Building materials in a circular economy: The case of wood waste as CO2-sink in bio concrete

Abstract

This paper aims to assess greenhouse gases’ (GHG) emissions in the life cycle of wood bio-concretes (WBC) production when recycled wood shavings (WS) are used as a circular economy (CE) strategy. Two WBC were evaluated, one with a higher content of WS (WBCHC) and another with a lower content (WBC-LC). Different WS recycling and transportation scenarios were evaluated. The Life Cycle Assessment (LCA) methodology was used, considering a cradle-to-gate scope, comparing two methods for calculation of GHG emissions: IPCC GWP100 and GWPbio. The transport analysis was carried out considering the WBC production in 26 Brazilian cities, according to different locations where waste WS are generated. In order to increase the robustness of the study, a sensitivity analysis was performed for: types of WS allocation, the origin of WS (waste x virgin materials), transportation efficiency, and electricity grid matrix. We verified that the waste WS content increase in WBC resulted in climate change mitigation for all cases and scenarios (when the biogenic carbon is considered). However, this benefit can vary according to WS availability and transport efficiency. Therefore, transportation must deserve special attention for the CE evaluation. When the GWPbio method is used and CO2 capture during the eucalypt growth is accounted for, the GHG emissions of WBC production can be very low (15 kgCO2-eq/m³). We conclude that recycling wood waste to use in WBC can be considered a good CO2 sink and a pathway for the low-carbon and circular construction industry.