Life cycle assessment (LCA) and exergetic life cycle assessment (ELCA) of the production of biodiesel from used cooking oils (UCO)

The paper asses the life cycle of biodiesel from used cooking oil (UCO). Such life cycle involves 4 stages: 1) collection of UCO, 2) pre-treatment, 3) delivery and 4) transesterification of UCO. Generally, UCO is collected from restaurants, food industries and recycling centres by authorised companies. Then, UCO is pre-treated to remove solid particles and water to increase its quality. After that, it is charged in cistern trucks and delivered to the biodiesel facility to be then transesterified to biodiesel. The production of 1 metric tone of biodiesel is evaluated by a conventional life cycle assessment (LCA) to assess the environmental impact and by an Exergetic life cycle assessment (ELCA) to account the total exergy input required by the system. A detailed list of the mass and energy inputs to each stage is done using data from local companies and completed using Ecoinvent 1.2 database. The results show that the transesterification stage causes 68% of the total environmental impact. The major exergy inputs are uranium and natural gas. According to the targets set by the Spanish Renewable Energy Plan in 2010, the input from renewables to the present system would increase to 2%. As consequence, the environmental impacts and exergy input would be reduced up to 36% and 10% respectively.