Water footprint analysis of bioethanol energy crops in Taiwan

Abstract

Abstract Due to Taiwan's subtropical location, this study investigates the water footprint of four energy crops (corn, sweet potatoes, sugarcane and sweet sorghum), and one food crop (rice), in order to establish the water footprint data of a subtropical region. Research results indicate that sweet potatoes have the smallest water footprint, followed by sugarcane and sweet sorghum, and corn has the largest water footprint of energy crops, though the water footprint of rice is much larger, which results are consistent with the average global water footprints for these crops. The green water component accounts for more than 50% of the overall water footprint for all energy crops except of corn, indicating that the cultivation processes of these energy crops relies more on rainwater, thus, fulfilling low input selection criteria. The water footprint of rice is about 13 times larger than that of sweet potatoes and 8.8–10.4 times that of sugarcane, indicating the relative resource inefficiency of cultivating rice as a food crop. Water footprint for Taiwan-grown sugarcane, corn, and sweet potatoes compare favourably to those in the top 3 producing countries (Brazil, United States and China), as the water footprint for Taiwan-cultivated corn is only 62% of that for corn planted in the United States. A comparison of energy crop water footprints in temperate, subtropical, and tropical climate zones indicates that sugarcane cultivation is relatively more efficient in tropical and subtropical regions, due to its heavy reliance on rainwater, while corn and sweet sorghum perform better in temperate and subtropical regions.