Willem H. Kampen
The cane sugar industry is under pressure because of global competition to diversify into value-added products. The sucrose molecule derived from sugarcane has properties that can lead to further development. The large-scale and economic diversification of sucrose in other than food products has not been realized. The biorefinery concept can solve this problem.
Analogous to an oil refinery, a biorefinery can produce many value-added products from sugarcane, such as glycerol, bioethanol, inositol, carbon dioxide, succinic acid, aconitic acid and an animal feed ingredient. The bagasse will be the fuel to cogenerate steam and electricity, so a biorefinery would be nearly self-sufficient in energy.
A biorefinery cuts down on loss occurring in raw sugar factories (Table 1). We have demonstrated in our research that a foliar application of betaine on sugarcane increases the sugar yield. This means more sugar is available for fermentation and raw material costs are reduced.
We have also demonstrated that Louisiana blackstrap molasses can yield 42 percent glycerol and 20 percent bioethanol on fermentable sugars in a special fermentation process. Yeast cells are forced to function under extreme fermentation parameters of high osmotic pressure, pH, temperature and cell concentration. The biorefinery has considerable swing capacity in terms of glycerol versus bioethanol production. Figure 1 shows the basic process and the yields obtainable. Glycerol has numerous applications, such as toothpastes, shampoos, skin care products, polyurethane, cellophane and pharmaceuticals. Inositol is used in baby formula and specialty animal feeds for salmon and shrimp. It is a high value-added product at $5 per pound. Succinic acid is used in photographic and pharmaceutical applications. Aconitic acid is used in rubber and paints.
The demand for bioethanol should triple by the year 2010. It is a renewable oxygenate in gasoline, which can be produced economically from molasses without the need for subsidies, if incorporated into the biorefinery process.
The remaining molasses solids are concentrated and blended with agricultural waste for animal feed, the demand for which should continue to increase.
Even though the total capital requirements are high, the return on investment would be about 20 percent, which is considered good. The process can be scaled up or down, and waste treatment requirements have been minimized.
Willem H. Kampen, Associate Professor, Audubon Sugar Institute, LSU AgCenter, Baton Rouge, La.