Economic analysis of waste minimisation and energy recovery from spent bleaching earth

Abstract

The bleaching stage in an edible oil refining process produces large amounts of spent bleaching earth (SBE) which contains high quantities of low-quality residual oil (20–50% w/w). SBE is usually disposed of in landfill, which is expensive, not environmentally friendly, and represents an inefficient use of a potentially useful and valuable by-product. This paper investigated different methods to utilise SBE for energy generation and determined the economic viability of the most promising method to achieve this. Extracting and recovering the oil from SBE using acetone for use as a fuel and regenerating the bleaching earth was the most attractive option because it achieved waste minimisation and energy recovery. In the best operating situation (fully automated, furnace and reboiler not run continuously) this process had net earnings of $213,682 and the payback period was 4 years. Despite this method being an attractive option based on waste minimisation and energy recovery, it was also complicated and had hazardous materials involved. The volumes being processed may not be large enough to make the process economically viable for an individual oil processor. If larger amounts of SBE were being generated or a centralised dedicated facility was built to handle SBE from several facilities, then this process could become more economically viable. In the case of a centralised facility, other considerations such as charging oil processing companies to take their SBE, reselling the regenerated bleaching earth or converting the extracted oil to biodiesel could further improve the economic viability of the process. • Bleaching edible oil produces spent bleaching earth (SBE). • SBE is hazardous but could be utilized as an alternative energy source and regenerated. • This paper investigates the economic feasibility of using SBE for energy. • SBE can be used for energy, the process is not currently economically feasible.