Comparative life cycle assessment of alternative strategies for energy recovery from used cooking oil. (15th June 2018)

• Record Type: Journal Article
• Authors: Lombardi, Lidia; Mendecka, Barbara; Carnevale, Ennio
• Is Part Of: Journal of environmental management. Volume 216(2018)
• Page Start: 235
• Page End: 245
• Publication Date: 2018-06-15
• Subjects: Used cooking oil -- Cogeneration -- Biodiesel production -- Life cycle assessment -- Cumulative exergy consumption -- Global warming potential; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2017.05.016
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: The separate collection of Used Cooking Oil (UCO) is gaining popularity through several countries in Europe. An appropriate management of UCO waste stream leads to substantial benefits. In this study, we analyse two different possibilities of UCO energy reuse: the direct feed to a reciprocating internal combustion engine (ICE) for cogeneration purpose, and the processing to generate biodiesel. Concerning biodiesel production, we analyse four among conventional and innovative technologies, characterised by different type and amount of used chemicals, heat and electricity consumptions and yields. We perform a systematic evaluation of environmental benefits and drawbacks by applying life cycle assessment (LCA) analysis to compare the alternatives. For the impact assessment, two methods are selected: the Global Warming Potential (GWP) and Cumulative Exergy Consumption (CExC). Results related only to the processing phases (i.e. not including yet the avoided effects) show that the recovery of UCO in cogeneration plant has in general lower values in terms of environmental impacts than its employment in biodiesel production. When products and co-products substitution are included, the savings obtained by the substitution of conventional diesel production, in the biodiesel cases, are significantly higher than the avoided effects for electricity and heat in the cogeneration case. In particular, by using the UCO in the biodiesel production processes, the savings vary from 41.6 to 54.6 GJex per tUCO, and from 2270 to 2860 kg CO2eq per tUCO for CExC and GWP, respectively. A particular focus is put on sensitivity and uncertainty analyses. Overall, high uncertainty of final results for process impacts is observed, especially for the supercritical methanol process. Low uncertainty values are evaluated for the avoided effects. Including the uncertain character of the impacts, cogeneration scenario and NaOH catalysed process of biodiesel production result to be the most suitable solutions from the process impacts and avoided effects perspective. Highlights: Life cycle assessment (LCA) of energy recovery from used cooking oil (UCO). Cogeneration vs. biodiesel production comparison. Cogeneration requires less impactful processing processes. Biodiesel production allows higher benefits for conventional diesel substitution. Cogeneration and supercritical biodiesel production are the most uncertain processes to evaluate.