Here is the DRAFT document that Florida is working on instead of a
permit process. Please make any comments asap! Oh yeah, "DRAFT
DOCUMENT> DO NOT CITE OR QUOTE"!
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BEST MANAGEMENT PRACTICES MANUAL
FOR YARD TRASH MANAGEMENT
Introduction
The Best Management Practices Manual for Yard Trash Management (BMP) was
developed to provide industry-generated and peer-reviewed operating recommendations for yard
trash processing facilities in Florida. The BMP manual represents the industry's response to the
Florida Department of Environmental Protection (FDEP) challenge to operate yard trash
processing facilities in an environmentally sensitive manner without permitting requirements.
These recommendations are not rules, but rather, they are intended to serve as guidelines for
establishing industry standards. These guidelines recognize the flexibility required for the many
existing facilities and processes that create marketable products in an environmentally sensitive
manner.
This manual deals solely with the processing of two types of materials, yard trash and
clean dry wood, which have been defined as follows:
"'Yard trash' means vegetative matter resulting from landscaping maintenance or land
clearing operations and includes materials such as tree and shrub trimmings, grass
clippings, palm fronds, leaves, trees and tree stumps." [FDEP Rule 17-709.200(15)
(1989)]
"'Clean dry wood' means wood (including lighter pine), lumber or tree and shrub trunks,
branches, and limbs which is free of paint, penthachlorophenol, creosote, tar, asphalt, or
other wood preservatives and which when burned does not emit excessive visible
emissions." [Chapter 62-256.200, Florida Administrative Code (1994)]
Marketers of yard trash products generally consider yard trash as a resource, not as a
waste product, and they prefer to describe the materials with more positive terms, such as yard
trimmings. However, to avoid confusion, the term "yard trash" will be used throughout this
manual to describe the two types of materials defined above.
This manual is intended to provide the parameters for operating a facility in a safe and
environmentally sensitive manner. It is not intended to serve as an all-inclusive technical "how to"
guide on establishing and operating a yard trash processing facility.
Background
Florida's warm climate creates ideal conditions for a nine-month growing season. Heavy
applications of water-soluble nitrogen fertilizer and scheduled irrigation practices have
contributed to the growth of lush landscapes. The abundance of high-maintenance landscapes
results in the generation of more that 3.5 million tons per year of residential and commercial
landscape yard trash. (reference - FDEP annual report)
Recognizing the large volumes of organic material that were being generated, FDEP took
several measures to encourage resource recovery and recycling. In 1989, FDEP established Rule
17-709 to regulate the production and use of compost products. Any yard trash processing
facility that did not identify itself as a composting facility was not subject to the permitting and
operating requirements of Rule 17-709. The FDEP regulation dealing with yard waste
composting created confusion by exempting from the rule other types of yard waste recycling
facilities.
In 1992, in an effort to prolong the life of the state's lined landfills, Florida prohibited the
disposal of yard trash in lined landfills. This increased the need for alternative methods of
collecting and processing yard trash. Source separation of yard trash from municipal solid stream
presented a new set of opportunities and challenges for counties and cities across the state. An
increasing number of facilities were to process yard trash in a controlled, accelerated fashion
using natural processes of decomposition.
In 1995, based upon several years of operating history, FDEP acknowledged the limited
environmental risk posed by the operation of yard trash processing facilities, whether they
produce compost, mulch or other products. In the spirit of cooperation with the yard trash
processing industry and the acknowledgement of the limited environmental risk associated with
yard trash processing facilities, FDEP proposed removing the permitting requirements for yard
trash composting facilities. FDEP will continue its enforcement authority for any yard trash
facilities that operate in a manner that could cause an environmental problem or do not provide
for the timely movement of material off site. (See Appendix A: FDEP Policy Memorandum, May
10, 1995 by Solid Waste Administrator John Rudell)
Notes
1. United States Environmental Protection Agency Focus Meeting On Compost Quality and
Facility Standards. Minneapolis, Minnesota: 1991. 4-13.
2. Ruddell, John. "Memo to Waste Program Administrators," Florida Department of
Environmental Protection., Tallahassee, FL. 17 May 1995.
3. Composting Council. Compost Facility Operating Guide. 1st Edition, Alexandria, 1994.
Glossary. Appendix A.
4. Florida Department of Environmental Protection Bureau of Solid Waste Division of Waste
Management. Solid Waste Management in Florida. Tallahassee: State of Florida, 1995. 33.
5. Kashmanian, Richard. "Quantifying The Amount Of Yard Trimmings To Be Composted In
The United States In 1996." Compost Science & Utilization Summer 1993: 22.
6. Fla. DEP Solid Waste Management in Florida. ix
CHAPTER 1
FLORIDA YARD TRASH COMPOSITION AND CHARACTERISTICS
Florida MSW Composition
Mild year-round temperatures, lush vegetation and an abundance of natural resources
make the Sunshine State an ideal location for 14 million citizens, with new residents arriving at
the rate of about 1,000 per day. In addition, 37 million tourists visit Florida each. This rapid
growth in population has placed pressures on the management and disposal of about 65,000 tons
of solid waste generated per day. In fiscal year 1994, Florida's waste stream totaled 23.5 million
tons, of which yard waste represented 14.8%, or about 3.5 million tons. See Figure 1 (Fla MSW
Composition, figure 7 of 1994 DEP annual report.)
On the local level, an important first step in planning and building a yard trash processing
facility is to determine the annual volume of yard waste in the local solid waste stream.
This information is essential to make the following strategic decisions:
Site location and size
Site design
Selection of processing alternative
Selection of equipment size and type
The most common method of determining the tonnage of yard waste available is through
the use of a waste composition study that provides the percentage of yard waste in the solid waste
stream. Although the statewide average for yard trash in 1994 was 14.8%, the percentage varies
by location.
Another method of determining yard trash volume within the solid waste stream is to
study generation-rate data from the source of collection. Factors that affect generation rates
include:
Population density
Demographics
Seasonal fluctuations
While yard trash composition studies indicate the total amount of yard trash in a
community, capture rate forecasting is necessary to determine how much is likely to be recovered
for processing. In general, yard trash composes between 15% and 20% of the solid waste stream
on an annual basis and may be as high a 50% during the summer growing season. Communities
that have segregated curbside collection of yard trash can expect to receive 60-80% of the total
yard waste generated. Communities that do not offer curbside collection of segregated yard trash
but provide drop-off sites can expect to receive between 10% and 25% of the total yard trash
generated.
Florida Yard Trash Composition by Region
While a solid waste stream composition study provides information on the percentage of
yard trash in the waste stream, it is important to also study the composition of the yard trash
component of the waste stream. This information will identify the feedstocks available for mixing
and blending in the process of producing the final product. Because of the diversity of the
vegetative materials grown in the northern, central, and southern regions of Florida, a regional
yard trash composition study is recommended. See Figure 2 (chart of Pinellas Co. composition).
Weight and Volume Characteristics
A facility operator needs to know the weight and volume characteristics of different types
of yard trash feedstock. The density of various components of yard trash is dependent on the
degree of compaction, moisture content, and the bulk density of the material. Table 1 shows the
most common reported densities.
Table 1. Landscape Waste Densities (lbs./cu.yd.)
_________________________________________________________________
Loose Compacted
Leaves 200 400
Grass 400 800
Brush 300 900
_________________________________________________________________
Source: Illinois Dept. of Energy and Natural Resources.
A knowledge of the bulk density ranges is important due to their effect on the operational
parameters of production, inventory, and shipping. The weights presented in Table 2 are typical
weights based on the experience of St. Petersburg, Florida.
Table 2. Bulk Density In Stages of Processing for Yard Waste Material (lbs./cu.yd.)
_________________________________________________________________
Feedstock Processing Stage Weight
_________________________________________________________________
Mixed compacted yard trash before grinding 500-550
Loose mixed brush before grinding 100-250
Mixed yard waste after grinding 350-400
Mixed logs only after grinding 450-550
Mulch 60 days old after windrowing 550-650
Screened compost after windrowing 800-1000
_________________________________________________________________
Note: The densities are a function of particle size from processing equipment, age, processing
method, moisture content, and compaction.
Notes
1. Florida Department of Environmental Protection Bureau of Solid Waste Division of Waste
Management. Solid Waste Management in Florida. Tallahassee: State of Florida, 1995. 9
2. United States Environmental Protection Agency. Characterization of Municipal Solid Waste in
the United States: 1994 Update
3. Hodges Alan, Clouser Rodney, and Degner Robert. Yard Waste Management A Planning
Guide for Florida :Financing and Costs for Yard Waste Composting in Florida, Draft Version.
Gainesville: Cooperative Extension Service Institute of Food and Agricultural Sciences University
of Florida
4. Koraun, Edwin A., M.S. "Solid Waste Management: An Investigation of the Potential For
Recycling Yard and Vegetative Waste as Mulch or Compost in Brevard County". Report to
Brevard County Utility Services Solid Waste Division. October 1990. 30.
5. M. LaRue Robinson. "Results of Pinellas County Grass Clipping Recycling Program".
University of Florida, Pinellas County Cooperative Extension Service.
6. Illinois Department of Energy and Natural Resources, Office of Solid Waste and Renewable
Resources. Management Strategies for Landscape Waste. Springfield: September 1989. 12.
7. Ragsdale, James V. and Stasis, Peter. "Yard Waste Composition and Effects on Compost and
Mulch Production" Proceedings Second United States Conference on Municipal Solid Waste
Management, Arlington, 2-5 June 1992..
8. Illinois Department of Energy and Natural Resources, Office of Solid Waste and Renewable
Resources. Management Strategies for Landscape Waste. 11.
9. Rynk, Robert. ed. Appendix A. On Farm Composting Handbook. Ithica:Northeast Regional
Agricultural Engineering Services. 1992. 106-113.
10. Barkdoll, Ann W. and Nordstedt, Roger A. Cooperative Extension Service Institute of Food
and Agricultural Sciences University of Florida and Florida Department of Environmental
Regulation. Yard Waste Management a Planning Guide for Florida. Draft.
CHAPTER 2
YARD WASTE RECYCLING ALTERNATIVES
Solid waste management in Florida primarily consists of landfilling, incineration, recycling,
and source reduction activities. Options for yard trash management primarily include composting,
mulching, fuel production, direct land application, and landfill cover amendment.
Composting
From a solid waste management perspective, yard waste composting can greatly reduce
the amount of solid waste which requires disposal. Composting can be a cost effective and
environmentally sensitive way to dispose of a community's yard trash. Composting is a method of
solid waste management whereby the organic component of the waste stream is biologically
decomposed under controlled conditions to a state in which the compost can safely be handled
stored and applied. Quite simply, composting is a biological process in which microorganisms
convert organic matter into a soil-like material which has many horticultural benefits.
Controlled decomposition occurs as the result of a multitude of macro- and
microorganisms. Bacteria, fungi, and actinomycete are the primary organisms involved in
decomposition. In order to grow and multiply, microorganisms have four requirements: carbon,
an energy source; nitrogen, a protein source; moisture; and oxygen. Enzymes, produced by
bacteria, assist in the breaking down of complex carbohydrates into simpler forms which bacteria
can use for food. The nutrients that become available during decomposition remain in the
compost within the bodies of the new microorganisms and as humus.
The composting process does not stop at a specific point but continues to break down
until the remaining nutrients are consumed by the last remaining organisms and until most of the
carbon is converted into carbon dioxide and water.
Compost is considered stable when it has reached the requirements of its end use, with
common indicators being a respiration rate where the demand for oxygen by the microbes is
reduced; compost piles that don't reheat when moisture and oxygen are reintroduced; and the
smell is earthy and not pungent. The point at which the active composting stage should be
stopped depends on the ultimate use for the compost, on how soon it will be used, and also on the
available space at the compost site. (p. 60, On Farm Composting Handbook).
Compost has many beneficial uses. Compost improves soil aeration, soil drainage, the
water-holding capacity of sandy soils, the percentage of organic materials in soils, and the ability
of soils to absorb and hold nutrients.
Mulching
Another method of solid waste management is the recycling of yard waste into mulch.
Mulch may be considered any material applied to the soil surface for protection or improvement
of the area covered. Mulches frequently are applied around plants to modify the soil environment
and enhance plant growth.
The production of mulch generally requires less time, less land, less quality control, less
windrow processing, minimal screening, and lower cost compared to the production of compost.
The benefits of mulch are prevention of water loss from the soil by evaporation, weed
suppression, uniformity of soil temperature, improvement of soil structure, and enhancement of
landscape appearance.
Fuel Production
Processing yard trash for fuel is similar to composting and mulching. Fuel produced from
yard trash, also known as biomass fuel,is a valuable renewable energy resource. One of the most
important benefits of fuel production is that it provides a major market for the large volumes of
yard trash generated in Florida.
Fuel production is a relatively low-cost option that frequently requires only size reduction
and distribution. Screening the material to remove the fines and contaminants may be required by
the end users.
Direct Land Application
Direct land application of vegetative matter is a traditional method of recycling farm-
generated wastes. For present-day farmers, land application of yard trash can be a method of
improving soil quality of farm land. Although yard waste has relatively little nutrient content, its
principal benefit to agricultural is the addition of organic matter to the soil at little or no cost.
Another benefit is that direct land application is less costly than composting or mulching because
less material processing is required.(2)
Direct land application of yard trash to cropland should take into consideration the timing
of the application, nutrient needs of the crop, nutrient availability of the waste, C:N ratio, storage,
weather, and pollution control.(3- check page in cite.) Special consideration should be given to
the removal of common contaminants in yard trash, such as plastics, glass, and metals.
Other considerations are equipment needed for application and incorporation; size
consistency and manageability; and weed seed content.
Direct land application should only be considered a viable option when the material is
incorporated into the soil for a sufficient period of time to allow for decomposition prior to
planting crops. Yard trash should be spread after harvesting an existing crop, or on a field that is
to lie fallow for a season.(4) The decomposition process of the direct-land-applied material will
result in utilization of nitrogen already in the soil. If a crop is planted before the yard trash has
sufficiently decomposed, nitrogen utilization during the degradation process can negatively affect
plant health and growth.
Landfill Cover Amendment
An important use of yard trash is for landfill cover amendment. The addition of yard trash
provides an economic advantage of cost avoidance from reduced cost of cover dirt and avoidance
of post processing costs for screening and distributing.
To be acceptable as daily and intermediate landfill cover the Florida Department of
Environmental Protection requires processed yard trash meet the following prerequisites (1) act as
a fire barrier, (2) control litter, (3) control vectors and (4) reduce rainfall infiltration.
Specifications for daily cover at the landfill may be achieved when yard waste undergoes a
compost management process of 90 days which includes size reduction, windrowing, irrigation
and temperature monitoring. After 90 days the fully composted yard trash is blended at a 50/50
ratio of compost to soil and delivered to the landfill for daily cover. Post-process screening is not
required however, FDEP requires that 90 percent of the finished product pass through a 3/4 inch
screen size. Testing to meet this parameter is conducted on an annual basis.
To be considered as intermediate cover, fully composted, 90 day old yard waste is
processed through a trommel screen with a 1/2 inch size opening. FDEP specifies that the
compost be blended at a 75/25 percent ratio of compost to soil. Following blending the
intermediate cover is delivered to the landfill, dropped at designated locations and spread with a
bull dozer.
Another landfill use of recycled yard trash is in the renovation of turf throughout the
landfill. Fertilizer is sometimes blended in with the compost and is applied by a manure spreader.
Firewood
While Florida experiences mild winter months, a demand exists for use in-home fireplace.
In addition to being aesthetically appealing, a fireplace is a low cost supplement to more
expensive heating fuels.
In the production of firewood from yard trash, factors that should be considered include:
moisture content, wood variety, and Btu value. Dry wood is considered to have no more than 20-
25% moisture and may take up to two years to adequately dry.
References
1. Twitchell, Mary. Building A Pole Woodshed. Garden Way Publishing bulletin A-42. Pownal,
Vermont. Srorey Communications. 1980. 1,2.11,12,31.
(2) Rynk, Robert. On-Farm Composting Handbook. Ithaca, N.Y.. Northeast Regional
Agricultural Engineering Service. 1992. 103.
(3) Rynk, Robert. On-Farm Composting Handbook. 103.
(4) Illinois Department of Energy and Natural Resources. Management Strategy For Landscape
Waste. Springfield. 1989. 45.
(5) Kashmanian, R.M., H.C. Gregory, and S.A. Dressing. "Where Will all the Compost Go?"
BioCycle October 1990. 38-39,80-83.
CHAPTER 3
FUNDAMENTALS OF COMPOST PRODUCTION
Composting of yard trash such as grass clippings, shrub prunings, leaves, and other green
materials has been practiced for centuries. In natural situations, under forest canopies,
composting takes effect as leaf litter decomposes into humus. Humus is the rich, dark brown to
black colored remains of the composted plant material and is considered an excellent soil
conditioner. For decades, in the United States, the importance of humus has been all but ignored
as the agricultural industry increasingly relied upon manufactured fertilizers to improve crop
yields. Interest in the production and use of compost is on the upswing as more farmers,
homeowners, private companies, and municipalities due to the benefits afforded to soil and crops,
as well as the reduction of landfilled waste.
Composting requires a thorough understanding of the process to ensure that the facility is
operated in an environmentally safe manner and that the end product will be beneficial to the
plants and soils to which it is applied. This chapter presents information that is generic to every
compost site. Depending on the type of yard material and bulking agent available, facility
operators should make adjustments to optimize decomposition conditions.
Contamination
One of the most important factors in producing quality yard trash composts is the
exclusion or removal of undesirable raw materials prior to composting. Undesirable materials
include plastics, metals, glass, paper products, large wood products, building wastes with nails,
and woody plant materials which have not been reduced in size. Kitchen waste, manures, and
biosolids (wastewater residuals) may be compostable, but those processes are not within the
scope of this manual.
The best method for avoiding these contaminants is knowing the source of materials,
careful inspection prior to processing, and attention to composting conditions.
Feedstock Preparation
Feedstock preparation is an important first step to ensure that the composting process is
optimized. Moisture content, carbon , nitrogen, and some micronutrient are the raw materials
that will determine the recipe of the mix. The following chart describes the function of each
element in the microbial process:
Carbon: Is used by microbes as a sources of energy and is the most abundant
component in the cellular structure.
Nitrogen: Is used by microbes to grow and multiply.
Other Nutrients: Macronutrient such as Phosphorus, Potassium and calcium are all
requirements for microorganisms and are present in yard trash materials.
Moisture Content: Moisture is necessary to support the metabolic process of the microbes.
Water provide the media for chemical reactions, transport nutrient and
allows the microorganisms to move about the pile.
The ratio of carbon to nitrogen is an important nutrient factor. A C:N ratio of 30:1 for
incoming feedstock is considered ideal. However these ratios may vary depending on the location
and the types of feedstocks received. This should be taken into consideration when deciding
compost process and overall goals.
Oxygen and Aeration
Successful composting depends on a sufficient supply of air being made available to the
materials in the compost pile. Oxygen is essential for microbial activity to meet the requirements
for adequate decomposition. Although decomposition of plant materials can proceed
anaerobically, or without oxygen, and compost piles may contain anaerobic regions, composting
with adequate aeration proceeds more rapidly. Composting with adequate aeration also generates
higher temperatures (113-158 F, compared to 59-131 F. for anaerobic comporting), less methane,
and more carbon dioxide than anaerobic composting. Anaerobic composting is desirable in
specialized operations such as methane generation for energy, but composting with adequate air
generally produces a higher quality compost for agricultural use. Composting without adequate
aeration may result in the production of objectionable odors.
The height and age of the compost windrow may affect decomposition in that piles may
become too compressed and anaerobic. Oxygen is introduced into the composting process
through turning the pile. Oxygen meters can be used to determine when piles should be turned.
Odors, collapsing of the pile, lack of vapor at the top of the pile also indicate that the oxygen
levels are low and the pile should be turned.
Particle Size and Surface Area
Particle size is crucial to the structure and size of the windrow pile because particle size
greatly affects aeration. Large brushy yard trash must be reduced in volume to standardize the
material and to allow a particle size that will promote air flow in the composting pile. The ground
material will allow a greater surface area for the microorganisms (fungi, bacteria, and
actinomycetes) which will promote decomposition.
The pile should be constructed so that a chimney effect takes place within the pile. The
chimney effect allows for air to be drawn into the bottom of the pile and then vented through the
top providing the necessary oxygen for microbial activity. In a properly constructed pile this
venting is apparent when the area along the ridge of the pile is giving off visible vapors.
It is essential to maintain a balance between larger and smaller particles. Too many fine
particles will close off air channels and reduce oxygen levels. Too many large particles will allow
over aeration and cooling of the pile. Overaeration will reduce moisture content through
evaporation.
Moisture Content
Moisture is required to support microbial activity for optimum decomposition to occur. If
the moisture level is too low, decomposition slows down, if the moisture level is too high it
causes anaerobic conditions and odors. An optimum range for moisture content is between 40
and 65% depending on the particle size and structure.
Material coming into the site will vary in moisture content. Factors affecting moisture
content include ambient conditions and type of material. For example, leaves that are gathered
during the rainy season and wood chips obtained from fresh material will arrive at the site with a
higher moisture content than leaves collected after a dry spell or wood chips obtained from old or
dried brush. Grass and green leaves will contain encapsulated moisture that is contained within
the plant's cells, and the moisture will be released slowly as the material decomposes.
If the material is dry and brown and the temperature of the material is low, the moisture
content is probably insufficient. It is recommended that moisture be added as necessary to
maintain the optimum moisture level in the piles.
Carbon/Nitrogen Ratio
The ratio of carbon to nitrogen (C:N ratio) in compost piles has been used as an indicator
of compost maturity, compost quality, and suitability for compost application to agricultural
fields. In general, finished composts, which are composts considered sufficiently stable for
storage or land application, are within the range of 15:1 to 35:1. Resistant woody materials often
have C:N ratios as high as 200:1. Nitrogen-rich residues such as grass clippings may be mixed
with these high carbon materials to accelerate rates of composting. It is the growth and death of
the microorganisms that lowers the C:N ratio in composting substrates. The C:N ratio is no
longer considered the ultimate "rule-of-thumb" in compost maturity or acceptability for
agricultural use. Although high C:N ratios have typically been associated with tying up nitrogen
(immobilization) in the soil where such materials were applied, some high C:N ratio materials such
as lignin-rich peat-moss do not immobilize nitrogen.
Analyses for C:N ratios are considered variable, notoriously inaccurate, misleading, and
often contain gross generalizations. Better indicators of compost maturity and stability are
constantly being studied with advances in this area are anticipated in the future that will help
compost producers more easily determine reliable production parameters.
pH
The pH of finished yard trash composts ideally should be close to 7.0. Unfinished
composts can have acetic acid contaminants which would lower the pH. Inclusion of undesirable
materials such as excessive lime or elemental sulfur might affect the pH of finished composts, but
in general carefully produced, mature, yard trash composts have a pH of 6.5 to 8.0.
Pathogens
Conditions that occur during the active phase of properly managed yard trash operations
generally provide a reasonable assurance that weed seeds and plant pathogens do not present an
environmental problem.
Heat generation is the most recognized method for controlling seeds and pathogens. A
regimen of temperature control and monitoring in conjunction frequent turning to maximize
exposure of the yard trash materials to elevated temperatures can ensure a sanitized finished
product.
Some researchers report optimal decomposition of plant materials at 131-140 degrees F.
As a general rule, attainment and maintenance of temperatures higher than 131 degrees F. over a
three-day period should be sufficient to eliminate all pathogens and weed seeds found in the
windrowed pile.
CHAPTER 4
FUNDAMENTALS OF MULCH PRODUCTION
One of the most common alternatives for recycling yard trash in Florida is mulch
production. Florida's tropical landscapes provide a woody brush feedstock that after it has been
volume reduced, maintains its structure for a useful and recognizable mulch. This product is
relatively easy and cost effective to manufacture and can be adaptable to a variety of communities
in the state.
Webster's dictionary defines mulch as "a protective covering spread or left on the ground
especially to reduce evaporation, maintain even soil temperature, prevent erosion, control weeds,
or enrich the soil."
Types of Mulch
There are typically three types of mulches made from yard trash: fresh mulch made from
heterogeneous ground yard waste; sanitized mulch made from fresh mulch that has been
windrowed; and wood mulch made from hard and soft wood logs.
Characteristics
The characteristics of mulch as an end product will depend upon the preference of the end
user. Following are general parameters for acceptable mulch products in Florida:
Color - golden brown to dark brown
Size - 1/2 inch to 4 inches
pH - 6.1 to 8.0
Odor - little or no odor
Moisture - 30% - 45%
Weight - Fresh ground mulch: 350 to 400 lbs./cubic yard
Windrowed mulch: 450 to 650 lbs./cubic yard
Log mulch: 450 to 550 lbs./cubic yard
(Note: Density and moisture content affect the weight.)
Structure - loose, friable and fairly coarse.
Foreign Matter - less than 2% by weight.
Fresh Mulch
Fresh mulch is a product that is made from freshly ground yard trash. Fresh mulch has
little or no decomposition, and may contain weed seeds, plant diseases, and insects. Fresh mulch
is suitable for uses in which these limiting parameters is not a concern, such as for erosion control
at a landfills, landfill cover additive, bulking agents for sludge composting, projects that encoura
ge phytotoxicity, and other low risk mulching projects.
Sanitized Mulch
Sanitized mulch is a product that is made from freshly ground yard trash that has gone
through the windrow process long enough to attain the heat necessary to destroy the unwanted
characteristics of fresh mulch.
Yard trash processing facilities operators in Florida have found that fresh mulch is difficult
to market because of its potential contamination by weed seed, insects, and plant disease.
Sanitizing the fresh mulch improves the acceptability and marketability of the product.
Studies by Aziz Shiralipour and Dennis McConnell indicate that high temperatures and
phytotoxins produced during the composting period have an inhibitive effect on the germination
of weed seeds. Even the most heat resistant weed seeds failed to germinate after they were
exposed to 131 degrees F. for 48 hours. (Shiralipour and McConnell). The EPA has also found
that this temperature is necessary to destroy most plant pathogens. Most insects are destroyed at
lower temperatures of 115 degrees F for three days. (cite)
The windrowing of mulch creates an environment acceptable to microorganisms activity
which produces heat in the piles. The main difference between composting and windrow
mulching is that in the mulching method, decomposition is not the goal. The goal to increase
microbial activity, thereby raising temperatures to the point necessary to destroy the undesirable.
At that time the piles should be turned. In composting, microorganism activity is encouraged to
reach the optimum state of decomposition, then turning is required.
Once the yard trash is ground it is placed into elongated piles, an environment in which
microorganisms thrive. The shape of the windrows gives the microbes needed air flow and
insulates to contain temperatures. Windrow size can vary depending on the type and density of
the ground material, its moisture content, aeration, and ambient temperature. Temperatures can
be controlled by pile size. Piles containing a higher quantity of nitrogen can reach acceptable
temperatures to sanitize at a lower pile height than piles that contain a lower quantity of nitrogen.
When nitrogen content is high, windrows will typically reach acceptable temperatures at a height
of 6-8 feet. When nitrogen is lower, mulch windrows typically range from 8-10 feet.
As micro-organism activity increases, the temperature inside the pile increases. After
temperatures reach 131 degrees F. for three days, the piles can be turned to allow the exterior of
the pile to be exposed to the high internal temperatures. The pile should be allowed to reheat and
again maintain 131 degrees F for three days. The piles should then be turned a second time and
allowed to reheat to 131 degrees F. for 3 days. If the temperature of the piles begins to drop due
to reduced moisture content, then moisture should be added during one of the turns.
Log Mulch
Log mulch is made from grinding whole logs, limbs and branches five inches or larger and
does not include palm trees or stumps. To ensure that log mulch remains clean and free of
contaminants, the log material should be separated from the other incoming brush material and
kept free of debris, dirt, and palm tree logs. Log mulch has a brighter brown color and maintains
its original appearance for a longer period of time than other yard trash mulches and can be
compared to commercially harvested landscape mulches, such as cypress.
Plant Safety
The production of landscape mulch using yard trash is a viable recycling alternative, but a
word of caution is offered. According to Dr. Francis Gouin, "Recycled wood chips that are
applied as mulch soon after processing may also cause damage by suffocating plants and starving
them of soil nitrogen.... The problem is due to an imbalance in the carbon:nitrogen ratio in
demolition ground wood and recycled tree and shrub waste". The solution according to Dr.
Gouin is to reduce the carbon:nitrogen ratio to 60:1 or less, which can be accomplished through
micro-organism activity. When this method is applied correctly a "mantle of dark brown wood
will surround the lighter, more solid, tissue in the center of the wood chips. Although the chips
are not thoroughly composted, the outer mantle of decaying wood fiber will retard the
competition for soil nitrogen when the material is used as mulch".
CHAPTER 5
FUNDAMENTALS OF FUEL PRODUCTION
Biomass fuel is vegetative waste used as a source of fuel. Yard trash and other clean
woody wastes should be processed to a uniform size and burned as boiler fuel to recover the
energy content. To ensure the acceptability and marketability of biomass fuel, some basic
management practices should be followed.
Wood fuel is purchased on the basis of energy content, or Btu value. The two things that
most affect Btu value are the moisture content and the amount of soil or other non-combustibles
in the vegetative material. Therefore, yard trash should be stored in a manner that allows the
materials to dry and that minimizes contamination.
All biomass fuel markets provide written specifications for material to be purchased.
Although they vary between fuel users, the basic specifications usually include the provisions
described below.
Material Description
Almost any type of vegetative material can be considered, including yard trash, scrap
wood from construction and demolition, commercial tree trimmings, landclearing debris, pallets,
etc. Research on the combustion characteristics of yard trash has suggested, however, that if
large quantities of grass clippings and other fine trimmings are included in the material, screening
may be required.
The material should contain a significant proportion of woody material, such as larger
diameter trees or construction wood. The fuel users are finding that fuel consisting solely of
unscreened curbside collected residential yard trash is not as desirable because of issues with
chemical content and ash composition.
Particle Size
Generally 95% of the material should pass through a screen with 3" round holes, and no
pieces should be larger than 6" or 8" in any direction. The amount of smaller material less than
1/4" (often referred to as the "fines") should be limited to allow efficient combustion.
Most fuel markets prefer that fines content be limited to less than 5-10% by weight. For
yard trash this is a difficult specification. Care should be taken in the grinding process or the fines
will have to be removed prior to shipping by passing the material through a screen.
Product Storage
Product storage is not recommended, especially if the material contains a high percentage
of green vegetative waste. If the material starts to decompose prior to shipment it may be
necessary to rescreen the material prior to shipment. Ideally the material should be shipped within
five days of processing.
Non-wood Contamination
Non-conforming material such as plastic, metal, concrete, etc., should be limited to less
than 1-5% by weight, depending on specifications. Removal of plastic bags may be required
depending on specifications. Metal should be removed not only because of the fuel
specifications, but also for operating safety and decreased maintenance costs.
Moisture Content
Specifications generally require a moisture content of less than 50%. At higher moisture,
the combustion process becomes very inefficient, and emissions become difficult to control.
Through the use of effective management practices, yard trash facility operators should try to
achieve moisture contents as low as 25-35%.
Ash Content
Ash content is what will not combust when the material is burned. The ash content is
directly related to the amount of soil in the incoming material. If the material has been properly
processed, the ash content will range from 8-12%. Curbside yard trash generally contains 8%
ash, in the form of soil picked up with clippings. Clean wood waste can have ash content as low
as 1.5%.
Btu Value
Btu is the measurement of energy available in the material that is being combusted. The
Btu measurement will indicate the fuel value. Btu value for yard trash typically varies from 2200
to 4500 Btu per pound depending upon the composition of the yard trash and how it has been
size-reduced.
CHAPTER 6
FACILITY SITING AND DESIGN
Facility siting and design is the key to operating a yard waste processing facility that will
have minimal impact upon the surrounding community and the environment. Proper siting and
design will minimize the costs of operation and the potential for complaints from neighbors or the
regulatory community.
This chapter describes several important siting and design considerations for yard trash
processing facilities.
Location
The ideal location would be as close as possible to yard trash generators to reduce
collection costs (which can be the single highest cost of segregated yard waste) and also as close
as possible to end user markets.
Due to its traffic generation, outside storage, heavy equipment usage, and the nature of
the feedstock, a facility should be located close to other agricultural, public utility, or industrial
uses. A site adjacent to residential land uses can create the need to provide a greater degree of
operational controls in order to prevent traffic, odor, or noise problems. The location should
conform to applicable zoning and comprehensive plan designations.
Permitting Requirements
Most states, especially those in the central and western United States, have not established
specific permit or siting requirements for facilities that process yard trash. Three states -
Delaware, Michigan and Pennsylvania) - have expressly exempted from requirements facilities that
compost yard trimmings because of the minimal environmental impacts generally associated with
such facilities. (CRS, 1989).(1)
In Florida, developers of a yard waste processing facility should consult with their local,
regional, and state regulatory agencies in order to determine their development requirements. The
facility may fall under the jurisdiction of local zoning and building requirements, local
environmental agencies, regional water management districts and the Florida Department of
Environmental Protection.
Local Zoning and Building Requirements
Local city and county zoning and building codes regulate where specific land uses can be
established. Requests for zoning or special use permits may be required before a developer can
proceed with the site plan approval and building permit process.
Local Environmental Agencies
Some counties and cities have environmental review agencies that provide a similar
function to the Florida Department of Environmental Protection. Applications and site plans may
be required to be submitted to the local environmental agency for review and approval.
Water Management Districts
The management and storage of surface water falls under the regulation of Florida's five
Water Management Districts. Permit requirements address three areas of surface water
management: (1) Water Quantity/Quality; (2) 100-Year Floodplain; (3) Environmental
Considerations. Your regional water management district should be consulted early in the
approval process.
Florida Department of Environmental Protection (FDEP)
FDEP regulates yard trash composting facilities under Rule 62-709, FAC, and an FDEP
memorandum of policy on May 18, 1995 removed the permitting requirements. FDEP still
maintains the enforcement provisions of 62-709 for yard trash composting facilities. The
processing of yard trash into other usable materials such as mulch is not considered composting
and is not regulated under Rule 62-709 per Rule 62-709.300(10).
Setbacks
When designing a site, local zoning and environmental agencies should be consulted
concerning setback and buffer requirements. Yard waste composting facilities must comply with
FDEP's setback regulations for solid waste facilities (Rule 62-701) as follows:
(1) within 500 feet from an existing or approved potable water supply well;
(2) within 1,000 feet from of any existing or approved potable well serving a community
water system; and
(3) within 200 feet from any natural or artificial body of water, including wetlands.
At the time this manual went to press, FDEP was considering removing the permitting
requirements, which include the above setback requirements, for yard trash composting facilities.
The lack of documentation of adverse environmental impacts from yard waste processing facilities
would support such a decision by FDEP. No setback requirements are recommended from
existing or approved potable water supply wells, or from natural or artificial bodies of water,
including wetlands, or from any existing or approved potable well serving a community water
system.
Current Federal Aviation Administration (FAA) guidelines prohibit siting any type of solid
waste facility, including composting facilities, within 10,000 feet (almost 2 miles) of an airport
(NTIS, 94). (2)(p56).
Buffers
Buffers are intended to mitigate nuisances. Types of buffers include distance, vegetation
(trees), bodies of water, and structures (berms).
For yard waste processing sites a buffer or setback is needed more for fugitive dust and
particulates than for odors. Following the operational recommendations in Chapter 7 of this
manual can reduce the distance needed for buffers.
During the site design, the direction of the prevailing wind should be noted and the buffer
zone extended in this direction. This will help minimize the transport of odor and bioaerosols
downwind of the facility (NTIS 94). (3)(p.63)
Entrance and Exit Requirements
The facility should be easily accessed from major transportation routes. Approach to the
entrance and exit should be from a road with adequate capacity and turning capabilities. Travel
through a residential neighborhood should be avoided. The entrance road should be designed to
avoid delay and back-up of vehicles entering the site. This can be accomplished by designing
circular traffic flow patterns along with adequate turning and dumping areas. The entrance and
exit roads should not create any major pedestrian or vehicular conflicts. The entrance and internal
road network should provide access to fire trucks and other emergency vehicles. The processing
site should have access to hard surface roads. The preferred access road should be one that is
gravel or paved and capable of use during wet weather and during the rainy season. Road design
should support any anticipated high volume or heavy weight vehicles. A traffic study may be
performed to determine anticipated traffic volume.
Stormwater Control
Florida's extended rainy season requires that a site design provide for proper drainage.
Poor drainage and ponding impede production and contributes to the introduction of foreign
matter into compost. Adequate stormwater controls should be provided to provide for retention
and detention of stormwater as necessary prior to leaving the site. Design considerations for
stormwater control include percolation, slope, retention pond, and hydraulic overload.
Percolation
Locate the site on moderate to well drained soil. If there is no hard surface the soil should
be permeable enough to ensure the excess water is absorbed during heavy precipitation and that
the upper layers of soil do not become water-logged. This creates pooling and limits vehicular
access (NTIS 1994).(4)(p59)
Slope
The surface should be graded to avoid standing pools of water. The ideal slope is a 2 to 4
percent grade with a 1 percent minimum. (Rynk,et.al., 1992). (50)(p.64) It is recommended that
windrows be parallel to the direction of the slope to direct runoff and avoid ponding.
Retention or Detention Areas
Runoff from impervious surfaces should be directed to adequate retention or detention
areas to control the offsite release of stormwater. Stormwater runoff from the delivery area
should not flow into curing or processing areas, which could reintroduce pathogens, insects, and
weed seeds.
Land Area Requirements
The most important factors in determining the amount of landed needed for a yard waste
facility are the type and quantity of products to be produced. Other factors include:
- the level of processing technology, e.g., height of windrows, space between rows and
rate of volume reduction
- storage time required before grinding;
- market demand for material, such as fuel;
- buffers;
- regulations regarding setbacks, stormwater retention and land use.
Staging Area
The stage area is dedicated to receiving, weighing, unloading, inspecting, mixing, and
grinding yard trash. The size of the staging area is a function of the volume received and the
period of storage before grinding.
Processing Area
Windrow construction and turning occur in the processing area. Factors that determine
the size of this area include:
* The level of technology
* Material volume received
* Character of feedstock
* Pile height
* The products to be produced and marketed
Storage and Curing Area
Activities in the storage and curing area include post-process screening, stockpiling
finished product, and loading for shipment. The size of this area is determined by:
*Storage pile height, size, and volume
*Length of time between seasonal market demand: Allow for approximately six months'
capacity based on the time between the two peak seasons, spring and fall.
Projections for Site Capacity and Layout for Composting and Mulching Facilities
The land area of a composting facility must be large enough to handle both present and
projected volumes. Ideally, a composting facility should have, at a minimum, enough acreage to
accommodate an entire years' projected volume of incoming feedstock on the site. (Richard et al.,
1990). (12) (p60)
Processing site capacities range from 1,500 to 3,000 tons per year per acre (Schroeder,
1993) (11) (p. 158)
One of the most useful and practical guidelines written on calculating the land area
requirements for a compost facility is found in the On-Farm Composting Handbook published by
Northeast Regional Agricultural Engineering Service Cooperative Extension Ithaca, NY.
When designing a mulch or composting facility and assigning land area to the three
operational phases of staging, processing, and storage, the plan should take into consideration the
relationship between volume reduction and material handling equipment. A survey of eight
facilities across the U.S. shows an average volume reduction of 65 percent (ENR, 1989). (13)
(p27)
The suggestions used for site design in this section is based on experience from a mulch
production process that uses compost management techniques during a four to six month period
to sanitize 10 foot high windrows by monthly turning with a front end loader. This may not
always apply to composting operations with 7 foot high rows and who use windrow turning
equipment.
In Florida the climate with its warm weather and long growing season fuels a continuous
cycle of plant growth resulting in the generation of shrubbery and woody, carbonaceous material
that is low in nitrogen content. When this material undergoes a low technology mulch production
process it requires 9 to 12 months to achieve a significant volume reduction.
One formula used in mulch production to assign land space to the areas needed for
operations uses the following percentages:
* Give 25% to the staging area
* Give 50% to the processing (composting pad) and
* Give 25% to the storage and screening area (Lehmann, 1995). (14) (p47)
Staging Area Operations
Tub grinding equipment brings the single largest reduction in volume by a ratio of three to
one. A hundred yards of brush and shrubbery when delivered will be reduced by 66% to a volume
of 34%, rendering 34 yards after grinding. Therefore the staging area, where the tub grinder is
located, should be less than half as large as the composting pad in the processing area. At 25%,
this will allow for stacking, drying and the initial start-up of the decomposition process.
Processing Area
The composting pad is half of the total site area but is sufficient when the compaction
factor is taken into consideration. Windrows of 10 feet will compact up to 20 percent allowing
acceptance of more volume. Volume reduction in this phase ranges from 15 to 30 percent over a
three to six month period. This area should be close to the staging area with rows perpendicular
to the staging area to reduce transfer distance.
Storage Area
The storage area should be assigned a space of 25% of the total site area. This is a
function of a cumulative 75% volume reduction of material from delivery to final stockpile. This
can best be understood by the illustration below.
Screening activities should take place in the storage area.
Site Surface and Sub-Surface
Paved or hard-surface areas are ideal for receiving, processing, and storage areas due to
the amount of rainfall in Florida. However, firm surface with moderately- to well-drained soils
may be satisfactory. Where existing soil conditions are not acceptable, a pad constructed of 6
inches of compacted and graded sand, gravel, or shell works well (Rynk et,al. 1992). (6)(p67)
Some of the reasons that a paved surface is recommended include:
o It improves productivity and operational efficiency during rainy season.
o The repetitive motion of heavy equipment when mixed with layers of organic
material and soil produces an uneven work surface, ruts, and ponding.
o Surface soil mixes with yard waste introducing foreign material into a mulch
product.
The minimum separation distance commonly recommended between surface soils and the
water table based on the seasonal high level ranges is from 2-5 feet. A site soil investigation
should be conducted by a soil scientist, possibly through the assistance of the SCS (Rynk et al.,
1992). (8)(p63)
Utilities
Yard waste processing facilities need access to utilities including water, wastewater,
telephone and electricity.
The proper moisture levels for mulch and compost production need to be maintained
through the addition of water. Options available are potable water, recycled water, retention pond
or lake water, and rain water.
Security
Yard waste processing facilities should have adequate security to limit the access of
vandals or illegal dumpers.
Signage
Proper entrance and exit signage should be provided to ensure safe traffic control.
Additional signs should be provided that with information on the operator of the site, the hours of
operation, emergency contact phone number, and materials that are and are not accepted at the
facility.
Material Measurement
Scales are recommended to ensure proper recordkeeping and management of the incoming
material, and the outgoing products. Due to its variation, yard trash densities and weights may be
difficult to track on a volume basis. Where scales are not available, volume estimation is an
acceptable method of recording the material entering and leaving the facility.
References
1. Cal Recovery Systems (CRC) and M.M. Dillon Limited. 1989. Composting: A Literature
Study. Ontario, Canada: Queen's Printer for Ontario. (EPA p.77)
2. United States Environmental Protection Agency. (1994). Composting Yard Trimmings and
Municipal Solid Waste. Washington, D.C. (NTIS No. PB94-163250)
3. United States Environmental Protection Agency. (1994). Composting Yard Trimmings and
Municipal Solid Waste. Washington, D.C. (NTIS No. PB94-163250)
4. United States Environmental Protection Agency. (1994).
Composting Yard Trimmings and Municipal Solid Waste. Washington, D.C. (NTIS No PB94-
163250)
5. Rynk, R., et.al. (1992). On-Farm Composting Handbook.
Ithica, N.Y.: Northeast Regional Agricultural Engineering Service.
6. Rynk, R., et.al. (1992). On-Farm Composting Handbook. Ithica, N,Y.: Northeast Regional
Agricultural Engineering Service.
7. Richard, T., N.Dickson, and S. Rowland. (1990). Yard waste management:A planning guide
for New York State. Albany, N.Y.:
New York State Energy Research and Development Authority, Cornell Cooperative Extension,
and New York State Department of Environmental Conservation.
8. Rynk, R.., et.al. (1992). On-Farm Composting Handbook.Ithica, N.Y.: Northeast Regional
Agricultural Engineering Service.
9. Simpson, M. & Engel, P. (1990). Leaf and Yard Waste Composting Manual Prepared for the
National Corn Growers Association. St. Louis, Mo.
10. Lehmann, T., (1995, May). Florida Department of Environmental Protection 1995 Recycling
Coordinator Training. Lecture on Yard Waste Composting, Gainesville, Fl.
11. Nordstedt, R., Barkdoll, A.W., Schroeder, R. (1993). Composting of Yard Waste. H.A.
Hoitink & H. M. Keener (Eds.), Science and Engineering of Composting: Design, Environmental,
Microbiological and Utilization Aspects (p.158). Wooster, Oh: Renaissance.
12. United States Environmental Protection Agency. (1994). Composting Yard Trimmings and
Municipal Solid Waste. Washington, D.C. (NTIS NoPB94-163250)
13. Illinois Department of Energy and Natural Resources. (1989). Management Strategies for
Landscape Waste. Springfield, Il.: Illinois Department of Energy and Natural Resources.
14. Lehmann, T., (1995, May). Florida Department of Environmental Protection 1995 Recycling
Coordinator Training. Lecture on Yard Waste Composting, Gainesville, Fl.
CHAPTER 7
OPERATIONAL CONSIDERATIONS
The goal of every yard waste processing facility should be to operate in a manner that
does not impact the environment or the community surrounding the facility. The potential to
which the environment or community can be impacted is greatly influenced by the following three
factors:
o Location of the facility and closeness to neighbors. The recommendations for the
siting of a facility in Chapter 6, can reduce the operational requirements that need
to be followed. Greater distances to the nearest neighbor will reduce the
recommended noise, odor, and process times considerations.
o The amount and type of material received for processing. The amount and type of
material processed will often dictate the area requirements of the facility, the
intensity of processing required, and the timeframes required to produce the end
product.
o The end products being produced from the incoming material. Yard waste
compost requires greater processing and storage areas than the processing of yard
waste materials into fuel.
The following recommended operational guidelines when applied to a specific facility need
to take into consideration the three factors referenced above. An operational parameter that is
acceptable at one site may create a problem at another site.
Incoming Material
The receipt of material must take into consideration the following variables:
o type and number of vehicles delivering material
o type of material and whether it is in bags
o site operator control of collection of material
On-Site Personnel
Each site should have personnel monitoring the receipt of each load and inspecting the
load for foreign matter or contamination. This may not be necessary if the operator of the site has
control over the sources of material being delivered, or if the quality of the end product is not a
concern. On-site personnel should also be present for traffic control and the directing of loads
containing different types of source-separated yard waste to separate receiving areas. Sites
receiving low volumes of yard waste material from known sources may not need on-site personnel
reviewing the loads.
Incoming Material Considerations
Separation by Material Type
Loads should be identified and directed to separation areas for different product streams
such as biomass fuel material; hardwood logs (excluding palm trees) go to log mulch areas;
shrubbery, brush, palms go to regular mulch areas; and compost feedstock, such as grass, leaves,
and wood chips from tree services can go to windrow areas when grinding is not required. Also,
material too large for the manufacturers rated capacity of the grinding equipment on site should
be separated and left for periodic grinding by outside contractors using land clearing equipment.
Plastic Bags
Yard waste materials contained in plastic bags need to be managed in an effective manner.
The main concerns with plastic bags on yard waste processing facilities are the potential of odors
during debagging and initial processing, litter caused by shredded plastic bags, and maintaining the
marketability and quality of the products produced from yard waste received in plastic bags.
Plastic bags containing grass that will be processed into products other than fuel should be
removed within a short period of time of entering the site; 24 to 48 hours is recommended,
depending upon the proximity of neighbors. There are many plastic debagging systems available
but their effectiveness in removing all of the plastic in a cost effective manner is still a question for
site operators to deal with.
Grass
Loads containing primarily grass, whether in bags or already collected in bulk need to be
specially managed onsite so as to minimize odor and the release of nitrogen. Grass should be
mixed with a sufficent amount of a carbon source and incorporated into windrows to provide a
proper amount of moisture, a preferable C:N ratio, and adequate availability of oxygen.
Contaminants
Loads need to be inspected for household hazardous waste and for other foreign material
such as glass, metal, plastic, construction and demolition debris, and other undesirable materials.
Storage Parameters
Storage parameters and processing times depend upon the the materials being received,
products to be produced, the size of the facility and its location relative to neighbors. Facilities
receiving large quantities of grass should process the loads of grass in the timeframes discussed
above. Facilities receiving greater percentages of limbs, bursh and palm fronds are not as time
sensitive for processing.
The amount of material allowed to build up on site is a another consideration. It may not
be economical to process without a minimum tonnage built up prior to bringing the proper
equipment on site. Raw yard waste that is able to be consolidated with a front end loader can be
managed to take up very little area. An acre of storage area can hold 750 tons if properly
managed.
It is recommended that no more than 1500 tons of material is allowed to accumulate prior
to size reducing it and determining the proper form of processing it into the desired end product.
As previously stated, this amount can be increased if there is sufficient storage capacity and the
location of the site is of sufficient distance from neighbors so as not to create complaints.
Size Reduction
Yard trash to be processed into desirable end products requires size reduction. Size
reduction is necessary to increase the surface area in order to increase microbial activity for
decomposition, or to create end products of proper size and aesthetics, such as log mulch or fuels.
Size reduction of yard waste materials is predominantly done by tub grinders that have
been adapted and modified from the agricultural industry. Other equipment is also available to
process yard trash, such as horizontal feed grinders, chippers, and high- and low-speed shredders.
A facility operator should review his specific needs based upon the type and amount of material to
be processed, and the level of monitoring of incoming material to insure a minimum of
contamination.
Volume Reduction
Yard trash is high volume, bulky waste that must be managed to optimize space and
standardized to produce a marketable product. In many locations where the yard trash is
comprised of mostly leaves and grass no further volume reduction would be necessary. In most
situations however, a volume reduction machine is necessary to control the brushy mixture of
incoming materials.
In the small operation of 5 to 10 tons of material per day, a hand fed chipper may satisfy
volume reduction needs. This is a machine of low capital cost, resulting in low production with a
high investment of manual labor. The material that comes out of a chipper has a smooth surface
and is somewhat of a chunk. When placed in the landscape this mulch has a tendency of floating
and offers only a small amount of moisture retention.
As the facilities become larger, requiring more machines to keep up with incoming
material, a tub grinder or horizontal fed grinders would be a consideration. The most commonly
used machine is the tub grinder. These machines come in different sizes from power units that
hook up to a tractor to self-powered units of over 800 horse power. Tub grinders are generally
high capital cost, high production, low labor, but high maintenance. The brush nature of the yard
waste can require a wide feed system to accommodate oversized material ranging from palm
fronds to tree limbs and stumps. The large bowl opening and the rotation of the inside walls of
the tub grinder offers an efficient means of handling bulky materials. A tub grinder produces an
end product that is a shred, and has rough surfaces (George Machado). This product has a
tendency of staying put in the landscape without floating, it holds moisture better, but will
decompose faster than a chip product.
Processing Times
Processing times are dependent upon the end product to be produced and the level of
effort to manage and accelerate the natural process. Mulches made of clean wood and large limbs
and trunks of hardwoods are finished end products with no additonal processing after it is size
reduced.
The time required to process yard trash materials into a stable compost product will vary
depending upon the level of management utilized in the process. There are three technologies that
can be used in composting yard trash: minimal level, low level, and intermediate level.
Minimal Level: This is a low-cost approach to compost yard trash. This material is
composed of leaves and grass and does not require volume reduction. The material is blended
and placed into a windrow. Turning is limited to once per year and anaerobic regions may
develop within the piles. There is little or no management of the pile in regards to oxygen,
moisture, and temperature control. This method requires large land areas and requires up to three
years to produce a stabilized compost.
Low Level: This is a method requires a higher level of management than the minimal
level. Yard trash is volume reduced to a uniform size, maximizing the surface area for microbial
activity. The material is placed in windrows and monitored once a week for oxygen, moisture,
and temperatures. Windrows are turned once per month with moisture added when piles dry out
and microbial activity slows down. This technology will produce a stabilized compost in six
months to a year.
Intermediate Level: This method of yard trash composting requires volume reduction and
weekly turning of windrows. The piles are managed to optimize the proper level of oxygen,
moisture, and temperature distribution. Feedstocks are blended to obtain the proper mixture of
carbon material and nitrogen material. This method will produce a stabilized compost within
three to six months.
Pile to Alley Relationship
Pile to alley relationship is the space between the windrows. The following distances are
recommended to allow for processing equipment access:
* 3-5 feet is needed for self propelled windrow turners
* 6-10 feet is needed for tractor assisted windrow turners and front-end loaders.
See illustration on Dimensions and Spacing for Windrows and Piles
Source: On-Farm Composting Handbook
Dust Control
In general air quality when measured for pollution is not a problem at composting
facilities, with the exception of occasional odors. Dust can frequently be a problem at composting
facilities, particularly in the dry months. Dust is generated from dry, uncontained organic
materials, especially during (wiundrow turning), screening and shredding operations, and from
vehicle traffic over unimproved surfaces. (NTIS, 94). (1) (p.68)
Operational decisions that can be made by management to reduce fugitive dust and
provide for worker safety include:
* Restrict activities when the wind direction is unfavorable
* Locate a high dust activity on a remote location of the site
* Dampen roads and areas that generate dust.
* Employees should use goggles and filter masks
* Use equipment with an enclosed operator cab with air conditioning that has a
replacable air filter system
Bioaerosols
Bioaerosols are microorganisms that may have the potential to cause adverse health
effects. In 1993 a workshop sponsored by the Composting Council, The U.S. Environmental
Protection Agency, and the U.S. Department of Agriculture brought together scientists and
engineers to review the potential health risks associated with composting facilities. Those experts
determined that "composting facilities do not pose any unique endangerment to the health and
welfare of the general public." (Composting Council Fact Sheet, p. 6) A copy of the executive
summary of the workshop's conclusions is included in the appendix of this manual.
Odors
"Odor problems are the single biggest threat to a composting operation. Nothing is more
persistent than an angry neighbor seeking to shut down a composting operation because of odors.
In theory, aerobic composting does not generate odorous compounds as anaerobic processes do.
Objectionable odors can come from certain raw materials or the process itself if conditions are not
right.
"There are three primary sources of odors at a composting facility: odorous raw materials,
ammonia lost from high-nitrogen materials, and anaerobic conditions within windrows or the
composting process.
"Anaerobic conditions can be minimized by proper management of the compost facility.
Use a good mix of raw materials, avoid overly wet mixes, monitor temperatures, and turn to
aerate the materals regularly. Bad odors can be controlled by providing extra carbon in the mix
and maintaining the pH below 8.5. The most common causes of odors at a composting site are
strong smelling raw materials. The odors come to the site with the materials and do not dissipate
until the materials begin composting." (Cochran, B. et al, 1995). (2) (23)
"Anaerobic conditions encourage generation of odorous compounds like organic acids,
mercaptans, alcohols, amines, and hydrogen sulfide gas and other odorous culphur compounds."
(Williams and Miller, 1992; Diaz, 1987). (3) (70)
Noise
Noise is measured in terms of sound pressure called a decibel (dB). Sound levels decrease
with distance from the source. For each doubling of the distance from a single source, noise
levels decrease by 6dB because the sound waves diverge from the source (Compost Council,
1994). (6) (section 9.4-p.2) A tub grinder hammermill can generate about 90 decibels at the
source (NITS, 1994). (5) (p70)
Noise generated by a yard trash processing facility is regulated in two ways:
* Occupational Health and Safety Administration (OSHA) or similar state requirements
specify noise exposure limits for facility employees. These limits usually specify exposure limits
for different sound levels (such as 3 hours at 97 dBA but only 1 hour at 100 dBA).
* City or county noise ordinances often specify acceptable noise levels at property
boundaries or at the nearest residence. Those ordinances usually base acceptable sound levels on
the time of day, the land use classification of the source, and nature of the receptors. For example,
a receptor in an industrial area would be weighted differently from one in a residential area.
(Composting Council, 1994) (7) (Sect. 9.4-p2)
Noise Reduction Measures
Noise generated by a yard trash processing facility can be mitigated in the following ways:
* Provide a buffer zone of vegetation, shrubs or trees around the perimeter that will lower
noise levels.
* Production equipment should have mufflers and noise hoods on engines.
* Provide a berm at the source of noise.
* Restrict noise-generating activities when wind direction and weather conditions are
unfavorable.
Pest and Insect Control
Properly managed yard trash processing facilities do not rodents or birds due to the lack of
a food source. The biological activity and the turning and management of the piles prevents the
creation of a suitable habitat for birds and rodents.
Insect control is important because Florida's climate provides an ideal habitat for insects.
There is a common misconception that yard trash may contain populations of pest insects such as
roaches, flies, mosquitoes, fleas, and termites. Although such pests may be delivered to a
processing site, they will be eliminated early during the shredding and windrow management
processes.
Data on actively managed yard trash mulch windrows indicate that insect populations are
found within top six inches of the windrow where the temperatures ranged from 80-105 degrees
F. All insect populations cease to exist at a depth of 6- 9 inches where temperatures range from
105-115 degrees F. (Smith, C. 1991). (9)
The following measures are recommended for the control of insects:
* Limit the time grass stays in the staging area to limit the hatching of fly larvae.
* Turn windrows frequently early in processing to maintain temperatures that kill insects.
* Store the finished products a considerable distance from fresh unprocessed feedstock.
* If the final product is stored for long periods, inspect periodically for insects and turn to
reheat if necessary.
Fire Prevention
Fires are rarely a problem in yard trash processing operations, primarily because a pile's
moisture content is between 40-60% and the material burns poorly (Simpson, H., Engel, P., 1989
?). (10) (p33) A yard trash processing facility receives a large quantity of combustible material
before it has been size reduced. This represents a high-potential fire hazard and proper
precautions should be taken. Possible ignition sources are discarded cigarettes, lightning,
vandalism, and spontaneous combustion.
There is also a potential for surface fires in finished mulch which may occur at ground
level under drought or extremely dry conditions and where there is an ignition source and where
there are strong prevailing winds.
Finished material generally burns on the top few inches of surface where it is driest.
Equipment fires also may occur from an accumulation of dust and wood chips left on a hot
engine, bearing, or component part that has not been cleaned off on a daily basis.
Fire can also ignite from inside the piles from spontaneous combustion. However, a rare
set of conditions must occur before a fire is possible. First, there must be vegetation with ample
nitrogen to fuel bacterial populations that generate heat. Since most microbes cannot live at
temperatures much above 160-175 degrees F., the continued heating of vegetation to their
ignition temperature is thought to be due to rapid oxidation initiated after bacterial preheating.
(_________________) (11)
Second, the material has to heat to over 200 degrees F. for an extended period of time
(Dickson, 1989) (12)
Third, the heat loss must be limited. Sufficient air must be available to permit oxidation,
yet not so much air that the heat is carried away by convection as rapidly as it is formed. An
example is the high piles of log chips that do not ignite where there is air space between the chips
that vents heat, but a bale of hay that is loosely packed with its insulating effect might provide
ideal conditions for heating (______________________). (13)
Spontaneous combustion becomes a possibility at a moisture content range of 25-45%. In
piles over 12 feet high, it is possible for the internal heat of the pile to initiate chemical reactions
leading to spontaneous combustion (Rynk, R.,et al, 1992). (14)
Operational procedures to minimize spontaneous combustion for storage of yard trash
should include the following:
* Incoming unprocessed materials should be stored in windrows or piles with a clear area
around each pile that is equal to the height of the pile.
* Avoid mixing new material with older material on the site, and thoroughly clean the
area before starting a new pile.
* Storage site should be level and on firm ground.
* Check pile temperatures of older piles of material.
* Avoid concentrations of fines during pile build up.
* Be aware that vehicle exhaust systems can cause fires.
Employee Safety and Health
A yard trash processing facility can operates on an industrial scale where heavy equipment
manipulates and moves large quantities of material. Such operating conditions require that
management concern itself with the industrial health and safety of employees by providing
protective equipment, training in safe equipment operation, and practicing fire prevention
procedures.
The following uses of employee safety equipment are recommended:
* Hearing protection should be worn at levels of 85 decibels or above. Ear muffs are most
effective.
* Safety goggles should be worn to protect the eyes from dust or projectiles.
* Leather gloves should be worn to protect the hands.
* A dust respirator should be worn to protect against airborne dust. A disposable
respirator that filters particles down to one micron in size is recommended.
The following safety training measures are recommended:
* Provide safety meetings on a regular basis.
* Instruct new employees on safe operation of all equipment.
* Instruct new employees on the proper safety procedures of the facility.
Employees should be trained with regard to equipment hazards and the potential
conditions that cause accidents, including the following conditions:
* Know the safe operation and design of equipment that has pinch points, wrap points,
cutting points, and entanglement risks from free wheeling parts (Cochran, B., 1995). (16) (p79-
88)
* Watch for pin leaks in hydraulic lines.
* Volume reduction equipment has a "hot" zone where projectiles may be thrown. Know
the direction of the hammermill rotation and the distance objects travel. A safety zone of 250
feet from the size reduction equipment should be established for unauthorized personnel.
Material Turning
Outdoor windrow turning in Florida generally uses front end loaders to aerate yard waste
compost and mulch. A loader is versatile and has the advantage of being capable of moving large
piles up to 10-12 feet high. A disadvantage is a lower production rate but this can be
compensated for by using oversized buckets.
Another type of windrow turner is a tractor-power assisted windrow turner or a self-
powered turner that is towed by a tractor. The advantage of this type of equipment is greater
volume movement and an increased decomposition rate. A disadvantage is that windrow height is
limited to 5-7 feet and width is limited to 14-18 feet. This requires more land to accommodate
smaller rows. .
The highest production windrow turner is the self-propelled model that straddles a
windrow. This equipment is used most often where there is high moisture and a greater potential
for odor production as in operations processing municipal solid waste and biosolids compost.
Disadvantages include the high cost of the equipment and its inability to manage the larger piles.
Windrow height is limited to 7-9 feet and width is limited to 14-20 feet.
Material Screening
Three types of screens are used in yard trash operations.
A portable trommel screen is used primarily for its high production in the separation of
fines. The design includes a charge hopper that feeds into a rotating drum. The tumbling motion
of material forces fine particles to be collected and stacked to the side and oversized material to
be discharged out end of the drum.
The shaker screen is a slanted vibrating deck where material rolls down and drops off. It
is used for scalping to separate logs, stumps, and demolition debris from soil. Two different
screen sizes generally are stacked in combination on two decks.
The satellite screen is a low-cost highly efficent screening machine for small operations.
References
1. United States Environmental Protection Agency. (1994). Composting Yard Trimmings and
Municipal Solid Waste. Washington D.C, (NTIS PB94-163250)
2. Cochran, B., Breitenbeck, G., Carney, B., McManus, R. (1995).
Composting (Organic Recycling) Compost Facility Operator Guide Supplement.Baton Rouge,La.:
Louisiana State University Agricultural Center.
3. Williams, T.O., and F.C. Miller. (1992, October). Odor control using biofilters, Part I.
BioCycle 33(10):72-77.
4. missing
5. United States Environmental Protection Agency. (1994). Composting Yard Trimmings and
Municipal Solid Waste. Washington, D.C. (NTIS No PB94-163250)
6. Composting Council. (1994). Compost Facility Operating Guiide. 1st Edition, Alexandria, Va.:
Composting Council.
7, Composting Council. (1994). Compost Facility Operating Guide. 1st Edition, Alexandria, Va.:
Composting Council.
8. Smith, W.C. (1995) (Insect Kill Temperatures in Compost Pile). Unpublished phone interview
data.
9. Smith, C. (1991). Additional Observations of Landfill Sites Similar to That Proposed for Nine
Nile Road. Unpublished Manuscript.
10. Simpson, M., Engel, P. (1989?). Leaf and Yard Waste Composting Manual. Prepared for
National Corn Growers Association, St. Louis, Mo.
11. The Chemistry and Physics of Fire-4-13 ____________?
12. Dickson, N., Richard, T. (1989). Correspondence. Department of Agricultural and Biological
Engineering, Cornell University. Ithaca, NY.
13. The Chemistry and Physics of Fire-4-13_________________?
14. Rynk, R., et al. (1992). Nn-Farm Composting Handbook. Northeast Regional Agricultural
Engineering Services, Ithaca, NY,
CHAPTER 8
PRODUCT CONSIDERATION
Quality assurance is an essential component of a yard trash processing operation. Quality
assurance starts at the source with public education. Information should be provided to
community residents about yard trash that is acceptable for recycling and how it should be
separated from other wastes to prevent contaminating materials that will enter the facility.
Quality assurance procedures should be followed to ensure that the final product is safe
and will have no adverse impact on the environment. Quality assurance practices also can reduce
the likelihood of nuisance conditions which may adversely affect the facility's relations with the
surrounding community.
Consistent and predictable product quality is an essential factor affecting the marketability
of compost and mulch. The level of quality assurance will determine the level of demand for the
product. Compost and mulch quality depends upon the biological, chemical, and physical
characteristics of the material. Some of the most desirable characteristics include:
Maturity (i.e., properly cured and stabilized)
Absence of weed seeds, plant pathogen, and contaminants (e.., plastic, glass, metal)
High organic matter content
pH range for designated end-use
Available nutrients (nitrogen, phosphorus, and potassium)
Low or undetectable levels of heavy metals and toxic organic compounds
Uniform particle size
Compost and mulch have numerous agricultural, horticultural, industrial, and forestry
uses. Depending on the end-use, products should be analyzed for the above characteristics. For
example, according to an EPA survey, (cite) the landscape industry has prioritized the desirability
of compost and mulch characteristics as follows:
VERY IMPORTANT Plant pathogens, weed seed, toxic substances, soluble salts, color
IMPORTANT Organic matter content, waterholding capacity, bulk density,
particle size, nutrient content, heavy metals, maturity and odor
LEAST IMPORTANT Moisture content, porosity, pH
In the processing of yard trash into mulch, it is important that the end product have
specific characteristics to sufficient to be able to adequately serve as a mulch. Those
characteristics include: prevent erosion of soil in heavy rains, reduce evaporation of soil moisture,
suppress weed growth, reduce soil compaction, and serve as a protective ground cover. Low
levels of fines and maintaining adequate structure for approximately three months is especially
important when the mulch will be used for paths, driveways, and parking areas. To many product
users, the color of mulch is an important element in the overall aesthetics of the landscape.
To encourage the expansion of compost and mulch markets, end-user confidence is
essential. Confidence in the marketplace can be increased by producing a consistent product and
by providing accurate information. The Composting Council has compiled a list of minimum
suggested chemical, physical, and biological parameters for compost. Table x. presents the
rationale for testing for each of those parameters.
Table x. Suggested Compost Parameters Summary
Compost Parameters Rationale for Inclusion
____________________________________________________________________________
pH Effect on pH adjustment
Soluble Salt Content Potential toxicity, effect on watering regime
Nutrient Content Effect on fertilizer requirements
Water Holding Capacity Effect on watering regime
Bulk Density Estimation/conversion of application rates
Moisture Content Product handling and transportation
Organic Matter Content Determination of application rate
Particle Size Determine usablitiy in specific applications
Nutrients
In addition to various soil conditioning effects, applications of quality composts to
croplands can improve nutrient content and availability. Composted plant materials, especially
those high in nitrogen, such as grass clippings, can supply nitrogen and thereby improve crop yield
and production, especially on poor, nutrient-deficient soils.
Improved yields for compost application have been reported with broccoli, tomatoes,
squash, sweet potato, potato, corn, rice, and other vegetables as well as improved growth of
turfgrass, citrus, onion, lettuce, and snapdragon, among others. Increases in the protein content of
some crops has been reported after compost applications. Potassium and phosphorous content of
soils and plants has also been increased with applications of compost to croplands. While reports
of sulfur increases due to compost applications have been inconclusive, it is generally believed
that sulfur, calcium, and magnesium, as well as zinc, manganese, and iron availability may be
increased by the use of compost in the root zone of crops.
In addition, the improvement of the soil organic matter, tilth, bulk density, and structure
afforded by compost applications can encourage earthworm and soil microbial cultures which can
further improve soil fertility and plant nutrition. Careful attention to the compost feedstocks can
impart quality nutrition in the final composts.
Recordkeeping
The importance of recordkeeping cannot be overstated and in some cases it may be
required by local or state regulatory agencies. It is a good practice to keep a log to track volumes
or weight of incoming yard waste and its origin. This data is useful in:
Developing estimates of amount of compost or mulch which will be produced.
Determining the adequacy of the site for handling projected amounts of yard waste
Isolating the origin of contamination problems and
Monitoring costs
Records should also be kept of any problems occurring and steps taken to resolve them.
These may be valuable in responding to inquiries about the facility's operations. Temperature
monitoring and ambient weather conditions should also be recorded. This information is
beneficial not only in monitoring temperature changes but in recognizing trends as indicators of
when windrows need to be turned.
Historical records should be kept for windrows, including date of formation, dates of
turning, temperatures, irrigation, and date of removal. Each windrow should be individually
identified.
Product Testing
To ensure quality, compost and mulch products should be laboratory-tested frequently. A
composite sample, composed of many small sample from different locations in the curing pile, will
provide the most representative results. Among the tests most commonly conducted are those
that determine the concentration of plant nutrients and toxic compounds. The compounds tested
for will depend on the feedstock and any applicable regulations. The presence of weed seeds and
phytotoxic compounds should also be monitored.
Pesticide and herbicides that may be present in yard trash feedstock are usually broken
down by microbes or sunlight within the first few days of the composting process. Many studies
have indicated that levels of heavy metals and pesticide residues detected in yard trash compost
and mulch is generally insignificant.
Representations of Product
In the marketing of mulch or compost it is important to be familiar with the provisions of
Florida's Commercial Fertilizer Law (Ch. 576, Fla. Statutes). Portions of the law are included in
the appendix.
Marketing Guidelines
The Compost Council Research Foundation has developed detailed instructional data for
specific compost end uses. A copy of the guidelines, "Popular Uses for Quality Compost," is
included in the appendix.
BEST MANAGEMENT PRACTICES MANUAL
FOR YARD TRASH MANAGMENT
APPENDIX
Please note: The materials included in this appendix
are preliminary, rough drafts due to time limitations.
GLOSSARY
Yard Trash-- vegetative matter resulting from landscaping maintenance and land clearing
operations. Florida Statutes 403.703 (15)
Yard Trash-- vegetative matter resulting from landscaping maintenance or land clearing
operations and includes materials such as tree and shrub trimmings, grass clippings, palm fronds,
trees and tree stumps. Rule 17-709.200 (15)
Yard Trash--grass clippings, leaves, weeds, brush, tree pruning of six inches or less in diameter
..and vegetative matter from land clearing activities, and from residential, commercial,
institutional, business and public lands and parks landscaping activities; does not include
putrescible material.(Compost Fac Opr Guide, Glossary)
Windrow--An elongated formation of yard trash material where the dimension of construction,
the particle size and the manner of rotation provide a state to control temperatures to sanitize the
material sufficient to remove weed seeds, insects and plant pathogens.
Compost--Chapter 62-709, F.A.C., defines compost to mean "solid waste which has undergone
biological decomposition of organic matter, has been disinfected using composting or similar
technologies, and has been stabilized to a degree which is potentially beneficial to plant growth
and which is used or sold for use as a soil amendment, artificial top soil, growing medium
amendment or other similar uses."
Yard Trash Composting--Is the conversion of fresh yard trash using a windrow or similar method
which undergoes biological, thermal, chemical and physical change converting its appearance and
structure into a mature humus product with a protective dark mantle to reduce nitrogen robbing.
Yard trash compost is higher in carbon to nitrogen ratio than the recommended 30:1, it is absent
the required primary plant nutrient levels found in fertilizer products such as manure compost with
a one half percent respective N.P.K. level. The benefit when the compost is used as a soil
amendment is moisture retention, soil aeration, reduced fertilizer leaching and slow release of
nutrients.
Compost Soil Product--Yard trash compost is similar to the definition of topsoil, it is a product
with high organic content but contains a lower mineral content of sand or clay than is found in
low organic topsoil. Compost soil products can be used as an artificial top soil, a potting soil, or
a soil amendment where it is sufficiently stable.
Processing --is materials handling on an industrial scale with increasing costs as end products go
from fuel, to mulch, to compost. It includes inspection of deliveries, stockpiling in staging area,
grinding, transporting, windrow building, rotating windrows for thermophilic kill temperatures to
"sanitize" the material for safe public distribution, final post process screening for compost
markets and final distribution.
Contamination--Foreign material, other than vegetative material,that can include plastic sharps
and metal fragments found in yard trash such as glass, concrete, rubber, leather, and cloth. Heavy
metals, toxic organic compounds, chemicals, and petroleum products at high levels can become a
pollutant. Inclusion of sand, clay or small particles of rock, shell or similar materials does not
constitute a contaminant. (Compost Fac. Op Guide, Glossary, supplemented)
Screened Material--A second production step to mechanically size classify material by the use of a
mechanical disc, vibrating or trommel screen to remove large objects and give a uniform size.
Aerobic Decomposition--the oxidation of organic matter into carbon dioxide and water by
microorganisms in the presence of air. (Compost Facility Operating Guide, Glossary)
Anaerobic Decomposition--occurring in the absence of oxygen, as in anaerobic respiration.
(Compost Facility Operating Guide, Glossary)
Curing--The last stage of composting that occurs after most of the readily metabolized material
has been decomposted or stabilized. It provides additional biological stabilization. (Compost Rac
Op Guide, Appendix)
Fresh Yard Trash--Unprocessed vegetation that has not gone through the windrow process and
thermophilic stage for pathogen kill.
Heavy Metals--Trace elements whose concentrations are regulated because of the potential for
toxicity to humans, animals or plants and includes copper, nickel, cadmium, lead mercury, and
zinc if present in excessive amounts. (Compost Fac Oper Guide, Appendix)
Humus--A complex amorphous aggregate, formed during the microbial decomposition or
alteration of plant or animal residues and products synthesized by soil organisms; principal
constituents are derivatives of lignins, proteins and cellulose combined with inorganic soil
constituents; dark or black carbon-rich relatively stable residue resulting from the decomposition
of organic matter. (Compost Fac Oper Guide, Appendix)
Inorganic--Substance in which carbon-to-carbon bonds are absent; mineral matter(Compost Fac
Oper Guide, Appendix)
Leaching--The removal of materials in solution by the passage of water through it. (Compost Fac
Oper Guide, Appendix)
Mature Compost--Is material that has gone through the windrow process for "sanitization" and
has been sufficiently cured for stability to not introduce phytotoxic acids or will not deplete soil
nitrogen to support additional biological decomposition but will be beneficial to soil and plants
grown in the amended soil.(Compost Fac Oper Guide, Modified ,Appendix)
Macronutrients--nutrients used by plants in high quantities.
Micronutrient--Are required by plants in small quantities but are toxic at high levels and include
boron, chlorine, copper, iron, manganese, molybdenum, and zinc.
Mulch--A soil surface cover used to retain moisture by retarding evaporation, discourage weed
growth, stabilize temperatures by insulating the soil, and stabilize the soil against erosion from
rainfall, (Compost Fac Opr Guide, Modified, Glossary)
Pathogen--an organism or microorganism, including bacteria, mold, fungus, virus, and protozoa
capable of producing an infection or disease in a susceptible host. Measures to control pathogens
include industrial hygiene, effective design and operation for biodegradation of pathogen nutrients
and for adequate and uniform aeration and temperature/time to assure pathogen destruction.
(Compost Fac. Oper. Guide, amended,Appendix)
Mulching--No state regulations exist for the sanitization of yard trash mulch. A modified version
of the FDEP compost rule for compost disinfection is recommended. This is based on the EPA
regulations specified in the Process to Further Reduce Pathogens (PFRP) found in 40 Code of
Federal Regulations Part 257 which requires that material in windrows maintain a minimum of 5
turnings. Based upon these standard, the University of Florida Institute of Food and Agricultural
Science (IFAS) established the following modified windrow temperature guidelines:
The processor must establish and maintain a minimum average temperature of 131 degree
Fahrenheit at 3 feet of depth for 72 hours after formation of windrow and after each of the 2
rotations of the windrow formed. (McConnell and Shirapour, 1990)
Phytotoxin--toxins which may endanger plant viability or functionality. (Compost Fac Opr Guide,
Appendix)
Primary Plant Nutrients--Plant foods including total nitrogen(N); available phosphoric acid
(P2O5) or phosphorous (P); and soluble potash (K2O) or potassium (K). (Compost Fac Oper
Guide, Appendix)
Soil Conditioner--Soil supplement which physically stabilizes the soil, improves resistance to
erosion, increases permeability to air and water, improves texture and resistance to crusting, eases
cultivation or otherwise improves soil physical quality. (Compost Fac Opr Guide, Glossary)
Stability--A level of biological activity in a moist, warm and aerated biomass sample. Unstable
biomass consumes nitrogen and oxygen to support biological activity and generates heat, carbon
dioxide and water vapor. Unstable, active compost demands nitrogen if applied to the soil and
can cause nitrogen deficiency in the soil mix and be detrimental to plant growth even causing
death of plants in some cases. (Compost Fac Oper Guide, shortened, Glossary)
Thermophilic Phase--phase in composting process where temperatures occur between 113 and
167 degree Fahrenheit. It is associated with specific colonies of microorganisms that accomplish
a high rate of decomposition. (Compost Fac Opr Guide, Glossary)
Vector--a carrier such as an animal, air current, and/or water stream that ingests or conveys
garbage, odor, microorganisms, and/or pathogens from one location to another. (Compost Fac
Opr Guide, Glossary)
Water Table--The upper surface of ground water.(Compost Fac Opr Guide, Glossary)
Clean Dry Wood--means wood (including lighter pine), lumber or tree and shrub trunks,
branches, and limbs which are free of paint, penthachlorophenol, creosote, tar, asphalt, or other
wood preservatives and which when burned does not emit excessive visible emissions. F.A.C. 62-
256.200(5).
Residuals--Material left after processing that is not recycled
OVERVIEW OF THE SOLID WASTE MANAGEMENT ACTS OF 1988 AND 1993
In 1988, the Florida Legislature passed the Solid Waste Management act which requires
each county to reach a goal of recycling 30 percent by weight of the solid waste generated by the
year 1994. This law further specified that yard trash represent no more than 15 percent of the 30
percent goal. At the passing of this act, Florida became one of a dozen states that would prohibit
the disposal of yard trash in lined landfills. The prohibition became effective January 1, 1992.
In 1993, the Florida Legislature modified the mandate by exempting all counties with a population
under 50,000 from having to reach the goal. It passed the Solid Waste Management Act
403.706(4)(d) that allows counties to receive credit for one-half of the 30 percent goal for waste
reduction by using yard waste or clean wood or paper waste in programs that produce alternative
clean-burning fuels such as ethanol or for clean burning fuel for production of energy for use at
facilities other than waste-to-energy facilities. Recycling credit only applies if the county can
demonstrate it has implemented a yard trash mulching or composting program and as part of the
program, compost or mulch made from yard trash is available to the general public and in use at
county-owned or maintained and municipally owned and maintained facilities in the county or
state agencies operating in the county.
One measure of the successful implementation of this legislation is reflected in a Florida
Department of Environmental Protection report on Solid Waste Management for the reporting
period of 1994. Counties reported recycling an estimated 1.6 million tons of yard trash that was
converted into compost or mulch. In Florida yard trash is 3.5 million tons or comprises 14.8
percent of the municipal solid waste stream.(4) This means Florida has a capture rate of 45
percent of all yard waste in the solid waste stream that was recycled. This surpasses the national
capture rate of 12 percent.(5) It must be noted where Florida gives credit for grass clippings
recycling left on lawns and the national average for the year 1992 did not give such credit.
FD EP RECYCLING POLICY
Yard trash recycling in Florida for 1994 reveals the state currently has 38 composting
facilities operating in 23 counties. A majority of these facilities utilize a windrowing process to
cure the compost material and 29 of the 44 facilities compost only yard trash. Three of 41
facilities are designed to compost MSW.(6)
Statewide participation by both public and private operators contributed to 1.6 tons of
yard trash being recycled in 1994. The Florida Department of Environmental Protection has
recognized the importance of this component of recycling and a need to simplify and revise the
Composting Rule 62-709 F.A.C.. They deserve commendation for their innovative approach to
deregulate through administrative code simplification.
In a policy statement issued by memorandum from John Ruddell dated May 10, 1995(1)
the DEP eliminated the permitting requirements and simplified minimum facility standards for
facilities that compost only yard trash. This policy statement memorialized through memorandum
is in effect while the composting rule 62-709 revision is in progress.
Concurrent with this regulatory review process the Florida Organics Recyclers
Association (FORA) contracted with DEP to develop Best Management Practices (BMP)
guidelines for the composting/mulching industry. Data collected from public workshops, research
and other published reference materials composes the major sections of the manual. The text
covers design, operation and material handling and is intended top contribute to the final compost
rule revisions.
A REVIEW OF THE MEMO'S KEY POINTS FOLLOWS:
Permit Requirements
* Current rule 62-709 requires facilities that compost under 3,000 yards per year to have a
general permit and facilities composting over 3000 yards to have a regular permit.
* Memorandum eliminated all permitting requirements
Inspection
Are required only upon complaint or when site is believed to be accepting material other than yard
trash or where violating DEP rules. Otherwise inspection is upon invitation for technical
assistance
Prohibition
62-701.300 Prohibitions,
(1)General Prohibition
(b) No person shall store or dispose of solid waste in a manner or location that causes air quality
standards to be violated or water quality standards or criteria of receiving waters to be violated.
(2)Disposal Unless authorized by a Department permit or site certification in effect on January 6,
1993, no solid waste shall be stored or disposed of by being placed:
(a) In an area where geological formations or other subsurface features will not provide support
for the solid waste;
(b) In any area where the absence of geological formations or subsurface features would allow for
the unimpeded discharge of waste or leachate to ground or surface water. A person may dispose
of solid waste in such an area upon demonstration to the Department that permanent leachate
control methods will result in compliance with water quality standards under Chapter 62-302 and
62-520, F.A.C.;
(c) Within 500 feet of an existing or approved potable water supply well unless disposal takes
place at a facility for which a complete permit application was filed or which was originally
permitted before the potable water supply well was in existence. This prohibition shall not apply
to any renewal of an existing permit that does not involve lateral expansion, nor to any vertical
expansion at a permitted facility;
(d) In a dewatered pit unless the pit is lined and permanent leachate containment and special
design techniques are used to ensure the integrity of the liner;
(e) In an area subject to frequent and periodic flooding unless flood protection measures are in
place;
(f) In any natural or artificial body of water including ground water;
(g) Within 200 feet of any natural or artificial body of water, including wetlands within the
jurisdiction of the Department, except bodies of water contained completely within the property
boundaries of the disposal site, which do not discharge from the site to surface waters. A person
may dispose of solid waste within the 200 foot setback area upon demonstration to the
Department that permanent leachate control methods will result in compliance with water quality
standards under Chapters 62-302 and 62-520, F.A.C. Stormwater control methods shall meet
stormwater requirements of chapter 62-25, F.A.C. However, nothing contained herein shall
prohibit the Department from imposing conditions necessary to assure that solid waste disposed
of within the 200 foot setback area will not cause pollution from the site in contravention of
Department rules.
(h) On the right of way of any public highway, road or alley; and
(i) Within 1,000 feet of any existing or approved potable water well serving a community water
system as defined in Rule 62-550.200 (9), F.A.C., unless disposal takes place at a facility for
which a complete permit application was __________ or which was originally permitted before
the water well was in existence. It is the intent of the Department that this provision shall be
repealed on the affective date of any rule promulgated by the Department which regulates
wellhead protection areas generally. This prohibition shall not apply to any renewal of any
existing permit that does not involve lateral expansion, ______ (not) to any vertical expansion at a
permitted facility.
(3) Burning. Open burning of solid waste is prohibited except in accordance with Rule 62-
701.520(2), F.A.C. Controlled burning of solid waste is prohibited except in a permitted
incinerator, or in a facility in which the burning of solid waste is authorized by a site certification
order issued under chapter 403, Part II, F.S.; clean vegetation and wood wastes may be burned in
an air curtain incinerator in accordance with Rule 62-2.500(1)(e), F.A.C.
Design Criteria
The following rule provisions apply to facilities that compost yard trash.
62-709.500(4) The facility site shall be provided with operational features and appurtenances
necessary to maintain a clean and orderly operation. These minimum features are:
62-709.500(4)(a) An effective barrier to prevent unauthorized entry and dumping into the facility
site;
62-709.500(4)(d) Dust control methods where needed to control problems;
62-709.500(4)(f) Fire protection and control provisions to deal with accidental burning of solid
waste or compost at the facility;
Operating Criteria
62-709.510(1)(b) The facility shall be operated in a manner, with any needed measures taken, to
control vectors and odors.
62-709.510(1)(e) More than half of the compost stored at the facility shall be used or sold for use
within each year beginning the third year after facility startup. Further, any compost remaining at
the facility for three years after it was produced shall be disposed of pursuant to the requirements
of Rule 62-701, F.A.C., or shall be reprocessed so that it can be sold or used.
Special Operating Criteria for minimal Technology
62-709.515(1) The composting material is turned at least once during a 12-month interval;
62-709.515(3) Particle size of larger yard trash items such as limbs, trees, and tree stumps are
reduced to promote composting;
Testing, Record Keeping and Reporting
Requirements under Rule 62-709.530, F.A.C., do not apply for facilities that compost yard trash.
While this record keeping provision will not apply, facilities should be encouraged to keep
appropriate records on the amount of material received and processed into compost, and the
amount of compost removed for use or disposal, in order to demonstrate that the facility is not
operating as a disposal facility.
Criteria for Use of Compost
Compost from yard trash shall have unrestricted distribution.
Closure
When such facilities close, all residuals, solid waste, compost and recyclable materials shall be
removed and recycled or disposed of.
Compost Definition 5E-1002(1)(c) "The term 'compost' means a substance derived primarily or
entirely from decomposition of vegetative and /or animal organic material, which is sold or
offered for sale for the purpose of promoting or stimulating plant growth, and to which no
inorganic fertilizer materials have been added other than to promote decomposition. Such
products shall contain not more than twelve percent (12) total plant nutrients."
(3) Soil amendment definition 5E-1002(1)(d) "The term 'soil amendment,''soil conditioner,' or 'soil
additive,' means any substance or mixture of substances sold or offered for sale for soil enriching
or corrective purposes, intended or claimed to be effective in promoting or stimulating plant
growth, increasing soil or plant productivity, improving the quality of crops, or producing any
chemical or physical change in the soil, except amendments, conditioners, additives and related
products derived solely from inorganic sources containing no recognized plant nutrients."
We are the Ones we have been waiting for.
When the people lead, the leaders will follow.
Why would you think that I speak for my employer?
Carol Meeds: mother, chemist, woman, warrior
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