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Silage Leachate Pollution

Silage runoff, or the flow of surface excess water over an area containing silage or silage leachate, contains nutrients harmful to watersheds. Nutrient concentrations within silage runoff are variable and are dependent on event size, seasonality, bunker condition, and concentration of silage.

Silage leachate is an issue for all farmers who have silage. Silage leachate can come from all forms of silage storage: bunkers, upright silos, bags, and piles. Handling leachate can be simple or complex depending on the scope of your operation. Silage can be made from corn, and silage crops, and also grain or alfalfa. Also, canning company wastes, such as from sweet corn processing may be used. The amount of leachate produced varies with the material stored, its moisture and nitro-gen content, and handling and storage conditions. Of these, moistur e is the most critical.

Silage leachate is an organic liquid that is formed when water, or in some cases pressure from the structure, comes in contact with silage and runs off. Leachate can be formed as a part of silage storage, especially if the corn or alfalfa is harvested too wet. Water comes in contact with the silage because it is part of the silage. The other source of leachate is rain water coming in contact with silage and carrying nutrients with it.

Groundwater contaminated with silage juices has a disagreeable odor and normally shows increased acidity, ammonia, nitrate, and iron.

Silage leachate has a high biological oxygen demand, BOD. If it is allowed to reach surface water, oxygen in the water will be consumed so quickly that anything living in the water, including fish, could immediately be in peril. It is estimated that one gallon of silage leachate can lower the oxygen content of 10,000 gallons of river water to such an extent that there is a chance for fish kill. Leachate also can cause algal blooms that will further deplete the oxygen levels of surface water and it can also produce high levels of ammonia which will also cause fish kill.

Silage leachate is acidic (pH around 4), and contains high concentrations of BOD, ammonia-N, phosphorus, potassium, and organic carbons. Silage leachate is one of the most environmentally contaminating wastes produced on a livestock farm if it’s not contained, treated, and disposed of properly. The direct discharge to vegetated areas kills the vegetation and causes septic odors. Silage leachate is corrosive to steel and concrete, which further complicates managing this waste.

Feed storage is required for the majority of dairy operations in the country (which are expanding in size and fed storage requirements) leading to widespread potential contamination. Collecting first flush data provides essential data for separation of waste streams (high and low strength) to ease management in terms of operation and cost, reduce loading to treatment systems, and reducing the overall environmental impact.

The risk of widespread groundwater contamination due to silage storage is relatively low, but contamination can occur if silage leachate (silage juices) enter a well or seeps through the soil to shallow groundwater. Surface water can also easily be contaminated by leachate runoff from a leaking silo or a ground storage bag. The operator should reduce these risks by managing silage moisture content and maintaining a structurallly sound storage structure.

Silage seepage presents two concerns for the agricultural industry namely that pollution of land and water may result from silage seepage, and the silage juices cause corrosion and deterioration of the silo.

Most of the environmental problems associated with silage/haylage seepage on farms result from improper or inadequate collection and retention of the seepage draining from the silos. An adequate collection and storage/treatment system is essential.

Silage is an indispensible feed for animal-based agriculture. When properly harvested and stored, silage poses little or no pollution threat. Improper handling and inclement weather, however, can lead to a significant flow of silage juices (or leachate) from the silo. Leachate is an organic liquid that results from pressure in the silo, from putting up feed that is too wet, or from extra water entering the silo. It is usually a problem only when silage is fresh or just after it is stored in covered silos. Storage in uncovered silos is not recommended, because exposure to the weather accelerates the decrease of silage quality. Loss of leachate represents a major loss of nutrient value from the silage.

If silage leachate enters a stream, its high organic content feeds bacteria that rob the water of oxygen. The capacity of a contaminant to rob water of oxygen is called biochemical oxygen demand (BOD). The BOD of silage effluent is 150 times greater than that of human sewage. BOD from 1 ton of silage with a moisture content of 23.4% has been described by others to be equal to approximately 4,755 gallons of sewage.


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