Environmental and Economic Impacts of Hydroxyapatite Mineralized Wood: LCA and LCC Analysis

Abstract

Wood is considered a promising raw material for the circular bioeconomy and has the ability to store biogenic carbon, and this is one reason why we want to extend the service life of the wood. In order to consider the influence of durability in our study, we used two wood species with different lifespans. Beech (Fagus sylvatica L.) belongs to the group of very sensitive wood species, as the durability of the untreated wood is estimated to be around 5 years; meanwhile, pine (Pinus sylvestris L.) belongs to the group of moderately resistant wood species, where the durability of the untreated wood is estimated to be up to 15 years. While toxic chemicals are often used for wood preservation, hydroxyapatite offers an environmentally friendly solution for wood mineralization. This study presents life cycle assessment (LCA) and life cycle cost (LCC) analyses comparing a novel hydroxyapatite (HAp) mineralization method with a service life of 50 years to a non-mineralized reference alternative. LCA was based on EN ISO 14040 and EN ISO 14044, while LCC was adapted from the European Commission’s LCC tool for public procurement. The results of the LCA show that mineralized wood has a lower overall impact on the environment than surface-treated beech wood but a higher impact than surface-treated pine wood. Most impact categories were determined by electricity consumption with the exception of stratospheric ozone depletion, water consumption, and land use. Water consumption proved to be the category where the mineralization process was problematic due to water consumption during the leaching process. The LCC showed that mineralized wood is the most cost-effective solution for the exterior façade, as all costs, but especially investment costs, were lower. The differences in the LCA and LCC results are mainly due to the different lifetimes of the two alternatives. It can be concluded that if energy-intensive processes and chemicals are used in the production of the material, the extended lifetime must be sufficient to account for the additional impacts that occur during the production phase.