Sugarcane is burned before harvesting to remove the unproductive leafy material that makes up 20 to 25 percent of the cane plant. The leaves contain very little sugar, but if not removed before processing the cane, they can reduce the amount of sucrose (sugar) that can be recovered from the cane stalk at the factory.
http://hcsugar.com/what-we-do/faqs/
While economically justifiable, it still doesn’t minimize the emissions by BACT/MACT standards used on the mainland.
Maybe the Hawaii watermelons need to use the “unproductive leafy material” as their alternate source of energy?