Potential to Use Sorghum Brewers Spent Grains as a Boiler Fuel

Musaida Mercy Manyuchi, Richard Frank, Charles Mbohwa, Edison Muzenda

Abstract


The potential of using sorghum brewers spent grain (BSG) was examined for the production of bioelectricity. A local brewery company, with a production capacity of 24 tons per day of sorghum brewers spent grain as biomass waste, was used as a source of boiler fuel. After a full proximate analysis, the sorghum brewers spent grain had an average calorific value of 12.6 MJ/kg whilst coal had 19.9 MJ/kg. In addition, the BSG had a fixed carbon content of 41.6%. This indicated that it was feasible to generate electricity using sorghum brewers spent grain as a source of fuel just like coal; however the moisture content of the BSG must be controlled at minimum levels to attain high calorific values. An assumed feed rate of 1100 kg/h BSG being fed, operation at 86% efficiency, maximum pressure of 9 bars, and a steam output of 1689 kg/h were designed to supply a one megawatt (MW) turbine generator. An economic analysis was done with a total investment cost of USD$ 3.4 million, a payback period of 3.7 years, and a return on investment of 27.4%. Sorghum BSG can be provided as an alternative source of bioelectricity for the brewery industry.

Keywords


Bioelectricity; Brewers spent grains; Direct combustion; Economic analyses

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