Deashing of Sweet Sorghum and Energy Cane Syrups

Sweet sorghum and energy cane are promising biomass feedstocks for future biorefineries for the southeastern US. The ability to incorporate these row crops in the harvesting and processing cycle of the existing sugar cane industry gives them an edge over other feedstocks for this region. The main product of theses energy crops is combustible biomass; however, preparation and drying operations (milling) yield sugar syrups as byproducts, which may be utilized for fermentation and thermal conversion to bio-based chemicals.

The quality benchmarks for any sugar syrup are on the low quality (low revenue) side blackstrap molasses and corn derived glucose syrup on the high quality side. Syrups produced from sweet sorghum and energy cane exhibit high ash levels (up to 12%) and high color, clearly inferior to corn syrup, but better in purity than blackstrap molasses. Potassium chloride comprises the majority of the ash-component of the syrup and has to be reduced to glucose syrup levels (0.05%/Bx) before being able to compete. Due to potassium chlorides’ high solubility advanced separation methods are a necessity. The combination of microfiltration, electrodialysis and ion exchange was used to demonstrate the scalable production of syrups which can meet the specifications of industrial partners and will allow these energy crops to compete with corn derived products.