Process Design, Techno-Economic, And Life-Cycle Assessments Of Selected Sugarcane-Based Biorefineries: A Case Study In The South African Context

The expansion of ethanol production using sugarcane as feedstock is of significant commercial interest in South Africa due to its primarily use as biofuel. In this chapter three integrated sugar mill–based biorefineries coproducing sugar, ethanol, chemicals, and electricity are proposed for assessment in the context of South Africa. The feedstock considered in the plants are sugarcane, green harvesting residues, bagasse, and molasses. These biorefineries were designed to be integrated into existing sugar mills in order to provide both environmental and economic profits. The scenarios considered in this chapter show coproduction of [sugar mill (SM)–lactic acid (LA) and fuel (LF) (SM-LF)] sugar, ethanol (from cellulose), and LA (from hemicellulose); [SM-furfural and fuel (FF)] sugar, ethanol (from cellulose), and furfural (from hemicellulose); [SM–only fuel (OF)] sugar, ethanol (from cellulose and hemicellulose), and surplus power for export. The simulations of these plants were carried out using Aspen Plus V8.8. Techno-economic analysis results showed that SM-LF is economically feasible, while the SM-OF and SM-FF scenarios are not profitable under the considered conditions. Thus a high-value chemical such as LA provides an important contribution to the economic viability of the ethanol production within the biorefinery concept. The life-cycle assessment of the scenarios showed potential for reduction in climate change and fossil depletion impact categories, in comparison with their conventional reference system.