What Is an Anaerobic Lagoon?

An anaerobic lagoon is a large, man-made earthen basin designed to treat and store livestock waste, especially manure from cattle, swine, and poultry operations. These lagoons rely on anaerobic digestion, a biological process where microorganisms break down organic material in the absence of oxygen.

This method is commonly used on concentrated animal feeding operations (CAFOs), where the volume of animal waste is too large for conventional storage or treatment. Anaerobic lagoons can retain wastewater for 20 to 150 days, allowing solid and liquid separation, pathogen reduction, and biogas production, primarily methane (CH₄) and carbon dioxide (CO₂).

How Anaerobic Lagoons Work

Anaerobic lagoons operate like a large-scale septic system. Here’s what happens inside:

• Wastewater enters the lagoon from barns or collection pits.

• Heavy solids settle to the bottom, forming sludge.

• Anaerobic bacteria in the sludge digest the organic matter, releasing gases like methane, ammonia, and hydrogen sulfide (H₂S).

• The upper liquid layer allows further treatment and eventual evaporation or discharge.

Lagoons are typically 8 to 15 feet deep to prevent oxygen penetration, which preserves the anaerobic conditions required for methane-producing microbes.

Environmental Challenges

Anaerobic lagoons offer a low-cost solution to waste management, but they come with serious environmental risks if poorly designed or maintained:

➤ Air Emissions

• Gases like methane, ammonia, and H₂S contribute to air pollution and pose health hazards to nearby communities.

➤ Groundwater Contamination

• Without proper liners, nitrate, phosphorus, pathogens, and antibiotics can leach into surrounding soil and water sources.

➤ Overflow & Runoff

• Heavy rainfall, wind, or inadequate capacity can lead to overflows, spreading bacteria, hormones, and other contaminants into the environment.

Anaerobic Lagoon vs Anaerobic Digester

An anaerobic digester is often more controlled, compact, and efficient, especially where biogas energy capture is a priority. However, lagoons are still widely used due to their lower installation cost and ability to handle large volumes.

Covered Anaerobic Lagoons

One of the most effective upgrades to a lagoon system is the addition of a floating cover.

Floating covers help:

• Trap odors like H₂S and ammonia

• Capture methane for energy use

• Prevent rainwater infiltration and overflow

• Meet EPA air emission standards

• Improve safety for nearby workers and communities

A properly designed cover can transform a simple lagoon into a biogas-producing asset while also improving environmental compliance.

Lagoon Liners & Leak Prevention

To prevent groundwater contamination, anaerobic lagoons should be lined with impermeable materials, such as:

• Reinforced Polypropylene (RPP)

• High-Density Polyethylene (HDPE)

• Geosynthetic Clay Liners (GCL)

These materials offer high chemical resistance, weld strength, and puncture resistance, especially when paired with proper anchoring systems.

Plastic Fusion Fabricators provides custom-fabricated liners tailored to lagoon dimensions, slope angles, and pipe penetrations.

Should You Cover Your Lagoon?

✔️ You should consider covering your lagoon if:

• You’re dealing with strong odor complaints

• You’re losing valuable biogas to the atmosphere

• You want to meet evolving Clean Water Act or state-level air quality regulations

• You’re applying for renewable energy incentives

Floating covers are scalable, cost-effective, and compatible with most existing lagoons.

Frequently Asked Questions about Anaerobic Lagoons

What is the difference between anaerobic and aerobic lagoons?

Anaerobic lagoons function without oxygen and produce methane. Aerobic lagoons, on the other hand, rely on oxygen (natural or mechanical) to break down waste and produce less gas.

What gases are produced in anaerobic lagoons?

The digestion process produces methane (CH₄), carbon dioxide (CO₂), ammonia (NH₃), and hydrogen sulfide (H₂S) — some of which are potent greenhouse gases or health hazards.

Are anaerobic lagoons legal?

Yes, but they are regulated by federal and state environmental agencies under the Clean Water Act, NRCS Technical Guidelines, and local permitting systems. Proper design, lining, and maintenance are required.

How do you maintain an anaerobic lagoon?

• Regular sludge monitoring and removal

• Inspecting for leaks, liner damage, or overflow

• Managing input flow rates

• Adding a floating cover for better gas control

Ready to Upgrade Your Lagoon?

At Plastic Fusion Fabricators, we specialize in engineered liner systems and floating covers for anaerobic lagoons used in agriculture, food processing, and industrial wastewater.

📩 Request a free project consultation →

Or explore our odor control covers designed to meet your regulatory and operational needs.

Sources & Further Reading

• EPA CAFO Regulations