Good mileage: 98 tons of plants per gallon

The Washington Times reports that’s how many tons of prehistoric, buried plant material it takes to produce just one gallon of gasoline.
Researcher Jeff Dukes asked, “Can you imagine loading 40 acres worth of wheat — stalks, roots and all — into the tank of your car or SUV every 20 miles?”.
Do we have to dig it up first or can we just go right in there with a scythe?