Abstract
A method aiming the optimization of biofuels production from integrated crop-livestock system is presented, for a farm in operation with multiple agropastoral activities. For this purpose, multi-objective optimization is applied with support of a life-cycle assessment framework. The validity test of proposed methods adopts as object of study a plausible farm in the Brazilian Midwest, with soybean and maize crop rotation along with cattle fattening in pasture and feedlots, which gives origin to various biofuels chains: biodiesel, bioethanol and biogas. Decisions are based on two life-cycle performance metrics: greenhouse gas emissions and energy balance. Impacts on biofuel life-cycles are apportioned according to the market value of co-products. Strong influence of allocation factors on performance metrics is shown. Soybean biodiesel has greater energy potential than bioethanol and biogas, while generating the lowest greenhouse gas emissions by kg of biofuel. However, high population density of animal fattening in feedlots makes this activity have a greater energy balance by footprint than agriculture, as long as previous phases of animal growth do not occur in the farm. Multi-objective optimization shows that in general the pasture share should be minimized, so the decision relies on sizing the feedlot and agricultural areas. If equal weights are applied to objective-functions, the resulting farm distribution is 88.58% agriculture, 10% pasture, and 1.42% feedlot. The present model can be used to evaluate other systems and further metrics can be applied, allowing land distribution among different agropastoral activities, helping to guide private and public decision-making in the agro-energy sector.
Published Version
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