Optimizing the water, carbon, and land-use footprint of bioenergy production in Mexico - Six case studies and the nationwide implications

摘要

This study aims to answer the question if and how biofuels can be produced in Mexico without aggravating water scarcity, reducing greenhouse gas (GHG) emissions and avoiding indirect land-use changes. We analyzed environmental impacts of six potential maize-bioethanol production systems in Mexico on water resources, land use, and GHG emissions by using a life cycle assessment approach. Three irrigated high-input maize systems and three rain-fed low-yield systems were analyzed. Inventory data was acquired by soil sampling and interviews with farmers. For the water footprint, field water balances were modeled using the Food and Agriculture Organization (FAO) AquaCrop Model. For the carbon footprint, the BioGrace tool was used. Based on the results of status-quo analysis, scenarios with improved agricultural management were defined to identify optimization potential. Additionally, the producible amount of biofuels was estimated on a national level. The analyses showed that improving management in rain-fed agriculture offers the best opportunities for biofuel production without compromising regional water availability and without unwanted indirect effects on food prices and GHG emissions. Around 3.4% of Mexican gas consumption could be produced from maize bioethanol in Mexico without the above mentioned unwanted effects. By optimizing green water use in rain-fed maize production, around 3 billion m(3) of non-productive soil evaporation would be put into productive use. This is around 10% of the total water extracted from aquifers in Mexico. From this we conclude that unproductive soil evaporation is an underestimated water resource which should be considered in water management. (c) 2016 Society of Chemical Industry and John Wiley & Sons, Ltd