The advocators of CNG Harping on about the safe nature, environmentally and otherwise...resd on.
Original TextFirstly, while CNG consists mostly of methane that causes little pollution as compared to other forms of fuel, gas-run vehicles do emit "ultra fine particles" that penetrate deep into human body and, besides causing respiratory disorders, may also prove carcinogenic. Second, since CNG is stored at high-pressure level, the outcome of any collision could be lethal and result in explosions that could engulf the vehicle in flames. These points must be born in mind before any switch is made to CNG, and should form an object of more research from the point of view of the safety and health of the people.
Courtesy of: http://www.cng.com.pk/news.asp#9
[highlight]It is reported that a minor fire broke out at the filling station at the Indraprastha CNG station in Delhi on August 21 (Aug. 22). This fire came after the accidental fire in the CNG vehicle at New Delhi on August 5.
Risks of accidents at storage and distribution points are very serious and there have been numerous reports on the prevention of fire hazards with gaseous petroleum fuels. Liquid fuels are so formulated that only small portions of volatile compounds mix with air during storage and handling and the risks of fire are lower since the mixture may be lean beyond the
Excerpt from: http://www.hinduonnet.com/2001/08/25/stories/05251307.htm
Some more facts....
Two recent studies cast significant doubt as to the benefits and viability of CNG or LNG as a marine fuel
–Fueling Heavy Duty Trucks: Diesel or Natural Gas Harvard Center for Risk Analysis
–Relative Impact on the Environment and Health from the Introduction of Low Emission City Buses in Sweden SAE Technical Paper Series
Paper 2000-01-1882
The Harvard Study
Compressed Natural Gas (CNG) is compressed to several thousand pounds per square inch
Liquefied Natural Gas (LNG) is stored at temperatures around -260o Fahrenheit
The magnitude of health risks of diesel has been questioned by the Health Effects Institute
Major research efforts are currently underway to enhance the understanding of these health risks
Little is known about the adverse health effects of Natural Gas (Methane) emissions
The Harvard Study
The combination of low sulfur fuel with after-treatment technology (green diesels) is proving to be very effective
Though diesel emissions result in more mass the ultra fine particles of Methane emissions could prove to be more biologically harmful due to their ability to penetrate the body further
Diesel engines posses a significant efficiency advantage over Methane
The Harvard Study
Greenhouse Gas Potential
Methane is 20 times more potent than carbon dioxide as a greenhouse gas
Methane will escape during refueling and storage
Regulators in California have apparently not taken the diesel greenhouse gas advantage into account
The Harvard Study
Relative Safety is an Important Consideration
The National Fire Protection Association gives Methane its highest hazard ranking for flammability (a 4 on a scale of 1 to 4)
Diesel is rated as moderate (2 on the scale)
Methane leaks and spills must be treated with great care
Methane vapors at low temperatures can cause clouds of flammable vapor concentrations
The Harvard Study
Safety Concerns (continued)
The extreme pressure or temperature condition of CNG or LNG pose significant additional hazard
Very special care must be given to the transport, transfer and storage of CNG/LNG
Methane poses significantly higher safety hazards than diesel
Safety concerns about siting fueling facilities may be an obstacle to terminal locations.
The Harvard Study
Significant Performance Issues
Range limitations result from lower performance combined with storage parameters
Complex refueling infrastructure limits routing
A gallon of LNG contains about 60% of the energy in a gallon of diesel
CNG contains even less energy than LNG
Maintenance costs are significantly higher and downtime is predicted to be more problematic.
The Swedish Study
Ozone formation is highest for diesel but with catalyst or particulate trap level is same as methane
Nox emissions can be reduced by 50% with EGR
Particulate emissions can be reduced with trap to level similar from Methane
Diesel fuel with a particulate trap has the lowest acetaldehyde emissions - methane is higher
The lowest cancer risk index is achieved with diesel fuel and a particulate filter
The Swedish Study
CNG has higher Greenhouse Gas Emissions (GHG) than diesel fuel due to lower engine efficiency and higher GHG emissions
Considerable improvements are possible by the reformulation of diesel in combination with aftertreatment technology
Continuing development of engines and aftertreatment devices will diminish the advantage of alternative fuel.
FOr the original text : http://www.captainclark.com/Pages/ngoption.html
