Materials and energy flow in the life cycle of leather: a case study of Bangladesh

This article presents the results of the materials and energy flow analysis for leather produced in Bangladesh and establishes an inventory for the life cycle assessment. Also, a comparison is made with the material and energy flow of the Indian leather. A cradle to gate analysis is performed for full-chrome leather (FCL), a representative leather article from an export-oriented industry in Bangladesh, taking into consideration the main processes associated with leather production and the corresponding materials and energy input. Data was collected on annual wet-salted rawhide consumption, water, and steam consumption, chemicals requirement, tannery solid waste generation, electricity, fuel oil use for the generator and steam boiler. Moreover, an analysis of the physical and chemical properties of wastewater emissions of the different leather unit processes was performed. The input and output profiles of the FCL were compared to those of an Indian leather. It was seen that FCL consumed water 2 times higher than the Indian leather while the electricity consumption of Indian leather was almost 2 times higher than its Bangladeshi counterpart. The Indian leather had significantly higher carbon footprint (in terms of CO2 equivalent emission) mainly because of the consumption of grid electricity that comes from coal-based power generation. Wastewater parameters such as chloride, Total Dissolved Solids (TDS) and Total Solids (TS) for the Indian leather are more than 4.5, 3 and 3 times higher respectively than that of corresponding emissions for the Bangladeshi FCL, which can be attributed to the higher use of inorganic salts in the process. Despite similar input of chromium compounds for both the leathers, the emission of total chromium was slightly higher in the case of Indian leather probably due to lower uptake of chromium by the substrate. Bangladeshi FCL used twice in the amount of (NH4)(2)SO4 than India, which may be responsible for the higher BOD load in the wastewater. It can also be seen that a significant amount of rawhide input is not converted into the usable leather as demonstrated by the high proportion of solid waste generation (70% and 55% for Bangladeshi FCL and Indian leather respectively). This study highlights that wide variations exist in the materials and energy flows from different tanneries. Understanding these variations is essential to pinpoint areas where resources can be used more efficiently and optimally in the leather manufacturing process.