Sweet Sorghum

One of the first feedstocks that AKP is working to analyze is sweet sorghum.  Sweet sorghum is similar to sugar cane but has a much shorter growing cycle, thus producing more biomass per acre per year.  Compared to sugar cane, sweet sorghum requires 1/3 less water, less fertilizer, has higher fermentable sugar content and is sulfur free.  Sweet sorghum is grown throughout the world, thus there is a great experience with the production and harvesting of sweet sorghum.
“Because sweet sorghum can be used as either an energy crop or sold as forage for livestock, sweet sorghum has different markets that make it more secure for farmers to grow versus biomass crops that will only have one market option.”  Economic Feasibility of Ethanol Production from Sweet Sorghum Juice in Texas, A Thesis by Brittany Danielle Morris (December 2008), page 20. “Preliminary findings indicate that, compared to corn and grain sorghum, sweet sorghum does not produce more ethanol yield per acre, but does produce greater net energy.  This results in a net reduction in CO2 emission compared to corn or grain sorghum, and much more energy produced per energy invested.  Approximately 250% more energy is produced than invested for sweet sorghum, compared to 50% more produced than invested for corn or grain sorghum.” Nebraska Sweet Sorghum, http://doyouquittle.com/2008/04/24/Nebraska-sweet-sorghum/, Casey McConnell (4/14/2009)
Given the positive growing environment on Oahu for sweet sorghum, we propose that a required amount of acreage be planted every two weeks.  There should be 3 harvests per planting, which harvesting can be done on a daily basis.  The total growing time for the three full ratoons, based on Willacy County, Texas, should be 225 days, producing about 137 tons per acre per year.  Following the harvesting of the final ratoon, an alternate crop can be grown for the remaining 140 days to help replenish the field prior to replanting sweet sorghum.  This crop can either be used for sale (Revenue Source 1, below) or simply for plowing back into the field for nutrient replacement. When harvesting the sweet sorghum, since it is to be used only as biomass feedstock to the biorefinery, then it can be finely chopped in the field by the harvester and simultaneously loaded onto trucks, which can then take the chop to the wet storage at the biorefinery nearby.