A manure lagoon is a large, open-air earthen basin designed to store and biologically treat animal waste, primarily from Concentrated Animal Feeding Operations (CAFOs). This system handles the immense volume of liquid manure created by industrial-scale livestock farming, often holding millions of gallons of waste. The primary function of the lagoon is to allow the organic matter to undergo anaerobic digestion, where microorganisms break down the waste in the absence of oxygen. This digestion partially stabilizes the manure, reducing its volume and preparing the effluent for eventual application to agricultural fields.
Contamination of Water Systems
Manure lagoons present a significant threat to surrounding water bodies through the release of excess nutrients and various pathogens. The high concentrations of nitrogen and phosphorus in the stored waste are a major concern for both surface water and groundwater quality. These nutrients can leach through unlined or poorly maintained lagoon bases, or run off the surface during heavy rainfall events, eventually entering rivers and streams.
Once these pollutants reach surface water, they fuel a process known as eutrophication, causing excessive growth of aquatic plants and algae. The resulting dense algal blooms eventually die and decompose, a process that consumes vast amounts of dissolved oxygen from the water. This oxygen depletion creates “dead zones” where fish and other aquatic life cannot survive, leading to large-scale die-offs.
The nitrogen component of the waste also poses a risk to groundwater, which is a common source of drinking water for nearby communities. Specifically, nitrates can contaminate the water supply, a particular danger to human health. In infants under six months old, consuming water with nitrate levels above the safe threshold of 10 parts per million can lead to methemoglobinemia, a serious condition that impairs the blood’s ability to carry oxygen.
Furthermore, lagoons serve as a reservoir for numerous disease-causing microorganisms shed by livestock. Pathogens like E. coli, Salmonella, and Cryptosporidium can be transmitted to humans through contaminated drinking or recreational water. Their release into the environment, especially via spills or overflow, poses a direct public health hazard. The presence of antibiotics used in livestock operations also means that lagoons can be a source of antibiotic-resistant bacteria, which may transfer to water sources and potentially affect human populations.
Hazards from Atmospheric Emissions
The anaerobic decomposition occurring within the manure lagoon constantly generates a cocktail of gases that are released into the atmosphere, creating air quality and climate concerns.
Toxic Gases
Among the emissions is Hydrogen Sulfide (H₂S), a colorless gas with a distinct rotten-egg odor at low concentrations. Chronic, low-level exposure to H₂S can cause respiratory problems, headaches, and neurological issues for workers and residents in close proximity to the facility. Another compound released is Ammonia (NH₃), a severe respiratory irritant formed from the breakdown of nitrogen-rich components. Ammonia can travel hundreds of miles, contributing to the acidification and eutrophication of distant ecosystems. The persistent, strong odors from these and other volatile organic compounds significantly reduce the quality of life for those living near the lagoons.
Greenhouse Gases
Methane (CH₄) is a significant byproduct of the anaerobic digestion process. While not directly toxic to humans at low levels, methane is an extremely potent greenhouse gas, contributing substantially to global climate change. These atmospheric emissions are continuous, distinguishing them from the episodic risks of water contamination.
Immediate Physical Safety Concerns
Beyond chronic environmental hazards, manure lagoons pose acute physical dangers that can result in sudden injury or death.
Toxic Gas Exposure
The most perilous threat is the rapid, lethal buildup of toxic gases, especially Hydrogen Sulfide (H₂S), which occurs during agitation or pumping of the liquid waste. At concentrations above 100 parts per million, H₂S rapidly paralyzes the sense of smell, eliminating the rotten-egg warning. Concentrations of 700 parts per million can be instantly fatal, causing loss of consciousness and death within minutes.
Physical Hazards
A deceptive surface crust often forms on the lagoon, making the area appear solid and masking the liquid waste underneath. This crust creates a significant physical hazard, as a person or animal could easily break through and be unable to escape. Drowning is a serious risk, compounded by the viscosity of the slurry and the immediate presence of toxic gases at the surface.
Structural Failure
Structural failure represents a massive and sudden danger to the surrounding environment and infrastructure. Catastrophic breaches of the earthen walls or liners, often caused by poor construction or extreme weather events, can occur with little warning. When a breach happens, millions of gallons of untreated, toxic waste are instantly released, flooding nearby land, waterways, and properties in a devastating, uncontrolled spill.