Not a member of the sustainable design SIG, but prof. Elvin Karana at TU Delft is in the Design society and recently made an exciting announcement, taking the startup FoamLab out of stealth: https://www.foamlab.co/

They replace oil-based plastic foams with bio-based and biodegradable cellulosic foams grown by bacteria.  They don’t list LCA data or strength / stiffness data to compare its performance and impacts to existing products, but hopefully this will come soon.  In general terms, they say "Through precise control over our microbial fermentation and drying process, we can tune the density of the foam to suit different performance needs: from ultra-lightweight applications where minimal mass is critical, to denser variants for more structural or impact-resistant uses.  Our foams can have various levels of softness and compressibility. Some of our foams compress easily under touch, like a natural sponge. Others resist pressure and retain their shape, behaving more like polystyrene or dense cork.  We can grow foams that twist, fold, or wrap without tearing. On the other end, we also develop rigid foams with high dimensional stability for load-bearing, form-retaining structures, similar to wood-based foam or molded fiber… All of this tunability is achieved without synthetic binders, crosslinkers, or petrochemical inputs: just careful control of microbial growth and post-processing.”

Excited to see where this goes!