Assessing the sustainability of potential bioethanol from agave as a feedstock in Mexico
Mexico's highly oil-dependent economy, due to likely peak oil, would need alternative liquid fuels for energy security and to decarbonise the transport sector. This can be achieved by switching to alternative renewable energy carriers that can be produced in Mexico. Some progress has been made towards this goal, as the approved Bioenergy law, expected to promote ethanol industry development in Mexico.
The bioethanol industry has been developed globally from a range of feedstocks. Ethanol has long been recognized as a high-quality transportation fuel, either pure or in gasoline blends. Agave-derived ethanol is a promising candidate for further research because agave is already farmed in Mexico, as a feedstock for tequila production.
Being a plant with Crassulacean Acid Metabolism (CAM), agave species have low water requirements and high net CO2 uptake levels, due to the nocturnal CO2 fixation that minimises water loss. Agave species may be cultivated on marginal land – and hence may bypass the contentious food vs. fuel dilemma. Mexico is home to the highest number of different agave species, and also has a particular expertise in agave agricultural practices from the established tequila industry. Recent studies have shown that the species Agave tequilana Weber Blue has comparable lignocellulosic composition with other previously studied second-generation energy crops (e.g. corn stover and willow) that could be used for ethanol generation.
The purpose of the current research is to investigate the environmental performance of bioethanol from agave using the principles of life cycle analysis (LCA), with a focus on global warming potential (GWP) and fossil-energy requirements. Here, the production of ethanol from the parts of the plant not used for tequila production is considered. In order to assess sustainability of further development, a functional unit is defined as one tonne of ethanol. As no second-generation agave-derived ethanol plant is currently operating, the design of the process plant and specific process information was gathered from literature and tequila industry research, as well as current local agricultural practices inputs.
There is potential for improvements in this industry, and the intent of this work is to discuss them in order to support ethanol implementation as biofuel to be used as part of a transition towards sustainable transportation systems.