LCA of corn-based ethanol production. Influence of corn stover use to supply heat and power.

PIERAGOSTINI, C; AGUIRRE, P.; MUSSATI, M.C.

Ciudad Autónoma de Buenos Aires

Congreso; IV Congreso Argentino de la Sociedad de Toxicología y Química Ambiental SETAC Argentina; 2012

Sociedad de Toxicología y Química Ambiental SETAC Argentina y Universidad Argentina de la Empresa UADE.

Crop-based biofuels have increased sharply in recent years, especially in USA, Europe, Brazil, India, Argentina and China. In Argentina, the legislation has imposed the use of biofuels in blend with gasoline. In this context, this work aims at analyzing the environmental impact of corn-based bioethanol production in Argentina. Life Cycle Assessment (LCA) is the methodology chosen through the Eco-indicator LCIA method and SimaPro software. In most ethanol plants, natural gas is a primary fuel to produce process heat, and the electricity comes from power grids. Crop residues contain substantial amounts of plant nutrients and its retention on agricultural soils has numerous direct and indirect benefits with strong impacts on soil quality. Therefore, one case to be evaluated is the retention of all residues on a field and the use of natural gas and electricity from power grid (Alternative 1). Alternatively, corn stover can also supply heat and power to the ethanol plant (Alternative 2). In this work, these two alternatives are compared. No till and dry milling are the farming practice and biorefinery technology chosen, respectively. The defined system involves raw materials production, agricultural field operations for corn cultivation, biorefinery and the use of co-product dried distillers grains with solubles (DDGs) as animal feed. The functional unit considered is 1 kg of ethanol at the biorefinery plant, and the economic allocation between ethanol and DDGs is performed. In both alternatives, corn production is the more relevant process in most categories and the use of co-products has a positive environmental impact, particularly in land use. Several scenarios are evaluated in sensitive analysis, such as different residue/grain ratio, varying grain yield and altering the energy matrix. In general, the use of corn stover in combined heat and power (CHP) generation system to supply electricity and steam in biofuel plants has better environmental performance, but this alternative is not possible in all scenarios without decreasing the quality of soil. Therefore, implementation of the CHP system is limited to high grain yields.