Thursday, November 20, 2008

Energy Return on Investment vs. Price

In response to the statement "As the oil price increases, the tar sands and oil shales will become commercially viable", I heard myself say firmly "It's not the price of oil that is the issue but energy return on investment" a little voice inside was saying "but......."

The Energy Return on Investment (EROI) argument goes "it's the energy you have to put in, in order to get energy out that is important". Natural gas is used to heat the oil shales, thus melting the small amount of bitumen they contain which can then be extracted. So you are effectively converting Natural Gas into oil, with a return on investment of about 5-10% in energy terms.

That argument holds good if the energy being used to produce the new source of energy has an equivalent price. (Or if one type of energy production gets tax benefits.)

A nuclear power station requires ongoing amounts of uranium (180 tonnes/pa per GigaWatt) and mining and processing uranium takes a substantial amount of energy. Depending on how much of the mining, processing, enrichment and work to decommission open cast mines is included. EROI is between 1.86 and 60. There have even been claims that nuclear has a negative EROI. Suppose you believe in the negative number but the uranium is produced in a country that also has cheap, low grade coal. This country sells the enriched uranium to another country with high electricity prices for their nuclear power plant. You can therefore have a negative EROI but a positive commercial return for both the uranium producer and the power plant operator.

So next time I answer in their, I shall instead start with the more careful "Well it's not as simple as that...".