As shown in Fig. 2, decreasing the “fresh biomass × total sugar content” reduces environmental performance in most impact categories, especially with regard to the levels of FAETP, EP, and AP; meanwhile, moderate impacts were observed on GWP and TETP. This condition also increases the demand of land per FU to produce feedstock for bioethanol. Thus, the consumption of fertilizers and BAY 60-6583 in the plant cultivation unit is increased. Moreover, increased agrochemical input leads to serious nutrient and pesticide runoff to surrounding water body and atmospheric environment, which ultimately increase EP, AP, FAETP, TETP, and GWP. Using a large amount of agrochemicals corresponds to high fossil energy consumption, which decreases NER and NEG in response to reduced “fresh biomass × total sugar content.” Implementing reasonable management practices in the plant cultivation unit to alleviate salinity stress and to increase the fresh biomass and total sugar content of sweet sorghum stem is crucial to improve energy efficiency and environmental performance.