Comparison with other natural gas fuels

Drawbacks

Compressed natural gas vehicles require a greater amount of space for fuel storage than conventional gasoline powered vehicles. Since it is a compressed gas, rather than a liquid like gasoline, CNG takes up more space for each GGE (gasoline gallon equivalent). Therefore, the tanks used to store the CNG usually take up additional space in the trunk of a car or bed of a pickup truck which runs on CNG. This problem is solved in factory-built CNG vehicles that install the tanks under the body of the vehicle, leaving the trunk free (e.g., Fiat Multipla, New Fiat Panda, Volkswagen Touran Ecofuel, Volkswagen Caddy Ecofuel, Chevy Taxi - which sold in countries such as Peru). Another option is installation on roof (typical on buses), requiring, however, solution of structural strength issues.

Codes and standards

The lack of harmonized codes and standards across international jurisdictions is an additional barrier to NGV market penetration. The International Organization for Standards has an active technical committee working on a standard for natural gas fuelling stations for vehicles.

Despite the lack of harmonized international codes, natural gas vehicles have an excellent global safety record. Existing international standards include ISO 14469-2:2007 which applies to CNG vehicle nozzles and receptacle and ISO 15500-9:2012 specifies tests and requirements for the pressure regulator.

NFPA-52 covers natural gas vehicle safety standards in the United States.

Comparison with other natural gas fuels

Compressed natural gas is often confused with LNG (liquefied natural gas). While both are stored forms of natural gas, the key difference is that CNG is gas that is stored (as a gas) at high pressure, while LNG is stored at very low temperature, becoming liquid in the process. CNG has a lower cost of production and storage compared to LNG as it does not require an expensive cooling process and cryogenic tanks. CNG requires a much larger volume to store the same mass of gasoline or petrol and the use of very high pressures (3000 to 4000 psi, or 205 to 275 bar). As a consequence of this, LNG is often used for transporting natural gas over large distances, in ships, trains or pipelines, and the gas is then converted into CNG before distribution to the end user.

CNG is being experimentally stored at lower pressure in a form known as an ANG (adsorbed natural gas) tank, at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge like materials, such as activated carbon and MOFs (metal-organic frameworks). The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refueled from the natural gas network without extra gas compression, the fuel tanks can be slimmed down and made of lighter, weaker materials.

Compressed natural gas is sometimes mixed with hydrogen (HCNG) which increases the H/C ratio (heat capacity ratio) of the fuel and gives it a flame speed about eight times higher than CNG.

Worldwide uses

South America

CNG vehicles are commonly used in South America, where these vehicles are mainly used as taxicabs in main cities of Argentina and Brazil. Normally, standard gasoline vehicles are retrofitted in specialized shops, which involve installing the gas cylinder in the trunk and the CNG injection system and electronics. Argentina and Brazil are the two countries with the largest fleets of CNG vehicles, with a combined total fleet of more than 3.4 million vehicles by 2009. Conversion has been facilitated by a substantial price differential with liquid fuels, locally produced conversion equipment and a growing CNG-delivery infrastructure.

As of 2009 Argentina had 1,807,186 NGV's with 1,851 refueling stations across the nation, or 15 percent of all vehicles; and Brazil had 1,632,101 vehicles and 1,704 refueling stations, with a higher concentration in the cities of Rio de Janeiro and São Paulo.

Colombia had an NGV fleet of 300,000 vehicles, and 460 refueling stations, as of 2009. Bolivia has increased its fleet from 10,000 in 2003 to 121,908 units in 2009, with 128 refueling stations. Peru had 81,024 NGVs and 94 fueling stations as 2009, but that number is expected to skyrocket as Peru sits on South America's largest gas reserves. In Peru several factory-built NGVs have the tanks installed under the body of the vehicle, leaving the trunk free. Among the models built with this feature are the Fiat Multipla, the new Fiat Panda, the Volkswagen Touran Ecofuel, the Volkswagen Caddy Ecofuel and the Chevy Taxi. Other countries with significant NGV fleets are Venezuela (15,000) and Chile (8,064) as of 2009.

Asia

In Singapore, CNG is increasingly being used by public transport vehicles like buses and taxis, as well as goods vehicles. However, according to Channel NewsAsia on April 18, 2008, more owners of private cars in this country are converting their petrol-driven vehicles to also run on CNG – motivated no doubt by rising petrol prices. The initial cost of converting a regular vehicle to dual fuel at the German conversion workshop of C. Melchers, for example, is around S$3,800 (US$2,500); with the promise of real cost-savings that dual-fuel vehicles bring over the long term.

Singapore currently has five operating filling stations for natural gas. SembCorp Gas Pte Ltd. runs the station on Jurong Island and, jointly with Singapore Petroleum Company, the filling station at Jalan Buroh. Both these stations are in the western part of the country. Another station on the mainland is in Mandai Link to the north and is operated by SMART Energy. SMART also own a second station on Serangoon North Ave 5 which was set up end of March 2009; The fifth and largest station in the world was opened by the UNION Group in September 2009. This station is recognized by the Guniness World Records as being the largest in the world with 46 refuelling hoses. This station is located in Toh Tuck. The Union Group, which operates 1000 CNG Toyota Wish taxis plan to introduce another three daughter stations and increase the CNG taxi fleet to 8000 units.

CNG scooters (auto rickshaws) in Dhaka, Bangladesh.

As a key incentive for using this eco-friendly fuel Singapore has a green vehicle rebate for users of CNG technology. First introduced in January 2001, the GVR grants a 40 percent discount on the OMV (open market value) cost of newly registered green passenger vehicles. This initiative will end at the end of 2012 as the government believes the 'critical mass' of CNG vehicles would then have been built up.

The Ministry of Transport of Myanmar passed a law in 2005 which required that all public transport vehicles - buses, trucks and taxis, be converted to run on CNG. The Government permitted several private companies to handle the conversion of existing diesel and petrol cars, and also to begin importing CNG variants of buses and taxis. Accidents and rumors of accidents, partly fueled by Myanmar's position in local hydrocarbon politics, has discouraged citizens from using CNG vehicles, although now almost every taxi and public bus in Yangon, Myanmar's largest city, run on CNG. CNG stations have been set up around Yangon and other cities, but electricity shortages mean that vehicles may have to queue up for hours to fill their gas containers. The Burmese opposition movements are against the conversion to CNG, as they accuse the companies as being proxies of the junta, and also that the petrodollars earned by the regime would go towards the defense sector, rather than towards improving the infrastructure or welfare of the people.

In Malaysia, the use of CNG was originally introduced for taxicabs and airport limousines during the late-1990s, when new taxis were launched with CNG engines while taxicab operators were encouraged to send in existing taxis for full engine conversions. The practice of using CNG remained largely confined to taxicabs predominantly in the Klang Valley and Penang due to a lack of interest. No incentives were offered for those besides taxicab owners to use CNG engines, while government subsidies on petrol and diesel made conventional road vehicles cheaper to use in the eyes of the consumers. PETRONAS, Malaysia's state-owned oil company, also monopolizes the provision of CNG to road users. As of July 2008, Petronas only operates about 150 CNG refueling stations, most of which are concentrated in the Klang Valley. At the same time, another 50 were expected by the end of 2008.

As fuel subsidies were gradually removed in Malaysia starting June 5, 2008, the subsequent 41 percent price hike on petrol and diesel led to a 500 percent increase in the number of new CNG tanks installed. National car maker Proton considered fitting its Waja, Saga and Persona models with CNG kits from Prins Autogassystemen by the end of 2008,^[32] while a local distributor of locally assembled Hyundai cars offers new models with CNG kits. Conversion centres, which also benefited from the rush for lower running costs, also perform partial conversions to existing road vehicles, allowing them to run on both petrol or diesel and CNG with a cost varying between RM3,500 to RM5,000 for passenger cars.

In China, companies such as Sino-Energy are active in expanding the footprint of CNG filling stations in medium-size cities across the interior of the country, where at least two natural gas pipelines are operational

A CNG powered car being filled in a filling station in Delhi

In India, the Delhi government under the order of Supreme Court in 2004 made it mandatory for all city buses and auto rickshaws to run on CNG with the intention of reducing air pollution.

The Delhi Transport Corporation operates the world's largest fleet of CNG powered buses.

In Pakistan in 2012, the federal government announced plans to gradually phase out CNG over a period of approximately three years given natural gas shortages which have been negatively affecting the manufacturing sector. Aside from limiting electricity generation capacity, gas shortages in Pakistan have also raised the costs of business for key industries including the fertilizer, cement and textile sectors.

Iran has one of the largest fleets of CNG vehicles and CNG distribution networks in the world. There are 1800 CNG fueling stations, with a total of 10.352 CNG nozzles. The number of CNG burning vehicles in Iran is about 2.6 million.

Africa

Egypt is amongst the top 10 countries in CNG adoption, with 128,754 CNG vehicles and 124 CNG fueling stations. Egypt was also the first nation in Africa and the Middle East to open a public CNG fueling station in January 1996.

The vast majority 780000 have been produced as dual fuel vehicles by the auto manufacturer in the last two years, and the remainder have been converted utilizing after market conversion kits in workshops. There are 750 active refueling stations country wide with an additional 660 refueling stations under construction and expected to come on stream. Currently the major problem facing the industry as a whole is the building of refueling stations that is lagging behind dual fuel vehicle production, forcing many to use petrol instead.

Nigeria CNG started with a pilot project in Benin City Edo State in 2010 by Green Gas Limited. Green Gas Limited is a Joint Venture Company of NGC (Nigerian Gas Company Ltd.) & NIPCO PLC. As at October 2012 about seven CNG stations have been built in Benin City Edo State, with about 1,000 cars running on CNG in Benin City Edo state. In Benin City Edo state, major companies such as Coca-cola are using CNG to power their fork-lifts/trucks while Edo City Transport Ltd (ECTS) is also running some of its buses on CNG.

Europe
In Italy, there are more than 1173 CNG stations. The use of methane for vehicles, started in the 1930s and has continued off and on until today. Since 2008 there have been a large market expansion for natural gas vehicles (CNG and LPG) caused by the rise of gasoline prices and by the need to reduce air pollution emissions. Before 1995 the only way to have a CNG-powered car was by having it retrofitted with an after-market kit. A large producer was Landi Renzo, Tartarini Auto, Prins Autogassystemen, OMVL, BiGAs,... and AeB for electronic parts used by the most part of kit producer. Landi Renzo and Tartarini selling vehicles in Asia and South America. After 1995 bi-fuel cars (gasoline/CNG) became available from several major manufacturers. Currently Fiat, Opel, Volkswagen, Citroën, Renault, Volvo and Mercedes sell various car models and small trucks that are gasoline/CNG powered. Usually CNG parts used by major car manufacturers are actually produced by automotive aftermarket kit manufacturers, e.g. Fiat use Tartarini Auto components, Volkswagen use Teleflex GFI and Landi Renzo components.

In Germany, CNG-generated vehicles are expected to increase to two million units of motor-transport by the year 2020. The cost for CNG fuel is between 1/3 and 1/2 compared to other fossil fuels in Europe in 2008 there are around 800 CNG stations in Germany.

In Portugal there are four CNG refueling stations but three of them do not sell to the public. Only in Braga, can you find public access to CNG refueling—at the local city bus station (TUB).

In Turkey, Ankara has 1050 CNG buses.

In Hungary there are four public CNG refueling stations in the cities Budapest, Szeged, Pécs and Győr. The public transportation company of Szeged runs buses mainly on CNG.

In Bulgaria, there are 96 CNG refueling stations as of July 2011. One can be found in most of Bulgaria's big towns. In the capital Sofia there are 22 CNG stations making it possibly the city with the most publicly available CNG stations in Europe. There are also quite a few in Plovdiv, Stara Zagora and Veliko Tarnovo as well as in the towns on the Black Sea – Varna, Burgas, Nesebar and Kavarna. CNG vehicles are becoming more and more popular in the country. The fuel is mostly used by taxi drivers because of its much lower price compared to petrol.

In Macedonia, there is one CNG station located in the capital Skopje, but it is not for public use. Only twenty buses of the local Public Transport Company have been fitted to use a mixture of diesel and CNG. The first commercial CNG station in Skopje is in the advanced stage of development and is expected to start operation in July 2011.

In Serbia, there are four public CNG refueling stations in the capital Belgrade and in the towns of Pančevo, Kruševac and Čačak.

In Slovenia, there is only one public CNG refueling station in the capital Ljubljana.

In Croatia, there is only one CNG station situated close to the center of Zagreb. At least 60 CNG buses are in use as a form of a public transport (Zagreb public transport services).

In Estonia, there are two public CNG refueling stations - one in the country´s capital Tallinn and the other one in Tartu. From 2011, Tartu has five Scania manufactured CNG buses operating it´s inner-city routes.

In Sweden there are currently 90 CNG filling stations available to the public (as compared to about 10 LPG filling stations), primarily located in the southern and western parts of the country as well the Mälardalen region Another 70-80 CNG filling stations are under construction or in a late stage of planning (completions 2009-2010). Several of the planned filling stations are located in the northern parts of the country, which will greatly improve the infrastructure for CNG car users. There are approx. 14,500 CNG vehicles in Sweden (2007), of which approx. 13,500 are passenger cars and the remainder includes buses and trucks. In Stockholm, the public transportation company SL currently operates 50 CNG buses but have a capacity to operate 500. The Swedish government recently prolonged its subsidies for the development of CNG filling stations, from 2009-12-31 to 2010-12-31.

In Spain the EMT Madrid bus service use CNG motors in 672 regular buses. Is rare to see another kind of CNG vehicle, and there are no CNG refueling stations.

As of 2010, there are 25 public CNG filling stations in the Czech Republic, mainly in the big cities. Local bus manufacturers SOR Libchavy and Tedom produce CNG versions of their vehicles, with roof-mounted tanks.

Canada
Natural gas has been used as a motor fuel in Canada for over 20 years. With assistance from federal and provincial research programs, demonstration projects and NGV market deployment programs during the 1980s and 1990s, the population of light-duty NGVs grew to over 35,000 by the early 1990s. This assistance resulted in a significant adoption of natural gas transit buses as well.

The NGV market started to decline after 1995, eventually reaching today’s vehicle population of about 12,000.

This figure includes 150 urban transit buses, 45 school buses, 9,450 light-duty cars and trucks, and 2,400 forklifts and ice-resurfaces. The total fuel use in all NGV markets in Canada was 1.9 PJs (petajoules) in 2007 (or 54.6 million liters of gasoline liters equivalent), down from 2.6 PJs in 1997. Public CNG refueling stations have declined in quantity from 134 in 1997 to 72 today. There are 22 in British Columbia, 12 in Alberta, 10 in Saskatchewan, 27 in Ontario and two in Québec. There are only 12 private fleet stations.

Canadian industry has developed CNG-fueled truck and bus engines, CNG-fueled transit buses^, and light trucks and taxis.

USA

Similar to Canada, the United States has implemented various NGV initiatives and programs since 1980, but has had limited success in sustaining the market. There were 105,000 NGVs in operation in 2000; this figure peaked at 121,000 in 2004, and decreased to 110,000 in 2009.

In the United States, federal tax credits are available for buying a new CNG vehicle. Use of CNG varies from state to state; only 34 states have at least one CNG fueling site.

In California, CNG is used extensively in local city and county fleets, as well as public transportation (city/school buses). There are 90 public fueling stations in southern California alone, and travel from San Diego so the Bay Area to Las Vegas and Utah is routine with the advent of online station maps such as www.cngprices.com. Compressed natural gas is typically available for 30-60 percent less than the cost of gasoline in much of California.

The Massachusetts Bay Transportation Authority was running 360 CNG buses as early as in 2007, and is the largest user in the state.

The City of Harrisburg, Pennsylvania has switched some of the city's vehicles to compressed natural gas in an effort to save money on fuel costs. Trucks used by the city's street and water, sewer and gas departments have been converted from gasoline to CNG.

Personal use of CNG is a small niche market currently, though with current tax incentives and a growing number of public fueling stations available, it is experiencing unprecedented growth. The state of Utah offers a subsidized statewide network of CNG filling stations at a rate of $1.57/gge, while gasoline is above $4.00/gal. Elsewhere in the nation, retail prices average around $2.50/gge, with home refueling units compressing gas from residential gas lines for under $1/gge. Other than aftermarket conversions, and government used vehicle auctions, the only currently produced CNG vehicle in the United States is the Honda Civic GX sedan, which is made in limited numbers and available only in states with retail fueling outlets. An initiative, known as Pickens Plan, calls for the expansion of the use of CNG as a standard fuel for heavy vehicles has been recently started by oilman and entrepreneur T. Boone Pickens. California voters defeated Proposition 10 in the 2008 General Election by a significant (59.8 percent to 40.2 percent) margin. Proposition 10 was a $5 billion bond measure that, among other things, would have given rebates to state residents that purchase CNG vehicles. On February 21, 2013, T. Boone Pickens and New York Mayor, Michael Bloomberg unveiled a CNG powered mobile pizzeria. The company, Neapolitan Express uses alternative energy to run the truck as well as 100 percent recycled and compostable materials for their carryout boxes. Congress has encouraged conversion of cars to CNG with a tax credits of up to 50 percent of the auto conversion cost and the CNG home filling station cost. However, while CNG is much cleaner fuel, the conversion requires a type certificate from the EPA. Meeting the requirements of a type certificate can cost up to $50,000. Other non-EPA approved kits are available. A complete and safe aftermarket conversion using a non-EPA approved kit can be achieved for as little as $400 without the cylinder.

Oceania

During the 1970s and 1980s, CNG was commonly used in New Zealand in the wake of the oil crises, but fell into decline after petrol prices receded. At the peak of natural gas use, 10 percent of New Zealand's cars were converted, around 110,000 vehicles.

Brisbane Transport in Australia has adopted a policy of purchasing only CNG buses in future. Brisbane Transport has 215 Scania L94UB and 324 MAN 18.310 models as well as 30 MAN NG 313 articulated CNG buses. The State Transit Authority of New South Wales (operating under the name "Sydney Buses") operates 100 Scania L113CRB buses, 299 Mercedes-Benz O405NH buses and 254 Euro 5-compliant Mercedes-Benz OC500LE buses.

In the 1990s Benders Busways of Geelong, Victoria trialed CNG buses for the Energy Research and Development Corporation.^.

Martin Ferguson, Ollie Clark and Noel Childs featured on ABC 7.30 Report raised the issue of CNG as an overlooked transport fuel option in Australia, highlighting the large volumes of LNG currently being exported from the North West Shelf in light of the cost of importing crude oil to Australia.

Conclusion

To sum up, we see that CNG has a lot of advantages and not so many disadvantages. But it does not interfere with technology of CNG to develop.

However, CNG cars produce less emissions and greenhouse gases than their gasoline- and diesel-powered “brothers”.

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