Montana Composting Facility

United States Department of Agriculture Natural Resources Conservation Service Montana Operation and Maintenance Guide For Your Composting Facility

Operator: County: Location: Section: T: R: NRCS Office: Phone:

Compost is an organic product that has undergone a controlled biological transformation in order to achieve a stable product free from pathogens and weed seeds/plants. Compost is typically used as a soil conditioner, fine or coarse mulch, soil blanket for erosion control, planting bed establishment, etc. Large scale users of compost include farms, landscape contractors, highway departments, parks, golf courses, nurseries, land reclamation contractors.

The success of a composting operation is dependent on the ability to produce a quality product consistently. This goal can be best be obtained by implementing a systematic operation along with quality control testing. Protocol should be documented which identifies the planned feedstock and its quality, the physical handling process, a testing plan used during and at completion of the process, steps for odor control, and the target specifications for the end product.

The intensity of Operation and Maintenance protocol is dependent on the planned use of the end product. Composted products intended for sale or off-farm use require much more attention and detail in the operation and maintenance process. This is appropriate considering the producer is accountable for the quality of the end product.

PROJECT DESCRIPTION

Facility Description (e.g., type, size, number of animals, location, season of use, etc.):

Style of Composting:

Windrow Composting Aerated Static Pile Passively Aerated Windrows Rectangular Agitated Beds Bin Composting Rotating Drums Intended Use for composted product:

On-farm Landscaping Soil Amendment Bagged and Marketed Other

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FEEDSTOCK

Feedstock includes all components contributing to the compost mix. A key factor in producing consistent and high quality compost is the control and quality assurance of the feedstock contributing to the mix. Identify the compost feedstock and characteristics planned for this system.

Feedstock source and characteristics

List the types of animals that will comprise the Manure Source:

List the feed types that are used for each type of livestock:

List any additives, minerals or other products fed that could affect manure quality:

List the amendment (e.g., straw, wood chips, etc.) to be used in the compost mix:

List any additional amendments available or planned for use in the compost mix:

List the source and type of watering system utilized and/or planned for in the composting process:

Feedstock Testing

A successful composting process involves appropriate proportions of a nitrogen source (manure), a carbon source (amendment) and moisture. Formal laboratory testing is needed to describe the pertinent feedstock characteristics needed to develop the compost recipe. Continued feedstock testing, on a pre- determined schedule, should also be conducted for facilities where off-farm use is planned. This provides the operator information to adjust the mix if needed and identify the variability in quality of the feedstock source.

Testing for feedstock materials should, at a minimum, include:

* Moisture Content * pH * Total Nitrogen * C:N ratio

Additional tests that are beneficial include quantifying Ammonium, Phosphorus, Organic Matter, and Soluble Salt contents. Appendix A provides a list of laboratories available to complete these tests. Other laboratories local to the site may also be available.

Sampling frequency of the feedstock is dependent on the composting style utilized as well as the intended use of the compost end product.

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• If manure and/or amendments are added to the composting system throughout the year, monthly sampling is recommended. This level of sampling may be reduced to quarterly or semi-annually for on-farm planned use and/or once the system is well established and consistency of the input materials is realized.

• If manure and/or amendments are collected from open lots only once or twice per year, sampling is recommended as often as feedstock is collected. Sampling frequency can be reduced to once every few years for on-farm planned use once the system is well established.

Sampling Protocol

In order to be meaningful, feedstock samples need to be representative of the pile from which it was collected. The following sampling procedure outlines a standard method by which a representative sample can be obtained.

1. Collect many (≈ 20) samples from different locations in the “pile.” Each sample should be at least 60 in3 (e.g., 4” x 4” x 4” cube). 2. Avoid taking samples from the edges and outer surface which are likely to have different qualities from the bulk of the material in the pile. 3. Mix samples together and form a small pile. 4. Draw sub-sample from the mix by cutting the pile into quarters and selecting a quarter. Continue to pile and quarter until the appropriate sample size, as specified by the laboratory, is obtained. Typical sample size fills a quart-sized Ziploc bag. 5. Double bag the samples in Ziploc bags and refrigerate until the time of shipping. 6. Ship packaged samples in a polystyrene (insulated) container along with a frozen gel-pack to avoid over-heating or cooling. 7. Ship samples as soon after sampling as possible. Samples stored more than 7 days should be discarded and re-collected.

Other Feedstock Considerations

In addition to sampling and testing the feedstock quality, other Best Management Practices (BMPs) exist by which feedstock quality can be encouraged. The following BMPs are noted. Others may be appropriate and become evident as the facility operates.

• Feedstock materials should be “clean” i.e., free from trash, pesticide residue, metals, etc. • Woody materials decompose slowly and may need to be screened from final product. • Small particles are preferred over larger particles of the same material as they compost more rapidly and encourage product uniformity. • Unplanned additions of moisture can be problematic in compost handling and processing.  Control contributions from rainwater by providing drainage control and roof coverage.  Eliminate nuisance leaks such as leaky waterers.

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COMPOSTING PROCESS

The Mix

Controlled decomposition requires a proper balance of “green” nitrogen-rich, “brown” carbon-rich organic materials, aeration, and moisture. General guidelines along with a mix recipe for your operation are provided below.

Table 1. General Guidelines for Mix Characteristics

Characteristic Reasonable Range Preferred Range Carbon to Nitrogen (C:N) ratio 25:1 – 40:1 25:1 – 30:1 Moisture Content 35 – 65% 50 – 60% pH 5.5 – 9 6.5 – 8.5 Bulk Density (lbs/yd3) Less than 1100 (40 lbs/ft3) - - - - Ref. On-Farm Composting Handbook, NRAES-54, June 1992

A site specific mix recipe has been developed using data from the feedstock analysis (see below). These values should be considered a “starting” point. Monitoring and experimentation will be required to fine tune and optimize for composting efficiency.

Site Specific Compost System Recipe

Target Carbon to Nitrogen (C:N) ratio: Carbon _____: Nitrogen _____

Target Moisture Content: %

Manure Type: Wet Weight: lb % of Total Mix: Amendment #1: Wet Weight: lb % of Total Mix: Amendment #2: Wet Weight: lb % of Total Mix:

Moisture to add at start-up: lb water/lb mix

Computation sheets are available to develop a compost mix recipe. They are attached in Appendix B and available in EXCEL format at the Montana NRCS web page under Technical Resources, Engineering, Manure and Nutrient Management Section. These computational sheets can be useful to calculate mix adjustments as additional feedstock analysis data becomes available.

Active Composting and Curing Time

The composting process is typically comprised of an “active” composting phase and a curing time. The active composting phase is when the majority of composting occurs. Materials are mixed together, microbial activity begins, the pile temperature increases, peaks, and then drops off as the feedstock and/or pile conditions (oxygen, excessive temperatures, etc.) become limiting. The speed of composting and the quality of finished compost are largely determined by the selection, quality, and mixing of the raw materials including moisture. Curing occurs after the active composting stage. While curing, the materials continue to compost but at a much slower pace. Temperatures are in the 50 to 105 degrees F range and oxygen consumption, heat generation, and moisture evaporation are much lower. This phase provides a safety net for either shortened or poorly managed composting and reduces the chance that an immature compost will be used.

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Active Composting:

Active composting takes place within two temperature ranges known as mesophilic (50-105o F) and thermophilic (over 105o F) ranges. Most pathogens and fly larvae will be destroyed by maintaining the compost at 130o F for at least 3 days (EPA). A temperature of 145o F is needed to destroy weed seeds. On the other hand, microorganisms begin to suffer if temperatures exceed 140o F. If this occurs, the composting process will slow down.

Compost planned for on-farm use should obtain a temperature of at least 130 degrees F. Compost planned for off-farm use should obtain the 130 degrees F temperature for a minimum of 3 days. This temperature requirement extends to 15 days for passive windrow-style composting.

The critical variables to achieve the shortest period of active composting are:

• Moisture content • C:N ratio • Adequate aeration.

Optimizing the composting efficiency can best be achieved by attention to an active feedstock sampling program, management with material selection and pile handling to ensure proper aeration, and pile monitoring for temperature and moisture content. See Appendix C for guidance regarding monitoring temperature and moisture content.

Curing:

Curing is a critical step to achieving mature compost when targeting a quality compost product. Without this step, there is a high risk for immature compost to be the end product which can have a detrimental effect on plant health. In addition to assuring the compost is mature; curing also increases the concentration of humus, shifts the pH toward neutral, converts Ammonium to Nitrate, and re-colonizes soil microorganisms that promote disease-suppressing qualities.

Estimated time lengths for active composting and curing are listed in Table 2 for various types of composting styles. Similar to the mix recipe, these time lengths provide a starting point from which site specific time lengths can be developed with experience.

Table 2. Estimated time for active composting and curing

Active Composting Time Curing Time Method Range Typical Passive Composting 6 months - 2 years - - - - 1 year Windrow – frequent turning 1 - 4 months 2 months 1 - 2 months Passively aerated window 10 - 12 weeks - - - - 1 - 2 months Aerated static pile 2 - 4 weeks 3 weeks 1 - 2 months Rectangular agitated bed 2 - 4 weeks 3 weeks 1 - 2 months Rotating drums 3 - 8 days - - - - 2 months Vertical silos 1 - 2 weeks - - - - 2 months Ref. On-Farm Composting Handbook, NRAES-54, June 1992

Aeration

Providing adequate ventilation to the compost is critical in achieving an efficient composting system. It also is important during curing and storage in order to maintain a healthy, odor-free, facility. Without adequate ventilation, compost can become anaerobic which leads to odor problems and acidic conditions.

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Following are guidelines for proper aeration for differing composting styles:

Windrow Composting:

Windrow composting aerates primarily by natural air movement. The porosity of the compost mix determines the allowable size of the windrow to maintain this air movement. The typical height for windrow composting is 3 feet.

• Turning is necessary with this style of composting to restore pore space and porosity after decomposition and settlement has occurred. Turning also promotes uniform composting as temperature variations occur within the pile structure.

• Windrow temperatures and odors indicate when turning is needed. Low temperatures (< 120o F) or a significant drop in temperature indicates turning is needed. Turning is also needed when temperatures exceed 140-150o F. High temperatures that cannot be controlled by turning may indicate the pile is too large.

• More frequent turning reduces the length of the time for composting. Easily degradable or high nitrogen mixes may require turning as frequently as daily during the start of the active composting process. Composting intended for off-farm use should be turned at least 5 times during the active composting phase.

• If fly control is a concern, the pile should be turned at least once per week during the fly season to break the flies’ reproductive cycle.

Passively Aerated Windrows:

Passively aerated windrows incorporate open ended, 4-inch diameter perforated pipes through the base of the pile at 12-inch spacings. Air movement is drafted into the open ended pipes as hot gases rise through the pile. Typical pile heights are 3-4 feet.

• Turning is not required with passively aerated windrow composting.

• Because turning is not incorporated into the composting process, it is essential that raw materials are well mixed when placed in the row.

• The mix recipe must include materials that provide for good structure and porosity. Recommended amendments include straw and/or wood chips for solid materials and peat moss for slurry-like materials.

Aerated Static Pile:

Aerated static piles are windrows that utilize a pipe network and blower fans to distribute air through the pile. Advantages of an aerated static pile are that active composting can be completed in as little as three to five weeks, the amount of aeration is controlled, and the material can be stacked in larger piles (5-8 feet high).

• Turning is not required and initial mixing of the raw materials is critical to obtain a well mixed pile.

• The pile must have good structure which maintains porosity. This is accomplished by using appropriate amendments such as straw and/or wood chips.

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• On-and-off operation of the blower system can be on a fixed time schedule. Typically the blower should operate one-half to one-third of the total time cycle. The blower off time should not exceed 30 minutes. As the compost temperature rises, the blower ‘on’ time can be extended to increase cooling. Similarly, shorten the blower ‘on’ time as active composting declines.

• On-and-off operation of the blower system can also be controlled by pile temperature through the use of electronic temperature sensors. The sensor controls should be set so that the blower comes on to provide cooling when the pile temperature rises above 135o F. The blower should shutoff when the temperature drops to 130o F. During pile startup, the blower should run on a fixed time schedule. For this type of control, the temperature sensor should be placed at least 18 inches below the pile surface and at two-thirds the length of the pile as measured from the blower end.

In-Vessel Composting:

In-Vessel Composting refers to a group of methods which confine the compost materials within a building, container, or vessel. These methods typically rely on a variety of forced aeration and mechanical turning. Mechanical turning includes such techniques as augers systems, rotating drums, or turning machines.

Bin Composting:

Bin composting is a simple form of In-Vessel composting as the compost is contained by walls and, typically, a roof. Bin composting methods operate similar to the aerated static piles and blower forced air should be incorporated into management plan especially when compost is planned for off-farm use. Moving the pile from one bin to the next can also be incorporated to promote mixing, incorporate oxygen, and invigorate the process. Bin heights that exceed that typical of an aerated static pile may require greater air pressure or more attention to strong structure in the feedstock for porosity.

Odor control

Odors generate from essentially three primary sources: odorous raw materials, ammonia loss from high- nitrogen materials, and anaerobic conditions within windrows and piles. If odors become a problem consider the following:

• Start composting raw materials as soon as possible and avoid long storage periods. • Avoid overly wet mixes. • Turn or aerate the materials more frequently. • Add amendments (straw, sawdust, peat moss, and mature compost) to increase air space and carbon in the mix. • Direct exhaust air from an aerated static pile through an odor-absorbing filter. A 2-3 foot tall pile of finished compost serves well as a filter. • Dilute odors by moving a large volume of fresh, outside air through the facility.

QUALITY CONTROL

A consistent, high quality product which meets customer’s expectations is essential for success when producing compost for market. Any material that is produced with the intent to use “off-farm” should be tested by a certified laboratory for compost quality. The intended use defines the extent (what and how often) to which product testing should occur as well as the criteria to which the compost should meet. Testing criteria and recommended ranges for a variety of the common uses are listed in Table 3.

Manure compost is not often recommended for use with container-grown plants or as a growth media due to its relatively high soluble salt content. If planned for this use, compost should be mixed with other

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materials (peat moss, coarse sand, wood residual) at a rate no greater than 20-30% of the entire mix. Furthermore, compost intended to be used for container-grown plants should be tested with the utmost care to meet high-quality standards.

Manure compost intended for use as a soil amendment should consider the nutrient levels in addition to the criteria listed in Table 3 when determining application rates. It is important to remember that only 8- 12% of the nitrogen in the compost is available for plant growth in the first year. Generally speaking, compost can be applied at a 1-2 inch thickness and then incorporated into 6 to 8 inches of soil.

Table 3. Compost Test Criteria

Recommended Range Potting Mulch/Top Soil Parameter Units of Measure Grade1/ Dressing2/ Amendment3/ pH pH units 6 - 8.5 5.5 - 9.0 6 - 8.5 Moisture Content %, wet weight basis 30 - 60 30 - 60 30 - 60 Organic Matter Content %, dry weight basis 30 - 65 > than 30 30 - 65 Soluble Salt Concentration dS/m (mmhos/cm) < 6 < 10 < 10 % passing a selected mesh 99% < 3” Particle Size size, dry weight basis 99% < ½” 25%+ < 3/8” 99% < ¾” Physical Contaminants (inert material) %, dry weight basis < 1 < 1 < 1 Trace Metals Pass/Fail 4/ 4/ 4/ MPN per gm per dry weight <1000 MPN <1000 MPN <1000 MPN Fecal Coliform Salmonella MPN per 4 gm per dry weight <3 MPN <3 MPN <3 MPN Stability Indicator CO2 Evolution Rate mg CO2 -C per g OM per day < 8 < 8 < 8 Maturity Indicator (bioassay) Seed Emergence %, relative to positive control Minimum 80 Minimum 80 Minimum 80 Seedling Vigor %, relative to positive control Minimum 80 Minimum 80 Minimum 80 1/ Potting Grade: Compost used within a blend of materials to formulate a potting mix or seed bed. Compost should not exceed 20-30% of the mix. Soluble Salt content of the mix should not exceed 2.5 dS/cm to 4 dS/cm depending on the plants to be grown. 2/ Mulch/Top Dressing: Compost is applied to the soil surface to help inhibit weed growth, conserve soil moisture, and reduce soil erosion. Compost is typically applied at a 1-2 inch thickness. Contact with tree trunks or plant stems should be avoided. 3/ Soil Amendment: Compost is incorporated into the soil to improve soil quality (organic matter, water-holding capacity, aeration, drainage, and exchange capacity). Typical blends for soil amendment use is one part compost to two parts soil. 4/ Meet or exceed US EPA Class A standard, 40 CFR 503.13, Tables 1 and 3 levels (Arsenic 41 ppm, Cadmium 39 ppm, Copper 1500 ppm, Lead 300 ppm, Mercury 17 ppm, Molybdenum 75 ppm, Nickel 420 ppm, Selenium 100 ppm, Zinc 2,800 ppm). Ref: On-Farm Composting Handbook, NRAES-54, June 1992 E&A Environmental Consultants. Landscape Architect Specifications for Compost Utilization, Dec. 1997. Prepared for Clean Washington Center (CWC) and The US Composting Council.

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APPENDIX A

Analytical Laboratories Prepared to Test Compost and Feedstock Materials

The following list of analytical laboratories has been compiled by the United States Composting Council (USCC). These laboratories have been approved for use by composters participating in their “Seal of Testing Assurance” program. This list is also located on the USCC website at www.compostingcouncil.org and should be referenced for updated information.

Other laboratories equipped to complete feedstock and compost quality testing may also be available. Montana State University Bulletin EB150, Issued January 1998, lists Soil, Plant, and Water Analytical Laboratories for Montana Agriculture. This document is available at the website www.montana.edu. Many of these laboratories, some of which are included below, are likely able to assist with some or all of the recommended testing.

USCC “Seal of Testing Assurance” Approved Laboratories:

A&L Canada Laboratories A&L Great Lakes Labs 2136 Jetstream Rd. 3505 Conestoga Drive London, Ontario N5V3P5 Canada Fort Wayne, IN 46808 Tel: 519-457-2575 Tel: 260-483-4759 Email: [email protected] Email: [email protected] Website: www.algreatlakes.com

A&L Western Laboratories, Inc Ag Analytical Services Lab 1311 Woodland Ave Penn State University Suite 1 Tower Road Modesto, CA 95351 University Park, PA 16802 Tel: 209-529-4080 Tel: 814-863-0841 Email: [email protected] Email: [email protected] Website: www.aasl.psu.edu

Colorado Analytical Laboratories, Inc Midwest Laboratories, Inc 240 S. Main St. 13611 B St Brighton, CO 80601 Omaha, NE 68144 Tel: 303-659-2313 Tel: 402-334-7770 Email: [email protected] Email: [email protected] Website: www.coloradolab.com Website: www.midwestlabs.com

Soil Control Lab 42 Hangar Way Watsonville, CA 95076 Tel: 831-724-5422 Email: [email protected] Website: www.compostlab.com

Situ Biosciences LLC 3415 Howard St. STE. 102 Skokie, IL 60076 Tel: 847-677-4547 Email: [email protected] Website: www.situbiosciences.com

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USCC “Seal of Testing Assurance” Approved Laboratories (continued):

Soil Test Farm Consultants 2925 Driggs Dr. Moses Lake, WA 98837 Tel: 509-765-1622 Email: [email protected] Website: soiltestlab.com

Texas Element Inc. 815 Brazos St. Austin, TX 78701 Tel: 512-944-7151 Email: [email protected] Website: texaselement.com

Texas Plant and Soil Lab 5115 W. Monte Cristo Road Edinburg, TX 78541 Tel: 956-383-0739 Email: [email protected] Website: TexasPlantAndSoilLab.com

Western Labs 211 W. Hwy 95 Parma, ID 83660 Tel: 208-722-6564 Email: [email protected]

Woods End Lab 290 Belgrade Road Mt. Vernon, ME 04352 Tel: 207-293-2457 Email: [email protected] Website: www.woodsend.org

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Refer to Montana NRCS web page: Technical Resources/Engineering/Engineering Software and Spreadsheets for Appendix B.

APPENDIX B CALCULATION OF COMPOST RECIPE FOR RAW MATERIALS ANALYZED ON A DRY W EIGHT BASIS

Desired C:N Ratio: R

Desired Final Moisture: % MCfinal

Material A: MANURE MATERIAL B:

% moisture content (wet basis), MCa : % % moisture content (wet basis), MCb: %

C:N, Ra C:N, Rb

% Nitrogen (dry basis), Na : % % Nitrogen (dry basis), Nb: %

% Carbon, Ca: % % Carbon, Cb: %

Assume 1 lb of manure Assume 1 lb of material B; S = # of pounds of material B

Wt of Water, Wwa = ((%MCa/100)*1 lb) = lb Wt of Water, Wwb = ((%MCb/100)*1 lb) = lb

Wt of Dry, Wda = (1lb - Wwa) = lb Wt of Dry, Wdb = (1lb - Wwb) = lb

Wt of Nitrogen, Wna = ((%Na/100)*Wda) = lb Wt of Nitrogen, Wnb = ((%Nb/100)*Wdb) = lb

Wt of Carbon, Wca = (Wna*Ra) = lb Wt of Carbon, Wcb = (Wnb*Rb) = lb

S = (%Na) (Ra- R) (1-(Wa/100)) = lbs of Material B (%Nb) (R-Rb) (1-(Wb/100)) lb of moist manure

Overall Mix Percentage: % Manure: 1 pound x 100 = % Manure (By Weight, NOT Volume) 1 lb + S

% Material B: S x 100 = % Material B 1 lb + S Check Moisture Content:

MCmix = Wwa + (Wwb*S) = x 100 = ______% MCmix 1 lb + S

Moisture to Add: Wt water to add = ((MC final/100) - (MC mix/100))/(1-(MC final/100)) pound of moist mix = ______lbs water lb moist mix

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APPENDIX B - Continued CALCULATION OF COMPOST RECIPE FOR RAW MATERIALS ANALYZED ON A W ET WEIGHT BASIS

Desired C:N Ratio: R

Desired Final Moisture: % MCfinal

Material A: MANURE MATERIAL B:

% moisture content (wet basis), MCa: % % moisture content (wet basis), MCb: %

C:N, Ra C:N, Rb

% Nitrogen (wet basis), Na: % % Nitrogen (wet basis), Nb: %

Assume 1 pound of manure Assume 1 pound of material B S = # of pounds of material B

S = (%Na) (R - Ra) = = lbs of Material B

(%Nb) (Rb-R) lb of manure

Overall Mix Percentage: % Manure: 1 pound x 100 = % Manure (By weight, NOT volume) 1 lb + S

% Material B: S x 100 = % Material B 1 lb + S

Check Moisture Content:

MCmix = Wa/100 + (Wb/100*S) = x 100 = % MCmix 1 lb + S

Moisture to Add: Wt water to add = ((MCfinal/100)-(MCmi x/100))/(1-(MCfinal/100)) pound of moist mix = __lbs water__ lb moist mix

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APPENDIX C

On Farm Compost Monitoring and Testing

Composting is a biological process that needs monitoring and management throughout the composting period to insure proper composting processes. The operation may need to undergo some trial and error in the start-up of a new composting facility. Manage the compost piles for temperature, odors, moisture, and oxygen, as appropriate to assure that the required decomposition has been reached.

The extent and level of testing of the composting process is directed largely by the intended use of the compost and expectations of the customer. Compost marketed “off-farm” should be tested for quality on a regular basis by an approved laboratory (see Appendix A). Compost used “on-farm” may not require laboratory level testing with the frequency recommended for a market type material. Even in this case though, it is recommended laboratory testing be completed at least annually until the composting system is well established and material of quality can be produced with confidence.

Monitoring during the composting process is helpful to assure a quality end product. Provided below are directions for moisture content, temperature, bulk density, and odor test procedures. These tests can be run by the producer and are informative as per the stage of the composting process.

Moisture Content

Moisture is important in the mix as microorganisms can utilize only those organic molecules that are dissolved in water. On the other hand, too much moisture will reduce porosity, take up space intended for oxygen, and drown out microorganisms.

Measuring Moisture Content

Equipment needed: Microwave or conventional oven, small, oven safe container, 0.1 lb precision scale

Procedure: • Sample pile…. • Mix sample thoroughly • Weigh Container, C • Weigh Container and a 4-ounce (100 gram), approximate, portion of sample, Ww. • Dry sample in microwave or conventional oven until the weight stays constant (within 1% of its previous weight) between two consecutive drying times. --Microwave estimated drying time: 8 minute at full power (600 Watt microwave) and subsequent intervals at 2 min. --Conventional Oven estimated drying time: 24 hours at 140o F to 220o F • Re-weigh sample for dry weight, Wd • Calculate moisture content, ((Ww -Wd)/(Ww -C)*100

Note: Drying sample for too long in the microwave or at too high a temperature in the oven can burn off organic matter within sample resulting in erroneous test results.

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The target moisture content for compost is 50-60%. A “squeeze test” (Federal Compost Quality Assurance Organization, 1994) provides a rough estimate of moisture content. This test gives an indication as to whether materials may be “too dry” or “too wet” for composting.

Squeeze Test

Pick up a small handful of compost and squeeze firmly. Open fist and evaluate structure of sample.

 The sample is sufficiently moist for composting, if it holds together when the hand is opened but breaks apart when light pressure is applied.  The sample is too wet if it does not fall apart when light pressure is applied or releases water into the hand when squeezed.  The sample is too dry if it falls apart or crumbles when the hand is opened.

Temperature

Temperature is an important indicator of how well the compost process is performing. High temperatures (> 130o F for 3 days minimum) assures that pathogenic microbes and (> 145o F) weed seeds/plants are being destroyed. Temperatures that are too low indicate poor feedstock materials or proportions. It can also mean aeration is inadequate. Temperatures that are too high (> 150o F) indicate aeration is needed.

Measuring Temperature

Equipment Needed:

A hand-held dial thermometer or fast response digital style. Both styles should have a 3-foot long probe and a temperature range encompassing 50-200o F.

Procedure:  Measure the pile temperature at a 12-18 inch depth and at varying locations along its length and width.  Record Daily

Note:

 Temperatures will vary throughout the pile due to uneven mixing.

 A temperature gradient will develop from the hot inner core to the cooler surface temperature.

Bulk Density

Bulk density is a measure of mass per unit volume of the material mix. The volume incorporated into this measure is not only of the material itself but also the air spaces within the sample. Thus, the bulk density value gives an indication of the ability of air to move through the pile. A high bulk density (greater than 40 lb/ft3) indicates the need for a bulking agent and/or turning to improve porosity. Moisture content and compaction will also affect the bulk density of a material mix, increasing its value with increased mass and decreased volume.

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Measuring Bulk Density

Equipment Needed: A bucket or container and a scale with 1 lb precision

Procedure:

1. Weigh the empty container, Wcontainer, (lb) 2. Calculate the Volume (ft3) of the container by: a) Weigh the container while completely full with water. Subtract the weight of the container and then divide by 62.4 lb/ft3. or, for containers with easily measured dimensions, b) Measure the width, depth, and height of the container and calculate volume. 3. Place the material to be weighed (feedstock or compost mix) in the container with the same amount of compaction as occurs in the pile. Fill the container to the top.

4. Weight the filled container, Wfilled, (lb) 3 5. Calculate the Bulk Density as (Wfilled – Wcontainer)/Volume, (lb/ft )

Odor

Strong putrid odors are a sign that something is wrong. Likely, the pile has entered into an anaerobic condition and increased aeration is needed. Visit the compost at least daily and be alert to excessive odors.

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