Blowers for Renewable Natural Gas (RNG): Selection Guide for Engineers and Procurement Teams

Renewable Natural Gas — better known as RNG — has moved rapidly from niche energy concept to mainstream infrastructure investment. In the United States alone, operating RNG projects now number in the hundreds, with hundreds more under development. Behind every one of those projects, moving gas from point of production to point of use, is a blower system.

Selecting the right blower for an RNG application is not a standard procurement decision. It involves explosion-proof safety certifications, corrosion-resistant materials, gas-tight sealing, and performance parameters that differ significantly from conventional air blowers.

This guide is written for engineers, project developers, and procurement professionals who need to specify blowers for RNG service. It covers the role blowers play across the RNG process chain, the key technical requirements that separate RNG blowers from general-purpose equipment, and a comparison of the blower technologies best suited to each stage of the process.

TMC Fluid Systems supplies turnkey biogas and RNG blower systems to municipal, agricultural, and industrial customers across North America. This article draws on our direct application experience.

What Is Renewable Natural Gas and Why Does It Require Specialized Blowers?

Renewable Natural Gas is biomethane that has been captured, conditioned, and upgraded to pipeline-quality standards — typically 95% or greater methane (CH₄) content. Unlike fossil natural gas, RNG is produced from organic sources including:

• Agricultural manure and livestock waste at dairy and swine operations
• Municipal wastewater biosolids in anaerobic digesters at treatment plants
• Food and organic waste at food processing facilities
• Landfill gas captured from decomposing municipal solid waste

In each of these settings, the raw gas — whether it originates from a covered lagoon, a hard-walled digester, or a network of landfill wellheads — contains a complex mixture of methane, carbon dioxide (CO₂), hydrogen sulfide (H₂S), moisture, siloxanes, and trace contaminants.

Before it can be injected into a natural gas pipeline or used as compressed vehicle fuel, it must be collected, transferred through conditioning and upgrading equipment, and delivered at the pressure required by the downstream system.

Where Blowers Fit in the RNG Process Chain

A complete RNG system is not a single piece of equipment — it is a process chain, and blowers appear at multiple points along that chain. Understanding which duty each blower performs is essential for correct sizing and technology selection.

Stage 1 — Digester or Wellhead Gas Collection

At the source — whether an anaerobic digester or a landfill wellfield — gas is generated at very low positive pressure, typically between 2 and 24 inches water column ("WC), and must be drawn to a central collection header. At this stage, the blower operates under low-pressure differential conditions and must be capable of handling wet, dirty gas without clogging. See our detailed overview of biogas conveyance and compression fundamentals for a technical breakdown of this first stage.

Stage 2 — Transfer to Conditioning Equipment

Between the collection header and the conditioning skid (typically a dehydration unit and H₂S removal system), a transfer blower maintains steady gas flow and equalized pressure. Variable gas production rates — which are common in agricultural and landfill settings — require the blower to respond dynamically, often via a variable frequency drive (VFD).

Stage 3 — Within Conditioning and Upgrading Subsystems

Inside the conditioning train, blowers are used to circulate gas through scrubber vessels, drive gas across membranes or pressure swing adsorption (PSA) beds, and handle recirculation loops. This is where the chemical environment is most aggressive: concentrated H₂S, moisture, and CO₂ place extreme demands on materials and seals.

Stage 4 — Pre-Compression Boost

Before pipeline injection or storage, upgraded biomethane must be delivered at pressures that blowers alone cannot achieve - compressors take over at this stage. However, in applications where the upgraded gas must be moved at moderate pressure differentials (2–15 psi) to the compression inlet, a sliding vane compressor or high-pressure positive displacement blower is an efficient bridge technology. For a detailed comparison of when to specify a blower versus a compressor for RNG service, see our article on blowers vs. compressors.

Key Technical Requirements for RNG Blowers

The following requirements apply universally to any blower specified for RNG or biogas service. Failure to meet any one of them creates either a safety hazard or a maintenance problem that compromises plant uptime.

Explosion-Proof Design (Class 1, Division 1 or Division 2)

The National Electrical Code (NEC) classifies locations where flammable gases are present. Most RNG collection and conditioning environments qualify as Class 1, Division 1 (C1D1) — areas where flammable gases exist in ignitable concentrations under normal operating conditions — or Class 1, Division 2 (C1D2) — areas where flammable gases are handled in closed systems but could escape during abnormal conditions, requiring non-incendive, sealed, or specialized equipment.

Blower motors and electrical components must be rated for the applicable classification. TMC's biogas and specialty gas blowers are supplied with explosion-proof motors rated for Class 1, Division 1, Group D — the safest standard in the category.

Gas-Tight Sealing

Any leakage of methane to atmosphere is both a safety hazard and an environmental liability. RNG blowers must use mechanical seals or labyrinth-type seals that prevent gas migration into the motor or bearing cavity. Blowers relying on standard lip seals are inadequate for closed-loop methane service. Special sealing arrangements — including double mechanical seals with inert purge — are often specified for the highest-risk duty points.

Material Compatibility with H₂S and Moisture

Hydrogen sulfide is corrosive and, in concentrations above 10 ppm, toxic. Biogas and raw landfill gas can contain H₂S in concentrations from several hundred to several thousand ppm before conditioning. Blower casings, rotors, and internal components must be fabricated from corrosion-resistant alloys or given appropriate surface treatment. Bearing housings and timing gear cases must be sealed against moisture ingress, which accelerates H₂S attack on standard steel components.

Oil-Free Gas Delivery

Downstream conditioning equipment — particularly membranes, molecular sieves, and catalytic systems — is damaged by lubricant contamination. RNG blowers must provide 100% oil-free gas delivery. This requirement rules out any blower design that relies on oil flooding of the gas stream as a sealing or cooling mechanism.

Inlet and Discharge Protection

A vacuum switch at the blower inlet is standard practice: if biogas generation falls below the blower's minimum pumping speed, the switch trips the unit before a suction vacuum can damage downstream equipment or draw air into the gas stream, creating an explosive mixture. A pressure switch on the discharge line protects against excessive backpressure that could stall or damage the machine.

Which Blower Technology Is Right for Your RNG Application?

No single blower technology fits every stage of the RNG process chain. The right selection depends on flow rate, pressure differential, gas composition, and duty cycle. Below is a practical comparison of the technologies TMC Fluid Systems supplies for RNG service.

Positive Displacement (Roots-Type) Blowers — Twin Lobe and Tri-Lobe

Positive displacement blowers — also known as Roots-type, PD, or lobe blowers — deliver a fixed volume of gas per revolution, making them highly predictable and easy to control. They excel at the moderate flow rates and pressure differentials typical of digester gas collection and transfer duties (up to approximately 10 psi differential).

TMC supplies both twin lobe blowers and tri-lobe blowers for RNG and biogas service. Tri-lobe designs offer smoother, lower-pulsation flow compared to twin-lobe units — a significant advantage when feeding sensitive downstream conditioning equipment.

Regenerative (Side-Channel) Blowers

Regenerative blowers use a non-contacting impeller design that eliminates the metal-to-metal contact risk that creates sparking in some PD designs. They offer compact footprint, low maintenance, and quiet operation, making them well-suited for small-scale agricultural digesters and distributed RNG production facilities. Their operating range covers flows up to approximately 400 cfm and pressures up to 1 psi differential. See our regenerative blower product page for specifications.

Multistage Centrifugal Blowers

For large-scale municipal wastewater RNG projects and major landfill gas-to-energy applications, multistage centrifugal blowers provide high-volume gas handling capability with variable output. They are well-suited for applications where gas production varies significantly over time, as the centrifugal performance curve allows efficient operation across a wide range of flow rates when paired with inlet throttling or VFD control.

High-Speed Turbo Blowers

For RNG projects demanding maximum energy efficiency at large scale, turbo blowers offer magnetic bearing technology that eliminates lubrication entirely, producing oil-free gas delivery with very low vibration and noise. Their efficiency advantage over conventional PD blowers is most pronounced at continuous, steady-state duty — making them an excellent choice for base-load RNG plants with stable production profiles.