Management Strategies for Oil and Grease Residues

Abstract

The fate of organic oil and fat (i.e. "grease", defined as plant oils/animal fats) from restaurants and other commercial kitchens, is probably one of the most forgotten, yet critical issues in waste management, especially in developing countries. Even in cosmopolitan areas like Bangkok (Thailand), oil and grease are either released into the sewer lines, or are collected manually after separation in grease traps and open dumped with solid waste. An investigation was made to assess the quantity and characteristics of oil and grease released from commercial kitchens in Bangkok. Based on the results obtained, a holistic management strategy for these residues was developed. The recommendations for oil and grease management were laid down into three options, depending upon the size of the catering establishment, which affects the collection system, and the treatment, re-use and disposal alternatives. The major steps involved in the management scheme are separation and concentration of grease residues in central receiving treatment containers (CRTCs) at a central wastewater treatment plant (CWTP), anaerobic treatment for by-product recovery, and re-use in industrial applications. For the final disposal of concentrated oil and grease residues and the remaining sludge from anaerobic treatment, priority is given to incineration, together with sewage sludge or solid waste. It is shown that the treatment and disposal of these residues can be integrated into sewage sludge disposal schemes including incineration and anaerobic digestion. Landfill disposal was identified as an intermediate solution, preferably after stabilization. © 1997 ISWA