Life Cycle Water Footprints of Nonfood Biomass Fuels in China

This study presented life cycle water footprints (WFs) of biofuels from biomass in China based on the resource distribution, climate conditions, soil conditions and crop growing characteristics. Life cycle WFs including blue, green and gray water were evaluated for the selected fuel pathways. Geographical differences of water requirements were revealed to be different by locations. The results indicated that water irrigation requirements were significantly different from crop to crop, ranging from 2–293, 78–137, and 17–621 m³/ha, for sweet sorghum, cassava, and Jatropha curcas L., respectively. Four biofuel pathways were selected on this basis to analyze the life cycle WF: cassava based bioethanol in Guangxi, sweet sorghum based bioethanol in Northeast China, Jatropha curcal L. based biodiesel in Yunnan and microalgae based biodiesel in Hainan. The life cycle WFs of bioethanol from cassava and sweet sorghum were 3708, and 17 156 m³ per ton of bioethanol, respectively, whereas for biodiesel produced from Jatropha curcas L. and microalgae, they were 5787, and 31 361 m³ per ton of biodiesel, respectively. The crop growing stage was the main contributor to the whole life cycle of each pathway. Compared to blue and green water, gray water was significant due to the use of fertilizer during the growing of biomass. From the perspective of the WF, cassava based bioethanol in Guangxi and Jatropha based biodiesel in Yunnan were suitable for promotion, whereas the promotion for microalage based biodiesel in Hainan required improvement on technology.