(Didn't think I would need to know this, but then again I didn't know what I didn't know)
A Quad is a term for a quadrillion Btu's of energy use. 1,000,000,000,000,000 British thermal units. 1 QBtu equals the annual energy output of 40 1,000MW power plants (1).
So what does that have to do with the price of bread? I'm getting to that; but for now let's take a look at the post about Energy Use In Food. As the graphic shows from the year 2000, the US food system used 10.25 quadrillion Btus of energy. That's the same amount as the annual energy output of 410,000 1,000 MW power plants.
For comparison, a modern wind turbine is capable of generating 1-2 MW of energy. The entire installed wind energy capacity of the U.S. is 11,603 MW (2).
The total U.S. energy supply is 100.278 QBtu (3).
Now if we look at the energy use graph in the other post: this means the US food system use 10% of our energy output. Some articles have said 17% on average, but I am guessing that some of that research, being from the late 70's and early 80's (4), is outdated, and that the US energy supply growth has been faster than the growth of energy use in the food system. Still, 10% is a Big Number, and if we are serious about reducing our carbon emissions then we have to include reducing the amount of energy we use to grow the food we eat.
(1): Architecture 2030 website, "U.S. Energy Consumption, Greenhouse Gas Emissions"
(2): American Wind Energy Association (viewed Mar 9, 2007)
(3): Energy Information Administration Annual Energy Overview (2005)
(4): See John Hendrickson, " Energy Use in the U.S. Food System: a summary of existing research and analysis," Center for Integrated Agricultural Systems, UW-Madison