About CNG & H-CNG

About CNG & H-CNG

  • CNG is compressed natural gas. With natural gas mainly composed of methane, CNG emits less air pollutants — carbon dioxide, carbon monoxide, nitrogen oxides and particulate matter — than petrol or diesel.
  • H-CNG is a blend of hydrogen and CNG, the ideal hydrogen concentration being 18%. Compared to conventional CNG, use of H-CNG can reduce emission of carbon monoxide up to 70%, besides enabling up to 5% savings in fuel.


Advantages of the shift from CNG to H-CNG

  • The most promising aspect of this technology is that it will allow for the utilisation of the existing infrastructure of CNG — buses as well as the piping network and dispensing station.
  • Hydrogen has a unique property of extremely lean burning: ƒ
    • Extends lean misfire limit of CNG engines.ƒ
    • Lean burn results in lower combustion peak temperature which reduces NOx emissions (upto 50% with 20% HCNG).ƒ
  • Improves thermal efficiency Using H2 as an additive to CNG provides: ƒ
    • Lower risk due to very low energy content from H2 ‐safety properties similar to CNG.
    • Nearly commercial technology to start using hydrogen
    • No major Engine modifications required ƒ
    • Increased Nox emissions in Cities can be mitigated by supplementing CNG with hydrogen.ƒ
    • For lower blends existing CNG infrastructure can be utilized for using hydrogen without taking the risk of huge investment in creating the infrastructure.



  • The gas storage system may be impacted if the hydrogen concentration goes up.
  • Some “minor engine optimisation” is needed to make existing buses H-CNG-ready as it will involve “high temperature combustion”. Existing buses need not be replaced.
  • Delhi’s public transport includes autos and cars, but these would not be able to use H-CNG with the prevailing technology, mainly because hydrogen is “highly volatile” and the possibility of a rise in combustion temperature.
  • Physical blending of CNG and hydrogen involves a series of energy-intensive steps that would make H-CNG more expensive than CNG.
  • Addition of Hydrogen with CNG results in reduction of net energy content of the mixed fuel ‐ 20% H2 in CNG results in 14.4 % reduction in mixture energy content.


Way forward

  • Mass production of the fuel will further lower the cost.
  • The costs are not prohibitive and if further work can be done to reduce NOX emissions, then this approach – an intermediate hydrogen technology approach can be scaled up and implemented across the full bus fleet in the city within 2-3 years.
  • IOCL’s research & development wing has developed a technology that does away with the need for physical blending.
  • Its ‘Compact Reforming Process’ directly produces a hydrogen-CNG mixture from natural gas, using a single step.
  • The cost of production is significantly lower than physical blending.
  • Cost can be reduced by innovative hydrogen production technologies in future.
  • India has an ambitious plan to have one million hydrogen fuelled vehicles by 2020 mostly two and three-wheelers. Hence, it should be promoted as the fuel of the future.


About EPCA

  • The Central government constituted an authority- The Environment Pollution (Prevention and Control) Authority for the National Capital Region under the Environment (Protection) Act, 1986.
  • The Authority has the following powers and functions for protecting and improving the quality of the environment and preventing, controlling and abating environmental pollution:
    • Standards for the quality of the environment in its various aspects.
    • Standards for omission or discharge of environmental pollutants from various sources.
    • Restriction of areas in which any industries, operations or processes or class of industries or processes shall not be carried out or shall be carried out subject to certain safeguards.
    • Procedures and safeguards for the prevention of accidents which may cause environmental pollution and remedial measures for such accidents.
    • Procedures and safeguards for the handling of hazardous substances.