Most biogas plants lose up to 40% of their potential energy and vent thousands of tons of CO₂ each year. ISEN retrofits these plants with modular membrane-based systems that capture emissions without solvents or thermal regeneration, recover heat through three-tier cascades, and produce renewable fuels—achieving 40-60% higher profitability vs biogas-only operation.

Figure 1. ISEN Biogas Integration Flow – Turning Waste into Value.
CO₂ captured from biogas upgrading exhaust is separated via membrane cascade, combined with renewable hydrogen (pipeline or on-site), and converted into synthetic fuels while recovering process heat—creating verified negative emissions within a circular carbon loop.

CO₂ Capture & Utilisation

ISEN's biogas integration is based exclusively on membrane separation, enabling CO₂ capture from biogas upgrading exhaust without solvents, absorbers, or chemical regeneration.

Membrane Technology Advantages for Biogas:

Unlike amine-based systems that require thermal regeneration, chemical handling, and complex control systems, ISEN's membrane cascade operates on simple pressure differentials:

• No chemical solvents → Eliminates hazardous material handling and waste disposal
• No thermal regeneration → Zero steam demand for capture (vs 2.5-4.0 GJ/t for amine systems)
• Fully electric operation → Integrates seamlessly with renewable power and grid flexibility
• Rapid response time → Minutes, not hours (ideal for variable biogas production)
• Low maintenance → Comparable to compressor stations, not chemical plants
• Small footprint → Modular skids integrate within existing plant boundaries

CO₂ Utilization Pathways:

Captured biogenic CO₂ (75-85% recovery, ≥98% purity after compression and drying) is converted into valuable products:

1. Synthetic fuel synthesis (e-methanol, e-methane) via catalytic reaction with renewable hydrogen
2. Local greenhouse supply (food production, horticulture)
3. Industrial carbonation (beverages, chemicals)
4. Optional geological storage where infrastructure exists (traditional BECCS pathway)

Key benefits:

• Up to 90% emission reduction from biogas operations
• Enables negative-emission certification (biogenic CO₂ captured and utilized/stored)
• Multiple revenue streams: fuel products (500-700 €/t) + carbon credits (80-100 €/t) + heat recovery
• 30% lower CAPEX vs amine-based capture systems

Hydrogen Integration (Power-to-X)

Membrane separation delivers a clean, dry CO₂ stream (≥98% purity, <50 ppm H₂O) suitable for downstream Power-to-X applications without the chemical contaminants or liquid waste streams typical of amine-based capture systems.

Hydrogen Sourcing Flexibility:

ISEN integrates renewable hydrogen with captured biogenic CO₂ to synthesize carbon-neutral fuels. Hydrogen sourcing is tailored to site-specific conditions:

• Primary mode: Connection to regional hydrogen pipeline networks or nearby electrolyzer facilities
• Optional mode: On-site modular electrolyzer (PEM or alkaline) for remote biogas plants or sites with abundant curtailed renewable electricity
• Transition mode: Blue hydrogen (natural gas + CCS) where renewable H₂ infrastructure is developing

The modular design supports phased deployment—start with CO₂ capture and heat recovery, then add hydrogen integration as economics and infrastructure develop—enabling capacity expansion aligned with biogas production and offtake requirements.

Key benefits:

• Converts curtailed renewable power into storable, transportable liquid fuels (vs battery storage)
• Increases total energy output 20-25% without additional feedstock consumption
• Provides flexible grid balancing and multi-hour energy storage capability
• Creates new revenue streams from e-methanol (500-700 €/t) vs biogas-only operation
• Future-proofs facilities for evolving hydrogen economy and Power-to-X markets

Synthetic Methane & Methanol Production

Through catalytic synthesis, ISEN converts captured biogenic CO₂ and renewable hydrogen into carbon-neutral synthetic fuels: 

Product Options:

• e-Methane (Synthetic Natural Gas): Direct injection into existing gas grid infrastructure or use as vehicle fuel (CNG/LNG replacement)
• e-Methanol: Maritime fuel (IMO 2030+ compliant), road transport fuel, or precursor for sustainable aviation fuel (SAF) via alcohol-to-jet pathways
• Production scale: 25-30 kt/year methanol from 50 kt/year CO₂ capacity plant

Operational Advantages:

By eliminating solvents and chemical regeneration (inherent to membrane architecture), ISEN reduces operational complexity, improves plant availability (>99% uptime vs 85-90% for amine systems), and lowers total lifecycle costs for biogas operators.

The fully modular design enables biogas plants to start with base upgrading, add CO₂ capture for credits, then expand to synthetic fuel production as hydrogen infrastructure and market demand develop—minimizing upfront capital risk.

Key benefits:

• High-value products compatible with existing gas grid and transport infrastructure
• EU RFNBO-compliant (Renewable Fuels of Non-Biological Origin) for maximum subsidy eligibility
• Multiple revenue streams: Fuel sales (500-700 €/t methanol) + carbon credits (80-100 €/t) + district heat (8-10 €/MWh)
• Proven catalyst systems (Cu/ZnO/Al₂O₃ for methanol, Ni-based for methanation)
• Drop-in compatibility with biogas plant infrastructure (no process redesign required)

Thermal Integration & District Heating

ISEN maximizes efficiency through a three-tier thermal cascade that recovers heat across multiple temperature levels from both CO₂ membrane separation and methanol synthesis processes.

Recovered heat is integrated with:

• District heating networks (supply: 90-130°C, return: 65-80°C)
• On-site biogas processes (digestate drying, fermenter heating, building heat)
• Seasonal thermal storage (where available)

Thermal Recovery Architecture:

• Tier 1 (High-grade): Methanol synthesis reactor heat (200-280°C) → Process steam or high-temperature district heating
• Tier 2 (Medium-grade): CO₂ compression intercooler heat (90-130°C) → District heating supply network
• Tier 3 (Low-grade): Compression aftercooler and dryer regeneration heat (65-80°C) → District heating return line or digestate drying

Typical Recovery: 20-30 GWh/year thermal energy (50,000 t/year CO₂ capacity plant)

This multi-tier approach improves total plant efficiency to >90% (vs 40-50% for biogas-only electricity generation) while replacing fossil heat sources in district heating networks.

Key benefits:

• Monetizes waste heat: 1-1.5 M€/year additional revenue at 8-10 €/MWh
• Supports local energy independence and decarbonization of heating sector
• Strengthens municipal climate goals (fossil heat replacement)
• Reverses traditional economics: Heat becomes revenue OUTPUT instead of required INPUT (vs amine systems requiring 2.5-4.0 GJ/t steam for regeneration)

Digital Control & ESG Reporting 

All ISEN-upgraded biogas systems are controlled by IDOS (ISEN Digital Optimization System)—an AI-driven platform that optimizes process performance in real-time and feeds operational data to the Freyra ESG Dashboard for compliance reporting.

IDOS Process Optimization:

• Real-time efficiency optimization: Adjusts capture rates, compression loads, and synthesis parameters based on electricity prices, biogas production rates, and heat demand
• Predictive maintenance forecasting: Monitors membrane performance, compressor health, and catalyst activity to schedule maintenance before failures
• Economic dispatch control: Maximizes revenue by balancing methanol production vs biogas grid injection vs heat export vs grid flexibility services
• Performance benchmarking: Continuous comparison against design specifications and similar installations

Freyra ESG Dashboard Reporting:

• CO₂ capture volume and fuel output (real-time mass balance verification)
• Energy flows: Electricity consumption, hydrogen input, biogas production, heat recovery, and grid interactions
• Verified carbon credits: Automated EU ETS documentation with third-party verification integration
• ESG compliance metrics: Scopes 1-3 carbon accounting, CSRD reporting, ISO 14064 alignment

Quantified Value:

• 17% OPEX reduction through predictive maintenance and adaptive operation
• 2-4 M€/year additional profit from optimization vs baseline operation
• >99% uptime through early fault detection and proactive intervention

Key benefits:

• Transparent, investor-grade sustainability metrics with real-time verification
• Predictive operation reduces unplanned downtime by 60-80% vs reactive maintenance
• Seamless regulatory integration: GHG Protocol, CSRD, ISO 14064, EU ETS, CBAM-ready
• Remote monitoring and diagnostics: Reduces on-site staffing requirements

Digestate & Nutrient Valorisation

Nothing is wasted — carbon, heat, and nutrients are all recycled within the local ecosystem.

Digestate Processing Options:

• Thermal drying: Using Tier-3 waste heat (65-80°C) to reduce moisture content, producing concentrated organic fertilizer with lower transport costs
• CO₂ carbonation: Treating liquid digestate with captured biogenic CO₂ to stabilize pH, reduce ammonia emissions, and improve nutrient availability
• Biochar production: Pyrolysis of solid digestate fraction using high-grade process heat, creating long-term carbon sequestration and soil amendment products
• Nutrient recovery: Extracting phosphorus, nitrogen, and potassium for commercial fertilizer products

Circular Economy Benefits:

• Nothing is wasted — carbon, heat, and nutrients are all recycled within the local agricultural ecosystem
• Reduces synthetic fertilizer dependency for local farms (cost savings + emissions reduction)
• Creates additional revenue stream from bio-fertilizer or biochar sales
• Solves digestate disposal challenges (regulatory pressure on land application in many EU regions)
• Strengthens farm-energy plant symbiosis and regional circular economy integration

This integrated approach transforms digestate from a disposal cost (typical: 5-15 €/t handling) into a revenue-generating product (bio-fertilizer: 30-50 €/t, biochar: 200-400 €/t).

ISEN technology also applies to BioMass and waste-to-energy plants. Click button below to Learn more →