Evaluation of Opportunities to Mitigate Fugitive Methane Emissions from the California Natural Gas System
Using real-world operations data to optimize heavy-duty vehicles for improved fuel efficiency and reduced emissions.
Lawrence Berkeley National Laboratory
The project was completed in 2016. The final report is published. This work begins with a bottom-up methane emission model for California, using emission factors derived from a 2013 US-EPA inventory. The research team then test the model using atmospheric measurements and inverse modeling. Based on this and other recent work, the research team recommend a tiered measurement strategy to quantify natural gas system methane emissions. This tiered measurement strategy has been used by the California Air Resources Board for their methane emission work. Finally, energy monitoring and retrofit programs for buildings should be enhancedwith leak detection and repair procedures and appliance performance standards should be considered to encourage use of low-emission appliances.
Based on US EPA test procedures for heavy-duty engine emissions, results show that heavy-duty engines meet US EPA and California Air Resources Board emission standards for oxides of nitrogen (NOx) and particulate matter. In-use emissions measurement of the engines operating under load conditions are showing increased ammonia emissions from natural gas vehicles and increased NOx from diesel vehicles. Additional studies are needed to assess in-use emissions, fuel usage, and the impact of technology on fuel consumption and emissions from these engines, particularly those used in goods movement, refuse hauler, transit, and school bus applications.
SCAQMD conducted in-use emissions testing and characterize fuel usage of heavy-duty vehicles used in transit, school bus, refuse hauler, and goods movement applications. The test results can be used to:[br /]
· Improve emissions inventory and vocation-based drive cycles; [br /]
· Develop deterioration factors for engine and after-treatment technologies; [br /]
· Identify technology shortfalls and how to improve the shortfalls; [br /]
· Prioritize staff and financial resources to support advanced engine and after-treatment technologies research and demonstration programs; and [br /]
· Match vehicle technologies to vocations for which technology benefits can be maximized.
Research findings indicate that methane emission estimates are underestimated and that measures must be implemented to reduce methane emissions from the natural gas system. Some of the results are being reported in the analysis that the Energy Commission is preparing to comply with AB 1257.
The results will assist in developing vocation-optimized drive cycles to maximize fuel efficiency.
Vocation-optimized drive cycles will help reduce carbon emission from the transportation sector.