Carbon footprint of crust leather produced in Bangladesh

Abstract

The increased awareness of the importance of environmental protection and assessment of the GHGS emission, and the possible impacts associated with products both manufactured and consumed, has led to the development of life cycle assessment (LCA) methods to better understand and address impacts which assists in identifying opportunities to improve the environmental performance of products at various points in their life cycle. A representative leather tannery industry in Bangladesh has been studied from an environmental point of view. Life Cycle Analysis (LCA) methodology from cradle to gate has been used for the quantification and evaluation of the impacts of two representative leather articles namely fullchrome and chrome retanned crust leather production systems as a basis to analyze, compare and propose further improvement actions. The functional unit chosen is 1 square meter crust leather. The effects of the resource use and emissions generated are grouped and quantified into a limited number of midpoint impact categories (human toxicity, respiratory inorganics, respiratory organics, ionizing radiation, ozone layer depletion, aquatic ecotoxicity, terrestrial ecotoxicity, aquatic acidification, aquatic eutrophication, terrestrial acidification/nitrification, land occupation, global warming, nonrenewable energy consumption, mineral extraction) and these are finally grouped into four endpoint damage categories (human health, ecosystem quality, climate change, and resources). To characterize and assess the effects of the environmental burdens identified in the inventory, impact assessment was conducted based on impact 2002+methodology. In doing so, life cycle inventory data were linked to the midpoint categories. In few cases, like electricity, transportation, packaging energy from generator and diesel combusted in boiler processes have been taken as proxy processes. The obvious advantage of using proxies is that they facilitate the impact estimation when a full assessment would be too costly. The use of proxy data sets is the quickest and easiest solution for bridging data gaps. The results indicate that significant environmental impacts were caused during the tanning as well as the transportation for raw material, imported chemicals and delivery of crust leather; electricity production and packaging materials required in the life cycle. Damages to human health, ecosystem quality are mainly produced by the chrome tanning, acid wash, Rechroming and neutralization processes. Transport and electricity also contributed moderately. The control and reduction of chromium and ammonia emissions are the critical points to be considered to improve the environmental performance of the process. Technologies available for improved management of chromium tanning were proposed. The carbon footprint of the two systems found to be 0.721 and 0.731 Kg CO2 eq per m2 of full-chrome and chrome retanned crust leather respectively. Environmental hotspots found for production processes were tanning, rechroming, neutralization, deliming-bating and acidwash. Supply chain hotspots are transport for raw hides and chemicals, electricity. Slaughtering, the cradle considered for carbon footprint analysis of leather contributed minor amount to the impact categories. Production processes mainly contributed to non-carcinogens, aquatic ecotoxicity, aquatic acidification and aquatic eutrophication midpoint categories which finally contributed much to damage categories human health and ecosystem quality. Supply chain processes mainly contributed to midpoint categories global warming, carcinogens, ionizing radiation, ozone layer depletion, terrestrial ecotoxicity, terrestrial acidification/nutrification, respiratory organics, respiratory inorganics, land occupation, mineral extraction and non-renewable energy which finally contributed much to damage categories climate change, resources and human health. Full-chrome crust leather has 5 times higher impact on aquatic ecotoxicity, 4.53 times higher on non-carcinogens and 2.53 times higher on ecosystem quality. In addition, aquatic acidification of full-chrome system is greater than chrome retanned system but chrome retanned crust leather has marginally higher value of aquatic eutrophication. Comparing all impact categories, full-chrome crust leather had higher environmental burden than chrome retanned crust leather.