Berkeley Energy and Climate Institute

This study developed a consumption-based emissions inventory (CBEI) for the City and County of San Francisco, California from 1990 to 2015. CBEIs allocate all greenhouse gas emissions throughout product and service supply chains to final demand, namely households and governments. We find that average household carbon footprints in San Francisco decreased by 17% over the 25-year study period, and were 21% lower than the national average by 2015. Low rates of motor vehicle usage, small home (building) size, small household size, high prevalence of renters, population density, moderate climate, and relatively lowcarbon electricity all contributed to lower consumption-based emissions. These factors outweighed the countervailing effects of income and education, which tend to increase consumption and associated carbon footprints. Despite progress at reducing emissions on a per household basis, on aggregate, the total city-wide CBEI was only 2% lower in 2015 compared to 1990 levels. This reality reflects population pressures and the challenge of reducing emissions that depend on global supply chains. Traditional GHG inventories tend to neglect the effect of consumer demand on supply chain emissions, thus underestimating a city’s total impact. San Francisco’s CBEI is 2.5 times larger than the city’s traditional, more limited inventory. Tracking of full consumption-based inventories over time should aid in the development of new targets, policies, programs, incentives, and communications based on the unique opportunities for responsible production and consumption within San Francisco.

Life cycle assessment is a powerful framework for economic, social, and environmental cost pricing of consumer goods and services. We have extended the capacity of input-output life cycle assessment to approximate cradle-to-consumer environmental impacts from the manufacturing, transport and trade of >600 categories of consumer products and services. On average, 23 tons of CO2 equivalent greenhouse gases are embodied in the food, goods and services consumed by U.S. households. Particularly promising opportunities exist to provide environmental information directly to consumers for products at the point of sale. At a cost of $10/tCO₂, we estimate that incorporating the mitigation cost of carbon would add only about 0.5% to the price of goods and services, and 1% to the price of food. This information can lead to the creation of market-based incentives for more sustainable consumption and production.