This aim of this study was to use Data Envelopment Analysis (DEA) to assess the life cycle energy efficiency of six biofuels in China. DEA can differentiate efficient and non-efficient scenarios, and it can identify wasteful energy losses in biofuel production. More specifically, the study has examined the efficiency of six approaches for bioethanol production involving a sample of wheat, corn, cassava, and sweet potatoes as feedstocks and “old,” “new,” “wet,” and “dry” processes. For each of these six bioethanol production pathways, the users can determine energy inputs such as the embodied energy for seed, machinery, fertilizer, diesel, chemicals and primary energy utilized for manufacturing, and outputs such as the energy content of the bioethanol and byproducts. The results indicate that DEA is a novel and feasible method for finding efficient bioethanol production scenarios and suggest that sweet potatoes may be the most energy-efficient form of ethanol production for China.