EFI USA anaerobic digester cover on a covered lagoon

Biogas Capture

Anaerobic Digester Covers

Gas-tight covers, gas collection and drainage for anaerobic lagoons. Define the cover scope and its connection to the rest of the biogas system.

Why a Gas-Tight Cover

Plan the Cover and Gas Path Together

A cover contains the biogas produced by the treatment process. Its perimeter, piping and drainage need to work with the basin and downstream equipment. Coordinate the liner below with the cover above. See the biogas and digester program.

Captures Methane

A gas-tight seal traps biogas in the headspace instead of letting methane escape, so it can be destroyed or used for energy.

Controls Odor

Sealing the lagoon surface contains the odor compounds that drive neighbor complaints and permit pressure.

Connects to Gas Handling

Define the tie-in to the selected flare, engine, boiler or upgrading equipment, including its flow and pressure requirements.

Retrofits Existing Lagoons

Assess existing lagoon geometry, anchoring, operating levels and construction access before defining a retrofit.

System

Digester Cover System Components

The membrane, anchoring, ballast, drainage and gas piping form a coordinated scope. Engineering details are on the anaerobic cover specifications page.

Component	Function
Gas-tight membrane	Impermeable RPP or HDPE cover that seals the lagoon and traps biogas
Gas collection header	Piping network that draws biogas from the headspace to the flare or energy system
Condensate management	Drains moisture out of the gas path to protect gas quality and flow
Rainwater & ballast system	Sheds surface water and tensions the cover against wind and gas pressure
Perimeter anchor trench	Seals the cover edge to the bank for a gas-tight perimeter

EFI anaerobic digester cover installation

Where Digester Covers Work

Proven Across Agriculture and Industry

Dairy & Livestock

Manure lagoon digesters for dairy and cattle operations capturing biogas from waste streams.

Swine Operations

Gas-tight covers on swine waste lagoons for methane capture and odor control.

Food & Beverage Processing

Industrial wastewater lagoons converted to digesters that capture biogas from high-strength effluent.

Municipal Wastewater

Covers on treatment lagoons to capture biogas and contain odor near populated areas.

Pair the cover with EFI O2 injection and H2S removal to clean the biogas for energy use, or route the gas to an enclosed flare under the cap and flare program. For an aging installation, see digester cover replacement.

Digester cover scope in dairy and industrial projects

These original EFI case histories describe completed cover and gas-system work. They help define interfaces for a new project without predicting its gas output.

Castelanelli Bros. Dairy, California, 2004

EFI fabricated and installed the cover and biogas collection system at the Lodi dairy. The original case history specifies a 60 mil HDPE cover, ballast weights and gas collection beneath the cover. RCM International is named as engineer.

Include ballast and gas collection in the scope review alongside the membrane. Agree on the handoff to the process designer and energy equipment supplier.

Read the Castelanelli cover history

Olmeca III, Guatemala, 2009

EFI fabricated and installed covers and a biogas system for two digesters at Grupo Hame’s palm oil mill. The source specifies 60 and 80 mil HDPE, with collected biogas routed to generators and excess gas to a flare.

Identify both the intended gas use and the excess-gas destination. The original project scope does not assign generator supply or the entire process design to EFI.

Read the Olmeca III project history

Define the cover package before requesting a quote

Send the lagoon plan, slopes, liner details, operating-level range and available anchoring area.
Provide the waste stream, process design basis and available gas-flow and gas-quality data; identify any values still being developed.
Name the downstream equipment and proposed connection point, along with flow, pressure and control requirements supplied by its designer.
Assign responsibility for rainwater removal, condensate, electrical supply, access, commissioning and operator training.

Request a digester cover scope review

Independent record of EFI’s cover role

Environmental Credit Corp.’s 2011 final report to USDA NRCS identifies EFI as the contractor hired to engineer, design and construct lagoon covers and gas collection systems at its North Carolina and New York project sites. This developer record documents the historical scope; each new project needs its own process and equipment design.

Review the scope headings in EFI’s reference cover and biogas specification with the project engineer. Equipment quantities and acceptance criteria must be set for your installation.

FAQ

Frequently Asked Questions

A digester cover is a gas-tight membrane over an anaerobic treatment basin. With a sealed perimeter and collection piping, it contains the biogas produced below it and routes that gas to the specified handling equipment. The cover is one part of the digester process.

Anaerobic treatment produces biogas beneath the cover. Collection piping routes it toward a flare or energy-use equipment. Waste characteristics, loading, retention time and temperature affect digestion; fitting a cover alone does not establish gas production or energy output.

Material is selected for the site and process. EFI’s historical Castelanelli installation used a 60 mil HDPE cover, while Olmeca III used 60 and 80 mil HDPE. A new design must address chemical exposure, weather, seams, anchoring and operating conditions rather than copy a historical thickness.

An existing lagoon can be assessed for a cover retrofit. The review needs basin geometry, liner condition, anchoring space, operating levels and a construction sequence. Gas collection, drainage and downstream equipment interfaces must be included in the proposed scope.

Surface drainage and gas-line condensate handling are separate design tasks. Define the collection points, removal equipment, discharge route and operator access for each. The site operating manual should set the inspection and maintenance procedures.

Service life depends on material, exposure, chemistry, operating conditions and maintenance. Review product data, design limits and the warranty for the proposed cover. Inspection of an existing cover is needed before deciding between repair and replacement.

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