Carla Caldeira
University of Coimbra
Carla Caldeira holds a PhD in Sustainable Energy Systems (MIT-Portugal Program, University of Coimbra, 2017), an MSc on Environmental Science and Technology (University of Lisbon, 2009) and a Degree in Technological Chemistry (University of Lisbon 2001). She is currently a postdoctoral researcher at ADAI-LAETA working on the development of Life-Cycle Sustainability Assessment of bioenergy systems. In the past she worked as a researcher in Heterogeneous Catalysis at Instituto Superior Técnico / University Pierre et Marie Curie (2001-2002), Senior Technical Specialist - Chemical Analyst at INCM (2002-2012) and researcher at SIM - CCIAM, Climate Change Impact, Adaptation & Mitigation at Faculty of Sciences University of Lisbon (2010-2012). She was also a visiting researcher at MIT for a year. Her research interests include Life Cycle Assessment, Water footprint, Uncertainty in LCA, Multi-Objective Optimization, Blending Models, Bioenergy Systems, Life Cycle Sustainability Assessment.
The controversy raised around biofuels sustainability increased the pressure on biodiesel producers to be as cost efficient as possible and, simultaneously, ensure the sustainability of the biodiesel. As about 85% of biodiesel production costs are attributed to feedstock cost and each feedstock has a different environmental profile, operational level decision making about feedstock selection is crucial to reduce production costs and manage biodiesel environmental performance.
This work explores opportunities to improve biodiesel cost effectiveness at the operational level, particularly in the feedstock selection process, by assessing the use of waste-based feedstocks(Waste Cooking Oil, WCO) in blends with conventional feedstocks (palm, rapeseed and soya) and hedging feedstock purchase, whilst managing environmental impacts. For this purpose, an uncertainty-aware decision aiding tool to assess economic and environmental tradeoffs of decisions at the operational level, addressing feedstock compositional and price uncertainty, was developed. The model combines environmental life-cycle assessment (LCA) with blending models using multi-objective optimization to assess water scarcity (WSI), water degradability – acidification (AA),eutrophication (EU), ecotoxicity (FT) and human toxicity (HT) – and Greenhouse Gas (GHG) emissions (CC). Data from different crop cultivation locations were considered: Colombia and Malaysia for palm; Argentina, Brazil and the United States (US) for soybean; and, Germany, France, Spain, Canada and the US for rapeseed. An approach was developed to facilitate the decision process that enables the decision-maker to select the best compromise feedstock blend based on an explicit overall environmental performance.
Results show that incorporating feedstocks’ compositional uncertainty allows the use of WCO in blends with conventional feedstocks without compromising biodiesel technical performance. A reduction of total feedstock cost was obtained for blends with WCO relatively to equivalent (similar technical performance) blends composed only of virgin oils. The percentage of cost reduction depends on the relation among the prices of the feedstocks.
The multi-objective analysis showedthat lower CC and WSI solutions (blends) can be obtained at a lower cost if WCOis included in the biodiesel blend. The same conclusion is obtained when moreenvironmental objectives (AA, EU, FT and HT) are considered in the analysis.The decision-aiding approach developed allows for the visualization of the tradeoffbetween cost and environmental impacts, facilitating the decision process whenmore than three objectives are at stake.
This research shows that the inclusion of WCO in a diversified portfolio of feedstocks used in blending optimization models is an attractive approach to improve biodiesel cost effectiveness and environmental performance. The model developed can be further used to optimize the blending of alternative feedstocks and to assess the technical viability of other waste-based feedstock (e.g. animal fat) or emerging feedstocks such as algae. Although the tool was designed specifically for biodiesel production system, it can be adapted to other industries, particularly in the recycling sector, to support production planning at the operational level to enhance technical, economic and environmental performance of these industries.
• Sustainable energy systems , • Decision support methods and tools
