Avaliação dos impactos ambientais da produção de carvão vegetal: um estudo de caso

Abstract

Brazil is the world's leading producer of charcoal, mainly used as an energy source and reducing agent for iron ore in the pig iron and steel industry. Despite being vast, much of the Brazilian production of charcoal is low-tech and inefficient, with low use of the by-products and waste generated. Charcoal is produced through slow pyrolysis of wood, which also produces condensable gases (insoluble tar and pyroligneous extract) and non-condensable gases. Usually, carbonization gases are released directly into the atmosphere, causing health and environmental impacts, in addition to energy waste, since the non-condensable gas has about 30% of the energy contained in the wood. Therefore, seeking to reduce the potential environmental impacts, promote circular economy and improve energy efficiency of the charcoal production chain, this work presents the benefits arising from the use of wood carbonization by-products and wastes, through a Life Cycle Analysis (LCA). The environmental impacts were evaluated by comparing 4 scenarios: i) Current wood carbonization scenario; ii) Wood carbonization with non-condensable gases burning; iii) Wood carbonization with the recovering of non-condensable gases energy for electricity generation; and scenario iv) that assesses the recovering of insoluble tar and forest waste to generate additional electricity to the system, in addition to the use of Pyroligneous Extract (PE) in the cultivation of Eucalyptus. The results show that, due to carbon monoxide emissions in the carbonization furnaces, photochemical oxidation resulted in the most significant impact. It is estimated that 3.3 tons of CO2 eq./ton of charcoal are sequestered from the atmosphere throughout its life cycle, and scenarios 2, 3 and 4 can increase the amount of sequestered carbon by 5,06%, 6,7% and 0,48%, respectively. The utilization of Pyroligneous Extract for use in eucalyptus cultivation brings important environmental gains, due to its potential to reduce the consumption of formicides and herbicides.