200–250 bar (200-250 bar)

200-250 bar is the standard storage pressure range for compressed biogas (CBG) in cascade storage banks at bio-CNG stations and in vehicle on-board cylinders. At this pressure, methane gas is compressed to approximately 250-260 times its volume at atmospheric pressure, achieving an energy density that makes CBG practical as a transport fuel. Below this pressure range the vehicle range becomes too short for commercial use; above it the capital and operating costs of compression rise disproportionately.

The convention of 200-250 bar derives from CNG infrastructure. Indian CNG vehicles, regulated under the Central Motor Vehicles Rules and inspected per PESO (Petroleum and Explosives Safety Organisation) norms, use cylinders rated for a working pressure of 200 bar with a test pressure of 300 bar and burst pressure of 450 bar. Cascade banks at filling stations store gas at 250 bar to maintain a pressure differential that enables fast-fill dispensing — a vehicle cylinder fills from 0 to 200 bar in 3-5 minutes by drawing sequentially from low, medium, and high cascade tiers.

Reaching this pressure requires multi-stage reciprocating compression, typically four stages with intercoolers. Compressor power for a 5 TPD CBG plant feeding a 250-bar cascade is around 350-500 kW, representing one of the largest electrical loads on site. Capital cost for the compressor train alone is typically Rs 1.2-1.8 crore, with skid-mounted versions from suppliers like Atlas Copco, Galileo, and Indian OEMs like Mehta Compressors.

Safety regulation is stringent. Cylinders must be PESO-approved, hydro-tested every three years (Type I steel) or five years (Type II/III/IV composite), and replaced after 15-20 years of service. Cascade installations require minimum setback distances from boundary walls (typically 7-10 m), automatic blowdown systems, gas-leak detection, and emergency shutdown valves. The 200-250 bar pressure range is the engineering choice that balances vehicle range, station throughput, cylinder weight, and safety margin — and is essentially the same worldwide for CNG and CBG distribution.