Effect of biogas utilization and plant co-location on life-cycle greenhouse gas emissions of cassava ethanol production

Five types of plants that produce ethanol from cassava in Thailand were examined to identify the best option with respect to greenhouse gas (GHG) emissions reduction. We specified the five plant types for evaluating the impacts of biogas utilization and the co-location of ethanol production at existing cassava starch factories and assessed the life-cycle GHG emissions of these plant types. The results showed that the amount of GHG emission reduction in cassava ethanol production depended on the plant type. Substantial GHG savings are achieved by ethanol plants that use biogas produced during wastewater treatment as fuel. Using biogas for steam generation is more effective in reducing GHG emissions than using it for electricity generation. Plants co-located with starch factories have advantages in relation to GHG emissions when compared with stand-alone plants. However, the impact of co-location is limited because cassava starch factories are not energetically self-sufficient. Improvement analysis suggested that boiler efficiency and the energy source for steam generation are key factors for reducing GHG emissions. (C) 2012 Elsevier Ltd. All rights reserved.