The energy and mass balance of Los Angeles County

Abstract

We conducted an urban "metabolic" study of inputs and outputs of food, water, energy, and pollutants from Los Angeles County, USA. This region has been the subject of recent debate about the nature of population density and distribution as it relates to urban form and associated environmental impacts. We found that with the exception of food imports and wastewater outputs, inputs of resources and outputs of pollutants generally declined on a per capita basis from 1990 to 2000. Reductions likely reflected a combination of changes in public policy, improvements in technology and public infrastructure, and impacts of increases in population density. However, in comparison to other municipalities and urban regions, resource consumption per capita was still relatively high in some categories, particularly inputs of water and transportation energy. Per capita greenhouse gas emissions were lower in Los Angeles County than for the average of the USA as a whole but higher than previous analyses of urban areas internationally, largely due to comparatively high emissions from the transportation sector. Wastewater discharge accounted for less than 40% of water inputs excluding precipitation; however the partitioning of water outputs through other potential losses, specifically evapotranspiration, runoff, and groundwater recharge, remains highly uncertain. We suggest that more detailed information about water losses will greatly improve future mass and energy accounting for analyses of urban environmental sustainability in this semi-arid region.

Socio‐ecohydrology and the urban water challenge

“…However, this is not the case, as important pathways of water loss tend to be poorly monitored or unmonitored. For example, Ngo and Pataki (2008) found that less than 40% of imported water in Los Angeles County could be accounted for in measured wastewater discharge and runoff. In the western United States, much of the imported water used outdoors is presumably lost through ET, although this is highly uncertain as ET is arguably the most difficult component of the water budget to estimate in cities.…”

Progress toward low carbon cities: approaches for transboundary GHG emissions’ footprinting

“…Ngo and Pataki [18], and McGraw et al [19], accounted for GHG emissions for Los Angeles (CA, USA) and Chicago (IL, USA), respectively. Both accounted for a comprehensive set of in-boundary emissions; the former included transboundary emissions from food production and wastewater treatment, whereas the latter did not cover these categories, but did account for freight.…”

A new methodology for quantifying on-site residential and commercial fossil fuel CO2emissions at the building spatial scale and hourly time scale

“…For example, a few studies have quantified fossil fuel CO 2 emissions at the scale of an entire county or city [16,17,[19][20][21]. Other studies have attempted somewhat smaller spatial scales by quantifying emissions at the census tract or 'community' level [22,23].…”