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Reference
32 terms from lagoon cover, geomembrane liner, and biogas work, defined in plain language and linked to the page on this site that covers each one.
A drone survey of a gas-tight cover using a laser methane sensor and a thermal camera to find and map leaks. It covers the whole cover surface in a single flight and produces a report that tells the operator whether a cover needs a repair or a replacement.
Any sealed vessel or lagoon in which bacteria break down organic material without oxygen and produce biogas. Tank designs (complete mix, plug flow) are heated and mixed; covered lagoons are not. The choice depends on climate, manure consistency, and how the gas will be used.
The trench dug around the perimeter of a lined or covered lagoon into which the edge of the geomembrane is laid and backfilled. It is what keeps a liner or cover from pulling into the lagoon under wind, wave, or gas pressure.
A floating or suspended geomembrane wall placed inside a lagoon or tank to direct flow, extend the path water travels, and stop short-circuiting between inlet and outlet. Baffle curtains raise treatment time without adding volume and are used in wastewater lagoons, clearwells, and digesters.
The gas produced by anaerobic digestion, typically 55 to 70 percent methane with the balance mostly carbon dioxide, plus water vapor and trace hydrogen sulfide. Biogas can be flared, burned in a boiler or engine, or cleaned up and compressed or injected into a pipeline.
A gas-tight cover over an existing lagoon paired with an enclosed flare that destroys the captured methane. It is the lowest-complexity way to stop methane from a lagoon, because there is no gas cleanup, no engine, and no pipeline interconnect to build or maintain.
Burning biogas in an engine or turbine to produce electricity while recovering the engine's heat for the digester or the farm. In the EPA AgSTAR database it is one of the most common end uses alongside compressed natural gas, electricity, and pipeline injection.
Handling the water that drops out of warm, saturated biogas as it cools in the collection piping. Without traps and drains at every low point, condensate pools in the line, restricts flow, and starves the flare or engine of gas.
Weighted tubes or pipes laid on top of a floating cover in a pattern that holds the membrane down against wind and channels rainwater to pump-off points. On a gas-tight cover the ballast layout also shapes where gas collects, so it is designed alongside the collection system.
An earthen lagoon sealed with a gas-tight floating cover so the manure or wastewater in it digests without oxygen and the biogas collects under the cover. It is the simplest digester design, with no tank, no heating, and no mechanical mixing in most cases, which is why it is the most common type in the EPA AgSTAR database.
Cutting sample coupons out of finished field seams and pulling them apart in a tensile tester to confirm the weld is stronger than the parent sheet. Samples are taken at a set interval along the seam, and every test is logged as part of the installation QA record.
Removing a worn-out gas-tight cover and installing a new one on a lagoon that stays in service. Membrane covers last roughly 15 to 25 years depending on material and exposure, and a replacement can be sequenced so the lagoon is never drained.
A survey that finds holes in an installed geomembrane by putting a voltage across the liner and looking for the current path that only a hole can provide. It catches punctures that visual inspection and seam tests miss, and is run after the liner is covered or filled.
A flare that burns biogas inside an insulated stack rather than in an open flame, holding the combustion temperature and residence time needed to destroy methane at a verifiable rate. Enclosed flares are the type specified for carbon credit and compliance projects because their destruction efficiency can be measured.
A geomembrane sheet that rests on the surface of a lagoon or pond, held in place by ballast and an anchor trench around the perimeter. Floating covers control odor, keep rain and sunlight off the liquid, and, when built gas-tight, collect biogas. They are the cover type EFI installs most often.
The two methods used to join geomembrane panels in the field. Fusion welding runs a heated wedge between overlapping sheets to bond them in a double track with a test channel; extrusion welding lays a bead of molten polymer over a seam and is used for patches, details, and repairs.
The piping, headers, and blower that draw biogas from under a cover and deliver it to a flare or end use. On a covered lagoon the collection points sit at the high spots of the cover, with condensate drains at the low spots so water does not block the line.
A floating cover with welded seams and sealed penetrations so that gas produced under it cannot escape. A gas-tight cover is what turns an open manure or wastewater lagoon into a covered lagoon digester, because the biogas has nowhere to go but the collection piping.
A manufactured sheet of low-permeability plastic used as a liner or cover to keep liquids and gases where they belong. HDPE, LLDPE, and reinforced polypropylene are the three geomembranes EFI installs most, each chosen for a different mix of chemical resistance, flexibility, and exposure.
A thin layer of bentonite clay held between two geotextiles, which swells when wet to form a low-permeability barrier. A GCL is often used under a geomembrane as the second layer of a composite liner, or in place of a thick compacted clay layer where soil or space is limited.
A corrosive, toxic gas produced during digestion, present in raw biogas at anywhere from a few hundred to several thousand parts per million. It attacks engines, boilers, and piping, so almost every biogas end use has an H2S limit that must be met before the gas is burned or upgraded.
The stiffest and most chemically resistant common geomembrane, used for lagoon liners, landfill liners, and containment where the sheet will see harsh liquids or long UV exposure. It is welded by fusion and extrusion methods and specified by thickness, most often 40 to 80 mil.
Metering a small amount of air or oxygen into the biogas headspace under a digester cover, where naturally present bacteria convert hydrogen sulfide to elemental sulfur. The oxygen goes into the gas space above the liquid, never into the water column, so digestion is not disturbed and methane production continues.
A lined pad on which crushed ore is stacked and irrigated with a solution that dissolves the target metal. The geomembrane under the heap collects the pregnant solution and keeps it out of the ground, so it is built to carry very high loads over a long service life.
California's program that assigns a carbon intensity score to transportation fuels and issues tradeable credits to fuels below the annual target. Dairy and swine biogas used as vehicle fuel qualifies for a pathway, which is why the EPA database flags which projects hold one.
A more flexible polyethylene geomembrane than HDPE, better at conforming to uneven subgrades and tolerating settlement, at the cost of some chemical and UV resistance. It is a common choice for floating covers and for liners over soft or irregular ground.
Burning captured methane so it leaves the stack as carbon dioxide and water instead of escaping to the atmosphere as methane, which traps far more heat per ton. Destruction is the minimum that a cover and flare accomplish; energy recovery is optional on top of it.
A carbon credit issued for methane that was captured and destroyed rather than emitted, verified against a registry protocol and the flare's measured destruction rate. It is the revenue stream behind cap-and-flare projects that do not sell gas or power.
A floating cover made from a material that lets gas pass through while still blocking sunlight and rain and holding down odor. Permeable covers are used where the goal is odor, algae, or evaporation control rather than gas capture, and they are the simpler of the two systems to build.
A flexible geomembrane with a woven scrim laminated between polypropylene layers, giving it high tear strength and good UV life in a lightweight sheet. rPP is widely used for exposed floating covers and tank liners where the material has to flex daily without cracking.
Biogas that has been cleaned of carbon dioxide, hydrogen sulfide, water, and other contaminants until it meets pipeline gas quality. Producing RNG requires upgrading equipment and a pipeline or fueling connection on top of the digester itself, which is why many farm projects stop at destruction or on-site power.
A lined area or berm around a tank, sump, or process area that catches a leak or spill before it reaches soil or groundwater. Regulations set the required capacity and materials, and the liner must resist whatever the primary vessel holds.
If a term you need is missing, ask and it goes on the list. For the data behind the digester terms, see the US Livestock Digester Atlas.
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