Land Farming is a bioremediation technology. Contaminated soils are mixed with soil amendments such as soil bulking agents and nutrients, and then they are tilled into the earth. The material is periodically tilled for aeration. Contaminants are degraded, transformed, and immobilized by microbiological processes and by oxidation. Soil conditions are controlled to optimize the rate of contaminant degradation. Moisture content, frequency of aeration, and pH are all conditions that may be controlled. Land Farming differs from composting because it actually incorporates contaminated soil into soil that is uncontaminated. Composting also generally takes place in aboveground piles.
Limitations and Concerns
A land farm must be managed properly to prevent both on-site and off-site problems with ground water, surface water, air, and food chain contamination. Runoff collection facilities must be constructed and monitored. The possible leaching of contaminants from the contaminated soil into the ground and groundwater is a major concern.
Land Farming incorporates contaminated soil into soil that is uncontaminated, creating a larger volume of contaminated material. Therefore, the rate at which contaminants are degraded must be balanced with the potential of creating a larger body of contamination.
Land farms must not be used to dilute contaminants. If it cannot be shown that biodegradation occurs for all contaminants of concern, land farming should not be used.
Conditions affecting biological degradation of contaminants (e.g., temperature, and rainfall) are largely uncontrolled, possibly increasing the time to complete remediation.
Inorganic contaminants will not be biodegraded, but they may be immobilized.
Dust control is an important consideration, especially during tilling operations.
Many waste constituents may be banned by regulation from being applied to soil.
The depth of treatment is limited to the depth of achievable tilling (normally 18 inches).
A large amount of space is required.
Land farming has been proven most successful in treating petroleum hydrocarbons and other less volatile, biodegradable contaminants. The more chlorinated or nitrated the compound, the more difficult it is to degrade. Many mixed products and wastes include some volatile components that transfer to the atmosphere before they can be degraded. Contaminants that have been successfully treated include diesel fuel, No. 2 and No. 6 fuel oils, JP-5 jet fuel, oily sludge, wood-preserving wastes such as pentachlorophenol (PCP), polynuclear aromatic hydrocarbons (PAHs), and creosote), and certain pesticides.
Technology Development Status
Numerous full-scale operations have been conducted, particularly for sludges produced by the petroleum industry. Land farming is considered a commercial technology.
Other Resources and Demonstrations
None have been identified.