How much CO2 does 1 gallon of E-85 release when burned in an engine?

Question

CO2 is carbon dioxide and E-85 ethanol

Answer 1

A touch less than gasoline.

But the important things is that it is carbon dioxide that was recently taken from the air.

Not removed a very long time ago.

So the effective increase in global warming is much less from ethanol than it is from gasoline.

Answer 2

Sorry on short answer here.

Listed below are the pounds of CO2 produced from burning one pound of ethanol and the common fossil fuels:

Ethanol 1.9; gasoline 3.1; natural gas 2.75; coal 3.7.

On first glance, it would appear that ethanol produces 39 percent less CO2 than gasoline. However, ethanol is heavier than gasoline (6.6 versus 5.6 pounds per gallon). So burning ethanol produces 12.5 pounds of CO2 (6.6 x 1.9) per gallon, which is only 28 percent less than the 17.4 pounds (5.6 x 3.1) per gallon of gasoline.

One of the biggest problems with the C02 balance of corn ethanol in the U.S. is the great quantity of CO2 liberated by using coal as an energy source in the milling and conversion of corn into ethanol.

C02 Emissions

Although the energy efficiency of corn is barely positive at present, one of the main reasons it is being promoted is its positive effect on carbon dioxide emissions to reduce global warming. Fossil fuel consumption is a major source of carbon loading to the atmosphere and the development of any fuel source which would reduce this loading would be highly desirable.

The Congressional Research Service (CRS)/ Department of Energy (DOE) Report for Congress examined the carbon dioxide loading potential of corn ethanol versus gasoline and found that corn ethanol yields 37% as much CO2 as gasoline on an energy content basis. At first this number looks very encouraging but a closer examination of the report reveals key problems with this analysis. The main problems with the CRS/DOE report are:

1) - the most optimistic value for energy used in the conversion of corn to ethanol is used, 40,000 BTU/gallon (14,110,000 J/kg), 50,000 BTU/ gallon reflects a mean value for the industry.

2) - two different energy values are used for ethanol, 84,500 BTU/gallon ethanol (29,800,000 J/ kg ethanol) and 75,700 BTU/gallon ethanol in the calculations. A commonly used value is 80,000 BTU (28,200,000 J/ kg ethanol), the burning temperature at 25 C.

3) - the carbon credit to byproducts is based on an economic basis after processing at 48.9%. The byproducts should be credited based on the energy required to grow the equivalent quantity of corn (.32 bushel of com distillers is produced from each bushel of corn processed), as corn has the same net energy value for livestock as corn distillers.

4) -The CRS/DOE report states that long term com production does result in a net continuing oxidation of soil carbon, but the flux is generally small and will not be considered further. A soil carbon loss needs to be associated with the growing of corn as it reduces soil carbon levels.

As can be seen from the tables, there is a great deal of discrepancy between the two calculations. At press time, one of the authors in the March, 1989 CRS/DOE report was contacted to see if they have reevaluated their numbers. Our value of 18.10 for kg carbon released per billion J of ethanol was within 10% of their most recent calculation but no additional soil C02 loss was calculated on their part beyond this point. However, if you do consider a soil carbon loss of .035 % organic matter per year from the growing of corn, corn ethanol produces as much CO2 as gasoline.

This is bad news because gasoline gives off 21.5 Ibs of CO2 / per U.S. gallon. Essentially you may as well burn gasoline and use the land base

For reforestation (to store carbon in soil organic matter and standing biomass) than to grow com and produce ethanol.

As the calculations show, one of the key factors affecting the outcome of the carbon balance is the loss of carbon in the form of soil organic matter from annual grain crops. If corn restored soil organic matter like perennials do, the 38.0 Ibs of CO2 could be a credit which would then cause the corn to release 62% of the CO2 released by the gasoline.

Btu content (LHV):

-Diesel fuel 128,450 per gallon

-Gasoline 116, 090 per gallon

-LPG 84,950 per gallon

-Natural gas 983 per cubic ft.

-Electricity 3,412 per kwh

-Coal 9,773 per pound

-Ethanol 76,330 per gallon

Answer 3

According to one resource I found, the only CO2 released by E-85 is the amount that was originally absorbed from the plants it is made from.

But, look at the second link for a more realistic answer.  About halfway down the page, there is a great table labeled: Emission Comparison compared to diesel fuel per Mile for a Passenger Car.  It gives a great answer to your question.