Water footprint analysis of second-generation bioethanol in Taiwan

• The water footprint (WF) of second-generation bioethanol is smaller.
• Using nonfood crops as raw materials for bioethanol can reduce water consumption.
• The operational WF is considerably larger than that of raw materials.

In this study, we calculated the water footprint (WF) of second-generation bioethanol and hypothesized that second-generation bioethanol feedstock in response to the gradual depletion of fossil fuels has contributed to exorbitant international oil prices. To resolve these problems, countries worldwide have actively engaged in developing alternative energy plans to reduce their dependence on petroleum. Bioethanol is a critical choose items of biofuels, and increased use of biofuels for transportation is expected to substantially raise the level of competition for freshwater resources. In this paper, Taiwan's second-generation bioethanol demonstration plant is used as an example to calculate the WF of second-generation bioethanol. Using bagasse and rice straw as raw materials, the water footprint are 268.8 L H2O/L EtOH and 4674.9 L H2O/L EtOH, respectively, which is considerably lower than that of first-generation bioethanol. In this study, we proposed two sources of feedstock that are suitable for future second-generation bioethanol: (1) nonfood crop materials; and (2) domestic waste (e.g., food waste). The results of this study can be used by countries interested in using biofuels to formulate and implement energy policies that will enable them to develop renewable energy sources and simultaneously consider the management and application of water resources.