Renewable feedstocks and their biogenic carbon are one of the key elements of greenhouse gas emission policies towards net zero. However, today various approaches exist to model flows and related climate change impacts of biogenic carbon and biogenic CO2, including disputed approaches and regulations which attribute reduced Global Warming Potentials for late CO2 emissions. Companies are starting to compensate their fossil-based CO2 emissions caused in manufacturing with reforestation projects. Others sell their fossil CO2 emission reductions achieved by switching to renewable materials as emission certificates to third parties. And again others claim reduced CO2 emissions of their products compared to current standard products (handprints). This LCA forum will provide a synopsis on the various approaches and facets of modelling biogenic carbon and biogenic CO2 in the building and construction sector and offers a discussion platform for resolving or better understand the positions and arguments related to contentious issues. It is supposed to foster harmonisation and, where not achievable, at least to contribute to increase transparency. A Keynote speech of Dr. Cyril Brunner, Climate Physics group, ETH Zürich, will set the floor for an informative and comprehensive 80 th LCA forum on biogenic carbon assessment and climate mitigation in the construction sector.