Biogas Tanks: Types, Materials, and Selection for AD Plants

A biogas tank stores organic feedstock and captured biogas in a corrosion-resistant shell rated for 30-50 years under acidic, methane-rich conditions. The most common form fuses vitreous enamel at 820-930°C for an inert interior. Engineered by Shijiazhuang Zhengzhong Technology Co., Ltd. (Center Enamel) to AWWA D103-09 and ISO 28765, these tanks serve farms, municipalities, and industry.

A biogas tank is a vessel that holds anaerobic digestion feedstock and the biogas it produces, operating at 35-38°C mesophilic temperature with 55-65% methane at 5-30 mbar. In Glass-Fused-to-Steel (GFS) form the interior carries enamel fused at 820-930°C to 0.25-0.40 mm, resisting the acidic slurry. Capacities run 500-50,000 m3 for a single digester.

• Temp: 35-38°C mesophilic.
• Gas: 55-65% methane, 5-30 mbar.
• Surface: 0.25-0.40 mm enamel.
• Range: 500-50,000 m3.

Biogas tanks come as CSTR digesters with mixers, as gas-tight storage with a double-membrane holder, or as covered lagoons. The shell carries a holiday-tested enamel or epoxy coat, and roofs range from fixed cones to aluminum geodesic domes. Common pairings are CSTR for slurry and UASB for high-strength wastewater, each engineered to the feed's pH and solids.

• CSTR: mixed digester.
• Holder: double membrane.
• Coat: enamel or epoxy.
• Roof: cone or dome.

They serve farms converting manure, food processors handling organic waste, and municipalities treating sludge. Because the interior resists pH 3-11 and 1-14 in special grades, the same tank family covers wet digestion and gas storage on one site. Mixing uses 5-15 W/m3 to keep solids suspended and gas yield stable.

• Farms: manure and residue.
• Municipal: sludge digestion.
• pH: 3-11, 1-14 special.
• Mix: 5-15 W/m3.

Sizing sets hydraulic retention at 20-40 days and temperature at 35-38°C, with biogas at 55-65% methane and 5-30 mbar. The shell is calculated to AWWA D103-09 and ISO 28765, plates blasted to Sa 2.5 and holiday-tested at 1500 V. The holder and seal are designed for the 5-30 mbar gas pressure without leakage.

• Retention: 20-40 days HRT.
• Temperature: 35-38°C.
• Gas: 55-65% methane.
• Pressure: 5-30 mbar.
• Mixing energy: 5-15 W/m3.
• Enamel DFT: 0.25-0.40 mm.
• Holiday test: 1500 V.
• Code basis: AWWA D103-09 / ISO 28765.
• Limitation to check: Feed pH below 5.5.

The inert enamel interior outlasts painted steel for 30-50 years and speeds erection through bolting. A genuine limitation is that GFS is not suited to feedstock below pH 5.5 unless a correction step is added; this boundary must be confirmed during process design, or the coating warranty is at risk in acidic feed.

• Advantage: inert, 30-50 years.
• Advantage: fast bolted build.
• Limitation: not for pH<5.5 as-is.
• Boundary: confirm pH in design.

The figures below are the load-bearing values a provider should quote per biogas tank; capacities reach 50,000 m3 and design life runs 30-50 years. They let an engineer confirm the shell, coating, and gas system before steel is ordered for an anaerobic duty.

Against welded steel, concrete, and fiberglass, a Glass-Fused-to-Steel (GFS) biogas tank wins on corrosion resistance and build speed for the 500-50,000 m3 range. Use the table to match the material to feed corrosivity, site logistics, and required life.

Specify the enamel DFT of 0.25-0.40 mm, the 1500 V holiday test, and the ISO 28765 calculation; require references from biogas duties of similar volume. Shijiazhuang Zhengzhong Technology Co., Ltd. (Center Enamel) issues drawings, NDE records, and inspection packages per tank.

• Ask for: ISO 28765 calculation.
• Verify: 1500 V test, 0.25-0.40 mm.
• Confirm: biogas reference.
• Package: drawings plus NDE.

A biogas tank is a coating system, a code calculation, and an inspection record built to last 30-50 years under acidic, gas-rich duty. Choose a provider who shows the enamel proof and the ISO 28765 math.

A vessel that stores anaerobic digestion feedstock and biogas, typically 500-50,000 m3, operating at 35-38°C with 55-65% methane.

Glass-Fused-to-Steel enamel resists the acidic slurry for 30-50 years; concrete and welded steel are alternatives for specific duties.

The bolted shell is designed to AWWA D103-09 and ISO 28765, with plant control under ISO 9001 and ISO 45001.

Plates are blasted to Sa 2.5, coated to 0.25-0.40 mm DFT, and holiday-tested at 1500 V per square meter.

Biogas is stored at 5-30 mbar, usually in a double-membrane holder on top of the digester.

Yes. Capacity, mixer, roof, holder, and coating grade are engineered per feedstock, with drawings issued per tank.

• Biogas tanks run 35-38°C with 55-65% methane at 5-30 mbar.
• GFS enamel resists acidic slurry for 30-50 years.
• Require ISO 28765 plus a 1500 V holiday test.
• Confirm feed pH during design, not after build.