I was just calculating how much land area would be necessary. Given the stats in the OP: need 18M gallons/day, 300 acres=1M gallons, this works out to 1971000 a

I was just calculating how much land area would be necessary. Given the stats in the OP: need 18M gallons/day, 300 acres=1M gallons, this works out to 1971000 acres = ~3000 sq miles = a square about 55 miles on a side.