Marine Biobased Materials: Comparative Study of Hygroscopic Behaviour and Environmental Impact in Interior Applications

Sammanfattning

Growing environmental concerns have brought a focus to the impact of building materials. In response, biobased alternatives are being explored for their potential to reduce embodied carbon, support circularity, as well as improve indoor environmental quality. This is particularly important in Scandinavia, where moisture-related issues are common, there is a growing need for locally available materials that can both regulate humidity and reduce environmental harm. Marine biobased materials, such as seagrass and seaweed, present promising yet under-researched options. These resources are especially relevant in the Scandinavian region, where abundant coastlines make marine biomass both accessible and well-suited to local building traditions. This thesis investigates the moisture-regulating and environmental properties of eelgrass panels and seaweed-based biochar lime, comparing them as alternatives to conventional materials: gypsum boards and standard lime. Hygroscopic performance was assessed through the material sorption isotherms, derived from the glass jar experiment, and additionally an indoor humidity simulation using WUFI. Environmental impact was evaluated through a comparison of environmental product declarations (EPDs) and literature on material production and circularity. Results show that the biobased materials outperform their conventional counterparts in both moisture buffering capacity and environmental impact. Eelgrass panels, in particular, demonstrated a notable reduction in indoor relative humidity fluctuations by at least 5 % compared to gypsum, while seaweed-based biochar lime exhibited improved buffering performance over conventional lime. These findings underscore the potential of marine biobased materials in addressing both environmental and indoor climate challenges in construction, warranting further investigation and practical application.