San Diego Greenhouse Gas Emissions

Students in the Environmental Chemistry class at the University of San Diego completed an analysis of the greenhouse gas emissions of several different forms of energy consumption including electricity, industry, and transportation in San Diego County. Greenhouse gas emissions are reported in terms of CO₂, which is one of the most prevalent and significant greenhouse gases and is a potential contributor to global warming. The greenhouse gas emissions are determined by converting the amount of a resource consumed to an equivalent amount of CO₂ released into the atmosphere.

Greenhouse gas emissions for electricity were obtained from San Diego Gas & Electric. The majority of electricity consumption comes from the residential and commercial sectors. Commercial electricity consumption has shown the largest increase since 1990, and the total CO₂ emissions as a result of electricity consumption has increased from 9.3 teragrams CO₂ in 1990 to 13.3 teragrams of CO₂ in 2008. In the residential category, heating and cooling units and kitchen appliances use the most electricity. Suggestions for decreasing CO₂ emissions due to electricity use are to turn off lights and unplug appliances when not in use, and to keep houses well insulated to reduce waste from warm or cold air lost to the outdoors.

In industry, the production of CO₂ has increased dramatically since 1990, from less than 0.02 to over 1 MMT (million metric tons) CO₂. The greatest contributor is the use of HFCs, hydrofluorocarbons, as a substitution for other compounds that deplete ozone. A possible solution would be to replace these with hydrocarbons for particular uses. Of the CO₂ emissions from natural gas used in public transportation and aviation, use of natural gas for buses is the primary source of emissions, which have increased by a factor of almost 10 for that category since 1990. Suggestions to reduce emissions included better regulations to prevent and repair leaks in pipelines, as well as continued efforts to find alternative fuel sources.

Of transportation dependent on gasoline, diesel, or ethanol, emissions from gasoline are highest and increased from ~5 to ~11 MMT CO₂ from 1990 to 2008. Gasoline also has the highest consumption, with over 1 million gallons consumed in San Diego in 2008. The total CO₂ fuel emissions for heavy trucks, SUVs, and cars have increased in San Diego since 1990, but within the categories of SUVs and cars, emissions have decreased since 2007. Some alternative fuel possibilities include switchgrass and sugarcane ethanol and soybean and waste grease biodiesel, which have CO₂ emissions less than 50% of the values for petroleum ethanol and diesel.

The research done on greenhouse gas emissions was accompanied by a study called “Beaker World” in which the earth’s atmosphere was simulated in a beaker. Beakers filled with water and crushed ice were arranged with two beakers under a lamp and one in an unlit area. The contents of the beakers were stirred and the temperature measured with sensor probes for a determined time. In a second trial, compounds common in the atmosphere such as soot and acetone, were added to the beaker contents. The experiment was repeated and showed that the addition of these compounds affected the rate of temperature change of the solutions in the beakers.

The photos below show the Beaker World set-up and Environmental Chemistry students working on the experiment.