Delivering Opportunity

The document provides a technical appendix describing the life cycle emissions modeling for urban buses in California, comparing diesel, compressed natural gas (CNG), hydrogen fuel cell, and battery electric options. It details modifications to the CA-GREET 2.0 and Vision 2.0 models to better reflect California-specific fuel pathways and electricity grid mixes. Key findings include the significant reduction of global warming emissions when using 100% renewable energy for electric buses and the role of biomass and coal in the grid's particulate matter emissions. The analysis also examines the impact of low-carbon biofuels and low-NOx engines on overall emissions profiles.

• Battery electric buses powered by 100% renewable energy result in zero total life cycle global warming emissions, whereas conventional diesel buses produce 2,878 g CO2e/mi.
• The 2016 California average electricity grid mix results in a 20% reduction in PM2.5 emissions compared to the diesel baseline, though 94% of the emissions in this pathway are attributed to coal and biomass, which together account for approximately 10% of the electricity used.
• Electric buses are significantly more energy-efficient than CNG buses; an electric bus powered by a natural gas power plant can travel the same distance as a CNG bus while using 55% less natural gas.
• Life cycle NOx emissions are lowest for electric buses powered by 100% renewable energy (0 g NOx/mi) and highest for diesel buses using 100% renewable diesel (2.90 g NOx/mi).
• Coal-fired electricity is expected to be virtually eliminated from California by 2026 due to Senate Bill 1368 and the inability to renew contracts with out-of-state coal plants.
• The use of low-NOx engines in CNG buses reduces tailpipe NOx emissions by 90% compared to traditional CNG buses, though these engines do not significantly reduce life cycle PM emissions because tailpipe PM is only 4% of the total life cycle PM for traditional CNG buses.

APA

Union of Concerned Scientists (2016). Delivering Opportunity. https://www.ucs.org/sites/default/files/attach/2016/10/delivering-opportunity-appendix-c.pdf

Chicago

Union of Concerned Scientists. Delivering Opportunity. 2016. https://www.ucs.org/sites/default/files/attach/2016/10/delivering-opportunity-appendix-c.pdf.

Wikipedia

{{cite report |author=Union of Concerned Scientists |title=Delivering Opportunity |date=2016 |url=https://www.ucs.org/sites/default/files/attach/2016/10/delivering-opportunity-appendix-c.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{unionofconcernedscientists2016delivering, author = {{Union of Concerned Scientists}}, title = {{Delivering Opportunity}}, institution = {Union of Concerned Scientists}, year = {2016}, url = {https://www.ucs.org/sites/default/files/attach/2016/10/delivering-opportunity-appendix-c.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }