Equipment Specifications

Biogas Flare System Specifications

Q: What is the destruction efficiency of a biogas flare?

Enclosed (ground-level) biogas flares achieve 99.5% or greater methane destruction efficiency when properly designed and operated. This is verified through stack testing per EPA Method 25A or Method 18. Enclosed flares maintain controlled combustion conditions with monitored temperature, residence time, and air-to-fuel ratio. Open (candlestick) flares typically achieve 96-98% destruction efficiency but are not suitable for compliance where 99%+ destruction is required. EFI recommends enclosed flares for all new installations to meet current and anticipated regulations.

Q: What size flare do I need for my biogas system?

Flare sizing is based on maximum expected biogas flow rate, biogas composition (methane content), and required destruction efficiency. For covered lagoon digesters, typical biogas production ranges from 50 CFM for small agricultural lagoons to 2000+ CFM for large municipal or industrial systems. The flare must be sized for peak flow conditions plus a 20-25% safety factor. Key sizing parameters include BTU/hr heat input rating, minimum and maximum flow turndown ratio (typically 10:1 for enclosed flares), and site-specific wind conditions.

Q: What emissions regulations apply to biogas flares?

Federal regulations include NSPS (New Source Performance Standards) for specific source categories, NESHAP (National Emission Standards for Hazardous Air Pollutants) for applicable facilities, and EPA Greenhouse Gas Reporting Rules. State regulations vary significantly and may impose stricter requirements on destruction efficiency, monitoring, and reporting. California, for example, requires CARB-certified flares with continuous monitoring. Common permit requirements include 99%+ destruction efficiency, continuous temperature monitoring, flame detection, and periodic stack testing. EFI's engineering team coordinates with state and local agencies to ensure compliance.

Q: What is the difference between an enclosed flare and an open flare?

Enclosed (ground-level) flares combust biogas inside a refractory-lined steel cylinder, providing controlled combustion conditions, higher destruction efficiency (99.5%+), reduced noise and light pollution, and wind protection. They include temperature monitoring, flame detection, and can meet stringent emissions requirements. Open (candlestick) flares are simpler and less expensive, burning gas at an elevated tip exposed to ambient conditions. They achieve lower destruction efficiency (96-98%), are affected by wind, and produce visible flame. Enclosed flares are recommended for all compliance applications and are increasingly required by regulators.

Q: How are biogas flare systems controlled and monitored?

Modern biogas flare systems use PLC-based (programmable logic controller) control systems with SCADA (supervisory control and data acquisition) integration for remote monitoring. Standard controls include automatic ignition with flame detection (UV or thermocouple), combustion chamber temperature monitoring and control, gas flow measurement, automatic blower speed modulation for air-to-fuel ratio control, low/high pressure safety shutdowns, and alarm notification via cellular or internet. Data logging captures operating parameters for compliance reporting. EFI systems include 24/7 remote monitoring capability with automatic restart after safe shutdown conditions.

Enclosed and open flare types, destruction efficiency, operating parameters, emissions compliance requirements, and PLC/SCADA control system specifications.

Flare Types & Specifications

Three flare configurations for biogas destruction, each suited to different capacity requirements and regulatory environments.

Enclosed (Ground-Level) Flare

Biogas combusted inside a refractory-lined steel cylinder at ground level. Industry standard for compliance applications.

Destruction Efficiency	≥99.5% (methane)
Capacity Range	50-2,000+ CFM biogas
Heat Input Rating	0.5-20+ MMBtu/hr
Combustion Temperature	1,400-1,800°F (760-982°C)
Residence Time	≥0.3 seconds at design temperature
Turndown Ratio	10:1 (minimum to maximum flow)
Stack Height	15-40 ft (4.6-12.2 m) typical
Shell Material	Carbon steel with refractory lining (2,300°F rated)
Ignition	Automatic spark or pilot; redundant flame detection
Wind Rating	Operates in winds up to 60+ mph
Noise Level	<85 dBA at 100 ft (30 m)
Visible Emissions	No visible flame or smoke under normal operation

Open (Candlestick) Flare

Elevated tip flare with gas burned at the top of a vertical pipe. Lower cost, simpler installation, but lower destruction efficiency.

Destruction Efficiency	96-98% (methane)
Capacity Range	25-1,000 CFM biogas
Heat Input Rating	0.25-10 MMBtu/hr
Combustion Temperature	1,200-1,600°F (649-871°C)
Residence Time	Variable (wind-dependent)
Turndown Ratio	5:1 typical
Stack Height	20-60 ft (6.1-18.3 m) typical
Tip Material	Stainless steel (316 or 310 grade)
Ignition	Continuous pilot or automatic spark
Wind Rating	Flame stability affected above 30 mph
Noise Level	Variable; higher in crosswind conditions
Visible Emissions	Visible flame; may produce smoke at high flow

Auto-Ignition Flare

Self-contained flare with automatic ignition for intermittent gas flows. Used as emergency backup or for low-flow applications.

Destruction Efficiency	97-99% (methane)
Capacity Range	10-200 CFM biogas
Heat Input Rating	0.1-2 MMBtu/hr
Combustion Temperature	1,200-1,600°F (649-871°C)
Residence Time	≥0.2 seconds
Turndown Ratio	3:1 to 5:1
Stack Height	10-25 ft (3.0-7.6 m) typical
Ignition	Thermocouple-activated auto-ignition
Power Requirement	Solar/battery or 120V AC
Wind Rating	Wind screen included; rated to 40 mph
Maintenance	Minimal; quarterly inspection typical
Typical Use	Emergency backup, low-flow, remote sites

Operating Parameters

Key operating parameters for enclosed biogas flare systems.

Parameter	Value / Range	Notes
Combustion Temperature	1,400-1,800°F (760-982°C)	Enclosed flares; higher temp = higher destruction efficiency
Minimum Residence Time	≥0.3 seconds	At design temperature for 99.5%+ destruction
Air-to-Fuel Ratio	1.1-1.3:1 (10-30% excess air)	Controlled by combustion air blower; lean operation prevents smoke
Minimum Methane Content	≥35% CH₄ (auto-sustaining)	Below 35% requires supplemental fuel or enrichment
Maximum H₂S in Gas	Varies by manufacturer; typically <3,000 ppm	Higher H₂S requires stainless internals; produces SO₂ in exhaust
Gas Inlet Pressure	2-15 in WC (0.5-3.7 kPa)	Low pressure; blower-assisted designs handle lower inlet pressures
Gas Inlet Temperature	40-130°F (4-54°C)	Condensate knockout required upstream of flare
Pilot Gas Consumption	0.5-2.0 CFM natural gas or propane	Continuous pilot; some designs use biogas for pilot
Power Consumption	5-25 kW (blower, controls, ignition)	Varies by capacity; includes combustion air blower
Start-up Time	30-120 seconds to operating temperature	Automatic restart sequence; pre-purge required

Emissions Compliance

Federal and state regulatory framework for biogas flare systems. Requirements vary by source category, state, and facility size.

Regulation	Description	Key Requirements
NSPS (40 CFR 60)	New Source Performance Standards for specific source categories (landfills, POTW, etc.)	Varies by subpart; typically 99%+ destruction, continuous monitoring
NESHAP (40 CFR 63)	National Emission Standards for Hazardous Air Pollutants	Source-specific; may require enclosed flare with temperature monitoring
EPA GHG Reporting (40 CFR 98)	Greenhouse Gas Reporting Program for facilities >25,000 MT CO₂e/yr	Quantify and report methane destruction; document flare efficiency
NSPS Subpart WWW	Municipal Solid Waste Landfills (existing)	98% destruction by weight or enclosed flare at 1,500°F + 0.5 sec
NSPS Subpart XXX	Municipal Solid Waste Landfills (new)	99%+ destruction or enclosed flare at 1,500°F + 0.5 sec
State Regulations	State-specific air quality requirements (varies significantly)	May be more stringent than federal; CA requires CARB certification
Title V Permit	Major source operating permit for facilities exceeding thresholds	Monitoring, recordkeeping, reporting per permit conditions

Regulatory requirements are subject to change. EFI coordinates with state and local agencies to ensure current compliance for each project. This table is for reference only and does not constitute regulatory guidance.

Control & Monitoring Systems

PLC-based control and SCADA-integrated monitoring for all enclosed flare systems.

PLC Controller

Allen-Bradley, Siemens, or equivalent industrial PLC for all flare logic, safety interlocks, and sequence control.

Flame Detection

Redundant UV flame scanner and/or thermocouple. Automatic shutdown on flame loss with timed re-ignition attempts.

Temperature Monitoring

Type K thermocouple in combustion chamber. Continuous logging. Alarm on low temperature (<1,400°F) or high temperature.

Gas Flow Measurement

Thermal mass flow meter or orifice plate with DP transmitter. Totalizer for compliance reporting.

Pressure Monitoring

Gas inlet pressure transmitter with high/low pressure safety shutdown. Relief valve for overpressure protection.

Blower Control

Variable frequency drive (VFD) on combustion air blower. Modulates air-to-fuel ratio based on gas flow.

SCADA Integration

Modbus TCP/IP, Ethernet/IP, or cellular gateway for remote monitoring. Real-time dashboards and historical trending.

Auto-Restart

Automatic restart sequence after safe shutdown: pre-purge, pilot ignition, main flame verification, ramp to operating temperature.

Data Logging

On-board data logger with 1-year+ storage. Records temperature, flow, pressure, flame status, and alarm events.

Alarm Notification

SMS, email, or phone call alerts for shutdown, alarm, and maintenance conditions via cellular or internet connection.

Frequently Asked Questions

What is the destruction efficiency of a biogas flare?

Enclosed flares achieve 99.5%+ methane destruction, verified by stack testing per EPA Method 25A or 18. Open (candlestick) flares achieve 96-98%. EFI recommends enclosed flares for all new installations to meet current and anticipated regulations.

What size flare do I need for my biogas system?

Sizing is based on maximum biogas flow rate, methane content, and required destruction efficiency. Typical CLD systems produce 50-2,000+ CFM. Size for peak flow plus 20-25% safety factor. Key parameters: BTU/hr rating, turndown ratio (10:1 for enclosed), and site wind conditions.

What emissions regulations apply to biogas flares?

Federal: NSPS for specific source categories, NESHAP for applicable facilities, EPA GHG Reporting Rules. State regulations vary and may be more stringent -- California requires CARB-certified flares with continuous monitoring. Common requirements: 99%+ destruction, continuous temperature monitoring, periodic stack testing.

What is the difference between an enclosed flare and an open flare?

Enclosed flares combust gas inside a refractory-lined cylinder: 99.5%+ destruction, no visible flame, low noise, wind-resistant. Open flares burn at an elevated tip: 96-98% destruction, visible flame, wind-affected, lower cost. Enclosed flares are recommended and increasingly required by regulators.

How are biogas flare systems controlled and monitored?

PLC-based controls with SCADA integration for remote monitoring. Standard features: auto-ignition, flame detection (UV/thermocouple), temperature monitoring, flow measurement, VFD blower control, safety shutdowns, data logging, and cellular/internet alarm notification. 24/7 remote monitoring capability.

Download Flare System Specification Package

Get the complete biogas flare system specification package including equipment data sheets, control system details, and emissions compliance documentation.

Request Spec Package

Define the flare duty before selecting equipment

Share the operating range and permit requirements so the inquiry includes the information needed for equipment selection.

Minimum, normal and peak gas flow, with methane and H₂S analyses
Available inlet pressure and existing gas collection equipment
Air permit conditions, required monitoring and control interfaces

Request a project review