ABSTRACT
Among the current feedstock options for bioenergy applications, sugar cane in Brazil attracts special attention due to its significant contribution to mitigation of greenhouse gases (GHG) emissions through the production and use of ethanol and electricity (Macedo et al., 2008). Such environmental benefit could also be explored in other countries where sugar cane is cultivated. In this chapter, a case study of such application to the sugar industry in South Africa is presented. In South Africa, biomass is commercially used in the sugar industry and the pulp and paper mills by burning bagasse, logs and black liquor to generate process heat. The sugar industry, which has been (in most cases) self-sufficient in energy requirements could, however, generate surplus electricity for export to the grid upon modifications of its energy production configuration, but such development will be driven by a number of factors among which the electricity price and environmental regulations will be key determinants. The White Paper on Renewable Energy (2004), for instance, has set a medium-term target of 10,000 GWh renewable energy contribution to final energy consumption by 2013 (DoE, 2009) while the national Department of Energy (DoE) has developed a Biofuel Strategy focused on the production of renewable energy to reduce local dependence on imported crude oil. About 1.4 per cent of the national arable land would be utilized to achieve a market penetration of 2 per cent of liquid fuels used for road transport by 2013 (DoE, 2009). Besides providing energy security, the introduction of renewable energy sources would significantly contribute to mitigation of GHG emissions. This chapter presents an assessment of GHG emissions associated with sugar cane production in South Africa, distinguishing rain-fed from irrigated areas. Projected ethanol emissions have been estimated for hypothetical scenarios involving ethanol production either from molasses in distilleries adjacent to sugar mills or
directly from cane juice in autonomous distilleries. Possibilities to reduce ethanol life-cycle emissions were also investigated, taking into consideration the production in autonomous distilleries. Potential emissions derived from land use change due to cane expansion in Africa are also discussed. Finally, comparisons with life-cycle emissions for other biofuels are reviewed, followed by a discussion on the effects of climate change on biomass yields for different photosynthetic cycles.
