Residue from Sugarcane Juice Filtration (Filter Cake): Energy Use at the Sugar Factory

Sugar from sugarcane represents 65-70% of the world production of sugar and its production is mainly located in developing countries. The production process requires high amounts of steam and electricity at the different stages, and generates important quantities of residues. A major residue of the sugar production is filter cake (in Cuba: Cachaza), the residue from cane juice filtration. Filter cake causes significant pollution, and in several sugar factories it is considered a waste, posing problems of management and final disposal. This paper reviews recycling and recovery opportunities of filter cake (and bagasse) and experimentally studies the use of filter cake as fuel at the sugar factory. Filter cake may e. g. be used as a fertilizer/soil improver directly applied on the fields or after composting. During its decomposition, it generates, however, an acid leachate and emits significant amounts of greenhouse gases. Moreover, the experimental part of the paper shows that blends of filter cake with bagasse can be combusted in industrial boilers in sugar factories, and that loose, non-vitrified ashes with a similar appearance as bagasse ash are obtained. This results in lower volumes and masses of residues to be transported, so that transportation costs are reduced. Moreover, it gives a new economic value to the filter cake, and reduces its environmental impact. When all filter cake would be combusted blended with bagasse, about 25% more ash would be obtained than for bagasse and the trace element composition would comply with the regulatory limits for use as fertilizer/soil improver.