INTRODUCTION

After independence of India, Delhi, the capital became major centre of commerce, industry and education. Rapid growth of Delhi resulted in significant increase in environmental pollution. Based on the ambient air quality monitored by the central pollution control Board in 1998, it was found that the contribution from vehicles to the ambient air of Delhi is about 70% of total pollution from other industries including thermal power plant and domestic sources. The Hon'ble Supreme Court of India directed the Government of India to take initiative in the use of CNG, an established clean fuel in the world, as transport fuel in Delhi to control increasing levels of ambient air pollution. This order is mainly with regard to Government vehicles and led to the CNG Pilot project by Gas Authority of India Limited (GAIL). Use of CNG was preferred due to availability of Natural Gas Pipeline in and around the city of Delhi.

Gas Authority Of India Limited, the major gas company in India, was entrusted with the responsibility of undertaking the pilot project for use of CNG. The objective of pilot project was to identify and resolve technical, institutional, regulatory and economic issues that would have an impact on using CNG. Initially with the launching of the pilot project, only the government vehicles were to be converted to CNG. 

THE PILOT PHASE-DEVELOPMENT OF CNG IN DELHI GAS SUPPLY

0.15 MMSCMD of natural gas was allocated for use in the transport sector as CNG in Delhi by Government of India. The gas supply to Delhi is from the Hazira-Bijaipur- Jagdishpur (HBJ) gas pipeline. The pressure-available in pipeline across Delhi is around 20-22 kg/cm2g. Hence the required quantities of natural gas for CNG was reliably available.

CNG STATIONS

During pilot phase, the mother station was located at a distance of approximately 25 kms. from Delhi to feed the five numbers of daughter stations, which were installed in Delhi. The design and safety norm for these stations was mainly based on New Zealand Standards. Subsequently when the construction of the gas pipeline through the city was completed, the mother station was shifted to Delhi and three on-line CNG stations were installed making the total number of CNG station in Delhi as nine. 

CNG Conversion

During the pilot phase, bi-fuel conversion kits for gasoline vehicles were mainly installed in the government vehicles. During this period, CNG kits were developed and type approved for most of the gasoline fueled four wheelers on road. During the pilot-phase the conversion of existing diesel buses on dual fuel mode were also tried in Delhi. The trial results indicated limited diesel replacement by CNG (approx 34%), extra fuel consumption and maintenance problems. The trial was discontinued by DTC after logging about 6.5 lakh kms. out of which over 3 lakh kms. was in dual-fuel mode.
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CNG PROPERTIES AND SAFETY ASPECT
The properties of natural gas, unleaded gasoline and diesel are as mentioned below:
 

The data indicates the case of leakage, the gas will not accumulate at the ground but will disperse in the atmosphere. In case of fire, the gas will bum above ground level if combustible mixture is formed.

CNG EMISSIONS

A comparative account of emission measurements made by the apex institutes of India viz. Automotive Research Association of India (ARAI), Vehicle Research & Development Estt. (VRDE) and Indian Institute of Petroleum (IIP) in our country and New Zealand are as reproduced below.

Reduction in Mass Emission with CNG retrofitted in Petrol Vehicles as Certified by ARAI/VRDE in gram per kilometer vehicle run: 

*As per the notification of Ministry  of Surface Transport (MOST), Non-Methane Hydrocarbon shall replace Hydrocarbon. Methane content in Compressed Natural Gas to be used shall not be less than 70%.

In order to have a comparative account of emissions from other countries the following emission data as reported by Gas Association of New Zealand.

REGULATIONS

With the launch of CNG pilot program Oil Industries Safety Directorate (OISD) in consultation with Chief Controller of Explosives (CCoE), equipment manufacturer and GAIL had published the safety standard 01SD-179 after taking into account various safety standards in countries like New Zealand, Italy, USA, etc. where CNG is being used in transport sector for many years. The companies engaged in CNG dispensing and kit fitment are strictly following these guidelines. 
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GOVERNMENT SUPPORT
During the pilot phase of the CNG project, government support was sought and following concessions were given by government:
· Basic custom duty on import of CNG conversion kit was reduced from 35% to 5%. 
· The sales tax on CNG conversion kits applicable was waived.
· The land was made available for CNG on priority basis and at the same terms as applicable for other public utilities.
 

EXPERIENCE OF PILOT PROGRAM

The pilot phase of project established CNG as a clean vehicular fuel and removed all safety apprehensions on CNG handling, transportation and storage etc. The necessary expertise in CNG station engineering, design, construction, operation and maintenance and vehicle conversions were acquired with participation of various research, consultancy and private institutions of Indian & Foreign origin.

DEVELOPMENT OF CNG-CURRENT STATUS SUPREME COURT'S DIRECTIVE
Hon'ble Supreme Court of India vide its judgement dated 28.07.1998 has given directives for compliance:

· GAIL to expedite and expand from 9 to 80 CNG supply outlets by 31.03.2000 in Delhi 
· Entire city bus fleet (DTC & Private) to be steadily converted to single fuel mode on CNG by 31.03.2001 .
· No 8 year old bus to ply except on CNG or other clean fuels after 01.04.2000 
· Replacement of all pre 1990 autos and taxis with new vehicles on clean fuel by 31.03.2000
· Financial incentives for replacement of all post 1990 autos and taxis with new vehicles on clean fuel by 31.03.2001.

PROMOTION OF CNG BY INDRAPRASTHA GAS LIMITED (IGL) IN THE NATIONAL CAPITAL TERRITORY OF DELHI

In December 1998, Indraprastha Gas Limited (IGL), a joint venture company between Gas Authority of India Limited (GAIL), Bharat Petroleum Corporation Limited (BPCL) and Government of Delhi has been formed. After incorporation of IGL, GAIL has transferred all the activities related to CNG project to IGL for its implementation in Delhi. IGL is implementing the CNG program as per directives given by the Hon'ble Court. It is getting all the necessary assistance from The Environment Pollution (Prevention and Control) Authority (EPCA) as EPCA is monitoring the development of the CNG project.

METHODOLOGY ADOPTED FOR CNG DISTRIBUTION

Compressed Natural Gas, as the name suggests, is nothing but the natural gas in compressed form. Due to low energy density of Natural gas, it is compressed to around 250 Bars for automobile use so as to facilitate increased onboard storage in the vehicles.

The CNG in Delhi is presently dispensed by 4 types of stations: 
· DAUGHTER STATION 
These are the stations where natural gas pipeline is not available. At these stations CNG is being transported through cascades (Bundle of Cylinders) fixed on commercial vehicles. These are called mobile cascades. These cascades are filled at those CNG stations, which are installed on Natural Gas pipeline. At daughter stations, CNG is dispensed to vehicles on pressure equilibrium principle resulting in lesser cascade capacity utilization. After few fills of the CNG vehicles, the pressure in the cascade placed at daughter station gets reduced resulting in lesser quantity of CNG fills to the subsequent CNG consumers due to low pressure in the cascade leading to general customer dissatisfaction. It may be noted that at a daughter station, the CNG supply is made available only through mobile cascades. Dispensing CNG from a daughter station generally incurs higher cost but is the only option where there is no pipeline connectivity to source Natural Gas.

· DAUGHTER BOOSTER STATION 
These are also the stations, which are not on natural gas pipelines -like daughter stations. The only difference between daughter station and daughter booster station is that, a variable suction pressure compressor (booster) is installed in-between the mobile cascade and the dispenser. The function of the booster compressor is to draw the gas from the cascade right from 200 kg/cm2 pressure in the cascade to as low as 20 kg./Cm2 pressure. The main advantage of booster compressor is that, irrespective of the pressure in the cascade, the discharge pressure will always remain 200 kg/cm2. instillation of booster compressor helps in higher cascade capacity utilization and increased customer satisfaction. This also helps in evacuating the mobile cascades to a larger extent resulting in less cascade movement on road and reduced the associated cost.

· ON-LINE STATIONS 
Online stations are installed on the pipeline, route and are connected to the natural gas pipeline for its continuous supply. On these stations, compressors with a discharge pressure of around 250 kg/cm2 are installed taking gas from pipeline. Storage cascade (stationary) is also installed for smooth functioning of compressor, which acts as a buffer for CNG supply. Number and capacity of compressor, cascade and dispenser depends upon the requirement and demand of CNG. At these stations, direct retailing/dispensing are also done to different types of vehicles as per requirement.

· MOTHER STATIONS 
These stations are same as those of online stations in configuration. The difference between a mother station and an on-line station is that the filling system is additionally provided for filling of mobile cascades at mother stations.

The choice of different types of CNG station at a location is primary guided by cost of laying the pipeline to the station connecting the natural gas supply source, the requirement of CNG quantity and the types of vehicles, which are needed to be filled.

STATION DESIGNING
The Mother stations were planned with a compressor capacity of 1150 SCMH. The gas engine driven compressors were chosen based on the experience of our operations in the pilot phase. Due to non-availability of reliable electric power, motor driven compressors for CNG operation has not, been considered as a favored option in Delhi. IGL has designed mother stations with 1 dispenser (Single Filling Arm) for Buses and 2 dispensers (Twin Filling Arms) for Cars/Autos. The stationary Cascades, which are installed at the mother stations, are of 3000 litres water capacity. All the equipments procured by IGL were of latest technology. The Compressor generally run on Auto Mode and the Dispensers are designed for Ultra Fast Fill technology.

The On-line stations were designed with 250 SCMH compressor capacity with electric motor drive as the power requirement for such stations is relatively small (less than 100 KW) IGL has designed On-line stations with 2 dispensers (Twin Filling Arms) for Cars/Autos. The stationary Cascade at On-line stations is also designed of 3000 litres water capacity.

Daughter Stations were designed with 1 dispenser (Twin Filling Arm) for Cars/Autos and 2200 litres water capacity mobile cascade. Initially daughter booster stations were not considered considering that, booster compressor could be installed once the CNG demand increases. As of now at 10 Daughter stations, booster compressors have been installed. IGL plans to convert all Daughter Stations to Daughter. Booster by December, 2001. The installation of booster compressors are planned to be carried out either by shifting compressors from On-line stations and replacing on-line compressors with bigger capacity compressors or by installing new booster compressors.

CURRENT STATUS
Having taken over the project with 9 CNG station from GAIL, as on date, IGL has installed additional 76 CNG stations making a total of 85 CNG Stations. The breakup of these stations is as appended below. 
 

At present IGL is supplying CNG to about 50,000 vehicles, which include about 3,000 buses. As per the study conducted by ORG MARG and as per the internal assessment of IGL, by March 2002, there will be about 95,000 CNG vehicles on the roads of NCT, Delhi, which shall include about 8,000 CNG buses.

Due to large number of vehicles which are being converted to CNG, IGL is developing its infrastructure and planned to increase the number of stations to around 120 by March 2002 and to around 140 by March 2003. As per the existing plan, with the commissioning of the compressors the dispensing capacity of IGL will go up to 4.4 lakh kg/day by 30.09.2001. IGL has already ordered additional number of equipments viz. Compressors, Dispensers, Cascades and related items for further augmentation programme in a phased manner with effect from November 2001. IGL is putting more emphasis to install additional online stations and for this IGL is expanding the gas pipeline network in Delhi.

It is our endeavor to have maximum stations on pipeline and all daughter stations with booster compressors.

ECONOMICS OF CNG USE
The most significant factor governing the choice amongst alternative fuels shall be the life cycle economics.

CRITERIA - EFFECTING ECONOMIC BENEFITS OF CNG
· KMS/ LITRE
At present, with retrofit kits being available in case of petrol vehicles in India, the km/litre on CNG on energy equivalent basis is similar to that of petrol.
However, with increase in use of CNG and availability of dedicated optimized engines it shall be possible to take advantage of the greater theoretical engine efficiency obtainable with CNG and achieve higher mileage.

· MAINTENANCE 
Natural gas is a clean burning fuel that reduces vehicle maintenance. This is also resulting in less frequent change of engine oil and spark plug. Hence the cost of maintenance too is lower to motorist fleet owner.

· VEHICLE COST
The present day cost of CNG dedicated vehicle is higher than basic petrol or diesel vehicles. However in case of petrol vehicles the higher cost of CNG conversion/vehicle is paid back within a period of 1-2 years depending VII use of vehicles. In case of diesel the pay back period is higher due to subsidised diesel prices in India.

· LIFE CYCLE COST OFVEHICLE 
With above parameters it is evident that life cycle cost of CNG vehicle taking a life of only 7 years is lower as compared to life cycle cost of petrol or diesel vehicle. This is without any loading on account of any environmental cost. If the cost of environmental pollution is also added the life cycle cost of CNG vehicles shall be much lower.

· FUEL COST 
On energy equivalent basis natural gas cost approximately 1/3rd of cost of gasoline. This means that fuel bill for a consumer using CNG shall be only 33% as compared to petrol. In case of diesel vehicles, the saving is to the tune of around 10% only on energy equivalent basis. Vide letter dated 02-12-98, DTC has furnished that the operating cost of buses driven by BEST, Mumbai is Rs 3.37/Km on CNG against Rs.3.75/Km on diesel mode.
 
 

CONCLUSION
The transportation sector has an enormous impact on the environment and its severity has become alarming in Delhi. The industrial growth and spread of ownership of automobiles, majority of which are two stroke engines, the ambient air quality has been detoriating with a distinct haze in Delhi sky and along with it the increasing number of respiratory diseases amongst the residents of Delhi. With increasing level of awareness about pollutants and its harmful impact on human health, the public opinion in Delhi is to bring back the blue skies and the fresh air, which was prevalent in Delhi about 20 to 30 years back.

It is very established that NGVs can become an effective solution to reduce environmental damages being caused by use of conventional liquid fuels. Having established itself as one of the clean fuels and with the availability of Natural Gas supply pipeline in Delhi, the use of CNG was an obvious choice for Cleaning of Delhi's ambient air. With Hon'ble Supreme Court's directive to augment the number of CNG stations from 9 to 80 and compulsory conversions of commercial fleets of vehicles of National Capital Territory of Delhi, the growth in use of CNG as automotive fuel is bound to be phenomenal. IGL is taking all possible steps to help achieving the objective of transforming Delhi to Clean, Green and Refreshing Delhi.