Bechtle, Miriam; Himmelreich, Birgit

Renewable feedstocks are already well-established carbon sources in the chemical industry. If these raw materials are processed in dedicated plants segregated from fossil-based production processes, the products of such plants can be claimed as bio-based. A lower economy of scale for such dedicated plants can lead to high prices for bio-based products. In addition this segregated approach is not feasible in an industry with complex integrated value chains. On the other hand, the demand for bio-based and recycled products grows constantly. A certification following the mass balance approach offers the possibility to contribute to the bio economy and to climate protection by operating existing world scale plants with fossil and bio-based/recycled feedstocks simultaneously. The resulting products contain both fossil and biobased/recycled content, which can’t be distinguished anymore. But on a conceptual level, this distinction can be made by attributing the input material to the output product according to their yield and production losses. The challenge in applying the mass balance approach for attributing bio-based/recycled raw materials to the product of a multistep chemical production processes with several input materials is how to attribute these inputs to the product and how to handle solvents and inorganic co-products. In a pilot project for two of our sites we developed a new approach to achieve a mass balance certification to deal with these challenges. Instead of assessing a global conversion factor by summing up the input and output mass streams, we introduced the consumption factor as a link between several individual raw materials and a product. Depending on which raw materials are substituted, the sustainable share of the product is different. We believe sustainable share as an indicator for the products sustainable properties helps to build up credibility and mitigates the risk of the allegation of arbitrariness commonly associated with free attribution