Alternative Fuels: Compressed Natural Gas (CNG)

Background

Compressed Natural Gas (CNG) is a gasoline and diesel fuel alternative consisting primarily of methane. The gas is associated with other fossil fuels (coal or oil) and is created by methanogenic organisms in landfills. The gas is extracted from the source and compressed to a high pressure where it can be stored in a vehicle fuel tank.

Current Activities

The current CARB CNG specification has been undergoing review for a possible update. CARB staff has temporarily put the review effort on hold while ASTM International is developing a fuel quality specification for natural gas used as a motor vehicle fuel (See ASTM Work Item (WK) 40094). The work item is currently going through the ballot process. CARB staff has been participating in the work item development and will wait until the item completes balloting before deciding whether the current CARB specification needs to be amended.

Research Studies

CARB funded several studies that examine the emissions effect of natural gas. The first is the effect of natural gas fuel composition on vehicles study, which was conducted by the University of California at Riverside. This study examined the emission effects that lower Methane Number and higher Wobbe Index gas supplies may have on light and heavy-duty engines. CARB partially funded the heavy duty emission testing portion of the study. The second is the Tool for Emission Processing of LNG Expansion Scenarios (TEMPLES) study, which was developed by the University of California at Irvine (UCI). This study is a predictive model used to estimate changes in GHG and criteria pollutant emissions from mobile and stationary sources. The research studies culminated with reports covering the effect of gas quality on vehicle emissions and with a model that examines the air quality impact of changes to gas quality.

Evaluation of the Performance and Air Pollutant Emissions of Vehicles Operating on Various Natural Gas Blends – Heavy-Duty Vehicle Testing – Phase 1, April 2014
Evaluation of the Performance and Air Pollutant Emissions of Vehicles Operating on Various Natural Gas Blends – Phase 2, March 2015
Impacts of Natural Gas Composition on Air Quality – An Assessment Using TEMPLES Model – Phase 1, May 2014
Impacts of Natural Gas Composition on Air Quality – An Assessment Using TEMPLES Model – Phase 2, March 7, 2016

Converting Vehicles to Compressed Natural Gas Fuel

Individuals interested in converting gasoline or diesel vehicles to operate on an alternative fuel must ensure that the alternative fuel retrofit systems have been certified by CARB. For more information on converting a vehicle to run on compressed natural gas fuel, and for the list of certified retrofit systems for various vehicle makes and models, please visit CARB's web page that covers Certification of Alternative Fuel Retrofit Systems

Current Regulations

Specifications for CNG

Contact

For more information about the Compressed Natural Gas Motor Vehicle Fuels, please contact Alexander Mitchell.

Archived Meetings & Workshops

Date	Description & Materials
May 19, 2010	Public Meeting in Sacramento from 9:00 a.m. to 12:00 p.m. to Discuss Compressed Natural Gas (CNG) Fuel Specifications. Meeting Notice and Agenda Revised Agenda CARB Staff Presentation: color; black and white Stakeholder Presentations Southern California Gas Company San Diego Air Pollution Control District: color; black and white Research Studies SoCalGas/SDG&E Vehicle Report (this link not found) SwRI Heavy Duty Study (this link not found) Sierra Research HD Analysis (this link not found) SwRI Light Duty Study (this link not found) Sierra Research LD Analysis (this link not found) Comment Letters Sempra Energy Utilities Proposed Specifications for Alternative Motor Vehicle Fuels American Honda Motor Company, Inc. Letter Sempra LNG South Coast Air Quality Management District Engine Manufacturers Association Kings Canyon Unified School District St. Croix Research Clean Energy San Diego County Air Pollution Air District Cover Letter Comments Revolution CNG Central Coast Clean Cities Coalition General Motors
August 3, 2005	Public Consultation Meeting in Sacramento from 10:00 a.m. to 3:00 p.m. to Discuss a Draft Proposed Concept to Revise the Motor Vehicle CNG Specifications. Meeting Notice and Agenda Draft CNG Specifications Proposal ARB Staff Presentation (PPT) or (PDF) Research Needs: Aspen Environmental Group: Natural Gas Heat Content Surge by William Walters (PPT) or (PDF) California Energy Commission: Public Interest Natural Gas Air Quality Research Program by Marla Mueller (PPT) or (PDF) Industry Presentations: Bevilacqua-Knight, Inc.: Comments On The Proposed CARB Alternative Fuel Specifications by Steven Sokolsky (PPT) or (PDF) California Natural Gas Vehicle Coalition: NGV Commercial Fuel Spec by Mike Eaves (PPT) or (PDF) Engine Manufacturers Association: Presentation at the CARB Workshop by Roger Gault (PPT) or (PDF) Gas Technology Institute: Natural Gas Composition for NGVs by William E. Liss (PPT) or (PDF) Pacific Gas and Electric Company: Comments to the CARB Draft Proposed Concept – CNG Motor Vehicle Specifications by Tony Estrada (PPT) or (PDF) Shell North America LPG: Presentation at the CARB Workshop by Edgar Kuipers (PPT) or (PDF) SoCal Gas: Comments on the CARB Draft Proposed Concept to Revise Motor Vehicle CNG Specifications by Edwin Harte (PPT) or (PDF) Southwest Research Institute: Study on the Effect of Varying Fuel Composition on Fuel Supplied to Cummins and Detroit Diesel Gas Engines by James Chiu (PPT) or (PDF) Western States Petroleum Association and California Independence Petroleum Association: Presentation at the CARB Workshop by Tom Umenhofer (PPT) or (PDF) Comment Letters: Santa Barbara County Air Pollution Control District by Terry Dressler County of San Luis Obispo Air Pollution Control District by Larry R. Allen
February 17 and 18, 2005	Change of Date: Natural Gas Quality Workshop Notice The California Energy Commission and the California Public Utilities Commission will conduct a joint workshop to address natural gas quality issues on February 17 and 18, 2005 in San Francisco, CA. Notice of Change of Workshop Date
December 8 and 9, 2004	Natural Gas Quality Workshop Notice The California Energy Commission and the California Public Utilities Commission will conduct a joint workshop to address natural gas quality issues on December 8 and 9, 2004 in San Francisco, California. The workshop is being conducted in collaboration with the California Air Resources Board and the California Department of Conservation’s Division of Oil, Gas, and Geothermal Resources. Workshop Notice and Agenda
May 9, 2002	Notice of Cancellation The Hearing for consideration of amendments to the California Alternative Fuels for Motor Vehicle Regulations has been cancelled. A new notice will be published at least 45 days in advance of the public hearing. This notice can be accessed from our website.
March 28, 2002	Notice of Change Location The Meeting Location for Public Hearing scheduled on May 16, 2002 for considering the adoption of Proposed Amendments to the Compressed Natural Gas and Liquefied Petroleum Gas Specifications in the California Alternative Fuels for Motor Vehicle Regulations has been changed. For more information please go to the formal rulemaking area.
February 19, 2002	Notice of Postponement The Public Hearing scheduled on February 21, 2002 for considering the adoption of: Proposed Amendments to the Compressed Natural Gas and Liquefied Petroleum Gas Specifications in the California Alternative Fuels for Motor Vehicle Regulations has been postponed. For more information please go to the formal rulemaking area.
February 14 and 15, 2002	Public Meeting Notice and Agenda to Discuss Proposed Amendments CNG and LPG Motor Vehicle Fuel Specifications CNG Presentation (PPT) (PDF) CNG Attendee List LPG Presentation (PPT) (PDF) LPG Attendee List
December 21, 2001	Proposed Amendments to the Compressed Natural Gas and Liquefied Petroleum Gas Specifications in the California Alternative Fuels for Motor Vehicle Regulations. For more information please go to the formal rulemaking area.
March 7, 2001	Public meeting notice and agenda to discuss CNG motor vehicle fuel quality. CARB Presentation CARB Strawman Proposal CARB Public Meeting Attendance List Kings Canyon Unified School District Fleet Presentation Kings Canyon - Fleet Attachment Engine Manufacturers Association Presentation Southern California Gas Presentation Membrane Technology and Research Presentation
June 21, 2000	Workshop notice and agenda to discuss the need to amend the alternative fuels regulations for LPG or CNG, and draft concepts. CARB Staff Presentation EMA Presentation SoCal Gas Presentation Mendocino AQMD Presentation Antek Presentation CAVTEC Presentation
October 29, 1998	Workshop Notice for October 29, 1998 Re: Evaluation of the Motor Vehicle Fuel Specifications for Compressed Natural Gas CARB Gives First Time Approval to Compressed Natural Gas Truck Parts CARB Certifies State's First Compressed Natural Gas Bus CARB Demonstrates First Natural Gas Powered "Clean Air" School Bus