As bio-ethanol is developing rapidly, its impacts on food security, water security and the environment begin to receive worldwide attention, especially within the Water–Energy–Food nexus framework. The aim of this study is to present an integrated method of assessing sweet sorghum-based ethanol potential in China in compliance with the Water–Energy–Food nexus principles. Life cycle assessment is coupled with the DSSAT (the Decision Support System for Agrotechnology Transfer) model and geographic information technology to evaluate the spatial distribution of water consumption, net energy gain and Greenhouse Gas emission reduction potentials of developing sweet sorghum-based ethanol on marginal lands instead of cultivated land in China. Marginal lands with high water stress are excluded from the results considering their unsuitability of developing sweet sorghum-based ethanol due to possible energy–water conflicts. The results show that the water consumption, net energy gain and Greenhouse Gas emission reduction of developing sweet sorghum-based ethanol in China are evaluated as 348.95 billion m3, 182.62 billion MJ, and 2.47 million t carbon per year, respectively. Some regions such as Yunnan Province in south China should be given priority for sweet sorghum-based ethanol development, while Jilin Province and Heilongjiang Province need further studies and assessment.

Water, energy, and food are the most basic and essential sectors for human welfare. However, an inextricable nexus and competition exists among these sectors. Production of molasses-based bioethanol is an interesting case resulting in the production of different food and energy materials while consuming water, energy, land, and other raw materials, throughout its life cycle. This paper briefly describes the nexus among water, energy, and food for bioethanol in Pakistan and its environmental implications. A life cycle approach has been used for evaluating four footprint categories including the carbon, ecological, water scarcity, and energy footprints along with an energy analysis of bioethanol. In comparison to conventional gasoline, bioethanol would have benefits in terms of lesser greenhouse gas emissions, better use of productive land, and superior energy performance, but, this will be at the expense of higher impacts in terms of water scarcity. Therefore, considering only a single aspect could result in inadvertent trade-offs that may go unnoticed. The quantified values would help accomplish integrated resource management along with their utilization within limits so as to be available for other uses. This study could help in developing strategies for optimal management of resources to maximize the synergies and minimize the possible trade-offs.

This study presents a comprehensive decision model for the integrative design of a biorefinery for bioethanol production and its supply chain (BPSC) under the water-energy-food-land (WEFL) nexus framework. A new optimization model was developed using a mixed integer linear programming to simultaneously identify the optimal process configuration of a bioethanol production plant and the optimal bioethanol supply network. The objective function of the model is to minimize the total annual cost for establishing and operating the BPSC to meet society’s needs (energy, water and food) under the limited resources and land availabilities, and technology capacity. The proposed model can provide the optimal solutions for design and operation of the BPSC: i) the types, and quantities of feedstocks; ii) types, number, and location of facilities and; iii) regional flows. The capability of the proposed model was validated through the case study of Jeju Island, Korea, with two scenarios: BPSC by cost (COPT) and nexus (NOPT) optimization. As a result, it was identified that the BPSC in NOPT requires higher energy supply cost (8.55 B$) than the COPT (6.44 B$). However, the BPSC in NOPT can satisfy the society demands with relatively smaller consumption of occupied land (2%), fresh water (30%) and primary energy consumption (64%) than that of the COPT, respectively.

Bioethanol has been researched as a potential alternative to substitute liquid fossil fuels due to its eco-friendly characteristics and relatively low production cost when compared to other bio-based fuels. First generation bioethanol is produced from raw materials rich in simple sugars or starch, such as sugarcane and corn, which are food sources. To avoid the fuel versus food dilemma, second generation bioethanol aims at using non-edible raw materials, as lignocellulosic agricultural residues, as source of fermentable sugars. Hydrolysis with sub/supercritical water has demonstrated great potential to decompose the lignocellulosic complex into simple sugars with several advantages over conventional processes. This review provides an overview of the state of the art on hydrolysis with sub- and supercritical water in the context of the reuse of agricultural residues to produce suitable fermentation substrates for the production of second generation bioethanol. Recent applications and advances are put into context together, providing an insight into future research trends.