPOSITION OF FLORIDA RAW WASTE AND COLLIER COUNTY MINED MATERIAL
Florida Waste Composition (a) Collier County Landfill Mining (b)
Component % by Weight
Paper 37.0
Glass 10.6
Plastic 1 .6
Metal 9.6
Yard Wastes 15.6
Food Wastes 15.2
Wood Wastes 1.6
Other
Rubber
Textile
Inerts
Non-processibles
Unidentifiable
Subtotal 8.8
Total 100.0
% by Weight
3.0
2.1
4.3
2.4
2.0
0.0
5.2
0.6
0.9
59.1
18.0
2.5
81.1
100.0
Notes:
(a) Broward County, Florida, 1976. Typical for 1970's.
(b) Average Material Balance. See Figure 7.
19
-------
100
90
80
70
-. 60
£
| 50
^ 40
30
20
10
0
Target Compo
Stream Numbt
Stream Detcrl
0 n
i-^
— I
j. l
i i i > i
nent Soil Plastics Ferrous
»r S1 S2 S3
ptlon Soil Fraction Plastic Fraction Ferrous Fraction
Figure 6. Variation in composition of potentially
recoverable target components.
Laboratory results for samples from all fractions (e.g., S1 through S4/S5) indicate that several
parameters fail to satisfy the project acceptance criteria for accuracy of results. In the soil fraction,
results for fecal streptococci, phosphorus, and mercury exhibited standard errors ranging up to +/-
60.5% of the mean. Results for proximate analysis ranged up to +/-92% for all fractions tested. All
results for the residue stream were more widely variable than the other streams, with results that
showed up to 91.9% variation. Since all available samples were tested, and the possibility of additional
sampling wasprecluded by the disassembling of the separation system, the sub-standard results were
accepted and are noted as such in Table 7.
Using field data, a material balance for a feedstock of 907 MT (1000 tons) of mined materials is
illustrated in Figure 7. The estimate presented in this figure for the feed stream was calculated based
20
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TABLE 7. SUMMARY OF LABORATORY RESULTS FOR THE PRIMARY PROCESS STREAM FRACTIONS
Parameter
Number of Samples (a)
Results Reported on (Fraction)
Fraction Weight % of Sample
FUEL CHARACTERISTICS
Proximate Analysis (as received)
-Ash
-Moisture
-Volatile Matter
—Fixed Carbon
Heating Value (dry basis)
Ultimate Analysis (b)
BACTERIOLOGICAL ANALYSIS
Total Coiiform
Fecal Coiiform
Fecal Streptoccocci
E. Coli
%
%
%
%
kJ/kg
Btu/lb
cfu/g
cfu/g
cfu/g
-
Soil (S1) Plastics (S2)
4-7 4-5
(millable)
97.6%
38.3
28.4
31.1
2.241600
>23
406.5
(a)
Ferrous (S3) Alum (S4) Residue (S5)
4-5 4 4-5
(millable) (non-millable) (millable)
36.3% . 88.7%
29.0 - 26.3
16.0 - 35.2
51.5 - 37.0
3.48
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on the principle of conservation of massio and on measured data. In the balance, the soil fraction
averages 59.4% of the feed by weight. The two ferrous fractions and the plastics fraction average
1.7%, 0.1% and 2.4%, respectively. Thus, at least 63.6% by weight of the feed could potentially be
recovered for reuse. Non-processible (oversized) material averages 18.0% of the input, with 14.2%
making up the remaining other fraction. Table 8 presents the percent recovery in each stream.
Analyses of the Soil Fraction-
The results of analyses presented in Table 7 show that the soil fraction contained 26% moisture
and its pH was slightly basic. Aluminum, calcium, and iron exceeded 1000 mg/kg (ppm), and asbestos
was present at a concentration of 1% to 2%. None of the 6 metals testedn that would be regulated
under RCRA through the TCLP, would exceed the regulatory level. Figure 8 compares the lab results
for the soil fraction with Florida Code 1 compost regulations for heavy metals. Relatively high
population densities of indicator organisms (e.g., Total and Fecal Coliform, and Fecal Streptococci)
were present in the samples analyzed, indicating the presence of mammalian (human or animal) waste
material.
The results also indicate that the BOD5 ranged from about 714 to 1,100 mg/kg (ppm) and that
the COD fluctuated from approximately 52,000 to 152,000 mg/kg (ppm). While these parameters are
not critical to marketability, the market's preference for high quality material and its cyclic nature could
nonetheless limit the competitive status of the product.
Aesthetically, the product looks similar to a soil and may be attractive to soil amendment
markets without further mechanical processing. Four Paspalum sp. seeds were found in
approximately 900 grams sampled. The germination of timothy seeds varied from 95.2% to 99.2% and
had a value similar to the controls, i.e., 97%. The results of the seed and germination analyses are
presented in Table 9.
TABLE 8. AVERAGE RECOVERY BY FRACTION
Fractions
Additional Aluminum/ Non-
Target Soil Plastics Ferrous Ferrous Residue Processibles
Material (S1) (S2) (S3) (S6) (S4/S5) (S7)
Plastic 4.0%
Ferrous 0.0%
Aluminum 0.0%
Inert 94.7%
42.1% 3.7%
0.0% 74.2%
4.3% 2.2%
0.0% 0.1%
0.2% 43.7% 0.0%
3.2% 1.6% 0.0%
0.0% 91.3% 0.0%
0.0% 1.0% 0.0%
Finger
Screen
Unders
(S8)
2.6%
0.5%
0.0%
0.5%
Air Knife
Heavies
(S9)
3.7%
20.5%
2.2%
3.7%
10
11
Conservation of mass requires that the sum of the masses of the output streams plus losses, if
any, must equal the sum of the masses of the input streams.
Selenium and silver were not tested.
23
-------
300*1
200-
Q.
Q.
100-
; Florida Regs.
Soil Fraction (S1)
Cadmium Lead Mercury Zinc Chromium Nickel Copper
Metals
Figure 8. Comparison of metals in soil fraction with Florida compost regulations.
TABLE 9. COLLIER COUNTY - RESULTS OF SEED AND GERMINATION
ANALYSIS OF SOIL FRACTION
Test No.
1
2
3
4
5
6
7
8
Seed Analysis
Type
one F'aspalum sp.
none
none
none
none
one Paspalum sp.
none
two Paspalum sp.
Sample
(g)
105
108
108
124
123
121
109
106
Size
(oz)
3.7
3.8
3.8
4.3
4.3
4.3
3.8
3.7
Germination (%)
Sample
99.2
99.2
98.2
97.2
95.2
98.2
97.2
96.2
Control
97
97
97
97
97
97
97
97
24
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The organic content and nutrient value of the soil fraction are compared with a variety of MSW
composts and compost feedstocks in Table 10. The recovered soil has very low volatile solids content
(6.6%, dry weight). Further composting of the soil product will not further stabilize the soil fraction
because of its high mineral content. Also, Table 10 indicates that the volatile solids content of mature
compost tends to stabilize at a much higher value (about one order of magnitude) than the recovered
soil product.
These characteristics taken in total indicate that the soil fraction from this demonstration could
be used as a soil conditioner.
Table 10 indicates concentrations of nitrogen, phosphorus, potassium (NPK) and other
analyses for manure, peat, MSW derived compost and the Collier soil fraction. The comparatively low
nutrient value of the soil fraction, as measured by NPK, would limit its competitiveness in traditional
compost markets. Also, the soil fraction from other sites may have very different NPK values.
Depending on market and regulatory conditions, the soil fraction could be used to add bulk
density to materials such as peat and compost. The soil product could be used in landfill closures and
subgrade fill. In Edinburg, New York, the soil fraction was awarded a beneficial use determination,
permitting additional uses, (e.g., subgrade fill when not in contact with ground water off-site).
Incomplete separation would not hinder the use of the soil fraction in landfill closures and subgrade fill
as severely as it would possible uses of ferrous, plastic or aluminum streams.
The most important market for the soil fraction is as landfill cover. Collier County has
successfully used the mined soil fraction as cover. A sample of the soil fraction was examined by a
representative of the State of Connecticut Agricultural Experiment Station in New Haven. Preliminary
visual analysis indicated that the material appeared marketable, but that a growth test over a growing
season would be required to determine the soil's actual marketability as a compost product. The
evaluator noted that, based on the soil tests, the material would have "little difficulty" growing plants,
but that the source of the soil (a landfill) might limit its perceived value. Note that this evaluation was
based on Collier soil fraction only, and results will be highly variable site to site.
Analyses of the Blended Aluminum/Residue Fraction-
The heating value of the blended aluminum/residue fraction was about 14,514 kJ/kg (6,240
Btu/lb). The fraction also had a moisture content of about 35%, very high BODg and COD, and four
metals (aluminum, calcium, ferrous, and manganese) that exceeded 1000 mg/kg (ppm).
Table 11 summarizes the size distribution of the aluminum/residue fraction, based on the
results of sieve analyses conducted on four samples. Size data are needed for energy recovery to
determine if the material should be shredded prior to burning. More than 40% of this fraction exceeds
20 cm (8 in.), and more than 60% exceeds 2 cm (3/4 in.).
Air Quality Monitoring
Table 12 summarizes the results of the air quality monitoring program for the coarse screen
and the trommel, respectively. Dust, fibers, and metals were observed to be present in minor
concentrations well below the applicable time-weighted average (TWA) permissible exposure limits.
Upstream calcium, likely originating in the cover material, was observed at levels below 0.3% of its
permissible exposure limit. Microbial agents were measured throughout the sampling program as
would be expected for landfilling operations.
25
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TABLE 10. COMPARISON OF COLLIER COUNTY SOIL FRACTION WITH
MSW COMPOST AND OTHER PRODUCTS
Component
Soil (a)
Fraction
Compost Projects
Compost (c)
Feed(b) A B CD
Other Products
Manure Peat
Moisture (%)
26% 54% 37% N/A N/A N/A N/A N/A
Volatile Solids (%, dry) 6.62% 75% 56% N/A 6% 6% N/A N/A
Nitrogen (%, dry) 0.15% N/A N/A 0.98% 1.51% 1.73% 3.50% 1.50%
Potassium (%, dry) 0.04% N/A N/A 0.13% 0.64% 0.57% 2.50% 0.04%
Phosphorus (%, dry) 0.02% N/A N/A 0.25% 0.24% 0.27% 1.50% 0.04%
PH
Particle Size
7.22 N/A N/A N/A N/A N/A N/A N/A
<2cm N/A N/A N/A N/A N/A N/A N/A
NOTES:
(a) MITE Evaluation soil fraction
(b) Average properties of compostable fraction of municipal solid waste from 2 projects.
(c) Compost analyses:
A: Average properties of MSW/sludge co-compost produced from the waste in "Feed" column.
B: Average properties of MSW compost from two Minnesota projects.
C: 36 day old MSW-derived compost, as measured at Tuscany, Italy.
D: 88 day old MSW-derived compost, as measured at Tuscany, Italy.
26
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TABLE 11. COLLIER COUNTY ALUMINUM/RESIDUE FRACTION - PARTICLE SIZE CHARACTERISTICS
Particle Size Range
X > 20 cm (8 in.)
7.5 cm (3 in.) < X < 20 cm (8 in.)
2 cm (3/4 in.) < X < 7.5 cm (3 in.)
30 mesh < X < 2 cm (3/4 in.)
50 mesh < X < 30 mesh
X < 50 mesh
TOTAL
Percent
By Weight
40.6
16.5
3.3
11.5
10.6
17.5
100.0
Cumulative %
Retained By Weight
40.6
57.1
60.4
71.9
82.5
1QO.O
Downstream samples of both the coarse grizzly screen and the trommel suggest an increase in
nuisance dust and calcium. Lead was discovered in four downstream samples, at less than 5% of the
TWA permissible exposure limit. Copper was found in one sample, at less than 2% of the TWA
permissible exposure limit. One gypsum fiber was detected. Elevated total bacterial counts were
observed downstream of both the gri2:zly and the trommel, with a greater frequency downstream of the
trommel.
Additional Results
Additional measurements of particle size, adhering dirt, and bulk densities were taken to assist
in estimating the composition and recyclability of various materials. Table 13 reports the size
distribution of the glass particles recovered through hand-sorting all streams on April 23. Nearly 55%
was retained on a 2 cm (3/4 in.) screen and about 38% was retained on a 1 cm (3/8 in.) screen. The
percentages by weight of dirt adhering to the glass and aluminum fractions accumulated during the
manual sort are presented in Table 14. The dirt adhering to glass particles is about 16% of total weight
and indicates the magnitude of the weight percentage of dirt that adhered to the other waste
components sorted during the field work. The higher percentage of dirt in the aluminum cans (i.e.,
61% of total weight) can be attributed to the entrapment of dirt in the cans during the burial and
compaction operations. Bulk densities calculated for several key output streams are presented in
Table 15.
27
-------
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Table 13. COLLIER COUNTY - GLASS SIZE DISTRIBUTION
Fraction
Input
3/4"
3/8"
Pan
Total:
Mass Balance Closure:
Recovered Tare
Material (a) Weight
(kg) (kg)
7.73 1.8
5.02 1.8
4.06 1.8
2.23 1.8
5.86/5.91 =
Net Weight
Retained
(kg)
5.91
3.2
2.24
0.42
5.86
99%
% by Weight
Retained
0.0
54.6
38.2
7.1
100.0
Passing
100.0
45.3
7.1
(a) Sample weights as recovered from various streams.
Test date: 23ApriM992.
TABLE 14. GLASS AND ALUMINUM FRACTION - ADHERENT DIRT
Recovered Tare
Material (a) Weight Net Weight
Fraction (kg) (kg) (kq)
Glass 6.8
Dirt 0.93
Input Total: 7.73
Aluminum (50 cans) (b)
Dirt
Input Total:
1.8
N/A
1.8
5
0.93
5.93
0.9 (approx.)
1.4
2.3
%of
Total
By Weight
84.3%
15.7%
100.0%.
39.1%
60.9%
100.0%
(a) Sample weights as recovered from various streams.
Test date: 23 April 1992.
(b) Based on 55 cans/kg to account for heavier 1970's
aluminum can weight.
TABLE 15. BULK DENSITIES OF PRODUCT STREAMS
Bulk Density, kg/ms
Stream
No.
(S1)
(S2)
(S3)
(S4/S5)
Material
Soil
Plastics
Ferrous
Metal
Aluminum/
Residue
No. of
Samples
4
1
2
2
Mean
1160
212
294
260
Sample
Standard
Deviation
62.5
-
20.8
46.5
29
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SECTION 4
MARKETS FOR RECOVERED MATERIALS
DESCRIPTION
General
This section of the report reviews markets for materials recovered through landfill mining.
Since efforts to develop markets for these landfilled mined products are in their developmental stages,
this section identifies those materials with potential marketability, and then reviews the markets for
those materials from the perspective of traditional source separated material markets. Figure 9
identifies potential uses of various recovered material categories.
Material Quality Requirements
The quality of mined materials must be similar to that of source-separated recyclables before
reliable markets will exist for mined materials. Summarized below are non-quantitative market quality
requirements for ferrous, aluminum, and plastics . secondary materials recovered from source
separated material recycling programs. Markets may revise requirements to address mined materials.
Tin Cans
Ferrous Scrap,
Aluminum, or Mixed
Plastics
Baled to density defined by the detinning or mini-mill market,
with non-ferrous contaminants removed to mark-specific purity
level.
Baled, and meeting market-specified purity levels.
Since source-separated recyclables are currently cleaner than mined materials, it can be
assumed that the degree of processing or scrutiny at the market will be greater for the latter.
Previous Mined Material Marketing
Since August, 1990, Collier County has sent scrap ferrous to a local scrap dealer for positive or
negative revenue, depending on the overall market strength. The dealer reports that the material has
"no value" due to the costs to clean and further separate the dirt, paper, rags, and other waste
materials delivered with the ferrous (G. Harris, Tampa Scrap, personal communication, 1992).
MARKET DEMAND CONDITIONS
To investigate the marketability of mined recyclables, the subcontractor contacted a limited
number of possible buyers. Samples were sent to each buyer's representative. The representatives
30
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Technically Feasible
Use by Industry
Sorted Material Categories
Waste Industry
Fuel I Cover
General Industry
Feed-
Soil I stock I Reuse
Current Marketability
Industry
Market
Potential Comment
Food
Yard
Wood
Paper and Paperboard
Rubber and Leather
Textiles
Plastics
Ferrous
Aluminum
Other Non-Ferrous
Glass
Inerts
Unidentified
Non-Processible
None
None
None
None
None
None
Poor
Poor
Poor
None
None
Good
None
None
Small clumps
Oxidized, dirty
Oxidized, dirty
Shards
NOTES: 1. Use Key:
Potential use for excavated materials
Potential use for traditional recycled materials
No potential use
Figure 9. Estimated market potential for mined materials.
were queried as to the material quality requirements and the reaction to the samples. No
representative felt that materials were attractive as received. Representatives commented that the
mined materials would require extensive cleaning and pre-processing before they could be competitive
with their source-separated counterparts. Product quality could be improved through additional
processing conducted at the landfill mining site or at a materials recovery facility (MRF). Section 3
discusses the marketability of the soil fraction.
MARKET BARRIERS
Market demand for recyclables is influenced primarily by the strength of demand for the end
product, the availability of plant capacity to absorb the secondary materials, the ease with which
recycled materials can be substituted for virgin raw materials in the manufacturing process, and the
relative costs of manufacturing with recycled versus raw materials. Table 16 summarizes general
market barriers for source separated recyclables.
While the constraints listed in Table 16 are relevant to both source separated and mined
materials, the primary market barriers that specifically affect mined material will involve purity of the
recovered product. In secondary materials markets, mined recyclables would be subject to the
barriers listed in Table 16.
31
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TABLE 16. GENERAL MARKET BARRIERS FOR SOURCE SEPARATED RECYCLABLES
Material
Barriers Affecting Materials Demand
Tin Cans & Ferrous Scrap
Aluminum Cans
Plastics
Soil/Compost
• Weak end product demand for finished steel
• Limited productive capacity of economically
accessible mini-mills
• Inability of tin cans to substitute for scrap
• Seasonal aluminum can demand affected by the
overall economy
• Low-grade alloy resulting from mixing barrels and
ends of used aluminum cans
• Low-value and limited applications of plastic lumber
products
• Need for separation by resin
• Low virgin PET & HOPE prices
• Technical sorting/recycling problems and non-
specific markets for film and other plastics
• Low quality, visually unappealing compost
32
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SECTION 5
REGULATORY IMPACT
INTRODUCTION
This section of the report reviews regulations that apply to both landfill mining activities and
product quality. A review of regulations applicable to landfill mining was undertaken in states with
pilot/commercial landfill mining projects.
The principal product from landfill mining, in terms of both quantity produced and number of
projects actively recovering this material, is the soil fraction. To permit its use as landfill cover, review
by state permitting authorities would likely be required. Florida permits Collier County to apply the soil
fraction as cover. Cover requirements vary among the states, but it is likely that since the material is
derived from the landfill, regulators would be amenable to its reuse as cover. To permit the soil fraction
to be competitive with aerobically prepared compost, it must meet the regulatory requirements for
compost as none exist for recovered soil.
The reuse of other recovered materials would not be regulated under solid waste laws,
although provisions of OSHA, commerce and other regulations could apply.
REVIEW OF APPLICABLE FLORIDA REGULATIONS
Process Related Regulations
On March 18, 1992, Florida promulgated draft regulations containing a rule governing the
mining of solid waste (Florida Administrative Code Chapter 17-701.710). Subsequently in 1992, the
draft landfill mining rule was eliminated from ACC 17-701 since only Collier County had expressed
interest in applying the technology.
Landfill mining cannot be undertaken without authorization through a Florida Department of
Environmental Regulation (DER) landfill operations permit. Specific requirements result from
consultation between the applicant and DER.
Product Related Regulations
Florida Administrative Code Chapter 17-709, Criteria for the Production and Use of Compost
Made From Solid Waste, which was promulgated on November 21, 1989, specifies that the following
characteristics define compost: type of waste processed, product maturity, the amount of foreign
matter in the product, the particle size and organic matter content of the product, and the
concentration of heavy metals. Florida regulations define foreign matter content in three categories
approximately as follows (17-709.550(1 )(c)): less than 2% dry weight; 2% to 4% dry weight; or 4% to
10% dry weight. Particle size and organic content are defined approximately as follows (17-
33
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709.550(1 )(d)): fine (<10mm, and an organic matter content of >25%); medium (<15mm, and an
organic matter content of >30%); coarse (<25mm, and an organic matter content of >35%).
In addition, compost is classified according to heavy metal concentrations, with Code 1 having
the lowest concentration of heavy metals and Code 4 having the highest (17-709.550(1 )(e)). Table 17
presents the heavy metal criteria for all four codes. Table 18 contains the classification and allowable-
use criteria that are applicable to MSW recovered as a part of a landfill mining operation (17-709.550(2)
& 17-709.600(1, 2, 3, & 4)). The Collier soil fraction separated at the MITE project would satisfy Code 1,
Type C compost requirements, because the foreign matter content could not meet higher use classes.
TABLE 17. FLORIDA'S HEAVY METAL CRITERIA FOR COMPOST
Concentration within Each Code
(mg/kg dry weight)
Parameter
Cadmium
Copper
Lead
Nickel
Zinc
Code 1 Code 2
<15 15-<30
<450 450 - <900
<500 500 -< 1,000
<50 50-<100
<900 900 -< 1,800
CodeS
30-100
900 - 3,000
1,000-1,500
100-500 '
1,800-10,000
Code 4
>100
>3,000
> 1,500
>500
> 10,000
Reference: FAC Chapter 17-709.550(1 )(e)
In 1990, the County Transportation Services Division asked that the DER allow soil material
excavated from the Naples Airport Landfill to be used as embankment material. The DER denied the
request because "post processing of waste/soil material, regardless of testing, can not guarantee that
some portion of the soil/waste in question will not cause an environmental or public health problem
when released outside a landfill." The DER specified that waste/soil from both the Naples Airport
Landfill and the Naples Landfill "should not be disposed or used (initial landfill cover) outside of a lined
landfill" (Correspondence, Florida Department of Environmental Regulation to Colljer County
Transportation Services, 1990). The State of New York, however, has permitted the use of excavated
soil as subgrade on off-site projects not exposed to high ground water.
NEED FOR ADDITIONAL REGULATIONS
No regulations at the Federal level currently exist for landfill mining operations. Uniform
regulations among the states would promote and encourage the industry, but few data are available on
which to base such regulations. Since the economics of projects do not clearly establish that this
technology will enjoy wide application, it seems premature to develop federal regulations at this time.
States generally have a method for modifying an existing permit, and this permit modification approach
has been applied to all projects undertaken thus far.
34
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TABLE 18. FLORIDA COMPOST CLASSIFICATION AND ALLOWABLE USE CRITERIA
Type Maturity
A mature
B mature/semi-
mature
C mature/semi-
mature
D fresh
E
Particle Foreign Metal
Size Matter Concentration
fine <2% Code 1
fine/medium <4% Code1/Code2
fine/medium/ <10% Code 1 /Code 21
coarse Codes
fine/medium/ < 1 0% Code 1 /Code 2/
coarse Code 3
Code 4
Allowable
Use
unrestricted distribution
public park
commercial,
agricultural,
institutional,
governmental
operations
commercial,
agricultural,
institutional,
governmental
operations
landfills or at
landfill reclamation
disposed of as per
Chapter 1 7-701
Notes:
As mentioned in the discussion of landfill-mining process-related regulations, draft rule
17-701.710(3) specifies that waste and soil mixtures capable of passing through a 1-in.
screen may be used as initial cover at lined landfills.
Reference: FAC Chapter 17-709.550(2) and 17-709.600(1, 2, 3, & 4).
Excavated material awaiting processing could potentially release leachate to the environment if
exposed to precipitation. State regulators need to recognize this condition and consider control
methods (e.g., limit stockpile size, or require temporary cover, etc.). Regulations for the quality and use
of the soil product should be developed.
35
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SECTION 6
ECONOMIC EVALUATION
GENERAL
The costs for the Collier County MITE demonstration project are developed in this section of
the report. The following subsection presents estimates of the capital and operating costs of the
project, and summarizes project economics in terms of unit costs.
COST ESTIMATES
Capital Costs
Capital investment to conduct the MITE demonstration project was relatively low since the
County was able to lease or borrow processing equipment, and to reassign landfill equipment
temporarily from other duties. Funds for the demonstration were provided by the Ford Foundation, as
a result of the selection of this project as a 1990 "Innovations" award from the Kennedy School of
Government at Harvard University. The expenditure was limited to $40,000 for this project. This
approach to securing equipment may be successfully applied in a limited number of other projects.
However, to examine the economics of landfill mining projects under more conventional financing and
acquisition scenarios, capital costs were estimated for a publicly-owned system necessary for a similar
project.
Capital cost estimates are based on the following assumptions:
• estimates are discounted at 8% to January 1992 dollars,
• mobile mining and portable process equipment are purchasedfs, and
• costs to set up the processing equipment, and to dismantle and remove it at the
conclusion of the mining episode, are included as a capital cost under site preparation.
Table 19 summarizes the estimated capital costs for the purchase and installation of a system
similar to that demonstrated at Collier County.
A review of Sections 2 and 3 indicates that the County demonstration system was operated
below its design capacity for most of the evaluation. 13 Further, the rate at which excavation could be
conducted, based on general construction practice, could exceed the materials processing rate. Also,
the 11.8 MT/hr (13 tons/hr) average processing rate that was achieved during the first week of the test
is substantially below the peak rate for that week of 16.3 MT/hr (18 tons/hr). Note that the finger screen
12 Leasing may be appropriate, if equipment is available.
13 The trommel and the air knife were not matched in capacity; the trommel had a higher throughput
capacity.
36
-------
portion of the air knife was observed to overload with surges of waste throughput, but it was not
possible to determine feed rates under those conditions. Based on a visual assessment of potential
capacity, the landfill mining system described in Table 19 is assumed to have a processing capacity of
63.5 MT/hr (70 tons/hr), similar to the capacity cited for the trommel when processing dry leaf compost,
if two conditions are satisfied:
• engineering design optimization of the system layout and installation, matching
equipment capacities, conveying system capacities, site arrangement and
construction, and
• an experienced crew operated and maintained the system.
The availability of such a system is assumed to be about 70%, yielding an operating capacity of
about 45 MT/hr (50 tons/hr).
The useful life of the landfill mining equipment is assumed to be 7 years, i.e., about 1800
operating days or nearly 15,000 hours. Note that mining at 45 MT/hr (50 tons/hr) for 15,000 hours
yields 680,400 MT (750,000 tons), equivalent to a 30.5 m (100 ft) high, 2 ha (15.8 acre) landfill cell with
3:1 side slopes at 771 kg/ms (1,300 Ib/yd3).
Operating Costs
The Collier County system was operated by County staff. Operating cost estimates, presented
in Table 20, are based on the following assumptions:
• estimates are presented in January 1992 dollars,
• labor overhead rates were assumed to be 25% of direct labor,
• annual maintenance cost was assumed to be 2% of capital costs,
• transportation of residue to disposal was assumed to cost $11.1 /MT ($10/ton) and
transportation of materials to markets was assumed to cost $6.6/MT ($6/ton),
• a mined material processing rate of 55 MT/hr (50 tons/hr), for 6 working hours per day,
260 days per year, and
• a 70% equipment availability.
Table 20 summarizes the estimated operating cost for a system similar to the Collier County
demonstration project.
Unit Costs
Using the cost estimates presented in Tables 19 and 20, and the test results presented in
Section 3, unit costs for a production-oriented project similar to the landfill mining MITE demonstration
are derived in Table 21, and are presented in terms of cost per MT (ton) of feed mined material, and in
cost per MT (ton) and per ms (yds) of soil fraction recovered. Note that unit costs are presented on the
basis of both actual test period throughput (12 MT/hr (13 tons/hr)) and estimated capacity (45 MT/hr
(50 tons/hr)).
37
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TABLE 19. ESTIMATED CAPITAL COSTS
Item
Cost
Site Preparation (a) $52,000
Fixed Equipment
Grizzly/Trommel, Air Knife/Destoner
Magnetic Separator, Portable Conveyors,
Generator SUBTOTAL $255,500
Mobile Equipment
Excavator, Dozer, Front End Loader,
Truck, Debris Boxes SUBTOTAL $695,000
Contingency $200,500
TOTAL (b) $1,203,000
Rounded $1,200,000
Notes: (a) Site preparation costs are based on the configuration finally adopted during
the test, i.e., 60m x 90m (200' x 300').
(b) Although no stockpiling costs were incurred during the test, in commercial
application, these costs would apply. Costs to prepare an area in which to
stockpile mined material prior to use, and equip it with a front end loader are
estimated to be $474,000 in addition to the costs shown.
TABLE 20. ESTIMATED ANNUAL OPERATING COSTS
Item
Cost
Excavation & Processing:
Labor
Direct
Overhead
Fuel
Maintenance
Product Transport and
Residue Disposal (a)
Administration
Contingency:
TOTAL (b)
Rounded
$435,760
$108,940
$48,048
$20,050
$229,320
$8,200
$170,064
$1,020,382
$1,020,000
Notes: (a) Assumes that residue is landfilled on-site @ $9/MT ($10/ton) and that
recovered products can be hauled to a market @ $5/MT ($6/ton). Note that
$9/MT ($10/ton) reflects the estimated operating cost for a sanitary landfill.
(b) Although no stockpiling costs were incurred during the test, in commercial
application, these costs would apply. Costs for a loader operator, fuel,
and maintenance are estimated to be $208,000 in addition to the costs shown.
38
-------
CO
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PROJECT
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soil fraction bas<
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Capital cost is fro
Amortization rate:
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sss
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39
-------
REVENUES AND AVOIDED COSTS
Revenues accruing to landfill mining from the sale of recovered materials have not been
established, either during the MITE demonstration project at Collier County, or at any other project.
However, positive economic benefits have accrued to projects from avoided costs, such as:
•• since Collier County purchases cover material off-site, the avoided cost of purchase of
soil for landfill cover,
• avoided costs of developing new landfill space, and
• avoided payment for waste short-fall to resource recovery system operators under a
"put or pay" contract when waste commitments cannot be met.
40
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SECTION 7
CONCLUSIONS & RECOMMENDATIONS
CONCLUSIONS
General
This section of the report evaluates the landfill mining technology, generally addressing the
process, its environmental aspects, and health and safety issues. The mass balance for the system
tested in Collier County and the product quality, measured in terms of the efficiency of the system in
concentrating target components (i.e., output stream purity), were as shown in Table 22. Variations in
system performance over time cannot be judged without periodic sampling during the course of at
least one year.
TABLE 22. MASS BALANCE AND CONCENTRATION EFFICIENCY SUMMARIES
Fraction
Non-processible
Soil
Ferrous
Plastics
Residue & other
Mass Fraction, %
18%
60%
2%
2%
18%
100%
Stream Purity, %
Not applicable
94%
82%
75%
61%
-
Process Evaluation
Technical Evaluation of the MITE Demonstration-
Based on conditions under which the MITE evaluation was conducted, landfill mining appears
to be technically and environmentally feasible for the recovery of soil that was used during the
construction of the landfill. The portable system at the Naples Landfill effectively and efficiently
recovers a soil fraction that is environmentally benign when compared to Florida MSW compost
regulations and is apparently a good! growing medium based on growth tests using timothy grass
seeds. Using the "inert" category as the surrogate for soil, recovery of soil averaged about 87% with a
purity of about 94%. The recovered soil fraction was suitable for use as cover material (including
serving as a component of a final cover) and as a soil medium for supporting plant growth. Note that
the soil is recoverable using only the coarse screen and the trommel screen operations.
41
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Including process equipment for recovering marketable or usable materials other than a soil
fraction is of questionable feasibility without substantial processing to upgrade the quality of recovered
materials. While ferrous, film plastics and aluminum are potential candidates for recovery, none of
these materials were recovered with sufficient purity during the test to render it marketable.
Ferrous recovery averaged about 78% with a purity of about 81 %. While 81 % purity exceeds
the economic criterion cited by one market, product quality is not competitive in the commercial scrap
market without secondary processing (e.g., a perforated vibratory pan and second magnetic head
pulley). A product with a purity of 95% or greater - achievable by using a high power magnetic
separator or two magnetic separators in series - would likely be marketable.
The landfill mining system yielded a film plastics product with a purity of about 75%. Much of
the film was dirt-laden and film plastic purity was too low for marketing without secondary processing
(e.g., manual sorting).
The lack of a suitable"!* aluminum separator prevented aluminum recovery. Thus, no
conclusions are offered regarding the aluminum separator. Because of the relatively large variation in
particle size distribution of- the stream and the high concentration of non-aluminum materials, the
aluminum enriched fraction from the air knife would require additional processing (e.g., a second
trommel followed by an eddy current separator) prior to injection into most aluminum separators on the
market. The aluminum concentration in the aluminum enriched air knife fraction was 5.5%; this
concentration is about one order of magnitude greater than that of the aluminum in the MSW
feedstock. About 90% of the aluminum was directed to the aluminum enriched air knife fraction. The
concentration of other materials in the target stream is also very high (i.e., 94%). Electro-mechanical
separation of aluminum from MSW typically yields a recovery percentage in the range of 50% to 60%.
Commercial Status/Demonstration Projects-
The operating history of all full scale domestic landfill mining projects represents a total
operating history of at least 500 days for these technologies.
Reliability of Equipment-
Based on an anticipated 6 operating hours per day and run-time data presented in Table 3,
availability for the process system averaged 53% for the 4 days of the field test, and reached a peak of
89%. Material recovery facilities (MRFs) typically achieve 70% or greater availability. The lower
availability during the test may have been due to the poorly matched equipment capacities.
Some portion of equipment downtime during the test was due to a hydraulic hose failure,
which was repaired by landfill maintenance personnel, and to wet weather. Processing and testing
operations were suspended during showers. Spare parts were reportedly available. The equipment
appeared to be rugged, and designed for solid wastes service. The grizzly/trommel was integral with
its flatbed trailer, although the air knife was designed for indoor rather than outdoor applications.
The Collier system presented several methods of process control: feed rate, replaceable
trommel wire mesh screens, and adjustable air flow into the air knife. Thus, the system appears to be
relatively flexible.
14 Compatible with the particle size distribution, contamination, and flow-rate.
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Adaptation to Other Feedstocks
The MITE demonstration project at Collier used a grizzly to remove non-processible oversize
materials (e.g., tires, large lumber, metal, wire rope, and film plastic), the size of which would foul or
damage the downstream trommel screen. In effect, the system downstream of the grizzly was
processing predominantly residential and commercial wastes. The Collier train is specific to a
residential landfill. While not designed to handle construction and demolition debris (C&D), the train
handled the oversize materials, which are characteristic of industrial wastes and of C&D wastes.
Although no tests were conducted to assess the efficiency of the system in handling C&D
wastes, it seems likely that similar equipment would perform as well on a variety of feedstocks. The
percentage of oversize non-processible wastes likely would be greater than that experienced during
the test, unless some form of size reduction had been applied during the original placement of the
wastes, or had occurred during decomposition and excavation, or was incorporated as an additional
processing step ahead of the landfill mining grizzly. The performance of similar equipment at other
.landfills where the concentration of non-residential wastes is greater than at Collier could be
significantly different from the results reported herein.
Decomposition in Landfills
Potential benefits of planning for mining during the design phase of new landfills include a
reduced need for future landfill siting activities and the beneficial recovery of a resource(s). Leachate
recirculation may speed decomposition and the documented placement of wastes by type may
facilitate early and convenient mining.
Environmental Aspects
General--
While the MITE demonstration did not include an environmental risk assessment, the landfill
mining operation did not appear to pose any hazards that would not normally be present at solid waste
landfilling or strip mining operations. This judgment is based on the analyses of air emissions (both
chemical compounds and microorganisms) from the operations, analyses of the chemical constituents
of the process streams, and observations of the operations. Potential environmental impacts are a
function of the characteristics of the MSW feedstock and of the processing conditions. The Naples
Landfill received mainly residential wastes, thus limiting the potential for industrial and hazardous
wastes in the landfill and their subsequent release during mining. Edinburg, New York, experience
supports the findings of minimal impacts to the environment. However, the situation at other locations
might be significantly different.
Water Quality-
Although not observed cfuring the MITE demonstration, the potential exists for the release to
the environment of leachate from re-exposed wastes or of perched leachate during excavation.
Health and Safety Aspects
Health and safety risks parallel those of a typical landfill or atypical strip mining operation. At a
minimum, the mining health and safety plan should consider the type of waste to be mined (e.g.,
residential, C&D, etc.), the potential for physical injury from rolling stock or rotating equipment;
exposure to leachate, to hazardous material or pathogens during mining or processing; subsurface
fires; landfill gas emissions; and health effects of prolonged exposure to sunlight.
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Health risks to the general public appear to be minimal. Mined materials buyers need to be
made aware of the source of the material (i.e., landfill mining rather than curbside collection).
Economics
For the recovery of a soil fraction only, the unit costs are estimated to be in the range of
$127/MT ($115 per ton) based on the results of the MITE project demonstration, including operational
expenses and amortized capital expenses.
RECOMMENDATIONS
Based on this evaluation of the Collier County project, and of the landfill mining concept and
technology in general, the following recommendations are presented:
Research
1. State-level data bases should be established to collect, verify and maintain data
regarding landfill mining technology.
2. An area of needed research is development of an economic and portable modular
system that would allow recovery of a number of marketable materials from mined
material.
3. Characterize the contents of old landfills to fully identify the range of landfill mixtures
throughout the United States. These characteristics are necessary to design
processing systems and to assess the feasibility of landfill mining. For example, the
feasibility of mining landfilled construction and demolition debris and of mining pre-
RCRA landfilled municipal wastes depends on the characteristics of the landfilled (i.e.,
degraded) materials.
4. An analysis of the environmental and health and safety aspects of landfill mining of
pre-RCRA waste disposal facilities and of mixtures with high concentrations of
industrial wastes is needed to supplement and extend the ranges of findings from the
Collier County MITE demonstration project. The Collier County project involved a
landfill of predominantly residential and commercial wastes.
Application
1. Application of the technology should be contingent upon a clear understanding of the
contents of the cells being mined.
2. The results of this study can be used as one source of data for developing operating
and performance criteria for landfill mining systems.
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REFERENCES
Landfill Reclamation Technology Transfer Information, Collier County Solid Waste Dept.
R. S. Means Company, Inc., 1992 Means Site Work Landscape Cost Data. 11th Annual Edition,
Kingston, MA, 1992.
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*U.S. GOVERNMENT PRINTING OFFICE: M93 - 7SM02/S027*
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