COMPARATIVE LIFE CYCLE ASSESSMENT OF TORREFIED PELLET PRODUCTION FROM FIVE LIGNOCELLULOSIC BIOMASS TYPES

To achieve the targets for reducing greenhouse gas emissions by 2020, many European countries intend to decrease fossil fuel consumption by promoting the use of biomass energy. Due to their renewable nature and to their density and physicochemical properties, which are similar to those of coal, torrefied biomass pellets seem to be a promising substitute for this fossil fuel. This study aims to evaluate, using cradle-to-plant gate life cycle assessment, the potential environmental benefit of the production of wood torrefied pellets compared to wood pellets. It also studies the possibility of using alternative sources of lignocellulosic biomass for pellet production. Four types of biomass (fescue, sorghum, maize and bamboo) were tested and their environmental results at production and transformation stages are compared with those of wood pellets. A comparison of the production of 1 GJ of energy from the four types of lignocellulosic torrefied biomass pellets reveals that torrefaction of wood provides the best environmental performance. This is mainly due to the production of biomass process: the growth of the wood used in this study does not require the use of mineral or organic fertilisers. These inputs greatly increase the environmental impact of agricultural biomass. Finally, increasing the lower calorific content of biomass by means of torrefaction may also be linked to a reduction in the environmental impact of biomass pellet production, depending on the type of biomass and the impact category. For all the biomass types studied, performance in the global warming impact category was improved by the torrefaction of the pellets.