Environmental sustainability of bark valorisation into biofoam and syngas
Conventional foams derived from petroleum are extensively used for insulating uses. Research into alternative sources to petroleum based chemicals is attracting a great deal of attention. Softwood bark and in special, maritime pine bark from European forests is an abundant co-product from forest industries. In this study, the production of formaldehyde-free tannin based biofoams to be used as building insulation materials was environmentally assessed using the Life Cycle Assessment methodology (cradle to-grave approach) as well as their valorisation into bioenergy (electricity and thermal energy) at end of their life cycle by means of their gasification into tar-free syngas and its further combustion in a CHP unit. The production chain was divided into four subsystems: forest activities (SS1), sawmill (SS2), biofoams production (SS3) and bioenergy production (SS4). Wherever possible, primary data from pilot plants were managed. Since two main co-products are obtained, three different approaches were considered and discussed: total allocation of environmental burdens to the electricity (main product), exergy based allocation and system expansion. According to the results, SS3 was identified as the environmental hotspot regardless the impact category considered for assessment. The large requirements of electricity in the tannin extraction unit as well as the production of chemicals required for the biofoam formulation were the responsible factors of these notable contributions. Special attention should also be paid to the uncontrolled pentane emissions associated to the biofoam formulation, specifically in terms of photochemicals oxidant formation. Remarkable environmental benefits were obtained in terms of climate change, fossil fuels depletion as well as in some toxicity related impact categories in comparison with the petroleum based foams, mainly based on the use of an abundant renewable source as raw material to produce the foams. Improvement actions should look at the reduction (or even recovery) of chemicals used, the control of diffuse emissions (e.g. pentane from evaporation unit and CHP unit) as well as the installation of a cogeneration unit to produce the electricity requirements to reduce dependence on fossil fuels.