CUDe—Carbon Utilization Degree as an Indicator for Sustainable Biomass Use

Carbon (C) is a central element in organic compounds and is an indispensable resource for life. It is also an essential production factor in bio-based economies, where biomass serves many purposes, including energy generation and material production. Biomass conversion is a common case of transformation between different carbon-containing compounds. At each transformation step, C might be lost. To optimize the C use, the C flows from raw materials to end products must be understood. The estimation of how much of the initial C in the feedstock remains in consumable products and delivers services provides an indication of the C use efficiency. We define this concept as Carbon Utilization Degree (CUDe) and apply it to two biomass uses: biogas production and hemp insulation. CUDe increases when conversion processes are optimized, i.e., residues are harnessed and/or losses are minimized. We propose CUDe as a complementary approach for policy design to assess C as an asset for bio-based production. This may lead to a paradigm shift to see C as a resource that requires sustainable exploitation. It could complement the existing methods that focus solely on the climate impact of carbon.