Environmental evaluation of emerging bakery waste oil-derived sophorolipids production by performing a dynamic life cycle assessment

Sophorolipids (SLs) are promising biosurfactants that have gained significant attention due to their superior properties compared to their fossil-derived counterparts. However, the huge cost of the abstracts limits its massive production. This study investigates the viability of bakery waste oil (BWO) as an economically efficient and environmentally sustainable feedstock for SLs production. Although such waste valorisation minimizes the use of first-generation substrates, the systematic environmental impacts need to be assessed as the waste streams may introduce different materials and processes. For this reason, a dynamic life cycle assessment (dLCA) was employed to iteratively assess the environmental impacts of SLs production as technology evolved. To facilitate the comparison between each traversal, the functional unit (FU) is defined as the production of 1 kg of crude SLs. SimaPro software and Ecoinvent v3.5 database were used to perform the dLCA. Cumulative energy demand (CED), global warming potential (GWP), and ReCiPe 2016 Midpoint (H) methods were used as indicators. Surprisingly, this analysis reveals that the use of BWO as a feedstock for SLs production (15,803.3 MJ of CED and 1277.3 kg CO₂ eq. of GWP) does not consistently lead to reduced environmental impacts compared to first-generation feedstocks like oleic acid (11,898.3 MJ of CED and 959.6 kg CO₂ eq. of GWP). Then different pH regulators were added to improve the bioprocess and reduce the environmental impacts. Notably, the introduction of potassium hydroxide (KOH) as a pH regulator significantly decreased environmental footprints, with results showing a CED and GWP of 9301.1 MJ and 751.7 kg CO₂ eq., respectively. In contrast, sodium hydroxide (NaOH) exacerbated these impacts, resulting in a higher CED (19,741.6 MJ) and GWP (1595.6 kg CO₂ eq.). ReCiPe Midpoint results confirmed that the use of BWO significantly reduced the environmental impacts of chemicals, especially the first-generation feedstock, under the regulation of KOH. Finally, a comparison was made between the use of BWO and food waste as substrates, demonstrating that BWO has a greater potential for reducing environmental impact. Moreover, the study recommends that combining BWO and food waste, along with other productivity-enhancing techniques like fed-batch fermentation and in-situ separation, will further enhance the sustainability of SLs production.
The findings from the dLCA framework provide valuable insights for achieving sustainable SLs production, simultaneously enhancing SLs yield and environmental friendliness. This study highlights the effectiveness of dLCA as a method to track and analyze emerging technologies, guiding them toward a sustainability pathway. © 2024 Institution of Chemical Engineers.