Anaerobic Digestion of Leather Industry Wastes - An Alternate Source of Energy

Abstract

Advances in environmental protection legislation, along withthe awareness of societies, leads industrialists, environmentalistsand scientists, to search for production methods or industrialprocesses with lower environmental impacts. Within thisphilosophy, the maximum utilization of raw materials, wastesand by-products should be considered as a target for the leatherindustry. The anaerobic digestion of solid leather wastes mayrepresent a possibility for energy recovery through biogasproduction. This gaseous fuel (biogas) is considered a renewableand carbon-free since the basic raw material is classified asbiomass. This paper presents the potential for energy recoverythrough anaerobic digestion of different tannery wastes, tannedand untanned, based on the potential for biogas generationavailable in scientific literature using recent publications. Theresults show that collagenous materials can be efficiently degradedbiologically to obtain a gas with high calorific value in sufficientquantities to supplement the energy demand of tanneries as acomplementary source. The average heating values (HigherHeating Value, HHV) of biogas obtained under controlledconditions was found to be between 13.1 and 29.4 MJ.Nm-3allowing an estimated energy potential of around 123 to 485 kWhper metric ton of rawhide processed. Considering the tanneryenergy consumption, the biogas may represent from 0.9 to 15% ofthe total energy demand or from 6 to 31% of the electrical demand.This initiative aims to increase the energy efficiency and improvethe environmental quality of the tanning industry.