But does it...
take into account the carbon captured by the plants grown for the food?
I see a lot of carbon being sucked up by those fields of corn planted every year for biofuel.
At least in my part of the country the farmers plow under the stalks or collect them and grind them up for composting after the corn is harvested.
Of course composting releases methane, a powerful global warming gas. Just don't try to tell that to the green police who advocate it.