Valorization of tannery limed fleshings through fat extraction: an approach to utilize by-product

The present work is intended to develop a fat extraction method from the limed fleshings for soap production. In leather processing, just after washing, following the liming process, swollen pelts (lime treated hide/skin) have to pass through an operation to remove the remaining fat and flesh from the flesh side in order to improve the diffusion of chemicals into pelt is known as fleshing. Fleshing is the indispensable mechanical operations in leather processing where substantial amounts of inevitable solid waste (termed as fleshings) are produced. Generally, fleshings are kept indiscriminately nearly the industrial area as green, which has negative effects on the environment including human health. It contains a considerable amount of fat, which could be a great source for soap production. To extract fat, firstly collected cowhide fleshings were delimed with boric acid and hydrochloric acid for 5–6 h. The delimed fleshings were heated in a water bath to separate fat from its structure. The optimized extraction conditions were: temperature 75 °C; time 3 h; without agitation. It was estimated that 6.2 % (dry weight) fat was extractable and yearly 638.6 MT fat could be extracted only from the cowhide fleshings in Bangladesh. Finally, soap was prepared from the extracted fat by saponification using sodium hydroxide. The soap was soluble in distilled water, which has good lathering and cleansing power. The process could be optimized for large-scale production, which would be allowed to produce a new product for the commercial use. The approach could also contribute a significant reduction in the environmental impact of inevitable solid waste and decrease the costs associated with disposal.