vehicle fuel and pipeline standards (fuel standards for vehicles)

Vehicle fuel and pipeline standards are the technical purity, composition and pressure specifications that compressed biogas must meet before it can be dispensed into vehicles or injected into India's natural gas grid. The governing specification is IS 16087:2016 from the Bureau of Indian Standards, harmonised with the requirements of City Gas Distribution licensees and Oil Marketing Companies.

The key parameters laid down for CBG include methane content of at least 90% by volume (some buyers insist on 92-95%), carbon dioxide below 4%, total sulphur including hydrogen sulphide below 20 mg/Nm³, oxygen below 0.5%, moisture as dew point at or below −10°C at line pressure, and trace particulate matter removed to below 5 microns. Dispensing pressure at retail CNG stations is typically 200-250 bar, while grid injection occurs at the local CGD network pressure of 4-19 bar.

These limits exist for specific failure-mode reasons. Hydrogen sulphide combusts to SO₂ and forms sulphuric acid in engines and pipelines, corroding cylinders, regulators and combustion chambers. Moisture combines with CO₂ to form carbonic acid, causing the same corrosion at lower temperatures. Excess CO₂ lowers calorific value below the 47-49 MJ/kg expected of CNG, triggering engine knock and reduced range. Siloxanes, while not always limit-listed, form abrasive silica deposits on pistons and valves.

Conformance is verified through gas chromatography and online H₂S analysers at the plant gate. SATAT-registered plants must produce a batch test certificate for each tanker load before the OMC accepts delivery. Non-conforming gas is rejected outright; repeated failure can suspend the offtake contract. The trade-off for the producer is that final polishing — typically a second-stage amine wash or pressure swing adsorption unit — adds 8-12% to upgrading capex but is non-negotiable for any plant aiming at vehicle fuel or grid injection markets.