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Publication #ENH125

Compost Utilization by State Departments of Transportation in the United States1

R.J. Black, G.L. Miller, and G. Kidder2

In 1996, nineteen state DOTs had specifications for compost, and thirty-four DOTs reported experimental or routine use of compost on roadsides. The following are some of the ways composts were used:

  • as a soil amendment

  • as a component in manufactured topsoil

  • as a mulch or topdressing

  • for erosion control

  • in hydroseeding

  • in wetlands mitigation

  • in filtration berms

  • in bioremediation

Each state has unique requirements that determine how its roadsides are developed and maintained, and compost markets likewise vary from state to state. While DOT compost utilization projects (or lack thereof) reflect these differences, the following are notable trends and issues about compost products:

  • product effectiveness

  • quality and safety

  • cost and availability

  • acceptance

Where composts are being used by a DOT or its contractors, the demand is for a product that is reliably mature, available in large quantities, meets specifications, is economically and qualitatively competitive with the alternatives, and meets state environmental standards. A summary of compost specifications in effect in 1996 by DOTs nationwide is presented in Table 1 .

Tables

Table 1. 

Table 1 (one of several pages). State DOT's' Compost Specifications in Effect in 1996.
STATE/Organization

Compost type

Date spec'd (when noted)


 Particle size/texture


 Color/odorOrganic content


 pHC:N

C:P


 E.C./Soluble salts


 Moisture (M)Bulk density(BD)

Water holding capacity (WC)


 Stability


 Inerts/non-biodegradable


 Heavy metals and other contaminants


 Rates of applicationGrades


 Tests or certifications required
Composting Council (preferred parameters for compost used as soil amendment for turf establishment).

June 1995


 Passes through 1" screen or smaller (preferred).

Acceptable size dependent on turf, compost & soil variables.


 Organic content may vary but must be reported; higher rates preferred and have some use as measure of value.
 5.5 - 8.0 (pH)
 May vary depending on tolerance of turf species. Max 4.0 dS/m for amended soil.
 35 - 55% (M)

BD must be reported.

WC must be reported.


 Stable to highly stable; must pass growth screening test.
 Avoid glass; minimize man-made inerts.
 Meets CC Model Regs based on EPA 40CFR 503.

Should be free of weeds.

Rates not to surpass turf's annual N requirement.


 135 to 270 cu yds per acre (1" to 2" layer incorporated to a depth of 5" to 7"- inclusion rate of 20 to 30% by volume).


 Content and availability of nutrients should be identified, particularly quantity and form of N.

Sol. salt, water holding cap., bulk density & organic matter content must be reported.
CONEG

1

Source Reduction Task Force (source-separated compost

2

for general use

3

).

February 1996


 <0.5 inch and

should meet state particle size standards for topsoil.

Loose & friable


 Min organic matter 30% (dry weight basis).4
 6.0 - 8.0 (pH)
 < 4.0 mmhos/cm (dS/m)
 M generally between 35-60%
 Stable according to specified testing methods5.
 Free of refuse or any material toxic to plant growth.
 Delimited by source-separation requirement. Source-separated compost has been proven to be far below EPA heavy metals standards.
 Evenly applied to depth specified in plans or by project Engineer. Shall not bury or kill existing vegetation.
 Certification that input materials(s) were source-separated if required by state purchaser.
Arizona DOT (composted wood or bark for use as soil conditioner).
 Min 85% must pass through a 6.3 mm sieve.
 Not less than 85% organic matter.
 7.5 or less (pH)

Min 0.5% N




As specified in the Special Provisions.
Arizona DOT

(composted steer manure for use as mulch).


 Must pass through a 12.5 mm screen (6.3 mm if used for lawns).


Must contain wetting agent or be hygroscopic.
 Well-composted and unleached; no visible amounts of undercomposed (sic) straw or bedding material.
 No stones.
 Free of sticks, stones, earth, weed seed, substances injurious or toxic to plant growth.
 As specified in the Special Provisions.






Shall comply with the requirements of the California Food and Agricultural Code

California DOT (soil amendment).6
 Shall be friable and pass a 25 mm sieve.


Relatively dry.

No living vegetation, dirt, objectionable material, pathogenic viruses, fly larvae, insecticides, herbicides, fungicides nor poisonous chemicals that would inhibit plant growth.
Shall be packaged so that compliance can be readily determined or shall be accompanied by a Certificate of Compliance.
California DOT interim specifications7 (composted mulch of recycled urban green material).
 At least 85% of particles must be between 1/2 & 3" long, no less than 3/8" in width and 1/16" in thickness.




Plastic, glass, metal or rocks shall not exceed 0.1%

(sic)

by volume.


 Composted to reduce weed seeds and deleterious material; shall not contain paint, petroleum products, herbicides, fungicides or other chemical residues harmful to plant or animal life.

California DOT District 7 interim specifications8 (mulch of composted urban green waste).
 Between 1/2 and 11/2" in thickness and 1" to 8" in length.



Grinding within 1 mo. of cutting. Composting in windrows for min. 120 days; min internal temp between 140-160o for at least 7 days.



Florida Dept. of Agriculture & Consumer Services
 At press time, specifications for compost procured by state agencies were in the process of being finalized
Georgia Dept. of Agriculture (composted organic materials)

12/29/93


 100% < 1" 90% < 1/2"
 Brown to black/ earthy.
 4.5-8.5 (pH) labeled and suitable to end use.
 Max

10 mmhos/cm, labeled and suitable to end use.


 30 - 50%
 May not reheat to 20o C above ambient temp.
 Plastic: max 1%

All other: max 2%


 Must comply with Ga. Environmental Protection Dept. requirements.
 Nutrient grade; soil amendment grade
 Quality assurance
Georgia DOT (organic materials that have undergone decomposition).
Dk brown or black / minimal odor.
 5 to 8 (pH)

Stabilized to degree beneficial to plant growth.
No human pathogens; does not contain levels of chemicals harmful to plants or humans.
List of ingredients in original mix in order of relative proportion by weight; test results on priority pollutants.
Illinois DOT

Current


 Thoroughly decomposed



Capable of germinating and supporting vegetation. Thoroughly decomposed.
 No glass or metal shards. No plastic or other manmade material larger than 4 mm and sieved out to be less than 1% of total dry weight.
At contractor's option or when specified, a blend of topsoil and compost (max 40% compost by volume) shall be substituted for topsoil.
 Must be produced by an Illinois EPA registered facility. Compost test results and cert. of IEPA registration must be provided to engineer with each shipment.
Maine DOT

Current


 See CONEG specs
Massachusetts Highway Dept. proposed standard specifications (compost

9

procurement for amending soils

10

).

October 1996


 1/2" or smaller/humus-like.


 Dk brown to black.

Min 40% organic matter (dry weight).


 5.5 to 8.0 (pH)

10:1 to 25:1(C:N)11


 < 4.0 mmhos/cm (dS/m) or

2560 ppm salt.


 No visible free

water or dust produced when handling.


 Stability must be assessed by either CO2 evolution test or reheating test.12
 Shall not be visible and should not exceed 1% dry wt.
 Per EPA 40 CFR 503 and Massachusetts

310 CMR 32.00 (for application to soils with human activity).


 Only Class A (Federal) or Type 1 (Mass.) products acceptable.
 The mineral content of the compost must be given including N, P, K, Mg, Na, Fe, Cu, B, Mn, and Mo.
Michigan DOT Special Provision

February 1996


 Max 1" diameter with less than 10% retained on a 3/4" screen.
 Dk brown or black.

Shall not have an objectionable odor.

10-50% organic content.


 6.0 to 8.5 (pH)

10:1-20:1 (C:N)


 1-7.5 mmho (sic)13
 No visible free water or dust produced when handling.
 Demonstrably mature / stable.14
 Less than 1% by weight. No visible plastic, glass or metal
 Meet EPA 40 CFR 503. Be free of viable weed seeds and other plant parts capable of reproducing (except airborne weed species).
 As directed by Engineer. Contractor can obtain compost only from manufacturers registered with the Michigan Dept. of Ag.
 Compost supplier shall certify that compost meets Michigan codes as well as EPA 40 CFR 503. Data sheet shall accompany and show total nutrient test results, organic content, inert contam, sol. salts, C:N ratio, proof of maturity / stability acceptable to Michigan Dept. of Ag.
Minnesota DOT

(Grade 1 compost for use in turf establishment. Nutrient-rich, derived from poultry or animal manure; no biosolids unless specified).


 Total breakdown of raw ingredients.

Texture similar to highly organic soil.


 Lack of odor.
 15:1

(C:N)15

Max 40% C

Min 2.5% total N

Min 2.5% total P

Min 1.5% total K16
In an air-dried condition at the time of delivery.
 Decomposition complete as evidenced by total breakdown of raw ingredients and lack of odor or heat generation.
 Free of plastic debris, stones, sand, glass and other extraneous matter. Material shall meet the Minn. Pollution Control Agency requirements for allowable levels of any inherent contaminants.
 No pathogenic material or weed seed. Material shall meet the Minn. Pollution Control Agency requirements for allowable levels of any inherent contaminants.
 Grades 1 & 2 (below)
 Compost shall be tested & approved by the engineer prior to delivery to the project. Prior to the engineer sampling the product, the contractor shall furnish a certification from the supplier that the material has been produced by accepted aerobic composting techniques employing turning or aeration, pathogen reduction & curing. The Dept. reserves the right to conduct bioassay testing of any material.
Minnesota DOT (Grade 2 compost for use as a landscape planting medium. Derived from decomposed leaves and yardwaste; no poultry or animal manure acceptable).
 Texture similar to shredded peat.
 As for Minnesota DOT Grade 1 compost, above.
 5.5 to 7.5 (pH)

Between 12:1 and 25:1 (C:N)

Max 10% ammonium N of total N.


 Max 15 mmhos/cm
 Moisture between 2% and 40%.17
 As for Minnesota DOT Grade 1 compost, above.
 As for Minnesota DOT Grade 1 compost, above.
 As for Minnesota DOT Grade 1 compost, above.
 Grades 1 (above) & 2
 As for Minnesota DOT Grade 1 compost, above.
New Jersey

(composted

sewerage [sic] sludge and wood chips)

Current.


 Per NJDEP interim guidelines.
 Min. organic content 50% by weight.
 No less than 6.0 pH
Average not more than 55%.
 Stabilized.


Certified weight and name of producer.
New York State DOT

draft revision to the Standard Specification for Source-Separated Compost.18


 < 12.5 mm

Loose & friable.


 Min. 30% organic matter (dry weight)19
 6.0 to 8.0 (pH)
 < 4.0 mmhos/cm

(dS/m)


 35-60% (M)
 Stable to very stable according to test method current on the date of advertisement for bids.
 Reasonably free of stones, refuse, materials deleterious to soil structure or toxic or detrimental to plant germination and growth.
 Free of sticks,

refuse and materials deleterious to soil structure or toxic or detrimental to plant germination and growth.
Acceptance of source-separated compost based upon the Producer's label or certificate of analysis by an approved laboratory indicating compliance with the materials requirements; delivery inspection by the Engineer.
North Carolina DOT

(composted poultry litter as specified in Request for Contract Quotations).

1996


 Pass through 5/8" screen.
 Slight to no odor.
 5.7 to 7.5 (pH)

Nutrients may not

be less than 90%

of the values in the contractor's quote.


 < 4.0 mmhos/cm

(dS/m)20


 < 40% (M) and no more than 15% over contractor's quote.
 Meets specified production criteria. Also, may not exceed 110

o

F after 5 days stockpiling

or increase more than 20oF in 24 hrs.


 Fillers added to poultry litter must be approved in writing by NCDOT.
 Zn & Cu < 2 lb/ton dry wt. Na <30 lb/ton dry wt. No hazardous materials. Free of specified noxious weeds & protected from non-noxious weeds. No poultry parts, mortalities, litter from houses contaminated w/ chlamydia.
List all components & relative percentage; product registered with Fertilizer Section of

NC Dept. of Ag.
Oregon DOT (compost for soil conditioning)21
 Fine texture (for composted ground bark).




Free of substances detrimental to plant life.
 Free of noxious weeds, living plants and rhizomes, and substances detrimental to plant life.


 Composted ground bark is acceptable only if 10 lb of 22-16-8 fertilizer is premixed to each 6 cu yd of compost or if 10 lb

of fertilizer is incorporated for each 1000 sq ft of compost applied in a 2" layer.
Pennsylvania DOT (sewage sludge/woodchips compost as mulch)22
 3/8" to 3"
 50% organic matter23
 6.0 min pH
Min 100% WC
 Nonburning, free of substances toxic to plant growth.
 Free of foreign material.
 Max ppm:Cd-25; Cr-1000;Cu-1000;

Pb-1000;Hg-10;

Ni-200; Zn-2500;

PCBs-3.
Submit a certified lab analysis with each shipment.
Texas DOT
 Compost material approved by the Engineer may be used as mulch or as 30% of backfill mix.
Free of stones or other foreign matter.
 Free of sticks

or clay.

US DOT / Fed Highway Admin (organic materials such as leaves, grass, shrubs, and yard trimmings).

1996


 12 mm max (sodding & seeding).

25 mm max (erosion control); friable.


 Dk brown / soil-like odor.

50% min organic.


 6.0 to 7.8 (pH)

25:1 to 35:1 (C:N)

120:1 to 240:1 (C:P)
40% max (M).
 Cured for 4 to 8 weeks.

Maturity is indicated by temperature stability & soil-like odor.


 2% max.
 Weed free, pathogen free.

Virginia DOT (composted leaf matter & yardwaste)

August 1995


 No recognizable woody fibers, seeds, or leaf structures.
 Average 40% organic matter.
 6.0 - 8.0 (pH)
Average BD <1250 lb/cu yd.
Free of stones & non-organic matter.
 Free of sticks, heavy metals, toxic matter.

Wisconsin DOT
 Compost shall be a standard commercial compost of cattle, sheep, or poultry manure or other organic material acceptable to the Engineer.
Washington State DOT (composted organic solid waste).

October 1996.


 100% must pass through 1" sieve.24
 Uniform dark, soil-like appearance. Min organic matter 30% dry matter.25
 5.5 - 8.5 pH26
 <4.0 mmhos/cm
Score a number 5 or above on the SolvitaTM Compost Maturity Test
 <1% manufactured inert material (plastic, concrete, ceramics, metal, etc.)27
 Shall comply with WS Dept of Ecology (DOE) Interim Guidelines for Compost Quality. Max ppm for Grades AA & A compost (respectively): As-20/20; Cd-10/39; Cr-600/1200; Cu-750/1500; Pb-150/300; Hg-8/17; Mo-9/18; Ni-210/420; Se-18/36; Zn-1400/2800.
 DOE recommended loading 200 dry metric tonnes per hectare annually. Greater applications may be permissible.

Grade AA compost recommended for home gardens & areas of possible direct ingestion by children.

Grade A compost recommended for topsoil blends, landscaping, ornamental, silviculture, sod farms, and similar apps.


 Prior to delivery, contractor shall supply unused set of compost maturity test kits; additional kits may be requested when testing needs exceed supply.

Acceptance of compost based on submittals by contractor.28
Wyoming DOT (sample Special Provision for landscaping with organic amendment of 25% composted sheep or cow manure and 75% mountain peat).
 Amendment to be coarsely ground & thoroughly mixed to ensure an even composition.
 Min 50% organic matter.
 5.5 - 8.0 (pH)
 Free from high salt content.

Free from stones and materials harmful to plant life.
 Free from clay subsoil, lumps, plants or their roots, sticks, weed stolons and seeds, debris, chemicals, or other materials harmful to plant life.

1

Coalition of Northeastern Governors.

2 See Notes on Terminology, p. 115.

3 "as a topdressing to established areas of turf, grass, or other ground cover growth for the purposes of improving soil fertility, aeration, and moisture-holding capacity..."

4 As determined by loss on ignition.

5 Dewar Self-Heating Test or Carbon Dioxide Generation Rate as described in the CONEG Model Procurement Specifications Appendix B.

6 In addition to other products, may also include, "a relatively dry organic compost derived from sewage sludge, plant material, or rice hulls."

7 Pending development of final specifications. Interim specifications are for compost used in erosion control and other applications.

8 See preceeding note.

9 May include composted biosolids, yardwaste, agricultural wastes, and source separated municipal waste. Not applicable for other processed organic residues (e.g. lime stabilized wastewater sludge).

10 Fully detailed by Switzenbaum et al. in Manufactured loam using compost material, Phase I: Feasibility. See Appendix C.

11 The reported C:N ratios before and after processing are to be preferred, together with total carbon.

12 For the CO2 test, the compost respiration shall be no more than 5 mg CO2-C/gBVS day. For reheating using the Dewar Self-Heating Test, the maximum heat rise should be no greater than 20o C above room temperature (20o to 25o C).

13 EPA 120.1 = Specific Conductance. EPA, ASTM or Equivalent Method.

14 Using an acceptable test, e.g. CO2 respiration or temperature self-heating tests.

15 Determined by the Kjeldahl method. All other testing will be according to current standard testing procedures of the Univ. of Minn. Soil Sci. Dept. Soils Testing Lab.
16

To obtain the N-P-K levels specified, the compost may be fortified with commercial fertilizer.

17 In accordance with ASTM D 2016, Oven Drying Method. All other testing according to current standard procedures at the U. of Minn. Soils Testing Laboratory.

18 Composted Sewage sludge must meet the applicable regulatory requirements of the NYS Dept. of Environmental Conservation (DEC) and requires an approved laboratory's certificate of acceptability provided by the producer of the compost. Composted sewer sludge used to amend or manufacture topsoil shall require a certificate from a laboratory approved by the DEC, verifying compliance with all applicable laws, rules and regulations and shall be supplied by the Contractor at the Contractor's sole expense.

19 As determined by loss on ignition.

20 Using a water to soil testing method of 2:1.

21 Includes spent mushroom compost, composted mint plant residue, approved commercially manufactured conditions made from composted sewage sludge amended with organic and inorganic materials or composted yard debris amended with inorganic materials, and fully composted, fine textured ground bark.

22 Specification will probably be modified to include compostes from other feedstocks as well as other applications (i.e. as topsoil and soil supplement).

23 Oven Dry Basis.

24 When tested in accordance with AASHTO Test Method T87 and T88.

25 As determined by loss on ignition (LOI test).

26 When tested in accordance with WSDOT Test Method 417.

27 On a dry weight or volume basis, whichever provides for the least amount of foreign material.

28 The submittals are: 1) A Request for Approval of Material Source, 2) a copy of Solid Waste Handling Permit issued to supplier, 3) written verification from the supplier that material complies with the processes, testing, and standards specified in the Interim Guidelines for Compost Quality, 4) written verification from the supplier that the compost products originate a min of 65% by vol from recycled plant waste. [A max of 35% by volume of other approved organic waste and/or biosolids may be substituted for recycled plant waste]. 5) a copy of the lab analyses [less than 3 mos. old] described under Testing Parameters in Guidelines for Compost Quality, and 6) a list of the feedstock by percentage present in the final compost product.





Footnotes

1. This document is ENH125, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date October 1998. Reviewed October 2003. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.

2. R.J. Black, associate professor, G.L. Miller, assistant professor, Environmental Horticulture Department, and G. Kidder, professor, Soil and Water Science Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.