Difference between biogas and compressed biogas
Side-by-side comparison of raw biogas and Compressed Biogas (CBG) covering methane purity, calorific value, impurities, and how each gas is transported — the two states of the same gas after the upgrading step.
| Feature | Biogas (Raw) | Compressed Biogas (CBG)/ Bio-CNG |
| Methane (CH4) | 55% – 65% | 90% – 95% (High Purity) |
| Impurities | High CO2, H2S, & Moisture | Negligible / Removed |
| Calorific Value | ~19,500 kJ/kg | ~52,000 kJ/kg (High Energy) |
| Applications | Cooking, Heating, Power Gen | Vehicular Fuel, Industrial Fuel |
| Pressure | Low / Atmospheric | Low / Atmospheric |
| Transportation | Only via pipelines (local) | Cylinders & Cascades (Long distance) |
Beyond definitions
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How to read this table
- Each row is a property; the two columns are the two forms of the gas.
- Bold CBG cells in the original table indicate the attribute where CBG holds a clear advantage.
- Calorific values are at standard conditions (0°C, 1 atm); actual values vary slightly by feedstock and upgrading efficiency.
- The Pressure row shows both gases start at low/atmospheric pressure — CBG is compressed to 200–250 bar only at the dispensing or storage stage, not during upgrading.
About this table
Raw biogas and Compressed Biogas (CBG) — also called Bio-CNG — come from the same anaerobic digestion process, but they are very different products once gas upgrading is applied. This table shows six key attributes that separate the two forms, helping readers understand why upgrading is essential before biogas can be used as a vehicle fuel or sold to Oil Marketing Companies (OMCs) under the SATAT scheme.
The most critical difference is methane content. Raw biogas contains 55–65% methane (CH₄), with the remainder being mostly carbon dioxide (CO₂), hydrogen sulfide (H₂S), and moisture. After passing through a gas upgrading unit — typically a Membrane Separation or Pressure Swing Adsorption (PSA) system — the methane concentration rises to 90–95%, meeting IS 16087:2016 fuel quality standards. This purity jump also drives the calorific value from approximately 19,500 kJ/kg for raw biogas to approximately 52,000 kJ/kg for CBG, giving CBG roughly 2.7× the energy density per kilogram.
The impurity removal step is equally important for equipment protection. H₂S at even 100–200 ppm causes corrosion in vehicle engines and compressor components. After upgrading, H₂S levels drop to single-digit ppm or below, and moisture is dried to dew-point levels compatible with high-pressure cylinder storage at 200–250 bar.
The transportation row highlights the commercial consequence: raw biogas can only move by pipeline within a very short radius of the plant. CBG, compressed into cascades and cylinders, can be transported by road to CNG stations and industrial consumers anywhere in the region — unlocking a far larger addressable market than pipeline-constrained biogas ever could.
Key insights
- CBG has roughly 2.7× the calorific value of raw biogas per kilogram (52,000 vs 19,500 kJ/kg), making it far more energy-dense as a transport fuel.
- Upgrading raises methane purity from 55–65% to 90–95%, meeting the IS 16087:2016 standard required for vehicle fuel sales.
- H₂S and moisture — which corrode engines and compressors — are reduced to negligible levels in CBG, enabling direct use in existing CNG-compatible vehicles without modification.
- CBG can be moved in cylinders and cascades to any location, while raw biogas is confined to local pipelines — a fundamental commercial difference.
Methodology & sources
Methane percentages and calorific values are typical industry ranges as of 2024, consistent with IS 16087:2016 and SATAT scheme specifications. Values represent conditions at standard temperature and pressure. Actual plant output may vary by 2–5% depending on feedstock mix and upgrading technology selected.
Related data tables
Bio-CNG Production Yield & Output - Expected Bio-CNG yield
Expected Bio-CNG output in kg/day from a 10 TPD plant for five feedstock types — pressmud gives the highest yield at 1,000 kg/day, while cattle dung gives the lowest at 175 kg/day — with vehicle fuelling equivalents for each.
Feedstock Categories for Bio-CNG Production
Five feedstock types for Bio-CNG production mapped against sources, Indian regional availability, seasonal patterns, and gas yield — a practical reference for site-specific feedstock planning.
Zone 3 - Gas Cleaning & Upgrading - Upgrading Technologies
Side-by-side comparison of three biogas upgrading technologies — Membrane Separation, PSA, and Water Scrubbing — covering how each works, methane recovery %, power demand, maintenance burden, and startup speed.