Life cycle assessment of charcoal production and electricity generation from eucalyptus in an industrial batch kiln

Abstract

Brazilian charcoal is produced from planted eucalyptus forest wood in traditional batch reactors. The ordinary technology applied in Brazil does not use pyrolysis waste gases, which leads to the loss of 30% of wood energy and decreases air quality. This study evaluated the synchronous use of industrial batch kilns, waste gas burning, and energy recovery to produce electricity. Three scenarios were analyzed: (S1) Eucalyptus charcoal production without gas burning (Base Scenario); (S2) with gas burning; and (S3) with gas burning and electricity generation. Since a eucalyptus forest can fix carbon into its biomass through photosynthesis and finally into charcoal, S1 was able to reduce 3402.5 kg of CO2-eq per Mg of charcoal produced, and S2 reduced 6453.1 kg of CO2-eq due to waste gas methane burning. Electricity production is environmentally positive for all evaluated environmental indicators thanks to gas pollutants destruction and renewable energy generation. For S1, a ratio difference of 6.3 was found between the output of renewable energy and fossil energy input during the charcoal life cycle. For a combined production of charcoal and electricity (S3), a ratio difference of 6.9 was found. Photochemical oxidation was the main impact which can be significantly reduced by adopting gas flaring.