SOURCE ENERGY AND PRIMARY ENERGY

Source energy is the energy taken from the earth, such as from a well, a mine, a forest. The energy for exploration, extraction, processing and transport is used to convert the source energy to primary energy for the US economy. The US electrical system uses about 40% of all primary energy.

- Source energy is the energy taken from coal mines, oil and gas wells, and forests for conversion to electricity and heat.

- Primary energy = source energy - energy used for exploration, extraction, processing and transport of fuels (coal, oil, gas, biofuels, wastes, etc.) to users, such as fuel to electricity generating plants, or process plants, or buildings, or vehicles, etc. That means it has not been subjected to any conversion or transformation process.

- Consumed energy by users = net electricity generation (fed to grid) + electricity imports (fed to grid)  + fuel to process plants, or buildings, or vehicles, etc.

- Gross electricity generation = primary energy (fuel to power plants) x plant efficiency.

- Net electricity generation = gross generation - plant self-use = fed to grid. 

- Electricity at user meters = fed to grid - transmission & distribution losses.

For exploration and extraction mostly diesel and electricity are used.

For processing mostly diesel, natural gas and electricity are used.

For transport mostly diesel is used.

A combination of these energies leads to a source factor of the US electrical system of about 1.08, i.e., the equivalent of about 8% of the source energy is used to obtain the primary energy fed to power plants. Excluded is the embedded energy of all the required infrastructures.

NOTE: Also there is the energy consumed for Operations & Maintenance and on-going replacements/upgrading of the infrastructures used for exploration, extraction, processing and transport of the source energy. That energy and its CO2 are counted separately.

EPA Method of Calculating Combustion CO2 of Pure Diesel and Pure Gasoline

Various government, commercial, and institutional entities calculate the combustion CO2 of various fuels, as becomes clear after Googling the internet for a few hours. As a result, a diversity of values is published year after year, which creates endless confusion among various people who use these values.

The EPA has the responsibility to annually report the CO2 emissions of the US economy.

The EPA co-ordinates its calculation standards with those of the Intergovernmental Panel on Climate Change, IPCC. If that co-ordination did not exist, each country would “invent” its own methods and confusion would be worldwide.

The IPCC guidelines for calculating emissions inventories require an oxidation factor be applied to the carbon content to account for a small portion of the fuel that is not oxidized into CO. For all oil and oil products, the oxidation factor used is set at  0.99, i.e., 99 percent of the carbon in the fuel is eventually oxidized, while 1 percent remains un-oxidized.

However, when EPA deals with the US Department of Transportation, etc., the 99% oxidation factor is not applied.

Among departments, the agreed CO2 value for gasoline is 8887 g/gal, and for diesel is 10180 g/gal. See URL

https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculato...

The Code of Federal Regulations (40 CFR 600.113) provides values for carbon content per gallon of gasoline and diesel fuel which EPA uses in calculating the fuel economy of vehicles:

Gasoline carbon content per gallon: 2421 grams

Diesel carbon content per gallon: 2778 grams

Pure diesel and pure gasoline consist of hundreds of different chemicals. As a result:

- Their densities, g/l, vary from 830 – 860 g/l for pure diesel, and 710 – 770 g/l for pure gasoline. See first URL

- I assumed 850 for pure diesel and 737 for pure gasoline.

- Both fuels have a Carbon fraction of about 0.86. See first URL

- EPA calculated the Carbon for pure diesel at 2778 g/gal, and for pure gasoline at 2421 g/gal. See second URL

- By working back, the Carbon/l and Carbon weight fraction for both fuels are obtained. 

- The combustion CO2 for pure diesel is 2778 x 44/12 = 10186 g/gal, or 22.456 lb/gal

- The combustion CO2 of pure gasoline 2421 x 44/12 = 8876 g/gal, or 19.569 lb/gal

- Both values are slightly different from the above-stated 10180 and 8887 g/gal.

https://www.iea-amf.org/content/fuel_information/diesel_gasoline

https://www.chargepoint.com/files/420f05001.pdf

NOTE: All this appears to be straight forward, but it took me an entire day of Googling among confusing and conflicting sources, before I, as an experienced Googler, had found, and re-found, the referenced URLs.

CO2 Emissions of Gasoline and E10: E10 fuel (90% gasoline/10% ethanol) has a source energy, which is reduced due to exploration, extraction, processing and transport, to become the primary energy fed to E10 vehicles. See URL.

http://www.patagoniaalliance.org/wp-content/uploads/2014/08/How-muc...

Burning E10 (90% gasoline/10% Ethanol) = 0.9 x 19.569 + 0.1 x 12.720 = 18.884 lb/gal

Upstream = 0.9 x 4.892 + 0.1 x 13.556 = 5.759 lb/gal

Total = 24.643 lb/gal, if CO2 of ethanol is counted, 24.643 - 1.272 = 23.371 lb/gal, if not counted.

Source Factor of US Electrical System: The US economy was supplied with about 25,451.00 TWh of primary energy in 2013. See Table 6. In this analysis, I used the 2013 emission data in conjunction with the 2013 electricity generation data. 

The EIA 2013 emissions data was higher than at present, mainly due to gas replacing coal. It is ironic, I could find the 2016 GERMAN electricity generation data, but not the 2016 US data.

https://en.wikipedia.org/wiki/Energy_in_the_United_States

CO2 Emission Intensity of US Electrical System: The total CO2 emissions were 2053 million metric ton in 2013, and 1821 MMt in 2016, due to less coal and more gas burning.

https://www.eia.gov/todayinenergy/detail.php?id=18511

CO2 Emissions of New England Electrical System: NE grid CO2 intensity was 726 lb/MWh, or 0.726 lb/kWh, or 726/2204.62 = 0.3293 metric ton/MWh, on a primary energy basis. This is low compared to the US and many other local grids, because of the high percentage of low-CO2 hydro, nuclear and gas on the NE grid. See Table 5.1 of URL.

ISO-NE calculates Vermont CO2 emissions at 210 lb/MWh, based on electricity supplied to utilities. The woodchip-fired McNeil and Ryegate power plants emit almost all of the CO2.

CO2 emissions allocated to Vermont = 6,100,000 MWh/y x 210 lb/MWh = 640,500 ton/y, or 581,053 Mt/y, i.e., the CO2 of the in-state generated electricity is spread out over the electricity supply to utilities. See Table 5.1 of URL.

https://www.iso-ne.com/static-assets/documents/2016/01/2014_emissio...

Table 5‐1

2014 New England System
Annual Average NOX, SO2, and CO2 Emission Rates (lb/MWh)

NOTE: Vermont has a low electrical CO2/kWh. ISO-NE estimates it at 210 lb/MWh. Burlington, a major city in Vermont, is NOT 100% renewable (as it claims), because almost all of Vermont's ELECTRICAL CO2 is from wood-fired McNeil in Burlington, and that is renewable only on a 50 - 100 year basis, provided the forest, from which the trees were taken, would still be there to do the absorbing and that the forest CO2 absorption/acre is unimpaired by development, clear-cutting, disease, etc.