The aim of the study is to describe the recycling of used cooking oil (UCO), a domestic waste generated daily in restaurants and food companies, for the production of biodiesel in Catalonia. Such recycling scheme includes four stages: 1) collection, 2) pre-treatment, 3) delivery of UCO and 4) production of biodiesel. Data are first gathered in companies working in the real system and then on statistical reports and databases for accounting in detail the inputs and outputs to the system. Then, the methodology Life Cycle Assessment (LCA) is used to account the potential production of biodiesel and the environmental impacts related to such production. The results show that impact categories are highly influenced by the input from the electricity supplied to the preesterification and the transesterification stages. The environmental impact of the system is reduced in all the impact categories, especially in the global warming potential (GWP) when it is also accounted the input of materials required to upgrade the by-products glycerol, fertiliser and methanol.