Manure lagoons, large outdoor basins designed to contain animal waste from concentrated animal feeding operations (CAFOs), serve as a method for managing substantial volumes of animal waste. These structures are typically unlined or lined with clay and hold a slurry of manure and water, where anaerobic respiration breaks down organic compounds. This article explores the various dangers associated with these structures, encompassing risks to air quality, water resources, soil health, and the potential for environmental incidents.
Airborne Hazards and Human Health
Manure lagoons continuously release a variety of gases into the atmosphere, posing risks to both air quality and human health. Among the most prevalent are hydrogen sulfide (H2S), methane (CH4), ammonia (NH3), and carbon dioxide (CO2). These gases are produced as organic matter in the manure undergoes anaerobic decomposition.
Hydrogen sulfide, identifiable by its rotten-egg smell at low concentrations, becomes highly dangerous at higher levels, quickly deadening the sense of smell. Concentrations as low as 10 parts per million (ppm) can cause eye irritation, while 500-700 ppm can be rapidly fatal, leading to respiratory paralysis and death. This gas is heavier than air and can accumulate in low-lying areas around lagoons, presenting a particular threat during manure agitation when levels can increase by hundreds or thousands of times.
Methane, an odorless and colorless gas, is a byproduct of anaerobic digestion and contributes to greenhouse gas emissions. While not directly toxic, methane is flammable and explosive when its concentration in air reaches 5% to 15%. This gas can accumulate at the surface of the lagoon, sometimes trapped in foam, and poses a significant explosion hazard, particularly during agitation or when disturbed. Carbon dioxide, also odorless and colorless, is another product of manure decomposition. It is heavier than air and can displace oxygen, leading to labored breathing, headaches, drowsiness, and eventually asphyxiation in high concentrations.
Ammonia, recognized by its sharp, pungent odor, irritates the eyes, nose, throat, and lungs. While its strong smell often provides a warning, prolonged exposure to high concentrations can cause severe lung damage or death. Ammonia emissions can travel significant distances, contributing to air pollution and potentially affecting ecosystems far from the source. These airborne compounds can lead to a range of health issues for workers and nearby residents, including respiratory problems, headaches, and in acute cases, neurological damage or fatality.
Water Contamination and Aquatic Life
Manure lagoons present a threat to water resources through various pathways, including runoff, leaching, and accidental spills. These events can contaminate both surface waters, such as rivers, lakes, and streams, and underground water sources. The primary pollutants released from lagoons are excessive nutrients like nitrates and phosphorus. When these nutrients enter waterways, they can trigger rapid growth of algae, a process known as eutrophication.
Algal blooms consume vast amounts of oxygen in the water as they decompose, creating “dead zones” where aquatic life, including fish, cannot survive due to oxygen depletion. This process leads to widespread fish kills and disrupts entire aquatic ecosystems. Beyond nutrients, manure lagoons also contain pathogens such as E. coli and Salmonella, which can contaminate drinking water supplies and make recreational activities unsafe.
Pharmaceuticals and antibiotics, administered to livestock, further complicate water contamination. These substances can leach into the environment, contributing to the development of antibiotic-resistant bacteria, which poses a broader public health concern. Faulty lagoon construction, poor maintenance, or extreme weather events like heavy rainfall can lead to overflows or breaches, releasing large volumes of contaminated waste directly into surrounding waters. Such incidents can have impacts on water quality and the health of aquatic populations.
Soil Degradation and Land Pollution
Manure lagoon operations can have long-term impacts on the health and quality of surrounding land. While manure can be a beneficial fertilizer, repeated or improper application of lagoon waste can alter soil chemistry. This includes changes to soil pH, which affects nutrient availability and the activity of beneficial microorganisms. The high concentrations of certain compounds in lagoon manure can disrupt the delicate balance of the soil ecosystem.
Animal feed additives can lead to the accumulation of heavy metals in the manure, which may then transfer to the soil during land application. These heavy metals can persist in the soil and potentially enter the food chain through crops or forage grown on the contaminated land. Such accumulation can reduce soil fertility and limit the types of crops that can be safely grown. The presence of large manure lagoons also creates significant odor issues for nearby properties, which can decrease land value and diminish the overall quality of life for residents in the vicinity.
Physical Dangers and Environmental Catastrophes
Manure lagoons pose acute physical dangers and the potential for large-scale environmental disasters. A significant and immediate risk is drowning, particularly for individuals who might fall into the deep, viscous liquid of the lagoons. The thick, often crusted surface of the manure can make escape difficult, increasing the risk of entrapment and submersion.
Beyond individual hazards, structural failures of lagoons, such as dike breaches or liner ruptures, can lead to massive, sudden spills of animal waste. These catastrophic events can release millions of gallons of manure, as seen in past incidents where spills have dwarfed major oil disasters in volume. The consequences of such spills are resulting in widespread pollution of rivers and lakes, destruction of aquatic ecosystems, and significant economic losses for affected communities due to clean-up costs and environmental damage. These incidents highlight the potential for environmental catastrophes that can arise from the failure of these large-scale waste containment systems.