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a b s t r a c tEconomic uncertainties and environmental constraints regarding fossil fuels have encouraged initiatives for renewable energy sources and assessment of their life cycle impacts. Brazil ranks second worldwide in biodiesel production, despite the relatively recent organization of its national chain, marked by the creation of the National Program for Biodiesel Production and Use (PNPB). The Central-West region is responsible for the largest share of biodiesel production (44.4%) and the largest cattle slaughter (37.5%). In this scenario, beef tallow has great potential for expansion of biodiesel production, since it is a byproduct of the chain that, when not properly disposed, presents a considerable environmental burden. This work presents a method for assessing environmental performance that integrates life cycle assessment (LCA) with land use change (LUC) for analysis of the tallow biodiesel production chain. The results are given in terms of increment in annual greenhouse gases (GHG) emissions per hectare related to local tallow biodiesel. The system's boundary covers a representative major cattle farming area in Central-West Brazil. For the LCA segment of the method, five inventory allocations were considered: (i) without allocation, (ii) mass, (iii) market value, (iv) energy and (v) an "average allocation", calculated as the mean of mass, market value and energy. The last one is a novel approach proposed in this work, aggregating all the others, which separately result in under or over estimation of impacts. Using the "average allocation", the increment in annual GHG emission per hectare from tallow biodiesel production, is 43.2 kg CO 2 eq ha À1 y À1 . This value is 17% less than the emission increment due to soybean biodiesel (50.2 kg CO 2 eq ha À1 y À1 ). LUC is responsible for 96% of the emission assessed, which demonstrates the importance of including LUC assessment in life cycle assessment of tallow biodiesel. According to the sensitivity analyses performed, changes from crop to pasture have superior environmental performance among the investigated options. Land use management is essential to preserve the remaining natural areas, making tallow biodiesel more sustainable.

Biodiesel has great potential to reduce greenhouse gas emissions, as an alternative to fossil diesel. However, its production occurs under different agricultural systems, with different levels of emissions in the farming phase. Integrated crop-livestock systems can play an important role in this sense, since they combine livestock with crop farming, optimizing land and input usage, with good potential to reduce total emissions from energy and food agriculture. This study compares integrated crop-livestock systems with traditional soybean farming systems regarding biodiesel production, through life-cycle assessment. Additionally, it compares different integrated crop-livestock systems in Central Brazil, to evaluate their impact regarding greenhouse gas emissions. The life cycle assessment performed adopts two approaches to apportion the farming phase emissions (sub-process division and system expansion), as well as two functional units (emissions per hectare and per kilogram of biodiesel). The system expansion approach appears to be the most suitable because the studied agropastoral systems have strong reciprocal relationship and exchange of benefits among the different farming activities. This approach also considers co-products as avoided products, showing that the whole integrated system is environmentally more attractive due to negative emissions. When analyzing only biodiesel production, results show no substantial difference between traditional and integrated systems. Therefore, the factors with the greatest impact on biodiesel production, concerning GHG emissions, are the frequency of rotation (pasture/crop) and type of management in the agricultural system.

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