Anaerobic Digester Covers

An anaerobic digester cover is a gas-tight impermeable geomembrane installed over a manure or wastewater lagoon to trap the biogas produced by anaerobic digestion. The cover floats on the lagoon surface and seals the headspace so methane can be collected rather than released, then piped to a flare or to an energy or RNG system. This is what turns an open lagoon into a covered lagoon digester. EFI is the most experienced covered lagoon digester contractor in the US, with 500+ systems installed.

Organic waste in the lagoon breaks down anaerobically and releases biogas, which is roughly 60 to 70 percent methane. A gas-tight EFI cover captures that biogas in the space between the cover and the liquid surface. A gas collection header and piping route the biogas to a flare for destruction or to an engine, boiler, or RNG upgrading system for energy. A liner below and a gas-tight cover above create a sealed digester from the existing lagoon.

Digester covers use gas-tight geomembranes, typically reinforced polypropylene (RPP) or HDPE, selected for methane impermeability, UV stability, and resistance to biogas and hydrogen sulfide. EFI fabricates covers in large panels at its own facility and field-welds them to the exact lagoon geometry with a sealed perimeter anchor trench.

Yes. EFI regularly retrofits gas-tight covers onto existing waste lagoons to convert them into digesters. The team designs the cover, gas collection, condensate management, ballast, and anchoring for the specific lagoon, so an operating lagoon can become a biogas-producing asset without building new infrastructure.

EFI cover systems include rainwater management on the surface and condensate drainage within the gas-collection path, so water does not pond on the cover or carry into the gas system. This protects biogas quality, maintains gas flow to the flare or energy equipment, and extends cover life.

Anaerobic digester covers are engineered for 15 to 25 years of service depending on material selection, climate, biogas chemistry, and maintenance. EFI uses UV-stabilized gas-tight materials and offers operations and maintenance support, including inspections and repairs, to help each cover reach its full design life.