Hydrocarbon fuel blendstock from tannery waste: energy from fleshing oil via gas phase catalytic cracking

The global leather industry generates large quantities of tannery waste. These leather wastes have a high fat content, which could be used for valuable products. This study focuses on the conversion of such fats into a biocrude to be distilled into a bio-based hydrocarbon fuel blendstock. A biorefining technology defined as ‘gas-phase catalytic cracking’ (GCC) over activated carbons, also referred to as ‘greasoline’, was used for conversion, and GC–MS/FID and simulated distillation for product characterization. The experiments were performed at ambient pressure and 450 °C reaction temperature, with 40 g h-1 of fat being processed over 55 g of steam-activated carbon under a nitrogen atmosphere for a duration of 4 h. Fleshing oil obtained from the pre-fleshing of double-face lambskins by extraction with supercritical CO2 yielded almost the same mass fraction of organic liquid product (OLP) (59 wt%) as palm oil used as a reference (62 wt%). In both OLPs, n-alkanes from heptane to heptadecane predominate, with a clear predominance of n-pentadecane and n-heptadecane and no unsaturated molecules among the major components. For both oils, about 85 wt% of the OLP is in the boiling range of diesel fuel, and about another 12 wt% is in the gasoline boiling range. The results show that mixtures of fatty acids extracted from leather tanning wastes can be used for value-added products - in particular for the production of bio-based hydrocarbon fuel blendstock.