Environmental assessment of microalgae biodiesel production in Colombia: Comparison of three oil extraction systems

Abstract

The objective of the study was to compare three cases of biodiesel production from microalgae dried biomass applying the Life Cycle Assessment (LCA) technique by means of the "cradle to grave" concept, presenting preliminary results for environmental assessment of emerging technologies for microalgae biodiesel production in Colombia focused on oil extraction stage. The evaluated processes correspond to the following cases: case 1 hexane-based extraction (HE), case 2 methanol/chloroform (MCE) and case 3 ethanol/ hexane (EHE). Operating conditions for each extraction method were adjusted with experimental work. Routes were simulated using the Aspen Plus® 7.1 software, taking as a feedstock a robust modeled composition of Chlorella sp. Environmental emissions associated with algae biodiesel production were quantified and evaluated through the Simapro 7.1 software. The outcomes confirm the potential of microalgae as a sink of greenhouses gases, but highlight the crucial necessity of decreasing energy consumption and some technical improvements in oil extraction step. Results related with greenhouse gas (GHG) emissions were compared with European sustainability criteria, in order to identify the reduction of the hypothetical microalgae biodiesel. Case 1 presents the most important reduction respect to fossil reference (156%). For the other two scenarios, reduction decreases because of higher energy consumption. Case 2 presents a reduction of approximately 99% and case 3 presents a reduction reaching 14%.