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Waste Analysis

Table of Contents

Why Waste Analysis?

Waste Analysis Services

Sampling Procedures

Understanding the Waste Analysis Report

Monitoring and Record Keeping

Prepared by
J. P. Zublena, Associate State Program Leader ANR/CRD, North Carolina Cooperative Extension Service, NCSU;
C. Ray Campbell, Section Chief; Plant/Waste/Solution Advisory, Agronomic Division, NCDA

Published by
North Carolina Cooperative Extension Service

Publication AG-439-33
June 1993 (JMG)

Last Web Update:
December 1997 (DBL)

Agricultural, industrial, municipal, and yard wastes can be valuable to farmers provided they are properly managed. Waste analysis is an important key to proper management. By determining the amount of nutrients and potentially harmful elements in the waste, and by determining the prodluct's liming characteristics, growers and other potential users of these materials can make informed decisions about their application. From both an economic and an environmental standpoint, this information benefits all North Carolinians.

This fact sheet will clarify the importance of waste analysis and describe the procedures for taking reliable samples and submitting them to the Waste Advisory Section at the Agronomic Division of the North Carolina Department of Agriculture (NCDA).


Why Waste Analysis?

Waste products must be used or disposed of with environmentally sound management practices in order to prevent damage to our natural resources. Farms' food-processing plants, textile manufacturers, pharmaceutical companies, wood and paper producers, and municipalities all generate a variety of waste products--the disposal of which must be managed somewhat differently depending upon the source and the intended use. Most waste must undergo some form of processing before it can be applied to the land.

As landfill space becomes increasingly limited, waste producers are being forced to seek alternative disposal sites or potential recycling opportunities. Land application is one of the safest and most common alternatives provided that best management practices (BMPs) are followed. Waste products are generally applied to the land because they contain nutrients or liming materials beneficial to plant growth. Waste analysis is the most accurate and efficient way to measure the nutrient or lime value of different waste products. Because the amount of these beneficial components can vary among waste products, laboratory analysis lets the producer know the proper amount of the waste material to apply to meet the specific plant needs for each site. When management decisions are made without waste-analysis information, even well-intentioned users can reduce plant growth and yields or endanger the environment.

Composting can reduce volume, improve uniformity, and sometimes alter the nutrient availability of waste products. Because of this, samples from the final material that will be applied must be analyzed.

Nutrient concentrations vary in most organic waste products. Table 1, for example, depicts the wide range in nutrients from animal wastes analyzed by the NCDA Agronomic Division. Note that the maximum and minimum values for nitrogen, phosphate, and potash differ by more than 100-fold. These numbers should send a clear message to waste users and environmental policymakers: average nutrient estimates are not adequate guides for the safe and efficient use of waste materials.

Table 1. Variations in poultry and swine manure nutrient levels.

  Minimum Maximum Average
Poultry, broiler house pounds per ton
Nitrogen 4 137 72
Phosphate 21 146 78
Potash 12 78 46
Swine, liquid lagoon pounds per 1,000 gallons
Nitrogen 2 345 136
Phosphate 1 197 53
Potash 5 369 133

Waste users who fail to test each waste material are faced with a number of questions they simply cannot answer. Are they supplying plants with adequate nutrients? Are they building up excess nutrients that may ultimately move to streams or groundwater? Are they changing the soil pH to levels that will not support plant production? Are they applying heavy metals at levels that may be toxic to plants and permanently alter soil productivity?

Because environmental damage and losses in plant yield and quality often happen before visible plant symptoms, growers and other users should always have their wastes analyzed by a competent laboratory and their application rates determined by a knowledgeable agronomist.


Waste Analysis Services

The Waste Advisory Section of the NCDA Agronomic Division analyzes wastes, interprets analytical results, and provides management recommendations for citizens of North Carolina. The fee is $4.00 per sample. Private laboratories also offer some of these services and their fees vary.

A good analytical service should always determine the concentrations of essential plant nutrients, including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and boron (B). Analyses of certain municipal and industrial wastes should also include tests for heavy metals like nickel (Ni), cadmium (Cd), and lead (Pb), as well as elements such as sodium (Na) and chlorine (Cl). The neutralizing value (calcium carbonate equivalent, CCE) of lime-stabilized products or materials suspected of having liming characteristics should also be determined.


Sampling Procedures

Proper sampling is the key to reliable waste analysis. Although laboratory procedures are extremely accurate, they have little value if the samples fail to represent the waste product. The importance of careful sampling becomes clear when one recognizes that laboratory determinations are made on a portion of the sample submitted that is as little as 0.02 pound (1 gram) for solid materials or less than a tablespoon (10 milliliters) for liquid materials.

Waste samples submitted to a laboratory should represent the average composition of the material that will be applied to the field. Reliable samples typically consist of material collected from a number of locations. Precise sampling methods vary according to the type of waste.

Ideally, growers should not base application rates on laboratory test results from previous years because nutrient concentrations can change significantly, particularly when the waste has been exposed to the environment. For example, nutrient levels in an anaerobic lagoon can be influenced by rainfall. Stockpiled litter or other wastes may also change significantly if left unprotected. Municipal and industrial wastes also vary as production demands alter inputs and processing.

Liquid Wastes

Liquid waste samples submitted for analysis should meet the following requirements.

  • Place sample in a sealed plastic container with about a one-quart volume. Glass is not suitable because it is breakable and may contain contaminants.
  • Leave 1 inch of air space in the plastic container to allow for expansion caused by the release of gas from the waste material.
  • Refrigerate samples that cannot be shipped on the day they are collected; this will minimize chemical reactions and pressure buildup from gases.

Ideally, some liquid wastes should be sampled after they are thoroughly mixed. Because this is sometimes impractical, samples can also be taken in accordance with the suggestions that follow.

Lagoon Liquid: Premixing the surface liquid in the lagoon is not needed, provided it is the only component that is being pumped. Growers with two-stage systems should draw samples from the lagoon they intend to pump.

Samples should be collected using a plastic container similar to the one shown in Figure 1. One pint of material should be taken from at least eight sites around the lagoon and then mixed in a plastic container. Waste should be collected at least 6 feet from the edge of the lagoon at a depth of about a foot. Shallower samples from anaerobic lagoons may be less representative than deep samples because oxygen transfer near the surface sometimes alters the ehemistry of the solution. Floating debris and scum should be avoided.

fig1.gif (85533 bytes)

Figure 1. Liquid waste sampling device.

One quart of mixed material should be sent to the laboratory. Galvanized containers should never be used for collection, mixing, or storage due to the risk of contamination from metals like zinc in the container.

Liquid Slurry: Waste materials applied as a slurry from a pit or storage basin should be mixed prior to sampling. Waste should be collected from approximately eight areas around the pit or basin and mixed thoroughly in a plastic container. Figure 2 shows a useful collecting device. An 8- to 10-foot section of 0.5- to 0.75-inch plastic pipe can also be used: the pipe should be extended into the pit, and the thumb pressed over the end to form an air lock; the pipe is then removed from the waste, and the air lock is released to deposit the waste in a container.

fig2.gif (91380 bytes) Figure 2. Slurry sampling device.

For analysis, the laboratory requires 1 quart of material in a plastic container. The sample should not be rinsed into the container because doing so dilutes the mixture and distorts nutrient evaluations. However, if water is typically added to the waste prior to land application, a proportionate quantity of water should be added to the sample.

Solid Wastes

Solid waste samples should represent the average moisture content of the waste.

A one-quart sample is required for analysis. Samples should be taken from approximately eight different areas in the waste, placed in a plastic container, and thoroughly mixed. Approximately one quart of the mixed sample should be placed in a plastic bag, sealed, and shipped directly to the laboratory. Samples stored for more than two days should be refrigerated. Figure 3 shows a device for sampling solid waste.

fig3.gif (89630 bytes)Figure 3. Solid waste sampling device.

Poultry In-House Manure Sampling: Nutrient concentration varies widely in poultry litter both from house to house and within each house. If waste is to be applied by house, each one should be sampled separately.

Waste samples should be collected from 6 to 12 locations in the house. Each sample should extend from the top to the bottom of the accumulated waste. Samples taken around waterers, feeders, and brooders should be proportionate to the space these areas occupy in the house. The collected material should be combined in a plastic container and mixed thoroughly. The 1 quart laboratory sample should be taken from this mixture.

Poultry Below-House Manure Sampling: In a high-rise system, manure is deposited below the poultry house. If the system is properly managed, the manure should be fairly uniform in moisture and appearance.

Approximately eight samples should be collected throughout the storage area. If manure in certain areas differs in appearance, take samples proportionate to the size and number of these areas. For example, if 10 percent of the manure differs from the bulk pile, then 10 percent of the total sample should be taken from this area. The collected material should be combined in a plastic container and mixed thoroughly. The 1-quart laboratory sample should be taken from this mixture, placed in a plastic bag, sealed, and shipped to the laboratory for analysis. If the sample can not be shipped within one day of sampling, it should be refrigerated.

Stockpiled Litter: Ideally, stockpiled waste should be stored under cover on an impervious surface. The weathered exterior of uncovered waste may not accurately represent the majority of the material. Rainfall generally moves water-soluble nutrients down into the pile. If an unprotected stockpile is used over an extended period, it should be sampled before each application.

Stockpiled waste should be sampled at a depth of at least 18 inches at six or more locations. The collected material should be combined in a plastic container and mixed thoroughly. The one-quart laboratory sample should be taken from this mixture, placed in a plastic bag, sealed, and shipped to the laboratory for analysis. If the sample cannot be shipped within two days of sampling, it should be refrigerated.

Surface-Scraped Waste: Surface-scraped and piled materials should be treated like stockpiled waste. Follow the same procedures for taking samples. Ideally, surface-scraped materials should be protected from the weather unless they are used immediately.

Composted Waste: Ideally, composted waste should be stored under cover on an impervious surface. Although nutrients are somewhat stabilized in these materials, some nutrients can leach out during rains. When composted waste is left unprotected, samples should be submitted to the laboratory each time the material is applied. Sampling procedures the same as those described for stockpiled waste.


Understanding the Waste Analysis Report

Samples submitted to the NCDA Agronomic Division will be analyzed and the sender will receive a report that lists the concentration of each plant nutrient and several potentially harmful elements. Specific concentrations of nutrients and other elements are reported on a dry-weight basis for solid wastes; results for liquid wastes are reported on a volume basis.

The most useful information is nutrients available for the first crop. These levels are predicted on an as-is or wet basis. Nutrient availability is predicted by estimating the nutrient release rate from the waste and a nutrient loss for a specific application method.

Nutrients listed in the report as "availab]e for the first crop" should be used in determining the actual application rate to meet a specific plant nutrient requirement. For the availability prediction to be reliable, growers must have properly identified the type of waste and the application method on the information sheet submitted to the laboratory.

For waste materials suspected of containing liming materials, such as stack dust or lime-stabilized waste, a calcium-carbonate equivalent (CCE) determination should be requested. These materials are reported on a dryweight basis for solid and semi-solid materials and on a volume basis for liquids. The CCE can be used to compare waste materials to agricultural lime for effectiveness in neutralizing soil acidity. The agricultural lime equivalent (ALE) is also calculated on a wet basis. This indicates the amount of the waste product that must be applied to have the same liming potential as one from agricultural lime with 90 percent CCE.


Monitoring and Record Keeping

Growers who use waste materials as fertilizer or a source of lime should maintain records of the analytical results, application rates, and soil tests for each application site. Growers are also advised to take plant samples to evaluate their nutrient management program, identify corrective actions for current crops, and plan improvements for future crops.

Owners of waste application sites may also wish to sample surface and groundwater supplies once a year to confirm that nutrient-management programs are not adversely affecting the environment. Where waste products have been applied regularly for a number of years, growers should also monitor the buildup of metals that can affect long-term soil productivity, particularly zinc and copper. For municipal and industrial waste sites, nickel, cadmium, lead, and sodium should also be monitored.