U. C. Irvine
Physics and Astronomy
We analyze automotive and household
contributions to CO2 greenhouse gases in
The California Statewide Residential Appliance Saturation Study, 2004. Numbers have been rounded off to make the relative magnitudes easier to perceive, and any errors in the calculations are my own.
A short term goal is to comply with the
Household electricity use is
about 6,000 kWh per household per year, for 3 residents
average per household. So the household use per capita is 2,000 kWh or
about ¼ of the 8,000 kWh per capita electricity from all
Household Natural Gas use: 400 therms per household x (100,000 BTU/therm) gives 40 million BTU x (117 lbs CO2/million BTU) = 4,700 lbs CO2 per year. We note that this is about the same CO2 emission as that of the average household electricity use.
Total average household CO2 generation:
Totaling 4000 lbs CO2 from electricity plus 4700 lbs CO2 from
natural gas gives 8700 lbs of CO2
generated per year by an average household.
Installing solar water heating for
somewhere around $4,000-$6,000 is said to save 2/3 of the water heating part of
the gas bill. (The EPA quotes 50% to 80% savings.) You can get a
30% federal tax credit up to $2,000 until
The first thing we can do in the house is to replace all lighting with Compact Fluorescent Bulbs, which take only ¼ of the power for the same light. Since
lighting is 22% of home electricity, removing ¾ of it saves 17% or 1/6 of the total 6,000 kWh, leaving only 5,000 kWh of household electricity. At $0.10 per kWh, this gives a yearly savings of $100. The 1/6 savings of CO2 emissions from electricity is (1/6) x 4000 lbs CO2 or a reduction of 670 lbs of CO2 per year. This is where more energy efficient appliances and air conditioning come in, as well as solar adaptation by awnings, tinted or upgraded windows and use of fans to lessen the cooling needs of the house. Getting rid of a second fridge, replacing an old one, turning off equipment when not in use, and avoiding 400 watt plasma screen televisions also help. The plasma set will use over 600 kWh per year, as will background electricity for electric devices and chargers, even when not in use.
Space heating is about 40% of
natural gas usage in the home, producing 1900 lbs CO2 per home in
We have shown how to reduce CO2 from household electricity from 4000 lbs to 3300 lbs by using CFL lights. CO2 from natural gas can be reduced from 4700 lbs to 3100 lbs by installing solar water heating. The average total of 8700 lbs CO2 can then be reduced to 6400 lbs CO2 per year, a reduction of 26%.
We must remember that in the State
The greenhouse gas free electricity production does not have to be counted in the electricity account. We will evaluate coal and natural gas plant CO2 production assuming that they all operate at the average US value of 34% efficiency. This gives for coal, 2080 lbs of CO2 emission per 1000 kWh, and for natural gas, 1170 lbs of CO2 emission per 1000 kWh. By 2010, 20% of the State of California’s electricity will be produced by renewable resources (currently 11%) from large scale solar thermal, concentrator solar photovoltaic, wind and geothermal. Add this to the hydroelectric share of 19% and the nuclear share of 13% will give 52% of electricity which is greenhouse gas (GHG) free. The per capita electricity is about 8,000 kWh per year. The Governor has also proposed a 33% renewable fraction by 2020. This would bring us to 65% GHG free electricity, and the remaining 35% of 8,000 kWh would be 2800 kWh, eventually only from natural gas. At 1170 lbs CO2 per 1000 kWh from natural gas plants, this would give 3300 lbs CO2 per year per capita. Natural gas plant efficiencies can be increased up to 59% by a combined cycle of gas turbines followed by the standard steam turbines. Most new plants are of this type. Cogeneration plants that find a use for the heated water, can increase efficiencies up to 85%. California Bill SB 1368 requires that any plant under new contracts must meet combined-cycle emission limits of 1,100 lbs of CO2 per megawatt hour.
Lacking explicit data from each utility for its emissions, we evaluate them using their source breakdown, and by assuming 34% efficiencies for their coal and natural gas plants. This gives for coal, 2080 lbs of CO2 per 1000 kWh; and from natural gas, 1170 lbs CO2 per 1000 kWh. We compare them by calculating their emissions for 1000 kWh of electricity.
The percentage of greenhouse-gas-free power is different for different power companies in the State. Hydroelectric power is mostly in the North part of the State. For SC Edison for 2006, nuclear is 17%, renewables are 16%, large hydro is 5%, coal is 8%, and natural gas is 54%. The renewable power is mainly geothermal at 9%, followed by wind at 3%, biomass at 2%, and solar and small hydro at 1% each. So for now 38% of SC Edison electricity is greenhouse-gas-free, and by 2010, when renewables are increased to 20%, 42% of SC Edison’s power will be greenhouse-gas-free.
For 1000 kWh, we have CO2 emissions from natural gas at 54% and coal of 8% giving:
540 kWh x (1170 lbs CO2 from gas/ 1000 kWh) + 80 kWh x (2080 lbs CO2 from coal/ 1000 kWh) = 632 + 166 = 798 lbs CO2 per 1000 kWh. From California Air Resources Board (CARB), however we see a greenhouse emission factor for SC Edison of 660 lbs CO2 per 1000 kWh, and our simple estimate is 20% over this. This could be because they do not include out of state coal sources, and their natural gas generating plants are more efficient than we have assumed. This disagreement is still under study.
For SDG&E for 2006, nuclear is 15%, renewables are 8%, large hydro is 10%, coal is 18%, and natural gas is 50%. The renewable power is mainly wind at 3%, biomass at 3%, and geothermal at 2%. So for now 33% of SDG&E electricity is greenhouse-gas-free, and by 2010, when renewables are increased to 20%, 45% of SDG&E’s power will be greenhouse-gas-free.
For 1000 kWh, we have CO2 emissions from natural gas at 50% and coal of 18% giving:
500 kWh x (1170 lbs CO2 from gas/ 1000 kWh) + 180 kWh x (2080 lbs CO2 from coal/ 1000 kWh) = 585 + 374 = 949 lbs CO2 per 1000 kWh.
For comparison, Los Angeles Department of Water and Power operates on 48% coal, 30% natural gas, and only 6% hydro, 10% nuclear and 6% renewables, for a present total of 22% greenhouse-gas-free. We must mention here that coal is twice as CO2 polluting as natural gas for the same energy, further downgrading their greenhouse-gas-free percentage. As above, this mix generates the comparative maximum of 1349 lbs CO2 per 1000 kWh.
The Sacramento Municipal Utility District (SMUD) takes advantage of hydro power in the North to be 47% hydro, 12% renewable, and 41% natural gas, and using no coal or nuclear (having shut down their nuclear plant by a ballot measure). So they are the State leader at 59% greenhouse-gas-free, and by 2010 at 20% renewable will be 67% greenhouse-gas-free. This mix generates 853 lbs CO2 per 1000 kWh.
Pacific Gas and Electric (PG&E) has 19% hydro, 23% nuclear, 13% renewables, 42% natural gas, and only 3% coal. So it is now 55% greenhouse-gas-free, and by 2010 will be 62% greenhouse-gas-free. This mix generates the comparative minimum of 553 lbs CO2 per 1000 kWh.
During the Period 1990 to 2004,
Total Emissions of all
greenhouse gases in
The share that is direct CO2 emissions rose from 317 to 356, for a 12% increase.
In sectors of direct CO2 sources of emissions:
Transportation rose from 161 to 188, an increase of 17%.
Total electricity production rose from 80 to 108, an increase of 35%.
Industrial stayed flat from 66 to 67.
Residential decreased slightly from 29 to 28 (this is mainly home natural gas use)
Commercial stayed flat around 12.
Land Use Change and Forestry Sink stayed flat at around -21.
Conclusions: Most CO2 production sources stayed flat despite a 20% population increase. But in the largest sources, transportation rose with population, and CO2 production from electricity production increased at double the rate of the population increase.
In terms of a per capita
interpretation of the Kyoto agreement, since population had grown by 20% over
this period, but greenhouse gas emission had only grown by 15%, California by
2004 had reduced its greenhouse gas generation per capita by 5%, almost meeting
the Kyoto goal of a 7% reduction, had the population stayed constant. For cities that have not grown, they may
already be near the