Used-cooking-oil biodiesel: Life cycle assessment and comparison with first- and third-generation biofuel

Abstract

The environmental sustainability of second-generation biodiesel (used-cooking-oil) was examined, at industrial-scale, in Greece. The total carbon and environmental footprint per tonne of biodiesel production was ~0.55t CO 2 eq (i.e. ~14g CO 2 eq/MJ) and 58.37Pt, respectively. This is ~40% lower compared to first-generation biodiesel, an order of magnitude lower than the third-generation (microalgae), since the latter is not a fully-fledged technology yet. A threefold reduction in environmental impacts was observed compared to petrodiesel. Environmental hotspots include energy inputs to drive the process, followed by methanol (CH 3 OH) and potassium methoxide (CH 3 KO) consumption. Glycerol (C 3 H 8 O 3 ) and potassium sulfate (K 2 SO 4 ), both process co-products, resulted to avoided environmental burdens. Furthermore, used-cooking-oil valorisation for biodiesel production can address water pollution concerns from its disposal to the sewage system. The total distance and means of transport were found to influence the system's environmental sustainability. Strong incentives for used-cooking-oil recycling, widespread collection systems, and biodiesel supply chain optimization are still pending in Greece, Europe, and further afield. Given its overall low environmental footprint and capability to be produced at commercial scales, the second-generation biodiesel, which currently represents 15% of the biodiesel market in Greece, could act as a stepping-stone in decarbonizing Europe's transport sector and improving supply and energy security.

Biodiesel and green diesel generation: an overview

“…Recently, the use of ceibapentandra, pineapple, waste paper and coffee residues has been listed for the production of bioethanol. The processing of bioethanol from waste materials can also be combined with the production of biogas [27]. Biodiesel from raw Jatropha and Karanja oils can be blended with diesel for applications in engines [28].…”

More sustainable vegetable oil: balancing productivity with carbon storage opportunities

“…Whilst the use of vegetable oil for biofuel production has fallen out of favour due to sustainability concerns 16,25,26,27 , the demand for used cooking oil as a fuel source is expected to rise significantly 28 . However, despite this being seen as a highly sustainable source of transport fuel compared to first generation biofuel or fossil alternatives 29,30,31 , recent reports suggest that it could in fact be linked to deforestation and thus an additional source of currently under-considered GHG emissions 28,32 . This is partially a result of large imports of used cooking oil from regions where this is often not considered a waste-product but rather a source of animal feed 33 .…”

The advances and limitations in biodiesel production: feedstocks, oil extraction methods, production, and environmental life cycle assessment

“…The world population's growth causes an increase in the volume of food industry wastes and by-products (31). Biodiesel production from UCOs and WAFs becomes a good opportunity for their effective utilization with additional environmental, economic, and food security advantages (32). Among the main limiting factors of industrial application of oil and fat wastes are the impurity and the lack of a centralized system for collecting such row material (32).…”