Techno-economic evaluation of soap production from waste cooking oil with additives derived from citrus peel waste.

In the pursuit of sustainable waste management practices, this study explores the technical and economic feasibility of soap production using waste cooking oil (WCO) combined with citrus peel waste (CPW), with a specific focus on extracting limonene as soap additives. The preliminary experimental investigations indicated that soaps produced from WCO have similar qualities if properly treated, compared to those produced from virgin oils. Also, including limonene effectively addresses WCO odours and demonstrates a promise of anti-microbial properties against E.coli . From the comprehensive techno-economic evaluation of WCO-based soap production, a focus on industrial symbiosis by integrating CPW-derived limonene is necessary. Results show that soap production with WCO and on-site additive in limonene (scenario 3) was competitive, with an IRR of 19% compared to 16% when the soap was produced using WCO and the additives were purchased (scenario 4). Also, the minimum selling prices of soaps were comparable for scenarios 3 (R 160.53/kg) and 4 (R 159.87/kg), further building on the economic viability of on-site limonene production. Hence, the environmental potential and economic viability of integrating WCO and CPW into soap production seem to be a profitable approach should on-site production be implemented.