Benjamin L. Legendre
The No. 1 goal of the Audubon Sugar Institute is to keep Louisiana sugar factories profitable.
Although new sugarcane varieties have contributed to the success of the agricultural sector in increasing the yield of sugar per acre, the rising costs of fuel and fertilizer along with the scarcity of a reliable labor force have squeezed sugarcane producer profits during a period when the price of sugar has reached a 20- year low. And even with improvements in factory efficiency, sugar factories face increased input costs and a scarcity of skilled labor.
In the process of squeezing juice from sugarcane at the factory, sugar can be lost in several ways. It can be left in the bagasse (the fibrous part of the sugarcane stalk), the filter cake (the “mud” that comprises the non-fibrous residue) or the molasses. The industry still has room for significant improvements in extracting sucrose from cane, reducing moisture and sucrose in bagasse, lowering sucrose in filter cake and reducing sugar in the final molasses. Reducing the moisture in bagasse is also important because bagasse is used as fuel for factory boilers. High moisture in the bagasse lowers the Btu value, which could require the use of additional fuels and further increase the cost of processing.
Researchers at the Audubon Sugar Institute are involved in exhaustive investigations in a number of areas that could ultimately improve efficiency throughout the factory. They’re investigating cane yard losses, cane preparation, milling, sugar clarification, sugar crystallization and sugar losses in final molasses.
Average sucrose content in bagasse was approximately 2.5 percent for the 2007 crop. That means a loss of approximately 15 pounds of sugar for each ton of cane processed. Every 10th of a point reduction in sucrose content in bagasse represents an extra half pound of recoverable sugar per ton of cane processed. It is therefore imperative that factory efficiencies be improved. But it is also imperative that cane and juice quality of the sugarcane being delivered to the factories be improved to overcome the increased production costs and maintain profitability.
Factories are improving cane and juice quality – and therefore the yield of recoverable sugar per ton of cane – by offering price incentives to producers who deliver cane that yields sugar above the factory average. At the same time, the factories are imposing price disincentives – lower prices per pound of sugar – to producers who deliver cane with sugar yields below the factory average. To ensure higher sugar yields, most factories encourage the use of the chemical ripener glyphosate. This can increase the yield of recoverable sugar by more than 30 pounds per ton of cane, especially early in the harvest season when the cane is mostly immature. In fact, the factories not only encourage its use but also share in the costs of the chemical and the application.
As late as the early 1970s, factories used natural gas to fuel their boilers because of its relatively low cost. In many cases the excess bagasse was sold to one of several companies that used bagasse as raw material in the manufacture of products such as paper, insulator board and planting pots. Today, however, one of the major costs in operating a sugar factory is in fuels other than bagasse to fire its boilers. The cost of natural gas or fuel oil now makes these energy sources prohibitive for use; therefore, boilers must be as efficient as possible in using bagasse as fuel.
According to data provided by Audubon faculty, the average efficiency of boilers tested during the 2005 crop year in Louisiana was approximately 55 percent in a range of 38 percent to 62 percent. Research has indicated that if the flue gas temperature could be lowered to 300 degrees from the reported temperature of about 450 degrees, boiler efficiency could be increased to 62 percent and produce 13 percent more steam with the addition of new equipment. On the other hand, with bagasse at 50 percent moisture and 3 percent ash, boiler efficiency would increase to 60 percent, thereby providing 9 percent more steam even with the existing flue gas temperature of 450 degrees.
These are also important points when considering whether ethanol production by the sugar industry can swing the energy balance in favor of sugarcane versus corn and improve the chances for sugar factory profitability.
Another way to improve Louisiana factory profitability is by cogenerating electricity and selling excess electrical power to the utility companies. However, rules and regulations of the Louisiana Public Service Commission must be changed if sugar factories are to cogenerate electricity and sell it to the power grid.
Most sugar factories around the world generate their own electrical power and often are able to sell their surplus to the power grid. Louisiana sugar factories generate only a portion of their electrical power requirements and purchase the rest. This could change if producers send the factory all the sugarcane leaves and tops as extra boiler fuel along with the stalks. Most factories, however, are not equipped to remove the excess leafy material before processing.
In Louisiana, however, it should be possible for factories to satisfy their own needs and export electrical power if they generate steam at 250 psi or higher. Depending upon the steam economy and size of the factory, it should be possible to export 5 to 10 megawatts of electrical power per day. Several factories have installed 600-psi boilers, and they should be able to effectively produce all of their electrical power needs and still export electrical power to the grid at two or three times the capacity of 250-psi boilers. However, cogenerating electricity in Louisiana sugar factories faces two drawbacks – the season is short, which makes the investment harder to justify, and electrical power would be exported during winter, a time of low demand.
Even with a good year for sugarcane growth and with excellent harvesting conditions, some producers and processors will still struggle to survive financially because of the current low price for sugar. Assuming this trend continues, the industry might be forced to look at other options, such as developing integrated technologies that will convert lowvalue sugarcane biomass (bagasse, pith, cane leaf matter, molasses) into highvalue products such as ethanol, biodiesel, pharmaceuticals, specialty chemicals and xylitol. Factories could expand their operational time by processing other crops, such as high-fiber sugarcane varieties or sweet sorghum, or they could develop a sugarcane biorefinery model with profitable byproducts to generate an economic advantage when integrated into a sugar factory.
Benjamin L. Legendre, Denver T. Loupe/American Society of Sugarcane Technologists Sugar Heritage Professor and Interim Head, Audubon Sugar Institute, LSU AgCenter, St. Gabriel, La. (This article was published in the spring 2008 issue of Louisiana Agriculture.)