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Sustainable fuels and technologies are expected to significantly contribute towards climate change mitigation considering that the transportation sector provides a 23% share out of the total CO 2 emissions. Biodiesel is a green fuel produced by transesterification of triglycerides with an alcohol in the presence of a catalyst. The current study entails modelling and simulation of biodiesel production, through an acid transesterification process, using both classic and intensified methods, coupled with an environmental impact analysis performed following the Life Cycle Assessment methodology. The traditional biodiesel production consists in the synthesis and separation sections, while the intensified method is based on reactive distillation. ChemCAD software was used to simulate and evaluate the processes from a technical point of view. Methanol is generated using CO 2 and H 2 , this method being considered as a new approach for CO 2 utilization. Water electrolysis is employed for H 2 generation, with either biomass or natural gas as power source. A cradle-to-gate environmental analysis is performed within the current research by means of GaBi software, considering the following system boundaries: i) upstream processes: catalyst supply chain, sunflower oil supply chain, natural gas supply chain, limestone extraction and decomposition, ii) main-processes: methanol and biodiesel production, iii) downstream processes: disposal of wastes. ReCiPe method was chosen as the impact assessment method. High purities for the main product and by-product are obtained (i.e., purities higher than 99%). The outcome of the process simulation points to the conclusion that the intensified path gives better performances from technical point of view. The environmental results show that the classic approach performs better when CO 2 and H 2 are used as raw materials, while reactive distillation displays a higher efficiency when natural gas is used as feedstock. [Display omitted] [ABSTRACT FROM AUTHOR]

• Bioenergy-livestock integrated systems can alleviate pressure on land resources. • BLI has potential to meet global future biofuel demands and climate mitigation targets. • Production of feed using bioenergy by-products is techno-economically feasible. • Biofuels from integrated systems can reduce GHG emissions compared to fossil fuels. • There is still room to further explore the integration of bioenergy-livestock value chains. Bioenergy is seen as a key option to meet future energy demands and mitigate climate impacts. However, large-scale deployment of bioenergy can cause an additional pressure over land resources and correspondent sustainability impacts. Enhanced land management practices are fundamental to intensify land-based outputs under different climate mitigation scenarios. Bioenergy-livestock integration (BLI) is a win-win strategy to climate mitigation while ensuring food and fibers demands from the society by using bioenergy by-products as animal feed to release land to additional industrial crops production. This study comparatively assesses BLI opportunities in Brazil to better understand the sustainability issues of the alternatives for integration of these value chains, highlighting the key techno-economic and environmental aspects. When compared to conventional systems, the BLI systems present positive techno-economic impacts and lower greenhouse gas emissions, reaching mitigations up to 32 % and 22 % for meat and ethanol production, respectively. The expansion of BLI systems in Brazil could meet projected biofuels future demands, using less than 20 % of the expected area for this expansion. Potential expansion areas are concentrated in Center-South region of Brazil. BLI systems can be further advanced by including other synergies, such as codigestion of sugarcane vinasse and cattle manure, integration of flex ethanol plants with biodiesel plants, maximization of biofuels by-products as animal feed, and inclusion of novel promising alternative industrial crops such as macauba, sweet sorghum, energy cane and short rotation eucalyptus coppice. However, we identify many potential barriers including the operational complexity, specific know-how, and necessity of economic incentives. This study may provide important insights for strategic and integrated polices for both agricultural and livestock sections as the proper sustainability assessment of an early stage of the deployment of enhanced BLI systems may help to meet global future demands of energy while also contributing to climate change targets. [ABSTRACT FROM AUTHOR]