Applying Non-Hazardous Wastes to Land: Opportunities and Problems
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Applying Non-Hazardous Wastes to Land: Opportunities and Problems

   

Applying Non-Hazardous Wastes to Land: Opportunities and Problems 1

Gerald Kidder2

In this fact sheet we will explore land application as a method of utilizing non-hazardous wastes or by-products. Many materials that are considered wastes are really resources that are in the wrong place or form. We will discuss the more common waste materials that have potential for land application and the benefits of using them. We will also look at precautions necessary for their use. The context will be utilization, not disposal.

The Issues

How does this concern me?

Human beings produce large quantities of wastes as we go about our daily lives. From our homes come wastes from food preparation, washing machines, baths, toilets, newspapers, junk mail, packaging, hobbies, auto and home maintenance projects, and the landscape. In addition, wastes are generated in producing the goods and services we utilize. So we contribute to the waste stream by buying food and manufactured products, utilizing facilities such as buildings and roads, and enjoying services such as electricity and softened water. In Florida, each person generates 9.6 pounds of municipal solid waste (MSW) per day, twice the national average. It adds up to 24.3 million tons per year. That does not include sewage sludge, treated wastewater, or indirectly produced wastes such as those from food production and preparation or from industrial processes.

Why the increased interest in disposal/utilization of wastes?

Previously used practices like open burning or dumping in streams, oceans, and pits in the ground are now severely restricted or prohibited. We are more aware of the environmental damage that occurs when wastes are burned, dumped into bodies of water, or buried in simple holes in the ground. Society's concern is reflected in laws and regulations affecting wastes. For several years now Florida law has required that any landfill receiving garbage must be lined. A similar federal law came into effect in 1995. Environmentally sound waste management is usually more expensive than simple burning, dumping, or burying, so changes in waste management can have significant economic impact on communities.

What are we doing about the waste problem?

Approaches being used to tackle this large and complex problem include:

Non-Hazardous Wastes and Soil

Where does land application of "non-hazardous wastes" fit in this picture?

Waste that does not adversely affect the soil and surrounding environment is considered a non-hazardous waste. Land application of such material is usually environmentally safer and more economical than other means of waste disposal. Also, spreading these materials on land dilutes the waste and allows the environment (soil, air, water, microbes, plants, and animals) to transform and assimilate the "waste" material. Nutrients and energy contained in the waste materials are often food for other living organisms.

Why would we want to apply wastes to land?

Soils can benefit chemically and physically from the addition of some wastes. At the same time, proper land application provides an environmentally safe and economical means of waste disposal/utilization. Many of our wastes had their origin in fields, orchards, forests, and urban landscapes. By returning such wastes to the soil from which they came, we complete the cycle that would have occurred naturally.

Most food and many fibers come from the land. Inevitable by-products are manure, food processing wastes, home and restaurant garbage, and sewage or septage sludge. Products made from natural fibers such as cotton, paper, and leather will result in mill residues, discarded clothes, junk mail, dirty paper towels, and shoes, to name a few. Soil is the natural place to return such materials, perhaps after some intermediate processing like composting. Plant materials (tree leaves, brush, grass) from home landscapes are best kept on-site and returned to the soil directly. However, if they are hauled off-site, they should also be returned to the soil after processing.

Finally, land application is economical. This is especially true when all costs and social benefits of alternate waste disposal options are considered.

Don't wastes pollute the soil?

Not if the materials are chosen carefully and applied properly. A waste in one situation can be a resource in another. Animal manures have been returned to the land as fertilizer and soil conditioner for centuries. Waste lime from water treatment plants and wood ash have an acid-neutralizing effect, just as aglime does. Yard wastes have much the same composition as crop residues -- which are considered an asset in good soil management.

What about heavy metal contamination of sewage sludges?

There is considerable misinformation about the magnitude of the heavy metal problem in today's biosolids. Industrial contamination, which was the main source of heavy metals in sewage sludge 20 to 30 years ago, has been greatly reduced. Individual sources of contamination have been identified, including small industries such as metal plating shops, labs, and manufacturing plants. These have been prohibited from flushing heavy metals into the sewer water, and contamination of municipal sewage sludges has been avoided. The new federal sludge rules further encourage such pre-cleaning of the waste stream.

When announcing the new National Sewage Sludge Rule in December 1992, EPA noted that approximately 70% of biosolids currently met the exceptional quality standards. The heavy metal and pathogen contents of exceptional quality sludge are low enough that EPA does not require regulation of its use.

What happens when wastes are land applied?

Soil is the home of a wide variety of living organisms capable of decomposing a whole host of materials. Some organisms, such as earthworms, sowbugs, and insect larvae, are readily visible. Microscopic organisms present in soil include bacteria, fungi, and actinomyces, each with a range of needs and capabilities that contribute to decomposition. Higher plants utilize nutrients released by the decomposition processes. What is waste to people is food for other organisms.

Materials, Application Methods, Rates, and Regulations

What waste materials can be applied to land?

All of the following can be applied to land -- provided the proper rates and precautions are used:

How are waste materials applied to land?

Solid waste materials are usually spread by specially equipped trucks or by tractor-drawn equipment. Liquid materials may be spread by similar equipment or may be pumped through pipes and applied by irrigation equipment. Injection of liquids below the soil surface is an excellent means of application that also controls odors but generally requires additional energy to pull the injection equipment through the soil.

Do Florida regulations control land spreading of waste materials?

Land spreading of many waste materials is regulated by the Florida Department of Environmental Protection. Septage disposal is regulated by the Department of Health and Rehabilitative Services. Federal regulations such as those found in the 1993 "sludge rule" (40 CFR Part 503) apply whenever Florida rules are less restrictive. Manure management where there are high concentrations of animals may be regulated by industrial waste permits or by agreements such as Soil Conservation Service conservation plans.

What are some of the precautions used when applying non-hazardous wastes to land?

Materials are categorized by their potential for containing pollutants or undesirable characteristics and handled accordingly. Application rates, based on crop nutrient requirements and soil characteristics, are designed to avoid nutrient excesses that potentially could damage plants or water bodies. Application is not allowed near streams, surface waters, or water wells, to minimize their contamination by nutrients or particulate matter from the waste material.

What are some typical application rates?

Application rates vary considerably because waste materials are variable in chemical composition and in the proportion of solids to water. Nitrogen (N) content is the characteristic most often used to determine the maximum application rate, but sometimes the content of other elements (e.g., P, Cd, Pb, Zn) is also considered. The following are representative per acre application rate ranges: 2 to 40 tons of manure, 20 to 80 tons of composted yard wastes, 20,000 to 80,000 gallons of septage or liquid sewage sludge, up to 150 inches of waste water effluent, and 0.5 to 2.0 tons of waste lime.

Summary and References

Summary

Application of non-hazardous wastes to land is an environmentally and economically sound waste management alternative. When it is done with reasonable care, plants benefit from return of nutrients and organic matter, soil physical properties are improved, and wastes are turned into resources. Regulations and common sense management practices protect soil and water from inappropriate materials and rates.

Some References

Fla. Dept. Environmental Protection. 1996. "Solid Waste Management in Florida, March 1996 Report". FDEP, Bureau of Solid & Hazardous Waste. Tallahassee, Fla.

Hoitink, H.A.J., and H.M. Keener (eds). 1993. The Science and Engineering of Composting: Design, Environmental, Microbiological and Utilization Aspects . Renaissance Publications. Worthington, Ohio.

USEPA. 1994. "A Plain English Guide to the EPA Part 503 Biosolids Rule". EPA/832/R-93/003. Office of Wastewater Mgt., Washington, DC.

Footnotes

1. This document is SL-137, one of a series of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published as Notes in Soil Science, SS-SOS-43, September 1993. Revised as SL-137, January 1998. Reviewed September 2003. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.

2. Gerald Kidder, professor emeritus, Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611-0290.

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.


Copyright Information

This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.