I checked out the website and graph information. If my math is correct, to compare 1,000,000 btu's of natural gas and corn, it would take 147lbs of corn to get 1,000,000 btu's. About how many bushels is that?
The other factor is the efficiency. It lists corn at 75% efficient and 85% for natural gas. New furnaces are now over 90% efficient and natural gas is running around $10.00 per 1,000,000 btu's. This will increase the amount of corn. As corn continues to rise, the economics are not as good. You also still need to factor in the payback of the cornburner too.
I agree with the piece of mind and supporting our farmers. I just wanted to compare btu's of each fuel and put it into perspective.